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Network Working Group M. Smith, Editor
INTERNET-DRAFT Netscape Communications Corp.
Intended Category: Standards Track T. Howes
Obsoletes: RFC 1823 Netscape Communications Corp.
Expires: 2 December 1999 A. Herron
Microsoft Corp.
M. Wahl
Innosoft International, Inc.
A. Anantha
Microsoft Corp.
2 June 1999
The C LDAP Application Program Interface
<draft-ietf-ldapext-ldap-c-api-03.txt>
1. Status of this Memo
This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026. Internet-Drafts are working docu-
ments of the Internet Engineering Task Force (IETF), its areas, and its
working groups. Note that other groups may also distribute working
documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference material
or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This draft document will be submitted to the RFC Editor as a Standards
Track document. Distribution of this memo is unlimited. Technical dis-
cussion of this document will take place on the IETF LDAP Extension
Working Group mailing list <ietf-ldapext@netscape.com>. Please send
editorial comments directly to the authors.
Copyright (C) The Internet Society (1997-1999). All Rights Reserved.
Please see the Copyright section near the end of this document for more
information.
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2. Introduction
This document defines a C language application program interface (API)
to the Lightweight Directory Access Protocol (LDAP). This document
replaces the previous definition of this API, defined in RFC 1823,
updating it to include support for features found in version 3 of the
LDAP protocol. New extended operation functions were added to support
LDAPv3 features such as controls. In addition, other LDAP API changes
were made to support information hiding and thread safety.
The C LDAP API is designed to be powerful, yet simple to use. It defines
compatible synchronous and asynchronous interfaces to LDAP to suit a
wide variety of applications. This document gives a brief overview of
the LDAP model, then an overview of how the API is used by an applica-
tion program to obtain LDAP information. The API calls are described in
detail, followed by appendices that provide example code demonstrating
use of the API, the namespace consumed by the API, a summary of require-
ments for API extensions, known incompatibilities with RFC 1823, and a
list of changes made since the last revision of this document.
3. Table of Contents
1. Status of this Memo............................................1
2. Introduction...................................................2
3. Table of Contents..............................................2
4. Overview of the LDAP Model.....................................4
5. Overview of LDAP API Use.......................................4
6. Header File Requirements.......................................6
7. Common Data Structures.........................................7
8. Retrieving Information About the API Implementation............8
8.1. Retrieving Information at Compile Time......................9
8.2. Retrieving Information During Execution.....................10
9. LDAP Error Codes...............................................13
10. Performing LDAP Operations.....................................14
10.1. Initializing an LDAP Session................................14
10.2. LDAP Session Handle Options.................................15
10.3. Working With Controls.......................................20
10.3.1. A Client Control That Governs Referral Processing........22
10.4. Authenticating to the directory.............................22
10.5. Closing the session.........................................25
10.6. Searching...................................................26
10.7. Reading an Entry............................................29
10.8. Listing the Children of an Entry............................30
10.9. Comparing a Value Against an Entry..........................30
10.10. Modifying an entry..........................................32
10.11. Modifying the Name of an Entry..............................34
10.12. Adding an entry.............................................36
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10.13. Deleting an entry...........................................38
10.14. Extended Operations.........................................39
11. Abandoning An Operation........................................41
12. Obtaining Results and Peeking Inside LDAP Messages.............42
13. Handling Errors and Parsing Results............................44
14. Stepping Through a List of Results.............................46
15. Parsing Search Results.........................................47
15.1. Stepping Through a List of Entries or References............48
15.2. Stepping Through the Attributes of an Entry.................49
15.3. Retrieving the Values of an Attribute.......................50
15.4. Retrieving the name of an entry.............................51
15.5. Retrieving controls from an entry...........................52
15.6. Parsing References..........................................53
16. Encoded ASN.1 Value Manipulation...............................54
16.1. General.....................................................54
16.2. Encoding....................................................55
16.3. Encoding Example............................................58
16.4. Decoding....................................................59
16.5. Decoding Example............................................61
17. Security Considerations........................................64
18. Acknowledgements...............................................64
19. Copyright......................................................64
20. Bibliography...................................................65
21. Authors' Addresses.............................................66
22. Appendix A - Sample C LDAP API Code............................66
23. Appendix B - Namespace Consumed By This Specification..........68
24. Appendix C - Summary of Requirements for API Extensions........68
24.1. Compatibility...............................................69
24.2. Style.......................................................69
24.3. Dependence on Externally Defined Types......................69
24.4. Compile Time Information....................................69
24.5. Runtime Information.........................................69
24.6. Values Used for Session Handle Options......................70
25. Appendix D - Known Incompatibilities with RFC 1823.............70
25.1. Opaque LDAP Structure.......................................70
25.2. Additional Error Codes......................................70
25.3. Freeing of String Data with ldap_memfree()..................71
25.4. Changes to ldap_result()....................................71
25.5. Changes to ldap_first_attribute() and ldap_next_attribute...71
25.6. Changes to ldap_modrdn() and ldap_modrdn_s() Functions......71
25.7. Changes to the berval structure.............................71
25.8. API Specification Clarified.................................72
25.9. Deprecated Functions........................................72
26. Appendix E - Data Types and Legacy Implementations.............72
27. Appendix F - Changes Made Since Last Document Revision.........73
27.1. API Changes.................................................73
27.2. Editorial Changes...........................................74
28. Appendix G - Changes Made Since draft-ietf-ldapext-ldap-c-api-.74
28.1. API Changes.................................................74
28.2. Editorial changes...........................................75
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4. Overview of the LDAP Model
LDAP is the lightweight directory access protocol, described in [2] and
[6]. It can provide a lightweight frontend to the X.500 directory [1],
or a stand-alone service. In either mode, LDAP is based on a client-
server model in which a client makes a TCP connection to an LDAP server,
over which it sends requests and receives responses.
The LDAP information model is based on the entry, which contains infor-
mation about some object (e.g., a person). Entries are composed of
attributes, which have a type and one or more values. Each attribute has
a syntax that determines what kinds of values are allowed in the attri-
bute (e.g., ASCII characters, a jpeg photograph, etc.) and how those
values behave during directory operations (e.g., is case significant
during comparisons).
Entries may be organized in a tree structure, usually based on politi-
cal, geographical, and organizational boundaries. Each entry is uniquely
named relative to its sibling entries by its relative distinguished name
(RDN) consisting of one or more distinguished attribute values from the
entry. At most one value from each attribute may be used in the RDN.
For example, the entry for the person Babs Jensen might be named with
the "Barbara Jensen" value from the commonName attribute.
A globally unique name for an entry, called a distinguished name or DN,
is constructed by concatenating the sequence of RDNs from the entry up
to the root of the tree. For example, if Babs worked for the University
of Michigan, the DN of her U-M entry might be "cn=Barbara Jensen,
o=University of Michigan, c=US". The DN format used by LDAP is defined
in [4].
Operations are provided to authenticate, search for and retrieve infor-
mation, modify information, and add and delete entries from the tree.
The next sections give an overview of how the API is used and detailed
descriptions of the LDAP API calls that implement all of these func-
tions.
5. Overview of LDAP API Use
An application generally uses the C LDAP API in four simple steps.
1. Initialize an LDAP session with a primary LDAP server. The
ldap_init() function returns a handle to the session, allowing
multiple connections to be open at once.
2. Authenticate to the LDAP server. The ldap_sasl_bind() function
and friends support a variety of authentication methods.
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3. Perform some LDAP operations and obtain some results.
ldap_search() and friends return results which can be parsed by
ldap_parse_result(), ldap_first_entry(), ldap_next_entry(), etc.
4. Close the session. The ldap_unbind() function closes the connec-
tion.
Operations can be performed either synchronously or asynchronously. The
names of the synchronous functions end in _s. For example, a synchronous
search can be completed by calling ldap_search_s(). An asynchronous
search can be initiated by calling ldap_search(). All synchronous rou-
tines return an indication of the outcome of the operation (e.g, the
constant LDAP_SUCCESS or some other error code). The asynchronous rou-
tines make available to the caller the message id of the operation ini-
tiated. This id can be used in subsequent calls to ldap_result() to
obtain the result(s) of the operation. An asynchronous operation can be
abandoned by calling ldap_abandon() or ldap_abandon_ext().
Results and errors are returned in an opaque structure called LDAPMes-
sage. Routines are provided to parse this structure, step through
entries and attributes returned, etc. Routines are also provided to
interpret errors. Later sections of this document describe these rou-
tines in more detail.
LDAP version 3 servers may return referrals and references to other
servers. By default, implementations of this API will attempt to follow
referrals automatically for the application. This behavior can be dis-
abled globally (using the ldap_set_option() call) or on a per-request
basis through the use of a client control.
All DN and string attribute values passed into or produced by this C
LDAP API are represented using the character set of the underlying LDAP
protocol version in use. When this API is used with LDAPv3, DN and
string values are represented as UTF-8[10] characters. When this API is
used with LDAPv2, the US-ASCII[12] or T.61[12] character set are used.
Future documents may specific additional APIs supporting other character
sets.
For compatibility with existing applications, implementations of this
API will by default use version 2 of the LDAP protocol. Applications
that intend to take advantage of LDAP version 3 features will need to
use the ldap_set_option() call with a LDAP_OPT_PROTOCOL_VERSION to
switch to version 3.
Note that this API is designed for use in environments where the 'int'
type is at least 32 bits in size.
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6. Header File Requirements
To promote portability of applications, implementations of this C LDAP
API must conform to the following requirements of the header files used
by applications to access the services of this API:
Name and Inclusion
Applications are only required to include a single header file
named ldap.h to access all of the API services described in this
document. Therefore, the following C source program must com-
pile without errors:
#include <ldap.h>
int
main()
{
return 0;
}
Note that it is permissible for the ldap.h header file to
include other implementation-specific header files.
Implementations SHOULD also provide a header file named lber.h to faci-
late development of applications desiring compatibility with older LDAP
implementations. The lber.h header file may be empty.
Idempotence
All header files should be idempotent; that is, if they are
included more than once the effect is as if they had only been
included once.
Must Be Included Before API Is Used
An application must include the ldap.h header file before
referencing any of the function or type definitions described in
this API specification.
Mutual Independence
If possible, header files should be mutually independent with
minimal dependence on system or any other header files.
Use of the 'const' Keyword
This API specification is defined in terms of ISO C[13]. It
makes use of function prototypes and the 'const' keyword. The
use of 'const' in this specification is limited to simple, non-
array function parameters to avoid forcing applications to
declare parameters and variables that accept return values from
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LDAP API functions as 'const.' Implementations specifically
designed to be used with non-ISO C translators may provide func-
tion declarations without prototypes or function prototypes
without specification of 'const' arguments.
Definition of 'struct timeval'
This API specification uses the 'struct timeval' type. Imple-
mentations of this API should ensure that the struct timeval
type is by default defined as a consequence of including the
ldap.h header file. Because struct timeval is usually defined
in one or more system header files, it is possible for header
file conflicts to occur if ldap.h also defines it or arranges
for it to be defined by including another header file. There-
fore, applications may want to arrange for struct timeval to be
defined before they include ldap.h. To support this, the ldap.h
header file must not itself define struct timeval if the prepro-
cessor symbol LDAP_TYPE_TIMEVAL_DEFINED is defined before ldap.h
is included.
7. Common Data Structures
Some data structures that are common to several LDAP API functions are
defined here:
typedef struct ldap LDAP;
typedef struct ldapmsg LDAPMessage;
typedef struct berelement BerElement;
typedef ber_len_t; /* actual definition is implementation-specific */
typedef ber_tag_t; /* actual definition is implementation-specific */
struct berval {
ber_len_t bv_len;
char *bv_val;
};
struct timeval {
long tv_sec;
long tv_usec;
};
The LDAP structure is an opaque data type that represents an LDAP ses-
sion Typically this corresponds to a connection to a single server, but
it may encompass several server connections in the face of LDAPv3
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referrals.
The LDAPMessage structure is an opaque data type that is used to return
entry, reference, result, and error information. An LDAPMessage struc-
ture may represent the beginning of a list, or chain of messages that
consists of a series of entries, references, and result messages as
returned by LDAP operations such as search. LDAP API functions such as
ldap_parse_result() that operate on message chains that may contain more
than one result message always operate on the first result message in
the chain. See the "Obtaining Results and Peeking Inside LDAP Messages"
section of this document for more information.
The BerElement structure is an opaque data type that is used to hold
data and state information about encoded data. It is described in more
detail in the section "Encoded ASN.1 Value Manipulation" later in this
document.
The ber_len_t type is an unsigned integral data type that is large
enough to contain the length of the largest piece of data supported by
the API implementation. Similarly, the ber_tag_t type is an unsigned
integral data type that is large enough to hold the largest BER tag sup-
ported by the API implementation. Both of these types should be at
least 32 bits in size. See the appendix "Data Types and Legacy Imple-
mentations" for additional considerations.
The berval structure is used to represent arbitrary binary data and its
fields have the following meanings:
bv_len Length of data in bytes.
bv_val A pointer to the data itself.
The timeval structure is used to represent an interval of time and its
fields have the following meanings:
tv_sec Seconds component of time interval.
tv_usec Microseconds component of time interval.
See the earlier section "Header File Requirements" for more information
on struct timeval.
8. Retrieving Information About the API Implementation
Applications developed to this specification need to be able to deter-
mine information about the particular API implementation they are using
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both at compile time and during execution.
8.1. Retrieving Information at Compile Time
All conformant implementations MUST include the following five defini-
tions in a header file so compile time tests can be done by LDAP
software developers:
#define LDAP_API_VERSION level
#define LDAP_VERSION_MIN min-version
#define LDAP_VERSION_MAX max-version
#define LDAP_VENDOR_NAME "vend-name"
#define LDAP_VENDOR_VERSION vend-version
where:
"level" is replaced with the RFC number given to this C LDAP API
specification when it is published as a standards track RFC.
min-version is replaced with the lowest LDAP protocol version sup-
ported by the implementation.
max-version is replaced with the highest LDAP protocol version sup-
ported by the implementation. This should be 3.
"vend-name" is replaced with a text string that identifies the
party that supplies the API implementation.
"vend-version" is a supplier-specific version number multiplied
times 100.
Note that the LDAP_VENDOR_NAME macro may be defined as "" if no vendor
name is available and the LDAP_VENDOR_VERSION macro may be defined as 0
if no vendor-specific version information is available.
For example, if this specification is published as RFC 88888, Netscape
Communication's version 4.0 implementation that supports LDAPv2 and v3
might include macro definitions like these:
#define LDAP_API_VERSION 88888 /* RFC 88888 compliant */
#define LDAP_VERSION_MIN 2
#define LDAP_VERSION_MAX 3
#define LDAP_VENDOR_NAME "Netscape Communications Corp."
#define LDAP_VENDOR_VERSION 400 /* version 4.0 */
and application code can test the C LDAP API version level using a
construct such as this one:
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#if (LDAP_API_VERSION >= 88888)
/* use features supported in RFC 88888 or later */
#endif
Until such time as this document is published as an RFC, implementations
should use the value 2000 plus the revision number of this draft for
LDAP_API_VERSION. For example, the correct value for LDAP_API_VERSION
for revision 03 of this draft is 2003.
Documents that extend this specification SHOULD define a macro of the
form:
#define LDAP_API_FEATURE_x level
where "x" is replaced with a name (textual identifier) for the feature
and "level" is replaced with the number of the RFC that specifies the
API extension. The name SHOULD NOT begin with the string "X_".
For example, if C LDAP API extensions for Transport Layer Security [9]
were published in RFC 99999, that RFC might require conformant implemen-
tations to define a macro like this:
#define LDAP_API_FEATURE_TLS 99999
Private or experimental API extensions may be indicated by defining a
macro of this same form where "x" (the extension's name) begins with the
string "X_" and "level" is replaced with a integer number that is
specific to the extension.
8.2. Retrieving Information During Execution
The ldap_get_option() call (described in greater detail later in this
document) can be used during execution in conjunction with an option
parameter value of LDAP_OPT_API_INFO (0x00) to retrieve some basic
information about the API and about the specific implementation being
used. The ld parameter to ldap_get_option() can be either NULL or a
valid LDAP session handle which was obtained by calling ldap_init().
The optdata parameter to ldap_get_option() MUST be the address of an
LDAPAPIInfo structure which is defined as follows:
typedef struct ldapapiinfo {
int ldapai_info_version; /* version of this struct (1) */
int ldapai_api_version; /* revision of API supported */
int ldapai_protocol_version; /* highest LDAP version supported */
char **ldapai_extensions; /* names of API extensions */
char *ldapai_vendor_name; /* name of supplier */
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int ldapai_vendor_version; /* supplier-specific version times 100 */
} LDAPAPIInfo;
In addition, API implementations MUST include the following macro defin-
ition:
#define LDAP_API_INFO_VERSION 1
Note that the ldapai_info_version field of the LDAPAPIInfo structure
should be set to the value LDAP_API_INFO_VERSION (1) before calling
ldap_get_option() so that it can be checked for consistency. All other
fields are set by the ldap_get_option() function.
The members of the LDAPAPIInfo structure are:
ldapai_info_version
A number that identifies the version of the LDAPAPIInfo struc-
ture. This should be set to the value LDAP_API_INFO_VERSION
(1) before calling ldap_get_option(). If the value received
is not recognized by the API implementation, the
ldap_get_option() function sets ldapai_info_version to a valid
value that would be recognized, sets the ldapai_api_version to
the correct value, and returns an error without filling in any
of the other fields in the LDAPAPIInfo structure.
ldapai_api_version
A number that matches that assigned to the C LDAP API RFC sup-
ported by the API implementation. This should match the value
of the LDAP_API_VERSION macro defined earlier.
ldapai_protocol_version
The highest LDAP protocol version supported by the implementa-
tion. For example, if LDAPv3 is the highest version supported
then this field will be set to 3.
ldapai_extensions
A NULL-terminated array of character strings that lists the
names of the API extensions supported by the LDAP API imple-
mentation. These names will typically match the textual iden-
tifiers that appear in the "x" portion of the
LDAP_API_FEATURE_x macros described above, although the pre-
cise value MUST be defined by documents that specify C LDAP
API extensions. If no API extensions are supported, this
field will be set to NULL. The caller is responsible for
disposing of the memory occupied by this array by passing it
to ldap_value_free() which is described later in this docu-
ment. To retrieve more information about a particular exten-
sion, the ldap_get_option() call can be used with an option
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parameter value of LDAP_OPT_API_FEATURE_INFO (0x15). The opt-
data parameter to the ldap_get_option() MUST be the address of
an LDAPAPIFeatureInfo structure which is defined as follows:
typedef struct ldap_apifeature_info {
int ldapaif_info_version; /* version of this struct (1) */
char *ldapaif_name; /* name of supported feature */
int ldapaif_version; /* revision of supported feature */
} LDAPAPIFeatureInfo;
In addition, API implementations MUST include the following
macro definition:
#define LDAP_FEATURE_INFO_VERSION 1
Note that the ldapaif_info_version field of the LDAPAPI-
FeatureInfo structure should be set to the value
LDAP_FEATURE_INFO_VERSION (1) and the ldapaif_name field
should be set to the extension name string as described below
before ldap_get_option() is called. The call will fill in the
ldapaif_version field of the LDAPAPIFeatureInfo structure.
The members of the LDAPAPIFeatureInfo structure are:
ldapaif_info_version
A number that identifies the version of the LDAPAPI-
FeatureInfo structure. This should be set to the value
LDAP_FEATURE_INFO_VERSION (1) before calling
ldap_get_option(). If the value received is not recognized
by the API implementation, the ldap_get_option() function
sets ldapaif_info_version to a valid value that would be
recognized and returns an error without filling in the
ldapaif_version field in the LDAPAPIFeatureInfo structure.
ldapaif_name
The name of an extension, as returned in the
ldapai_extensions array of the LDAPAPIInfo structure and as
specified in the document that describes the extension.
ldapaif_version
This field will be set as a result of calling
ldap_get_option(). It is a number that matches that
assigned to the C LDAP API extension RFC supported for this
extension. For private or experimental API extensions, the
value is extension-specific. In either case, the value of
ldapaxi_ext_version should be identical to the value of the
LDAP_API_FEATURE_x macro defined for the extension
(described above).
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9. LDAP Error Codes
Many of the LDAP API routines return LDAP error codes, some of which
indicate local errors and some of which may be returned by servers. All
of the LDAP error codes returned will be positive integers. Supported
error codes are (hexadecimal values are given in parentheses after the
constant):
LDAP_SUCCESS (0x00)
LDAP_OPERATIONS_ERROR (0x01)
LDAP_PROTOCOL_ERROR (0x02)
LDAP_TIMELIMIT_EXCEEDED (0x03)
LDAP_SIZELIMIT_EXCEEDED (0x04)
LDAP_COMPARE_FALSE (0x05)
LDAP_COMPARE_TRUE (0x06)
LDAP_STRONG_AUTH_NOT_SUPPORTED (0x07)
LDAP_STRONG_AUTH_REQUIRED (0x08)
LDAP_REFERRAL (0x0a) -- new in LDAPv3
LDAP_ADMINLIMIT_EXCEEDED (0x0b) -- new in LDAPv3
LDAP_UNAVAILABLE_CRITICAL_EXTENSION (0x0c) -- new in LDAPv3
LDAP_CONFIDENTIALITY_REQUIRED (0x0d) -- new in LDAPv3
LDAP_SASL_BIND_IN_PROGRESS (0x0e) -- new in LDAPv3
LDAP_NO_SUCH_ATTRIBUTE (0x10)
LDAP_UNDEFINED_TYPE (0x11)
LDAP_INAPPROPRIATE_MATCHING (0x12)
LDAP_CONSTRAINT_VIOLATION (0x13)
LDAP_TYPE_OR_VALUE_EXISTS (0x14)
LDAP_INVALID_SYNTAX (0x15)
LDAP_NO_SUCH_OBJECT (0x20)
LDAP_ALIAS_PROBLEM (0x21)
LDAP_INVALID_DN_SYNTAX (0x22)
LDAP_IS_LEAF (0x23) -- not used in LDAPv3
LDAP_ALIAS_DEREF_PROBLEM (0x24)
LDAP_INAPPROPRIATE_AUTH (0x30)
LDAP_INVALID_CREDENTIALS (0x31)
LDAP_INSUFFICIENT_ACCESS (0x32)
LDAP_BUSY (0x33)
LDAP_UNAVAILABLE (0x34)
LDAP_UNWILLING_TO_PERFORM (0x35)
LDAP_LOOP_DETECT (0x36)
LDAP_NAMING_VIOLATION (0x40)
LDAP_OBJECT_CLASS_VIOLATION (0x41)
LDAP_NOT_ALLOWED_ON_NONLEAF (0x42)
LDAP_NOT_ALLOWED_ON_RDN (0x43)
LDAP_ALREADY_EXISTS (0x44)
LDAP_NO_OBJECT_CLASS_MODS (0x45)
LDAP_RESULTS_TOO_LARGE (0x46) -- reserved for CLDAP
LDAP_AFFECTS_MULTIPLE_DSAS (0x47) -- new in LDAPv3
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LDAP_OTHER (0x50)
LDAP_SERVER_DOWN (0x51)
LDAP_LOCAL_ERROR (0x52)
LDAP_ENCODING_ERROR (0x53)
LDAP_DECODING_ERROR (0x54)
LDAP_TIMEOUT (0x55)
LDAP_AUTH_UNKNOWN (0x56)
LDAP_FILTER_ERROR (0x57)
LDAP_USER_CANCELLED (0x58)
LDAP_PARAM_ERROR (0x59)
LDAP_NO_MEMORY (0x5a)
LDAP_CONNECT_ERROR (0x5b)
LDAP_NOT_SUPPORTED (0x5c)
LDAP_CONTROL_NOT_FOUND (0x5d)
LDAP_NO_RESULTS_RETURNED (0x5e)
LDAP_MORE_RESULTS_TO_RETURN (0x5f)
LDAP_CLIENT_LOOP (0x60)
LDAP_REFERRAL_LIMIT_EXCEEDED (0x61)
10. Performing LDAP Operations
This section describes each LDAP operation API call in detail. All func-
tions take a "session handle," a pointer to an LDAP structure containing
per-connection information. Many routines return results in an LDAPMes-
sage structure. These structures and others are described as needed
below.
10.1. Initializing an LDAP Session
ldap_init() initializes a session with an LDAP server. The server is not
actually contacted until an operation is performed that requires it,
allowing various options to be set after initialization.
LDAP *ldap_init(
const char *hostname,
int portno
);
Use of the following routine is deprecated:
LDAP *ldap_open(
const char *hostname,
int portno
);
Unlike ldap_init(), ldap_open() attempts to make a server connection
before returning to the caller.
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Parameters are:
hostname Contains a space-separated list of hostnames or dotted strings
representing the IP address of hosts running an LDAP server to
connect to. Each hostname in the list can include an optional
port number which is separated from the host itself with a
colon (:) character. The hosts will be tried in the order
listed, stopping with the first one to which a successful con-
nection is made.
Note: A suitable representation for including a literal IPv6[11]
address in the hostname parameter is desired, but has not yet been
determined or implemented in practice.
portno Contains the TCP port number to connect to. The default LDAP
port of 389 can be obtained by supplying the constant
LDAP_PORT. If a host includes a port number then this parame-
ter is ignored.
ldap_init() and ldap_open() both return a "session handle," a pointer to
an opaque structure that should be passed to subsequent calls pertaining
to the session. These routines return NULL if the session cannot be ini-
tialized in which case the operating system error reporting mechanism
can be checked to see why the call failed.
Note that if you connect to an LDAPv2 server, one of the LDAP bind calls
described below must be completed before other operations can be per-
formed on the session. LDAPv3 does not require that a bind operation be
completed before other operations can be performed.
The calling program can set various attributes of the session by calling
the routines described in the next section.
10.2. LDAP Session Handle Options
The LDAP session handle returned by ldap_init() is a pointer to an
opaque data type representing an LDAP session. In RFC 1823 this data
type was a structure exposed to the caller, and various fields in the
structure could be set to control aspects of the session, such as size
and time limits on searches.
In the interest of insulating callers from inevitable changes to this
structure, these aspects of the session are now accessed through a pair
of accessor functions, described below.
ldap_get_option() is used to access the current value of various
session-wide parameters. ldap_set_option() is used to set the value of
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these parameters. Note that some options are READ-ONLY and cannot be
set; it is an error to call ldap_set_option() and attempt to set a
READ-ONLY option.
Note that if automatic referral following is enabled (the default), any
connections created during the course of following referrals will
inherit the options associated with the session that sent the original
request that caused the referrals to be returned.
int ldap_get_option(
LDAP *ld,
int option,
void *outvalue
);
int ldap_set_option(
LDAP *ld,
int option,
const void *invalue
);
#define LDAP_OPT_ON ((void *)1)
#define LDAP_OPT_OFF ((void *)0)
Parameters are:
ld The session handle. If this is NULL, a set of global defaults is
accessed. New LDAP session handles created with ldap_init() or
ldap_open() inherit their characteristics from these global
defaults.
option The name of the option being accessed or set. This parameter
should be one of the following constants, which have the indi-
cated meanings. After the constant the actual hexadecimal value
of the constant is listed in parentheses.
LDAP_OPT_API_INFO (0x00)
Type for invalue parameter: not applicable (option is READ-ONLY)
Type for outvalue parameter: LDAPAPIInfo *
Description:
Used to retrieve some basic information about the LDAP API
implementation at execution time. See the section "Retriev-
ing Information About the API Implementation" above for more
information. This option is READ-ONLY and cannot be set.
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LDAP_OPT_DESC (0x01)
Type for invalue parameter: not applicable (option is READ-
ONLY)
Type for outvalue parameter: int *
Description:
The underlying socket descriptor corresponding to the pri-
mary LDAP connection. This option is READ-ONLY and cannot
be set.
LDAP_OPT_DEREF (0x02)
Type for invalue parameter: int *
Type for outvalue parameter: int *
Description:
Determines how aliases are handled during search. It can
have one of the following values: LDAP_DEREF_NEVER (0x00),
LDAP_DEREF_SEARCHING (0x01), LDAP_DEREF_FINDING (0x02), or
LDAP_DEREF_ALWAYS (0x03). The LDAP_DEREF_SEARCHING value
means aliases should be dereferenced during the search but
not when locating the base object of the search. The
LDAP_DEREF_FINDING value means aliases should be derefer-
enced when locating the base object but not during the
search.
LDAP_OPT_SIZELIMIT (0x03)
Type for invalue parameter: int *
Type for outvalue parameter: int *
Description:
A limit on the number of entries to return from a search.
A value of LDAP_NO_LIMIT (0) means no limit.
LDAP_OPT_TIMELIMIT (0x04)
Type for invalue parameter: int *
Type for outvalue parameter: int *
Description:
A limit on the number of seconds to spend on a search. A
value of LDAP_NO_LIMIT (0) means no limit. This value is
passed to the server in the search request only; it does
not affect how long the C LDAP API implementation itself
will wait locally for search results. The timeout parame-
ter passed to ldap_search_ext_s() or ldap_result() -- both
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of which are described later in this document -- can be
used to specify both a local and server side time limit.
LDAP_OPT_REFERRALS (0x08)
Type for invalue parameter: void * (LDAP_OPT_ON or
LDAP_OPT_OFF)
Type for outvalue parameter: int *
Description:
Determines whether the LDAP library automatically follows
referrals returned by LDAP servers or not. It can be set
to one of the constants LDAP_OPT_ON or LDAP_OPT_OFF; any
non-NULL pointer value passed to ldap_set_option() enables
this option. When reading the current setting using
ldap_get_option(), a zero value means off and any non-zero
value means on.
LDAP_OPT_RESTART (0x09)
Type for invalue parameter: void * (LDAP_OPT_ON or
LDAP_OPT_OFF)
Type for outvalue parameter: int *
Description:
Determines whether LDAP I/O operations should automati-
cally be restarted if they abort prematurely. It should be
set to one of the constants LDAP_OPT_ON or LDAP_OPT_OFF;
any non-NULL pointer value passed to ldap_set_option()
enables this option. When reading the current setting
using ldap_get_option(), a zero value means off and any
non-zero value means on. This option is useful if an LDAP
I/O operation may be interrupted prematurely, for example
by a timer going off, or other interrupt.
LDAP_OPT_PROTOCOL_VERSION (0x11)
Type for invalue parameter: int *
Type for outvalue parameter: int *
Description:
This option indicates the version of the LDAP protocol
used when communicating with the primary LDAP server. It
must be one of the constants LDAP_VERSION2 (2) or
LDAP_VERSION3 (3). If no version is set the default is
LDAP_VERSION2 (2).
LDAP_OPT_SERVER_CONTROLS (0x12)
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Type for invalue parameter: LDAPControl **
Type for outvalue parameter: LDAPControl ***
Description:
A default list of LDAP server controls to be sent with
each request. See the Working With Controls section
below.
LDAP_OPT_CLIENT_CONTROLS (0x13)
Type for invalue parameter: LDAPControl **
Type for outvalue parameter: LDAPControl ***
Description:
A default list of client controls that affect the LDAP
session. See the Working With Controls section below.
LDAP_OPT_API_FEATURE_INFO (0x15)
Type for invalue parameter: not applicable (option is READ-
ONLY)
Type for outvalue parameter: LDAPAPIFeatureInfo *
Description:
Used to retrieve version information about LDAP API
extended features at execution time. See the section
"Retrieving Information About the API Implementation"
above for more information. This option is READ-ONLY and
cannot be set.
LDAP_OPT_HOST_NAME (0x30)
Type for invalue parameter: char *
Type for outvalue parameter: char **
Description:
The host name (or list of hosts) for the primary LDAP
server. See the definition of the hostname parameter to
ldap_init() for the allowed syntax.
LDAP_OPT_ERROR_NUMBER (0x31)
Type for invalue parameter: int *
Type for outvalue parameter: int *
Description:
The code of the most recent LDAP error that occurred for
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this session.
LDAP_OPT_ERROR_STRING (0x32)
Type for invalue parameter: char *
Type for outvalue parameter: char **
Description:
The message returned with the most recent LDAP error that
occurred for this session.
outvalue The address of a place to put the value of the option. The
actual type of this parameter depends on the setting of the
option parameter. For outvalues of type char ** and LDAP-
Control **, a copy of the data that is associated with the
LDAP session ld is returned; callers should dispose of the
memory by calling ldap_memfree() or ldap_controls_free().
invalue A pointer to the value the option is to be given. The actual
type of this parameter depends on the setting of the option
parameter. The data associated with invalue is copied by the
API implementation to allow callers of the API to dispose of
or otherwise change their copy of the data after a success-
ful call to ldap_set_option(). If a value passed for
invalue is invalid or cannot be accepted by the implementa-
tion, ldap_set_option() should return -1 to indicate an
error.
Both ldap_get_option() and ldap_set_option() return 0 if successful and
-1 if an error occurs.
Standards track documents that extend this specification and specify new
options MUST use values for option macros that are between 0x1000 and
0x3FFF inclusive. Private and experimental extensions MUST use values
for the option macros that are between 0x4000 and 0x7FFF inclusive. All
values below 0x1000 and above 0x7FFF that are not defined in this docu-
ment are reserved and MUST NOT be used.
10.3. Working With Controls
LDAPv3 operations can be extended through the use of controls. Controls
may be sent to a server or returned to the client with any LDAP message.
These controls are referred to as server controls.
The LDAP API also supports a client-side extension mechanism through the
use of client controls. These controls affect the behavior of the LDAP
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API only and are never sent to a server. A common data structure is
used to represent both types of controls:
typedef struct ldapcontrol {
char *ldctl_oid;
struct berval ldctl_value;
char ldctl_iscritical;
} LDAPControl, *PLDAPControl;
The fields in the ldapcontrol structure have the following meanings:
ldctl_oid The control type, represented as a string.
ldctl_value The data associated with the control (if any). To
specify a zero-length value, set ldctl_value.bv_len to
zero and ldctl_value.bv_val to a zero-length string.
To indicate that no data is associated with the con-
trol, set ldctl_value.bv_val to NULL.
ldctl_iscritical Indicates whether the control is critical of not. If
this field is non-zero, the operation will only be car-
ried out if the control is recognized by the server
and/or client. Note that the LDAP unbind and abandon
operations have no server response, so clients SHOULD
NOT mark server controls critical when used with these
two operations.
Some LDAP API calls allocate an ldapcontrol structure or a NULL-
terminated array of ldapcontrol structures. The following routines can
be used to dispose of a single control or an array of controls:
void ldap_control_free( LDAPControl *ctrl );
void ldap_controls_free( LDAPControl **ctrls );
A set of controls that affect the entire session can be set using the
ldap_set_option() function (see above). A list of controls can also be
passed directly to some LDAP API calls such as ldap_search_ext(), in
which case any controls set for the session through the use of
ldap_set_option() are ignored. Control lists are represented as a NULL-
terminated array of pointers to ldapcontrol structures.
Server controls are defined by LDAPv3 protocol extension documents; for
example, a control has been proposed to support server-side sorting of
search results [7].
One client control is defined in this document (described in the follow-
ing section). Other client controls may be defined in future revisions
of this document or in documents that extend this API.
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10.3.1. A Client Control That Governs Referral Processing
As described previously in the section "LDAP Session Handle Options,"
applications can enable and disable automatic chasing of referrals on a
session-wide basic by using the ldap_set_option() function with the
LDAP_OPT_REFERRALS option. It is also useful to govern automatic refer-
ral chasing on per-request basis. A client control with an OID of
1.2.840.113556.1.4.616 exists to provide this functionality.
/* OID for referrals client control */
#define LDAP_CONTROL_REFERRALS "1.2.840.113556.1.4.616"
/* Flags for referrals client control value */
#define LDAP_CHASE_SUBORDINATE_REFERRALS 0x00000020
#define LDAP_CHASE_EXTERNAL_REFERRALS 0x00000040
To create a referrals client control, the ldctl_oid field of an LDAPCon-
trol structure should be set to LDAP_CONTROL_REFERRALS
("1.2.840.113556.1.4.616") and the ldctl_value field should be set to a
4-octet value that contains a set of flags. The ldctl_value.bv_len
field should always be set to 4. The ldctl_value.bv_val field should
point to a 4-octet integer flags value. This flags value can be set to
zero to disable automatic chasing of referrals and LDAPv3 references
altogether. Alternatively, the flags value can be set to the value
LDAP_CHASE_SUBORDINATE_REFERRALS (0x00000020) to indicate that only
LDAPv3 search continuation references should be automatically chased by
the API implementation, to the value LDAP_CHASE_EXTERNAL_REFERRALS
(0x00000040) to indicate that only LDAPv3 referrals should be automati-
cally chased, or the logical OR of the two flag values (0x00000060) to
indicate that both referrals and references should be automatically
chased.
10.4. Authenticating to the directory
The following functions are used to authenticate an LDAP client to an
LDAP directory server.
The ldap_sasl_bind() and ldap_sasl_bind_s() functions can be used to do
general and extensible authentication over LDAP through the use of the
Simple Authentication Security Layer [8]. The routines both take the dn
to bind as, the method to use, as a dotted-string representation of an
OID identifying the method, and a struct berval holding the credentials.
The special constant value LDAP_SASL_SIMPLE (NULL) can be passed to
request simple authentication, or the simplified routines
ldap_simple_bind() or ldap_simple_bind_s() can be used.
int ldap_sasl_bind(
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LDAP *ld,
const char *dn,
const char *mechanism,
const struct berval *cred,
LDAPControl **serverctrls,
LDAPControl **clientctrls,
int *msgidp
);
int ldap_sasl_bind_s(
LDAP *ld,
const char *dn,
const char *mechanism,
const struct berval *cred,
LDAPControl **serverctrls,
LDAPControl **clientctrls,
struct berval **servercredp
);
int ldap_simple_bind(
LDAP *ld,
const char *dn,
const char *passwd
);
int ldap_simple_bind_s(
LDAP *ld,
const char *dn,
const char *passwd
);
The use of the following routines is deprecated:
int ldap_bind( LDAP *ld, const char *dn, const char *cred,
int method );
int ldap_bind_s( LDAP *ld, const char *dn, const char *cred,
int method );
int ldap_kerberos_bind( LDAP *ld, const char *dn );
int ldap_kerberos_bind_s( LDAP *ld, const char *dn );
Parameters are:
ld The session handle.
dn The name of the entry to bind as.
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mechanism Either LDAP_SASL_SIMPLE (NULL) to get simple authentica-
tion, or a text string identifying the SASL method.
cred The credentials with which to authenticate. Arbitrary
credentials can be passed using this parameter. The format
and content of the credentials depends on the setting of
the mechanism parameter.
passwd For ldap_simple_bind(), the password to compare to the
entry's userPassword attribute.
serverctrls List of LDAP server controls.
clientctrls List of client controls.
msgidp This result parameter will be set to the message id of the
request if the ldap_sasl_bind() call succeeds.
servercredp This result parameter will be filled in with the creden-
tials passed back by the server for mutual authentication,
if given. An allocated berval structure is returned that
should be disposed of by calling ber_bvfree(). NULL may be
passed to ignore this field.
Additional parameters for the deprecated routines are not described.
Interested readers are referred to RFC 1823.
The ldap_sasl_bind() function initiates an asynchronous bind operation
and returns the constant LDAP_SUCCESS if the request was successfully
sent, or another LDAP error code if not. See the section below on error
handling for more information about possible errors and how to interpret
them. If successful, ldap_sasl_bind() places the message id of the
request in *msgidp. A subsequent call to ldap_result(), described below,
can be used to obtain the result of the bind.
The ldap_simple_bind() function initiates a simple asynchronous bind
operation and returns the message id of the operation initiated. A sub-
sequent call to ldap_result(), described below, can be used to obtain
the result of the bind. In case of error, ldap_simple_bind() will return
-1, setting the session error parameters in the LDAP structure appropri-
ately.
The synchronous ldap_sasl_bind_s() and ldap_simple_bind_s() functions
both return the result of the operation, either the constant
LDAP_SUCCESS if the operation was successful, or another LDAP error code
if it was not. See the section below on error handling for more informa-
tion about possible errors and how to interpret them.
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Note that if an LDAPv2 server is contacted, no other operations over the
connection should be attempted before a bind call has successfully com-
pleted.
Subsequent bind calls can be used to re-authenticate over the same con-
nection, and multistep SASL sequences can be accomplished through a
sequence of calls to ldap_sasl_bind() or ldap_sasl_bind_s().
10.5. Closing the session
The following functions are used to unbind from the directory, close
open connections, and dispose of the session handle.
int ldap_unbind_ext( LDAP *ld, LDAPControl **serverctrls,
LDAPControl **clientctrls );
int ldap_unbind( LDAP *ld );
int ldap_unbind_s( LDAP *ld );
Parameters are:
ld The session handle.
serverctrls List of LDAP server controls.
clientctrls List of client controls.
The ldap_unbind_ext(), ldap_unbind() and ldap_unbind_s() all work syn-
chronously in the sense that they send an unbind request to the server,
close all open connections associated with the LDAP session handle, and
dispose of all resources associated with the session handle before
returning. Note, however, that there is no server response to an LDAP
unbind operation. All three of the unbind functions return LDAP_SUCCESS
(or another LDAP error code if the request cannot be sent to the LDAP
server). After a call to one of the unbind functions, the session han-
dle ld is invalid and it is illegal to make any further LDAP API calls
using ld.
The ldap_unbind() and ldap_unbind_s() functions behave identically. The
ldap_unbind_ext() function allows server and client controls to be
included explicitly, but note that since there is no server response to
an unbind request there is no way to receive a response to a server con-
trol sent with an unbind request.
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10.6. Searching
The following functions are used to search the LDAP directory, returning
a requested set of attributes for each entry matched. There are five
variations.
int ldap_search_ext(
LDAP *ld,
const char *base,
int scope,
const char *filter,
char **attrs,
int attrsonly,
LDAPControl **serverctrls,
LDAPControl **clientctrls,
struct timeval *timeout,
int sizelimit,
int *msgidp
);
int ldap_search_ext_s(
LDAP *ld,
const char *base,
int scope,
const char *filter,
char **attrs,
int attrsonly,
LDAPControl **serverctrls,
LDAPControl **clientctrls,
struct timeval *timeout,
int sizelimit,
LDAPMessage **res
);
int ldap_search(
LDAP *ld,
const char *base,
int scope,
const char *filter,
char **attrs,
int attrsonly
);
int ldap_search_s(
LDAP *ld,
const char *base,
int scope,
const char *filter,
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char **attrs,
int attrsonly,
LDAPMessage **res
);
int ldap_search_st(
LDAP *ld,
const char *base,
int scope,
const char *filter,
char **attrs,
int attrsonly,
struct timeval *timeout,
LDAPMessage **res
);
Parameters are:
ld The session handle.
base The dn of the entry at which to start the search.
scope One of LDAP_SCOPE_BASE (0x00), LDAP_SCOPE_ONELEVEL (0x01),
or LDAP_SCOPE_SUBTREE (0x02), indicating the scope of the
search.
filter A character string as described in [3], representing the
search filter. The value NULL can be passed to indicate
that the filter "(objectclass=*)" which matches all entries
should be used. Note that if the caller of the API is
using LDAPv2, only a subset of the filter functionality
described in [3] can be successfully used.
attrs A NULL-terminated array of strings indicating which attri-
butes to return for each matching entry. Passing NULL for
this parameter causes all available user attributes to be
retrieved. The special constant string LDAP_NO_ATTRS
("1.1") can be used as the only string in the array to
indicate that no attribute types should be returned by the
server. The special constant string LDAP_ALL_USER_ATTRS
("*") can be used in the attrs array along with the names
of some operational attributes to indicate that all user
attributes plus the listed operational attributes should be
returned.
attrsonly A boolean value that should be zero if both attribute types
and values are to be returned, non-zero if only types are
wanted.
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timeout For the ldap_search_st() function, this specifies the local
search timeout value (if it is NULL, the timeout is infin-
ite). For the ldap_search_ext() and ldap_search_ext_s()
functions, this specifies both the local search timeout
value and the operation time limit that is sent to the
server within the search request. For the
ldap_search_ext() and ldap_search_ext_s() functions, pass-
ing a NULL value for timeout causes the global default
timeout stored in the LDAP session handle (set by using
ldap_set_option() with the LDAP_OPT_TIMELIMIT parameter) to
be sent to the server with the request but an infinite
local search timeout to be used.
sizelimit For the ldap_search_ext() and ldap_search_ext_s() calls,
this is a limit on the number of entries to return from the
search. A value of LDAP_NO_LIMIT (0) means no limit.
res For the synchronous calls, this is a result parameter which
will contain the results of the search upon completion of
the call. If no results are returned, *res is set to NULL.
serverctrls List of LDAP server controls.
clientctrls List of client controls.
msgidp This result parameter will be set to the message id of the
request if the ldap_search_ext() call succeeds.
There are three options in the session handle ld which potentially
affect how the search is performed. They are:
LDAP_OPT_SIZELIMIT
A limit on the number of entries to return from the search.
A value of LDAP_NO_LIMIT (0) means no limit. Note that the
value from the session handle is ignored when using the
ldap_search_ext() or ldap_search_ext_s() functions.
LDAP_OPT_TIMELIMIT
A limit on the number of seconds to spend on the search. A
value of LDAP_NO_LIMIT (0) means no limit. Note that the
value from the session handle is ignored when using the
ldap_search_ext() or ldap_search_ext_s() functions.
LDAP_OPT_DEREF
One of LDAP_DEREF_NEVER (0x00), LDAP_DEREF_SEARCHING
(0x01), LDAP_DEREF_FINDING (0x02), or LDAP_DEREF_ALWAYS
(0x03), specifying how aliases should be handled during the
search. The LDAP_DEREF_SEARCHING value means aliases should
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be dereferenced during the search but not when locating the
base object of the search. The LDAP_DEREF_FINDING value
means aliases should be dereferenced when locating the base
object but not during the search.
The ldap_search_ext() function initiates an asynchronous search opera-
tion and returns the constant LDAP_SUCCESS if the request was success-
fully sent, or another LDAP error code if not. See the section below on
error handling for more information about possible errors and how to
interpret them. If successful, ldap_search_ext() places the message id
of the request in *msgidp. A subsequent call to ldap_result(), described
below, can be used to obtain the results from the search. These results
can be parsed using the result parsing routines described in detail
later.
Similar to ldap_search_ext(), the ldap_search() function initiates an
asynchronous search operation and returns the message id of the opera-
tion initiated. As for ldap_search_ext(), a subsequent call to
ldap_result(), described below, can be used to obtain the result of the
bind. In case of error, ldap_search() will return -1, setting the ses-
sion error parameters in the LDAP structure appropriately.
The synchronous ldap_search_ext_s(), ldap_search_s(), and
ldap_search_st() functions all return the result of the operation,
either the constant LDAP_SUCCESS if the operation was successful, or
another LDAP error code if it was not. See the section below on error
handling for more information about possible errors and how to interpret
them. Entries returned from the search (if any) are contained in the
res parameter. This parameter is opaque to the caller. Entries, attri-
butes, values, etc., should be extracted by calling the parsing routines
described below. The results contained in res should be freed when no
longer in use by calling ldap_msgfree(), described later.
The ldap_search_ext() and ldap_search_ext_s() functions support LDAPv3
server controls, client controls, and allow varying size and time limits
to be easily specified for each search operation. The ldap_search_st()
function is identical to ldap_search_s() except that it takes an addi-
tional parameter specifying a local timeout for the search. The local
search timeout is used to limit the amount of time the API implementa-
tion will wait for a search to complete. After the local search timeout
expires, the API implementation will send an abandon operation to abort
the search operation.
10.7. Reading an Entry
LDAP does not support a read operation directly. Instead, this operation
is emulated by a search with base set to the DN of the entry to read,
scope set to LDAP_SCOPE_BASE, and filter set to "(objectclass=*)" or
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NULL. attrs contains the list of attributes to return.
10.8. Listing the Children of an Entry
LDAP does not support a list operation directly. Instead, this operation
is emulated by a search with base set to the DN of the entry to list,
scope set to LDAP_SCOPE_ONELEVEL, and filter set to "(objectclass=*)" or
NULL. attrs contains the list of attributes to return for each child
entry.
10.9. Comparing a Value Against an Entry
The following routines are used to compare a given attribute value
assertion against an LDAP entry. There are four variations:
int ldap_compare_ext(
LDAP *ld,
const char *dn,
const char *attr,
struct berval *bvalue
LDAPControl **serverctrls,
LDAPControl **clientctrls,
int *msgidp
);
int ldap_compare_ext_s(
LDAP *ld,
const char *dn,
const char *attr,
struct berval *bvalue,
LDAPControl **serverctrls,
LDAPControl **clientctrls
);
int ldap_compare(
LDAP *ld,
const char *dn,
const char *attr,
const char *value
);
int ldap_compare_s(
LDAP *ld,
const char *dn,
const char *attr,
const char *value
);
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Parameters are:
ld The session handle.
dn The name of the entry to compare against.
attr The attribute to compare against.
bvalue The attribute value to compare against those found in the
given entry. This parameter is used in the extended rou-
tines and is a pointer to a struct berval so it is possible
to compare binary values.
value A string attribute value to compare against, used by the
ldap_compare() and ldap_compare_s() functions. Use
ldap_compare_ext() or ldap_compare_ext_s() if you need to
compare binary values.
serverctrls List of LDAP server controls.
clientctrls List of client controls.
msgidp This result parameter will be set to the message id of the
request if the ldap_compare_ext() call succeeds.
The ldap_compare_ext() function initiates an asynchronous compare opera-
tion and returns the constant LDAP_SUCCESS if the request was success-
fully sent, or another LDAP error code if not. See the section below on
error handling for more information about possible errors and how to
interpret them. If successful, ldap_compare_ext() places the message id
of the request in *msgidp. A subsequent call to ldap_result(), described
below, can be used to obtain the result of the compare.
Similar to ldap_compare_ext(), the ldap_compare() function initiates an
asynchronous compare operation and returns the message id of the opera-
tion initiated. As for ldap_compare_ext(), a subsequent call to
ldap_result(), described below, can be used to obtain the result of the
bind. In case of error, ldap_compare() will return -1, setting the ses-
sion error parameters in the LDAP structure appropriately.
The synchronous ldap_compare_ext_s() and ldap_compare_s() functions both
return the result of the operation, either the constant LDAP_SUCCESS if
the operation was successful, or another LDAP error code if it was not.
See the section below on error handling for more information about pos-
sible errors and how to interpret them.
The ldap_compare_ext() and ldap_compare_ext_s() functions support LDAPv3
server controls and client controls.
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10.10. Modifying an entry
The following routines are used to modify an existing LDAP entry. There
are four variations:
typedef struct ldapmod {
int mod_op;
char *mod_type;
union {
char **modv_strvals;
struct berval **modv_bvals;
} mod_vals;
} LDAPMod;
#define mod_values mod_vals.modv_strvals
#define mod_bvalues mod_vals.modv_bvals
int ldap_modify_ext(
LDAP *ld,
const char *dn,
LDAPMod **mods,
LDAPControl **serverctrls,
LDAPControl **clientctrls,
int *msgidp
);
int ldap_modify_ext_s(
LDAP *ld,
const char *dn,
LDAPMod **mods,
LDAPControl **serverctrls,
LDAPControl **clientctrls
);
int ldap_modify(
LDAP *ld,
const char *dn,
LDAPMod **mods
);
int ldap_modify_s(
LDAP *ld,
const char *dn,
LDAPMod **mods
);
Parameters are:
ld The session handle.
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dn The name of the entry to modify.
mods A NULL-terminated array of modifications to make to the
entry.
serverctrls List of LDAP server controls.
clientctrls List of client controls.
msgidp This result parameter will be set to the message id of the
request if the ldap_modify_ext() call succeeds.
The fields in the LDAPMod structure have the following meanings:
mod_op The modification operation to perform. It should be one of
LDAP_MOD_ADD (0x00), LDAP_MOD_DELETE (0x01), or
LDAP_MOD_REPLACE (0x02). This field also indicates the
type of values included in the mod_vals union. It is logi-
cally ORed with LDAP_MOD_BVALUES (0x80) to select the
mod_bvalues form. Otherwise, the mod_values form is used.
mod_type The type of the attribute to modify.
mod_vals The values (if any) to add, delete, or replace. Only one of
the mod_values or mod_bvalues variants should be used,
selected by ORing the mod_op field with the constant
LDAP_MOD_BVALUES. mod_values is a NULL-terminated array of
zero-terminated strings and mod_bvalues is a NULL-
terminated array of berval structures that can be used to
pass binary values such as images.
For LDAP_MOD_ADD modifications, the given values are added to the
entry, creating the attribute if necessary.
For LDAP_MOD_DELETE modifications, the given values are deleted from the
entry, removing the attribute if no values remain. If the entire attri-
bute is to be deleted, the mod_vals field should be set to NULL.
For LDAP_MOD_REPLACE modifications, the attribute will have the listed
values after the modification, having been created if necessary, or
removed if the mod_vals field is NULL. All modifications are performed
in the order in which they are listed.
The ldap_modify_ext() function initiates an asynchronous modify opera-
tion and returns the constant LDAP_SUCCESS if the request was success-
fully sent, or another LDAP error code if not. See the section below on
error handling for more information about possible errors and how to
interpret them. If successful, ldap_modify_ext() places the message id
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of the request in *msgidp. A subsequent call to ldap_result(), described
below, can be used to obtain the result of the modify.
Similar to ldap_modify_ext(), the ldap_modify() function initiates an
asynchronous modify operation and returns the message id of the opera-
tion initiated. As for ldap_modify_ext(), a subsequent call to
ldap_result(), described below, can be used to obtain the result of the
modify. In case of error, ldap_modify() will return -1, setting the ses-
sion error parameters in the LDAP structure appropriately.
The synchronous ldap_modify_ext_s() and ldap_modify_s() functions both
return the result of the operation, either the constant LDAP_SUCCESS if
the operation was successful, or another LDAP error code if it was not.
See the section below on error handling for more information about pos-
sible errors and how to interpret them.
The ldap_modify_ext() and ldap_modify_ext_s() functions support LDAPv3
server controls and client controls.
10.11. Modifying the Name of an Entry
In LDAPv2, the ldap_modrdn(), ldap_modrdn_s(), ldap_modrdn2(), and
ldap_modrdn2_s() routines were used to change the name of an LDAP entry.
They could only be used to change the least significant component of a
name (the RDN or relative distinguished name). LDAPv3 provides the
Modify DN protocol operation that allows more general name change
access. The ldap_rename() and ldap_rename_s() routines are used to
change the name of an entry, and the use of the ldap_modrdn(),
ldap_modrdn_s(), ldap_modrdn2(), and ldap_modrdn2_s() routines is depre-
cated.
int ldap_rename(
LDAP *ld,
const char *dn,
const char *newrdn,
const char *newparent,
int deleteoldrdn,
LDAPControl **serverctrls,
LDAPControl **clientctrls,
int *msgidp
);
int ldap_rename_s(
LDAP *ld,
const char *dn,
const char *newrdn,
const char *newparent,
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int deleteoldrdn,
LDAPControl **serverctrls,
LDAPControl **clientctrls
);
Use of the following routines is deprecated.
int ldap_modrdn(
LDAP *ld,
const char *dn,
const char *newrdn
);
int ldap_modrdn_s(
LDAP *ld,
const char *dn,
const char *newrdn
);
int ldap_modrdn2(
LDAP *ld,
const char *dn,
const char *newrdn,
int deleteoldrdn
);
int ldap_modrdn2_s(
LDAP *ld,
const char *dn,
const char *newrdn,
int deleteoldrdn
);
Parameters are:
ld The session handle.
dn The name of the entry whose DN is to be changed.
newrdn The new RDN to give the entry.
newparent The new parent, or superior entry. If this parameter is
NULL, only the RDN of the entry is changed. The root DN
may be specified by passing a zero length string, "". The
newparent parameter should always be NULL when using ver-
sion 2 of the LDAP protocol; otherwise the server's
behavior is undefined.
deleteoldrdn This parameter only has meaning on the rename routines if
newrdn is different than the old RDN. It is a boolean
value, if non-zero indicating that the old RDN value(s)
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should be removed, if zero indicating that the old RDN
value(s) should be retained as non-distinguished values of
the entry.
serverctrls List of LDAP server controls.
clientctrls List of client controls.
msgidp This result parameter will be set to the message id of the
request if the ldap_rename() call succeeds.
The ldap_rename() function initiates an asynchronous modify DN operation
and returns the constant LDAP_SUCCESS if the request was successfully
sent, or another LDAP error code if not. See the section below on error
handling for more information about possible errors and how to interpret
them. If successful, ldap_rename() places the DN message id of the
request in *msgidp. A subsequent call to ldap_result(), described below,
can be used to obtain the result of the rename.
The synchronous ldap_rename_s() returns the result of the operation,
either the constant LDAP_SUCCESS if the operation was successful, or
another LDAP error code if it was not. See the section below on error
handling for more information about possible errors and how to interpret
them.
The ldap_rename() and ldap_rename_s() functions both support LDAPv3
server controls and client controls.
10.12. Adding an entry
The following functions are used to add entries to the LDAP directory.
There are four variations:
int ldap_add_ext(
LDAP *ld,
const char *dn,
LDAPMod **attrs,
LDAPControl **serverctrls,
LDAPControl **clientctrls,
int *msgidp
);
int ldap_add_ext_s(
LDAP *ld,
const char *dn,
LDAPMod **attrs,
LDAPControl **serverctrls,
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LDAPControl **clientctrls
);
int ldap_add(
LDAP *ld,
const char *dn,
LDAPMod **attrs
);
int ldap_add_s(
LDAP *ld,
const char *dn,
LDAPMod **attrs
);
Parameters are:
ld The session handle.
dn The name of the entry to add.
attrs The entry's attributes, specified using the LDAPMod struc-
ture defined for ldap_modify(). The mod_type and mod_vals
fields should be filled in. The mod_op field is ignored
unless ORed with the constant LDAP_MOD_BVALUES, used to
select the mod_bvalues case of the mod_vals union.
serverctrls List of LDAP server controls.
clientctrls List of client controls.
msgidp This result parameter will be set to the message id of the
request if the ldap_add_ext() call succeeds.
Note that the parent of the entry being added must already exist or the
parent must be empty (i.e., equal to the root DN) for an add to succeed.
The ldap_add_ext() function initiates an asynchronous add operation and
returns the constant LDAP_SUCCESS if the request was successfully sent,
or another LDAP error code if not. See the section below on error han-
dling for more information about possible errors and how to interpret
them. If successful, ldap_add_ext() places the message id of the
request in *msgidp. A subsequent call to ldap_result(), described below,
can be used to obtain the result of the add.
Similar to ldap_add_ext(), the ldap_add() function initiates an asyn-
chronous add operation and returns the message id of the operation ini-
tiated. As for ldap_add_ext(), a subsequent call to ldap_result(),
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described below, can be used to obtain the result of the add. In case of
error, ldap_add() will return -1, setting the session error parameters
in the LDAP structure appropriately.
The synchronous ldap_add_ext_s() and ldap_add_s() functions both return
the result of the operation, either the constant LDAP_SUCCESS if the
operation was successful, or another LDAP error code if it was not. See
the section below on error handling for more information about possible
errors and how to interpret them.
The ldap_add_ext() and ldap_add_ext_s() functions support LDAPv3 server
controls and client controls.
10.13. Deleting an entry
The following functions are used to delete a leaf entry from the LDAP
directory. There are four variations:
int ldap_delete_ext(
LDAP *ld,
const char *dn,
LDAPControl **serverctrls,
LDAPControl **clientctrls,
int *msgidp
);
int ldap_delete_ext_s(
LDAP *ld,
const char *dn,
LDAPControl **serverctrls,
LDAPControl **clientctrls
);
int ldap_delete(
LDAP *ld,
const char *dn
);
int ldap_delete_s(
LDAP *ld,
const char *dn
);
Parameters are:
ld The session handle.
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dn The name of the entry to delete.
serverctrls List of LDAP server controls.
clientctrls List of client controls.
msgidp This result parameter will be set to the message id of the
request if the ldap_delete_ext() call succeeds.
Note that the entry to delete must be a leaf entry (i.e., it must have
no children). Deletion of entire subtrees in a single operation is not
supported by LDAP.
The ldap_delete_ext() function initiates an asynchronous delete opera-
tion and returns the constant LDAP_SUCCESS if the request was success-
fully sent, or another LDAP error code if not. See the section below on
error handling for more information about possible errors and how to
interpret them. If successful, ldap_delete_ext() places the message id
of the request in *msgidp. A subsequent call to ldap_result(), described
below, can be used to obtain the result of the delete.
Similar to ldap_delete_ext(), the ldap_delete() function initiates an
asynchronous delete operation and returns the message id of the opera-
tion initiated. As for ldap_delete_ext(), a subsequent call to
ldap_result(), described below, can be used to obtain the result of the
delete. In case of error, ldap_delete() will return -1, setting the ses-
sion error parameters in the LDAP structure appropriately.
The synchronous ldap_delete_ext_s() and ldap_delete_s() functions both
return the result of the operation, either the constant LDAP_SUCCESS if
the operation was successful, or another LDAP error code if it was not.
See the section below on error handling for more information about pos-
sible errors and how to interpret them.
The ldap_delete_ext() and ldap_delete_ext_s() functions support LDAPv3
server controls and client controls.
10.14. Extended Operations
The ldap_extended_operation() and ldap_extended_operation_s() routines
allow extended LDAP operations to be passed to the server, providing a
general protocol extensibility mechanism.
int ldap_extended_operation(
LDAP *ld,
const char *requestoid,
struct berval *requestdata,
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LDAPControl **serverctrls,
LDAPControl **clientctrls,
int *msgidp
);
int ldap_extended_operation_s(
LDAP *ld,
const char *requestoid,
struct berval *requestdata,
LDAPControl **serverctrls,
LDAPControl **clientctrls,
char **retoidp,
struct berval **retdatap
);
Parameters are:
ld The session handle.
requestoid The dotted-OID text string naming the request.
requestdata The arbitrary data required by the operation (if NULL, no
data is sent to the server).
serverctrls List of LDAP server controls.
clientctrls List of client controls.
msgidp This result parameter will be set to the message id of the
request if the ldap_extended_operation() call succeeds.
retoidp Pointer to a character string that will be set to an allo-
cated, dotted-OID text string returned by the server. This
string should be disposed of using the ldap_memfree() func-
tion. If no OID was returned, *retoidp is set to NULL.
retdatap Pointer to a berval structure pointer that will be set an
allocated copy of the data returned by the server. This
struct berval should be disposed of using ber_bvfree(). If
no data is returned, *retdatap is set to NULL.
The ldap_extended_operation() function initiates an asynchronous
extended operation and returns the constant LDAP_SUCCESS if the request
was successfully sent, or another LDAP error code if not. See the sec-
tion below on error handling for more information about possible errors
and how to interpret them. If successful, ldap_extended_operation()
places the message id of the request in *msgidp. A subsequent call to
ldap_result(), described below, can be used to obtain the result of the
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extended operation which can be passed to ldap_parse_extended_result()
to obtain the OID and data contained in the response.
The synchronous ldap_extended_operation_s() function returns the result
of the operation, either the constant LDAP_SUCCESS if the operation was
successful, or another LDAP error code if it was not. See the section
below on error handling for more information about possible errors and
how to interpret them. The retoid and retdata parameters are filled in
with the OID and data from the response. If no OID or data was
returned, these parameters are set to NULL.
The ldap_extended_operation() and ldap_extended_operation_s() functions
both support LDAPv3 server controls and client controls.
11. Abandoning An Operation
The following calls are used to abandon an operation in progress:
int ldap_abandon_ext(
LDAP *ld,
int msgid,
LDAPControl **serverctrls,
LDAPControl **clientctrls
);
int ldap_abandon(
LDAP *ld,
int msgid
);
ld The session handle.
msgid The message id of the request to be abandoned.
serverctrls List of LDAP server controls.
clientctrls List of client controls.
ldap_abandon_ext() abandons the operation with message id msgid and
returns the constant LDAP_SUCCESS if the abandon was successful or
another LDAP error code if not. See the section below on error handling
for more information about possible errors and how to interpret them.
ldap_abandon() is identical to ldap_abandon_ext() except that it does
not accept client or server controls and it returns zero if the abandon
was successful, -1 otherwise.
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After a successful call to ldap_abandon() or ldap_abandon_ext(), results
with the given message id are never returned from a subsequent call to
ldap_result(). There is no server response to LDAP abandon operations.
12. Obtaining Results and Peeking Inside LDAP Messages
ldap_result() is used to obtain the result of a previous asynchronously
initiated operation. Note that depending on how it is called,
ldap_result() may actually return a list or "chain" of result messages.
The ldap_result() function only returns messages for a single request,
so for all LDAP operations other than search only one result message is
expected; that is, the only time the "result chain" may contain more
than one message is if results from a search operation are returned.
Once a chain of messages has been returned to the caller, it is no
longer tied in any caller-visible way to the LDAP request that produced
it. Therefore, a chain of messages returned by calling ldap_result() or
by calling a synchronous search routine will never be affected by subse-
quent LDAP API calls (except for ldap_msgfree() which is used to dispose
of a chain of messages).
ldap_msgfree() frees the result messages (possibly an entire chain of
messages) obtained from a previous call to ldap_result() or from a call
to a synchronous search routine.
ldap_msgtype() returns the type of an LDAP message. ldap_msgid()
returns the message ID of an LDAP message.
int ldap_result(
LDAP *ld,
int msgid,
int all,
struct timeval *timeout,
LDAPMessage **res
);
int ldap_msgfree( LDAPMessage *res );
int ldap_msgtype( LDAPMessage *res );
int ldap_msgid( LDAPMessage *res );
Parameters are:
ld The session handle.
msgid The message id of the operation whose results are to be
returned, or the constant LDAP_RES_ANY (-1) if any result is
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desired.
all Specifies how many messages will be retrieved in a single call
to ldap_result(). This parameter only has meaning for search
results. Pass the constant LDAP_MSG_ONE (0x00) to retrieve one
message at a time. Pass LDAP_MSG_ALL (0x01) to request that
all results of a search be received before returning all
results in a single chain. Pass LDAP_MSG_RECEIVED (0x02) to
indicate that all messages retrieved so far should be returned
in the result chain.
timeout A timeout specifying how long to wait for results to be
returned. A NULL value causes ldap_result() to block until
results are available. A timeout value of zero seconds speci-
fies a polling behavior.
res For ldap_result(), a result parameter that will contain the
result(s) of the operation. If no results are returned, *res is
set to NULL. For ldap_msgfree(), the result chain to be freed,
obtained from a previous call to ldap_result(),
ldap_search_s(), or ldap_search_st(). If res is NULL, nothing
is done and ldap_msgfree() returns zero.
Upon successful completion, ldap_result() returns the type of the first
result returned in the res parameter. This will be one of the following
constants.
LDAP_RES_BIND (0x61)
LDAP_RES_SEARCH_ENTRY (0x64)
LDAP_RES_SEARCH_REFERENCE (0x73) -- new in LDAPv3
LDAP_RES_SEARCH_RESULT (0x65)
LDAP_RES_MODIFY (0x67)
LDAP_RES_ADD (0x69)
LDAP_RES_DELETE (0x6B)
LDAP_RES_MODDN (0x6D)
LDAP_RES_COMPARE (0x6F)
LDAP_RES_EXTENDED (0x78) -- new in LDAPv3
ldap_result() returns 0 if the timeout expired and -1 if an error
occurs, in which case the error parameters of the LDAP session handle
will be set accordingly.
ldap_msgfree() frees the result structure pointed to by res and returns
the type of the message it freed. If res is NULL, nothing is done and
the value zero is returned.
ldap_msgtype() returns the type of the LDAP message it is passed as a
parameter. The type will be one of the types listed above, or -1 on
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error.
ldap_msgid() returns the message ID associated with the LDAP message
passed as a parameter.
13. Handling Errors and Parsing Results
The following calls are used to extract information from results and
handle errors returned by other LDAP API routines. Note that
ldap_parse_sasl_bind_result() and ldap_parse_extended_result() must typ-
ically be used in addition to ldap_parse_result() to retrieve all the
result information from SASL Bind and Extended Operations respectively.
int ldap_parse_result(
LDAP *ld,
LDAPMessage *res,
int *errcodep,
char **matcheddnp,
char **errmsgp,
char ***referralsp,
LDAPControl ***serverctrlsp,
int freeit
);
int ldap_parse_sasl_bind_result(
LDAP *ld,
LDAPMessage *res,
struct berval **servercredp,
int freeit
);
int ldap_parse_extended_result(
LDAP *ld,
LDAPMessage *res,
char **retoidp,
struct berval **retdatap,
int freeit
);
char *ldap_err2string( int err );
The use of the following routines is deprecated.
int ldap_result2error(
LDAP *ld,
LDAPMessage *res,
int freeit
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);
void ldap_perror( LDAP *ld, const char *msg );
Parameters are:
ld The session handle.
res The result of an LDAP operation as returned by
ldap_result() or one of the synchronous API operation
calls.
errcodep This result parameter will be filled in with the LDAP error
code field from the LDAPMessage message. This is the indi-
cation from the server of the outcome of the operation.
NULL may be passed to ignore this field.
matcheddnp In the case of a return of LDAP_NO_SUCH_OBJECT, this result
parameter will be filled in with a DN indicating how much
of the name in the request was recognized. NULL may be
passed to ignore this field. The matched DN string should
be freed by calling ldap_memfree() which is described later
in this document.
errmsgp This result parameter will be filled in with the contents
of the error message field from the LDAPMessage message.
The error message string should be freed by calling
ldap_memfree() which is described later in this document.
NULL may be passed to ignore this field.
referralsp This result parameter will be filled in with the contents
of the referrals field from the LDAPMessage message, indi-
cating zero or more alternate LDAP servers where the
request should be retried. The referrals array should be
freed by calling ldap_value_free() which is described later
in this document. NULL may be passed to ignore this field.
serverctrlsp This result parameter will be filled in with an allocated
array of controls copied out of the LDAPMessage message.
The control array should be freed by calling
ldap_controls_free() which was described earlier.
freeit A boolean that determines whether the res parameter is
disposed of or not. Pass any non-zero value to have these
routines free res after extracting the requested informa-
tion. This is provided as a convenience; you can also use
ldap_msgfree() to free the result later. If freeit is
non-zero, the entire chain of messages represented by res
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is disposed of.
servercredp For SASL bind results, this result parameter will be filled
in with the credentials passed back by the server for
mutual authentication, if given. An allocated berval struc-
ture is returned that should be disposed of by calling
ber_bvfree(). NULL may be passed to ignore this field.
retoidp For extended results, this result parameter will be filled
in with the dotted-OID text representation of the name of
the extended operation response. This string should be
disposed of by calling ldap_memfree(). NULL may be passed
to ignore this field.
retdatap For extended results, this result parameter will be filled
in with a pointer to a struct berval containing the data in
the extended operation response. It should be disposed of
by calling ber_bvfree(). NULL may be passed to ignore this
field.
err For ldap_err2string(), an LDAP error code, as returned by
ldap_parse_result() or another LDAP API call.
Additional parameters for the deprecated routines are not described.
Interested readers are referred to RFC 1823.
All three of the ldap_parse_*_result() routines skip over messages of
type LDAP_RES_SEARCH_ENTRY and LDAP_RES_SEARCH_REFERENCE when looking
for a result message to parse. They return the constant LDAP_SUCCESS if
the result was successfully parsed and another LDAP error code if not.
Note that the LDAP error code that indicates the outcome of the opera-
tion performed by the server is placed in the errcodep
ldap_parse_result() parameter. If a chain of messages that contains
more than one result message is passed to these routines they always
operate on the first result in the chain.
ldap_err2string() is used to convert a numeric LDAP error code, as
returned by one of the three ldap_parse_*_result() routines, or one of
the synchronous API operation calls, into an informative zero-terminated
character string message describing the error. It returns a pointer to
static data.
14. Stepping Through a List of Results
The ldap_first_message() and ldap_next_message() routines are used to
step through the list of messages in a result chain returned by
ldap_result(). For search operations, the result chain may actually
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include referral messages, entry messages, and result messages.
ldap_count_messages() is used to count the number of messages returned.
The ldap_msgtype() function, described above, can be used to distinguish
between the different message types.
LDAPMessage *ldap_first_message( LDAP *ld, LDAPMessage *res );
LDAPMessage *ldap_next_message( LDAP *ld, LDAPMessage *msg );
int ldap_count_messages( LDAP *ld, LDAPMessage *res );
Parameters are:
ld The session handle.
res The result chain, as obtained by a call to one of the synchronous
search routines or ldap_result().
msg The message returned by a previous call to ldap_first_message()
or ldap_next_message().
ldap_first_message() and ldap_next_message() will return NULL when no
more messages exist in the result set to be returned. NULL is also
returned if an error occurs while stepping through the entries, in which
case the error parameters in the session handle ld will be set to indi-
cate the error.
ldap_count_messages() returns the number of messages contained in a
chain of results. It can also be used to count the number of messages
that remain in a chain if called with a message, entry, or reference
returned by ldap_first_message(), ldap_next_message(),
ldap_first_entry(), ldap_next_entry(), ldap_first_reference(),
ldap_next_reference().
15. Parsing Search Results
The following calls are used to parse the entries and references
returned by ldap_search() and friends. These results are returned in an
opaque structure that should only be accessed by calling the routines
described below. Routines are provided to step through the entries and
references returned, step through the attributes of an entry, retrieve
the name of an entry, and retrieve the values associated with a given
attribute in an entry.
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15.1. Stepping Through a List of Entries or References
The ldap_first_entry() and ldap_next_entry() routines are used to step
through and retrieve the list of entries from a search result chain.
The ldap_first_reference() and ldap_next_reference() routines are used
to step through and retrieve the list of continuation references from a
search result chain. ldap_count_entries() is used to count the number
of entries returned. ldap_count_references() is used to count the number
of references returned.
LDAPMessage *ldap_first_entry( LDAP *ld, LDAPMessage *res );
LDAPMessage *ldap_next_entry( LDAP *ld, LDAPMessage *entry );
LDAPMessage *ldap_first_reference( LDAP *ld, LDAPMessage *res );
LDAPMessage *ldap_next_reference( LDAP *ld, LDAPMessage *ref );
int ldap_count_entries( LDAP *ld, LDAPMessage *res );
int ldap_count_references( LDAP *ld, LDAPMessage *res );
Parameters are:
ld The session handle.
res The search result, as obtained by a call to one of the synchro-
nous search routines or ldap_result().
entry The entry returned by a previous call to ldap_first_entry() or
ldap_next_entry().
ref The reference returned by a previous call to
ldap_first_reference() or ldap_next_reference().
ldap_first_entry(), ldap_next_entry(), ldap_first_reference() and
ldap_next_reference() all return NULL when no more entries or references
exist in the result set to be returned. NULL is also returned if an
error occurs while stepping through the entries or references, in which
case the error parameters in the session handle ld will be set to indi-
cate the error.
ldap_count_entries() returns the number of entries contained in a chain
of entries. It can also be used to count the number of entries that
remain in a chain if called with a message, entry or reference returned
by ldap_first_message(), ldap_next_message(), ldap_first_entry(),
ldap_next_entry(), ldap_first_reference(), ldap_next_reference().
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ldap_count_references() returns the number of references contained in a
chain of search results. It can also be used to count the number of
references that remain in a chain.
15.2. Stepping Through the Attributes of an Entry
The ldap_first_attribute() and ldap_next_attribute() calls are used to
step through the list of attribute types returned with an entry.
char *ldap_first_attribute(
LDAP *ld,
LDAPMessage *entry,
BerElement **ptr
);
char *ldap_next_attribute(
LDAP *ld,
LDAPMessage *entry,
BerElement *ptr
);
void ldap_memfree( char *mem );
Parameters are:
ld The session handle.
entry The entry whose attributes are to be stepped through, as returned
by ldap_first_entry() or ldap_next_entry().
ptr In ldap_first_attribute(), the address of a pointer used inter-
nally to keep track of the current position in the entry. In
ldap_next_attribute(), the pointer returned by a previous call to
ldap_first_attribute(). The BerElement type itself is an opaque
structure that is described in more detail later in this document
in the section "Encoded ASN.1 Value Manipulation".
mem A pointer to memory allocated by the LDAP library, such as the
attribute type names returned by ldap_first_attribute() and
ldap_next_attribute, or the DN returned by ldap_get_dn(). If mem
is NULL, nothing is done.
ldap_first_attribute() and ldap_next_attribute() will return NULL when
the end of the attributes is reached, or if there is an error, in which
case the error parameters in the session handle ld will be set to indi-
cate the error.
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Both routines return a pointer to an allocated buffer containing the
current attribute name. This should be freed when no longer in use by
calling ldap_memfree().
ldap_first_attribute() will allocate and return in ptr a pointer to a
BerElement used to keep track of the current position. This pointer
should be passed in subsequent calls to ldap_next_attribute() to step
through the entry's attributes. After a set of calls to
ldap_first_attribute() and ldap_next_attribute(), if ptr is non-NULL, it
should be freed by calling ber_free( ptr, 0 ). Note that it is very
important to pass the second parameter as 0 (zero) in this call, since
the buffer associated with the BerElement does not point to separately
allocated memory.
The attribute type names returned are suitable for passing in a call to
ldap_get_values() and friends to retrieve the associated values.
15.3. Retrieving the Values of an Attribute
ldap_get_values() and ldap_get_values_len() are used to retrieve the
values of a given attribute from an entry. ldap_count_values() and
ldap_count_values_len() are used to count the returned values.
ldap_value_free() and ldap_value_free_len() are used to free the values.
char **ldap_get_values(
LDAP *ld,
LDAPMessage *entry,
const char *attr
);
struct berval **ldap_get_values_len(
LDAP *ld,
LDAPMessage *entry,
const char *attr
);
int ldap_count_values( char **vals );
int ldap_count_values_len( struct berval **vals );
void ldap_value_free( char **vals );
void ldap_value_free_len( struct berval **vals );
Parameters are:
ld The session handle.
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entry The entry from which to retrieve values, as returned by
ldap_first_entry() or ldap_next_entry().
attr The attribute whose values are to be retrieved, as returned by
ldap_first_attribute() or ldap_next_attribute(), or a caller-
supplied string (e.g., "mail").
vals The values returned by a previous call to ldap_get_values() or
ldap_get_values_len().
Two forms of the various calls are provided. The first form is only
suitable for use with non-binary character string data. The second _len
form is used with any kind of data.
ldap_get_values() and ldap_get_values_len() return NULL if no values are
found for attr or if an error occurs.
ldap_count_values() and ldap_count_values_len() return -1 if an error
occurs such as the vals parameter being invalid.
Note that the values returned are dynamically allocated and should be
freed by calling either ldap_value_free() or ldap_value_free_len() when
no longer in use.
15.4. Retrieving the name of an entry
ldap_get_dn() is used to retrieve the name of an entry.
ldap_explode_dn() and ldap_explode_rdn() are used to break up a name
into its component parts. ldap_dn2ufn() is used to convert the name into
a more "user friendly" format.
char *ldap_get_dn( LDAP *ld, LDAPMessage *entry );
char **ldap_explode_dn( const char *dn, int notypes );
char **ldap_explode_rdn( const char *rdn, int notypes );
char *ldap_dn2ufn( const char *dn );
Parameters are:
ld The session handle.
entry The entry whose name is to be retrieved, as returned by
ldap_first_entry() or ldap_next_entry().
dn The dn to explode, such as returned by ldap_get_dn().
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rdn The rdn to explode, such as returned in the components of the
array returned by ldap_explode_dn().
notypes A boolean parameter, if non-zero indicating that the dn or rdn
components should have their type information stripped off
(i.e., "cn=Babs" would become "Babs").
ldap_get_dn() will return NULL if there is some error parsing the dn,
setting error parameters in the session handle ld to indicate the error.
It returns a pointer to newly allocated space that the caller should
free by calling ldap_memfree() when it is no longer in use. Note the
format of the DNs returned is given by [4].
ldap_explode_dn() returns a NULL-terminated char * array containing the
RDN components of the DN supplied, with or without types as indicated by
the notypes parameter. The components are returned in the order they
appear in the dn. The array returned should be freed when it is no
longer in use by calling ldap_value_free().
ldap_explode_rdn() returns a NULL-terminated char * array containing the
components of the RDN supplied, with or without types as indicated by
the notypes parameter. The components are returned in the order they
appear in the rdn. The array returned should be freed when it is no
longer in use by calling ldap_value_free().
ldap_dn2ufn() converts the DN into the user friendly format described in
[5]. The UFN returned is newly allocated space that should be freed by a
call to ldap_memfree() when no longer in use.
15.5. Retrieving controls from an entry
ldap_get_entry_controls() is used to extract LDAP controls from an
entry.
int ldap_get_entry_controls(
LDAP *ld,
LDAPMessage *entry,
LDAPControl ***serverctrlsp
);
Parameters are:
ld The session handle.
entry The entry to extract controls from, as returned by
ldap_first_entry() or ldap_next_entry().
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serverctrlsp This result parameter will be filled in with an allocated
array of controls copied out of entry. The control array
should be freed by calling ldap_controls_free(). If ser-
verctrlsp is NULL, no controls are returned.
ldap_get_entry_controls() returns an LDAP error code that indicates
whether the reference could be successfully parsed (LDAP_SUCCESS if all
goes well).
15.6. Parsing References
ldap_parse_reference() is used to extract referrals and controls from a
SearchResultReference message.
int ldap_parse_reference(
LDAP *ld,
LDAPMessage *ref,
char ***referralsp,
LDAPControl ***serverctrlsp,
int freeit
);
Parameters are:
ld The session handle.
ref The reference to parse, as returned by ldap_result(),
ldap_first_reference(), or ldap_next_reference().
referralsp This result parameter will be filled in with an allocated
array of character strings. The elements of the array are
the referrals (typically LDAP URLs) contained in ref. The
array should be freed when no longer in used by calling
ldap_value_free(). If referralsp is NULL, the referral
URLs are not returned.
serverctrlsp This result parameter will be filled in with an allocated
array of controls copied out of ref. The control array
should be freed by calling ldap_controls_free(). If ser-
verctrlsp is NULL, no controls are returned.
freeit A boolean that determines whether the ref parameter is
disposed of or not. Pass any non-zero value to have this
routine free ref after extracting the requested informa-
tion. This is provided as a convenience; you can also use
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ldap_msgfree() to free the result later.
ldap_parse_reference() returns an LDAP error code that indicates whether
the reference could be successfully parsed (LDAP_SUCCESS if all goes
well).
16. Encoded ASN.1 Value Manipulation
This section describes routines which may be used to encode and decode
BER-encoded ASN.1 values, which are often used inside of control and
extension values.
With the exceptions of two new functions ber_flatten() and ber_init(),
these functions are compatible with the University of Michigan LDAP 3.3
implementation of BER.
16.1. General
struct berval {
ber_len_t bv_len;
char *bv_val;
};
As defined earlier in the section "Common Data Structures", a struct
berval contains an arbitrary sequence of bytes and an indication of its
length. The bv_len element is an unsigned integer. The bv_val is not
necessarily zero-terminated. Applications may allocate their own berval
structures.
As defined earlier in the section "Common Data Structures", the BerEle-
ment structure is an opaque structure:
typedef struct berelement BerElement;
It contains not only a copy of the encoded value, but also state infor-
mation used in encoding or decoding. Applications cannot allocate their
own BerElement structures. The internal state is neither thread-
specific nor locked, so two threads should not manipulate the same
BerElement value simultaneously.
A single BerElement value cannot be used for both encoding and decoding.
void ber_bvfree( struct berval *bv );
ber_bvfree() frees a berval returned from this API. Both the bv->bv_val
string and the berval itself are freed. Applications should not use
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ber_bvfree() with bervals which the application has allocated.
void ber_bvecfree( struct berval **bv );
ber_bvecfree() frees an array of bervals returned from this API. Each
of the bervals in the array are freed using ber_bvfree(), then the array
itself is freed.
struct berval *ber_bvdup( const struct berval *bv );
ber_bvdup() returns a copy of a berval. The bv_val field in the
returned berval points to a different area of memory than the bv_val
field in the argument berval. The NULL pointer is returned on error
(e.g. out of memory).
void ber_free( BerElement *ber, int fbuf );
ber_free() frees a BerElement which is returned from the API calls
ber_alloc_t() or ber_init(). Each BerElement must be freed by the
caller. The second argument fbuf should always be set to 1 to ensure
that the internal buffer used by the BER functions is freed as well as
the BerElement container itself.
16.2. Encoding
BerElement *ber_alloc_t( int options );
ber_alloc_t() constructs and returns BerElement. The NULL pointer is
returned on error. The options field contains a bitwise-or of options
which are to be used when generating the encoding of this BerElement.
One option is defined and must always be supplied:
#define LBER_USE_DER 0x01
When this option is present, lengths will always be encoded in the
minimum number of octets. Note that this option does not cause values
of sets to be rearranged in tag and byte order or default values to be
removed, so these functions are not sufficient for generating DER output
as defined in X.509 and X.680. If the caller takes responsibility for
ordering values of sets correctly and removing default values, DER out-
put as defined in X.509 and X.680 can be produced.
Unrecognized option bits are ignored.
The BerElement returned by ber_alloc_t() is initially empty. Calls to
ber_printf() will append bytes to the end of the ber_alloc_t().
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int ber_printf( BerElement *ber, const char *fmt, ... )
The ber_printf() routine is used to encode a BER element in much the
same way that sprintf() works. One important difference, though, is
that state information is kept in the ber argument so that multiple
calls can be made to ber_printf() to append to the end of the BER ele-
ment. ber must be a pointer to a BerElement returned by ber_alloc_t().
ber_printf() interprets and formats its arguments according to the for-
mat string fmt. ber_printf() returns -1 if there is an error during
encoding and a positive number if successful. As with sprintf(), each
character in fmt refers to an argument to ber_printf().
The format string can contain the following format characters:
't' Tag. The next argument is a ber_tag_t specifying the tag to
override the next element to be written to the ber. This works
across calls. The integer tag value must contain the tag class,
constructed bit, and tag value. For example, a tag of "[3]" for
a constructed type is 0xA3. All implementations must support
tags that fit in a single octet (i.e., where the tag value is
less than 32) and they may support larger tags.
'b' Boolean. The next argument is an int, containing either 0 for
FALSE or 0xff for TRUE. A boolean element is output. If this
format character is not preceded by the 't' format modifier, the
tag 0x01 is used for the element.
'i' Integer. The next argument is an int, containing the integer in
the host's byte order. An integer element is output. If this
format character is not preceded by the 't' format modifier, the
tag 0x02 is used for the element.
'X' Bitstring. The next two arguments are a char * pointer to the
start of the bitstring, followed by an int containing the number
of bits in the bitstring. A bitstring element is output, in
primitive form. If this format character is not preceded by the
't' format modifier, the tag 0x03 is used for the element.
'n' Null. No argument is required. An ASN.1 NULL element is out-
put. If this format character is not preceded by the 't' format
modifier, the tag 0x05 is used for the element.
'o' Octet string. The next two arguments are a char *, followed by
an int with the length of the string. The string may contain
null bytes and need not be zero-terminated. An octet string
element is output, in primitive form. If this format character
is not preceded by the 't' format modifier, the tag 0x04 is used
for the element.
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's' Octet string. The next argument is a char * pointing to a
zero-terminated string. An octet string element in primitive
form is output, which does not include the trailing '\0' (null)
byte. If this format character is not preceded by the 't' format
modifier, the tag 0x04 is used for the element.
'v' Several octet strings. The next argument is a char **, an array
of char * pointers to zero-terminated strings. The last element
in the array must be a NULL pointer. The octet strings do not
include the trailing '\0' (null) byte. Note that a construct
like '{v}' is required to get an actual SEQUENCE OF octet
strings. The 't' format modifier cannot be used with this for-
mat character.
'V' Several octet strings. A NULL-terminated array of berval *'s is
supplied. Note that a construct like '{V}' is required to get an
actual SEQUENCE OF octet strings. The 't' format modifier cannot
be used with this format character.
'{' Begin sequence. No argument is required. If this format char-
acter is not preceded by the 't' format modifier, the tag 0x30
is used.
'}' End sequence. No argument is required. The 't' format modifier
cannot be used with this format character.
'[' Begin set. No argument is required. If this format character
is not preceded by the 't' format modifier, the tag 0x31 is
used.
']' End set. No argument is required. The 't' format modifier can-
not be used with this format character.
Each use of a '{' format character must be matched by a '}' character,
either later in the format string, or in the format string of a subse-
quent call to ber_printf() for that BerElement. The same applies to the
'[' and ']' format characters.
Sequences and sets nest, and implementations of this API must maintain
internal state to be able to properly calculate the lengths.
int ber_flatten( const BerElement *ber, struct berval **bvPtr );
The ber_flatten routine allocates a struct berval whose contents are a
BER encoding taken from the ber argument. The bvPtr pointer points to
the returned berval, which must be freed using ber_bvfree(). This rou-
tine returns 0 on success and -1 on error.
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The ber_flatten API call is not present in U-M LDAP 3.3.
The use of ber_flatten on a BerElement in which all '{' and '}' format
modifiers have not been properly matched is an error (i.e., -1 will be
returned by ber_flatten() if this situation is exists).
16.3. Encoding Example
The following is an example of encoding the following ASN.1 data type:
Example1Request ::= SEQUENCE {
s OCTET STRING, -- must be printable
val1 INTEGER,
val2 [0] INTEGER DEFAULT 0
}
int encode_example1(const char *s,int val1,int val2,struct berval **bvPtr)
{
BerElement *ber;
int rc = -1;
ber = ber_alloc_t(LBER_USE_DER);
if (ber == NULL) return -1;
if (ber_printf(ber,"{si",s,val1) == -1) {
goto done;
}
if (val2 != 0) {
if (ber_printf(ber,"ti",0x80,val2) == -1) {
goto done;
}
}
if (ber_printf(ber,"}") == -1) {
goto done;
}
rc = ber_flatten(ber,bvPtr);
done:
ber_free(ber,1);
return rc;
}
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16.4. Decoding
The following two symbols are available to applications.
#define LBER_ERROR (ber_tag_t)0xffffffff
#define LBER_DEFAULT (ber_tag_t)0xffffffff
BerElement *ber_init( const struct berval *bv );
The ber_init function constructs a BerElement and returns a new BerEle-
ment containing a copy of the data in the bv argument. ber_init returns
the NULL pointer on error.
ber_tag_t ber_scanf( BerElement *ber, const char *fmt, ... );
The ber_scanf() routine is used to decode a BER element in much the same
way that sscanf() works. One important difference, though, is that some
state information is kept with the ber argument so that multiple calls
can be made to ber_scanf() to sequentially read from the BER element.
The ber argument must be a pointer to a BerElement returned by
ber_init(). ber_scanf interprets the bytes according to the format
string fmt, and stores the results in its additional arguments.
ber_scanf() returns LBER_ERROR on error, and a different value on suc-
cess.
The format string contains conversion specifications which are used to
direct the interpretation of the BER element. The format string can
contain the following characters:
'a' Octet string. A char ** argument should be supplied. Memory is
allocated, filled with the contents of the octet string, zero-
terminated, and the pointer to the string is stored in the argu-
ment. The returned value must be freed using ldap_memfree. The
tag of the element must indicate the primitive form (constructed
strings are not supported) but is otherwise ignored and dis-
carded during the decoding. This format cannot be used with
octet strings which could contain null bytes.
'O' Octet string. A struct berval ** argument should be supplied,
which upon return points to an allocated struct berval contain-
ing the octet string and its length. ber_bvfree() must be
called to free the allocated memory. The tag of the element
must indicate the primitive form (constructed strings are not
supported) but is otherwise ignored during the decoding.
'b' Boolean. A pointer to an int should be supplied. The int value
stored will be 0 for FALSE or nonzero for TRUE. The tag of the
element must indicate the primitive form but is otherwise
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ignored during the decoding.
'i' Integer. A pointer to an int should be supplied. The int value
stored will be in host byte order. The tag of the element must
indicate the primitive form but is otherwise ignored during the
decoding. ber_scanf() will return an error if the integer can-
not be stored in an int.
'B' Bitstring. A char ** argument should be supplied which will
point to the allocated bits, followed by a ber_len_t * argument,
which will point to the length (in bits) of the bitstring
returned. ldap_memfree must be called to free the bitstring.
The tag of the element must indicate the primitive form (con-
structed bitstrings are not supported) but is otherwise ignored
during the decoding.
'n' Null. No argument is required. The element is verified to have
a zero-length value and is skipped. The tag is ignored.
'v' Several octet strings. A char *** argument should be supplied,
which upon return points to an allocated NULL-terminated array
of char *'s containing the octet strings. NULL is stored if the
sequence is empty. ldap_memfree must be called to free each
element of the array and the array itself. The tag of the
sequence and of the octet strings are ignored.
'V' Several octet strings (which could contain null bytes). A
struct berval *** should be supplied, which upon return points
to a allocated NULL-terminated array of struct berval *'s con-
taining the octet strings and their lengths. NULL is stored if
the sequence is empty. ber_bvecfree() can be called to free the
allocated memory. The tag of the sequence and of the octet
strings are ignored.
'x' Skip element. The next element is skipped. No argument is
required.
'{' Begin sequence. No argument is required. The initial sequence
tag and length are skipped.
'}' End sequence. No argument is required.
'[' Begin set. No argument is required. The initial set tag and
length are skipped.
']' End set. No argument is required.
ber_tag_t ber_peek_tag( const BerElement *ber,
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ber_len_t *lenPtr );
ber_peek_tag() returns the tag of the next element to be parsed in the
BerElement argument. The length of this element is stored in the
*lenPtr argument. LBER_DEFAULT is returned if there is no further data
to be read. The ber argument is not modified.
ber_tag_t ber_skip_tag( BerElement *ber, ber_len_t *lenPtr );
ber_skip_tag() is similar to ber_peek_tag(), except that the state
pointer in the BerElement argument is advanced past the first tag and
length, and is pointed to the value part of the next element. This rou-
tine should only be used with constructed types and situations when a
BER encoding is used as the value of an OCTET STRING. The length of the
value is stored in *lenPtr.
ber_tag_t ber_first_element( BerElement *ber,
ber_len_t *lenPtr, char **opaquePtr );
ber_tag_t ber_next_element( BerElement *ber,
ber_len_t *lenPtr, char *opaque );
ber_first_element() and ber_next_element() are used to traverse a SET,
SET OF, SEQUENCE or SEQUENCE OF data value. ber_first_element() calls
ber_skip_tag(), stores internal information in *lenPtr and *opaquePtr,
and calls ber_peek_tag() for the first element inside the constructed
value. LBER_DEFAULT is returned if the constructed value is empty.
ber_next_element() positions the state at the start of the next element
in the constructed type. LBER_DEFAULT is returned if there are no
further values.
The len and opaque values should not be used by applications other than
as arguments to ber_next_element(), as shown in the example below.
16.5. Decoding Example
The following is an example of decoding an ASN.1 data type:
Example2Request ::= SEQUENCE {
dn OCTET STRING, -- must be printable
scope ENUMERATED { b (0), s (1), w (2) },
ali ENUMERATED { n (0), s (1), f (2), a (3) },
size INTEGER,
time INTEGER,
tonly BOOLEAN,
attrs SEQUENCE OF OCTET STRING, -- must be printable
[0] SEQUENCE OF SEQUENCE {
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type OCTET STRING -- must be printable,
crit BOOLEAN DEFAULT FALSE,
value OCTET STRING
} OPTIONAL }
#define TAG_CONTROL_LIST 0xA0L /* context specific cons 0 */
int decode_example2(struct berval *bv)
{
BerElement *ber;
ber_len_t len;
ber_tag_t res;
int scope, ali, size, time, tonly;
char *dn = NULL, **attrs = NULL;
int i,rc = 0;
ber = ber_init(bv);
if (ber == NULL) {
fputs("ERROR ber_init failed\n", stderr);
return -1;
}
res = ber_scanf(ber,"{aiiiib{v}",&dn,&scope,&ali,
&size,&time,&tonly,&attrs);
if (res == LBER_ERROR) {
fputs("ERROR ber_scanf failed\n", stderr);
ber_free(ber,1);
return -1;
}
/* *** use dn */
ldap_memfree(dn);
for (i = 0; attrs != NULL && attrs[i] != NULL; i++) {
/* *** use attrs[i] */
ldap_memfree(attrs[i]);
}
ldap_memfree(attrs);
if (ber_peek_tag(ber,&len) == TAG_CONTROL_LIST) {
char *opaque;
ber_tag_t tag;
for (tag = ber_first_element(ber,&len,&opaque);
tag != LBER_DEFAULT;
tag = ber_next_element (ber,&len,opaque)) {
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ber_len_t tlen;
ber_tag_t ttag;
char *type;
int crit;
struct berval *value;
if (ber_scanf(ber,"{a",&type) == LBER_ERROR) {
fputs("ERROR cannot parse type\n", stderr);
break;
}
/* *** use type */
ldap_memfree(type);
ttag = ber_peek_tag(ber,&tlen);
if (ttag == 0x01) { /* boolean */
if (ber_scanf(ber,"b",
&crit) == LBER_ERROR) {
fputs("ERROR cannot parse crit\n",
stderr);
rc = -1;
break;
}
} else if (ttag == 0x04) { /* octet string */
crit = 0;
} else {
fputs("ERROR extra field in controls\n",
stderr );
break;
}
if (ber_scanf(ber,"O}",&value) == LBER_ERROR) {
fputs("ERROR cannot parse value\n", stderr);
rc = -1;
break;
}
/* *** use value */
ber_bvfree(value);
}
}
ber_scanf(ber,"}");
ber_free(ber,1);
return rc;
}
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17. Security Considerations
LDAPv2 supports security through protocol-level authentication using
clear-text passwords. LDAPv3 adds support for SASL [8] (Simple Authen-
tication Security Layer) methods. LDAPv3 also supports operation over a
secure transport layer using Transport Layer Security TLS [9]. Readers
are referred to the protocol documents for discussion of related secu-
rity considerations.
Implementations of this API should be cautious when handling authentica-
tion credentials. In particular, keeping long-lived copies of creden-
tials without the application's knowledge is discouraged.
18. Acknowledgements
Many members of the IETF ASID and LDAPEXT working groups as well as
members of the Internet at large have provided useful comments and
suggestions that have been incorporated into this document. Chris
Weider deserves special mention for his contributions as co-author of
earlier revisions of this document.
The original material upon which this specification is based was sup-
ported by the National Science Foundation under Grant No. NCR-9416667.
19. Copyright
Copyright (C) The Internet Society (1997-1999). All Rights Reserved.
This document and translations of it may be copied and furnished to oth-
ers, and derivative works that comment on or otherwise explain it or
assist in its implementation may be prepared, copied, published and dis-
tributed, in whole or in part, without restriction of any kind, provided
that the above copyright notice and this paragraph are included on all
such copies and derivative works. However, this document itself may not
be modified in any way, such as by removing the copyright notice or
references to the Internet Society or other Internet organizations,
except as needed for the purpose of developing Internet standards in
which case the procedures for copyrights defined in the Internet Stan-
dards process must be followed, or as required to translate it into
languages other than English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an "AS
IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK
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FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT
LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT
INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FIT-
NESS FOR A PARTICULAR PURPOSE.
20. Bibliography
[1] The Directory: Selected Attribute Syntaxes. CCITT, Recommendation
X.520.
[2] M. Wahl, A. Coulbeck, T. Howes, S. Kille, W. Yeong, C. Robbins,
"Lightweight Directory Access Protocol (v3): Attribute Syntax
Definitions", RFC 2252, December 1997.
[3] T. Howes, "The String Representation of LDAP Search Filters," RFC
2254, December 1997.
[4] M. Wahl, S. Kille, T. Howes, "Lightweight Directory Access Protocol
(v3): A UTF-8 String Representation of Distinguished Names", RFC
2253, December 1997.
[5] S. Kille, "Using the OSI Directory to Achieve User Friendly Nam-
ing," RFC 1781, March 1995.
[6] M. Wahl, T. Howes, S. Kille, "Lightweight Directory Access Protocol
(v3)", RFC 2251, December 1997.
[7] A. Herron, T. Howes, M. Wahl, C. Weider, A. Anantha, "LDAP Control
Extension for Server Side Sorting of Search Results", INTERNET-
DRAFT <draft-ietf-ldapext-sorting-01.txt>, 7 August 1998.
[8] J. Meyers, "Simple Authentication and Security Layer (SASL)", RFC
2222, October 1997.
[9] "Lightweight Directory Access Protocol (v3): Extension for Tran-
sport Layer Security", INTERNET-DRAFT <draft-ietf-ldapext-ldapv3-
tls-04.txt>, November 1998.
[10] "UTF-8, a transformation format of Unicode and ISO 10646", RFC
2044, October 1996.
[11] "IP Version 6 Addressing Architecture,", RFC 1884, December 1995.
[12] "Character Mnemonics and Character Sets," RFC 1345, June 1992.
[13] "Programming Languages - C", ANSI/ISO Standard 9899, revised 1997.
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21. Authors' Addresses
Mark Smith (document editor)
Netscape Communications Corp.
501 E. Middlefield Rd., Mailstop MV068
Mountain View, CA 94043
USA
+1 650 937-3477
mcs@netscape.com
Tim Howes
Netscape Communications Corp.
501 E. Middlefield Rd., Mailstop MV068
Mountain View, CA 94043
USA
+1 650 937-3419
howes@netscape.com
Andy Herron
Microsoft Corp.
1 Microsoft Way
Redmond, WA 98052
USA
+1 425 882-8080
andyhe@microsoft.com
Mark Wahl
Innosoft International, Inc.
8911 Capital of Texas Hwy, Suite 4140
Austin, TX 78759
USA
+1 626 919 3600
Mark.Wahl@innosoft.com
Anoop Anantha
Microsoft Corp.
1 Microsoft Way
Redmond, WA 98052
USA
+1 425 882-8080
anoopa@microsoft.com
22. Appendix A - Sample C LDAP API Code
#include <stdio.h>
#include <ldap.h>
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main()
{
LDAP *ld;
LDAPMessage *res, *e;
int i, rc;
char *a, *dn;
BerElement *ptr;
char **vals;
/* open an LDAP session */
if ( (ld = ldap_init( "dotted.host.name", LDAP_PORT )) == NULL )
return 1;
/* authenticate as nobody */
if (( rc = ldap_simple_bind_s( ld, NULL, NULL )) != LDAP_SUCCESS ) {
fprintf( stderr, "ldap_simple_bind_s: %s\n",
ldap_err2string( rc ));
ldap_unbind( ld );
return 1;
}
/* search for entries with cn of "Babs Jensen", return all attrs */
if (( rc = ldap_search_s( ld, "o=University of Michigan, c=US",
LDAP_SCOPE_SUBTREE, "(cn=Babs Jensen)", NULL, 0, &res ))
!= LDAP_SUCCESS ) {
fprintf( stderr, "ldap_search_s: %s\n",
ldap_err2string( rc ));
if ( res == NULL ) {
ldap_unbind( ld );
return 1;
}
}
/* step through each entry returned */
for ( e = ldap_first_entry( ld, res ); e != NULL;
e = ldap_next_entry( ld, e ) ) {
/* print its name */
dn = ldap_get_dn( ld, e );
printf( "dn: %s\n", dn );
ldap_memfree( dn );
/* print each attribute */
for ( a = ldap_first_attribute( ld, e, &ptr ); a != NULL;
a = ldap_next_attribute( ld, e, ptr ) ) {
printf( "\tattribute: %s\n", a );
/* print each value */
vals = ldap_get_values( ld, e, a );
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for ( i = 0; vals[i] != NULL; i++ ) {
printf( "\t\tvalue: %s\n", vals[i] );
}
ldap_value_free( vals );
ldap_memfree( a );
}
if ( ptr != NULL ) {
ber_free( ptr, 0 );
}
}
/* free the search results */
ldap_msgfree( res );
/* close and free connection resources */
ldap_unbind( ld );
return 0;
}
23. Appendix B - Namespace Consumed By This Specification
The following 2 prefixes are used in this specification to name func-
tions:
ldap_
ber_
The following 6 prefixes are used in this specification to name struc-
tures, unions, and typedefs:
ldap
LDAP
PLDAP
ber
Ber
timeval
The following 3 prefixes are used in this specification to name #defined
macros:
LDAP
LBER_
mod_
24. Appendix C - Summary of Requirements for API Extensions
As the LDAP protocol is extended, this C LDAP API will need to be
extended as well. For example, an LDAPv3 control extension has already
been defined for server-side sorting of search results [7]. This
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appendix summarizes the requirements for extending this API.
24.1. Compatibility
Extensions to this document should not, by default, alter the behavior
of any of the APIs specified in this document. If an extension option-
ally changes the behavior of any existing C LDAP API function calls, the
behavior change must be well documented.
24.2. Style
Extensions to this API should follow the general style and naming con-
ventions used in this document. For example, function names should
start with "ldap_" or "ber_" and consist entirely of lowercase letters,
digits, and underscore ('_') characters. More information can be found
in the preceding appendix called "Namespace Consumed By This Specifica-
tion."
24.3. Dependence on Externally Defined Types
Extensions to this API should minimize dependencies on types and macros
that are defined in system header files and generally use only intrinsic
types that are part of the C language, types defined in this specifica-
tion, or types defined in the extension document itself.
24.4. Compile Time Information
Extensions to this API should conform to the requirements contained in
the "Retrieving Information at Compile Time" section of this document.
That is, extensions should define a macro of the form:
#define LDAP_API_FEATURE_x level
so that applications can detect the presence or absence of the extension
at compile time and also test the version or level of the extension pro-
vided by an API implementation.
24.5. Runtime Information
Extensions to this API should conform to the requirements contained in
the "Retrieving Information During Execution" section of this document.
That is, each extension should be given a character string name and that
name should appear in the ldapai_extensions array field of the LDAPAPI-
Info structure following a successful call to ldap_get_option() with an
option parameter value of LDAP_OPT_API_INFO. In addition, information
about the extension should be available via a call to ldap_get_option()
with an option parameter value of LDAP_OPT_API_FEATURE_INFO.
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24.6. Values Used for Session Handle Options
Extensions to this API that add new session options (for use with the
ldap_get_option() and ldap_set_option() functions) should meet the
requirements contained in the last paragraph of the "LDAP Session Handle
Options" section of this document. Specifically, standards track docu-
ments MUST use values for option macros that are between 0x1000 and
0x3FFF inclusive and private and experimental extensions MUST use values
for the option macros that are between 0x4000 and 0x7FFF inclusive.
25. Appendix D - Known Incompatibilities with RFC 1823
This appendix lists known incompatibilities between this API specifica-
tion and the one contained in RFC 1823, beyond the additional API func-
tions added in support of LDAPv3.
25.1. Opaque LDAP Structure
In RFC 1823, some fields in the LDAP structure were exposed to applica-
tion programmers. To provide a cleaner interface and to make it easier
for implementations to evolve over time without sacrificing binary com-
patibility with older applications, the LDAP structure is now entirely
opaque. The new ldap_set_option() and ldap_get_option() calls can be
used to manipulate per-session and global options.
25.2. Additional Error Codes
The following new error code macros were introduced to support LDAPv3:
LDAP_REFERRAL
LDAP_ADMINLIMIT_EXCEEDED
LDAP_UNAVAILABLE_CRITICAL_EXTENSION
LDAP_CONFIDENTIALITY_REQUIRED
LDAP_SASL_BIND_IN_PROGRESS
LDAP_AFFECTS_MULTIPLE_DSAS
LDAP_CONNECT_ERROR
LDAP_NOT_SUPPORTED
LDAP_CONTROL_NOT_FOUND
LDAP_NO_RESULTS_RETURNED
LDAP_MORE_RESULTS_TO_RETURN
LDAP_CLIENT_LOOP
LDAP_REFERRAL_LIMIT_EXCEEDED
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25.3. Freeing of String Data with ldap_memfree()
All strings received from the API (e.g., those returned by the
ldap_get_dn() or ldap_dn2ufn() functions) should be freed by calling
ldap_memfree() not free(). RFC 1823 did not define an ldap_memfree()
function.
25.4. Changes to ldap_result()
The meaning of the all parameter to ldap_result has changed slightly.
Nonzero values from RFC 1823 correspond to LDAP_MSG_ALL (0x01). There
is also a new possible value, LDAP_MSG_RECEIVED (0x02).
The result type LDAP_RES_MODDN is now returned where RFC 1823 returned
LDAP_RES_MODRDN. The actual value for these two macros is the same
(0x6D).
25.5. Changes to ldap_first_attribute() and ldap_next_attribute
Each non-NULL return value should be freed by calling ldap_memfree()
after use. In RFC 1823, these two functions returned a pointer to a
per-session buffer, which was not very thread-friendly.
After the last call to ldap_first_attribute() or ldap_next_attribute(),
the value set in the ptr parameter should be freed by calling ber_free(
ptr, 0 ). RFC 1823 did not mention that the ptr value should be freed.
The type of the ptr parameter was changed from void * to BerElement *.
25.6. Changes to ldap_modrdn() and ldap_modrdn_s() Functions
In RFC 1823, the ldap_modrdn() and ldap_modrdn_s() functions include a
parameter called deleteoldrdn. This does not match the great majority
of implementations, so in this specification the deleteoldrdn parameter
was removed from ldap_modrdn() and ldap_modrdn_s(). Two additional
functions that support deleteoldrdn and are widely implemented as well
were added to this specification: ldap_modrdn2() and ldap_modrdn2_s().
25.7. Changes to the berval structure
In RFC 1823, the bv_len element of the berval structure was defined as
an unsigned long. In this specification, the type is implementation-
specific, although it must be an unsigned integral type that is at least
32 bits in size. See the appendix "Data Types and Legacy
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Implementations" for additional considerations.
25.8. API Specification Clarified
RFC 1823 left many things unspecified, including behavior of various
memory disposal functions when a NULL pointer is presented, requirements
for header files, values of many macros, and so on. This specification
is more complete and generally tighter than the one in RFC 1823.
25.9. Deprecated Functions
A number of functions that are in RFC 1823 are labeled as "deprecated"
in this specification. In most cases, a replacement that provides
equivalent functionality has been defined. The deprecated functions
are:
ldap_bind()
Use ldap_simple_bind() or ldap_sasl_bind() instead.
ldap_bind_s()
Use ldap_simple_bind_s() or ldap_sasl_bind_s() instead.
ldap_kerberos_bind() and ldap_kerberos_bind_s()
No equivalent functions are provided.
ldap_modrdn() and ldap_modrdn2()
Use ldap_rename() instead.
ldap_modrdn_s() and ldap_modrdn2_s()
Use ldap_rename_s() instead.
ldap_open()
Use ldap_init() instead.
ldap_perror()
Use ldap_err2string() instead.
ldap_result2error()
Use ldap_parse_result() instead.
26. Appendix E - Data Types and Legacy Implementations
The data types associated with the length of a ber value (ber_len_t) and
the tag (ber_tag_t) have been defined in this specification as unsigned
integral types of implementation-specific size. This was done so that
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source and binary compatibility of the C LDAP API can be maintained
across ILP32 environments (where int, long, and pointers are all 32 bits
in size) and LP64 environments (where ints remain 32 bits but longs and
pointers grow to 64 bits).
In older implementations of the C LDAP API, such as those based on RFC
1823, implementors may have chosen to use an unsigned long for these
types. If a long data type was used, a port of an application to a 64-
bit operating system using the LP64 data model would find the size of
the BER length and tag types used by the C LDAP API to increase. Also,
if the legacy implementation had chosen to implement the types as an
unsigned int, adoption of a specification that mandated use of unsigned
longs would cause a source incompatibility in an LP64 application. By
using an implementation-specific data type, the C LDAP API implementa-
tion is free to choose the correct data type and the ability to maintain
source compatibility.
For example, suppose a legacy implementation chose to define the return
value of ber_skip_tag() as an unsigned long but wishes to have the
library return a 32-bit quantity in both ILP32 and LP64 data models.
The following typedefs for ber_tag_t will provide a fixed sized data
structure while preserving existing ILP32 source -- all without generat-
ing compiler warnings:
#if defined(_LP64)
typedef unsigned int ber_tag_t;
#else
typedef unsigned long ber_tag_t;
#endif
The above assumes that the the preprocessor symbol _LP64 is defined if
and only if the code is being compiled in an LP64 environment. Similar
code can be used to define an appropriate ber_len_t type.
27. Appendix F - Changes Made Since Last Document Revision
The previous version of this document was draft-ietf-ldapext-ldap-c-
api-02.txt, dated 23 February, 1999. This appendix lists all of the
changes made to that document to produce this one.
27.1. API Changes
Types: added the ber_len_t and ber_tag_t implementation-specific
unsigned integral data types to support source and binary compatibil-
ity between ILP32 and LP64 environments. Changes were made to the
"Common Data Structures" and "Encoded ASN.1 Value Manipulation" sec-
tions of this document.
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27.2. Editorial Changes
General: Added Appendix E - Data Types and Legacy Implementations;
moved list of recent document changes to Appendices F and G.
"Retrieving Information During Execution" section: removed misplaced
ldapai_vendor_name and ldapai_vendor_version from the LDAPAPI-
FeatureInfo structure description.
"Extended Operations" section: changed the names of the "requestoid"
and "requestdata" parameters in the function prototypes to match the
parameter descriptions. The old names were "exoid" and "exdata."
Appendix D - "Appendix D - Known Incompatibilities with RFC 1823 ":
Added note about changes to the berval structure.
28. Appendix G - Changes Made Since draft-ietf-ldapext-ldap-c-api-
01.txt
The version of this document that preceded draft-ietf-ldapext-ldap-c-
api-02.txt was draft-ietf-ldapext-ldap-c-api-01.txt, dated 7 August
1998. This appendix lists all of the changes made to that document to
produce draft-ietf-ldapext-ldap-c-api-02.txt.
28.1. API Changes
General: added the 'const' keyword to function prototypes where
appropriate.
Added two new sections that specify additional features and require-
ments for API implementors:
"Header File Requirements"
"A Client Control That Governs Referral Processing"
LDAP_VERSION_MAX, LDAP_VENDOR_NAME, and LDAP_VENDOR_VERSION macros.
Corrected LDAP_API_VERSION example code to use >= instead of >.
Added note about what value to use for LDAP_API_VERSION prior to pub-
lication of this draft as an RFC (2000 + draft revision number).
"Retrieving Information During Execution" section: added
LDAP_API_INFO_VERSION macro and clarified the text to explain the
behavior when there is a mismatch between LDAPAPIInfo structure ver-
sions. Added LDAP_OPT_API_FEATURE_INFO to allow applications to
retrieve version information about API extended features.
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"LDAP Session Handle Options" section: Added macro definitions for
LDAP_OPT_ON and LDAP_OPT_OFF and changed the "invalue" type for
Boolean options from "int" to "void *". For consistency, we now
require that applications dispose of "char *" and "LDAPControl *"
values that are returned. Added note about which option value ranges
are to be used for various purposes.
"Closing the session" section: added new function ldap_unbind_ext()
to allow controls to be used with unbind operations.
"Searching" section: added requirement that *res be set to NULL by
synchronous calls that fail to return any results.
"Modifying the Name of an Entry" section: added function prototypes
for ldap_modrdn2() and ldap_modrdn2_s() and corrected the ones for
ldap_modrdn() and ldap_modrdn_s() to match the most widely imple-
mented APIs.
"Obtaining Results and Peeking Inside LDAP Messages" section: added
requirement that "*res" be set to NULL when ldap_result() fails to
return any results. Added requirement that ldap_msgfree() accept a
NULL "res" parameter.
"Stepping Through the Attributes of an Entry" section: added
requirement that ldap_memfree() accept a NULL "mem" parameter.
"Encoded ASN.1 Value Manipulation - Encoding" section: added note
that implementations may support tags with a value larger than 32
(but this is not required).
"Encoded ASN.1 Value Manipulation - Decoding" section: changed the
LBER_ERROR and LBER_DEFAULT macros to end in "UL" instead of "L"
since all the functions that return these two values return an
"unsigned long" value.
28.2. Editorial changes
Removed section: "Appendix - Outstanding Issues."
Added two new editorial sections:
"Appendix - Summary of Requirements for API Extensions"
"Appendix - Known Incompatibilities with RFC 1823".
General: replaced all occurrences of "LDAP C API" with "C LDAP API"
for consistency.
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"Status of Memo" section: added a statement that this document is in
full conformance with all provisions of Section 10 of RFC2026. Also
revised the text about the Internet Draft current and shadow direc-
tories to match the latest I-D guidelines.
Document authors: removed Chris Weider from the list of authors (at
his own request) and added an explicit mention of him in the "Ack-
nowledgements" section. Updated Mark Wahl's company affiliation in
document preface. Added "(document editor)" after Mark Smith's name
in the "Authors' Addresses" section.
Copyright: updated the year to 1999.
"Introduction" section: expanded the sentence that mentioned the sam-
ple code appendix to mention all of the appendices.
"Overview of LDAP API Use" section: numbered the four simple steps
for using the API. Added mention of the referrals client control.
Clarified the text on character sets. Replaced mention of
ldap_bind() with ldap_sasl_bind() because the former is deprecated.
Added note that this API is designed for use in environments where
the 'int' type is at least 32 bits in size.
"Common Data Structures" section: added definition of BerElement so
it is defined before it is used. Added reference back to "Header
File Requirements" for "struct timeval" related considerations.
"Initializing an LDAP Session" section: moved note about ldap_open()
attempting to make a server connection closer to the ldap_open()
function prototype. Added note that using literal IPv6 addresses in
the "hostname" parameter is not yet supported.
"LDAP Session Handle Options" section: replaced one instance of
"Formerly" with "In RFC 1823." Added note about inheritance of
options when automatic referral following is enabled. Added
LDAP_OPT_API_INFO and LDAP_OPT_API_FEATURE_INFO for completeness (not
previously included in this section). Replaced erroneous references
to the "Using Controls" section with references to the "Working With
Controls" section. In the text describing the LDAP_OPT_HOST_NAME
option, added a reference to the "hostname" parameter of ldap_init()
for the syntax of the option value. Clarified that ldap_set_option()
makes a copy of the "invalue" data.
"Working With Controls" section: added a note to remind the reader
that server controls that are marked critical should not be used with
unbind and abandon operations since those two operations have no
server response.
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"Closing the session" section: made it clear that all open connec-
tions associated with a session handle are closed when any of the
unbind API functions are called.
"Searching" section: added note that only a subset of the filter
functionality is available when communicating with an LDAPv2 server.
Clarified text to explain when a local timeout is used and when it is
not.
"Abandoning An Operation" section: removed some redundant text from
the paragraph that explains the differences between ldap_abandon()
and ldap_abandon_ext().
"Obtaining Results and Peeking Inside LDAP Messages" section: clari-
fied that ldap_result() only returns messages for one request at a
time.
"Handling Errors and Parsing Results" section: replace a few
occurrences of LDAPResult with LDAPMessage (there is no type called
LDAPResult). Changed the names of the "resultoidp" and "resultdatap"
parameters to "retoidp" and "retdatap" to avoid confusion with LDAP
result messages.
"Stepping Through a List of Entries or References" section: added "or
References" to the section name to better reflect its contents.
Added missing description of "ref" parameter. Added mention of
ldap_first_reference() and ldap_next_reference() in sentence about
function return values.
"Stepping Through the Attributes of an Entry" section: added forward
reference for BerElement type.
"Parsing References" section: in the description of the "ref" parame-
ter, changed the phrase "these routines" to the more accurate "this
routine."
"Encoded ASN.1 Value Manipulation - General" section: changed text to
make sense given that the definition of BerElement now appears first
in the "Common Data Structures" section.
"Encoded ASN.1 Value Manipulation - Encoding" section: Changed the
style of function prototypes to better match the rest of the docu-
ment. Corrected a typo in the ber_bvdup() description ("as the"
replaced with "than the"). Changed "null" to "NULL" where appropri-
ate to be consistent with use elsewhere in the document. Removed
mention of sequences from the discussion of the LBER_USE_DER option.
Fixed some truncated sentences (by adding some missing '\' characters
to the nroff document source).
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C LDAP API C LDAP Application Program Interface 2 June 1999
"Encoded ASN.1 Value Manipulation - Encoding Example" section: sim-
plified the error handling in the example code through the use of a
'goto' statement.
"Encoded ASN.1 Value Manipulation - Decoding" section: Changed the
style of function prototypes to better match the rest of the docu-
ment. Changed "null" to "NULL" and "null-terminated" to "zero-
terminated" where appropriate to be consistent with use elsewhere in
the document. Fixed a typo (the text now says "an allocated" instead
of "a allocated."). Clarified the description of the 'n' format
character for ber_scanf().
"Encoded ASN.1 Value Manipulation - Decoding Example" section:
changed code to not define a macro that begins with "LDAP" since that
prefix is reserved for the API. Removed an extra 'i' from the format
string used in the first call to ber_scanf(). Changed error report-
ing code to send messages to stderr instead of stdout. Changed
declaration of "res" local variable from "int" to "unsigned long" and
corrected one test of the ber_scanf() return value to test against
LBER_ERROR instead of -1. Fixed improperly rendered strings (by
adding '\' characters to the nroff source for this document so that
'\t' and '\n' are correctly rendered).
"Acknowledgements" section: added the mention of Chris Weider.
Rephrased the text that gives credit to the National Science Founda-
tion (it now says "The original material upon which this specifica-
tion is based was supported by ..." instead of "This original
material upon which this revision is based was based upon work sup-
ported by ..."
In the "Bibliography" section: Added a reference to RFC 1345 and
ANSI/ISO C. Updated the LDAPv3 TLS and Sorting references to point
to the latest revisions of those documents.
"Appendix - Sample C LDAP API Code": added #include <stdio.h> to the
sample code. Changed the code to demonstrate good error handling by
freeing all memory and calling ldap_unbind() before returning.
Replaced calls to exit() with return statements. Fixed improperly
rendered strings (by adding '\' characters to the nroff source for
this document so that '\t' and '\n' are correctly rendered).
Expires: 2 December 1999 [Page 78]
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