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curl/lib/vauth/krb5_gssapi.c
Patrick Monnerat 7da2990b19
auth: do not append zero-terminator to authorisation id in kerberos 
RFC4752 Section 3.1 states "The authorization identity is not terminated
with a zero-valued (%x00) octet". Although a comment in code said it may
be needed anyway, nothing confirms it. In addition, servers may consider
it as part of the identity, causing a failure.

Closes #7008
2021-08-16 08:36:10 +02:00

322 lines
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C
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/***************************************************************************
* _ _ ____ _
* Project ___| | | | _ \| |
* / __| | | | |_) | |
* | (__| |_| | _ <| |___
* \___|\___/|_| \_\_____|
*
* Copyright (C) 2014 - 2019, Steve Holme, <steve_holme@hotmail.com>.
* Copyright (C) 2015 - 2021, Daniel Stenberg, <daniel@haxx.se>, et al.
*
* This software is licensed as described in the file COPYING, which
* you should have received as part of this distribution. The terms
* are also available at https://curl.se/docs/copyright.html.
*
* You may opt to use, copy, modify, merge, publish, distribute and/or sell
* copies of the Software, and permit persons to whom the Software is
* furnished to do so, under the terms of the COPYING file.
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
* KIND, either express or implied.
*
* RFC4752 The Kerberos V5 ("GSSAPI") SASL Mechanism
*
***************************************************************************/
#include "curl_setup.h"
#if defined(HAVE_GSSAPI) && defined(USE_KERBEROS5)
#include <curl/curl.h>
#include "vauth/vauth.h"
#include "curl_sasl.h"
#include "urldata.h"
#include "curl_gssapi.h"
#include "sendf.h"
#include "curl_printf.h"
/* The last #include files should be: */
#include "curl_memory.h"
#include "memdebug.h"
/*
* Curl_auth_is_gssapi_supported()
*
* This is used to evaluate if GSSAPI (Kerberos V5) is supported.
*
* Parameters: None
*
* Returns TRUE if Kerberos V5 is supported by the GSS-API library.
*/
bool Curl_auth_is_gssapi_supported(void)
{
return TRUE;
}
/*
* Curl_auth_create_gssapi_user_message()
*
* This is used to generate an already encoded GSSAPI (Kerberos V5) user token
* message ready for sending to the recipient.
*
* Parameters:
*
* data [in] - The session handle.
* userp [in] - The user name.
* passwdp [in] - The user's password.
* service [in] - The service type such as http, smtp, pop or imap.
* host [in[ - The host name.
* mutual_auth [in] - Flag specifying whether or not mutual authentication
* is enabled.
* chlg [in] - Optional challenge message.
* krb5 [in/out] - The Kerberos 5 data struct being used and modified.
* out [out] - The result storage.
*
* Returns CURLE_OK on success.
*/
CURLcode Curl_auth_create_gssapi_user_message(struct Curl_easy *data,
const char *userp,
const char *passwdp,
const char *service,
const char *host,
const bool mutual_auth,
const struct bufref *chlg,
struct kerberos5data *krb5,
struct bufref *out)
{
CURLcode result = CURLE_OK;
OM_uint32 major_status;
OM_uint32 minor_status;
OM_uint32 unused_status;
gss_buffer_desc spn_token = GSS_C_EMPTY_BUFFER;
gss_buffer_desc input_token = GSS_C_EMPTY_BUFFER;
gss_buffer_desc output_token = GSS_C_EMPTY_BUFFER;
(void) userp;
(void) passwdp;
if(!krb5->spn) {
/* Generate our SPN */
char *spn = Curl_auth_build_spn(service, NULL, host);
if(!spn)
return CURLE_OUT_OF_MEMORY;
/* Populate the SPN structure */
spn_token.value = spn;
spn_token.length = strlen(spn);
/* Import the SPN */
major_status = gss_import_name(&minor_status, &spn_token,
GSS_C_NT_HOSTBASED_SERVICE, &krb5->spn);
if(GSS_ERROR(major_status)) {
Curl_gss_log_error(data, "gss_import_name() failed: ",
major_status, minor_status);
free(spn);
return CURLE_AUTH_ERROR;
}
free(spn);
}
if(chlg) {
if(!Curl_bufref_len(chlg)) {
infof(data, "GSSAPI handshake failure (empty challenge message)");
return CURLE_BAD_CONTENT_ENCODING;
}
input_token.value = (void *) Curl_bufref_ptr(chlg);
input_token.length = Curl_bufref_len(chlg);
}
major_status = Curl_gss_init_sec_context(data,
&minor_status,
&krb5->context,
krb5->spn,
&Curl_krb5_mech_oid,
GSS_C_NO_CHANNEL_BINDINGS,
&input_token,
&output_token,
mutual_auth,
NULL);
if(GSS_ERROR(major_status)) {
if(output_token.value)
gss_release_buffer(&unused_status, &output_token);
Curl_gss_log_error(data, "gss_init_sec_context() failed: ",
major_status, minor_status);
return CURLE_AUTH_ERROR;
}
if(output_token.value && output_token.length) {
result = Curl_bufref_memdup(out, output_token.value, output_token.length);
gss_release_buffer(&unused_status, &output_token);
}
else
Curl_bufref_set(out, mutual_auth? "": NULL, 0, NULL);
return result;
}
/*
* Curl_auth_create_gssapi_security_message()
*
* This is used to generate an already encoded GSSAPI (Kerberos V5) security
* token message ready for sending to the recipient.
*
* Parameters:
*
* data [in] - The session handle.
* authzid [in] - The authorization identity if some.
* chlg [in] - Optional challenge message.
* krb5 [in/out] - The Kerberos 5 data struct being used and modified.
* out [out] - The result storage.
*
* Returns CURLE_OK on success.
*/
CURLcode Curl_auth_create_gssapi_security_message(struct Curl_easy *data,
const char *authzid,
const struct bufref *chlg,
struct kerberos5data *krb5,
struct bufref *out)
{
CURLcode result = CURLE_OK;
size_t messagelen = 0;
unsigned char *message = NULL;
OM_uint32 major_status;
OM_uint32 minor_status;
OM_uint32 unused_status;
gss_buffer_desc input_token = GSS_C_EMPTY_BUFFER;
gss_buffer_desc output_token = GSS_C_EMPTY_BUFFER;
unsigned char *indata;
gss_qop_t qop = GSS_C_QOP_DEFAULT;
unsigned int sec_layer = 0;
unsigned int max_size = 0;
/* Ensure we have a valid challenge message */
if(!Curl_bufref_len(chlg)) {
infof(data, "GSSAPI handshake failure (empty security message)");
return CURLE_BAD_CONTENT_ENCODING;
}
/* Setup the challenge "input" security buffer */
input_token.value = (void *) Curl_bufref_ptr(chlg);
input_token.length = Curl_bufref_len(chlg);
/* Decrypt the inbound challenge and obtain the qop */
major_status = gss_unwrap(&minor_status, krb5->context, &input_token,
&output_token, NULL, &qop);
if(GSS_ERROR(major_status)) {
Curl_gss_log_error(data, "gss_unwrap() failed: ",
major_status, minor_status);
return CURLE_BAD_CONTENT_ENCODING;
}
/* Not 4 octets long so fail as per RFC4752 Section 3.1 */
if(output_token.length != 4) {
infof(data, "GSSAPI handshake failure (invalid security data)");
return CURLE_BAD_CONTENT_ENCODING;
}
/* Extract the security layer and the maximum message size */
indata = output_token.value;
sec_layer = indata[0];
max_size = (indata[1] << 16) | (indata[2] << 8) | indata[3];
/* Free the challenge as it is not required anymore */
gss_release_buffer(&unused_status, &output_token);
/* Process the security layer */
if(!(sec_layer & GSSAUTH_P_NONE)) {
infof(data, "GSSAPI handshake failure (invalid security layer)");
return CURLE_BAD_CONTENT_ENCODING;
}
sec_layer &= GSSAUTH_P_NONE; /* We do not support a security layer */
/* Process the maximum message size the server can receive */
if(max_size > 0) {
/* The server has told us it supports a maximum receive buffer, however, as
we don't require one unless we are encrypting data, we tell the server
our receive buffer is zero. */
max_size = 0;
}
/* Allocate our message */
messagelen = 4;
if(authzid)
messagelen += strlen(authzid);
message = malloc(messagelen);
if(!message)
return CURLE_OUT_OF_MEMORY;
/* Populate the message with the security layer and client supported receive
message size. */
message[0] = sec_layer & 0xFF;
message[1] = (max_size >> 16) & 0xFF;
message[2] = (max_size >> 8) & 0xFF;
message[3] = max_size & 0xFF;
/* If given, append the authorization identity. */
if(authzid && *authzid)
memcpy(message + 4, authzid, messagelen - 4);
/* Setup the "authentication data" security buffer */
input_token.value = message;
input_token.length = messagelen;
/* Encrypt the data */
major_status = gss_wrap(&minor_status, krb5->context, 0,
GSS_C_QOP_DEFAULT, &input_token, NULL,
&output_token);
if(GSS_ERROR(major_status)) {
Curl_gss_log_error(data, "gss_wrap() failed: ",
major_status, minor_status);
free(message);
return CURLE_AUTH_ERROR;
}
/* Return the response. */
result = Curl_bufref_memdup(out, output_token.value, output_token.length);
/* Free the output buffer */
gss_release_buffer(&unused_status, &output_token);
/* Free the message buffer */
free(message);
return result;
}
/*
* Curl_auth_cleanup_gssapi()
*
* This is used to clean up the GSSAPI (Kerberos V5) specific data.
*
* Parameters:
*
* krb5 [in/out] - The Kerberos 5 data struct being cleaned up.
*
*/
void Curl_auth_cleanup_gssapi(struct kerberos5data *krb5)
{
OM_uint32 minor_status;
/* Free our security context */
if(krb5->context != GSS_C_NO_CONTEXT) {
gss_delete_sec_context(&minor_status, &krb5->context, GSS_C_NO_BUFFER);
krb5->context = GSS_C_NO_CONTEXT;
}
/* Free the SPN */
if(krb5->spn != GSS_C_NO_NAME) {
gss_release_name(&minor_status, &krb5->spn);
krb5->spn = GSS_C_NO_NAME;
}
}
#endif /* HAVE_GSSAPI && USE_KERBEROS5 */
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