mirror of
https://github.com/openssl/openssl.git
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123 lines
4.3 KiB
Plaintext
123 lines
4.3 KiB
Plaintext
=pod
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=head1 NAME
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X509_LOOKUP_hash_dir, X509_LOOKUP_file,
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X509_load_cert_file,
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X509_load_crl_file,
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X509_load_cert_crl_file - Default OpenSSL certificate
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lookup methods
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=head1 SYNOPSIS
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#include <openssl/x509_vfy.h>
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X509_LOOKUP_METHOD *X509_LOOKUP_hash_dir(void);
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X509_LOOKUP_METHOD *X509_LOOKUP_file(void);
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int X509_load_cert_file(X509_LOOKUP *ctx, const char *file, int type);
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int X509_load_crl_file(X509_LOOKUP *ctx, const char *file, int type);
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int X509_load_cert_crl_file(X509_LOOKUP *ctx, const char *file, int type);
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=head1 DESCRIPTION
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B<X509_LOOKUP_hash_dir> and B<X509_LOOKUP_file> are two certificate
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lookup methods to use with B<X509_STORE>, provided by OpenSSL library.
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Users of the library typically do not need to create instances of these
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methods manually, they would be created automatically by
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L<X509_STORE_load_locations(3)> or
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L<SSL_CTX_load_verify_locations(3)>
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functions.
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Internally loading of certificates and CRLs is implemented via functions
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B<X509_load_cert_crl_file>, B<X509_load_cert_file> and
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B<X509_load_crl_file>. These functions support parameter I<type>, which
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can be one of constants B<FILETYPE_PEM>, B<FILETYPE_ASN1> and
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B<FILETYPE_DEFAULT>. They load certificates and/or CRLs from specified
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file into memory cache of B<X509_STORE> objects which given B<ctx>
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parameter is associated with.
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Functions B<X509_load_cert_file> and
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B<X509_load_crl_file> can load both PEM and DER formats depending of
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type value. Because DER format cannot contain more than one certificate
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or CRL object (while PEM can contain several concatenated PEM objects)
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B<X509_load_cert_crl_file> with B<FILETYPE_ASN1> is equivalent to
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B<X509_load_cert_file>.
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Constant B<FILETYPE_DEFAULT> with NULL filename causes these functions
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to load default certificate store file (see
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L<X509_STORE_set_default_paths(3)>.
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Functions return number of objects loaded from file or 0 in case of
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error.
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Both methods support adding several certificate locations into one
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B<X509_STORE>.
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This page documents certificate store formats used by these methods and
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caching policy.
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=head2 FILE METHOD
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The B<X509_LOOKUP_file> method loads all the certificates or CRLs
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present in a file into memory at the time the file is added as a
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lookup source.
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File format is ASCII text which contains concatenated PEM certificates
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and CRLs.
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This method should be used by applications which work with a small
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set of CAs.
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=head2 HASHED DIR METHOD
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B<X509_LOOKUP_hash_dir> is a more advanced method, which loads
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certificates and CRLs on demand, and caches them in memory once
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they are loaded. As of OpenSSL 1.0.0, it also checks for newer CRLs
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upon each lookup, so that newer CRLs are as soon as they appear in
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the directory.
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The directory should contain one certificate or CRL per file in PEM format,
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with a file name of the form I<hash>.I<N> for a certificate, or
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I<hash>.B<r>I<N> for a CRL.
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The I<hash> is the value returned by the L<X509_NAME_hash(3)> function applied
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to the subject name for certificates or issuer name for CRLs.
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The hash can also be obtained via the B<-hash> option of the L<x509(1)> or
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L<crl(1)> commands.
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The .I<N> or .B<r>I<N> suffix is a sequence number that starts at zero, and is
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incremented consecutively for each certificate or CRL with the same I<hash>
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value.
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Gaps in the sequence numbers are not supported, it is assumed that there are no
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more objects with the same hash beyond the first missing number in the
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sequence.
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Sequence numbers make it possible for the directory to contain multiple
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certificates with same subject name hash value.
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For example, it is possible to have in the store several certificates with same
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subject or several CRLs with same issuer (and, for example, different validity
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period).
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When checking for new CRLs once one CRL for given hash value is
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loaded, hash_dir lookup method checks only for certificates with
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sequence number greater than that of the already cached CRL.
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Note that the hash algorithm used for subject name hashing changed in OpenSSL
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1.0.0, and all certificate stores have to be rehashed when moving from OpenSSL
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0.9.8 to 1.0.0.
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OpenSSL includes a L<c_rehash(1)> utility which creates symlinks with correct
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hashed names for all files with .pem suffix in a given directory.
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=head1 SEE ALSO
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L<pem(3)>, L<d2i_X509_bio(3)>,
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L<X509_STORE_load_locations(3)>,
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L<X609_store_add_lookup(3)>,
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L<SSL_CTX_load_verify_locations(3)>,
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=cut
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