xref: /openssl/doc/man3/X509_LOOKUP_hash_dir.pod (revision d2f82495)
1=pod
2
3=head1 NAME
4
5X509_LOOKUP_hash_dir, X509_LOOKUP_file, X509_LOOKUP_store,
6X509_load_cert_file_ex, X509_load_cert_file,
7X509_load_crl_file,
8X509_load_cert_crl_file_ex, X509_load_cert_crl_file
9- Default OpenSSL certificate lookup methods
10
11=head1 SYNOPSIS
12
13 #include <openssl/x509_vfy.h>
14
15 X509_LOOKUP_METHOD *X509_LOOKUP_hash_dir(void);
16 X509_LOOKUP_METHOD *X509_LOOKUP_file(void);
17 X509_LOOKUP_METHOD *X509_LOOKUP_store(void);
18
19 int X509_load_cert_file_ex(X509_LOOKUP *ctx, const char *file, int type,
20                            OSSL_LIB_CTX *libctx, const char *propq);
21 int X509_load_cert_file(X509_LOOKUP *ctx, const char *file, int type);
22 int X509_load_crl_file(X509_LOOKUP *ctx, const char *file, int type);
23 int X509_load_cert_crl_file_ex(X509_LOOKUP *ctx, const char *file, int type,
24                                OSSL_LIB_CTX *libctx, const char *propq);
25 int X509_load_cert_crl_file(X509_LOOKUP *ctx, const char *file, int type);
26
27=head1 DESCRIPTION
28
29B<X509_LOOKUP_hash_dir> and B<X509_LOOKUP_file> are two certificate
30lookup methods to use with B<X509_STORE>, provided by OpenSSL library.
31
32Users of the library typically do not need to create instances of these
33methods manually, they would be created automatically by
34L<X509_STORE_load_locations(3)> or
35L<SSL_CTX_load_verify_locations(3)>
36functions.
37
38Internally loading of certificates and CRLs is implemented via functions
39B<X509_load_cert_crl_file>, B<X509_load_cert_file> and
40B<X509_load_crl_file>. These functions support parameter I<type>, which
41can be one of constants B<FILETYPE_PEM>, B<FILETYPE_ASN1> and
42B<FILETYPE_DEFAULT>. They load certificates and/or CRLs from specified
43file into memory cache of B<X509_STORE> objects which given B<ctx>
44parameter is associated with.
45
46Functions B<X509_load_cert_file> and
47B<X509_load_crl_file> can load both PEM and DER formats depending of
48type value. Because DER format cannot contain more than one certificate
49or CRL object (while PEM can contain several concatenated PEM objects)
50B<X509_load_cert_crl_file> with B<FILETYPE_ASN1> is equivalent to
51B<X509_load_cert_file>.
52
53Constant B<FILETYPE_DEFAULT> with NULL filename causes these functions
54to load default certificate store file (see
55L<X509_STORE_set_default_paths(3)>.
56
57
58Functions return number of objects loaded from file or 0 in case of
59error.
60
61Both methods support adding several certificate locations into one
62B<X509_STORE>.
63
64This page documents certificate store formats used by these methods and
65caching policy.
66
67=head2 File Method
68
69The B<X509_LOOKUP_file> method loads all the certificates or CRLs
70present in a file into memory at the time the file is added as a
71lookup source.
72
73File format is ASCII text which contains concatenated PEM certificates
74and CRLs.
75
76This method should be used by applications which work with a small
77set of CAs.
78
79=head2 Hashed Directory Method
80
81B<X509_LOOKUP_hash_dir> is a more advanced method, which loads
82certificates and CRLs on demand, and caches them in memory once
83they are loaded. As of OpenSSL 1.0.0, it also checks for newer CRLs
84upon each lookup, so that newer CRLs are as soon as they appear in
85the directory.
86
87The directory should contain one certificate or CRL per file in PEM format,
88with a filename of the form I<hash>.I<N> for a certificate, or
89I<hash>.B<r>I<N> for a CRL.
90The I<hash> is the value returned by the L<X509_NAME_hash_ex(3)> function
91applied to the subject name for certificates or issuer name for CRLs.
92The hash can also be obtained via the B<-hash> option of the
93L<openssl-x509(1)> or L<openssl-crl(1)> commands.
94
95The .I<N> or .B<r>I<N> suffix is a sequence number that starts at zero, and is
96incremented consecutively for each certificate or CRL with the same I<hash>
97value.
98Gaps in the sequence numbers are not supported, it is assumed that there are no
99more objects with the same hash beyond the first missing number in the
100sequence.
101
102Sequence numbers make it possible for the directory to contain multiple
103certificates with same subject name hash value.
104For example, it is possible to have in the store several certificates with same
105subject or several CRLs with same issuer (and, for example, different validity
106period).
107
108When checking for new CRLs once one CRL for given hash value is
109loaded, hash_dir lookup method checks only for certificates with
110sequence number greater than that of the already cached CRL.
111
112Note that the hash algorithm used for subject name hashing changed in OpenSSL
1131.0.0, and all certificate stores have to be rehashed when moving from OpenSSL
1140.9.8 to 1.0.0.
115
116OpenSSL includes a L<openssl-rehash(1)> utility which creates symlinks with
117hashed names for all files with F<.pem> suffix in a given directory.
118
119=head2 OSSL_STORE Method
120
121B<X509_LOOKUP_store> is a method that allows access to any store of
122certificates and CRLs through any loader supported by
123L<ossl_store(7)>.
124It works with the help of URIs, which can be direct references to
125certificates or CRLs, but can also be references to catalogues of such
126objects (that behave like directories).
127
128This method overlaps the L</File Method> and L</Hashed Directory Method>
129because of the 'file:' scheme loader.
130It does no caching of its own, but can use a caching L<ossl_store(7)>
131loader, and therefore depends on the loader's capability.
132
133=head1 RETURN VALUES
134
135X509_LOOKUP_hash_dir(), X509_LOOKUP_file() and X509_LOOKUP_store()
136always return a valid B<X509_LOOKUP_METHOD> structure.
137
138X509_load_cert_file(), X509_load_crl_file() and X509_load_cert_crl_file() return
139the number of loaded objects or 0 on error.
140
141=head1 SEE ALSO
142
143L<PEM_read_PrivateKey(3)>,
144L<X509_STORE_load_locations(3)>,
145L<SSL_CTX_load_verify_locations(3)>,
146L<X509_LOOKUP_meth_new(3)>,
147L<ossl_store(7)>
148
149=head1 HISTORY
150
151The functions X509_load_cert_file_ex(),
152X509_load_cert_crl_file_ex() and X509_LOOKUP_store() were added in
153OpenSSL 3.0.
154
155=head1 COPYRIGHT
156
157Copyright 2015-2021 The OpenSSL Project Authors. All Rights Reserved.
158
159Licensed under the Apache License 2.0 (the "License").  You may not use
160this file except in compliance with the License.  You can obtain a copy
161in the file LICENSE in the source distribution or at
162L<https://www.openssl.org/source/license.html>.
163
164=cut
165