5 X509_LOOKUP_hash_dir, X509_LOOKUP_file, X509_LOOKUP_store,
6 X509_load_cert_file_ex, X509_load_cert_file,
8 X509_load_cert_crl_file_ex, X509_load_cert_crl_file
9 - Default OpenSSL certificate lookup methods
13 #include <openssl/x509_vfy.h>
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);
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);
29 B<X509_LOOKUP_hash_dir> and B<X509_LOOKUP_file> are two certificate
30 lookup methods to use with B<X509_STORE>, provided by OpenSSL library.
32 Users of the library typically do not need to create instances of these
33 methods manually, they would be created automatically by
34 L<X509_STORE_load_locations(3)> or
35 L<SSL_CTX_load_verify_locations(3)>
38 Internally loading of certificates and CRLs is implemented via functions
39 B<X509_load_cert_crl_file>, B<X509_load_cert_file> and
40 B<X509_load_crl_file>. These functions support parameter I<type>, which
41 can be one of constants B<FILETYPE_PEM>, B<FILETYPE_ASN1> and
42 B<FILETYPE_DEFAULT>. They load certificates and/or CRLs from specified
43 file into memory cache of B<X509_STORE> objects which given B<ctx>
44 parameter is associated with.
46 Functions B<X509_load_cert_file> and
47 B<X509_load_crl_file> can load both PEM and DER formats depending of
48 type value. Because DER format cannot contain more than one certificate
49 or CRL object (while PEM can contain several concatenated PEM objects)
50 B<X509_load_cert_crl_file> with B<FILETYPE_ASN1> is equivalent to
51 B<X509_load_cert_file>.
53 Constant B<FILETYPE_DEFAULT> with NULL filename causes these functions
54 to load default certificate store file (see
55 L<X509_STORE_set_default_paths(3)>.
58 Functions return number of objects loaded from file or 0 in case of
61 Both methods support adding several certificate locations into one
64 This page documents certificate store formats used by these methods and
69 The B<X509_LOOKUP_file> method loads all the certificates or CRLs
70 present in a file into memory at the time the file is added as a
73 File format is ASCII text which contains concatenated PEM certificates
76 This method should be used by applications which work with a small
79 =head2 Hashed Directory Method
81 B<X509_LOOKUP_hash_dir> is a more advanced method, which loads
82 certificates and CRLs on demand, and caches them in memory once
83 they are loaded. As of OpenSSL 1.0.0, it also checks for newer CRLs
84 upon each lookup, so that newer CRLs are as soon as they appear in
87 The directory should contain one certificate or CRL per file in PEM format,
88 with a filename of the form I<hash>.I<N> for a certificate, or
89 I<hash>.B<r>I<N> for a CRL.
90 The I<hash> is the value returned by the L<X509_NAME_hash(3)> function applied
91 to the subject name for certificates or issuer name for CRLs.
92 The hash can also be obtained via the B<-hash> option of the
93 L<openssl-x509(1)> or L<openssl-crl(1)> commands.
95 The .I<N> or .B<r>I<N> suffix is a sequence number that starts at zero, and is
96 incremented consecutively for each certificate or CRL with the same I<hash>
98 Gaps in the sequence numbers are not supported, it is assumed that there are no
99 more objects with the same hash beyond the first missing number in the
102 Sequence numbers make it possible for the directory to contain multiple
103 certificates with same subject name hash value.
104 For example, it is possible to have in the store several certificates with same
105 subject or several CRLs with same issuer (and, for example, different validity
108 When checking for new CRLs once one CRL for given hash value is
109 loaded, hash_dir lookup method checks only for certificates with
110 sequence number greater than that of the already cached CRL.
112 Note that the hash algorithm used for subject name hashing changed in OpenSSL
113 1.0.0, and all certificate stores have to be rehashed when moving from OpenSSL
116 OpenSSL includes a L<openssl-rehash(1)> utility which creates symlinks with
117 hashed names for all files with F<.pem> suffix in a given directory.
119 =head2 OSSL_STORE Method
121 B<X509_LOOKUP_store> is a method that allows access to any store of
122 certificates and CRLs through any loader supported by
124 It works with the help of URIs, which can be direct references to
125 certificates or CRLs, but can also be references to catalogues of such
126 objects (that behave like directories).
128 This method overlaps the L</File Method> and L</Hashed Directory Method>
129 because of the 'file:' scheme loader.
130 It does no caching of its own, but can use a caching L<ossl_store(7)>
131 loader, and therefore depends on the loader's capability.
135 X509_LOOKUP_hash_dir(), X509_LOOKUP_file() and X509_LOOKUP_store()
136 always return a valid B<X509_LOOKUP_METHOD> structure.
138 X509_load_cert_file(), X509_load_crl_file() and X509_load_cert_crl_file() return
139 the number of loaded objects or 0 on error.
143 L<PEM_read_PrivateKey(3)>,
144 L<X509_STORE_load_locations(3)>,
145 L<X509_store_add_lookup(3)>,
146 L<SSL_CTX_load_verify_locations(3)>,
147 L<X509_LOOKUP_meth_new(3)>,
152 The functions X509_load_cert_file_ex(),
153 X509_load_cert_crl_file_ex() and X509_LOOKUP_store() were added in
158 Copyright 2015-2020 The OpenSSL Project Authors. All Rights Reserved.
160 Licensed under the Apache License 2.0 (the "License"). You may not use
161 this file except in compliance with the License. You can obtain a copy
162 in the file LICENSE in the source distribution or at
163 L<https://www.openssl.org/source/license.html>.