doc/man3/X509_STORE_CTX_new.pod

   1 =pod
   2
   3 =head1 NAME
   4
   5 X509_STORE_CTX_new_ex, X509_STORE_CTX_new, X509_STORE_CTX_cleanup,
   6 X509_STORE_CTX_free, X509_STORE_CTX_init, X509_STORE_CTX_set0_trusted_stack,
   7 X509_STORE_CTX_set_cert, X509_STORE_CTX_set0_crls,
   8 X509_STORE_CTX_get0_param, X509_STORE_CTX_set0_param,
   9 X509_STORE_CTX_get0_untrusted, X509_STORE_CTX_set0_untrusted,
  10 X509_STORE_CTX_get_num_untrusted,
  11 X509_STORE_CTX_get0_chain, X509_STORE_CTX_set0_verified_chain,
  12 X509_STORE_CTX_set_default,
  13 X509_STORE_CTX_set_verify,
  14 X509_STORE_CTX_verify_fn,
  15 X509_STORE_CTX_set_purpose,
  16 X509_STORE_CTX_set_trust,
  17 X509_STORE_CTX_purpose_inherit
  18 - X509_STORE_CTX initialisation
  19
  20 =head1 SYNOPSIS
  21
  22  #include <openssl/x509_vfy.h>
  23
  24  X509_STORE_CTX *X509_STORE_CTX_new_ex(OSSL_LIB_CTX *libctx, const char *propq);
  25  X509_STORE_CTX *X509_STORE_CTX_new(void);
  26  void X509_STORE_CTX_cleanup(X509_STORE_CTX *ctx);
  27  void X509_STORE_CTX_free(X509_STORE_CTX *ctx);
  28
  29  int X509_STORE_CTX_init(X509_STORE_CTX *ctx, X509_STORE *trust_store,
  30                          X509 *target, STACK_OF(X509) *untrusted);
  31
  32  void X509_STORE_CTX_set0_trusted_stack(X509_STORE_CTX *ctx, STACK_OF(X509) *sk);
  33
  34  void X509_STORE_CTX_set_cert(X509_STORE_CTX *ctx, X509 *target);
  35  void X509_STORE_CTX_set0_crls(X509_STORE_CTX *ctx, STACK_OF(X509_CRL) *sk);
  36
  37  X509_VERIFY_PARAM *X509_STORE_CTX_get0_param(const X509_STORE_CTX *ctx);
  38  void X509_STORE_CTX_set0_param(X509_STORE_CTX *ctx, X509_VERIFY_PARAM *param);
  39
  40  STACK_OF(X509)* X509_STORE_CTX_get0_untrusted(const X509_STORE_CTX *ctx);
  41  void X509_STORE_CTX_set0_untrusted(X509_STORE_CTX *ctx, STACK_OF(X509) *sk);
  42
  43  int X509_STORE_CTX_get_num_untrusted(const X509_STORE_CTX *ctx);
  44  STACK_OF(X509) *X509_STORE_CTX_get0_chain(const X509_STORE_CTX *ctx);
  45  void X509_STORE_CTX_set0_verified_chain(X509_STORE_CTX *ctx, STACK_OF(X509) *chain);
  46
  47  int X509_STORE_CTX_set_default(X509_STORE_CTX *ctx, const char *name);
  48  typedef int (*X509_STORE_CTX_verify_fn)(X509_STORE_CTX *);
  49  void X509_STORE_CTX_set_verify(X509_STORE_CTX *ctx, X509_STORE_CTX_verify_fn verify);
  50
  51  int X509_STORE_CTX_set_purpose(X509_STORE_CTX *ctx, int purpose);
  52  int X509_STORE_CTX_set_trust(X509_STORE_CTX *ctx, int trust);
  53  int X509_STORE_CTX_purpose_inherit(X509_STORE_CTX *ctx, int def_purpose,
  54                                     int purpose, int trust);
  55
  56 =head1 DESCRIPTION
  57
  58 These functions initialise an B<X509_STORE_CTX> structure for subsequent use
  59 by L<X509_verify_cert(3)> or L<X509_STORE_CTX_verify(3)>.
  60
  61 X509_STORE_CTX_new_ex() returns a newly initialised B<X509_STORE_CTX>
  62 structure associated with the specified library context I<libctx> and property
  63 query string I<propq>. Any cryptographic algorithms fetched while performing
  64 processing with the X509_STORE_CTX will use that library context and property
  65 query string.
  66
  67 X509_STORE_CTX_new() is the same as X509_STORE_CTX_new_ex() except that
  68 the default library context and a NULL property query string are used.
  69
  70 X509_STORE_CTX_cleanup() internally cleans up an B<X509_STORE_CTX> structure.
  71 It is used by X509_STORE_CTX_init() and X509_STORE_CTX_free().
  72
  73 X509_STORE_CTX_free() completely frees up I<ctx>. After this call I<ctx>
  74 is no longer valid.
  75 If I<ctx> is NULL nothing is done.
  76
  77 X509_STORE_CTX_init() sets up I<ctx> for a subsequent verification operation.
  78 It must be called before each call to L<X509_verify_cert(3)> or
  79 L<X509_STORE_CTX_verify(3)>, i.e., a context is only good for one verification.
  80 If you want to verify a further certificate or chain with the same I<ctx>
  81 then you must call X509_STORE_CTX_init() again.
  82 The trusted certificate store is set to I<trust_store> of type B<X509_STORE>.
  83 This may be NULL because there are no trusted certificates or because
  84 they are provided simply as a list using X509_STORE_CTX_set0_trusted_stack().
  85 The certificate to be verified is set to I<target>,
  86 and a list of additional certificates may be provided in I<untrusted>,
  87 which will be untrusted but may be used to build the chain.
  88 Each of the I<trust_store>, I<target> and I<untrusted> parameters can be NULL.
  89 Yet note that L<X509_verify_cert(3)> and L<X509_STORE_CTX_verify(3)>
  90 will need a verification target.
  91 This can also be set using X509_STORE_CTX_set_cert().
  92 For L<X509_STORE_CTX_verify(3)>, which takes by default the first element of the
  93 list of untrusted certificates as its verification target,
  94 this can be also set indirectly using X509_STORE_CTX_set0_untrusted().
  95
  96 X509_STORE_CTX_set0_trusted_stack() sets the set of trusted certificates of
  97 I<ctx> to I<sk>. This is an alternative way of specifying trusted certificates
  98 instead of using an B<X509_STORE> where its complexity is not needed
  99 or to make sure that only the given set I<sk> of certificates are trusted.
 100
 101 X509_STORE_CTX_set_cert() sets the target certificate to be verified in I<ctx>
 102 to I<target>.
 103
 104 X509_STORE_CTX_set0_verified_chain() sets the validated chain to I<chain>.
 105 Ownership of the chain is transferred to I<ctx>,
 106 and so it should not be free'd by the caller.
 107
 108 X509_STORE_CTX_get0_chain() returns the internal pointer used by the
 109 I<ctx> that contains the constructed (output) chain.
 110
 111 X509_STORE_CTX_set0_crls() sets a set of CRLs to use to aid certificate
 112 verification to I<sk>. These CRLs will only be used if CRL verification is
 113 enabled in the associated B<X509_VERIFY_PARAM> structure. This might be
 114 used where additional "useful" CRLs are supplied as part of a protocol,
 115 for example in a PKCS#7 structure.
 116
 117 X509_STORE_CTX_get0_param() retrieves an internal pointer
 118 to the verification parameters associated with I<ctx>.
 119
 120 X509_STORE_CTX_set0_param() sets the internal verification parameter pointer
 121 to I<param>. After this call B<param> should not be used.
 122
 123 X509_STORE_CTX_get0_untrusted() retrieves an internal pointer to the
 124 stack of untrusted certificates associated with I<ctx>.
 125
 126 X509_STORE_CTX_set0_untrusted() sets the internal pointer to the stack
 127 of untrusted certificates associated with I<ctx> to I<sk>.
 128 X509_STORE_CTX_verify() will take the first element, if any,
 129 as its default target if the target certificate is not set explicitly.
 130
 131 X509_STORE_CTX_get_num_untrusted() returns the number of untrusted certificates
 132 that were used in building the chain.
 133 This is can be used after calling L<X509_verify_cert(3)> and similar functions.
 134 With L<X509_STORE_CTX_verify(3)>, this does not count the first chain element.
 135
 136 X509_STORE_CTX_get0_chain() returns the internal pointer used by the
 137 I<ctx> that contains the validated chain.
 138
 139 Details of the chain building and checking process are described in
 140 L<openssl-verification-options(1)/Certification Path Building> and
 141 L<openssl-verification-options(1)/Certification Path Validation>.
 142
 143 X509_STORE_CTX_set0_verified_chain() sets the validated chain used
 144 by I<ctx> to be I<chain>.
 145 Ownership of the chain is transferred to I<ctx>,
 146 and so it should not be free'd by the caller.
 147
 148 X509_STORE_CTX_set_default() looks up and sets the default verification
 149 method to I<name>. This uses the function X509_VERIFY_PARAM_lookup() to
 150 find an appropriate set of parameters from the purpose identifier I<name>.
 151 Currently defined purposes are C<sslclient>, C<sslserver>, C<nssslserver>,
 152 C<smimesign>, C<smimeencrypt>, C<crlsign>, C<ocsphelper>, C<timestampsign>,
 153 and C<any>.
 154
 155 X509_STORE_CTX_set_verify() provides the capability for overriding the default
 156 verify function. This function is responsible for verifying chain signatures and
 157 expiration times.
 158
 159 A verify function is defined as an X509_STORE_CTX_verify type which has the
 160 following signature:
 161
 162  int (*verify)(X509_STORE_CTX *);
 163
 164 This function should receive the current X509_STORE_CTX as a parameter and
 165 return 1 on success or 0 on failure.
 166
 167 X509 certificates may contain information about what purposes keys contained
 168 within them can be used for. For example "TLS WWW Server Authentication" or
 169 "Email Protection". This "key usage" information is held internally to the
 170 certificate itself. In addition the trust store containing trusted certificates
 171 can declare what purposes we trust different certificates for. This "trust"
 172 information is not held within the certificate itself but is "meta" information
 173 held alongside it. This "meta" information is associated with the certificate
 174 after it is issued and could be determined by a system administrator. For
 175 example a certificate might declare that it is suitable for use for both
 176 "TLS WWW Server Authentication" and "TLS Client Authentication", but a system
 177 administrator might only trust it for the former. An X.509 certificate extension
 178 exists that can record extended key usage information to supplement the purpose
 179 information described above. This extended mechanism is arbitrarily extensible
 180 and not well suited for a generic library API; applications that need to
 181 validate extended key usage information in certificates will need to define a
 182 custom "purpose" (see below) or supply a nondefault verification callback
 183 (L<X509_STORE_set_verify_cb_func(3)>).
 184
 185 X509_STORE_CTX_set_purpose() sets the purpose for the target certificate being
 186 verified in the I<ctx>. Built-in available values for the I<purpose> argument
 187 are B<X509_PURPOSE_SSL_CLIENT>, B<X509_PURPOSE_SSL_SERVER>,
 188 B<X509_PURPOSE_NS_SSL_SERVER>, B<X509_PURPOSE_SMIME_SIGN>,
 189 B<X509_PURPOSE_SMIME_ENCRYPT>, B<X509_PURPOSE_CRL_SIGN>, B<X509_PURPOSE_ANY>,
 190 B<X509_PURPOSE_OCSP_HELPER>, B<X509_PURPOSE_TIMESTAMP_SIGN> and
 191 B<X509_PURPOSE_CODE_SIGN>.  It is also
 192 possible to create a custom purpose value. Setting a purpose requests that
 193 the key usage and extended key usage (EKU) extensions optionally declared within
 194 the certificate and its chain are verified to be consistent with that purpose.
 195 For SSL client, SSL server, and S/MIME purposes, the EKU is checked also for the
 196 CA certificates along the chain, including any given trust anchor certificate.
 197 Potentially also further checks are done (depending on the purpose given).
 198 Every purpose also has an associated default trust value, which will also be set
 199 at the same time. During verification, this trust setting will be verified
 200 to check whether it is consistent with the trust set by the system administrator
 201 for certificates in the chain.
 202
 203 X509_STORE_CTX_set_trust() sets the trust value for the target certificate
 204 being verified in the I<ctx>. Built-in available values for the I<trust>
 205 argument are B<X509_TRUST_COMPAT>, B<X509_TRUST_SSL_CLIENT>,
 206 B<X509_TRUST_SSL_SERVER>, B<X509_TRUST_EMAIL>, B<X509_TRUST_OBJECT_SIGN>,
 207 B<X509_TRUST_OCSP_SIGN>, B<X509_TRUST_OCSP_REQUEST> and B<X509_TRUST_TSA>. It is
 208 also possible to create a custom trust value. Since X509_STORE_CTX_set_purpose()
 209 also sets the trust value it is normally sufficient to only call that function.
 210 If both are called then X509_STORE_CTX_set_trust() should be called after
 211 X509_STORE_CTX_set_purpose() since the trust setting of the last call will be
 212 used.
 213
 214 It should not normally be necessary for end user applications to call
 215 X509_STORE_CTX_purpose_inherit() directly. Typically applications should call
 216 X509_STORE_CTX_set_purpose() or X509_STORE_CTX_set_trust() instead. Using this
 217 function it is possible to set the purpose and trust values for the I<ctx> at
 218 the same time.
 219 Both I<ctx> and its internal verification parameter pointer must not be NULL.
 220 The I<def_purpose> and I<purpose> arguments can have the same
 221 purpose values as described for X509_STORE_CTX_set_purpose() above. The I<trust>
 222 argument can have the same trust values as described in
 223 X509_STORE_CTX_set_trust() above. Any of the I<def_purpose>, I<purpose> or
 224 I<trust> values may also have the value 0 to indicate that the supplied
 225 parameter should be ignored. After calling this function the purpose to be used
 226 for verification is set from the I<purpose> argument unless the purpose was
 227 already set in I<ctx> before, and the trust is set from the I<trust> argument
 228 unless the trust was already set in I<ctx> before.
 229 If I<trust> is 0 then the trust value will be set from
 230 the default trust value for I<purpose>. If the default trust value for the
 231 purpose is I<X509_TRUST_DEFAULT> and I<trust> is 0 then the default trust value
 232 associated with the I<def_purpose> value is used for the trust setting instead.
 233
 234 =head1 NOTES
 235
 236 The certificates and CRLs in a store are used internally and should B<not>
 237 be freed up until after the associated B<X509_STORE_CTX> is freed.
 238
 239 =head1 BUGS
 240
 241 The certificates and CRLs in a context are used internally and should B<not>
 242 be freed up until after the associated B<X509_STORE_CTX> is freed. Copies
 243 should be made or reference counts increased instead.
 244
 245 =head1 RETURN VALUES
 246
 247 X509_STORE_CTX_new() returns a newly allocated context or NULL if an
 248 error occurred.
 249
 250 X509_STORE_CTX_init() returns 1 for success or 0 if an error occurred.
 251
 252 X509_STORE_CTX_get0_param() returns a pointer to an B<X509_VERIFY_PARAM>
 253 structure or NULL if an error occurred.
 254
 255 X509_STORE_CTX_cleanup(), X509_STORE_CTX_free(),
 256 X509_STORE_CTX_set0_trusted_stack(),
 257 X509_STORE_CTX_set_cert(),
 258 X509_STORE_CTX_set0_crls() and X509_STORE_CTX_set0_param() do not return
 259 values.
 260
 261 X509_STORE_CTX_set_default() returns 1 for success or 0 if an error occurred.
 262
 263 X509_STORE_CTX_get_num_untrusted() returns the number of untrusted certificates
 264 used.
 265
 266 =head1 SEE ALSO
 267
 268 L<X509_verify_cert(3)>, L<X509_STORE_CTX_verify(3)>,
 269 L<X509_VERIFY_PARAM_set_flags(3)>
 270
 271 =head1 HISTORY
 272
 273 The X509_STORE_CTX_set0_crls() function was added in OpenSSL 1.0.0.
 274 The X509_STORE_CTX_get_num_untrusted() function was added in OpenSSL 1.1.0.
 275 The X509_STORE_CTX_new_ex() function was added in OpenSSL 3.0.
 276
 277 There is no need to call X509_STORE_CTX_cleanup() explicitly since OpenSSL 3.0.
 278
 279 =head1 COPYRIGHT
 280
 281 Copyright 2009-2022 The OpenSSL Project Authors. All Rights Reserved.
 282
 283 Licensed under the Apache License 2.0 (the "License").  You may not use
 284 this file except in compliance with the License.  You can obtain a copy
 285 in the file LICENSE in the source distribution or at
 286 L<https://www.openssl.org/source/license.html>.
 287
 288 =cut