doc/man3/X509_STORE_CTX_set_verify_cb.pod

   1 =pod
   2
   3 =head1 NAME
   4
   5 X509_STORE_CTX_get_cleanup,
   6 X509_STORE_CTX_get_lookup_crls,
   7 X509_STORE_CTX_get_lookup_certs,
   8 X509_STORE_CTX_get_check_policy,
   9 X509_STORE_CTX_get_cert_crl,
  10 X509_STORE_CTX_get_check_crl,
  11 X509_STORE_CTX_get_get_crl,
  12 X509_STORE_CTX_get_check_revocation,
  13 X509_STORE_CTX_get_check_issued,
  14 X509_STORE_CTX_get_get_issuer,
  15 X509_STORE_CTX_get_verify_cb,
  16 X509_STORE_CTX_set_verify_cb,
  17 X509_STORE_CTX_verify_cb
  18 - get and set verification callback
  19
  20 =head1 SYNOPSIS
  21
  22  #include <openssl/x509_vfy.h>
  23
  24  typedef int (*X509_STORE_CTX_verify_cb)(int, X509_STORE_CTX *);
  25
  26  X509_STORE_CTX_verify_cb X509_STORE_CTX_get_verify_cb(X509_STORE_CTX *ctx);
  27
  28  void X509_STORE_CTX_set_verify_cb(X509_STORE_CTX *ctx,
  29                                    X509_STORE_CTX_verify_cb verify_cb);
  30
  31  X509_STORE_CTX_get_issuer_fn X509_STORE_CTX_get_get_issuer(X509_STORE_CTX *ctx);
  32  X509_STORE_CTX_check_issued_fn X509_STORE_CTX_get_check_issued(X509_STORE_CTX *ctx);
  33  X509_STORE_CTX_check_revocation_fn X509_STORE_CTX_get_check_revocation(X509_STORE_CTX *ctx);
  34  X509_STORE_CTX_get_crl_fn X509_STORE_CTX_get_get_crl(X509_STORE_CTX *ctx);
  35  X509_STORE_CTX_check_crl_fn X509_STORE_CTX_get_check_crl(X509_STORE_CTX *ctx);
  36  X509_STORE_CTX_cert_crl_fn X509_STORE_CTX_get_cert_crl(X509_STORE_CTX *ctx);
  37  X509_STORE_CTX_check_policy_fn X509_STORE_CTX_get_check_policy(X509_STORE_CTX *ctx);
  38  X509_STORE_CTX_lookup_certs_fn X509_STORE_CTX_get_lookup_certs(X509_STORE_CTX *ctx);
  39  X509_STORE_CTX_lookup_crls_fn X509_STORE_CTX_get_lookup_crls(X509_STORE_CTX *ctx);
  40  X509_STORE_CTX_cleanup_fn X509_STORE_CTX_get_cleanup(X509_STORE_CTX *ctx);
  41
  42 =head1 DESCRIPTION
  43
  44 X509_STORE_CTX_set_verify_cb() sets the verification callback of B<ctx> to
  45 B<verify_cb> overwriting any existing callback.
  46
  47 The verification callback can be used to customise the operation of certificate
  48 verification, either by overriding error conditions or logging errors for
  49 debugging purposes.
  50
  51 However a verification callback is B<not> essential and the default operation
  52 is often sufficient.
  53
  54 The B<ok> parameter to the callback indicates the value the callback should
  55 return to retain the default behaviour. If it is zero then an error condition
  56 is indicated. If it is 1 then no error occurred. If the flag
  57 B<X509_V_FLAG_NOTIFY_POLICY> is set then B<ok> is set to 2 to indicate the
  58 policy checking is complete.
  59
  60 The B<ctx> parameter to the callback is the B<X509_STORE_CTX> structure that
  61 is performing the verification operation. A callback can examine this
  62 structure and receive additional information about the error, for example
  63 by calling X509_STORE_CTX_get_current_cert(). Additional application data can
  64 be passed to the callback via the B<ex_data> mechanism.
  65
  66 X509_STORE_CTX_get_verify_cb() returns the value of the current callback
  67 for the specific B<ctx>.
  68
  69 X509_STORE_CTX_get_get_issuer(),
  70 X509_STORE_CTX_get_check_issued(), X509_STORE_CTX_get_check_revocation(),
  71 X509_STORE_CTX_get_get_crl(), X509_STORE_CTX_get_check_crl(),
  72 X509_STORE_CTX_get_cert_crl(), X509_STORE_CTX_get_check_policy(),
  73 X509_STORE_CTX_get_lookup_certs(), X509_STORE_CTX_get_lookup_crls()
  74 and X509_STORE_CTX_get_cleanup() return the function pointers cached
  75 from the corresponding B<X509_STORE>, please see
  76 L<X509_STORE_set_verify(3)> for more information.
  77
  78
  79 =head1 WARNING
  80
  81 In general a verification callback should B<NOT> unconditionally return 1 in
  82 all circumstances because this will allow verification to succeed no matter
  83 what the error. This effectively removes all security from the application
  84 because B<any> certificate (including untrusted generated ones) will be
  85 accepted.
  86
  87 =head1 NOTES
  88
  89 The verification callback can be set and inherited from the parent structure
  90 performing the operation. In some cases (such as S/MIME verification) the
  91 B<X509_STORE_CTX> structure is created and destroyed internally and the
  92 only way to set a custom verification callback is by inheriting it from the
  93 associated B<X509_STORE>.
  94
  95 =head1 RETURN VALUES
  96
  97 X509_STORE_CTX_set_verify_cb() does not return a value.
  98
  99 =head1 EXAMPLES
 100
 101 Default callback operation:
 102
 103  int verify_callback(int ok, X509_STORE_CTX *ctx) {
 104      return ok;
 105  }
 106
 107 Simple example, suppose a certificate in the chain is expired and we wish
 108 to continue after this error:
 109
 110  int verify_callback(int ok, X509_STORE_CTX *ctx) {
 111      /* Tolerate certificate expiration */
 112      if (X509_STORE_CTX_get_error(ctx) == X509_V_ERR_CERT_HAS_EXPIRED)
 113          return 1;
 114      /* Otherwise don't override */
 115      return ok;
 116  }
 117
 118 More complex example, we don't wish to continue after B<any> certificate has
 119 expired just one specific case:
 120
 121  int verify_callback(int ok, X509_STORE_CTX *ctx)
 122  {
 123      int err = X509_STORE_CTX_get_error(ctx);
 124      X509 *err_cert = X509_STORE_CTX_get_current_cert(ctx);
 125
 126      if (err == X509_V_ERR_CERT_HAS_EXPIRED) {
 127          if (check_is_acceptable_expired_cert(err_cert)
 128              return 1;
 129      }
 130      return ok;
 131  }
 132
 133 Full featured logging callback. In this case the B<bio_err> is assumed to be
 134 a global logging B<BIO>, an alternative would to store a BIO in B<ctx> using
 135 B<ex_data>.
 136
 137  int verify_callback(int ok, X509_STORE_CTX *ctx)
 138  {
 139      X509 *err_cert;
 140      int err, depth;
 141
 142      err_cert = X509_STORE_CTX_get_current_cert(ctx);
 143      err = X509_STORE_CTX_get_error(ctx);
 144      depth = X509_STORE_CTX_get_error_depth(ctx);
 145
 146      BIO_printf(bio_err, "depth=%d ", depth);
 147      if (err_cert) {
 148          X509_NAME_print_ex(bio_err, X509_get_subject_name(err_cert),
 149                             0, XN_FLAG_ONELINE);
 150          BIO_puts(bio_err, "\n");
 151      }
 152      else
 153          BIO_puts(bio_err, "<no cert>\n");
 154      if (!ok)
 155          BIO_printf(bio_err, "verify error:num=%d:%s\n", err,
 156                     X509_verify_cert_error_string(err));
 157      switch (err) {
 158      case X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT:
 159          BIO_puts(bio_err, "issuer= ");
 160          X509_NAME_print_ex(bio_err, X509_get_issuer_name(err_cert),
 161                             0, XN_FLAG_ONELINE);
 162          BIO_puts(bio_err, "\n");
 163          break;
 164      case X509_V_ERR_CERT_NOT_YET_VALID:
 165      case X509_V_ERR_ERROR_IN_CERT_NOT_BEFORE_FIELD:
 166          BIO_printf(bio_err, "notBefore=");
 167          ASN1_TIME_print(bio_err, X509_get_notBefore(err_cert));
 168          BIO_printf(bio_err, "\n");
 169          break;
 170      case X509_V_ERR_CERT_HAS_EXPIRED:
 171      case X509_V_ERR_ERROR_IN_CERT_NOT_AFTER_FIELD:
 172          BIO_printf(bio_err, "notAfter=");
 173          ASN1_TIME_print(bio_err, X509_get_notAfter(err_cert));
 174          BIO_printf(bio_err, "\n");
 175          break;
 176      case X509_V_ERR_NO_EXPLICIT_POLICY:
 177          policies_print(bio_err, ctx);
 178          break;
 179      }
 180      if (err == X509_V_OK && ok == 2)
 181          /* print out policies */
 182
 183      BIO_printf(bio_err, "verify return:%d\n", ok);
 184      return(ok);
 185  }
 186
 187 =head1 SEE ALSO
 188
 189 L<X509_STORE_CTX_get_error(3)>
 190 L<X509_STORE_set_verify_cb_func(3)>
 191 L<X509_STORE_CTX_get_ex_new_index(3)>
 192
 193 =head1 HISTORY
 194
 195 The
 196 X509_STORE_CTX_get_get_issuer(),
 197 X509_STORE_CTX_get_check_issued(), X509_STORE_CTX_get_check_revocation(),
 198 X509_STORE_CTX_get_get_crl(), X509_STORE_CTX_get_check_crl(),
 199 X509_STORE_CTX_get_cert_crl(), X509_STORE_CTX_get_check_policy(),
 200 X509_STORE_CTX_get_lookup_certs(), X509_STORE_CTX_get_lookup_crls()
 201 and X509_STORE_CTX_get_cleanup() functions were added in OpenSSL 1.1.0.
 202
 203 =head1 COPYRIGHT
 204
 205 Copyright 2009-2016 The OpenSSL Project Authors. All Rights Reserved.
 206
 207 Licensed under the Apache License 2.0 (the "License").  You may not use
 208 this file except in compliance with the License.  You can obtain a copy
 209 in the file LICENSE in the source distribution or at
 210 L<https://www.openssl.org/source/license.html>.
 211
 212 =cut