X509_check_host.pod 6.3 KB

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  1. =pod
  2. =head1 NAME
  3. X509_check_host, X509_check_email, X509_check_ip, X509_check_ip_asc - X.509 certificate matching
  4. =head1 SYNOPSIS
  5. #include <openssl/x509v3.h>
  6. int X509_check_host(X509 *, const char *name, size_t namelen,
  7. unsigned int flags, char **peername);
  8. int X509_check_email(X509 *, const char *address, size_t addresslen,
  9. unsigned int flags);
  10. int X509_check_ip(X509 *, const unsigned char *address, size_t addresslen,
  11. unsigned int flags);
  12. int X509_check_ip_asc(X509 *, const char *address, unsigned int flags);
  13. =head1 DESCRIPTION
  14. The certificate matching functions are used to check whether a
  15. certificate matches a given hostname, email address, or IP address.
  16. The validity of the certificate and its trust level has to be checked by
  17. other means.
  18. X509_check_host() checks if the certificate Subject Alternative
  19. Name (SAN) or Subject CommonName (CN) matches the specified host
  20. name, which must be encoded in the preferred name syntax described
  21. in section 3.5 of RFC 1034. By default, wildcards are supported
  22. and they match only in the left-most label; but they may match
  23. part of that label with an explicit prefix or suffix. For example,
  24. by default, the host B<name> "www.example.com" would match a
  25. certificate with a SAN or CN value of "*.example.com", "w*.example.com"
  26. or "*w.example.com".
  27. Per section 6.4.2 of RFC 6125, B<name> values representing international
  28. domain names must be given in A-label form. The B<namelen> argument
  29. must be the number of characters in the name string or zero in which
  30. case the length is calculated with strlen(B<name>). When B<name> starts
  31. with a dot (e.g ".example.com"), it will be matched by a certificate
  32. valid for any sub-domain of B<name>, (see also
  33. B<X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS> below).
  34. When the certificate is matched, and B<peername> is not NULL, a
  35. pointer to a copy of the matching SAN or CN from the peer certificate
  36. is stored at the address passed in B<peername>. The application
  37. is responsible for freeing the peername via OPENSSL_free() when it
  38. is no longer needed.
  39. X509_check_email() checks if the certificate matches the specified
  40. email B<address>. Only the mailbox syntax of RFC 822 is supported,
  41. comments are not allowed, and no attempt is made to normalize quoted
  42. characters. The B<addresslen> argument must be the number of
  43. characters in the address string or zero in which case the length
  44. is calculated with strlen(B<address>).
  45. X509_check_ip() checks if the certificate matches a specified IPv4 or
  46. IPv6 address. The B<address> array is in binary format, in network
  47. byte order. The length is either 4 (IPv4) or 16 (IPv6). Only
  48. explicitly marked addresses in the certificates are considered; IP
  49. addresses stored in DNS names and Common Names are ignored.
  50. X509_check_ip_asc() is similar, except that the NUL-terminated
  51. string B<address> is first converted to the internal representation.
  52. The B<flags> argument is usually 0. It can be the bitwise OR of the
  53. flags:
  54. =over 4
  55. =item B<X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT>,
  56. =item B<X509_CHECK_FLAG_NEVER_CHECK_SUBJECT>,
  57. =item B<X509_CHECK_FLAG_NO_WILDCARDS>,
  58. =item B<X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS>,
  59. =item B<X509_CHECK_FLAG_MULTI_LABEL_WILDCARDS>.
  60. =item B<X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS>.
  61. =back
  62. The B<X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT> flag causes the function
  63. to consider the subject DN even if the certificate contains at least
  64. one subject alternative name of the right type (DNS name or email
  65. address as appropriate); the default is to ignore the subject DN
  66. when at least one corresponding subject alternative names is present.
  67. The B<X509_CHECK_FLAG_NEVER_CHECK_SUBJECT> flag causes the function to never
  68. consider the subject DN even if the certificate contains no subject alternative
  69. names of the right type (DNS name or email address as appropriate); the default
  70. is to use the subject DN when no corresponding subject alternative names are
  71. present.
  72. If both B<X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT> and
  73. B<X509_CHECK_FLAG_NEVER_CHECK_SUBJECT> are specified, the latter takes
  74. precedence and the subject DN is not checked for matching names.
  75. If set, B<X509_CHECK_FLAG_NO_WILDCARDS> disables wildcard
  76. expansion; this only applies to B<X509_check_host>.
  77. If set, B<X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS> suppresses support
  78. for "*" as wildcard pattern in labels that have a prefix or suffix,
  79. such as: "www*" or "*www"; this only applies to B<X509_check_host>.
  80. If set, B<X509_CHECK_FLAG_MULTI_LABEL_WILDCARDS> allows a "*" that
  81. constitutes the complete label of a DNS name (e.g. "*.example.com")
  82. to match more than one label in B<name>; this flag only applies
  83. to B<X509_check_host>.
  84. If set, B<X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS> restricts B<name>
  85. values which start with ".", that would otherwise match any sub-domain
  86. in the peer certificate, to only match direct child sub-domains.
  87. Thus, for instance, with this flag set a B<name> of ".example.com"
  88. would match a peer certificate with a DNS name of "www.example.com",
  89. but would not match a peer certificate with a DNS name of
  90. "www.sub.example.com"; this flag only applies to B<X509_check_host>.
  91. =head1 RETURN VALUES
  92. The functions return 1 for a successful match, 0 for a failed match
  93. and -1 for an internal error: typically a memory allocation failure
  94. or an ASN.1 decoding error.
  95. All functions can also return -2 if the input is malformed. For example,
  96. X509_check_host() returns -2 if the provided B<name> contains embedded
  97. NULs.
  98. =head1 NOTES
  99. Applications are encouraged to use X509_VERIFY_PARAM_set1_host()
  100. rather than explicitly calling L<X509_check_host(3)>. Hostname
  101. checks may be out of scope with the DANE-EE(3) certificate usage,
  102. and the internal checks will be suppressed as appropriate when
  103. DANE support is enabled.
  104. =head1 SEE ALSO
  105. L<SSL_get_verify_result(3)>,
  106. L<X509_VERIFY_PARAM_set1_host(3)>,
  107. L<X509_VERIFY_PARAM_add1_host(3)>,
  108. L<X509_VERIFY_PARAM_set1_email(3)>,
  109. L<X509_VERIFY_PARAM_set1_ip(3)>,
  110. L<X509_VERIFY_PARAM_set1_ipasc(3)>
  111. =head1 HISTORY
  112. These functions were added in OpenSSL 1.0.2.
  113. =head1 COPYRIGHT
  114. Copyright 2012-2018 The OpenSSL Project Authors. All Rights Reserved.
  115. Licensed under the Apache License 2.0 (the "License"). You may not use
  116. this file except in compliance with the License. You can obtain a copy
  117. in the file LICENSE in the source distribution or at
  118. L<https://www.openssl.org/source/license.html>.
  119. =cut