1=pod 2 3=head1 NAME 4 5X509_check_host, X509_check_email, X509_check_ip, X509_check_ip_asc - X.509 certificate matching 6 7=head1 SYNOPSIS 8 9 #include <openssl/x509v3.h> 10 11 int X509_check_host(X509 *, const char *name, size_t namelen, 12 unsigned int flags, char **peername); 13 int X509_check_email(X509 *, const char *address, size_t addresslen, 14 unsigned int flags); 15 int X509_check_ip(X509 *, const unsigned char *address, size_t addresslen, 16 unsigned int flags); 17 int X509_check_ip_asc(X509 *, const char *address, unsigned int flags); 18 19=head1 DESCRIPTION 20 21The certificate matching functions are used to check whether a 22certificate matches a given hostname, email address, or IP address. 23The validity of the certificate and its trust level has to be checked by 24other means. 25 26X509_check_host() checks if the certificate Subject Alternative 27Name (SAN) or Subject CommonName (CN) matches the specified hostname, 28which must be encoded in the preferred name syntax described 29in section 3.5 of RFC 1034. By default, wildcards are supported 30and they match only in the left-most label; but they may match 31part of that label with an explicit prefix or suffix. For example, 32by default, the host B<name> "www.example.com" would match a 33certificate with a SAN or CN value of "*.example.com", "w*.example.com" 34or "*w.example.com". 35 36Per section 6.4.2 of RFC 6125, B<name> values representing international 37domain names must be given in A-label form. The B<namelen> argument 38must be the number of characters in the name string or zero in which 39case the length is calculated with strlen(B<name>). When B<name> starts 40with a dot (e.g. ".example.com"), it will be matched by a certificate 41valid for any sub-domain of B<name>, (see also 42B<X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS> below). 43 44When the certificate is matched, and B<peername> is not NULL, a 45pointer to a copy of the matching SAN or CN from the peer certificate 46is stored at the address passed in B<peername>. The application 47is responsible for freeing the peername via OPENSSL_free() when it 48is no longer needed. 49 50X509_check_email() checks if the certificate matches the specified 51email B<address>. Only the mailbox syntax of RFC 822 is supported, 52comments are not allowed, and no attempt is made to normalize quoted 53characters. The B<addresslen> argument must be the number of 54characters in the address string or zero in which case the length 55is calculated with strlen(B<address>). 56 57X509_check_ip() checks if the certificate matches a specified IPv4 or 58IPv6 address. The B<address> array is in binary format, in network 59byte order. The length is either 4 (IPv4) or 16 (IPv6). Only 60explicitly marked addresses in the certificates are considered; IP 61addresses stored in DNS names and Common Names are ignored. 62 63X509_check_ip_asc() is similar, except that the NUL-terminated 64string B<address> is first converted to the internal representation. 65 66The B<flags> argument is usually 0. It can be the bitwise OR of the 67flags: 68 69=over 4 70 71=item B<X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT>, 72 73=item B<X509_CHECK_FLAG_NEVER_CHECK_SUBJECT>, 74 75=item B<X509_CHECK_FLAG_NO_WILDCARDS>, 76 77=item B<X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS>, 78 79=item B<X509_CHECK_FLAG_MULTI_LABEL_WILDCARDS>. 80 81=item B<X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS>. 82 83=back 84 85The B<X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT> flag causes the function 86to consider the subject DN even if the certificate contains at least 87one subject alternative name of the right type (DNS name or email 88address as appropriate); the default is to ignore the subject DN 89when at least one corresponding subject alternative names is present. 90 91The B<X509_CHECK_FLAG_NEVER_CHECK_SUBJECT> flag causes the function to never 92consider the subject DN even if the certificate contains no subject alternative 93names of the right type (DNS name or email address as appropriate); the default 94is to use the subject DN when no corresponding subject alternative names are 95present. 96If both B<X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT> and 97B<X509_CHECK_FLAG_NEVER_CHECK_SUBJECT> are specified, the latter takes 98precedence and the subject DN is not checked for matching names. 99 100If set, B<X509_CHECK_FLAG_NO_WILDCARDS> disables wildcard 101expansion; this only applies to B<X509_check_host>. 102 103If set, B<X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS> suppresses support 104for "*" as wildcard pattern in labels that have a prefix or suffix, 105such as: "www*" or "*www"; this only applies to B<X509_check_host>. 106 107If set, B<X509_CHECK_FLAG_MULTI_LABEL_WILDCARDS> allows a "*" that 108constitutes the complete label of a DNS name (e.g. "*.example.com") 109to match more than one label in B<name>; this flag only applies 110to B<X509_check_host>. 111 112If set, B<X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS> restricts B<name> 113values which start with ".", that would otherwise match any sub-domain 114in the peer certificate, to only match direct child sub-domains. 115Thus, for instance, with this flag set a B<name> of ".example.com" 116would match a peer certificate with a DNS name of "www.example.com", 117but would not match a peer certificate with a DNS name of 118"www.sub.example.com"; this flag only applies to B<X509_check_host>. 119 120=head1 RETURN VALUES 121 122The functions return 1 for a successful match, 0 for a failed match 123and -1 for an internal error: typically a memory allocation failure 124or an ASN.1 decoding error. 125 126All functions can also return -2 if the input is malformed. For example, 127X509_check_host() returns -2 if the provided B<name> contains embedded 128NULs. 129 130=head1 NOTES 131 132Applications are encouraged to use X509_VERIFY_PARAM_set1_host() 133rather than explicitly calling L<X509_check_host(3)>. Host name 134checks may be out of scope with the DANE-EE(3) certificate usage, 135and the internal checks will be suppressed as appropriate when 136DANE support is enabled. 137 138=head1 SEE ALSO 139 140L<SSL_get_verify_result(3)>, 141L<X509_VERIFY_PARAM_set1_host(3)>, 142L<X509_VERIFY_PARAM_add1_host(3)>, 143L<X509_VERIFY_PARAM_set1_email(3)>, 144L<X509_VERIFY_PARAM_set1_ip(3)>, 145L<X509_VERIFY_PARAM_set1_ipasc(3)> 146 147=head1 HISTORY 148 149These functions were added in OpenSSL 1.0.2. 150 151=head1 COPYRIGHT 152 153Copyright 2012-2020 The OpenSSL Project Authors. All Rights Reserved. 154 155Licensed under the OpenSSL license (the "License"). You may not use 156this file except in compliance with the License. You can obtain a copy 157in the file LICENSE in the source distribution or at 158L<https://www.openssl.org/source/license.html>. 159 160=cut 161