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/x509.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 host name, 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 host 28name, which 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_NO_WILDCARDS>, 74 75=item B<X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS>, 76 77=item B<X509_CHECK_FLAG_MULTI_LABEL_WILDCARDS>. 78 79=item B<X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS>. 80 81=back 82 83The B<X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT> flag causes the function 84to consider the subject DN even if the certificate contains at least 85one subject alternative name of the right type (DNS name or email 86address as appropriate); the default is to ignore the subject DN 87when at least one corresponding subject alternative names is present. 88 89If set, B<X509_CHECK_FLAG_NO_WILDCARDS> disables wildcard 90expansion; this only applies to B<X509_check_host>. 91 92If set, B<X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS> suppresses support 93for "*" as wildcard pattern in labels that have a prefix or suffix, 94such as: "www*" or "*www"; this only aplies to B<X509_check_host>. 95 96If set, B<X509_CHECK_FLAG_MULTI_LABEL_WILDCARDS> allows a "*" that 97constitutes the complete label of a DNS name (e.g. "*.example.com") 98to match more than one label in B<name>; this flag only applies 99to B<X509_check_host>. 100 101If set, B<X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS> restricts B<name> 102values which start with ".", that would otherwise match any sub-domain 103in the peer certificate, to only match direct child sub-domains. 104Thus, for instance, with this flag set a B<name> of ".example.com" 105would match a peer certificate with a DNS name of "www.example.com", 106but would not match a peer certificate with a DNS name of 107"www.sub.example.com"; this flag only applies to B<X509_check_host>. 108 109=head1 RETURN VALUES 110 111The functions return 1 for a successful match, 0 for a failed match 112and -1 for an internal error: typically a memory allocation failure 113or an ASN.1 decoding error. 114 115All functions can also return -2 if the input is malformed. For example, 116X509_check_host() returns -2 if the provided B<name> contains embedded 117NULs. 118 119=head1 NOTES 120 121Applications are encouraged to use X509_VERIFY_PARAM_set1_host() 122rather than explicitly calling L<X509_check_host(3)>. Host name 123checks are out of scope with the DANE-EE(3) certificate usage, 124and the internal checks will be suppressed as appropriate when 125DANE support is added to OpenSSL. 126 127=head1 SEE ALSO 128 129L<SSL_get_verify_result(3)|SSL_get_verify_result(3)>, 130L<X509_VERIFY_PARAM_set1_host(3)|X509_VERIFY_PARAM_set1_host(3)>, 131L<X509_VERIFY_PARAM_add1_host(3)|X509_VERIFY_PARAM_add1_host(3)>, 132L<X509_VERIFY_PARAM_set1_email(3)|X509_VERIFY_PARAM_set1_email(3)>, 133L<X509_VERIFY_PARAM_set1_ip(3)|X509_VERIFY_PARAM_set1_ip(3)>, 134L<X509_VERIFY_PARAM_set1_ipasc(3)|X509_VERIFY_PARAM_set1_ipasc(3)> 135 136=head1 HISTORY 137 138These functions were added in OpenSSL 1.1.0. 139 140=cut 141