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>. The mailbox syntax of RFC 822 is supported, 52comments are not allowed, and no attempt is made to normalize quoted 53characters. The mailbox syntax of RFC 6531 is supported for 54SmtpUTF8Mailbox address in subjectAltName according to RFC 8398, 55with similar limitations as for RFC 822 syntax, and no attempt 56is made to convert from A-label to U-label before comparison. 57The B<addresslen> argument must be the number of 58characters in the address string or zero in which case the length 59is calculated with strlen(B<address>). 60 61X509_check_ip() checks if the certificate matches a specified IPv4 or 62IPv6 address. The B<address> array is in binary format, in network 63byte order. The length is either 4 (IPv4) or 16 (IPv6). Only 64explicitly marked addresses in the certificates are considered; IP 65addresses stored in DNS names and Common Names are ignored. There are 66currently no B<flags> that would affect the behavior of this call. 67 68X509_check_ip_asc() is similar, except that the NUL-terminated 69string B<address> is first converted to the internal representation. 70 71The B<flags> argument is usually 0. It can be the bitwise OR of the 72flags: 73 74=over 4 75 76=item B<X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT>, 77 78=item B<X509_CHECK_FLAG_NEVER_CHECK_SUBJECT>, 79 80=item B<X509_CHECK_FLAG_NO_WILDCARDS>, 81 82=item B<X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS>, 83 84=item B<X509_CHECK_FLAG_MULTI_LABEL_WILDCARDS>. 85 86=item B<X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS>. 87 88=back 89 90The B<X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT> flag causes the function 91to consider the subject DN even if the certificate contains at least 92one subject alternative name of the right type (DNS name or email 93address as appropriate); the default is to ignore the subject DN 94when at least one corresponding subject alternative names is present. 95 96The B<X509_CHECK_FLAG_NEVER_CHECK_SUBJECT> flag causes the function to never 97consider the subject DN even if the certificate contains no subject alternative 98names of the right type (DNS name or email address as appropriate); the default 99is to use the subject DN when no corresponding subject alternative names are 100present. 101If both B<X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT> and 102B<X509_CHECK_FLAG_NEVER_CHECK_SUBJECT> are specified, the latter takes 103precedence and the subject DN is not checked for matching names. 104 105If set, B<X509_CHECK_FLAG_NO_WILDCARDS> disables wildcard 106expansion; this only applies to B<X509_check_host>. 107 108If set, B<X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS> suppresses support 109for "*" as wildcard pattern in labels that have a prefix or suffix, 110such as: "www*" or "*www"; this only applies to B<X509_check_host>. 111 112If set, B<X509_CHECK_FLAG_MULTI_LABEL_WILDCARDS> allows a "*" that 113constitutes the complete label of a DNS name (e.g. "*.example.com") 114to match more than one label in B<name>; this flag only applies 115to B<X509_check_host>. 116 117If set, B<X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS> restricts B<name> 118values which start with ".", that would otherwise match any sub-domain 119in the peer certificate, to only match direct child sub-domains. 120Thus, for instance, with this flag set a B<name> of ".example.com" 121would match a peer certificate with a DNS name of "www.example.com", 122but would not match a peer certificate with a DNS name of 123"www.sub.example.com"; this flag only applies to B<X509_check_host>. 124 125=head1 RETURN VALUES 126 127The functions return 1 for a successful match, 0 for a failed match 128and -1 for an internal error: typically a memory allocation failure 129or an ASN.1 decoding error. 130 131All functions can also return -2 if the input is malformed. For example, 132X509_check_host() returns -2 if the provided B<name> contains embedded 133NULs. 134 135=head1 NOTES 136 137Applications are encouraged to use X509_VERIFY_PARAM_set1_host() 138rather than explicitly calling L<X509_check_host(3)>. Hostname 139checks may be out of scope with the DANE-EE(3) certificate usage, 140and the internal checks will be suppressed as appropriate when 141DANE support is enabled. 142 143=head1 SEE ALSO 144 145L<SSL_get_verify_result(3)>, 146L<X509_VERIFY_PARAM_set1_host(3)>, 147L<X509_VERIFY_PARAM_add1_host(3)>, 148L<X509_VERIFY_PARAM_set1_email(3)>, 149L<X509_VERIFY_PARAM_set1_ip(3)> 150 151=head1 HISTORY 152 153These functions were added in OpenSSL 1.0.2. 154 155=head1 COPYRIGHT 156 157Copyright 2012-2022 The OpenSSL Project Authors. All Rights Reserved. 158 159Licensed under the Apache License 2.0 (the "License"). You may not use 160this file except in compliance with the License. You can obtain a copy 161in the file LICENSE in the source distribution or at 162L<https://www.openssl.org/source/license.html>. 163 164=cut 165