=pod

=head1 NAME

X509_check_host, X509_check_email, X509_check_ip, X509_check_ip_asc - X.509 certificate matching

=head1 SYNOPSIS

 #include <openssl/x509.h>

 int X509_check_host(X509 *, const unsigned char *name,
                     size_t namelen, unsigned int flags);
 int X509_check_email(X509 *, const unsigned char *address,
                     size_t addresslen, unsigned int flags);
 int X509_check_ip(X509 *, const unsigned char *address,
                   size_t addresslen, unsigned int flags);
 int X509_check_ip_asc(X509 *, const char *address, unsigned int flags);

=head1 DESCRIPTION

The certificate matching functions are intended to be called to check
if a certificate matches a given host name, email address, or IP
address.  The validity of the certificate and its trust level has to
be checked by other means.

X509_check_host() checks if the certificate matches the specified
host name, which must be encoded in the preferred name syntax
described in section 3.5 of RFC 1034. The B<namelen> argument must be
the number of characters in the name string or zero in which case the
length is calculated with strlen(name).

X509_check_email() checks if the certificate matches the specified
email address.  Only the mailbox syntax of RFC 822 is supported,
comments are not allowed, and no attempt is made to normalize quoted
characters.  The B<addresslen> argument must be the number of
characters in the address string. The B<namelen> argument must be
the number of characters in the name string or zero in which case the
length is calculated with strlen(name).

X509_check_ip() checks if the certificate matches a specified IPv4 or
IPv6 address.  The B<address> array is in binary format, in network
byte order.  The length is either 4 (IPv4) or 16 (IPv6).  Only
explicitly marked addresses in the certificates are considered; IP
addresses stored in DNS names and Common Names are ignored.

X509_check_ip_asc() is similar, except that the NUL-terminated
string B<address> is first converted to the internal representation.

The B<flags> argument is usually 0.  It can be the bitwise OR of the
flags B<X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT>,
B<X509_CHECK_FLAG_NO_WILDCARDS>.

The B<X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT> flag causes the function
to check the subject DN even if the certificate contains a subject
alternative name extension is present; the default is to ignore the
subject DN in preference of the extension.

If present, B<X509_CHECK_FLAG_NO_WILDCARDS> disables wildcard
expansion; this only applies to B<X509_check_host>.

=head1 RETURN VALUES

The functions return 1 for a successful match, 0 for a failed match
and -1 for an internal error: typically a memory allocation failure.

X509_check_ip_asc() can also return -2 if the IP address string is malformed.

=head1 SEE ALSO

L<SSL_get_verify_result(3)|SSL_get_verify_result(3)>

=head1 HISTORY

These functions were added in OpenSSL 1.1.0.

=cut
