doc/man3/X509_check_host.pod - third_party/openssl - Git at Google

 =pod

 =head1 NAME

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

 =head1 SYNOPSIS

  #include <openssl/x509v3.h>

  int X509_check_host(X509 *, const char *name, size_t namelen,
                      unsigned int flags, char **peername);
  int X509_check_email(X509 *, const 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 used to check whether a
 certificate matches a given hostname, 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 Subject Alternative
 Name (SAN) or Subject CommonName (CN) matches the specified hostname,
 which must be encoded in the preferred name syntax described
 in section 3.5 of RFC 1034.  By default, wildcards are supported
 and they match  only in the left-most label; but they may match
 part of that label with an explicit prefix or suffix.  For example,
 by default, the host B<name> "www.example.com" would match a
 certificate with a SAN or CN value of "*.example.com", "w*.example.com"
 or "*w.example.com".

 Per section 6.4.2 of RFC 6125, B<name> values representing international
 domain names must be given in A-label form.  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(B<name>).  When B<name> starts
 with a dot (e.g. ".example.com"), it will be matched by a certificate
 valid for any sub-domain of B<name>, (see also
 B<X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS> below).

 When the certificate is matched, and B<peername> is not NULL, a
 pointer to a copy of the matching SAN or CN from the peer certificate
 is stored at the address passed in B<peername>.  The application
 is responsible for freeing the peername via OPENSSL_free() when it
 is no longer needed.

 X509_check_email() checks if the certificate matches the specified
 email B<address>. The mailbox syntax of RFC 822 is supported,
 comments are not allowed, and no attempt is made to normalize quoted
 characters. The mailbox syntax of RFC 6531 is supported for
 SmtpUTF8Mailbox address in subjectAltName according to RFC 8398,
 with similar limitations as for RFC 822 syntax, and no attempt
 is made to convert from A-label to U-label before comparison.
 The B<addresslen> argument must be the number of
 characters in the address string or zero in which case the length
 is calculated with strlen(B<address>).

 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. There are
 currently no B<flags> that would affect the behavior of this call.

 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:

 =over 4

 =item B<X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT>,

 =item B<X509_CHECK_FLAG_NEVER_CHECK_SUBJECT>,

 =item B<X509_CHECK_FLAG_NO_WILDCARDS>,

 =item B<X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS>,

 =item B<X509_CHECK_FLAG_MULTI_LABEL_WILDCARDS>.

 =item B<X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS>.

 =back

 The B<X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT> flag causes the function
 to consider the subject DN even if the certificate contains at least
 one subject alternative name of the right type (DNS name or email
 address as appropriate); the default is to ignore the subject DN
 when at least one corresponding subject alternative names is present.

 The B<X509_CHECK_FLAG_NEVER_CHECK_SUBJECT> flag causes the function to never
 consider the subject DN even if the certificate contains no subject alternative
 names of the right type (DNS name or email address as appropriate); the default
 is to use the subject DN when no corresponding subject alternative names are
 present.
 If both B<X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT> and
 B<X509_CHECK_FLAG_NEVER_CHECK_SUBJECT> are specified, the latter takes
 precedence and the subject DN is not checked for matching names.

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

 If set, B<X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS> suppresses support
 for "*" as wildcard pattern in labels that have a prefix or suffix,
 such as: "www*" or "*www"; this only applies to B<X509_check_host>.

 If set, B<X509_CHECK_FLAG_MULTI_LABEL_WILDCARDS> allows a "*" that
 constitutes the complete label of a DNS name (e.g. "*.example.com")
 to match more than one label in B<name>; this flag only applies
 to B<X509_check_host>.

 If set, B<X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS> restricts B<name>
 values which start with ".", that would otherwise match any sub-domain
 in the peer certificate, to only match direct child sub-domains.
 Thus, for instance, with this flag set a B<name> of ".example.com"
 would match a peer certificate with a DNS name of "www.example.com",
 but would not match a peer certificate with a DNS name of
 "www.sub.example.com"; this flag 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
 or an ASN.1 decoding error.

 All functions can also return -2 if the input is malformed. For example,
 X509_check_host() returns -2 if the provided B<name> contains embedded
 NULs.

 =head1 NOTES

 Applications are encouraged to use X509_VERIFY_PARAM_set1_host()
 rather than explicitly calling L<X509_check_host(3)>. Hostname
 checks may be out of scope with the DANE-EE(3) certificate usage,
 and the internal checks will be suppressed as appropriate when
 DANE support is enabled.

 =head1 SEE ALSO

 L<SSL_get_verify_result(3)>,
 L<X509_VERIFY_PARAM_set1_host(3)>,
 L<X509_VERIFY_PARAM_add1_host(3)>,
 L<X509_VERIFY_PARAM_set1_email(3)>,
 L<X509_VERIFY_PARAM_set1_ip(3)>

 =head1 HISTORY

 These functions were added in OpenSSL 1.0.2.

 =head1 COPYRIGHT

 Copyright 2012-2021 The OpenSSL Project Authors. All Rights Reserved.

 Licensed under the Apache License 2.0 (the "License").  You may not use
 this file except in compliance with the License.  You can obtain a copy
 in the file LICENSE in the source distribution or at
 L<https://www.openssl.org/source/license.html>.

 =cut
	=pod

	=head1 NAME

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

	=head1 SYNOPSIS

	#include <openssl/x509v3.h>

	int X509_check_host(X509 , const char name, size_t namelen,
	unsigned int flags, char **peername);
	int X509_check_email(X509 , const 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 used to check whether a
	certificate matches a given hostname, 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 Subject Alternative
	Name (SAN) or Subject CommonName (CN) matches the specified hostname,
	which must be encoded in the preferred name syntax described
	in section 3.5 of RFC 1034. By default, wildcards are supported
	and they match only in the left-most label; but they may match
	part of that label with an explicit prefix or suffix. For example,
	by default, the host B<name> "www.example.com" would match a
	certificate with a SAN or CN value of ".example.com", "w.example.com"
	or "*w.example.com".

	Per section 6.4.2 of RFC 6125, B<name> values representing international
	domain names must be given in A-label form. 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(B<name>). When B<name> starts
	with a dot (e.g. ".example.com"), it will be matched by a certificate
	valid for any sub-domain of B<name>, (see also
	B<X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS> below).

	When the certificate is matched, and B<peername> is not NULL, a
	pointer to a copy of the matching SAN or CN from the peer certificate
	is stored at the address passed in B<peername>. The application
	is responsible for freeing the peername via OPENSSL_free() when it
	is no longer needed.

	X509_check_email() checks if the certificate matches the specified
	email B<address>. The mailbox syntax of RFC 822 is supported,
	comments are not allowed, and no attempt is made to normalize quoted
	characters. The mailbox syntax of RFC 6531 is supported for
	SmtpUTF8Mailbox address in subjectAltName according to RFC 8398,
	with similar limitations as for RFC 822 syntax, and no attempt
	is made to convert from A-label to U-label before comparison.
	The B<addresslen> argument must be the number of
	characters in the address string or zero in which case the length
	is calculated with strlen(B<address>).

	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. There are
	currently no B<flags> that would affect the behavior of this call.

	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:

	=over 4

	=item B<X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT>,

	=item B<X509_CHECK_FLAG_NEVER_CHECK_SUBJECT>,

	=item B<X509_CHECK_FLAG_NO_WILDCARDS>,

	=item B<X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS>,

	=item B<X509_CHECK_FLAG_MULTI_LABEL_WILDCARDS>.

	=item B<X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS>.

	=back

	The B<X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT> flag causes the function
	to consider the subject DN even if the certificate contains at least
	one subject alternative name of the right type (DNS name or email
	address as appropriate); the default is to ignore the subject DN
	when at least one corresponding subject alternative names is present.

	The B<X509_CHECK_FLAG_NEVER_CHECK_SUBJECT> flag causes the function to never
	consider the subject DN even if the certificate contains no subject alternative
	names of the right type (DNS name or email address as appropriate); the default
	is to use the subject DN when no corresponding subject alternative names are
	present.
	If both B<X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT> and
	B<X509_CHECK_FLAG_NEVER_CHECK_SUBJECT> are specified, the latter takes
	precedence and the subject DN is not checked for matching names.

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

	If set, B<X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS> suppresses support
	for "*" as wildcard pattern in labels that have a prefix or suffix,
	such as: "www" or "www"; this only applies to B<X509_check_host>.

	If set, B<X509_CHECK_FLAG_MULTI_LABEL_WILDCARDS> allows a "*" that
	constitutes the complete label of a DNS name (e.g. "*.example.com")
	to match more than one label in B<name>; this flag only applies
	to B<X509_check_host>.

	If set, B<X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS> restricts B<name>
	values which start with ".", that would otherwise match any sub-domain
	in the peer certificate, to only match direct child sub-domains.
	Thus, for instance, with this flag set a B<name> of ".example.com"
	would match a peer certificate with a DNS name of "www.example.com",
	but would not match a peer certificate with a DNS name of
	"www.sub.example.com"; this flag 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
	or an ASN.1 decoding error.

	All functions can also return -2 if the input is malformed. For example,
	X509_check_host() returns -2 if the provided B<name> contains embedded
	NULs.

	=head1 NOTES

	Applications are encouraged to use X509_VERIFY_PARAM_set1_host()
	rather than explicitly calling L<X509_check_host(3)>. Hostname
	checks may be out of scope with the DANE-EE(3) certificate usage,
	and the internal checks will be suppressed as appropriate when
	DANE support is enabled.

	=head1 SEE ALSO

	L<SSL_get_verify_result(3)>,
	L<X509_VERIFY_PARAM_set1_host(3)>,
	L<X509_VERIFY_PARAM_add1_host(3)>,
	L<X509_VERIFY_PARAM_set1_email(3)>,
	L<X509_VERIFY_PARAM_set1_ip(3)>

	=head1 HISTORY

	These functions were added in OpenSSL 1.0.2.

	=head1 COPYRIGHT

	Copyright 2012-2021 The OpenSSL Project Authors. All Rights Reserved.

	Licensed under the Apache License 2.0 (the "License"). You may not use
	this file except in compliance with the License. You can obtain a copy
	in the file LICENSE in the source distribution or at
	L<https://www.openssl.org/source/license.html>.

	=cut