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Improve X509_check_host() documentation.

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Based on feedback from Jeffrey Walton.

(cherry picked from commit b73ac027357da29d9e393f24cd224999c94028d1)
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Viktor Dukhovni 2014-07-07 20:34:06 +10:00
parent e83c913723
commit 3ebcecf5c4
1 changed files with 38 additions and 27 deletions
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doc/crypto/X509_check_host.pod
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@ -18,38 +18,41 @@ X509_check_host, X509_check_email, X509_check_ip, X509_check_ip_asc - X.509 cert
=head1 DESCRIPTION =head1 DESCRIPTION
The certificate matching functions are intended to be called to check The certificate matching functions are used to check whether a
if a certificate matches a given host name, email address, or IP certificate matches a given host name, email address, or IP address.
address. The validity of the certificate and its trust level has to The validity of the certificate and its trust level has to be checked by
be checked by other means. other means.
X509_check_host() checks if the certificate matches the specified X509_check_host() checks if the certificate Subject Alternative
host name, which must be encoded in the preferred name syntax Name (SAN) or Subject CommonName (CN) matches the specified host
described in section 3.5 of RFC 1034. Per section 6.4.2 of RFC 6125, name, which must be encoded in the preferred name syntax described
B<name> values representing international domain names must be given in section 3.5 of RFC 1034. By default, wildcards are supported
in A-label form. The B<namelen> argument must be the number of and they match only in the left-most label; but they may match
characters in the name string or zero in which case the length is part of that label with an explicit prefix or suffix. For example,
calculated with strlen(name). When B<name> starts with a dot (e.g by default, the host B<name> "www.example.com" would match a
".example.com"), it will be matched by a certificate valid for any certificate with a SAN or CN value of "*.example.com", "w*.example.com"
sub-domain of B<name>, (see also B<X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS> or "*w.example.com".
below). When the certificate is matched and B<peername> is not
NULL a pointer to a copy of the matching hostname or CommonName Per section 6.4.2 of RFC 6125, B<name> values representing international
from the peer certificate is stored at the address passed in domain names must be given in A-label form. The B<namelen> argument
B<peername>. The application is responsible for freeing the peername must be the number of characters in the name string or zero in which
via OPENSSL_free() when it is no longer needed. Applications are case the length is calculated with strlen(B<name>). When B<name> starts
advised to use X509_VERIFY_PARAM_set1_host() in preference to with a dot (e.g ".example.com"), it will be matched by a certificate
explicitly calling L<X509_check_host(3)>, hostname checks are out valid for any sub-domain of B<name>, (see also
of scope with the DANE-EE(3) certificate usage, and the internal B<X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS> below).
check will be suppressed as appropriate when DANE support is added
to OpenSSL. 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 X509_check_email() checks if the certificate matches the specified
email address. Only the mailbox syntax of RFC 822 is supported, email B<address>. Only the mailbox syntax of RFC 822 is supported,
comments are not allowed, and no attempt is made to normalize quoted comments are not allowed, and no attempt is made to normalize quoted
characters. The B<addresslen> argument must be the number of characters. The B<addresslen> argument must be the number of
characters in the address string. The B<namelen> argument must be characters in the address string or zero in which case the length
the number of characters in the name string or zero in which case the is calculated with strlen(B<address>).
length is calculated with strlen(name).
X509_check_ip() checks if the certificate matches a specified IPv4 or X509_check_ip() checks if the certificate matches a specified IPv4 or
IPv6 address. The B<address> array is in binary format, in network IPv6 address. The B<address> array is in binary format, in network
@ -110,6 +113,14 @@ 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. X509_check_ip_asc() can also return -2 if the IP address string is malformed.
=head1 NOTES
Applications are encouraged to use X509_VERIFY_PARAM_set1_host()
rather than explicitly calling L<X509_check_host(3)>. Host name
checks are out of scope with the DANE-EE(3) certificate usage,
and the internal checks will be suppressed as appropriate when
DANE support is added to OpenSSL.
=head1 SEE ALSO =head1 SEE ALSO
L<SSL_get_verify_result(3)|SSL_get_verify_result(3)>, L<SSL_get_verify_result(3)|SSL_get_verify_result(3)>,