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Improve X509_check_host() documentation.

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Based on feedback from Jeffrey Walton.

(cherry picked from commit b73ac02735)
This commit is contained in:
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
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.
The certificate matching functions are used to check whether 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. 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(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 hostname or CommonName
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. Applications are
advised to use X509_VERIFY_PARAM_set1_host() in preference to
explicitly calling L<X509_check_host(3)>, hostname checks are out
of scope with the DANE-EE(3) certificate usage, and the internal
check will be suppressed as appropriate when DANE support is added
to OpenSSL.
X509_check_host() checks if the certificate Subject Alternative
Name (SAN) or Subject CommonName (CN) matches the specified host
name, 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 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
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).
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
@ -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.
=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
L<SSL_get_verify_result(3)|SSL_get_verify_result(3)>,