/usr/man/cat.3/X509_check_email.3
X509_check_host(3) OpenSSL X509_check_host(3)
NAME
X509_check_host, X509_check_email, X509_check_ip,
X509_check_ip_asc - X.509 certificate matching
SYNOPSIS
#include <openssl/x509.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);
DESCRIPTION
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 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 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, name values representing
international domain names must be given in A-label form.
The 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 name starts with a dot (e.g
".example.com"), it will be matched by a certificate valid
for any sub-domain of name, (see also
X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS below).
When the certificate is matched, and 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 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, comments are not allowed, and no attempt is
made to normalize quoted characters. The addresslen
argument must be the number of characters in the address
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X509_check_host(3) OpenSSL X509_check_host(3)
string or zero in which case the length is calculated with
strlen(address).
X509_check_ip() checks if the certificate matches a
specified IPv4 or IPv6 address. The 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 address is first converted to the internal
representation.
The flags argument is usually 0. It can be the bitwise OR
of the flags:
X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT,
X509_CHECK_FLAG_NO_WILDCARDS,
X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS,
X509_CHECK_FLAG_MULTI_LABEL_WILDCARDS.
X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS.
The 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.
If set, X509_CHECK_FLAG_NO_WILDCARDS disables wildcard
expansion; this only applies to X509_check_host.
If set, 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
aplies to X509_check_host.
If set, 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 name; this
flag only applies to X509_check_host.
If set, X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS restricts
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
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 X509_check_host.
1.0.2t Last change: 2019-09-10 2
X509_check_host(3) OpenSSL X509_check_host(3)
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
name contains embedded NULs.
NOTES
Applications are encouraged to use
X509_VERIFY_PARAM_set1_host() rather than explicitly calling
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.
SEE ALSO
SSL_get_verify_result(3), X509_VERIFY_PARAM_set1_host(3),
X509_VERIFY_PARAM_add1_host(3),
X509_VERIFY_PARAM_set1_email(3),
X509_VERIFY_PARAM_set1_ip(3),
X509_VERIFY_PARAM_set1_ipasc(3)
HISTORY
These functions were added in OpenSSL 1.0.2.
1.0.2t Last change: 2019-09-10 3
See also X509_check_host(3)
See also X509_check_ip(3)
See also X509_check_ip_asc(3)
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