X509_check_host(3ossl)

1X509_CHECK_HOST(3ossl)              OpenSSL             X509_CHECK_HOST(3ossl)
2
3
4

NAME

6       X509_check_host, X509_check_email, X509_check_ip, X509_check_ip_asc -
7       X.509 certificate matching
8

SYNOPSIS

10        #include <openssl/x509v3.h>
11
12        int X509_check_host(X509 *, const char *name, size_t namelen,
13                            unsigned int flags, char **peername);
14        int X509_check_email(X509 *, const char *address, size_t addresslen,
15                             unsigned int flags);
16        int X509_check_ip(X509 *, const unsigned char *address, size_t addresslen,
17                          unsigned int flags);
18        int X509_check_ip_asc(X509 *, const char *address, unsigned int flags);
19

DESCRIPTION

21       The certificate matching functions are used to check whether a
22       certificate matches a given hostname, email address, or IP address.
23       The validity of the certificate and its trust level has to be checked
24       by other means.
25
26       X509_check_host() checks if the certificate Subject Alternative Name
27       (SAN) or Subject CommonName (CN) matches the specified hostname, which
28       must be encoded in the preferred name syntax described in section 3.5
29       of RFC 1034.  By default, wildcards are supported and they match  only
30       in the left-most label; but they may match part of that label with an
31       explicit prefix or suffix.  For example, by default, the host name
32       "www.example.com" would match a certificate with a SAN or CN value of
33       "*.example.com", "w*.example.com" or "*w.example.com".
34
35       Per section 6.4.2 of RFC 6125, name values representing international
36       domain names must be given in A-label form.  The namelen argument must
37       be the number of characters in the name string or zero in which case
38       the length is calculated with strlen(name).  When name starts with a
39       dot (e.g. ".example.com"), it will be matched by a certificate valid
40       for any sub-domain of name, (see also
41       X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS below).
42
43       When the certificate is matched, and peername is not NULL, a pointer to
44       a copy of the matching SAN or CN from the peer certificate is stored at
45       the address passed in peername.  The application is responsible for
46       freeing the peername via OPENSSL_free() when it is no longer needed.
47
48       X509_check_email() checks if the certificate matches the specified
49       email address. The mailbox syntax of RFC 822 is supported, comments are
50       not allowed, and no attempt is made to normalize quoted characters. The
51       mailbox syntax of RFC 6531 is supported for SmtpUTF8Mailbox address in
52       subjectAltName according to RFC 8398, with similar limitations as for
53       RFC 822 syntax, and no attempt is made to convert from A-label to
54       U-label before comparison.  The addresslen argument must be the number
55       of characters in the address string or zero in which case the length is
56       calculated with strlen(address).
57
58       X509_check_ip() checks if the certificate matches a specified IPv4 or
59       IPv6 address.  The address array is in binary format, in network byte
60       order.  The length is either 4 (IPv4) or 16 (IPv6).  Only explicitly
61       marked addresses in the certificates are considered; IP addresses
62       stored in DNS names and Common Names are ignored. There are currently
63       no flags that would affect the behavior of this call.
64
65       X509_check_ip_asc() is similar, except that the NUL-terminated string
66       address is first converted to the internal representation.
67
68       The flags argument is usually 0.  It can be the bitwise OR of the
69       flags:
70
71       X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT,
72       X509_CHECK_FLAG_NEVER_CHECK_SUBJECT,
73       X509_CHECK_FLAG_NO_WILDCARDS,
74       X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS,
75       X509_CHECK_FLAG_MULTI_LABEL_WILDCARDS.
76       X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS.
77
78       The X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT flag causes the function to
79       consider the subject DN even if the certificate contains at least one
80       subject alternative name of the right type (DNS name or email address
81       as appropriate); the default is to ignore the subject DN when at least
82       one corresponding subject alternative names is present.
83
84       The X509_CHECK_FLAG_NEVER_CHECK_SUBJECT flag causes the function to
85       never consider the subject DN even if the certificate contains no
86       subject alternative names of the right type (DNS name or email address
87       as appropriate); the default is to use the subject DN when no
88       corresponding subject alternative names are present.  If both
89       X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT and
90       X509_CHECK_FLAG_NEVER_CHECK_SUBJECT are specified, the latter takes
91       precedence and the subject DN is not checked for matching names.
92
93       If set, X509_CHECK_FLAG_NO_WILDCARDS disables wildcard expansion; this
94       only applies to X509_check_host.
95
96       If set, X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS suppresses support for "*"
97       as wildcard pattern in labels that have a prefix or suffix, such as:
98       "www*" or "*www"; this only applies to X509_check_host.
99
100       If set, X509_CHECK_FLAG_MULTI_LABEL_WILDCARDS allows a "*" that
101       constitutes the complete label of a DNS name (e.g. "*.example.com") to
102       match more than one label in name; this flag only applies to
103       X509_check_host.
104
105       If set, X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS restricts name values
106       which start with ".", that would otherwise match any sub-domain in the
107       peer certificate, to only match direct child sub-domains.  Thus, for
108       instance, with this flag set a name of ".example.com" would match a
109       peer certificate with a DNS name of "www.example.com", but would not
110       match a peer certificate with a DNS name of "www.sub.example.com"; this
111       flag only applies to X509_check_host.
112

RETURN VALUES

114       The functions return 1 for a successful match, 0 for a failed match and
115       -1 for an internal error: typically a memory allocation failure or an
116       ASN.1 decoding error.
117
118       All functions can also return -2 if the input is malformed. For
119       example, X509_check_host() returns -2 if the provided name contains
120       embedded NULs.
121

NOTES

123       Applications are encouraged to use X509_VERIFY_PARAM_set1_host() rather
124       than explicitly calling X509_check_host(3). Hostname checks may be out
125       of scope with the DANE-EE(3) certificate usage, and the internal checks
126       will be suppressed as appropriate when DANE support is enabled.
127

HISTORY

134       These functions were added in OpenSSL 1.0.2.
135

COPYRIGHT

137       Copyright 2012-2022 The OpenSSL Project Authors. All Rights Reserved.
138
139       Licensed under the Apache License 2.0 (the "License").  You may not use
140       this file except in compliance with the License.  You can obtain a copy
141       in the file LICENSE in the source distribution or at
142       <https://www.openssl.org/source/license.html>.
143
144
145
1463.1.1                             2023-08-31            X509_CHECK_HOST(3ossl)