1X509_CHECK_HOST(3) OpenSSL X509_CHECK_HOST(3)
2
6 X509_check_host, X509_check_email, X509_check_ip, X509_check_ip_asc -
7 X.509 certificate matching
8
10 #include <openssl/x509v3.h>
11 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
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 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 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 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 X509_check_email() checks if the certificate matches the specified
49 email address. Only the mailbox syntax of RFC 822 is supported,
50 comments are not allowed, and no attempt is made to normalize quoted
51 characters. The addresslen argument must be the number of characters
52 in the address string or zero in which case the length is calculated
53 with strlen(address).
54 X509_check_ip() checks if the certificate matches a specified IPv4 or
56 IPv6 address. The address array is in binary format, in network byte
57 order. The length is either 4 (IPv4) or 16 (IPv6). Only explicitly
58 marked addresses in the certificates are considered; IP addresses
59 stored in DNS names and Common Names are ignored.
60 X509_check_ip_asc() is similar, except that the NUL-terminated string
62 address is first converted to the internal representation.
63 The flags argument is usually 0. It can be the bitwise OR of the
65 flags:
66 X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT,
68 X509_CHECK_FLAG_NEVER_CHECK_SUBJECT,
69 X509_CHECK_FLAG_NO_WILDCARDS,
70 X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS,
71 X509_CHECK_FLAG_MULTI_LABEL_WILDCARDS.
72 X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS.
73 The X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT flag causes the function to
75 consider the subject DN even if the certificate contains at least one
76 subject alternative name of the right type (DNS name or email address
77 as appropriate); the default is to ignore the subject DN when at least
78 one corresponding subject alternative names is present.
79 The X509_CHECK_FLAG_NEVER_CHECK_SUBJECT flag causes the function to
81 never consider the subject DN even if the certificate contains no
82 subject alternative names of the right type (DNS name or email address
83 as appropriate); the default is to use the subject DN when no
84 corresponding subject alternative names are present. If both
85 X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT and
86 X509_CHECK_FLAG_NEVER_CHECK_SUBJECT are specified, the latter takes
87 precedence and the subject DN is not checked for matching names.
88 If set, X509_CHECK_FLAG_NO_WILDCARDS disables wildcard expansion; this
90 only applies to X509_check_host.
91 If set, X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS suppresses support for "*"
93 as wildcard pattern in labels that have a prefix or suffix, such as:
94 "www*" or "*www"; this only applies to X509_check_host.
95 If set, X509_CHECK_FLAG_MULTI_LABEL_WILDCARDS allows a "*" that
97 constitutes the complete label of a DNS name (e.g. "*.example.com") to
98 match more than one label in name; this flag only applies to
99 X509_check_host.
100 If set, X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS restricts name values
102 which start with ".", that would otherwise match any sub-domain in the
103 peer certificate, to only match direct child sub-domains. Thus, for
104 instance, with this flag set a name of ".example.com" would match a
105 peer certificate with a DNS name of "www.example.com", but would not
106 match a peer certificate with a DNS name of "www.sub.example.com"; this
107 flag only applies to X509_check_host.
108
110 The functions return 1 for a successful match, 0 for a failed match and
111 -1 for an internal error: typically a memory allocation failure or an
112 ASN.1 decoding error.
113 All functions can also return -2 if the input is malformed. For
115 example, X509_check_host() returns -2 if the provided name contains
116 embedded NULs.
117
119 Applications are encouraged to use X509_VERIFY_PARAM_set1_host() rather
120 than explicitly calling X509_check_host(3). Host name checks may be out
121 of scope with the DANE-EE(3) certificate usage, and the internal checks
122 will be suppressed as appropriate when DANE support is enabled.
123
125 SSL_get_verify_result(3), X509_VERIFY_PARAM_set1_host(3),
126 X509_VERIFY_PARAM_add1_host(3), X509_VERIFY_PARAM_set1_email(3),
127 X509_VERIFY_PARAM_set1_ip(3), X509_VERIFY_PARAM_set1_ipasc(3)
128
130 These functions were added in OpenSSL 1.0.2.
131
133 Copyright 2012-2020 The OpenSSL Project Authors. All Rights Reserved.
134 Licensed under the OpenSSL license (the "License"). You may not use
136 this file except in compliance with the License. You can obtain a copy
137 in the file LICENSE in the source distribution or at
138 <https://www.openssl.org/source/license.html>.
1391.1.1q 2022-07-07 X509_CHECK_HOST(3)