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/x509.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 host name, 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 host name, 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 for
40 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_NO_WILDCARDS,
69 X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS,
70 X509_CHECK_FLAG_MULTI_LABEL_WILDCARDS.
71 X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS.
72 The X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT flag causes the function to
74 consider the subject DN even if the certificate contains at least one
75 subject alternative name of the right type (DNS name or email address
76 as appropriate); the default is to ignore the subject DN when at least
77 one corresponding subject alternative names is present.
78 If set, X509_CHECK_FLAG_NO_WILDCARDS disables wildcard expansion; this
80 only applies to X509_check_host.
81 If set, X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS suppresses support for "*"
83 as wildcard pattern in labels that have a prefix or suffix, such as:
84 "www*" or "*www"; this only aplies to X509_check_host.
85 If set, X509_CHECK_FLAG_MULTI_LABEL_WILDCARDS allows a "*" that
87 constitutes the complete label of a DNS name (e.g. "*.example.com") to
88 match more than one label in name; this flag only applies to
89 X509_check_host.
90 If set, X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS restricts name values
92 which start with ".", that would otherwise match any sub-domain in the
93 peer certificate, to only match direct child sub-domains. Thus, for
94 instance, with this flag set a name of ".example.com" would match a
95 peer certificate with a DNS name of "www.example.com", but would not
96 match a peer certificate with a DNS name of "www.sub.example.com"; this
97 flag only applies to X509_check_host.
98
100 The functions return 1 for a successful match, 0 for a failed match and
101 -1 for an internal error: typically a memory allocation failure or an
102 ASN.1 decoding error.
103 All functions can also return -2 if the input is malformed. For
105 example, X509_check_host() returns -2 if the provided name contains
106 embedded NULs.
107
109 Applications are encouraged to use X509_VERIFY_PARAM_set1_host() rather
110 than explicitly calling X509_check_host(3). Host name checks are out of
111 scope with the DANE-EE(3) certificate usage, and the internal checks
112 will be suppressed as appropriate when DANE support is added to
113 OpenSSL.
114
116 SSL_get_verify_result(3), X509_VERIFY_PARAM_set1_host(3),
117 X509_VERIFY_PARAM_add1_host(3), X509_VERIFY_PARAM_set1_email(3),
118 X509_VERIFY_PARAM_set1_ip(3), X509_VERIFY_PARAM_set1_ipasc(3)
119
121 These functions were added in OpenSSL 1.0.2.
1221.0.2o 2018-03-27 X509_check_host(3)