X509_check_host(3)           OpenSSL           X509_check_host(3)


     X509_check_host, X509_check_email, X509_check_ip,
     X509_check_ip_asc - X.509 certificate matching


      #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);


     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 "" would match a certificate
     with a SAN or CN value of "*", "w*"
     or "*".

     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
     ""), it will be matched by a certificate valid
     for any sub-domain of name, (see also

     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

     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

     The flags argument is usually 0.  It can be the bitwise OR
     of the flags:


     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.
     "*") to match more than one label in name; this
     flag only applies to X509_check_host.

     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 "" would match a peer certificate with a
     DNS name of "", but would not match a peer
     certificate with a DNS name of ""; this
     flag only applies to X509_check_host.

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X509_check_host(3)           OpenSSL           X509_check_host(3)


     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.


     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.


     SSL_get_verify_result(3), X509_VERIFY_PARAM_set1_host(3),


     These functions were added in OpenSSL 1.0.2.

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See also X509_check_email(3)
See also X509_check_host(3)
See also X509_check_ip(3)

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