bionic (3) ne_ssl_set_verify.3.gz

NAME

       ne_ssl_set_verify - register an SSL certificate verification callback

SYNOPSIS

       #include <ne_session.h>

       typedef int ne_ssl_verify_fn(void *userdata, int failures, const ne_ssl_certificate *cert);

       void ne_ssl_set_verify(ne_session *session, ne_ssl_verify_fn verify_fn, void *userdata);

DESCRIPTION

       To enable manual SSL certificate verification, a callback can be registered using ne_ssl_set_verify. If
       such a callback is not registered, when a connection is established to an SSL server which does not
       present a certificate signed by a trusted CA (see ne_ssl_trust_cert), or if the certificate presented is
       invalid in some way, the connection will fail.

       When the callback is invoked, the failures parameter gives a bitmask indicating in what way the automatic
       certificate verification failed. The value is equal to the bit-wise OR of one or more of the following
       constants (and is guaranteed to be non-zero):

       NE_SSL_NOTYETVALID
           The certificate is not yet valid.

       NE_SSL_EXPIRED
           The certificate has expired.

       NE_SSL_IDMISMATCH
           The hostname used for the session does not match the hostname to which the certificate was issued.

       NE_SSL_UNTRUSTED
           The Certificate Authority which signed the certificate is not trusted.

       Note that if either of the NE_SSL_IDMISMATCH or NE_SSL_UNTRUSTED failures is given, the connection may
       have been intercepted by a third party, and must not be presumed to be “secure”.

       The cert parameter passed to the callback represents the certificate which was presented by the server.
       If the server presented a chain of certificates, the chain can be accessed using ne_ssl_cert_signedby.
       The cert object given is not valid after the callback returns.

RETURN VALUE

       The verification callback must return zero to indicate that the certificate should be trusted; and
       non-zero otherwise (in which case, the connection will fail).

EXAMPLES

       The following code implements an example verification callback, using the dump_cert function from
       ne_ssl_cert_subject to display certification information. Notice that the hostname of the server used for
       the session is passed as the userdata parameter to the callback.

           static int
           my_verify(void *userdata, int failures, const ne_ssl_certificate *cert)
           {
             const char *hostname = userdata;

             dump_cert(cert);

             puts("Certificate verification failed - the connection may have been "
                  "intercepted by a third party!");

             if (failures & NE_SSL_IDMISMATCH) {
               const char *id = ne_ssl_cert_identity(cert);
               if (id)
                 printf("Server certificate was issued to '%s' not '%s'.\n",
                        id, hostname);
               else
                 printf("The certificate was not issued for '%s'\n", hostname);
             }

             if (failures & NE_SSL_UNTRUSTED)
               puts("The certificate is not signed by a trusted Certificate Authority.");

             /* ... check for validity failures ... */

             if (prompt_user())
               return 1; /* fail verification */
             else
               return 0; /* trust the certificate anyway */
           }

           int
           main(...)
           {
             ne_session *sess = ne_session_create("https", "some.host.name", 443);
             ne_ssl_set_verify(sess, my_verify, "some.host.name");
             ...
           }

SEE ALSO

       ne_ssl_trust_cert, ne_ssl_readable_dname, ne_ssl_cert_subject

AUTHOR

       Joe Orton <neon@lists.manyfish.co.uk>
           Author.

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