shall be specified, the NULL pointer can be used for B<verify_callback>. In
this case last B<verify_callback> set specifically for this B<ssl> remains. If
no special B<callback> was set before, the default callback for the underlying
-B<ctx> is used, that was valid at the the time B<ssl> was created with
+B<ctx> is used, that was valid at the time B<ssl> was created with
L<SSL_new(3)|SSL_new(3)>.
SSL_CTX_set_verify_depth() sets the maximum B<depth> for the certificate chain
B<Server mode:> the server sends a client certificate request to the client.
The certificate returned (if any) is checked. If the verification process
-fails as indicated by B<verify_callback>, the TLS/SSL handshake is
+fails, the TLS/SSL handshake is
immediately terminated with an alert message containing the reason for
the verification failure.
The behaviour can be controlled by the additional
SSL_VERIFY_FAIL_IF_NO_PEER_CERT and SSL_VERIFY_CLIENT_ONCE flags.
B<Client mode:> the server certificate is verified. If the verification process
-fails as indicated by B<verify_callback>, the TLS/SSL handshake is
+fails, the TLS/SSL handshake is
immediately terminated with an alert message containing the reason for
the verification failure. If no server certificate is sent, because an
anonymous cipher is used, SSL_VERIFY_PEER is ignored.
Exactly one of the B<mode> flags SSL_VERIFY_NONE and SSL_VERIFY_PEER must be
set at any time.
+The actual verification procedure is performed either using the built-in
+verification procedure or using another application provided verification
+function set with
+L<SSL_CTX_set_cert_verify_callback(3)|SSL_CTX_set_cert_verify_callback(3)>.
+The following descriptions apply in the case of the built-in procedure. An
+application provided procedure also has access to the verify depth information
+and the verify_callback() function, but the way this information is used
+may be different.
+
SSL_CTX_set_verify_depth() and SSL_set_verify_depth() set the limit up
to which depth certificates in a chain are used during the verification
procedure. If the certificate chain is longer than allowed, the certificates
SSL_VERIFY_PEER is set, a verification failure alert is sent to the peer and
the TLS/SSL handshake is terminated. If B<verify_callback> returns 1,
the verification process is continued. If B<verify_callback> always returns
-1, the TLS/SSL handshake will never be terminated because of this application
-experiencing a verification failure. The calling process can however
-retrieve the error code of the last verification error using
+1, the TLS/SSL handshake will not be terminated with respect to verification
+failures and the connection will be established. The calling process can
+however retrieve the error code of the last verification error using
L<SSL_get_verify_result(3)|SSL_get_verify_result(3)> or by maintaining its
own error storage managed by B<verify_callback>.
The example is realized for a server that does allow but not require client
certificates.
+The example makes use of the ex_data technique to store application data
+into/retrieve application data from the SSL structure
+(see L<SSL_get_ex_new_index(3)|SSL_get_ex_new_index(3)>,
+L<SSL_get_ex_data_X509_STORE_CTX_idx(3)|SSL_get_ex_data_X509_STORE_CTX_idx(3)>).
+
...
- int verbose_mode;
- int verify_depth;
- int always_continue;
+ typedef struct {
+ int verbose_mode;
+ int verify_depth;
+ int always_continue;
+ } mydata_t;
+ int mydata_index;
...
static int verify_callback(int preverify_ok, X509_STORE_CTX *ctx)
{
char buf[256];
X509 *err_cert;
int err, depth;
+ SSL *ssl;
+ mydata_t *mydata;
err_cert = X509_STORE_CTX_get_current_cert(ctx);
err = X509_STORE_CTX_get_error(ctx);
depth = X509_STORE_CTX_get_error_depth(ctx);
+ /*
+ * Retrieve the pointer to the SSL of the connection currently treated
+ * and the application specific data stored into the SSL object.
+ */
+ ssl = X509_STORE_CTX_get_ex_data(ctx, SSL_get_ex_data_X509_STORE_CTX_idx());
+ mydata = SSL_get_ex_data(ssl, mydata_index);
+
X509_NAME_oneline(X509_get_subject_name(err_cert), buf, 256);
/*
* SSL_CTX_set_verify_depth() is by purpose set to "limit+1" so
* that whenever the "depth>verify_depth" condition is met, we
* have violated the limit and want to log this error condition.
- * We must do it here, because the CHAIN_TO_LONG error would not
+ * We must do it here, because the CHAIN_TOO_LONG error would not
* be found explicitly; only errors introduced by cutting off the
* additional certificates would be logged.
*/
- if (depth > verify_depth) {
+ if (depth > mydata->verify_depth) {
preverify_ok = 0;
err = X509_V_ERR_CERT_CHAIN_TOO_LONG;
X509_STORE_CTX_set_error(ctx, err);
printf("verify error:num=%d:%s:depth=%d:%s\n", err,
X509_verify_cert_error_string(err), depth, buf);
}
- else if (verbose_mode)
+ else if (mydata->verbose_mode)
{
printf("depth=%d:%s\n", depth, buf);
}
* At this point, err contains the last verification error. We can use
* it for something special
*/
- if (!preverify_ok && (err == X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT)
+ if (!preverify_ok && (err == X509_V_ERR_UNABLE_TO_GET_ISSUER_CERT))
{
X509_NAME_oneline(X509_get_issuer_name(ctx->current_cert), buf, 256);
printf("issuer= %s\n", buf);
}
- if (always_continue)
+ if (mydata->always_continue)
return 1;
else
return preverify_ok;
}
+ ...
+
+ mydata_t mydata;
+
+ ...
+ mydata_index = SSL_get_ex_new_index(0, "mydata index", NULL, NULL, NULL);
+
...
SSL_CTX_set_verify(ctx, SSL_VERIFY_PEER|SSL_VERIFY_CLIENT_ONCE,
verify_callback);
* an appropriate error in the logfile.
*/
SSL_CTX_set_verify_depth(verify_depth + 1);
+
+ /*
+ * Set up the SSL specific data into "mydata" and store it into th SSL
+ * structure.
+ */
+ mydata.verify_depth = verify_depth; ...
+ SSL_set_ex_data(ssl, mydata_index, &mydata);
...
SSL_accept(ssl); /* check of success left out for clarity */
L<SSL_CTX_get_verify_mode(3)|SSL_CTX_get_verify_mode(3)>,
L<SSL_get_verify_result(3)|SSL_get_verify_result(3)>,
L<SSL_CTX_load_verify_locations(3)|SSL_CTX_load_verify_locations(3)>,
-L<SSL_get_peer_certificate(3)|SSL_get_peer_certificate(3)>
+L<SSL_get_peer_certificate(3)|SSL_get_peer_certificate(3)>,
+L<SSL_CTX_set_cert_verify_callback(3)|SSL_CTX_set_cert_verify_callback(3)>,
+L<SSL_get_ex_data_X509_STORE_CTX_idx(3)|SSL_get_ex_data_X509_STORE_CTX_idx(3)>,
+L<SSL_get_ex_new_index(3)|SSL_get_ex_new_index(3)>
=cut
projects / openssl.git / blobdiff