SSL_CTX_set_cert_verify_callback.pod revision 89837
1=pod 2 3=head1 NAME 4 5SSL_CTX_set_cert_verify_callback - set peer certificate verification procedure 6 7=head1 SYNOPSIS 8 9 #include <openssl/ssl.h> 10 11 void SSL_CTX_set_cert_verify_callback(SSL_CTX *ctx, int (*callback)(), 12 char *arg); 13 int (*callback)(); 14 15=head1 DESCRIPTION 16 17SSL_CTX_set_cert_verify_callback() sets the verification callback function for 18B<ctx>. SSL objects, that are created from B<ctx> inherit the setting valid at 19the time, L<SSL_new(3)|SSL_new(3)> is called. B<arg> is currently ignored. 20 21=head1 NOTES 22 23Whenever a certificate is verified during a SSL/TLS handshake, a verification 24function is called. If the application does not explicitly specify a 25verification callback function, the built-in verification function is used. 26If a verification callback B<callback> is specified via 27SSL_CTX_set_cert_verify_callback(), the supplied callback function is called 28instead. By setting B<callback> to NULL, the default behaviour is restored. 29 30When the verification must be performed, B<callback> will be called with 31the argument callback(X509_STORE_CTX *x509_store_ctx). The arguments B<arg> 32that can be specified when setting B<callback> are currently ignored. 33 34B<callback> should return 1 to indicate verification success and 0 to 35indicate verification failure. If SSL_VERIFY_PEER is set and B<callback> 36returns 0, the handshake will fail. As the verification procedure may 37allow to continue the connection in case of failure (by always returning 1) 38the verification result must be set in any case using the B<error> 39member of B<x509_store_ctx>, so that the calling application will be informed 40about the detailed result of the verification procedure! 41 42Within B<x509_store_ctx>, B<callback> has access to the B<verify_callback> 43function set using L<SSL_CTX_set_verify(3)|SSL_CTX_set_verify(3)>. 44 45=head1 WARNINGS 46 47Do not mix the verification callback described in this function with the 48B<verify_callback> function called during the verification process. The 49latter is set using the L<SSL_CTX_set_verify(3)|SSL_CTX_set_verify(3)> 50family of functions. 51 52Providing a complete verification procedure including certificate purpose 53settings etc is a complex task. The built-in procedure is quite powerful 54and in most cases it should be sufficient to modify its behaviour using 55the B<verify_callback> function. 56 57=head1 BUGS 58 59It is possible to specify arguments to be passed to the verification callback. 60Currently they are however not passed but ignored. 61 62The B<callback> function is not specified via a prototype, so that no 63type checking takes place. 64 65=head1 RETURN VALUES 66 67SSL_CTX_set_cert_verify_callback() does not provide diagnostic information. 68 69=head1 SEE ALSO 70 71L<ssl(3)|ssl(3)>, L<SSL_CTX_set_verify(3)|SSL_CTX_set_verify(3)>, 72L<SSL_get_verify_result(3)|SSL_get_verify_result(3)>, 73L<SSL_CTX_load_verify_locations(3)|SSL_CTX_load_verify_locations(3)> 74 75=cut 76