openssl/doc/ssl/SSL_CTX_set_cert_verify_callback.pod
Rich Salz a528d4f0a9 Remove SSLeay history, etc., from docs
If something was "present in all versions" of SSLeay, or if it was
added to a version of SSLeay (and therefore predates OpenSSL),
remove mention of it.  Documentation history now starts with OpenSSL.

Remove mention of all history before OpenSSL 0.9.8, inclusive.

Remove all AUTHOR sections.

Reviewed-by: Tim Hudson <tjh@openssl.org>
2015-10-28 17:23:51 -04:00

68 lines
2.4 KiB
Plaintext

=pod
=head1 NAME
SSL_CTX_set_cert_verify_callback - set peer certificate verification procedure
=head1 SYNOPSIS
#include <openssl/ssl.h>
void SSL_CTX_set_cert_verify_callback(SSL_CTX *ctx, int (*callback)(X509_STORE_CTX *,void *), void *arg);
=head1 DESCRIPTION
SSL_CTX_set_cert_verify_callback() sets the verification callback function for
I<ctx>. SSL objects that are created from I<ctx> inherit the setting valid at
the time when L<SSL_new(3)> is called.
=head1 NOTES
Whenever a certificate is verified during a SSL/TLS handshake, a verification
function is called. If the application does not explicitly specify a
verification callback function, the built-in verification function is used.
If a verification callback I<callback> is specified via
SSL_CTX_set_cert_verify_callback(), the supplied callback function is called
instead. By setting I<callback> to NULL, the default behaviour is restored.
When the verification must be performed, I<callback> will be called with
the arguments callback(X509_STORE_CTX *x509_store_ctx, void *arg). The
argument I<arg> is specified by the application when setting I<callback>.
I<callback> should return 1 to indicate verification success and 0 to
indicate verification failure. If SSL_VERIFY_PEER is set and I<callback>
returns 0, the handshake will fail. As the verification procedure may
allow to continue the connection in case of failure (by always returning 1)
the verification result must be set in any case using the B<error>
member of I<x509_store_ctx> so that the calling application will be informed
about the detailed result of the verification procedure!
Within I<x509_store_ctx>, I<callback> has access to the I<verify_callback>
function set using L<SSL_CTX_set_verify(3)>.
=head1 WARNINGS
Do not mix the verification callback described in this function with the
B<verify_callback> function called during the verification process. The
latter is set using the L<SSL_CTX_set_verify(3)>
family of functions.
Providing a complete verification procedure including certificate purpose
settings etc is a complex task. The built-in procedure is quite powerful
and in most cases it should be sufficient to modify its behaviour using
the B<verify_callback> function.
=head1 BUGS
=head1 RETURN VALUES
SSL_CTX_set_cert_verify_callback() does not provide diagnostic information.
=head1 SEE ALSO
L<ssl(3)>, L<SSL_CTX_set_verify(3)>,
L<SSL_get_verify_result(3)>,
L<SSL_CTX_load_verify_locations(3)>
=cut