SSL_CTX_set_cert_verify_callbOSSL_CTX_set_cert_verify_callback(3)NAMESSL_CTX_set_cert_verify_callback - set peer certificate
verification procedure
SYNOPSIS
#include <openssl/ssl.h>
void SSL_CTX_set_cert_verify_callback(SSL_CTX *ctx, int (*callback)(),
char *arg);
int (*callback)();
DESCRIPTIONSSL_CTX_set_cert_verify_callback() sets the verification
callback function for ctx. SSL objects, that are created
from ctx inherit the setting valid at the time, SSL_new(3)
is called. arg is currently ignored.
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 callback is specified
via SSL_CTX_set_cert_verify_callback(), the supplied
callback function is called instead. By setting callback
to NULL, the default behaviour is restored.
When the verification must be performed, callback will be
called with the argument callback(X509_STORE_CTX
*x509_store_ctx). The arguments arg that can be specified
when setting callback are currently ignored.
callback should return 1 to indicate verification success
and 0 to indicate verification failure. If SSL_VERIFY_PEER
is set and 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
error member of x509_store_ctx, so that the calling
application will be informed about the detailed result of
the verification procedure!
Within x509_store_ctx, callback has access to the
verify_callback function set using SSL_CTX_set_verify(3).
WARNINGS
Do not mix the verification callback described in this
function with the verify_callback function called during
the verification process. The latter is set using the
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
verify_callback function.
BUGS
It is possible to specify arguments to be passed to the
verification callback. Currently they are however not
passed but ignored.
The callback function is not specified via a prototype, so
that no type checking takes place.
RETURN VALUESSSL_CTX_set_cert_verify_callback() does not provide
diagnostic information.
SEE ALSOssl(3), SSL_CTX_set_verify(3), SSL_get_verify_result(3),
SSL_CTX_load_verify_locations(3)23/Aug/2001 SSL_CTX_set_cert_verify_callback(3)
