SSL_CTX_set_cert_verify_callback(3)OpenSSLSSL_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)3rd Berkeley Distribution 0.9.6m SSL_CTX_set_cert_verify_callback(3)
