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SSL_CTX_set_cert_verify_callback(3)                OpenSSL               SSL_CTX_set_cert_verify_callback(3)



NAME
       SSL_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)(X509_STORE_CTX *,void *), void *arg);

DESCRIPTION
       SSL_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 when SSL_new(3) is called.

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 arguments
       callback(X509_STORE_CTX *x509_store_ctx, void *arg). The argument arg is specified by the application
       when setting callback.

       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
RETURN VALUES
       SSL_CTX_set_cert_verify_callback() does not provide diagnostic information.

SEE ALSO
       ssl(3), SSL_CTX_set_verify(3), SSL_get_verify_result(3), SSL_CTX_load_verify_locations(3)

HISTORY
       Previous to OpenSSL 0.9.7, the arg argument to SSL_CTX_set_cert_verify_callback was ignored, and
       callback was called simply as
        int (*callback)(X509_STORE_CTX *) To compile software written for previous versions of OpenSSL, a
       dummy argument will have to be added to callback.



0.9.7l                                           2002-02-28              SSL_CTX_set_cert_verify_callback(3)