SSL_CTX_set_cert_verify_callback(3)

     SSL_CTX_set_cert_verify<I>00.9.6haSSL_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)(),
                                                 char *arg);
           int (*callback)();

     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, 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

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     SSL_CTX_set_cert_verify<I>00.9.6haSSL_CTX_set_cert_verify_callback(3)

          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 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)

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