@deftypefun {int} {gnutls_x509_crq_set_extension_by_oid} (gnutls_x509_crq_t @var{crq}, const char * @var{oid}, const void * @var{buf}, size_t @var{sizeof_buf}, unsigned int @var{critical})
@var{crq}: a certificate of type @code{gnutls_x509_crq_t} 

@var{oid}: holds an Object Identifier in null terminated string

@var{buf}: a pointer to a DER encoded data

@var{sizeof_buf}: holds the size of  @code{buf} 

@var{critical}: should be non-zero if the extension is to be marked as critical

This function will set an the extension, by the specified OID, in
the certificate request.  The extension data should be binary data DER
encoded.

@strong{Returns:} On success, @code{GNUTLS_E_SUCCESS}  (0) is returned, otherwise a
negative error value.
@end deftypefun