参考：

def openssl_private_encrypt(key, data, backend):    """Encrypt data with RSA private key.    This is a rewrite of the function from PHP, using cryptography    FFI bindings to the OpenSSL library. Private key encryption is    non-standard operation and Python packages either don't offer    it at all, or it's incompatible with the PHP version.    The backend argument MUST be the OpenSSL cryptography backend.    """    length = backend._lib.EVP_PKEY_size(key._evp_pkey)    buffer = backend._ffi.new('unsigned char[]', length)    result = backend._lib.RSA_private_encrypt(        len(data), data, buffer,        backend._lib.EVP_PKEY_get1_RSA(key._evp_pkey),        backend._lib.RSA_PKCS1_PADDING)    backend.openssl_assert(result == length)    return backend._ffi.buffer(buffer)[:]from cryptography.hazmat.backends.openssl.backend import backendfrom cryptography.hazmat.primitives.serialization import load_pem_private_keyprivkey = load_pem_private_key(self.pri_key_str, None,  backend)tmp = openssl_private_encrypt(privkey, md5Str, backend)