remove asyncssh patching (#404)

Looks like this is no longer necessary, GitHub seems to
return proper algorithm name these days, at least it does for me.

src/scmrepo/git/backend/dulwich/asyncssh_vendor.py

@@ -97,45 +97,6 @@ async def _close(self) -> None:
     close = sync_wrapper(_close)
 
 
-# NOTE: Github's SSH server does not strictly comply with the SSH protocol.
-# When validating a public key using the rsa-sha2-256 or rsa-sha2-512
-# signature algorithms, RFC4252 + RFC8332 state that the server should respond
-# with the same algorithm in SSH_MSG_USERAUTH_PK_OK. Github's server always
-# returns "ssh-rsa" rather than the correct sha2 algorithm name (likely for
-# backwards compatibility with old SSH client reasons). This behavior causes
-# asyncssh to fail with a key-mismatch error (since asyncssh expects the server
-# to behave properly).
-#
-# See also:
-#   https://www.ietf.org/rfc/rfc4252.txt
-#   https://www.ietf.org/rfc/rfc8332.txt
-def _process_public_key_ok_gh(self, _pkttype, _pktid, packet):
-    from asyncssh.misc import ProtocolError
-
-    algorithm = packet.get_string()
-    key_data = packet.get_string()
-    packet.check_end()
-
-    # pylint: disable=protected-access
-    if (
-        (
-            algorithm == b"ssh-rsa"
-            and self._keypair.algorithm
-            not in (
-                b"ssh-rsa",
-                b"rsa-sha2-256",
-                b"rsa-sha2-512",
-            )
-        )
-        or (algorithm not in (b"ssh-rsa", self._keypair.algorithm))
-        or key_data != self._keypair.public_data
-    ):
-        raise ProtocolError("Key mismatch")
-
-    self.create_task(self._send_signed_request())
-    return True
-
-
 class InteractiveSSHClient(SSHClient):
     _conn: Optional["SSHClientConnection"] = None
     _keys_to_try: Optional[list["FilePath"]] = None
@@ -286,12 +247,6 @@ async def _run_command(
           key_filename: Optional path to private keyfile
         """
         import asyncssh
-        from asyncssh.auth import MSG_USERAUTH_PK_OK, _ClientPublicKeyAuth
-
-        # pylint: disable=protected-access
-        _ClientPublicKeyAuth._packet_handlers[MSG_USERAUTH_PK_OK] = (
-            _process_public_key_ok_gh
-        )
 
         try:
             conn = await asyncssh.connect(

tests/test_dulwich.py

@@ -212,28 +212,6 @@ def test_run_command_partial_transfer(ssh_port: int, mocker: MockerFixture):
     assert mock_stderr.call_count == 3
 
 
-@pytest.mark.parametrize("algorithm", [b"ssh-rsa", b"rsa-sha2-256", b"rsa-sha2-512"])
-def test_dulwich_github_compat(mocker: MockerFixture, algorithm: bytes):
-    from asyncssh.misc import ProtocolError
-
-    from scmrepo.git.backend.dulwich.asyncssh_vendor import _process_public_key_ok_gh
-
-    key_data = b"foo"
-    auth = mocker.Mock(
-        _keypair=mocker.Mock(algorithm=algorithm, public_data=key_data),
-    )
-    packet = mocker.Mock()
-
-    strings = iter((b"ed21556", key_data))
-    packet.get_string = lambda: next(strings)
-    with pytest.raises(ProtocolError):
-        _process_public_key_ok_gh(auth, None, None, packet)
-
-    strings = iter((b"ssh-rsa", key_data))
-    packet.get_string = lambda: next(strings)
-    _process_public_key_ok_gh(auth, None, None, packet)
-
-
 @pytest.mark.skipif(os.name != "nt", reason="Windows only")
 def test_git_bash_ssh_vendor(mocker):
     from dulwich.client import SubprocessSSHVendor