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Fix ssh-agent proxy hang with newer openssh clients #241

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Merged
bluesliverx merged 1 commit into from
Sep 18, 2026
Merged

Fix ssh-agent proxy hang with newer openssh clients #241

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16 changes: 14 additions & 2 deletions buildrunner/sshagent/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -336,11 +336,13 @@ def forward_agent_handler(self, remote_channel):
_ct.start()


SSH2_AGENT_FAILURE = bytes([30])
SSH2_AGENT_FAILURE = bytes([5])
SSH2_AGENTC_REQUEST_IDENTITIES = 11
SSH2_AGENT_IDENTITIES_ANSWER = bytes([12])
SSH2_AGENTC_SIGN_REQUEST = 13
SSH2_AGENT_SIGN_RESPONSE = bytes([14])
SSH_AGENTC_EXTENSION = 27
SSH_AGENT_EXTENSION_FAILURE = bytes([28])


class CustomAgentConnectionThread(threading.Thread):
Expand Down Expand Up @@ -373,9 +375,19 @@ def run(self):
self._agent_identities_answer()
elif r_type == SSH2_AGENTC_SIGN_REQUEST:
self._agent_sign_response(request)
elif r_type == SSH_AGENTC_EXTENSION:
# e.g. session-bind@openssh.com sent by newer
# openssh clients (9.x+); we don't support any
# extensions, so reply with the well-formed
# extension-failure response type.
msg = Message()
msg.add_byte(SSH_AGENT_EXTENSION_FAILURE)
self._send_reply(msg)
else:
# return FAILURE message for everything else
self._send_reply(SSH2_AGENT_FAILURE)
msg = Message()
msg.add_byte(SSH2_AGENT_FAILURE)
self._send_reply(msg)
except SSHException:
raise
except Exception: # pylint: disable=broad-except
Expand Down
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