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security: stop OAuth token logging and enforce localhost MCP bind #19

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security: stop OAuth token logging and enforce localhost MCP bind #19

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20 changes: 15 additions & 5 deletions server.py
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Original file line number Diff line number Diff line change
Expand Up @@ -308,10 +308,7 @@ def build_oauth1_client() -> OAuth1Client:
"Missing X_OAUTH_CONSUMER_KEY or X_OAUTH_CONSUMER_SECRET for OAuth1 signing."
)
access_token, access_secret = run_oauth1_flow()
if is_truthy(os.getenv("X_OAUTH_PRINT_TOKENS", "0")):
print("OAuth1 access token:", access_token)
print("OAuth1 access token secret:", access_secret)
LOGGER.info("OAuth1 access token: %s", access_token)
# Do not log or print OAuth1 tokens — persistent credential leak risk.
return OAuth1Client(
client_key=consumer_key,
client_secret=consumer_secret,
Expand Down Expand Up @@ -451,8 +448,21 @@ async def log_response(response: httpx.Response) -> None:
)


LOCAL_MCP_HOSTS = {"127.0.0.1", "localhost", "::1"}


def _validated_mcp_host() -> str:
host = os.getenv("MCP_HOST", "127.0.0.1").strip().lower()
if host not in LOCAL_MCP_HOSTS:
Comment on lines +451 to +456
raise RuntimeError(
f"MCP_HOST={host} is not allowed. xmcp must bind to localhost only "
f"(127.0.0.1, localhost, ::1)."
)
Comment on lines +457 to +460
return host


def main() -> None:
host = os.getenv("MCP_HOST", "127.0.0.1")
host = _validated_mcp_host()
port = int(os.getenv("MCP_PORT", "8000"))
mcp = create_mcp()
mcp.run(transport="http", host=host, port=port)
Expand Down