security: stop OAuth token logging and enforce localhost MCP bind#19
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iws17 wants to merge 1 commit into
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security: stop OAuth token logging and enforce localhost MCP bind#19iws17 wants to merge 1 commit into
iws17 wants to merge 1 commit into
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Remove unconditional OAuth1 access-token logging and the debug print branch. Reject MCP_HOST values outside localhost to avoid accidental exposure of the generated X API tool surface. Co-authored-by: Cursor <cursoragent@cursor.com>
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Pull request overview
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This PR tightens security by preventing OAuth1 credential leakage in logs and by ensuring the MCP server only binds to loopback interfaces.
Changes:
- Removed logging/printing of OAuth1 access tokens in
build_oauth1_client. - Added
MCP_HOSTvalidation to restrict binding to localhost/loopback addresses.
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| LOCAL_MCP_HOSTS = {"127.0.0.1", "localhost", "::1"} | ||
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| def _validated_mcp_host() -> str: | ||
| host = os.getenv("MCP_HOST", "127.0.0.1").strip().lower() | ||
| if host not in LOCAL_MCP_HOSTS: |
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| raise RuntimeError( | ||
| f"MCP_HOST={host} is not allowed. xmcp must bind to localhost only " | ||
| f"(127.0.0.1, localhost, ::1)." | ||
| ) |
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| def _validated_mcp_host() -> str: | ||
| host = os.getenv("MCP_HOST", "127.0.0.1").strip().lower() |
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Summary
LOGGER.infoof OAuth1 access tokens inbuild_oauth1_client()and drop theX_OAUTH_PRINT_TOKENSdebug-print branch._validated_mcp_host()soMCP_HOSTmust be127.0.0.1,localhost, or::1— prevents accidental wide bind of the generated X API MCP surface.Related: overlaps with #17 (OAuth logging) but also removes the debug-print path and adds the localhost bind guard.
Test plan
MCP_HOST— binds on localhostMCP_HOST=0.0.0.0— startup fails with clear errorMade with Cursor