[keilynrp]

Closes #422.

Why

python-jose was the only reason ecdsa, rsa and pyasn1 were in the backend image. ecdsa carried PYSEC-2026-1325 (CVE-2024-23342, the Minerva timing attack on ECDSA signing), and no version fixes it. So it sat in the pip-audit baseline as a permanent exception, re-justified every quarter, for a library UKIP never used. UKIP signs HS256 only, which PyJWT covers with no dependencies.

Changes

Code	backend/auth.py, routers/auth_users.py and routers/ws.py import PyJWT. PyJWTError keeps the JWTError name, so the six except sites catch every refusal as before. The key-rotation loop is unchanged
Dependencies	PyJWT==2.15.1 in; python-jose, ecdsa, rsa and pyasn1 out
Security gate	PYSEC-2026-1325 is removed, not ignored. pip-audit: No known vulnerabilities found, 6 ignored (chromadb and oauthlib only)

Nobody is signed out

test_jwt_library.py pins an access token and a refresh token minted by python-jose 3.5.0 with production's claims; the refresh token is signed with a retiring key. Both decode under PyJWT.

The same file checks that:

• every refusal raises the type the call sites catch (expired, unknown key, tampered, unsigned alg: none, HS512 with the real key, garbage);
• only HS256 is accepted;
• nothing in backend/ imports jose.

Verified

• The JWT, SSO and session tests (55) pass with python-jose uninstalled.
• The lock matches the real image, checked the way the lock's header requires: built Dockerfile.backend and compared its pip freeze.
  • Nothing is installed that the lock doesn't pin.
  • PyJWT is in, and the four packages are out.
  • The only change to the lock-only set is those four leaving it.
• Pre-push: full backend suite, 4408 passed / 10 skipped. Changed-file Ruff gate 0; lint ratchet exact.
• CI green

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