fix(redact): mask Cookie / Set-Cookie session tokens

[ly-wang19]

Summary

Follow-up to 6f0ecf37d ("mask all Authorization schemes and x-api-key style headers").

redact_sensitive_text masks Authorization / Proxy-Authorization and the x-api-key / api-key header family — the threat model that commit names is a logged request or echoed curl leaking live credentials. But Cookie / Set-Cookie headers were left untouched, so a session token — an account-takeover credential — leaks verbatim into logs, transcripts, and tool output.

Reproduced against current main:

>>> redact_sensitive_text("Cookie: sessionid=abcdef123456SECRET7890; csrftoken=xyz", force=True)
'Cookie: sessionid=abcdef123456SECRET7890; csrftoken=xyz'   # ← leaked
>>> redact_sensitive_text("Set-Cookie: session=topsecretvalue12345; HttpOnly; Path=/", force=True)
'Set-Cookie: session=topsecretvalue12345; HttpOnly; Path=/' # ← leaked
>>> redact_sensitive_text("authorization: Bearer sk-x", force=True)
'authorization: Bearer ***'                                  # (already masked)

Cookie carries arbitrarily many secret pairs (sessionid, csrftoken, auth tokens); Set-Cookie carries the cookie plus non-secret attributes (Path, HttpOnly, …). Neither is covered by the Authorization or x-api-key rules, and cookie is not in the JSON/query secret-key set.

Fix

Add a Cookie/Set-Cookie rule alongside the existing header rules. It masks each cookie value via _mask_token (the same masker used for Authorization/x-api-key, so the partial-reveal policy is consistent) while preserving cookie names and the non-secret Set-Cookie attributes (Path/Domain/Expires/Max-Age/SameSite + the HttpOnly/Secure flags) for debuggability. The value run stops at end-of-line or a closing quote so an inline curl -H 'Cookie: …' https://host doesn't swallow the trailing URL.

After the fix:

Cookie: sessionid=abcdef...7890; csrftoken=***
Set-Cookie: session=topsec...2345; HttpOnly; Path=/
curl -H 'Cookie: auth=***' https://api.example.com/v1/x

Tests

tests/agent/test_redact.py::TestCookieHeaders — Cookie multi-pair masking (names preserved), Set-Cookie value masked with attributes preserved, and a curl-command case (URL preserved). All three fail without the rule; the full suite (85 tests) passes with it.

[alt-glitch]

Duplicate of #50514 — same Cookie/Set-Cookie session-token masking in agent/redact.py (same _COOKIE_HEADER_RE mechanism via _mask_token, same follow-up to merged #50423). #50514 is the earlier, broader PR (it additionally covers JSON-serialized secret headers at the same on-disk request/response dump sink).

[ly-wang19]

Quick repro against current main (the gap this closes):

>>> redact_sensitive_text("Cookie: sessionid=abcdef123456SECRET7890; csrftoken=xyz", force=True)
'Cookie: sessionid=abcdef123456SECRET7890; csrftoken=xyz'   # ← session token leaks verbatim
>>> redact_sensitive_text("authorization: Bearer sk-x", force=True)
'authorization: Bearer ***'                                  # already masked by 6f0ecf37d

This is a direct follow-up to 6f0ecf3 — same threat model (a logged request / echoed curl leaking a live credential), just the Cookie / Set-Cookie family that the Authorization + x-api-key rules don't cover. Session cookies are account-takeover credentials, so the leak is higher-impact than an API key in some flows.

It's one self-contained rule mirroring the existing header logic (mask the value via _mask_token, keep cookie names + non-secret Set-Cookie attributes), with 3 regression tests that fail without it; the full test_redact.py suite (85) passes. Still merges cleanly on main.

CI hasn't been able to run yet (first-time contributor) — whenever a maintainer has a moment, could the workflows be approved here? Happy to adjust scope or rebase. Thanks!

[teknium1]

Thanks for addressing a real raw-header redaction gap: current main bb5fc723b67c still applies only Authorization and API-key header rules at agent/redact.py:595-610.

Problems

• agent/redact.py:158 excludes quote characters from the header payload. For Cookie: sid="opaque", the match stops after sid=; _COOKIE_PAIR_RE at line 161 then has no value to mask, leaving the opaque token unredacted. Please cover quoted cookie values while preserving the outer curl quotation behavior.
• This PR does not cover JSON-serialized "Cookie": "..." headers. Current main's JSON key matcher is at agent/redact.py:177-181; Cookie is absent there. The duplicate discussion correctly points to #50514, whose diff includes that sibling request-dump representation.

Suggested changes

• Add quoted-cookie regression cases and adjust the matcher accordingly.
• Consolidate the JSON-header path with the broader #50514 approach so both representations are protected.

Automated hermes-sweeper review.

[teknium1]

This excludes a quote at the start of a cookie value. Cookie: sid="opaque" therefore matches only sid=, so _COOKIE_PAIR_RE receives no value to mask and opaque remains outside the replacement. Please distinguish quoted cookie values from the outer curl-command quote and add a regression.