* studio: proxy-aware login rate-limit; allow google favicons in CSP
Two follow-ups to #5375's auth + headers hardening.
Login rate-limit:
The per-IP bucket keyed on request.client.host alone. Behind any
reverse proxy or shared NAT it lumps everyone together (one user's
typos lock everyone out for 60 seconds; the 429 detail leaked the
proxy/internal IP back to clients). The bucket key is now
(client-ip, username.lower) so:
- one wrong-password run does not block another user from the same IP
- one IP does not block the same user from a different IP
The 429 detail body no longer interpolates the IP. Behind a proxy
clients can set UNSLOTH_STUDIO_TRUST_FORWARDED=1 so the limiter
honours X-Forwarded-For / Forwarded; off by default so a direct
caller cannot spoof the header.
CSP img-src:
components/assistant-ui/sources.tsx renders citation favicons from
https://www.google.com/s2/favicons. The current img-src allows
t0..t3.gstatic.com (used for other Google-hosted icons) but not the
main host the favicon URL points to, so every citation icon
CSP-blocks and falls back to gray initials. Adding www.google.com to
img-src is the same shape as #5409's connect-src HF allowlist fix.
Tests:
- test_login_rate_limit.py (new): _client_ip respects
UNSLOTH_STUDIO_TRUST_FORWARDED for X-Forwarded-For and Forwarded;
bucket key is composed of (ip, lower(username)) and isolates
cross-user and cross-IP buckets; 429 detail does not contain the
client IP; Retry-After header preserved.
- test_middleware.py: new test_img_src_allows_google_favicons pins
that www.google.com is in the img-src directive and the existing
gstatic CDNs stay allowed.
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* studio: normalise forwarded IPs, IP-wide aggregate cap, unknown-user sentinel
Reviewer follow-ups to the proxy-aware login rate-limit PR.
Forwarded address normalisation: with
UNSLOTH_STUDIO_TRUST_FORWARDED=1, raw `X-Forwarded-For` and
`Forwarded: for=` values such as `198.51.100.7:50001` or
`"[2001:db8::1]:50001"` were carried verbatim into the bucket key,
so one client emitting a fresh source port per attempt split into
many buckets and bypassed _LOGIN_MAX_FAILS. _normalize_forwarded_addr
now strips quotes, optional `[..]:port` for IPv6 and `host:port` for
IPv4, and validates as an IP literal; garbage values fall through to
the direct request.client.host. Forwarded parsing also isolates the
first forwarded-element so a multi-element header cannot create
attacker-controlled bucket strings.
Spray protection: the (ip, username) key removed the aggregate
per-IP throttle the pre-PR limiter provided. A client rotating
nonexistent usernames produced [401, 401, 401, 401, 401, 401] where
pre-PR produced [401, 401, 401, 401, 401, 429]. Restored the
aggregate via a parallel _LOGIN_IP_BUCKETS table (max 30 fails / 60s
per IP) checked alongside the per-(ip, username) bucket; both
buckets must be cleared on a successful login.
Bucket cardinality: every distinct unauthenticated username
allocated a new (ip, username) bucket entry without bound. 1,000
random usernames from one IP produced 1,000 buckets. Failures whose
username does not exist now record into a single sentinel key
(ip, "\x00unknown-user") so cardinality stays at one per IP for the
unknown path. The known-user path additionally enforces a global
hard cap (_LOGIN_MAX_BUCKETS = 4096) that prunes stale empty buckets
on overflow and otherwise folds the failure into the per-IP bucket
only.
Test:
- python -m pytest studio/backend/tests/test_login_rate_limit.py -q
-> 19 passed (was 12 before this commit; +5 forwarded-address
normalisation, +1 sentinel bucket, +1 bucket cap)
CSP comment refreshed to mention `www.google.com` alongside
*.gstatic.com so future readers see why the host is allowlisted.
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* studio: tokenise img-src assertion to silence CodeQL substring rule
The new CSP google-favicon test used 'host string in directive string'
which CodeQL flagged as py/incomplete-url-substring-sanitization
(the substring could appear at an arbitrary position in a URL).
The assertion is checking a CSP directive, not URL sanitisation, but
splitting the directive on whitespace and asserting against the
tokenised source list expresses the same intent and matches the
exact CSP source expression. CodeQL no longer treats it as a URL
substring check.
Test: python -m pytest studio/backend/tests/test_middleware.py -q
-> 14 passed
* studio: use any(src == host) for CSP source asserts
CodeQL's py/incomplete-url-substring-sanitization still flagged the
tokenised "host in img_sources" check. Switching to
`any(src == host for src in img_sources)` makes the comparison an
exact-equality (not substring) match, which the rule does not flag.
Test: python -m pytest studio/backend/tests/test_middleware.py -q
-> 14 passed
* studio: trim verbose rate-limit + CSP comments
Compress the 6-line constants header on _LOGIN_BUCKETS to 3 lines and
the per-helper docstrings on _trust_forwarded_for / _normalize_forwarded_addr
to one line each. Same code, fewer in-flow tutorials.
Note in the CSP comment that www.google.com is the active favicon host
(used by sources.tsx for s2/favicons citations); *.gstatic.com stays as
legacy faviconV2 coverage but the SPA no longer fetches it.
33 tests in test_login_rate_limit.py + test_middleware.py still pass.
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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
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