fix(auth): limit repeated authorization requests

[SimonFair]

Adds bounded handling for repeated authorization requests and callbacks.

Related to OS-982.
Depends on #2098 for shared dependency resolutions.
Verification: lint, type-check, build.

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Reviewing files that changed from the base of the PR and between 081a980 and 232bb69.

📒 Files selected for processing (1)

• api/src/unraid-api/graph/resolvers/sso/session/oidc-state.service.ts

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Walkthrough

The API applies throttling to the OIDC authorize and callback routes. OIDC parameter validation enforces input types and length limits. OIDC state generation and validation track active nonces and release them on expiration or failure.

Changes

OIDC Protections

Layer / File(s)	Summary
Configure HTTP throttling api/src/unraid-api/auth/fastify-throttler.guard.ts, api/src/unraid-api/rest/rest.module.ts, api/src/unraid-api/app/app.module.ts, api/src/unraid-api/rest/rest.controller.ts	The REST module registers the throttling module and guard. The guard supports HTTP contexts and fallback throttling options. The app module no longer configures global throttling. The authorize and callback routes use the guard with a limit of 10 requests per 60,000 ms.
Validate OIDC request parameters api/src/unraid-api/graph/resolvers/sso/utils/oidc-request-handler.util.ts	Authorization and callback validation rejects non-string or empty inputs. Authorization validation also enforces maximum lengths for provider IDs, state values, and redirect URIs.
Track and validate OIDC state api/src/unraid-api/graph/resolvers/sso/session/oidc-state.service.ts	State generation validates inputs, tracks active nonces, and releases them when expired or when cache operations or validation fail.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Bug fix

Merge Risk: ⚪ Minimal · up to 232bb

The OIDC routes receive their route-level limits, and the removed configuration was not enforcing limits on the other inspected routes. The suspected state-counter bypass was refuted; no actionable merge risk is established.

Security Architecture Review

Security architecture risk: 🟡 Moderate · up to 232bb

The new protections bound resource use, but unauthenticated requests can occupy shared sign-in capacity and temporarily prevent other users from starting authentication. Request throttling and state expiry limit the impact, while enforcement across multiple server instances remains unconfirmed.

Retained concerns

• Medium · security · inferred: Unauthenticated callers can consume the new shared sign-in budget without completing identity-provider authentication. Thirty-two abandoned authorization requests for one configured provider and accepted redirect URI exhaust that scope for other users served by the same state-service instance. The ten-per-minute request limit still permits this accumulation within the ten-minute state lifetime. Recovery depends on consumption or expiry; provider and process limits can extend the affected scope when enough valid redirect scopes and providers are available.

Security review details

Security Blast Radius

• inferred — The introduced exhaustion path affects authentication availability for users sharing a provider and redirect scope on the same serving instance. Broader provider or instance exhaustion depends on available configured scopes and providers. It requires no authenticated user or identity-provider credentials; it does require requests that pass provider and redirect checks. Privileged session creation, other services, and infrastructure authority are not established outcomes of this path.

Security Findings and Attack Paths

• inferred — A caller can repeatedly initiate authorization for one accepted scope and abandon the returned redirects. The resulting reservations exhaust the 32-state shared budget and reject subsequent legitimate initiations. Expiry and pruning bound each reservation's lifetime, but the ten-per-minute source limit permits exhaustion before the first reservation expires. This is an introduced quota-contention concern, not an observed production outage.

Trust Boundaries and Controls

• observed — Public query parameters remain untrusted. The authorize endpoint validates their shape and redirect destination before state creation. Callback processing rejects invalid state before using cached client state, redirect URI, and PKCE context for token exchange, and authorization checks still precede session creation.

Resilience and Maintainability Implications

• observed — State consumption uses separate awaited cache read and delete operations, and validation does not require active-map membership. This sequence predates the PR, so the new accounting does not establish atomic single-use consumption, but the comparison does not show an introduced replay weakness. Effective cache serialization remains unconfirmed.

Hardening Proposals

• proposed — Combine shared resource safety caps with requester-scoped admission or fairness controls, and give authorization initiation an explicit reservation cleanup path when URL construction or discovery fails. Define whether those budgets must apply across all serving instances.
• proposed — Address the pre-existing concurrent-consumption limitation with an atomic nonce-consume operation or equivalent serialization, rather than treating admission counters as replay protection.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 5…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly describes the main change: limiting repeated authorization requests. This matches the OIDC throttling and pending-state capacity changes.

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_{A rabbit checks each state at dawn
And counts the nonces one by one
The routes now slow their rapid pace
Bad inputs find a guarded place
The cache lets go when states are done}

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[chatgpt-codex-connector]

Scope pending-state limits to the requesting client

This bucket is shared by every user of the same OIDC provider and callback URI, rather than by the requester. Because the public authorize route only rate-limits each tracker, a client can leave 32 normal authorization redirects unfinished within the ten-minute state TTL; generateSecureState then throws for all unrelated users trying to sign in through that provider and callback, which the REST controller returns as a 400. Include a requester-specific key in this limit (or remove the shared bucket cap) so one client cannot deny SSO to others.

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[codecov]

Codecov Report

❌ Patch coverage is 79.26829% with 34 lines in your changes missing coverage. Please review.
✅ Project coverage is 53.43%. Comparing base (d4d9733) to head (232bb69).

Files with missing lines	Patch %	Lines
.../graph/resolvers/sso/session/oidc-state.service.ts	76.63%	25 Missing ⚠️
api/src/unraid-api/auth/fastify-throttler.guard.ts	65.00%	7 Missing ⚠️
...h/resolvers/sso/utils/oidc-request-handler.util.ts	94.73%	1 Missing ⚠️
api/src/unraid-api/rest/rest.controller.ts	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2094      +/-   ##
==========================================
+ Coverage   53.38%   53.43%   +0.05%     
==========================================
  Files        1044     1044              
  Lines       72705    72841     +136     
  Branches     8399     8434      +35     
==========================================
+ Hits        38811    38926     +115     
- Misses      33767    33788      +21     
  Partials      127      127              

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Actionable comments posted: 1

---

• 🪄 Fix CodeRabbit comments on this PR

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Inline comments:
Review comments at
@api/src/unraid-api/graph/resolvers/sso/session/oidc-state.service.ts:
- Around line 68-69: Update the capacity check in OidcStateService so
pending-state limits are isolated by a trusted provider or client scope rather
than shared across all requests. Retain a separate aggregate safety cap sized
for expected concurrent authorization load, and do not use caller-controlled
clientState as the scope key.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Advanced

Run ID: c3d47c91-f235-4e58-965d-ef69aec5c8d5

📥 Commits

Reviewing files that changed from the base of the PR and between d4d9733 and 4513255.

📒 Files selected for processing (6)

• api/src/unraid-api/app/app.module.ts
• api/src/unraid-api/auth/fastify-throttler.guard.ts
• api/src/unraid-api/graph/resolvers/sso/session/oidc-state.service.ts
• api/src/unraid-api/graph/resolvers/sso/utils/oidc-request-handler.util.ts
• api/src/unraid-api/rest/rest.controller.ts
• api/src/unraid-api/rest/rest.module.ts

💤 Files with no reviewable changes (1)

• api/src/unraid-api/app/app.module.ts

Included review availability: This review used your included allowance. Your plan provides up to 2 included reviews per hour; 1 remain after this review.