[D3SOX]

The OpenTubeX app can't tell whether an opentubex://oidc?token=… callback belongs to the sign-in it started. While a sign-in waits, any page in the user's browser can open a callback with a token for another account on the same server. The app then signs into that account and uploads the user's history and subscriptions to it.

GET /v1/account/oidc/authenticate and POST /v1/account/oidc/delete now take an optional state of 1 to 128 characters from A-Z, a-z, 0-9, - and _. The server keeps it with the flow and adds it to the redirect, next to token for sign-ins. GET /meta reports oidc_state: true, so the app knows it can require the state. Clients that send no state get the same redirects as before. The server now builds the deletion redirect before it deletes the account, so a bad redirect URL can't leave a deleted account without a redirect.

The app side is OpenTubeX/OpenTubeX#2981.

Proof: cargo test (new tests for redirect parameters and state validation, updated /meta and OpenAPI parameter tests), cargo fmt --check and cargo clippy --all-targets. I also ran this branch with a mock OIDC provider. A sign-in with state redirected to opentubex://oidc/?token=…&state=…, one without kept the old redirect, and an invalid state got a 400.

Reviewed with sol-loop: 2 rounds with gpt-6.1-sol on xhigh (round 1) and high (round 2).
Sol verdict: approved

Changes made by Claude Opus 5.5 in Claude Code (T3 Code).

[coderabbitai]

Walkthrough

OIDC login and deletion requests now accept optional client state. The server validates and retains state through the callback, then includes it in the client redirect when supplied. The metadata response advertises this capability, and the README documents the request formats and behavior.

Changes: OIDC Client State

Layer / File(s)	Summary
Request validation and callback context src/handlers/user.rs	Login and deletion requests accept optional state. The handlers validate it and store it with the callback context.
Callback redirects and tests src/handlers/user.rs	Callbacks append supplied state to redirect URLs. Tests cover redirect parameters, state validation, and the authentication OpenAPI parameter.
Capability metadata and documentation src/dto.rs, src/handlers/health.rs, src/route_tests.rs, README.md	The metadata response reports oidc_state: true. The README describes the optional state inputs and redirect behavior.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Feature

Sequence Diagram(s)

sequenceDiagram
  participant OIDCClient
  participant OIDCHandlers
  participant CallbackContext
  OIDCClient->>OIDCHandlers: Submit login or deletion request with optional state
  OIDCHandlers->>CallbackContext: Store state with redirect context
  CallbackContext-->>OIDCHandlers: Provide stored state to callback
  OIDCHandlers-->>OIDCClient: Redirect with token and optional state

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Possibly related PRs

• OpenTubeX/sync-server#32: This PR extends the same OIDC login and deletion flows that PR #32 changed.
• OpenTubeX/sync-server#33: This PR adds oidc_state to the /meta capability contract that PR #33 restructured.
• OpenTubeX/sync-server#31: This PR extends the MetaResponseCapabilities contract introduced by PR #31.

Suggested reviewers: bnyro

Merge Risk: Minimal · up to 4b250

Client state is retained through both callback flows and returned in the redirect when supplied. No merge-blocking issue is established.

Security architecture risk: Low · up to 4b250

The change preserves existing account-identity checks and approved redirect destinations. A limited ambiguity remains when an approved callback URL already contains a state parameter. Client-side rejection of foreign callbacks has not been verified.

Retained concerns

• Low · architecture · inferred: If an operator-approved redirect URL already contains a state query parameter, the new helper appends another state value. Correlation then depends on the client's duplicate-parameter handling rather than an unambiguous server contract. Exact allowlisting limits the condition to configured destinations; client rejection or a security bypass has not been demonstrated.

Security review details

Security Blast Radius

• inferred — The changed contract reaches approved clients receiving account-session tokens or deletion completion. The identified query ambiguity requires a configured destination already containing state; ordinary request input cannot choose an arbitrary unapproved callback destination.

Security Findings and Attack Paths

• inferred — Appending state to a URL that already has that key creates a newly ambiguous correlation contract. A first-value consumer could reject a valid callback, while a last-value consumer could use the appended value. Downstream parsing is unavailable, so this does not establish acceptance of a foreign session.

Trust Boundaries and Controls

• observed — Attacker-supplied client state is bounded and encoded as a query value. It remains distinct from provider state, PKCE, and nonce verification. Returning it does not replace those controls or weaken the callback variant and account-subject checks.

Resilience and Maintainability Implications

• observed — The unchanged challenge store removes a provider challenge under a mutex before token exchange. Repeated or concurrent callbacks cannot reuse it, but provider or later database failures consume the flow and require fresh initiation. This recovery behavior predates the PR.

Hardening Proposals

• proposed — Define a single-value contract for reserved callback parameters, including state, by rejecting conflicting configured query keys or applying an explicit replacement policy. Clients should reject missing, duplicate, stale, or mismatched state before accepting a returned token.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documenta…	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Title check		The title clearly describes the main change: returning client-provided state with OIDC redirects so apps can reject sign-ins they did not start.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.
Description check		The description explains the OIDC state changes, metadata capability, redirect behavior, and reported tests. It is related to the changeset.

Full details: Docstring Coverage

Explanation

Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentation-only edits and deletions within surviving functions are included; unchanged diff context and fully deleted functions are excluded. Analyzed 9 functions across 4 files. (1 skipped: 1 unsupported.)

Resolution

Write docstrings for the functions missing them to satisfy the coverage threshold.

Finishing Touches

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Failed pre-merge checks:
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Write docstrings for the functions missing them to satisfy the coverage
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Commits

Reviewing files that changed from the base of the PR and between 99c7fe1 and 4b2507f.

Files selected for processing: 5

• README.md
• src/dto.rs
• src/handlers/health.rs
• src/handlers/user.rs
• src/route_tests.rs

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[D3SOX]

Note

🤖 Claude Opus 5.5 responding on behalf of Nico

Not addressing the Docstring Coverage warning. It measures the whole crate, not this diff. Both new functions, validate_oidc_client_state and client_redirect_url, have doc comments, and the new state fields on OidcAuthenticationRequest and OidcDeleteRequest are documented for the OpenAPI output. Adding docstrings to untouched handlers would be outside this PR.

[D3SOX]

Note

🤖 Claude Opus 5.5 responding on behalf of Nico

Leaving the duplicate state concern as is. It needs an operator to allow a redirect URL that already carries state, and the OpenTubeX apps use opentubex://oidc and opentubex-nightly://oidc, which have no query. If that ever happens, it fails closed: the app reads the first value with searchParams.get('state'), the static value doesn't match the random one it sent, and the sign-in keeps waiting instead of accepting the callback.