2546 - Backend accepts expired OTPs

[Md-Humair-KK]

#2546

Summary by CodeRabbit

• Bug Fixes
  • Expired OTPs are rejected, with an error prompting the user to request a new one.
  • OTPs whose issue time cannot be validated are also rejected.
  • OTPs within the configured validity period continue to be accepted; password authentication is not affected by OTP expiry checks.
• Configuration
  • The OTP validity period can be configured. If no valid positive value is provided, the system uses a five-minute default.

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ℹ️ Recent review info

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Configuration used: Repository UI

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Plan: Advanced

Run ID: a635dbf1-e868-4a62-81ff-d90e687bf347

📥 Commits

Reviewing files that changed from the base of the PR and between 73110f9 and 5ac8920.

📒 Files selected for processing (2)

• esignet-service/internal/engine/mock/authenticator.go
• esignet-service/internal/engine/mock/authenticator_test.go

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Walkthrough

The OTP executor records the time of a successful OTP send. Mock authentication checks the timestamp against a configurable validity period and returns InvalidOTPError for malformed or expired timestamps.

Changes

OTP Expiry Validation

Layer / File(s)	Summary
Expiry contract and configuration esignet-service/internal/engine/shared/errors.go, esignet-service/internal/engine/mock/config.go	Adds InvalidOTPError and configures OTPValiditySeconds from the environment, with a 300-second fallback for invalid or non-positive values.
Record OTP issue time esignet-service/internal/engine/executors/otp_executor.go, esignet-service/internal/engine/executors/otp_executor_test.go	After a successful OTP send, stores the current UTC time in RFC3339 format. The test checks that the stored timestamp is valid and within the execution time bounds.
Validate OTP age during authentication esignet-service/internal/engine/mock/authenticator.go, esignet-service/internal/engine/mock/authenticator_test.go	Checks the issue timestamp before sending the authentication request. Missing metadata skips the check; malformed or expired timestamps return InvalidOTPError. Tests cover these cases, a fresh timestamp, and password challenges.

Priority: ➖ Normal

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

Change: Bug fix

Sequence Diagram(s)

sequenceDiagram
  participant OTPExecutor
  participant RuntimeData
  participant mockAuthnProvider
  participant KYCAuthRequest
  OTPExecutor->>RuntimeData: Store successful OTP issue time
  mockAuthnProvider->>RuntimeData: Read issue-time metadata
  mockAuthnProvider->>mockAuthnProvider: Check timestamp and validity period
  alt Timestamp is valid
    mockAuthnProvider->>KYCAuthRequest: Send authentication request
  else Timestamp is malformed or expired
    mockAuthnProvider-->>mockAuthnProvider: Return InvalidOTPError
  end

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Suggested reviewers: anushasunkada

Merge Risk: ⚪ Minimal · up to 5ac89

OTP authentication now rejects expired or malformed issue timestamps while password authentication bypasses the expiry check. No concrete merge-blocking issue remains in the supplied evidence; proceed subject to normal checks.

Security Architecture Review

Security architecture risk: 🔵 Low · up to 5ac89

The change adds expiry protection to mock OTP authentication without demonstrating a new exploitable weakness. However, expiry remains conditional on timestamp availability, and its effectiveness across resends, interrupted flows, and deployed configurations is not fully established.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — The expiry-control exposure is bounded to OTP authentication handled by the mock provider in configured service instances. Its maximum affected user or tenant population depends on deployment and flow configuration, which remains unavailable; test methods labeled as public entrypoints do not establish remote exposure.

Security Findings and Attack Paths

• inferred — The deferred missing-timestamp candidate is not a verified attack path. The provider permits absent timestamps, but a remotely reachable path that omits trusted issuance metadata was not established. Likewise, accepting an old OTP after resend would require downstream behavior that was not verified. Neither condition was demonstrated to be introduced or worsened by this PR.

Trust Boundaries and Controls

• observed — In the examined metadata builder, provider extension values come from runtime state, while initiator headers and query parameters use separate namespaces. This prevents those request fields from directly replacing the issue timestamp through this builder, but does not resolve every upstream runtime-state writer or the external authentication executor's handoff.
• observed — Issuance and authentication can reuse a transaction ID already present in runtime metadata, and the transaction-ID executor seeds that ID from the flow execution. This is counterevidence to necessarily different transaction IDs, but does not itself prove binding of the age timestamp to a particular OTP generation.

Resilience and Maintainability Implications

• inferred — The in-memory store provides locking and atomic storage operations, but those primitives do not prove atomic OTP issuance, timestamp persistence, and authentication as a combined transition. Interruption after downstream issuance, concurrent resend/authentication, cleanup, and single-use consumption remain lifecycle coverage gaps rather than observed defects.

Hardening Proposals

• proposed — Define when missing issue-time metadata is an allowed compatibility state and when it must reject OTP authentication. Validate that policy through the actual authentication executor and recovery path before making enforcement fail closed.
• proposed — Make resend invalidation and OTP consumption explicit parts of the provider contract. Verify that an old OTP cannot inherit a refreshed timestamp and that partial issuance failures and concurrent requests preserve the intended challenge age and identity.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 33.33% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 12 functions across 9 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly identifies the main change: preventing the backend from accepting expired OTPs. It is concise and specific.
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.

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_{An OTP takes its place in time
A fresh one passes the check
An old one calls for a new request
A clear timestamp guides the flow
The mock returns the right response}

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Codecov Report

❌ Patch coverage is 88.00000% with 3 lines in your changes missing coverage. Please review.
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Files with missing lines	Patch %	Lines
esignet-service/internal/engine/mock/config.go	57.14%	2 Missing and 1 partial ⚠️
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Additional details and impacted files

@@              Coverage Diff              @@
##             develop-go    #2657   +/-   ##
=============================================
  Coverage              ?   70.57%           
=============================================
  Files                 ?      131           
  Lines                 ?     9091           
  Branches              ?      112           
=============================================
  Hits                  ?     6416           
  Misses                ?     2214           
  Partials              ?      461           

Flag	Coverage Δ
go	69.45% <88.00%> (?)
npm	92.53% <ø> (?)

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Actionable comments posted: 1

---

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🤖 Prompt to fix review comments

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Inline comments:
Review comments at @esignet-service/internal/engine/mock/authenticator.go:
- Around line 109-111: In the authentication flow, guard the checkOTPExpiry call
with a check that kycAuthRequest.Otp is non-empty, so OTP expiry validation runs
only for OTP challenges. Add a password test with expired OTP metadata to verify
the password challenge is not rejected by the OTP check.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: ASSERTIVE

Plan: Advanced

Run ID: 73c64022-8697-4291-9d61-92d0dbda46ba

📥 Commits

Reviewing files that changed from the base of the PR and between 839e561 and 73110f9.

📒 Files selected for processing (5)

• esignet-service/internal/engine/executors/otp_executor.go
• esignet-service/internal/engine/executors/otp_executor_test.go
• esignet-service/internal/engine/mock/authenticator.go
• esignet-service/internal/engine/mock/authenticator_test.go
• esignet-service/internal/engine/mock/config.go

Included review availability: This review used your included allowance. Your plan provides up to 1 included review per hour; 0 remain after this review.