Require SNIP-12 request signing for high-value mutating billing endpoints in src/routes/billing.ts

[Jagadeeshftw]

Description

src/auth/challenge.ts already builds SNIP-12 typed data (CHALLENGE_TYPES, buildTypedChallenge) for wallet-signature login, but that pattern is not reused anywhere for individual mutating actions after login. src/routes/billing.ts mutating endpoints currently rely solely on the session bearer token plus an Idempotency-Key. For the highest-value billing mutations, require a fresh SNIP-12 signature over the specific request payload so a stolen/replayed session token alone cannot mutate billing state.

Requirements and context

• Extend the typed-data pattern from src/auth/challenge.ts with a BillingAction type covering profile/payment-method mutations
• Add a requireSignedAction middleware verifying the signature against the caller's known wallet public key before the handler runs
• Return a clear, non-sensitive 400 (not 401/403) when the signature is missing or invalid, distinct from session auth failures
• Must be secure, tested, and documented
• Should be efficient and easy to review

Suggested execution

Fork the repo and create a branch

git checkout -b feature/billing-request-signing

Implement changes

• Update/Write: src/routes/billing.ts
• Update/Write: src/auth/challenge.ts
• Add/Update tests: src/routes/billing.test.ts
• Add documentation: docs/routes/billing.md
• Include clear code comments and TS types
• Validate security assumptions

Test and commit

• Run tests: pnpm test
• Cover edge cases
• Include test output and security notes

Example commit message

feat: require SNIP-12 request signing on billing mutations

Guidelines

• Minimum 95 percent test coverage
• Clear documentation
• Timeframe: 96 hours

[heymide]

I'd like to be assigned to this issue. I'll deliver a clean, maintainable solution that matches the requirements.

Payout wallet (Stellar): GCJS6J54NK4FJFT5I4AUIOSFONKAM7GI6RRHWYH55TUY2WZAEIH2Q5D7
GrantFox OSS campaign — smart escrow payout on merge.

[devkryssie]

I’m interested in this issue because it aligns strongly with my backend, API, database, and blockchain development experience. I can extend the existing SNIP-12 signing flow to protect high-value billing mutations, implement secure request verification middleware, and add comprehensive tests for replay, invalid signatures, and edge cases. I’m committed to delivering a clean, well-documented, and security-focused implementation that integrates naturally with the existing architecture.