Resolve Unsigned Authentication Bypass and Forgeable Sessions in agent-spend-permissions - #139
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Resolve Unsigned Authentication Bypass and Forgeable Sessions in agent-spend-permissions#139mozluk wants to merge 1 commit into
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### Description
This pull request completely overhauls the session and authentication layer of `agent-spend-permissions` to close multiple critical and high-severity access control vulnerabilities (F-02, F-04)[cite: 30]. Previously, the application authorized mainnet USDC spending based on an unsigned, trivial-to-forge base64 session token, and verified SIWE signatures without asserting domain bindings or tracking nonces safely[cite: 30].
### Key Changes & Remediations
#### 1. Forgeable Session Mitigation (F-02)
* **Cryptographic Signatures:** The application no longer relies on an unsigned `Buffer.from("0xADDRESS:TIMESTAMP").toString('base64')` cookie to authorize operations[cite: 30]. `src/lib/session.ts` now wraps payloads with a strict `v1.<payload>.<mac>` standard authenticated by a constant-time HMAC-SHA256 signature using a mandatory `SESSION_SECRET`[cite: 30].
* **Route Protection:** All endpoints (`/api/wallet/create`, `/api/search`, `/api/chat`) that manipulate or spend on behalf of server wallets have been strictly transitioned to read exclusively from the new, signature-verified tokens[cite: 30].
#### 2. SIWE Verification Hardening (F-04)
* **ERC-6492 / ERC-1271 Support:** The `verify` route now utilizes `viem`'s `parseSiweMessage` and `verifySiweMessage` rather than a weak regex match[cite: 30]. This fully supports Smart Wallet signature recovery while correctly checking issue/expiry timestamps[cite: 30].
* **Domain Binding:** `SIWE_DOMAIN` enforcement (or `Host` header fallback) guarantees signatures obtained for other sites can no longer be replayed here[cite: 30].
#### 3. Stateless Nonces & Memory Leak Prevention (F-04)
* **Self-Authenticating Nonces:** Replaced the previous module-level `Set<string>` — which introduced severe memory leaks and erratic cross-instance sign-in failures — with stateless, HMAC-verified nonces that carry their own built-in `uint32` expiry[cite: 30].
* **Safe Replay Bounds:** Tracked nonces are opportunistically pruned and safely bounded to `10,000` concurrent uses to prevent memory exhaustion vectors.
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Description
This pull request completely overhauls the session and authentication layer of
agent-spend-permissionsto close multiple critical and high-severity access control vulnerabilities (F-02, F-04)[cite: 30]. Previously, the application authorized mainnet USDC spending based on an unsigned, trivial-to-forge base64 session token, and verified SIWE signatures without asserting domain bindings or tracking nonces safely[cite: 30].Key Changes & Remediations
1. Forgeable Session Mitigation (F-02)
Buffer.from("0xADDRESS:TIMESTAMP").toString('base64')cookie to authorize operations[cite: 30].src/lib/session.tsnow wraps payloads with a strictv1.<payload>.<mac>standard authenticated by a constant-time HMAC-SHA256 signature using a mandatorySESSION_SECRET[cite: 30]./api/wallet/create,/api/search,/api/chat) that manipulate or spend on behalf of server wallets have been strictly transitioned to read exclusively from the new, signature-verified tokens[cite: 30].2. SIWE Verification Hardening (F-04)
verifyroute now utilizesviem'sparseSiweMessageandverifySiweMessagerather than a weak regex match[cite: 30]. This fully supports Smart Wallet signature recovery while correctly checking issue/expiry timestamps[cite: 30].SIWE_DOMAINenforcement (orHostheader fallback) guarantees signatures obtained for other sites can no longer be replayed here[cite: 30].3. Stateless Nonces & Memory Leak Prevention (F-04)
Set<string>— which introduced severe memory leaks and erratic cross-instance sign-in failures — with stateless, HMAC-verified nonces that carry their own built-inuint32expiry[cite: 30].10,000concurrent uses to prevent memory exhaustion vectors.