T09 · Insecure Skill Coding Practices
Error
- Location
- webapp/app.js:183
- Finding
- Replayable Wallet Challenges and Untrusted Telegram Identity Binding<![CDATA[ ## Vulnerability Details **File Location**: `webapp/app.js:183-244`, `server/index.js:28-59`, `lib/challenge.js:23-32` **Vulnerability Type**: Replay attack and broken identity binding **Risk Level**: High ### Vulnerable Code ```javascript // webapp/app.js:183-199 function generateChallenge() { const timestamp = Date.now(); const nonce = Math.random().toString(36).substring(2, 15); const userId = tg.initDataUnsafe?.user?.id || 'telegram_user'; const message = `Verify ownership of Chia wallet:\n${currentAddress}\n\nTimestamp: ${timestamp}\nNonce: ${nonce}\nUser: ${userId}`; challengeData = { message, nonce, timestamp, address: currentAddress, userId }; elements.challengeMessage.textContent = message; elements.challengeSection.classList.remove('hidden'); console.log('📝 Challenge generated:', challengeData); } ``` ```javascript // webapp/app.js:233-244 const verificationData = { address: currentAddress, message: challengeData.message, signature: signature, publicKey: currentPublicKey, userId: challengeData.userId, timestamp: challengeData.timestamp }; // Send data back to Telegram bot tg.sendData(JSON.stringify(verificationData)); ``` ```javascript // server/index.js:28-59 const { address, message, signature, publicKey, userId, timestamp } = req.body; // Validate request if (!address || !message || !signature) { return res.status(400).json({ success: false, error: 'Missing required fields: address, message, signature' }); } // Validate timestamp (challenge must be recent) if (!validateChallengeTimestamp(timestamp)) { return res.status(400).json({ success: false, error: 'Challenge expired. Please generate a new one.' }); } const result = await verifySignature(address, message, signature, publicKey); if (result.verified) { pendingVerifications.set(userId, { address, verified: true, timestamp: Date.now() }); } ``` ```javascript // lib/challenge.js:23-32 f ...[truncated 2301 chars]
- Remediation
- <![CDATA[ ## Remediation Suggestions 1. Generate challenges exclusively on the trusted server using `crypto.randomBytes()` or `crypto.randomUUID()`. 2. Store each challenge with its nonce, expected Telegram user ID, expected wallet address, issuance time, expiration time, and unused/used state. 3. Validate Telegram Web App `initData` using Telegram's documented HMAC procedure. Do not authorize users based on `initDataUnsafe`. 4. Reconstruct the expected message on the server rather than accepting an arbitrary client-provided message. 5. Require an exact identity match between the verified Telegram user and the user bound to the stored challenge. 6. Enforce both timestamp bounds: ```javascript const age = Date.now() - issuedAt; const valid = age >= 0 && age <= FIVE_MINUTES; ``` 7. Atomically mark the nonce as consumed after successful verification and reject all subsequent attempts. 8. Expire and remove unused challenges after a short interval. 9. Ensure bot-side handlers bind successful verification to `msg.from.id`, not a `userId` supplied in Web App payload data. ]]>