GHSA-5vhg-9xg4-cv9m

### Summary

A malicious JSON-stringifyable message can be made passing on `verify()`, when global Buffer is [`buffer` package](https://www.npmjs.com/package/buffer)

### Details

This affects only environments where `require('buffer')` is <https://npmjs.com/buffer> E.g.: browser bundles, React Native apps, etc.

`Buffer.isBuffer` check can be bypassed, resulting in strange objects being accepted as `message`, and those messages could trick `verify()` into returning false-positive `true` values

v2.x is unaffected as it verifies input to be an actual `Uint8Array` instance

Such a message can be constructed for any already known message/signature pair There are some restrictions though (also depending on the known message/signature), but not very limiting, see PoC for example

https://github.com/bitcoinjs/tiny-secp256k1/pull/140 is a subtle fix for this

### PoC

This code deliberately doesn't provide `reencode` for now, could be updated later

```js import { randomBytes } from 'crypto' import tiny from 'tiny-secp256k1' // 1.1.6

// Random keypair const privateKey = randomBytes(32) const publicKey = tiny.pointFromScalar(privateKey)

const valid = Buffer.alloc(32).fill(255) // let's sign a static buffer const signature = tiny.sign(valid, privateKey)

// Prevent processing any unverified data by fail-closed throwing function verified(data, signature) { if (!Buffer.isBuffer(data)) data = Buffer.from(data, 'hex') if (!tiny.verify(data, publicKey, signature)) throw new Error('Signature invalid!') return new Uint8Array(data) }

function safeProcess(payload) { const totally = JSON.parse(payload) // e.g. json over network

const message = verified(totally, signature) console.log(message instanceof Uint8Array) console.log(Buffer.from(message).toString('utf8')) }

const payload = reencode(valid, "Secure contain protect") safeProcess(payload) ```

Output (after being bundled): ```console true Secure contain protect���� ```

### Impact

Malicious messages could crafted to be verified from a given known valid message/signature pair