Fix broken cryptographic primitive protecting a secret in Koa
A hash, cipher, or random source that cannot carry the weight it has been given: MD5 or SHA-1 over a password, a DES or ECB cipher, or Math.random() producing a token. Each has a drop-in replacement in the standard library, so the fix is small - the cost of not making it is that the protection is decorative.
high likely Koa CWE-327 / OWASP A02:2021
The vulnerable pattern in Koa
This finding comes from the Koa fixture in the owlwarden test suite. This hash is fast, and speed is the attacker's advantage: a commodity GPU tries billions of candidates a second, so a leaked table of these hashes is a leaked table of the values behind them. Password hashing needs a deliberately slow algorithm with a per-value salt.
The corrected handler
Replace the primitive at the point of use; there is no middleware for this.
import { randomBytes, randomUUID, scrypt } from 'node:crypto'
// Tokens and session ids: unpredictable, not merely random-looking.
const sessionId = randomUUID()
const resetToken = randomBytes(32).toString('base64url')
// Passwords: a slow hash with a per-password salt. bcrypt and argon2 are
// equally correct; scrypt needs no dependency.
const salt = randomBytes(16)
const hash = await new Promise<Buffer>((resolve, reject) =>
scrypt(password, salt, 64, (error, key) => (error ? reject(error) : resolve(key))),
)If you are not using Koa
Use a slow, salted hash for passwords and a cryptographic random source for tokens. Both are in the Node standard library; neither needs a dependency.
Check your own repository
npx owlwarden scan
npx owlwarden explain weak-cryptoRuns on your machine. No account, no telemetry, no network unless you ask. In CI, SARIF uploads to code scanning and the exit code is the gate.
Other Koa checks
Rules with a tested Koa example.
- cors-permissive medium Cross-origin policy accepts any origin
- hardcoded-secret high Credential hardcoded in source
- insecure-cookie medium Cookie set without its protective attributes
- install-lifecycle-script medium Package declares an install-time script
- open-redirect medium Redirect target comes from the caller
- security-headers-missing medium Security headers are not configured
- sensitive-data-logged medium Sensitive data written to a log
- sql-injection high SQL query built by string interpolation
- ssrf high Server fetches a URL the caller controls
- stack-trace-leak high Stack trace leaked in error response