[H2] Basic auth uses timing-vulnerable plaintext comparison

[pradeepto]

Severity: High

Category

Authentication Failures (OWASP A07)

Files

internal/httpapi/middleware/basic_auth.go:39

Description

Password comparison uses == which short-circuits on the first mismatched byte. Leaks timing information about how many leading bytes match. No rate limiting makes this worse since an attacker can run many attempts quickly.

// line 39
if username == u.Username && password == u.Password {

Fix

import "crypto/subtle"

usernameMatch := subtle.ConstantTimeCompare([]byte(username), []byte(u.Username))
passwordMatch := subtle.ConstantTimeCompare([]byte(password), []byte(u.Password))
if usernameMatch == 1 && passwordMatch == 1 {
    authorized = true
    break
}

[mvanhorn]

Implemented in #322 - replaced the == credential check with crypto/subtle.ConstantTimeCompare, computing both field comparisons before combining them.