Fix Insecure Webhooks in Hug
Insecure webhooks in Hug usually stem from a lack of origin verification. Without a cryptographic handshake, any script kiddie can POST spoofed payloads to your endpoint and trigger internal logic. To secure this, you must implement HMAC signature verification using a shared secret to ensure data integrity and authenticity.
The Vulnerable Pattern
import hug
@hug.post(‘/webhook-receiver’) def insecure_handler(body): # VULNERABILITY: No verification of the request source. # Anyone can send a POST request here and trigger the processing logic. process_event(body) return {‘status’: ‘accepted’}
The Secure Implementation
The hardened implementation introduces a mandatory HMAC-SHA256 signature check. The 'X-Hub-Signature-256' header is compared against a locally computed hash of the raw request body using a shared secret. Crucially, hmac.compare_digest is used to mitigate timing attacks, ensuring the comparison time doesn't leak information about the correct signature. The raw stream is used for hashing to ensure that whitespace or JSON formatting changes don't invalidate the signature.
import hug
import hmac
import hashlib
from falcon import HTTP_403
SECRET_TOKEN = b’your_hardened_shared_secret’
@hug.post(‘/webhook-receiver’)
def secure_handler(request, response, body=None):
# 1. Grab the signature from the headers
signature = request.get_header(‘X-Hub-Signature-256’)
if not signature:
response.status = HTTP_403
return {‘error’: ‘Missing signature’}
# 2. Get raw body for HMAC calculation
# Note: Hug/Falcon stream must be read carefully or handled via middleware
raw_payload = request.stream.read()
# 3. Compute expected HMAC
expected_sig = hmac.new(SECRET_TOKEN, raw_payload, hashlib.sha256).hexdigest()
# 4. Use constant-time comparison to prevent timing attacks
if not hmac.compare_digest(f'sha256={expected_sig}', signature):
response.status = HTTP_403
return {'error': 'Invalid signature'}
process_event(body)
return {'status': 'verified'}</code></pre>
Your Hug API
might be exposed to Insecure Webhooks
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