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"""
Module: api.middleware.webhook_verification
Description: Webhook signature verification middleware
Author: Anderson H. Silva
Date: 2025-01-25
License: Proprietary - All rights reserved
"""
import hmac
import hashlib
import time
from typing import Optional, Dict, Any
from fastapi import Request, HTTPException, status
from starlette.middleware.base import BaseHTTPMiddleware
from starlette.responses import JSONResponse
from src.core import get_logger
logger = get_logger(__name__)
class WebhookVerificationMiddleware(BaseHTTPMiddleware):
"""
Middleware for verifying incoming webhook signatures.
Protects endpoints that receive webhooks from external services.
"""
def __init__(
self,
app,
webhook_paths: Optional[Dict[str, str]] = None,
max_timestamp_age: int = 300 # 5 minutes
):
"""
Initialize webhook verification middleware.
Args:
app: FastAPI application
webhook_paths: Dict of path -> secret mapping
max_timestamp_age: Maximum age of timestamp in seconds
"""
super().__init__(app)
self.webhook_paths = webhook_paths or {}
self.max_timestamp_age = max_timestamp_age
async def dispatch(self, request: Request, call_next):
"""Process request with webhook verification."""
# Check if this is a webhook path
if request.url.path not in self.webhook_paths:
return await call_next(request)
# Get the secret for this path
secret = self.webhook_paths[request.url.path]
try:
# Read body
body = await request.body()
# Verify signature
if not self._verify_signature(request, body, secret):
logger.warning(
"webhook_signature_verification_failed",
path=request.url.path,
headers=dict(request.headers)
)
return JSONResponse(
status_code=status.HTTP_401_UNAUTHORIZED,
content={
"detail": "Invalid webhook signature",
"error": "INVALID_SIGNATURE"
}
)
# Verify timestamp if present
if not self._verify_timestamp(request):
logger.warning(
"webhook_timestamp_verification_failed",
path=request.url.path
)
return JSONResponse(
status_code=status.HTTP_401_UNAUTHORIZED,
content={
"detail": "Webhook timestamp too old",
"error": "TIMESTAMP_TOO_OLD"
}
)
# Store raw body for handler
request.state.webhook_body = body
# Process request
return await call_next(request)
except Exception as e:
logger.error(
"webhook_verification_error",
error=str(e),
exc_info=True
)
return JSONResponse(
status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
content={
"detail": "Webhook verification error",
"error": "VERIFICATION_ERROR"
}
)
def _verify_signature(
self,
request: Request,
body: bytes,
secret: str
) -> bool:
"""Verify webhook signature."""
# Get signature header - support multiple formats
signature_header = (
request.headers.get("X-Cidadao-Signature") or
request.headers.get("X-Webhook-Signature") or
request.headers.get("X-Hub-Signature-256") # GitHub format
)
if not signature_header:
logger.debug("No signature header found")
return False
# Parse signature
if "=" in signature_header:
algorithm, signature = signature_header.split("=", 1)
else:
algorithm = "sha256"
signature = signature_header
# Calculate expected signature
if algorithm == "sha256":
expected = hmac.new(
secret.encode(),
body,
hashlib.sha256
).hexdigest()
elif algorithm == "sha1":
expected = hmac.new(
secret.encode(),
body,
hashlib.sha1
).hexdigest()
else:
logger.warning(f"Unsupported signature algorithm: {algorithm}")
return False
# Compare signatures
return hmac.compare_digest(signature, expected)
def _verify_timestamp(self, request: Request) -> bool:
"""Verify webhook timestamp is recent."""
timestamp_header = (
request.headers.get("X-Cidadao-Timestamp") or
request.headers.get("X-Webhook-Timestamp")
)
if not timestamp_header:
# No timestamp to verify
return True
try:
# Parse timestamp
if timestamp_header.isdigit():
# Unix timestamp
webhook_time = float(timestamp_header)
else:
# ISO format
from dateutil.parser import parse
webhook_time = parse(timestamp_header).timestamp()
# Check age
current_time = time.time()
age = abs(current_time - webhook_time)
return age <= self.max_timestamp_age
except Exception as e:
logger.error(f"Failed to parse timestamp: {e}")
return False
def create_webhook_signature(
payload: bytes,
secret: str,
algorithm: str = "sha256"
) -> str:
"""
Create webhook signature for outgoing webhooks.
Args:
payload: Request body
secret: Webhook secret
algorithm: Hash algorithm (sha256, sha1)
Returns:
Signature string with format "algorithm=signature"
"""
if algorithm == "sha256":
signature = hmac.new(
secret.encode(),
payload,
hashlib.sha256
).hexdigest()
elif algorithm == "sha1":
signature = hmac.new(
secret.encode(),
payload,
hashlib.sha1
).hexdigest()
else:
raise ValueError(f"Unsupported algorithm: {algorithm}")
return f"{algorithm}={signature}"
def verify_webhook_signature(
signature: str,
payload: bytes,
secret: str
) -> bool:
"""
Verify webhook signature.
Args:
signature: Signature header value
payload: Request body
secret: Webhook secret
Returns:
True if signature is valid
"""
try:
# Parse signature
if "=" in signature:
algorithm, sig = signature.split("=", 1)
else:
algorithm = "sha256"
sig = signature
# Generate expected signature
expected = create_webhook_signature(payload, secret, algorithm)
# Extract just the signature part
if "=" in expected:
_, expected_sig = expected.split("=", 1)
else:
expected_sig = expected
# Compare
return hmac.compare_digest(sig, expected_sig)
except Exception as e:
logger.error(f"Signature verification error: {e}")
return False
class WebhookSigner:
"""Helper class for signing webhook requests."""
def __init__(self, secret: str, algorithm: str = "sha256"):
"""Initialize webhook signer."""
self.secret = secret
self.algorithm = algorithm
def sign(self, payload: bytes) -> Dict[str, str]:
"""
Generate webhook headers with signature.
Args:
payload: Request body
Returns:
Dict of headers to include in request
"""
signature = create_webhook_signature(
payload,
self.secret,
self.algorithm
)
timestamp = str(int(time.time()))
return {
"X-Cidadao-Signature": signature,
"X-Cidadao-Timestamp": timestamp,
"X-Cidadao-Algorithm": self.algorithm
} |