philiprehberger-webhook-signature

HMAC-based webhook signature generation and verification with timing-safe comparison.

Installation

pip install philiprehberger-webhook-signature

Usage

Signing a Payload

from philiprehberger_webhook_signature import sign

signed = sign(payload='{"event": "order.created"}', secret="whsec_abc123")

print(signed.signature)   # HMAC hex digest
print(signed.timestamp)   # Unix timestamp
print(signed.to_header()) # "t=1234567890,sha256=abc..."

Verifying a Signature

from philiprehberger_webhook_signature import verify, parse_header

# Parse the signature header
header = request.headers["X-Webhook-Signature"]
signature, timestamp = parse_header(header)

# Verify (raises on failure)
verify(
    payload=request.body,
    secret="whsec_abc123",
    signature=signature,
    timestamp=timestamp,
    max_age=300.0,  # reject signatures older than 5 minutes
)

Key Rotation

Use verify_with_rotation for zero-downtime secret rotation. It tries the current secret first and falls back to the previous secret if verification fails:

from philiprehberger_webhook_signature import verify_with_rotation, parse_header

header = request.headers["X-Webhook-Signature"]
signature, timestamp = parse_header(header)

verify_with_rotation(
    payload=request.body,
    signature=signature,
    current_secret="whsec_new_secret",
    previous_secret="whsec_old_secret",  # optional fallback
    tolerance=300,
    timestamp=timestamp,
)

Error Handling

from philiprehberger_webhook_signature import (
    verify,
    SignatureError,
    SignatureExpiredError,
    SignatureMismatchError,
)

try:
    verify(payload, secret, signature, timestamp)
except SignatureExpiredError as e:
    print(f"Signature too old: {e.age}s > {e.max_age}s")
except SignatureMismatchError:
    print("Invalid signature")
except SignatureError as e:
    print(f"Verification failed: {e}")

Custom Algorithm

signed = sign(payload="data", secret="secret", algorithm="sha512")
verify(payload="data", secret="secret", signature=sig, timestamp=ts, algorithm="sha512")

Disable Expiry Check

verify(payload, secret, signature, timestamp, max_age=None)

API

Function / Class	Description
sign(payload, secret, algorithm, timestamp)	Generate an HMAC signature for a webhook payload
verify(payload, secret, signature, timestamp, algorithm, max_age)	Verify a webhook signature with timing-safe comparison
verify_with_rotation(payload, signature, current_secret, previous_secret, tolerance, algorithm, timestamp)	Verify with key rotation support (tries current then previous secret)
parse_header(header, prefix)	Parse a signature header string into (signature, timestamp) tuple
SignedPayload	Signed payload with signature, timestamp, body, and to_header()
SignatureError	Base exception for signature errors
SignatureExpiredError	Raised when signature age exceeds max_age
SignatureMismatchError	Raised when signature verification fails

Development

pip install -e .
python -m pytest tests/ -v

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License

MIT