Checking Webhook Signatures
Validate the events that Stripe sends to your webhook URLs.
Stripe can optionally sign the webhook events it sends to your endpoints. We do so by including a signature in each event’s Stripe-Signature header. This allows you to validate that the events were sent by Stripe, not by a third party. You can verify signatures either using our official libraries, or manually using your own solution.
Before you can verify signatures, you need to retrieve your endpoint’s secret from your Dashboard’s Webhooks settings. Select an endpoint for which you want to obtain the secret, then select the Click to reveal button. Each secret is unique to the endpoint to which it corresponds. If you use multiple endpoints, you must obtain a secret for each one. After this setup, Stripe starts to sign each webhook it sends to the endpoint.
Verifying signatures using our official libraries
We recommend using one of our official libraries to verify signatures. You perform the verification by providing the event payload, the Stripe-Signature header, and the endpoint’s secret. If verification fails, Stripe returns an error.
# Set your secret key: remember to change this to your live secret key in production
# See your keys here: https://dashboard.stripe.com/account/apikeys
Stripe.api_key = "sk_test_BQokikJOvBiI2HlWgH4olfQ2"
# You can find your endpoint's secret in your webhook settings
endpoint_secret = 'whsec_...'
# Using Sinatra
post '/my/webhook/url' do
payload = request.body.read
sig_header = request.env['HTTP_STRIPE_SIGNATURE']
event = nil
begin
event = Stripe::Webhook.construct_event(
payload, sig_header, endpoint_secret
)
rescue JSON::ParserError => e
# Invalid payload
status 400
return
rescue Stripe::SignatureVerificationError => e
# Invalid signature
status 400
return
end
# Do something with event
status 200
end
# Set your secret key: remember to change this to your live secret key in production
# See your keys here: https://dashboard.stripe.com/account/apikeys
stripe.api_key = "sk_test_BQokikJOvBiI2HlWgH4olfQ2"
from django.http import HttpResponse
# You can find your endpoint's secret in your webhook settings
endpoint_secret = 'whsec_...'
# Using Django
@csrf_exempt
def my_webhook_view(request):
payload = request.body
sig_header = request.META['HTTP_STRIPE_SIGNATURE']
event = None
try:
event = stripe.Webhook.construct_event(
payload, sig_header, endpoint_secret
)
except ValueError as e:
# Invalid payload
return HttpResponse(status=400)
except stripe.error.SignatureVerificationError as e:
# Invalid signature
return HttpResponse(status=400)
# Do something with event
return HttpResponse(status=200)
// Set your secret key: remember to change this to your live secret key in production
// See your keys here: https://dashboard.stripe.com/account/apikeys
\Stripe\Stripe::setApiKey("sk_test_BQokikJOvBiI2HlWgH4olfQ2");
// You can find your endpoint's secret in your webhook settings
$endpoint_secret = 'whsec_...';
$payload = @file_get_contents('php://input');
$sig_header = $_SERVER['HTTP_STRIPE_SIGNATURE'];
$event = null;
try {
$event = \Stripe\Webhook::constructEvent(
$payload, $sig_header, $endpoint_secret
);
} catch(\UnexpectedValueException $e) {
// Invalid payload
http_response_code(400); // PHP 5.4 or greater
exit();
} catch(\Stripe\Error\SignatureVerification $e) {
// Invalid signature
http_response_code(400); // PHP 5.4 or greater
exit();
}
// Do something with $event
http_response_code(200); // PHP 5.4 or greater
// Set your secret key: remember to change this to your live secret key in production
// See your keys here: https://dashboard.stripe.com/account/apikeys
Stripe.apiKey = "sk_test_BQokikJOvBiI2HlWgH4olfQ2";
// Using the Spark framework (http://sparkjava.com)
public Object handle(Request request, Response response) {
String payload = request.body();
String sigHeader = request.headers("Stripe-Signature");
Event event = null;
try {
event = Webhook.constructEvent(
payload, sigHeader, endpointSecret
);
} catch (JsonSyntaxException e) {
// Invalid payload
response.status(400);
return "";
} catch (SignatureVerificationException e) {
// Invalid signature
response.status(400);
return "";
}
// Do something with event
response.status(200);
return "";
}
// Set your secret key: remember to change this to your live secret key in production
// See your keys here: https://dashboard.stripe.com/account/apikeys
var stripe = require("stripe")("sk_test_BQokikJOvBiI2HlWgH4olfQ2");
// You can find your endpoint's secret in your webhook settings
const endpointSecret = 'whsec_blSjcGhK1UHRbyGwXa9wSaK9FzLErNIS';
// This example uses Express to receive webhooks
const app = require('express')();
// Retrieve the raw body as a buffer and match all content types
app.use(require('body-parser').raw({type: '*/*'}));
app.post('/webhook/example', (req, res) => {
let sig = req.headers["stripe-signature"];
try {
let event = stripe.webhooks.constructEvent(req.body, sig, endpointSecret);
// Do something with event
}
catch (err) {
res.status(400).end()
}
// Return a response
res.json({received: true});
});
app.listen(8000, () => console.log('Running on port 8000'));
// Set your secret key: remember to change this to your live secret key in production
// See your keys here: https://dashboard.stripe.com/account/apikeys
StripeConfiguration.SetApiKey("sk_test_BQokikJOvBiI2HlWgH4olfQ2");
using System;
using System.IO;
using Microsoft.AspNetCore.Mvc;
using Stripe;
namespace workspace.Controllers {
[Route("api/[controller]")]
public class StripeWebHook : Controller {
// You can find your endpoint's secret in your webhook settings
const secret = "whsec_blSjcGhK1UHRbyGwXa9wSaK9FzLErNIS";
[HttpPost]
public void Index() {
var json = new StreamReader(HttpContext.Request.Body).ReadToEnd();
try {
var stripeEvent = StripeEventUtility.ConstructEvent(json,
Request.Headers["Stripe-Signature"], secret);
// Do something with event
}
catch (StripeException e) {
return BadRequest();
}
}
}
}
Preventing replay attacks
A replay attack is when an attacker intercepts a valid payload and its signature, then re-transmits them. To mitigate such attacks, Stripe includes a timestamp in the Stripe-Signature header. Because this timestamp is part of the signed payload, it is also verified by the signature, so an attacker cannot change the timestamp without invalidating the signature. If the signature is valid but the timestamp is too old, you can have your application reject the payload.
Our libraries have a default tolerance of five minutes between the timestamp and the current time. You can change this tolerance by providing an additional parameter when verifying signatures. We recommend that you use Network Time Protocol (NTP) to ensure that your server’s clock is accurate and synchronizes with the time on Stripe’s servers.
Stripe generates the timestamp and signature each time we send an event to your endpoint. If Stripe retries an event (e.g., your endpoint previously replied with a non-2xx status code), then we generate a new signature and timestamp for the new delivery attempt.
Verifying signatures manually
Although we recommend using our official libraries to verify webhook event signatures, you can use the following information to create a custom solution.
The Stripe-Signature header contains a timestamp and one or more signatures. The timestamp is prefixed by t=, and each signature is prefixed by a scheme. Schemes start with v, followed by an integer. Currently, the only valid signature scheme is v1. To aid with testing, Stripe sends an additional signature with a fake v0 scheme, for test-mode events.
Stripe-Signature: t=1492774577,
v1=5257a869e7ecebeda32affa62cdca3fa51cad7e77a0e56ff536d0ce8e108d8bd,
v0=6ffbb59b2300aae63f272406069a9788598b792a944a07aba816edb039989a39
Note that newlines have been added in the example above for clarity, but a real Stripe-Signature header will be all one line.
Stripe generates signatures using a hash-based message authentication code (HMAC) with SHA-256. To prevent downgrade attacks, you should ignore all schemes that are not v1.
It is possible to have multiple signatures with the same scheme/secret pair. This can happen when you roll an endpoint’s secret from the Dashboard, and choose to keep the previous secret active for up to 24 hours. During this time, your endpoint has multiple active secrets and Stripe generates one signature for each secret.
Step 1: Extract the timestamp and signatures from the header
Split the header, using the , character as the separator, to get a list of elements. Then split each element, using the = character as the separator, to get a prefix and value pair.
The value for the prefix t corresponds to the timestamp, and v1 corresponds to the signature(s). You can discard all other elements.
Step 2: Prepare the signed_payload string
You achieve this by concatenating:
- The timestamp (as a string)
- The character
. - The actual JSON payload (i.e., the request’s body)
Step 3: Determine the expected signature
Compute an HMAC with the SHA256 hash function. Use the endpoint’s signing secret as the key, and use the signed_payload string as the message.
Step 4: Compare signatures
Compare the signature(s) in the header to the expected signature. If a signature matches, compute the difference between the current timestamp and the received timestamp, then decide if the difference is within your tolerance.
To protect against timing attacks, use a constant-time string comparison to compare the expected signature to each of the received signatures.