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Webhooks.ts
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Webhooks.ts
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import {StripeError, StripeSignatureVerificationError} from './Error.js';
import {
CryptoProvider,
CryptoProviderOnlySupportsAsyncError,
} from './crypto/CryptoProvider.js';
import {PlatformFunctions} from './platform/PlatformFunctions.js';
type WebhookHeader = string | Uint8Array;
type WebhookParsedHeader = {
signatures: Array<string>;
timestamp: number;
};
type WebhookParsedEvent = {
details: WebhookParsedHeader;
decodedPayload: WebhookHeader;
decodedHeader: WebhookPayload;
suspectPayloadType: boolean;
};
type WebhookTestHeaderOptions = {
timestamp: number;
payload: string;
secret: string;
scheme: string;
signature: string;
cryptoProvider: CryptoProvider;
};
type WebhookEvent = Record<string, unknown>;
type WebhookPayload = string | Uint8Array;
type WebhookSignatureObject = {
verifyHeader: (
encodedPayload: WebhookPayload,
encodedHeader: WebhookHeader,
secret: string,
tolerance: number,
cryptoProvider: CryptoProvider,
receivedAt: number
) => boolean;
verifyHeaderAsync: (
encodedPayload: WebhookPayload,
encodedHeader: WebhookHeader,
secret: string,
tolerance: number,
cryptoProvider: CryptoProvider,
receivedAt: number
) => Promise<boolean>;
};
type WebhookObject = {
DEFAULT_TOLERANCE: number;
signature: WebhookSignatureObject;
constructEvent: (
payload: WebhookPayload,
header: WebhookHeader,
secret: string,
tolerance: null,
cryptoProvider: CryptoProvider,
receivedAt: number
) => WebhookEvent;
constructEventAsync: (
payload: WebhookPayload,
header: WebhookHeader,
secret: string,
tolerance: number,
cryptoProvider: CryptoProvider,
receivedAt: number
) => Promise<WebhookEvent>;
generateTestHeaderString: (opts: WebhookTestHeaderOptions) => string;
};
export function createWebhooks(
platformFunctions: PlatformFunctions
): WebhookObject {
const Webhook: WebhookObject = {
DEFAULT_TOLERANCE: 300, // 5 minutes
// @ts-ignore
signature: null,
constructEvent(
payload: WebhookPayload,
header: WebhookHeader,
secret: string,
tolerance: null,
cryptoProvider: CryptoProvider,
receivedAt: number
): WebhookEvent {
try {
this.signature.verifyHeader(
payload,
header,
secret,
tolerance || Webhook.DEFAULT_TOLERANCE,
cryptoProvider,
receivedAt
);
} catch (e) {
if (e instanceof CryptoProviderOnlySupportsAsyncError) {
e.message +=
'\nUse `await constructEventAsync(...)` instead of `constructEvent(...)`';
}
throw e;
}
const jsonPayload =
payload instanceof Uint8Array
? JSON.parse(new TextDecoder('utf8').decode(payload))
: JSON.parse(payload);
return jsonPayload;
},
async constructEventAsync(
payload: WebhookPayload,
header: WebhookHeader,
secret: string,
tolerance: number,
cryptoProvider: CryptoProvider,
receivedAt: number
): Promise<WebhookEvent> {
await this.signature.verifyHeaderAsync(
payload,
header,
secret,
tolerance || Webhook.DEFAULT_TOLERANCE,
cryptoProvider,
receivedAt
);
const jsonPayload =
payload instanceof Uint8Array
? JSON.parse(new TextDecoder('utf8').decode(payload))
: JSON.parse(payload);
return jsonPayload;
},
/**
* Generates a header to be used for webhook mocking
*
* @typedef {object} opts
* @property {number} timestamp - Timestamp of the header. Defaults to Date.now()
* @property {string} payload - JSON stringified payload object, containing the 'id' and 'object' parameters
* @property {string} secret - Stripe webhook secret 'whsec_...'
* @property {string} scheme - Version of API to hit. Defaults to 'v1'.
* @property {string} signature - Computed webhook signature
* @property {CryptoProvider} cryptoProvider - Crypto provider to use for computing the signature if none was provided. Defaults to NodeCryptoProvider.
*/
generateTestHeaderString: function(opts: WebhookTestHeaderOptions): string {
if (!opts) {
throw new StripeError({
message: 'Options are required',
});
}
opts.timestamp =
Math.floor(opts.timestamp) || Math.floor(Date.now() / 1000);
opts.scheme = opts.scheme || signature.EXPECTED_SCHEME;
opts.cryptoProvider = opts.cryptoProvider || getCryptoProvider();
opts.signature =
opts.signature ||
opts.cryptoProvider.computeHMACSignature(
opts.timestamp + '.' + opts.payload,
opts.secret
);
const generatedHeader = [
't=' + opts.timestamp,
opts.scheme + '=' + opts.signature,
].join(',');
return generatedHeader;
},
};
const signature = {
EXPECTED_SCHEME: 'v1',
verifyHeader(
encodedPayload: WebhookPayload,
encodedHeader: WebhookHeader,
secret: string,
tolerance: number,
cryptoProvider: CryptoProvider,
receivedAt: number
): boolean {
const {
decodedHeader: header,
decodedPayload: payload,
details,
suspectPayloadType,
} = parseEventDetails(
encodedPayload,
encodedHeader,
this.EXPECTED_SCHEME
);
const secretContainsWhitespace = /\s/.test(secret);
cryptoProvider = cryptoProvider || getCryptoProvider();
const expectedSignature = cryptoProvider.computeHMACSignature(
makeHMACContent(payload, details),
secret
);
validateComputedSignature(
payload,
header,
details,
expectedSignature,
tolerance,
suspectPayloadType,
secretContainsWhitespace,
receivedAt
);
return true;
},
async verifyHeaderAsync(
encodedPayload: WebhookPayload,
encodedHeader: WebhookHeader,
secret: string,
tolerance: number,
cryptoProvider: CryptoProvider,
receivedAt: number
): Promise<boolean> {
const {
decodedHeader: header,
decodedPayload: payload,
details,
suspectPayloadType,
} = parseEventDetails(
encodedPayload,
encodedHeader,
this.EXPECTED_SCHEME
);
const secretContainsWhitespace = /\s/.test(secret);
cryptoProvider = cryptoProvider || getCryptoProvider();
const expectedSignature = await cryptoProvider.computeHMACSignatureAsync(
makeHMACContent(payload, details),
secret
);
return validateComputedSignature(
payload,
header,
details,
expectedSignature,
tolerance,
suspectPayloadType,
secretContainsWhitespace,
receivedAt
);
},
};
function makeHMACContent(
payload: WebhookPayload,
details: WebhookParsedHeader
): string {
return `${details.timestamp}.${payload}`;
}
function parseEventDetails(
encodedPayload: WebhookPayload,
encodedHeader: WebhookHeader,
expectedScheme: string
): WebhookParsedEvent {
if (!encodedPayload) {
throw new StripeSignatureVerificationError(
encodedHeader,
encodedPayload,
{
message: 'No webhook payload was provided.',
}
);
}
const suspectPayloadType =
typeof encodedPayload != 'string' &&
!(encodedPayload instanceof Uint8Array);
const textDecoder = new TextDecoder('utf8');
const decodedPayload =
encodedPayload instanceof Uint8Array
? textDecoder.decode(encodedPayload)
: encodedPayload;
// Express's type for `Request#headers` is `string | []string`
// which is because the `set-cookie` header is an array,
// but no other headers are an array (docs: https://nodejs.org/api/http.html#http_message_headers)
// (Express's Request class is an extension of http.IncomingMessage, and doesn't appear to be relevantly modified: https://github.com/expressjs/express/blob/master/lib/request.js#L31)
if (Array.isArray(encodedHeader)) {
throw new Error(
'Unexpected: An array was passed as a header, which should not be possible for the stripe-signature header.'
);
}
if (encodedHeader == null || encodedHeader == '') {
throw new StripeSignatureVerificationError(
encodedHeader,
encodedPayload,
{
message: 'No stripe-signature header value was provided.',
}
);
}
const decodedHeader =
encodedHeader instanceof Uint8Array
? textDecoder.decode(encodedHeader)
: encodedHeader;
const details = parseHeader(decodedHeader, expectedScheme);
if (!details || details.timestamp === -1) {
throw new StripeSignatureVerificationError(
decodedHeader,
decodedPayload,
{
message: 'Unable to extract timestamp and signatures from header',
}
);
}
if (!details.signatures.length) {
throw new StripeSignatureVerificationError(
decodedHeader,
decodedPayload,
{
message: 'No signatures found with expected scheme',
}
);
}
return {
decodedPayload,
decodedHeader,
details,
suspectPayloadType,
};
}
function validateComputedSignature(
payload: WebhookPayload,
header: WebhookHeader,
details: WebhookParsedHeader,
expectedSignature: string,
tolerance: number,
suspectPayloadType: boolean,
secretContainsWhitespace: boolean,
receivedAt: number
): boolean {
const signatureFound = !!details.signatures.filter(
platformFunctions.secureCompare.bind(platformFunctions, expectedSignature)
).length;
const docsLocation =
'\nLearn more about webhook signing and explore webhook integration examples for various frameworks at ' +
'https://github.com/stripe/stripe-node#webhook-signing';
const whitespaceMessage = secretContainsWhitespace
? '\n\nNote: The provided signing secret contains whitespace. This often indicates an extra newline or space is in the value'
: '';
if (!signatureFound) {
if (suspectPayloadType) {
throw new StripeSignatureVerificationError(header, payload, {
message:
'Webhook payload must be provided as a string or a Buffer (https://nodejs.org/api/buffer.html) instance representing the _raw_ request body.' +
'Payload was provided as a parsed JavaScript object instead. \n' +
'Signature verification is impossible without access to the original signed material. \n' +
docsLocation +
'\n' +
whitespaceMessage,
});
}
throw new StripeSignatureVerificationError(header, payload, {
message:
'No signatures found matching the expected signature for payload.' +
' Are you passing the raw request body you received from Stripe? \n' +
docsLocation +
'\n' +
whitespaceMessage,
});
}
const timestampAge =
Math.floor(
(typeof receivedAt === 'number' ? receivedAt : Date.now()) / 1000
) - details.timestamp;
if (tolerance > 0 && timestampAge > tolerance) {
// @ts-ignore
throw new StripeSignatureVerificationError(header, payload, {
message: 'Timestamp outside the tolerance zone',
});
}
return true;
}
function parseHeader(
header: WebhookHeader,
scheme: string
): WebhookParsedHeader | null {
if (typeof header !== 'string') {
return null;
}
return header.split(',').reduce<WebhookParsedHeader>(
(accum, item) => {
const kv = item.split('=');
if (kv[0] === 't') {
accum.timestamp = parseInt(kv[1], 10);
}
if (kv[0] === scheme) {
accum.signatures.push(kv[1]);
}
return accum;
},
{
timestamp: -1,
signatures: [],
}
);
}
let webhooksCryptoProviderInstance: CryptoProvider | null = null;
/**
* Lazily instantiate a CryptoProvider instance. This is a stateless object
* so a singleton can be used here.
*/
function getCryptoProvider(): CryptoProvider {
if (!webhooksCryptoProviderInstance) {
webhooksCryptoProviderInstance = platformFunctions.createDefaultCryptoProvider();
}
return webhooksCryptoProviderInstance!;
}
Webhook.signature = signature;
return Webhook;
}