swaf/src/components/CsrfProtectionComponent.ts

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import ApplicationComponent from "../ApplicationComponent";
import {Request, Router} from "express";
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import crypto from "crypto";
import {BadRequestError} from "../HttpError";
export default class CsrfProtectionComponent extends ApplicationComponent<void> {
private static readonly excluders: ((req: Request) => boolean)[] = [];
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public static addExcluder(excluder: (req: Request) => boolean) {
this.excluders.push(excluder);
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}
public async handle(router: Router): Promise<void> {
router.use(async (req, res, next) => {
for (const excluder of CsrfProtectionComponent.excluders) {
if (excluder(req)) return next();
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}
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if (!req.session) {
throw new Error('Session is unavailable.');
}
res.locals.getCSRFToken = () => {
if (typeof req.session!.csrf !== 'string') {
req.session!.csrf = crypto.randomBytes(64).toString('base64');
}
return req.session!.csrf;
};
if (!['GET', 'HEAD', 'OPTIONS'].find(s => s === req.method)) {
try {
if (!(await req.authGuard.isAuthenticatedViaRequest(req))) {
if (req.session.csrf === undefined) {
throw new InvalidCsrfTokenError(req.baseUrl, `You weren't assigned any CSRF token.`);
} else if (req.body.csrf === undefined) {
throw new InvalidCsrfTokenError(req.baseUrl, `You didn't provide any CSRF token.`);
} else if (req.session.csrf !== req.body.csrf) {
throw new InvalidCsrfTokenError(req.baseUrl, `Tokens don't match.`);
}
}
} catch (e) {
next(e);
return;
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}
}
next();
});
}
}
class InvalidCsrfTokenError extends BadRequestError {
constructor(url: string, details: string, cause?: Error) {
super(
`Invalid CSRF token`,
`${details} We can't process this request. Please try again.`,
url,
cause
);
}
get name(): string {
return 'Invalid CSRF Token';
}
get errorCode(): number {
return 401;
}
}