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fix(Headers): don't forward secure headers to 3th party (#1449)
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* fix(Headers): don't forward secure headers to 3th party
* added more narrow test for isDomainOrSubdomain
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jimmywarting authored Jan 14, 2022
1 parent f2c3d56 commit f5d3cf5
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13 changes: 13 additions & 0 deletions src/index.js
Original file line number Diff line number Diff line change
Expand Up @@ -21,6 +21,7 @@ import Request, {getNodeRequestOptions} from './request.js';
import {FetchError} from './errors/fetch-error.js';
import {AbortError} from './errors/abort-error.js';
import {isRedirect} from './utils/is-redirect.js';
import {isDomainOrSubdomain} from './utils/is.js';
import {parseReferrerPolicyFromHeader} from './utils/referrer.js';

export {Headers, Request, Response, FetchError, AbortError, isRedirect};
Expand Down Expand Up @@ -188,6 +189,18 @@ export default async function fetch(url, options_) {
referrerPolicy: request.referrerPolicy
};

// when forwarding sensitive headers like "Authorization",
// "WWW-Authenticate", and "Cookie" to untrusted targets,
// headers will be ignored when following a redirect to a domain
// that is not a subdomain match or exact match of the initial domain.
// For example, a redirect from "foo.com" to either "foo.com" or "sub.foo.com"
// will forward the sensitive headers, but a redirect to "bar.com" will not.
if (!isDomainOrSubdomain(request.url, locationURL)) {
for (const name of ['authorization', 'www-authenticate', 'cookie', 'cookie2']) {
requestOptions.headers.delete(name);
}
}

// HTTP-redirect fetch step 9
if (response_.statusCode !== 303 && request.body && options_.body instanceof Stream.Readable) {
reject(new FetchError('Cannot follow redirect with body being a readable stream', 'unsupported-redirect'));
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17 changes: 17 additions & 0 deletions src/utils/is.js
Original file line number Diff line number Diff line change
Expand Up @@ -56,3 +56,20 @@ export const isAbortSignal = object => {
)
);
};

/**
* isDomainOrSubdomain reports whether sub is a subdomain (or exact match) of
* the parent domain.
*
* Both domains must already be in canonical form.
* @param {string|URL} original
* @param {string|URL} destination
*/
export const isDomainOrSubdomain = (destination, original) => {
const orig = new URL(original).hostname;
const dest = new URL(destination).hostname;

return orig === dest || (
orig[orig.length - dest.length - 1] === '.' && orig.endsWith(dest)
);
};
61 changes: 61 additions & 0 deletions test/main.js
Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,7 @@ import ResponseOrig from '../src/response.js';
import Body, {getTotalBytes, extractContentType} from '../src/body.js';
import TestServer from './utils/server.js';
import chaiTimeout from './utils/chai-timeout.js';
import {isDomainOrSubdomain} from '../src/utils/is.js';

const AbortControllerPolyfill = abortControllerPolyfill.AbortController;
const encoder = new TextEncoder();
Expand Down Expand Up @@ -496,6 +497,66 @@ describe('node-fetch', () => {
});
});

it('should not forward secure headers to 3th party', async () => {
const res = await fetch(`${base}redirect-to/302/https://httpbin.org/get`, {
headers: new Headers({
cookie: 'gets=removed',
cookie2: 'gets=removed',
authorization: 'gets=removed',
'www-authenticate': 'gets=removed',
'other-safe-headers': 'stays',
'x-foo': 'bar'
})
});

const headers = new Headers((await res.json()).headers);
// Safe headers are not removed
expect(headers.get('other-safe-headers')).to.equal('stays');
expect(headers.get('x-foo')).to.equal('bar');
// Unsafe headers should not have been sent to httpbin
expect(headers.get('cookie')).to.equal(null);
expect(headers.get('cookie2')).to.equal(null);
expect(headers.get('www-authenticate')).to.equal(null);
expect(headers.get('authorization')).to.equal(null);
});

it('should forward secure headers to same host', async () => {
const res = await fetch(`${base}redirect-to/302/${base}inspect`, {
headers: new Headers({
cookie: 'is=cookie',
cookie2: 'is=cookie2',
authorization: 'is=authorization',
'other-safe-headers': 'stays',
'www-authenticate': 'is=www-authenticate',
'x-foo': 'bar'
})
});

const headers = new Headers((await res.json()).headers);
// Safe headers are not removed
expect(res.url).to.equal(`${base}inspect`);
expect(headers.get('other-safe-headers')).to.equal('stays');
expect(headers.get('x-foo')).to.equal('bar');
// Unsafe headers should not have been sent to httpbin
expect(headers.get('cookie')).to.equal('is=cookie');
expect(headers.get('cookie2')).to.equal('is=cookie2');
expect(headers.get('www-authenticate')).to.equal('is=www-authenticate');
expect(headers.get('authorization')).to.equal('is=authorization');
});

it('isDomainOrSubdomain', () => {
// Forwarding headers to same (sub)domain are OK
expect(isDomainOrSubdomain('http://a.com', 'http://a.com')).to.be.true;
expect(isDomainOrSubdomain('http://a.com', 'http://www.a.com')).to.be.true;
expect(isDomainOrSubdomain('http://a.com', 'http://foo.bar.a.com')).to.be.true;

// Forwarding headers to parent domain, another sibling or a totally other domain is not ok
expect(isDomainOrSubdomain('http://b.com', 'http://a.com')).to.be.false;
expect(isDomainOrSubdomain('http://www.a.com', 'http://a.com')).to.be.false;
expect(isDomainOrSubdomain('http://bob.uk.com', 'http://uk.com')).to.be.false;
expect(isDomainOrSubdomain('http://bob.uk.com', 'http://xyz.uk.com')).to.be.false;
});

it('should treat broken redirect as ordinary response (follow)', () => {
const url = `${base}redirect/no-location`;
return fetch(url).then(res => {
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6 changes: 6 additions & 0 deletions test/utils/server.js
Original file line number Diff line number Diff line change
Expand Up @@ -245,6 +245,12 @@ export default class TestServer {
res.end();
}

if (p.startsWith('/redirect-to/3')) {
res.statusCode = p.slice(13, 16);
res.setHeader('Location', p.slice(17));
res.end();
}

if (p === '/redirect/302') {
res.statusCode = 302;
res.setHeader('Location', '/inspect');
Expand Down

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