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feat: implement CSRF protection for OAuth flows with nonce validation (#20983)
* feat: implement CSRF protection for OAuth flows with nonce validation - Add NonceService for cryptographically secure nonce generation and validation - Include nonce in JWT state for OAuth authorization requests - Store nonce in secure httpOnly cookie with SameSite=strict - Validate nonce matches between state and cookie in auth callback - Add origin/referer header validation for additional CSRF protection - Use timing-safe comparison to prevent timing attacks - Clear nonce cookie after successful validation or on error This prevents CSRF attacks where malicious sites could initiate OAuth flows on behalf of users by ensuring authorization requests originate from Gitpod. Co-authored-by: Ona <[email protected]> * refactor: consolidate fragment protection and fix context provider conflict Co-authored-by: Ona <[email protected]> * fix: handle GitHub OAuth api subdomain edge case with secure redirect Co-authored-by: Ona <[email protected]> * fix: simplify api subdomain redirect test to avoid dependency injection complexity Replace complex Authenticator dependency injection test with simple unit test that focuses on the core logic without requiring all service dependencies. This makes the test more reliable and easier to maintain while still validating the critical api subdomain detection logic for the GitHub OAuth edge case. Co-authored-by: Ona <[email protected]> * docs: update domain examples to use gitpod.io instead of preview domains Update test examples and documentation to use production-appropriate domain examples (gitpod.io) instead of specific preview environment domains for better clarity and maintainability. Co-authored-by: Ona <[email protected]> * fix cookie Co-authored-by: Ona <[email protected]> * Update authenticator.ts Co-authored-by: Copilot <[email protected]> * Update authenticator.ts Co-authored-by: Copilot <[email protected]> * minor stuff * cleanup old redirect logic * cleanup * 1 Co-authored-by: Ona <[email protected]> * feat: add feature flags for nonce validation and strict authorize returnTo Add two feature flags to control security features with safe defaults: **Feature Flag 1: enable_nonce_validation (default: false)** - Controls CSRF nonce validation in OAuth flows - When disabled: Nonce is generated but not validated (future compatibility) - When enabled: Full CSRF protection with nonce and origin validation - Nonce cookies are always generated and cleared for consistency **Feature Flag 2: enable_strict_authorize_return_to (default: false)** - Controls returnTo validation strictness for /api/authorize endpoint - When disabled: Falls back to login validation (broader patterns) - When enabled: Uses strict authorize validation (limited to specific paths) - /api/login always uses login validation regardless of flag **Implementation Details:** - Always generate nonce for consistency and future compatibility - Only validate nonce when feature flag is enabled - Always clear nonce cookies regardless of validation state - Authorize endpoint checks flag and falls back gracefully - Comprehensive logging for debugging and monitoring **Backward Compatibility:** - Default false ensures no breaking changes - Gradual rollout possible via feature flag configuration - Existing authentication flows continue to work - Safe fallback behavior when flags are disabled Co-authored-by: Ona <[email protected]> * fix: validate OAuth callback origin against SCM provider domain Update NonceService.validateOrigin to check request origin against the expected SCM provider domain instead of Gitpod's own domain. This fixes the CSRF protection logic for OAuth callbacks which legitimately come from external providers (github.com, gitlab.com, etc.). 🤖 Generated with [Claude Code](https://claude.ai/code) Co-Authored-By: Claude <[email protected]> * 1 * remove the origin check logic * update sorry url * move files * use safeRedirect for redirect * 1 * [server] minor refactor/renames * moah changes --------- Co-authored-by: Ona <[email protected]> Co-authored-by: Copilot <[email protected]> Co-authored-by: Gero Posmyk-Leinemann <[email protected]> Co-authored-by: Claude <[email protected]>
1 parent 9b7dd9f commit a736c1b

19 files changed

+959
-115
lines changed

‎components/server/src/auth/api-subdomain-redirect.spec.ts

Lines changed: 82 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,82 @@
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/**
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* Copyright (c) 2024 Gitpod GmbH. All rights reserved.
3+
* Licensed under the GNU Affero General Public License (AGPL).
4+
* See License.AGPL.txt in the project root for license information.
5+
*/
6+
7+
import { expect } from "chai";
8+
9+
describe("API Subdomain Redirect Logic", () => {
10+
// Test the core logic without complex dependency injection
11+
function isApiSubdomainOfConfiguredHost(hostname: string, configuredHost: string): boolean {
12+
return hostname === `api.${configuredHost}`;
13+
}
14+
15+
describe("isApiSubdomainOfConfiguredHost", () => {
16+
it("should detect api subdomain of configured host", () => {
17+
const configuredHost = "gitpod.io";
18+
const testCases = [
19+
{ hostname: "api.gitpod.io", expected: true },
20+
{ hostname: "api.preview.gitpod-dev.com", expected: false }, // Different configured host
21+
{ hostname: "gitpod.io", expected: false }, // Main domain
22+
{ hostname: "workspace-123.gitpod.io", expected: false }, // Other subdomain
23+
{ hostname: "api.evil.com", expected: false }, // Different domain
24+
];
25+
26+
testCases.forEach(({ hostname, expected }) => {
27+
const result = isApiSubdomainOfConfiguredHost(hostname, configuredHost);
28+
expect(result).to.equal(expected, `Failed for hostname: ${hostname}`);
29+
});
30+
});
31+
32+
it("should handle GitHub OAuth edge case correctly", () => {
33+
// This is the specific case mentioned in the login completion handler
34+
const configuredHost = "gitpod.io";
35+
const apiSubdomain = `api.${configuredHost}`;
36+
37+
const result = isApiSubdomainOfConfiguredHost(apiSubdomain, configuredHost);
38+
expect(result).to.be.true;
39+
});
40+
41+
it("should handle preview environment correctly", () => {
42+
const configuredHost = "preview.gitpod-dev.com";
43+
const apiSubdomain = `api.${configuredHost}`;
44+
45+
const result = isApiSubdomainOfConfiguredHost(apiSubdomain, configuredHost);
46+
expect(result).to.be.true;
47+
});
48+
});
49+
50+
describe("OAuth callback flow scenarios", () => {
51+
it("should identify redirect scenarios correctly", () => {
52+
const scenarios = [
53+
{
54+
name: "GitHub OAuth Callback on API Subdomain",
55+
hostname: "api.gitpod.io",
56+
configuredHost: "gitpod.io",
57+
shouldRedirect: true,
58+
},
59+
{
60+
name: "Regular Login on Main Domain",
61+
hostname: "gitpod.io",
62+
configuredHost: "gitpod.io",
63+
shouldRedirect: false,
64+
},
65+
{
66+
name: "Workspace Port (Should Not Redirect)",
67+
hostname: "3000-gitpod.io",
68+
configuredHost: "gitpod.io",
69+
shouldRedirect: false,
70+
},
71+
];
72+
73+
scenarios.forEach((scenario) => {
74+
const result = isApiSubdomainOfConfiguredHost(scenario.hostname, scenario.configuredHost);
75+
expect(result).to.equal(
76+
scenario.shouldRedirect,
77+
`${scenario.name}: Expected ${scenario.shouldRedirect} for ${scenario.hostname}`,
78+
);
79+
});
80+
});
81+
});
82+
});

‎components/server/src/auth/auth-provider.ts

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Original file line numberDiff line numberDiff line change
@@ -97,6 +97,7 @@ export interface AuthFlow {
9797
readonly host: string;
9898
readonly returnTo: string;
9999
readonly overrideScopes?: boolean;
100+
readonly nonce?: string;
100101
}
101102
export namespace AuthFlow {
102103
export function is(obj: any): obj is AuthFlow {

‎components/server/src/auth/authenticator.ts

Lines changed: 109 additions & 21 deletions
Original file line numberDiff line numberDiff line change
@@ -18,6 +18,9 @@ import { UserService } from "../user/user-service";
1818
import { AuthFlow, AuthProvider } from "./auth-provider";
1919
import { HostContextProvider } from "./host-context-provider";
2020
import { SignInJWT } from "./jwt";
21+
import { NonceService } from "./nonce-service";
22+
import { getFeatureFlagEnableNonceValidation, getFeatureFlagEnableStrictAuthorizeReturnTo } from "../util/featureflags";
23+
import { validateLoginReturnToUrl, validateAuthorizeReturnToUrl, safeFragmentRedirect } from "../express-util";
2124

2225
@injectable()
2326
export class Authenticator {
@@ -30,6 +33,7 @@ export class Authenticator {
3033
@inject(TokenProvider) protected readonly tokenProvider: TokenProvider;
3134
@inject(UserAuthentication) protected readonly userAuthentication: UserAuthentication;
3235
@inject(SignInJWT) protected readonly signInJWT: SignInJWT;
36+
@inject(NonceService) protected readonly nonceService: NonceService;
3337

3438
@postConstruct()
3539
protected setup() {
@@ -77,6 +81,42 @@ export class Authenticator {
7781
if (!host) {
7882
throw new Error("Auth flow state is missing 'host' attribute.");
7983
}
84+
85+
// Handle GitHub OAuth edge case: redirect from api.* subdomain to base domain
86+
// This allows nonce validation to work since cookies are accessible on base domain
87+
if (this.isApiSubdomainOfConfiguredHost(req.hostname)) {
88+
log.info(`OAuth callback on api subdomain, redirecting to base domain for nonce validation`, {
89+
hostname: req.hostname,
90+
configuredHost: this.config.hostUrl.url.hostname,
91+
});
92+
const baseUrl = this.config.hostUrl.with({
93+
pathname: req.path,
94+
search: new URL(req.url, this.config.hostUrl.url).search,
95+
});
96+
safeFragmentRedirect(res, baseUrl.toString());
97+
return;
98+
}
99+
100+
// Validate nonce for CSRF protection (if feature flag is enabled)
101+
const isNonceValidationEnabled = await getFeatureFlagEnableNonceValidation();
102+
if (isNonceValidationEnabled) {
103+
const stateNonce = flowState.nonce;
104+
const cookieNonce = this.nonceService.getNonceFromCookie(req);
105+
106+
if (!this.nonceService.validateNonce(stateNonce, cookieNonce)) {
107+
log.error(`CSRF protection: Nonce validation failed`, {
108+
url: req.url,
109+
hasStateNonce: !!stateNonce,
110+
hasCookieNonce: !!cookieNonce,
111+
});
112+
res.status(403).send("Authentication failed");
113+
return;
114+
}
115+
}
116+
117+
// Always clear the nonce cookie
118+
this.nonceService.clearNonceCookie(res);
119+
80120
const hostContext = this.hostContextProvider.get(host);
81121
if (!hostContext) {
82122
throw new Error("No host context found.");
@@ -89,6 +129,8 @@ export class Authenticator {
89129
await hostContext.authProvider.callback(req, res, next);
90130
} catch (error) {
91131
log.error(`Failed to handle callback.`, error, { url: req.url });
132+
// Always clear nonce cookie on error
133+
this.nonceService.clearNonceCookie(res);
92134
}
93135
} else {
94136
// Otherwise proceed with other handlers
@@ -121,6 +163,15 @@ export class Authenticator {
121163
return state;
122164
}
123165

166+
/**
167+
* Checks if the current hostname is api.{configured-domain}.
168+
* This handles the GitHub OAuth edge case where callbacks may come to api.* subdomain.
169+
*/
170+
private isApiSubdomainOfConfiguredHost(hostname: string): boolean {
171+
const configuredHost = this.config.hostUrl.url.hostname;
172+
return hostname === `api.${configuredHost}`;
173+
}
174+
124175
protected async getAuthProviderForHost(host: string): Promise<AuthProvider | undefined> {
125176
const hostContext = this.hostContextProvider.get(host);
126177
return hostContext && hostContext.authProvider;
@@ -131,18 +182,26 @@ export class Authenticator {
131182
log.info(`User is already authenticated. Continue.`, { "login-flow": true });
132183
return next();
133184
}
134-
let returnTo: string | undefined = req.query.returnTo?.toString();
135-
if (returnTo) {
136-
log.info(`Stored returnTo URL: ${returnTo}`, { "login-flow": true });
185+
let returnToParam: string | undefined = req.query.returnTo?.toString();
186+
if (returnToParam) {
187+
log.info(`Stored returnTo URL: ${returnToParam}`, { "login-flow": true });
188+
// Validate returnTo URL against allowlist for login API
189+
if (!validateLoginReturnToUrl(returnToParam, this.config.hostUrl)) {
190+
log.warn(`Invalid returnTo URL rejected for login: ${returnToParam}`, { "login-flow": true });
191+
safeFragmentRedirect(res, this.getSorryUrl(`Invalid return URL.`));
192+
return;
193+
}
137194
}
138195
// returnTo defaults to workspaces url
139196
const workspaceUrl = this.config.hostUrl.asDashboard().toString();
140-
returnTo = returnTo || workspaceUrl;
197+
returnToParam = returnToParam || workspaceUrl;
198+
const returnTo = returnToParam;
199+
141200
const host: string = req.query.host?.toString() || "";
142201
const authProvider = host && (await this.getAuthProviderForHost(host));
143202
if (!host || !authProvider) {
144203
log.info(`Bad request: missing parameters.`, { "login-flow": true });
145-
res.redirect(this.getSorryUrl(`Bad request: missing parameters.`));
204+
safeFragmentRedirect(res, this.getSorryUrl(`Bad request: missing parameters.`));
146205
return;
147206
}
148207
// Logins with organizational Git Auth is not permitted
@@ -151,12 +210,12 @@ export class Authenticator {
151210
"authorize-flow": true,
152211
ap: authProvider.info,
153212
});
154-
res.redirect(this.getSorryUrl(`Login with "${host}" is not permitted.`));
213+
safeFragmentRedirect(res, this.getSorryUrl(`Login with "${host}" is not permitted.`));
155214
return;
156215
}
157216
if (this.config.disableDynamicAuthProviderLogin && !authProvider.params.builtin) {
158217
log.info(`Auth Provider is not allowed.`, { ap: authProvider.info });
159-
res.redirect(this.getSorryUrl(`Login with ${authProvider.params.host} is not allowed.`));
218+
safeFragmentRedirect(res, this.getSorryUrl(`Login with ${authProvider.params.host} is not allowed.`));
160219
return;
161220
}
162221

@@ -166,13 +225,18 @@ export class Authenticator {
166225
"login-flow": true,
167226
ap: authProvider.info,
168227
});
169-
res.redirect(this.getSorryUrl(`Login with "${host}" is not permitted.`));
228+
safeFragmentRedirect(res, this.getSorryUrl(`Login with "${host}" is not permitted.`));
170229
return;
171230
}
172231

232+
// Always generate nonce for CSRF protection (validation controlled by feature flag)
233+
const nonce = this.nonceService.generateNonce();
234+
this.nonceService.setNonceCookie(res, nonce);
235+
173236
const state = await this.signInJWT.sign({
174237
host,
175238
returnTo,
239+
nonce,
176240
});
177241

178242
// authenticate user
@@ -183,7 +247,7 @@ export class Authenticator {
183247
const user = req.user;
184248
if (!req.isAuthenticated() || !User.is(user)) {
185249
log.info(`User is not authenticated.`);
186-
res.redirect(this.getSorryUrl(`Not authenticated. Please login.`));
250+
safeFragmentRedirect(res, this.getSorryUrl(`Not authenticated. Please login.`));
187251
return;
188252
}
189253
const returnTo: string = req.query.returnTo?.toString() || this.config.hostUrl.asDashboard().toString();
@@ -193,20 +257,21 @@ export class Authenticator {
193257

194258
if (!host || !authProvider) {
195259
log.warn(`Bad request: missing parameters.`);
196-
res.redirect(this.getSorryUrl(`Bad request: missing parameters.`));
260+
safeFragmentRedirect(res, this.getSorryUrl(`Bad request: missing parameters.`));
197261
return;
198262
}
199263

200264
try {
201265
await this.userAuthentication.deauthorize(user, authProvider.authProviderId);
202-
res.redirect(returnTo);
266+
safeFragmentRedirect(res, returnTo);
203267
} catch (error) {
204268
next(error);
205269
log.error(`Failed to disconnect a provider.`, error, {
206270
host,
207271
userId: user.id,
208272
});
209-
res.redirect(
273+
safeFragmentRedirect(
274+
res,
210275
this.getSorryUrl(
211276
`Failed to disconnect a provider: ${error && error.message ? error.message : "unknown reason"}`,
212277
),
@@ -218,27 +283,45 @@ export class Authenticator {
218283
const user = req.user;
219284
if (!req.isAuthenticated() || !User.is(user)) {
220285
log.info(`User is not authenticated.`, { "authorize-flow": true });
221-
res.redirect(this.getSorryUrl(`Not authenticated. Please login.`));
286+
safeFragmentRedirect(res, this.getSorryUrl(`Not authenticated. Please login.`));
222287
return;
223288
}
224289
if (user.id === BUILTIN_INSTLLATION_ADMIN_USER_ID) {
225290
log.info(`Authorization is not permitted for admin user.`);
226-
res.redirect(
291+
safeFragmentRedirect(
292+
res,
227293
this.getSorryUrl(`Authorization is not permitted for admin user. Please login with a user account.`),
228294
);
229295
return;
230296
}
231-
const returnTo: string | undefined = req.query.returnTo?.toString();
297+
const returnToParam: string | undefined = req.query.returnTo?.toString();
232298
const host: string | undefined = req.query.host?.toString();
233299
const scopes: string = req.query.scopes?.toString() || "";
234300
const override = req.query.override === "true";
235301
const authProvider = host && (await this.getAuthProviderForHost(host));
236-
if (!returnTo || !host || !authProvider) {
302+
303+
if (!returnToParam || !host || !authProvider) {
237304
log.info(`Bad request: missing parameters.`, { "authorize-flow": true });
238-
res.redirect(this.getSorryUrl(`Bad request: missing parameters.`));
305+
safeFragmentRedirect(res, this.getSorryUrl(`Bad request: missing parameters.`));
239306
return;
240307
}
241308

309+
// Validate returnTo URL against allowlist for authorize API
310+
const isStrictAuthorizeValidationEnabled = await getFeatureFlagEnableStrictAuthorizeReturnTo();
311+
if (isStrictAuthorizeValidationEnabled) {
312+
const isValidReturnTo = validateAuthorizeReturnToUrl(returnToParam, this.config.hostUrl);
313+
if (!isValidReturnTo) {
314+
log.warn(`Invalid returnTo URL rejected for authorize`, {
315+
"authorize-flow": true,
316+
returnToParam,
317+
});
318+
safeFragmentRedirect(res, this.getSorryUrl(`Invalid return URL.`));
319+
return;
320+
}
321+
}
322+
323+
const returnTo = returnToParam;
324+
242325
// For non-verified org auth provider, ensure user is an owner of the org
243326
if (!authProvider.info.verified && authProvider.info.organizationId) {
244327
const member = await this.teamDb.findTeamMembership(user.id, authProvider.info.organizationId);
@@ -247,7 +330,7 @@ export class Authenticator {
247330
"authorize-flow": true,
248331
ap: authProvider.info,
249332
});
250-
res.redirect(this.getSorryUrl(`Authorization with "${host}" is not permitted.`));
333+
safeFragmentRedirect(res, this.getSorryUrl(`Authorization with "${host}" is not permitted.`));
251334
return;
252335
}
253336
}
@@ -258,7 +341,7 @@ export class Authenticator {
258341
"authorize-flow": true,
259342
ap: authProvider.info,
260343
});
261-
res.redirect(this.getSorryUrl(`Authorization with "${host}" is not permitted.`));
344+
safeFragmentRedirect(res, this.getSorryUrl(`Authorization with "${host}" is not permitted.`));
262345
return;
263346
}
264347

@@ -270,7 +353,7 @@ export class Authenticator {
270353
"authorize-flow": true,
271354
ap: authProvider.info,
272355
});
273-
res.redirect(this.getSorryUrl(`Authorization with "${host}" is not permitted.`));
356+
safeFragmentRedirect(res, this.getSorryUrl(`Authorization with "${host}" is not permitted.`));
274357
return;
275358
}
276359
}
@@ -297,7 +380,12 @@ export class Authenticator {
297380
}
298381
// authorize Gitpod
299382
log.info(`(doAuthorize) wanted scopes (${override ? "overriding" : "merging"}): ${wantedScopes.join(",")}`);
300-
const state = await this.signInJWT.sign({ host, returnTo, overrideScopes: override });
383+
384+
// Always generate nonce for CSRF protection (validation controlled by feature flag)
385+
const nonce = this.nonceService.generateNonce();
386+
this.nonceService.setNonceCookie(res, nonce);
387+
388+
const state = await this.signInJWT.sign({ host, returnTo, overrideScopes: override, nonce });
301389
authProvider.authorize(req, res, next, this.deriveAuthState(state), wantedScopes);
302390
}
303391
private mergeScopes(a: string[], b: string[]) {

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