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feat(extension-auth): accept Firefox identity redirect hosts for extension auth #1999

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feat(extension-auth): accept Firefox identity redirect hosts for extension auth #1999

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6 changes: 6 additions & 0 deletions packages/env/server.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -80,6 +80,12 @@ function createServerEnv() {
.string()
.optional()
.describe("Chrome Web Store extension id allowed to receive auth keys"),
CAP_FIREFOX_EXTENSION_ID: z
.string()
.optional()
.describe(
"Firefox identity redirect subdomain (the <id> in https://<id>.extensions.allizom.org, derived from the gecko extension id) allowed to receive auth keys",
),
CAP_ALLOWED_SIGNUP_DOMAINS: z
.string()
.optional()
Expand Down
33 changes: 21 additions & 12 deletions packages/web-backend/src/Extension/Http.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,18 @@ import { handleDomainError } from "../Http/Errors.ts";
import { Videos } from "../Videos/index.ts";
import { Extensions } from "./Extensions.ts";

const CHROMIUM_IDENTITY_HOST_SUFFIX = ".chromiumapp.org";
// Each browser's identity.launchWebAuthFlow intercepts redirects to its own
// synthetic host; the leading label identifies the extension installation.
const IDENTITY_REDIRECT_HOSTS = [
{
suffix: ".chromiumapp.org",
getConfiguredExtensionId: () => serverEnv().CAP_CHROME_EXTENSION_ID,
},
{
suffix: ".extensions.allizom.org",
getConfiguredExtensionId: () => serverEnv().CAP_FIREFOX_EXTENSION_ID,
},
] as const;

const validateExtensionRedirectUri = (redirectUri: string) =>
Effect.gen(function* () {
Expand All @@ -29,18 +40,15 @@ const validateExtensionRedirectUri = (redirectUri: string) =>
catch: () => new HttpApiError.BadRequest(),
});

if (
url.protocol !== "https:" ||
!url.hostname.endsWith(CHROMIUM_IDENTITY_HOST_SUFFIX)
) {
const identityHost = IDENTITY_REDIRECT_HOSTS.find(({ suffix }) =>
url.hostname.endsWith(suffix),
);
if (url.protocol !== "https:" || !identityHost) {

@tembo tembo Bot Jul 11, 2026

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Might be worth rejecting non-default ports / credentials here to keep the redirect URI shape tight (and avoid surprises if browser behavior changes).

Suggested change
if (url.protocol !== "https:" || !identityHost) {
if (
url.protocol !== "https:" ||
url.port !== "" ||
url.username ||
url.password ||
!identityHost
) {
return yield* new HttpApiError.BadRequest();
}

return yield* new HttpApiError.BadRequest();
}

const extensionId = url.hostname.slice(
0,
-CHROMIUM_IDENTITY_HOST_SUFFIX.length,
);
const configuredExtensionId = serverEnv().CAP_CHROME_EXTENSION_ID;
const extensionId = url.hostname.slice(0, -identityHost.suffix.length);
const configuredExtensionId = identityHost.getConfiguredExtensionId();

@greptile-apps greptile-apps Bot Jul 11, 2026

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P2 Mixed-Case Firefox Id Rejection

URL.hostname is normalized to lowercase before extensionId is sliced, but the new Firefox id comes straight from CAP_FIREFOX_EXTENSION_ID. If that env var is copied with uppercase characters, the configured-id check rejects the real Firefox redirect host and the extension auth flow always returns a bad request.

Suggested change
const configuredExtensionId = identityHost.getConfiguredExtensionId();
const configuredExtensionId = identityHost
.getConfiguredExtensionId()
?.toLowerCase();
Prompt To Fix With AI 
This is a comment left during a code review.
Path: packages/web-backend/src/Extension/Http.ts
Line: 51

Comment:
**Mixed-Case Firefox Id Rejection**

`URL.hostname` is normalized to lowercase before `extensionId` is sliced, but the new Firefox id comes straight from `CAP_FIREFOX_EXTENSION_ID`. If that env var is copied with uppercase characters, the configured-id check rejects the real Firefox redirect host and the extension auth flow always returns a bad request.

```suggestion
		const configuredExtensionId = identityHost
			.getConfiguredExtensionId()
			?.toLowerCase();
```

How can I resolve this? If you propose a fix, please make it concise.

Comment on lines +50 to +51

@tembo tembo Bot Jul 11, 2026

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Since the comment says the leading label identifies the extension installation, it could be good to explicitly reject multi-label hosts (e.g. a.b.chromiumapp.org).

Suggested change
const extensionId = url.hostname.slice(0, -identityHost.suffix.length);
const configuredExtensionId = identityHost.getConfiguredExtensionId();
const extensionId = url.hostname.slice(0, -identityHost.suffix.length);
if (extensionId.includes(".")) {
return yield* new HttpApiError.BadRequest();
}
const configuredExtensionId = identityHost.getConfiguredExtensionId();


if (configuredExtensionId) {
if (extensionId !== configuredExtensionId) {
Expand All @@ -53,7 +61,8 @@ const validateExtensionRedirectUri = (redirectUri: string) =>
// signed-in user's auth key through this flow. The only deployment
// where accepting an arbitrary id is safe is localhost development;
// every reachable deployment (staging, previews, self-hosted) must set
// CAP_CHROME_EXTENSION_ID regardless of NODE_ENV.
// CAP_CHROME_EXTENSION_ID / CAP_FIREFOX_EXTENSION_ID regardless of
// NODE_ENV.
const webHostname = new URL(serverEnv().WEB_URL).hostname;
const isLocalDevelopment =
serverEnv().NODE_ENV !== "production" &&
Expand Down Expand Up @@ -151,7 +160,7 @@ const renderConsentPage = ({
</head>
<body>
<main class="card">
<h1>Connect the Cap Chrome extension</h1>
<h1>Connect the Cap browser extension</h1>
<p>The Cap extension is asking for access to your Cap account <span class="email">${escapeHtml(email)}</span> to create and upload recordings on your behalf.</p>
<p>Only continue if you opened this page from the Cap extension.</p>
<form method="post" action="approve" class="actions">
Expand Down
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