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fix(googlechat): validate sub claim for Chat issuer tokens to prevent auth bypass #3

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fix(googlechat): validate sub claim for Chat issuer tokens to prevent auth bypass #3

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17 changes: 7 additions & 10 deletions extensions/googlechat/src/auth.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -94,7 +94,7 @@ export async function verifyGoogleChatRequest(params: {
bearer?: string | null;
audienceType?: GoogleChatAudienceType | null;
audience?: string | null;
expectedAddOnPrincipal?: string | null;
expectedPrincipal?: string | null;
}): Promise<{ ok: boolean; reason?: string }> {
const bearer = params.bearer?.trim();
if (!bearer) {
Expand All @@ -119,23 +119,20 @@ export async function verifyGoogleChatRequest(params: {
if (!payload?.email_verified) {
return { ok: false, reason: "email not verified" };
}
if (email === CHAT_ISSUER) {
return { ok: true };
}
if (!ADDON_ISSUER_PATTERN.test(email)) {
if (email !== CHAT_ISSUER && !ADDON_ISSUER_PATTERN.test(email)) {
return { ok: false, reason: `invalid issuer: ${email}` };
}
const expectedAddOnPrincipal = params.expectedAddOnPrincipal?.trim().toLowerCase();
if (!expectedAddOnPrincipal) {
return { ok: false, reason: "missing add-on principal binding" };
const expectedPrincipal = params.expectedPrincipal?.trim().toLowerCase();
if (!expectedPrincipal) {
return { ok: false, reason: "missing principal binding (appPrincipal config required)" };
}
const tokenPrincipal = String(payload?.sub ?? "")
.trim()
.toLowerCase();
if (!tokenPrincipal || tokenPrincipal !== expectedAddOnPrincipal) {
if (!tokenPrincipal || tokenPrincipal !== expectedPrincipal) {
return {
ok: false,
reason: `unexpected add-on principal: ${tokenPrincipal || "<missing>"}`,
reason: `unexpected principal: ${tokenPrincipal || "<missing>"}`,
};
}
return { ok: true };
Expand Down
2 changes: 1 addition & 1 deletion extensions/googlechat/src/monitor-webhook.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -120,7 +120,7 @@ describe("googlechat monitor webhook", () => {
expect(verifyGoogleChatRequest).toHaveBeenCalledWith(
expect.objectContaining({
bearer: "addon-token",
expectedAddOnPrincipal: "chat-app",
expectedPrincipal: "chat-app",
}),
);
expect(processEvent).toHaveBeenCalledWith(
Expand Down
4 changes: 2 additions & 2 deletions extensions/googlechat/src/monitor-webhook.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -141,7 +141,7 @@ export function createGoogleChatWebhookRequestHandler(params: {
bearer: headerBearer,
audienceType: target.audienceType,
audience: target.audience,
expectedAddOnPrincipal: target.account.config.appPrincipal,
expectedPrincipal: target.account.config.appPrincipal,
});
return verification.ok;
},
Expand Down Expand Up @@ -176,7 +176,7 @@ export function createGoogleChatWebhookRequestHandler(params: {
bearer: parsed.addOnBearerToken,
audienceType: target.audienceType,
audience: target.audience,
expectedAddOnPrincipal: target.account.config.appPrincipal,
expectedPrincipal: target.account.config.appPrincipal,
});
return verification.ok;
},
Expand Down
53 changes: 48 additions & 5 deletions extensions/googlechat/src/targets.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -208,22 +208,65 @@ function mockTicket(payload: Record<string, unknown>) {
}

describe("verifyGoogleChatRequest", () => {
it("accepts Google Chat app-url tokens from the Chat issuer", async () => {
it("accepts Chat issuer tokens when principal matches", async () => {
mocks.verifyIdToken.mockReset();
mockTicket({
email: "chat@system.gserviceaccount.com",
email_verified: true,
sub: "12345",
});

await expect(
verifyGoogleChatRequest({
bearer: "token",
audienceType: "app-url",
audience: "https://example.com/googlechat",
expectedPrincipal: "12345",
}),
).resolves.toEqual({ ok: true });
});

it("rejects Chat issuer tokens when no principal binding is configured", async () => {
mocks.verifyIdToken.mockReset();
mockTicket({
email: "chat@system.gserviceaccount.com",
email_verified: true,
sub: "12345",
});

await expect(
verifyGoogleChatRequest({
bearer: "token",
audienceType: "app-url",
audience: "https://example.com/googlechat",
}),
).resolves.toEqual({
ok: false,
reason: "missing principal binding (appPrincipal config required)",
});
});

it("rejects Chat issuer tokens when principal does not match", async () => {
mocks.verifyIdToken.mockReset();
mockTicket({
email: "chat@system.gserviceaccount.com",
email_verified: true,
sub: "99999",
});

await expect(
verifyGoogleChatRequest({
bearer: "token",
audienceType: "app-url",
audience: "https://example.com/googlechat",
expectedPrincipal: "12345",
}),
).resolves.toEqual({
ok: false,
reason: "unexpected principal: 99999",
});
});

it("rejects add-on tokens when no principal binding is configured", async () => {
mocks.verifyIdToken.mockReset();
mockTicket({
Expand All @@ -240,7 +283,7 @@ describe("verifyGoogleChatRequest", () => {
}),
).resolves.toEqual({
ok: false,
reason: "missing add-on principal binding",
reason: "missing principal binding (appPrincipal config required)",
});
});

Expand All @@ -257,7 +300,7 @@ describe("verifyGoogleChatRequest", () => {
bearer: "token",
audienceType: "app-url",
audience: "https://example.com/googlechat",
expectedAddOnPrincipal: "principal-1",
expectedPrincipal: "principal-1",
}),
).resolves.toEqual({ ok: true });
});
Expand All @@ -275,11 +318,11 @@ describe("verifyGoogleChatRequest", () => {
bearer: "token",
audienceType: "app-url",
audience: "https://example.com/googlechat",
expectedAddOnPrincipal: "principal-1",
expectedPrincipal: "principal-1",
}),
).resolves.toEqual({
ok: false,
reason: "unexpected add-on principal: principal-2",
reason: "unexpected principal: principal-2",
});
});
});
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