fix: authentication bypass and denial of service (DoS) vulnerabilities in Apple Game Center auth adapter (GHSA-qf8x-vqjv-92gr) (parse-community#7962)

Author: mtrezza

spec/AuthenticationAdapters.spec.js

@@ -1665,11 +1665,7 @@ describe('Apple Game Center Auth adapter', () => {
       bundleId: 'cloud.xtralife.gamecenterauth',
     };
 
-    try {
-      await gcenter.validateAuthData(authData);
-    } catch (e) {
-      fail();
-    }
+    await gcenter.validateAuthData(authData);
   });
 
   it('validateAuthData invalid signature id', async () => {
@@ -1690,42 +1686,33 @@ describe('Apple Game Center Auth adapter', () => {
     }
   });
 
-  it('validateAuthData invalid public key url', async () => {
-    const authData = {
-      id: 'G:1965586982',
-      publicKeyUrl: 'invalid.com',
-      timestamp: 1565257031287,
-      signature: '1234',
-      salt: 'DzqqrQ==',
-      bundleId: 'cloud.xtralife.gamecenterauth',
-    };
-
-    try {
-      await gcenter.validateAuthData(authData);
-      fail();
-    } catch (e) {
-      expect(e.message).toBe('Apple Game Center - invalid publicKeyUrl: invalid.com');
-    }
-  });
-
   it('validateAuthData invalid public key http url', async () => {
-    const authData = {
-      id: 'G:1965586982',
-      publicKeyUrl: 'http://static.gc.apple.com/public-key/gc-prod-4.cer',
-      timestamp: 1565257031287,
-      signature: '1234',
-      salt: 'DzqqrQ==',
-      bundleId: 'cloud.xtralife.gamecenterauth',
-    };
-
-    try {
-      await gcenter.validateAuthData(authData);
-      fail();
-    } catch (e) {
-      expect(e.message).toBe(
-        'Apple Game Center - invalid publicKeyUrl: http://static.gc.apple.com/public-key/gc-prod-4.cer'
-      );
-    }
+    const publicKeyUrls = [
+      'example.com',
+      'http://static.gc.apple.com/public-key/gc-prod-4.cer',
+      'https://developer.apple.com/assets/elements/badges/download-on-the-app-store.svg',
+      'https://example.com/ \\.apple.com/public_key.cer',
+      'https://example.com/ &.apple.com/public_key.cer',
+    ];
+    await Promise.all(
+      publicKeyUrls.map(publicKeyUrl =>
+        expectAsync(
+          gcenter.validateAuthData({
+            id: 'G:1965586982',
+            timestamp: 1565257031287,
+            publicKeyUrl,
+            signature: '1234',
+            salt: 'DzqqrQ==',
+            bundleId: 'com.example.com',
+          })
+        ).toBeRejectedWith(
+          new Parse.Error(
+            Parse.Error.SCRIPT_FAILED,
+            `Apple Game Center - invalid publicKeyUrl: ${publicKeyUrl}`
+          )
+        )
+      )
+    );
   });
 });
 

src/Adapters/Auth/gcenter.js

@@ -19,15 +19,8 @@ const cache = {}; // (publicKey -> cert) cache
 
 function verifyPublicKeyUrl(publicKeyUrl) {
   try {
-    const parsedUrl = new URL(publicKeyUrl);
-    if (parsedUrl.protocol !== 'https:') {
-      return false;
-    }
-    const hostnameParts = parsedUrl.hostname.split('.');
-    const length = hostnameParts.length;
-    const domainParts = hostnameParts.slice(length - 2, length);
-    const domain = domainParts.join('.');
-    return domain === 'apple.com';
+    const regex = /^https:\/\/(?:[-_A-Za-z0-9]+\.){0,}apple\.com\/.*\.cer$/;
+    return regex.test(publicKeyUrl);
   } catch (error) {
     return false;
   }
@@ -43,7 +36,7 @@ function convertX509CertToPEM(X509Cert) {
   return pemPreFix + certBody + pemPostFix;
 }
 
-function getAppleCertificate(publicKeyUrl) {
+async function getAppleCertificate(publicKeyUrl) {
   if (!verifyPublicKeyUrl(publicKeyUrl)) {
     throw new Parse.Error(
       Parse.Error.OBJECT_NOT_FOUND,
@@ -53,6 +46,25 @@ function getAppleCertificate(publicKeyUrl) {
   if (cache[publicKeyUrl]) {
     return cache[publicKeyUrl];
   }
+  const url = new URL(publicKeyUrl);
+  const headOptions = {
+    hostname: url.hostname,
+    path: url.pathname,
+    method: 'HEAD',
+  };
+  const headers = await new Promise((resolve, reject) =>
+    https.get(headOptions, res => resolve(res.headers)).on('error', reject)
+  );
+  if (
+    headers['content-type'] !== 'application/pkix-cert' ||
+    headers['content-length'] == null ||
+    headers['content-length'] > 10000
+  ) {
+    throw new Parse.Error(
+      Parse.Error.OBJECT_NOT_FOUND,
+      `Apple Game Center - invalid publicKeyUrl: ${publicKeyUrl}`
+    );
+  }
   return new Promise((resolve, reject) => {
     https
       .get(publicKeyUrl, res => {