Prevent authenticators from using Settings to launch arbitrary activities.

Various authenticator results such as getAuthToken and addAccount might
result in an Intent returned to the AccountManager caller. A malicious
authenticator could exploit the fact that the Settings are a system app,
lead the user to launch add account for their account type and thus get
Settings to use the intent to start some arbitrary third parties Activity.

The fix is to make sure that the UID of the app associated with Activity
to be launched by the supplied intent and the Authenticators UID share
the same signature.  This means that an authenticator implementer can only
exploit apps they control.

Bug: 7699048
Change-Id: I34330454c341e6a8422ca1ed3b390466a0feedce

1 files changed, 55 insertions, 1 deletions

diff --git a/services/java/com/android/server/accounts/AccountManagerService.java b/services/java/com/android/server/accounts/AccountManagerService.java
index 2145b76..3a3dfd5 100644
--- a/services/java/com/android/server/accounts/AccountManagerService.java
+++ b/services/java/com/android/server/accounts/AccountManagerService.java
@@ -47,6 +47,7 @@ import android.content.pm.PackageManager;
 import android.content.pm.PackageManager.NameNotFoundException;
 import android.content.pm.RegisteredServicesCache;
 import android.content.pm.RegisteredServicesCacheListener;
+import android.content.pm.ResolveInfo;
 import android.content.pm.UserInfo;
 import android.database.Cursor;
 import android.database.DatabaseUtils;
@@ -580,15 +581,18 @@ public class AccountManagerService
         try {
             new Session(fromAccounts, null, account.type, false,
                     false /* stripAuthTokenFromResult */) {
+                @Override
                 protected String toDebugString(long now) {
                     return super.toDebugString(now) + ", getAccountCredentialsForClone"
                             + ", " + account.type;
                 }
 
+                @Override
                 public void run() throws RemoteException {
                     mAuthenticator.getAccountCredentialsForCloning(this, account);
                 }
 
+                @Override
                 public void onResult(Bundle result) {
                     if (result != null) {
                         if (result.getBoolean(AccountManager.KEY_BOOLEAN_RESULT, false)) {
@@ -613,11 +617,13 @@ public class AccountManagerService
         try {
             new Session(targetUser, null, account.type, false,
                     false /* stripAuthTokenFromResult */) {
+                @Override
                 protected String toDebugString(long now) {
                     return super.toDebugString(now) + ", getAccountCredentialsForClone"
                             + ", " + account.type;
                 }
 
+                @Override
                 public void run() throws RemoteException {
                     // Confirm that the owner's account still exists before this step.
                     UserAccounts owner = getUserAccounts(UserHandle.USER_OWNER);
@@ -632,6 +638,7 @@ public class AccountManagerService
                     }
                 }
 
+                @Override
                 public void onResult(Bundle result) {
                     if (result != null) {
                         if (result.getBoolean(AccountManager.KEY_BOOLEAN_RESULT, false)) {
@@ -646,6 +653,7 @@ public class AccountManagerService
                     }
                 }
 
+                @Override
                 public void onError(int errorCode, String errorMessage) {
                     super.onError(errorCode,  errorMessage);
                     // TODO: Show error notification to user
@@ -774,6 +782,7 @@ public class AccountManagerService
             mAccount = account;
         }
 
+        @Override
         public void run() throws RemoteException {
             try {
                 mAuthenticator.hasFeatures(this, mAccount, mFeatures);
@@ -782,6 +791,7 @@ public class AccountManagerService
             }
         }
 
+        @Override
         public void onResult(Bundle result) {
             IAccountManagerResponse response = getResponseAndClose();
             if (response != null) {
@@ -807,6 +817,7 @@ public class AccountManagerService
             }
         }
 
+        @Override
         protected String toDebugString(long now) {
             return super.toDebugString(now) + ", hasFeatures"
                     + ", " + mAccount
@@ -863,15 +874,18 @@ public class AccountManagerService
             mAccount = account;
         }
 
+        @Override
         protected String toDebugString(long now) {
             return super.toDebugString(now) + ", removeAccount"
                     + ", account " + mAccount;
         }
 
+        @Override
         public void run() throws RemoteException {
             mAuthenticator.getAccountRemovalAllowed(this, mAccount);
         }
 
+        @Override
         public void onResult(Bundle result) {
             if (result != null && result.containsKey(AccountManager.KEY_BOOLEAN_RESULT)
                     && !result.containsKey(AccountManager.KEY_INTENT)) {
@@ -1212,16 +1226,19 @@ public class AccountManagerService
         try {
             new Session(accounts, response, accountType, false,
                     false /* stripAuthTokenFromResult */) {
+                @Override
                 protected String toDebugString(long now) {
                     return super.toDebugString(now) + ", getAuthTokenLabel"
                             + ", " + accountType
                             + ", authTokenType " + authTokenType;
                 }
 
+                @Override
                 public void run() throws RemoteException {
                     mAuthenticator.getAuthTokenLabel(this, authTokenType);
                 }
 
+                @Override
                 public void onResult(Bundle result) {
                     if (result != null) {
                         String label = result.getString(AccountManager.KEY_AUTH_TOKEN_LABEL);
@@ -1299,6 +1316,7 @@ public class AccountManagerService
 
             new Session(accounts, response, account.type, expectActivityLaunch,
                     false /* stripAuthTokenFromResult */) {
+                @Override
                 protected String toDebugString(long now) {
                     if (loginOptions != null) loginOptions.keySet();
                     return super.toDebugString(now) + ", getAuthToken"
@@ -1308,6 +1326,7 @@ public class AccountManagerService
                             + ", notifyOnAuthFailure " + notifyOnAuthFailure;
                 }
 
+                @Override
                 public void run() throws RemoteException {
                     // If the caller doesn't have permission then create and return the
                     // "grant permission" intent instead of the "getAuthToken" intent.
@@ -1318,6 +1337,7 @@ public class AccountManagerService
                     }
                 }
 
+                @Override
                 public void onResult(Bundle result) {
                     if (result != null) {
                         if (result.containsKey(AccountManager.KEY_AUTH_TOKEN_LABEL)) {
@@ -1482,11 +1502,13 @@ public class AccountManagerService
         try {
             new Session(accounts, response, accountType, expectActivityLaunch,
                     true /* stripAuthTokenFromResult */) {
+                @Override
                 public void run() throws RemoteException {
                     mAuthenticator.addAccount(this, mAccountType, authTokenType, requiredFeatures,
                             options);
                 }
 
+                @Override
                 protected String toDebugString(long now) {
                     return super.toDebugString(now) + ", addAccount"
                             + ", accountType " + accountType
@@ -1530,9 +1552,11 @@ public class AccountManagerService
         try {
             new Session(accounts, response, account.type, expectActivityLaunch,
                     true /* stripAuthTokenFromResult */) {
+                @Override
                 public void run() throws RemoteException {
                     mAuthenticator.confirmCredentials(this, account, options);
                 }
+                @Override
                 protected String toDebugString(long now) {
                     return super.toDebugString(now) + ", confirmCredentials"
                             + ", " + account;
@@ -1563,9 +1587,11 @@ public class AccountManagerService
         try {
             new Session(accounts, response, account.type, expectActivityLaunch,
                     true /* stripAuthTokenFromResult */) {
+                @Override
                 public void run() throws RemoteException {
                     mAuthenticator.updateCredentials(this, account, authTokenType, loginOptions);
                 }
+                @Override
                 protected String toDebugString(long now) {
                     if (loginOptions != null) loginOptions.keySet();
                     return super.toDebugString(now) + ", updateCredentials"
@@ -1596,9 +1622,11 @@ public class AccountManagerService
         try {
             new Session(accounts, response, accountType, expectActivityLaunch,
                     true /* stripAuthTokenFromResult */) {
+                @Override
                 public void run() throws RemoteException {
                     mAuthenticator.editProperties(this, mAccountType);
                 }
+                @Override
                 protected String toDebugString(long now) {
                     return super.toDebugString(now) + ", editProperties"
                             + ", accountType " + accountType;
@@ -1624,6 +1652,7 @@ public class AccountManagerService
             mFeatures = features;
         }
 
+        @Override
         public void run() throws RemoteException {
             synchronized (mAccounts.cacheLock) {
                 mAccountsOfType = getAccountsFromCacheLocked(mAccounts, mAccountType, mCallingUid,
@@ -1661,6 +1690,7 @@ public class AccountManagerService
             }
         }
 
+        @Override
         public void onResult(Bundle result) {
             mNumResults++;
             if (result == null) {
@@ -1699,6 +1729,7 @@ public class AccountManagerService
         }
 
 
+        @Override
         protected String toDebugString(long now) {
             return super.toDebugString(now) + ", getAccountsByTypeAndFeatures"
                     + ", " + (mFeatures != null ? TextUtils.join(",", mFeatures) : null);
@@ -2111,9 +2142,31 @@ public class AccountManagerService
             }
         }
 
+        @Override
         public void onResult(Bundle result) {
             mNumResults++;
-            if (result != null && !TextUtils.isEmpty(result.getString(AccountManager.KEY_AUTHTOKEN))) {
+            Intent intent = null;
+            if (result != null
+                    && (intent = result.getParcelable(AccountManager.KEY_INTENT)) != null) {
+                /*
+                 * The Authenticator API allows third party authenticators to
+                 * supply arbitrary intents to other apps that they can run,
+                 * this can be very bad when those apps are in the system like
+                 * the System Settings.
+                 */
+                PackageManager pm = mContext.getPackageManager();
+                ResolveInfo resolveInfo = pm.resolveActivity(intent, 0);
+                int targetUid = resolveInfo.activityInfo.applicationInfo.uid;
+                int authenticatorUid = Binder.getCallingUid();
+                if (PackageManager.SIGNATURE_MATCH !=
+                        pm.checkSignatures(authenticatorUid, targetUid)) {
+                    throw new SecurityException(
+                            "Activity to be started with KEY_INTENT must " +
+                            "share Authenticator's signatures");
+                }
+            }
+            if (result != null
+                    && !TextUtils.isEmpty(result.getString(AccountManager.KEY_AUTHTOKEN))) {
                 String accountName = result.getString(AccountManager.KEY_ACCOUNT_NAME);
                 String accountType = result.getString(AccountManager.KEY_ACCOUNT_TYPE);
                 if (!TextUtils.isEmpty(accountName) && !TextUtils.isEmpty(accountType)) {
@@ -2223,6 +2276,7 @@ public class AccountManagerService
             super(looper);
         }
 
+        @Override
         public void handleMessage(Message msg) {
             switch (msg.what) {
                 case MESSAGE_TIMED_OUT: