Require device encryption password to perform adb backup/restore

This supersedes any backup-password that the user might supply.  Per
design, the device encryption password is also always used to encrypt
the backup archive.

The CL introduces two new strings, used for prompting the user for
their device encryption password rather than their settings-defined
"backup password" when confirming a full backup or restore operation.

Bug 5382487

Change-Id: I0b03881b45437c944eaf636b6209278e1bba7a9f

1 files changed, 47 insertions, 0 deletions

diff --git a/services/java/com/android/server/MountService.java b/services/java/com/android/server/MountService.java
index 582f0ede6c63..5425813dedf2 100644
--- a/services/java/com/android/server/MountService.java
+++ b/services/java/com/android/server/MountService.java
@@ -1897,6 +1897,53 @@ class MountService extends IMountService.Stub
         }
     }
 
+    /**
+     * Validate a user-supplied password string with cryptfs
+     */
+    @Override
+    public int verifyEncryptionPassword(String password) throws RemoteException {
+        // Only the system process is permitted to validate passwords
+        if (Binder.getCallingUid() != android.os.Process.SYSTEM_UID) {
+            throw new SecurityException("no permission to access the crypt keeper");
+        }
+
+        mContext.enforceCallingOrSelfPermission(Manifest.permission.CRYPT_KEEPER,
+            "no permission to access the crypt keeper");
+
+        if (TextUtils.isEmpty(password)) {
+            throw new IllegalArgumentException("password cannot be empty");
+        }
+
+        waitForReady();
+
+        if (DEBUG_EVENTS) {
+            Slog.i(TAG, "validating encryption password...");
+        }
+
+        try {
+            ArrayList<String> response = mConnector.doCommand("cryptfs verifypw " + password);
+            String[] tokens = response.get(0).split(" ");
+
+            if (tokens == null || tokens.length != 2) {
+                String msg = "Unexpected result from cryptfs verifypw: {";
+                if (tokens == null) msg += "null";
+                else for (int i = 0; i < tokens.length; i++) {
+                    if (i != 0) msg += ',';
+                    msg += tokens[i];
+                }
+                msg += '}';
+                Slog.e(TAG, msg);
+                return -1;
+            }
+
+            Slog.i(TAG, "cryptfs verifypw => " + tokens[1]);
+            return Integer.parseInt(tokens[1]);
+        } catch (NativeDaemonConnectorException e) {
+            // Encryption failed
+            return e.getCode();
+        }
+    }
+
     public Parcelable[] getVolumeList() {
         synchronized(mVolumes) {
             int size = mVolumes.size();