Prevent factory reset for short passwords in CryptKeeper

Since patterns and passwords can't be shorter than 4
elements, we shouldn't count them against attempts to unlock
the device.  If we do, we risk resetting the device
due to stray input.

Bug: 18211475
Bug: 18273380

Change-Id: Ib329cd3383471483cda68bfac4278b17d0c09c57

Conflicts:
	src/com/android/settings/CryptKeeper.java

src/com/android/settings/CryptKeeper.java

@@ -135,7 +135,18 @@ public class CryptKeeper extends Activity implements TextView.OnEditorActionList
     // how long we wait to clear a right pattern
     private static final int RIGHT_PATTERN_CLEAR_TIMEOUT_MS = 500;
 
-    private Runnable mClearPatternRunnable = new Runnable() {
+    // When the user enters a short pin/password, run this to show an error,
+    // but don't count it against attempts.
+    private final Runnable mFakeUnlockAttemptRunnable = new Runnable() {
+        public void run() {
+            handleBadAttempt(1 /* failedAttempt */);
+        }
+    };
+
+    // TODO: this should be tuned to match minimum decryption timeout
+    private static final int FAKE_ATTEMPT_DELAY = 1000;
+
+    private final Runnable mClearPatternRunnable = new Runnable() {
         @Override
         public void run() {
             mLockPatternView.clearPattern();
@@ -164,8 +175,7 @@ public class CryptKeeper extends Activity implements TextView.OnEditorActionList
         @Override
         protected void onPreExecute() {
             super.onPreExecute();
-            final TextView status = (TextView) findViewById(R.id.status);
-            status.setText(R.string.checking_decryption);
+            beginAttempt();
         }
 
         @Override
@@ -207,6 +217,17 @@ public class CryptKeeper extends Activity implements TextView.OnEditorActionList
                 showFactoryReset(true);
                 return;
             } else {
+                handleBadAttempt(failedAttempts);
+            }
+        }
+    }
+
+    private void beginAttempt() {
+        final TextView status = (TextView) findViewById(R.id.status);
+        status.setText(R.string.checking_decryption);
+    }
+
+    private void handleBadAttempt(Integer failedAttempts) {
         // Wrong entry. Handle pattern case.
         if (mLockPatternView != null) {
             mLockPatternView.setDisplayMode(DisplayMode.Wrong);
@@ -243,10 +264,11 @@ public class CryptKeeper extends Activity implements TextView.OnEditorActionList
                 }
             }
 
-
             if (mLockPatternView != null) {
                 mLockPatternView.setDisplayMode(DisplayMode.Wrong);
+                mLockPatternView.setEnabled(true);
             }
+
             // Reenable the password entry
             if (mPasswordEntry != null) {
                 mPasswordEntry.setEnabled(true);
@@ -255,11 +277,6 @@ public class CryptKeeper extends Activity implements TextView.OnEditorActionList
                 imm.showSoftInput(mPasswordEntry, 0);
                 setBackFunctionality(true);
             }
-                    if (mLockPatternView != null) {
-                        mLockPatternView.setEnabled(true);
-                    }
-                }
-            }
         }
     }
 
@@ -329,6 +346,8 @@ public class CryptKeeper extends Activity implements TextView.OnEditorActionList
             | StatusBarManager.DISABLE_SEARCH
             | StatusBarManager.DISABLE_RECENT;
 
+    protected static final int MIN_LENGTH_BEFORE_REPORT = LockPatternUtils.MIN_LOCK_PATTERN_SIZE;
+
     /** @return whether or not this Activity was started for debugging the UI only. */
     private boolean isDebugView() {
         return getIntent().hasExtra(EXTRA_FORCE_VIEW);
@@ -701,6 +720,11 @@ public class CryptKeeper extends Activity implements TextView.OnEditorActionList
         }
     }
 
+    private void fakeUnlockAttempt(View postingView) {
+        beginAttempt();
+        postingView.postDelayed(mFakeUnlockAttemptRunnable, FAKE_ATTEMPT_DELAY);
+    }
+
     protected LockPatternView.OnPatternListener mChooseNewLockPatternListener =
         new LockPatternView.OnPatternListener() {
 
@@ -716,7 +740,12 @@ public class CryptKeeper extends Activity implements TextView.OnEditorActionList
         @Override
         public void onPatternDetected(List<LockPatternView.Cell> pattern) {
             mLockPatternView.setEnabled(false);
+            if (pattern.size() >= MIN_LENGTH_BEFORE_REPORT) {
                 new DecryptTask().execute(LockPatternUtils.patternToString(pattern));
+            } else {
+                // Allow user to make as many of these as they want.
+                fakeUnlockAttempt(mLockPatternView);
+            }
         }
 
         @Override
@@ -873,7 +902,12 @@ public class CryptKeeper extends Activity implements TextView.OnEditorActionList
             mPasswordEntry.setEnabled(false);
             setBackFunctionality(false);
 
+            if (password.length() >= LockPatternUtils.MIN_LOCK_PATTERN_SIZE) {
                 new DecryptTask().execute(password);
+            } else {
+                // Allow user to make as many of these as they want.
+                fakeUnlockAttempt(mPasswordEntry);
+            }
 
             return true;
         }