前言

出廠的設備有些客戶喜歡設置鎖屏密碼，無奈記性不好，忘記密碼后就只能恢復出廠或者重新刷機了，啊這客戶肯定不接受的。

為了防止客戶逼逼賴賴，我們就未雨綢繆，給它加個清除接口。

先說結論，系統鎖屏密碼數據庫存儲位于 /data/system/locksettings.db

經過測試 O 版本直接刪除 locksettings.db 就已經達到要求

測試 Q、R 版本直接刪除 locksettings.db 后，系統鎖屏界面確實沒了，但一直卡在安卓正在啟動界面了，

無法進入桌面，進入設置中查看 Launcher3 應用丟了，目測此路不通。

那就曲線救國去研究 Settings 中是如何驗證密碼并取消密碼的。

Settings 中各版本存儲密碼傳遞對象，已圖案密碼為例 ConfirmLockPattern.java

O、P 版本 密碼 String intent.putExtra(ChooseLockSettingsHelper.EXTRA_KEY_PASSWORD, LockPatternUtils.patternToString(pattern));

Q 版本 密碼 Byte[] intent.putExtra(ChooseLockSettingsHelper.EXTRA_KEY_PASSWORD, LockPatternUtils.patternToByteArray(pattern));

R 版本 密碼 LockscreenCredential intent.putExtra(ChooseLockSettingsHelper.EXTRA_KEY_PASSWORD, pattern);

framework 往下加解密流程可參考這篇 AndroidQ 鎖屏密碼驗證流程之GateKeeper解析

解決思路

一：找到 Settings 中與用戶交互設置鎖屏密碼核心代碼，將繪制圖案或者密碼字符保存起來(數據庫、prop、ContentProvider等)

二：增加清除接口(AIDL、廣播、ContentResolver監聽等)

三：取出用戶設置密碼轉換為 framework 所需要 LockscreenCredential 對象

四：移除密碼

上代碼

4.1、找到鎖屏圖案保存核心代碼

vendor\mediatek\proprietary\packages\apps\MtkSettings\src\com\android\settings\password\ChooseLockPattern.java

protected LockPatternView.OnPatternListener mChooseNewLockPatternListener =new LockPatternView.OnPatternListener() {....public void onPatternDetected(List<LockPatternView.Cell> pattern) {if (mUiStage == Stage.NeedToConfirm || mUiStage == Stage.ConfirmWrong) {if (mChosenPattern == null) throw new IllegalStateException("null chosen pattern in stage 'need to confirm");try (LockscreenCredential confirmPattern =LockscreenCredential.createPattern(pattern)) {if (mChosenPattern.equals(confirmPattern)) {//20200903 cczheng add save lockdata startmScreenLockHelper.saveCurrentLockData(pattern);//20200903 cczheng add save lockdata endupdateStage(Stage.ChoiceConfirmed);} else {updateStage(Stage.ConfirmWrong);}}} else if (mUiStage == Stage.Introduction || mUiStage == Stage.ChoiceTooShort){if (pattern.size() < LockPatternUtils.MIN_LOCK_PATTERN_SIZE) {updateStage(Stage.ChoiceTooShort);} else {mChosenPattern = LockscreenCredential.createPattern(pattern);updateStage(Stage.FirstChoiceValid);}} else {throw new IllegalStateException("Unexpected stage " + mUiStage + " when "+ "entering the pattern.");}}

mChosenPattern 第一次繪制圖案密碼，confirmPattern 第二次繪制圖案密碼，兩次一致設置成功，

就地保存圖案密碼。圖案密碼九宮格每個點 Cell 對應一個 Row, 一個 Column,實際規則如下

(0,0) (0,1) (0,2)

(1,0) (1,1) (1,2)

(2,0) (2,1) (2,2)

最終畫線將每一個 cell 添加到集合中。

實際圖案密碼對象 LockscreenCredential.createPattern(pattern);

4.2、找到PIN碼和密碼保存核心代碼

vendor\mediatek\proprietary\packages\apps\MtkSettings\src\com\android\settings\password\ChooseLockPassword.java

public void handleNext() {if (mSaveAndFinishWorker != null) return;// TODO(b/120484642): This is a point of entry for passwords from the UIfinal Editable passwordText = mPasswordEntry.getText();if (TextUtils.isEmpty(passwordText)) {return;}mChosenPassword = mIsAlphaMode ? LockscreenCredential.createPassword(passwordText): LockscreenCredential.createPin(passwordText);if (mUiStage == Stage.Introduction) {if (validatePassword(mChosenPassword)) {mFirstPassword = mChosenPassword;mPasswordEntry.setText("");updateStage(Stage.NeedToConfirm);} else {mChosenPassword.zeroize();}} else if (mUiStage == Stage.NeedToConfirm) {if (mChosenPassword.equals(mFirstPassword)) {//20200903 cczheng add save lockdata startmScreenLockHelper.saveCurrentLockData(mIsAlphaMode, passwordText.toString());//20200903 cczheng add save lockdata endstartSaveAndFinish();} else {CharSequence tmp = mPasswordEntry.getText();if (tmp != null) {Selection.setSelection((Spannable) tmp, 0, tmp.length());}updateStage(Stage.ConfirmWrong);mChosenPassword.zeroize();}}}

mIsAlphaMode 用來區分是 PIN 碼還是密碼

實際密碼對象 LockscreenCredential.createPassword(passwordText)

實際PIN碼對象 LockscreenCredential.createPin(passwordText)

4.3、找到移除密碼核心代碼

設置完鎖屏密碼后再次進入鎖屏選擇頁面，此時需要驗證剛剛設置密碼，驗證成功后才能進入鎖屏選擇界面。

驗證成功就獲取到了 intent.putExtra(ChooseLockSettingsHelper.EXTRA_KEY_PASSWORD, pattern);

這個很關鍵，一會需要用它來移除鎖屏密碼

vendor\mediatek\proprietary\packages\apps\MtkSettings\src\com\android\settings\password\ChooseLockGeneric.java

void updateUnlockMethodAndFinish(int quality, boolean disabled, boolean chooseLockSkipped) {.....if (quality == DevicePolicyManager.PASSWORD_QUALITY_UNSPECIFIED) {// Clearing of user biometrics when screen lock is cleared is done at// LockSettingsService.removeBiometricsForUser().if (mUserPassword != null) {// No need to call setLockCredential if the user currently doesn't// have a passwordmChooseLockSettingsHelper.utils().setLockCredential(LockscreenCredential.createNone(), mUserPassword, mUserId);}mChooseLockSettingsHelper.utils().setLockScreenDisabled(disabled, mUserId);getActivity().setResult(Activity.RESULT_OK);finish();}}

關鍵方法就兩個

setLockCredential(新密碼，舊密碼，用戶id)

setLockScreenDisabled(移除密碼，用戶id)

4.4、造數據移除密碼

package com.android.settings.password;import android.content.Context; import android.util.Log; import android.os.SystemProperties; import com.android.internal.widget.LockPatternUtils; import com.android.internal.widget.LockPatternView; import com.android.internal.widget.LockPatternView.Cell; import com.android.internal.widget.LockscreenCredential;import java.util.ArrayList; import java.util.Collections; import java.util.List;public class ScreenLockHelper{private static final String TAG = "ScreenLockHelper";//value startwith //pt&xxxx LockPattern//pn&xxxx LockPin//ps&xxxx LockPasswordprivate final String KEY = "persist.android.screen.lock";private final String HEAD_PAT = "pt&";private final String HEAD_PIN = "pn&";private final String HEAD_PWD = "ps&";private Context mContext;private LockPatternUtils mLockPatternUtils;public ScreenLockHelper(Context context) {mContext = context;mLockPatternUtils = new LockPatternUtils(context);}public void saveCurrentLockData(boolean mIsPwd, String pwd) {pwd = (mIsPwd ? HEAD_PWD : HEAD_PIN) + pwd;SystemProperties.set(KEY, pwd);}public void saveCurrentLockData(List<LockPatternView.Cell> pattern) {String pwd = HEAD_PAT;StringBuilder builder = new StringBuilder();builder.append(pwd);for (int i=0; i<pattern.size(); i++) {LockPatternView.Cell cell = pattern.get(i);builder.append(cell.getRow());builder.append("*");builder.append(cell.getColumn());if (i != pattern.size() - 1) {builder.append("+");}Log.i(TAG,"cell="+cell.toString());}pwd = builder.toString();SystemProperties.set(KEY, pwd);}public void clearScreenLock() {LockscreenCredential emptyCredential = LockscreenCredential.createNone();LockscreenCredential savedCredential;String pwdValue = SystemProperties.get(KEY, "");if (pwdValue.startsWith(HEAD_PIN)) {savedCredential = LockscreenCredential.createPin(pwdValue.substring(3));}else if (pwdValue.startsWith(HEAD_PWD)) {savedCredential = LockscreenCredential.createPassword(pwdValue.substring(3));}else if (pwdValue.startsWith(HEAD_PAT)) {pwdValue = pwdValue.substring(3);List<LockPatternView.Cell> pattern = new ArrayList<LockPatternView.Cell>();String[] cellArray = pwdValue.split("\\+");for (String cellStr : cellArray) {String[] cell = cellStr.split("\\*");pattern.add(Cell.of(Integer.parseInt(cell[0]), Integer.parseInt(cell[1])));}savedCredential = LockscreenCredential.createPattern(pattern);}else{savedCredential = LockscreenCredential.createNone();}mLockPatternUtils.setLockCredential(emptyCredential, savedCredential, 0);mLockPatternUtils.setLockScreenDisabled(true, 0);} }

總結

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