From fa6d439a785593a47d4b236c20cd133efd3fbe8c Mon Sep 17 00:00:00 2001
From: Manjeet Rulhania <mrulhania@google.com>
Date: Mon, 20 Mar 2023 17:13:58 -0700
Subject: [PATCH] Add backup/reserved files in new permission subsystem

Bug: 274484493
Test: build
Change-Id: Ida3516c1730755a6bf3e636b8818726157c40831
---
 .../permission/access/AccessPersistence.kt    |  8 ++--
 .../access/util/AtomicFileExtensions.kt       | 43 +++++++++++++++++--
 2 files changed, 44 insertions(+), 7 deletions(-)

diff --git a/services/permission/java/com/android/server/permission/access/AccessPersistence.kt b/services/permission/java/com/android/server/permission/access/AccessPersistence.kt
index 5b1e4efe5acd9..4182ecf2666d7 100644
--- a/services/permission/java/com/android/server/permission/access/AccessPersistence.kt
+++ b/services/permission/java/com/android/server/permission/access/AccessPersistence.kt
@@ -30,9 +30,9 @@ import com.android.modules.utils.BinaryXmlSerializer
 import com.android.server.permission.access.collection.* // ktlint-disable no-wildcard-imports
 import com.android.server.permission.access.util.PermissionApex
 import com.android.server.permission.access.util.parseBinaryXml
-import com.android.server.permission.access.util.read
+import com.android.server.permission.access.util.readWithReserveCopy
 import com.android.server.permission.access.util.serializeBinaryXml
-import com.android.server.permission.access.util.writeInlined
+import com.android.server.permission.access.util.writeWithReserveCopy
 import java.io.File
 import java.io.FileNotFoundException
 
@@ -100,7 +100,7 @@ class AccessPersistence(
      */
     private inline fun File.parse(block: BinaryXmlPullParser.() -> Unit): Boolean =
         try {
-            AtomicFile(this).read { it.parseBinaryXml(block) }
+            AtomicFile(this).readWithReserveCopy { it.parseBinaryXml(block) }
             true
         } catch (e: FileNotFoundException) {
             Log.i(LOG_TAG, "$this not found")
@@ -179,7 +179,7 @@ class AccessPersistence(
 
     private inline fun File.serialize(block: BinaryXmlSerializer.() -> Unit) {
         try {
-            AtomicFile(this).writeInlined { it.serializeBinaryXml(block) }
+            AtomicFile(this).writeWithReserveCopy { it.serializeBinaryXml(block) }
         } catch (e: Exception) {
             Log.e(LOG_TAG, "Failed to serialize $this", e)
         }
diff --git a/services/permission/java/com/android/server/permission/access/util/AtomicFileExtensions.kt b/services/permission/java/com/android/server/permission/access/util/AtomicFileExtensions.kt
index 984dfb5a7548b..2c29332a638b1 100644
--- a/services/permission/java/com/android/server/permission/access/util/AtomicFileExtensions.kt
+++ b/services/permission/java/com/android/server/permission/access/util/AtomicFileExtensions.kt
@@ -16,17 +16,54 @@
 
 package com.android.server.permission.access.util
 
+import android.os.FileUtils
 import android.util.AtomicFile
+import android.util.Log
+import java.io.File
 import java.io.FileInputStream
+import java.io.FileNotFoundException
 import java.io.FileOutputStream
 import java.io.IOException
 
 /**
- * Read from an [AtomicFile] and close everything safely when done.
+ * Read from an [AtomicFile], fallback to reserve file to read the data.
+ */
+@Throws(Exception::class)
+inline fun AtomicFile.readWithReserveCopy(block: (FileInputStream) -> Unit) {
+    try {
+        openRead().use(block)
+    } catch (e: FileNotFoundException) {
+        throw e
+    } catch (e: Exception) {
+        Log.wtf("AccessPersistence", "Failed to read $this", e)
+        val reserveFile = File(baseFile.parentFile, baseFile.name + ".reservecopy")
+        try {
+            AtomicFile(reserveFile).openRead().use(block)
+        } catch (e2: Exception) {
+            Log.e("AccessPersistence", "Failed to read $reserveFile", e2)
+            throw e
+        }
+    }
+}
+
+/**
+ * Write to actual file and reserve file.
  */
 @Throws(IOException::class)
-inline fun AtomicFile.read(block: (FileInputStream) -> Unit) {
-    openRead().use(block)
+inline fun AtomicFile.writeWithReserveCopy(block: (FileOutputStream) -> Unit) {
+    val reserveFile = File(baseFile.parentFile, baseFile.name + ".reservecopy")
+    reserveFile.delete()
+    writeInlined(block)
+    try {
+        FileInputStream(baseFile).use { inputStream ->
+            FileOutputStream(reserveFile).use { outputStream ->
+                FileUtils.copy(inputStream, outputStream)
+                outputStream.fd.sync()
+            }
+        }
+    } catch (e: Exception) {
+        Log.e("AccessPersistence", "Failed to write $reserveFile", e)
+    }
 }
 
 /**