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/*
* Copyright (C) 2012 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.android.dx;
import java.io.File;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.List;
/**
* Uses heuristics to guess the application's private data directory.
*/
class AppDataDirGuesser {
// Copied from UserHandle, indicates range of uids allocated for a user.
public static final int PER_USER_RANGE = 100000;
@SuppressWarnings("ReturnValueIgnored")
public File guess() {
try {
ClassLoader classLoader = guessSuitableClassLoader();
// Check that we have an instance of the PathClassLoader.
Class clazz = Class.forName("dalvik.system.PathClassLoader");
clazz.cast(classLoader);
// Use the toString() method to calculate the data directory.
String pathFromThisClassLoader = getPathFromThisClassLoader(classLoader, clazz);
File[] results = guessPath(pathFromThisClassLoader);
if (results.length > 0) {
return results[0];
}
} catch (ClassCastException ignored) {
} catch (ClassNotFoundException ignored) {
}
return null;
}
private ClassLoader guessSuitableClassLoader() {
return AppDataDirGuesser.class.getClassLoader();
}
private String getPathFromThisClassLoader(ClassLoader classLoader, Class pathClassLoaderClass) {
// Prior to ICS, we can simply read the "path" field of the
// PathClassLoader.
try {
Field pathField = pathClassLoaderClass.getDeclaredField("path");
pathField.setAccessible(true);
return (String) pathField.get(classLoader);
} catch (NoSuchFieldException ignored) {
} catch (IllegalAccessException ignored) {
} catch (ClassCastException ignored) {
}
// Parsing toString() method: yuck. But no other way to get the path.
String result = classLoader.toString();
return processClassLoaderString(result);
}
/**
* Given the result of a ClassLoader.toString() call, process the result so that guessPath
* can use it. There are currently two variants. For Android 4.3 and later, the string
* "DexPathList" should be recognized and the array of dex path elements is parsed. for
* earlier versions, the last nested array ('[' ... ']') is enclosing the string we are
* interested in.
*/
static String processClassLoaderString(String input) {
if (input.contains("DexPathList")) {
return processClassLoaderString43OrLater(input);
} else {
return processClassLoaderString42OrEarlier(input);
}
}
private static String processClassLoaderString42OrEarlier(String input) {
/* The toString output looks like this:
* dalvik.system.PathClassLoader[dexPath=path/to/apk,libraryPath=path/to/libs]
*/
int index = input.lastIndexOf('[');
input = (index == -1) ? input : input.substring(index + 1);
index = input.indexOf(']');
input = (index == -1) ? input : input.substring(0, index);
return input;
}
private static String processClassLoaderString43OrLater(String input) {
/* The toString output looks like this:
* dalvik.system.PathClassLoader[DexPathList[[zip file "/data/app/{NAME}", ...], nativeLibraryDirectories=[...]]]
*/
int start = input.indexOf("DexPathList") + "DexPathList".length();
if (input.length() > start + 4) { // [[ + ]]
String trimmed = input.substring(start);
int end = trimmed.indexOf(']');
if (trimmed.charAt(0) == '[' && trimmed.charAt(1) == '[' && end >= 0) {
trimmed = trimmed.substring(2, end);
// Comma-separated list, Arrays.toString output.
String split[] = trimmed.split(",");
// Clean up parts. Each path element is the type of the element plus the path in
// quotes.
for (int i = 0; i < split.length; i++) {
int quoteStart = split[i].indexOf('"');
int quoteEnd = split[i].lastIndexOf('"');
if (quoteStart > 0 && quoteStart < quoteEnd) {
split[i] = split[i].substring(quoteStart + 1, quoteEnd);
}
}
// Need to rejoin components.
StringBuilder sb = new StringBuilder();
for (String s : split) {
if (sb.length() > 0) {
sb.append(':');
}
sb.append(s);
}
return sb.toString();
}
}
// This is technically a parsing failure. Return the original string, maybe a later
// stage can still salvage this.
return input;
}
File[] guessPath(String input) {
List results = new ArrayList<>();
String apkPathRoot = "/data/app/";
for (String potential : splitPathList(input)) {
if (!potential.startsWith(apkPathRoot)) {
continue;
}
int end = potential.lastIndexOf(".apk");
if (end != potential.length() - 4) {
continue;
}
int endSlash = potential.lastIndexOf("/", end);
if (endSlash == apkPathRoot.length() - 1) {
// Apks cannot be directly under /data/app
continue;
}
int startSlash = potential.lastIndexOf("/", endSlash - 1);
if (startSlash == -1) {
continue;
}
// Look for the first dash after the package name
int dash = potential.indexOf("-", startSlash);
if (dash == -1) {
continue;
}
end = dash;
String packageName = potential.substring(startSlash + 1, end);
File dataDir = getWriteableDirectory("/data/data/" + packageName);
if (dataDir == null) {
// If we can't access "/data/data", try to guess user specific data directory.
dataDir = guessUserDataDirectory(packageName);
}
if (dataDir != null) {
File cacheDir = new File(dataDir, "cache");
// The cache directory might not exist -- create if necessary
if (fileOrDirExists(cacheDir) || cacheDir.mkdir()) {
if (isWriteableDirectory(cacheDir)) {
results.add(cacheDir);
}
}
}
}
return results.toArray(new File[results.size()]);
}
static String[] splitPathList(String input) {
String trimmed = input;
if (input.startsWith("dexPath=")) {
int start = "dexPath=".length();
int end = input.indexOf(',');
trimmed = (end == -1) ? input.substring(start) : input.substring(start, end);
}
return trimmed.split(":");
}
boolean fileOrDirExists(File file) {
return file.exists();
}
boolean isWriteableDirectory(File file) {
return file.isDirectory() && file.canWrite();
}
Integer getProcessUid() {
/* Uses reflection to try to fetch process UID. It will only work when executing on
* Android device. Otherwise, returns null.
*/
try {
Method myUid = Class.forName("android.os.Process").getMethod("myUid");
// Invoke the method on a null instance, since it's a static method.
return (Integer) myUid.invoke(/* instance= */ null);
} catch (Exception e) {
// Catch any exceptions thrown and default to returning a null.
return null;
}
}
File guessUserDataDirectory(String packageName) {
Integer uid = getProcessUid();
if (uid == null) {
// If we couldn't retrieve process uid, return null.
return null;
}
// We're trying to get the ID of the Android user that's running the process. It can be
// inferred from the UID of the current process.
int userId = uid / PER_USER_RANGE;
return getWriteableDirectory(String.format("/data/user/%d/%s", userId, packageName));
}
private File getWriteableDirectory(String pathName) {
File dir = new File(pathName);
return isWriteableDirectory(dir) ? dir : null;
}
}
