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/*
* Copyright © 2018 Samuel Holland <samuel@sholland.org>
* Copyright © 2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
* SPDX-License-Identifier: Apache-2.0
*/
package com.wireguard.android.util;
import android.content.Context;
import android.support.annotation.Nullable;
import android.util.Log;
import com.wireguard.android.BuildConfig;
import com.wireguard.android.R;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.nio.charset.StandardCharsets;
import java.util.Collection;
import java.util.UUID;
/**
* Helper class for running commands as root.
*/
public class RootShell {
private static final String SU = "su";
private static final String TAG = "WireGuard/" + RootShell.class.getSimpleName();
private final String deviceNotRootedMessage;
private final File localBinaryDir;
private final File localTemporaryDir;
private final Object lock = new Object();
private final String preamble;
@Nullable private Process process;
@Nullable private BufferedReader stderr;
@Nullable private OutputStreamWriter stdin;
@Nullable private BufferedReader stdout;
public RootShell(final Context context) {
deviceNotRootedMessage = context.getString(R.string.error_root);
final File cacheDir = context.getCacheDir();
localBinaryDir = new File(cacheDir, "bin");
localTemporaryDir = new File(cacheDir, "tmp");
preamble = String.format("export CALLING_PACKAGE=%s PATH=\"%s:$PATH\" TMPDIR='%s'; id -u\n",
BuildConfig.APPLICATION_ID, localBinaryDir, localTemporaryDir);
}
private static boolean isExecutableInPath(final String name) {
final String path = System.getenv("PATH");
if (path == null)
return false;
for (final String dir : path.split(":"))
if (new File(dir, name).canExecute())
return true;
return false;
}
private boolean isRunning() {
synchronized (lock) {
try {
// Throws an exception if the process hasn't finished yet.
if (process != null)
process.exitValue();
return false;
} catch (final IllegalThreadStateException ignored) {
// The existing process is still running.
return true;
}
}
}
/**
* Run a command in a root shell.
*
* @param output Lines read from stdout are appended to this list. Pass null if the
* output from the shell is not important.
* @param command Command to run as root.
* @return The exit value of the command.
*/
public int run(@Nullable final Collection<String> output, final String command)
throws IOException, NoRootException {
synchronized (lock) {
/* Start inside synchronized block to prevent a concurrent call to stop(). */
start();
final String marker = UUID.randomUUID().toString();
final String script = "echo " + marker + "; echo " + marker + " >&2; (" + command +
"); ret=$?; echo " + marker + " $ret; echo " + marker + " $ret >&2\n";
Log.v(TAG, "executing: " + command);
stdin.write(script);
stdin.flush();
String line;
int errnoStdout = Integer.MIN_VALUE;
int errnoStderr = Integer.MAX_VALUE;
int markersSeen = 0;
while ((line = stdout.readLine()) != null) {
if (line.startsWith(marker)) {
++markersSeen;
if (line.length() > marker.length() + 1) {
errnoStdout = Integer.valueOf(line.substring(marker.length() + 1));
break;
}
} else if (markersSeen > 0) {
if (output != null)
output.add(line);
Log.v(TAG, "stdout: " + line);
}
}
while ((line = stderr.readLine()) != null) {
if (line.startsWith(marker)) {
++markersSeen;
if (line.length() > marker.length() + 1) {
errnoStderr = Integer.valueOf(line.substring(marker.length() + 1));
break;
}
} else if (markersSeen > 2) {
Log.v(TAG, "stderr: " + line);
}
}
if (markersSeen != 4)
throw new IOException("Expected 4 markers, received " + markersSeen);
if (errnoStdout != errnoStderr)
throw new IOException("Unable to read exit status");
Log.v(TAG, "exit: " + errnoStdout);
return errnoStdout;
}
}
public void start() throws IOException, NoRootException {
if (!isExecutableInPath(SU))
throw new NoRootException(deviceNotRootedMessage);
synchronized (lock) {
if (isRunning())
return;
if (!localBinaryDir.isDirectory() && !localBinaryDir.mkdirs())
throw new FileNotFoundException("Could not create local binary directory");
if (!localTemporaryDir.isDirectory() && !localTemporaryDir.mkdirs())
throw new FileNotFoundException("Could not create local temporary directory");
try {
final ProcessBuilder builder = new ProcessBuilder().command(SU);
builder.environment().put("LC_ALL", "C");
try {
process = builder.start();
} catch (final IOException e) {
// A failure at this stage means the device isn't rooted.
throw new NoRootException(deviceNotRootedMessage, e);
}
stdin = new OutputStreamWriter(process.getOutputStream(), StandardCharsets.UTF_8);
stdout = new BufferedReader(new InputStreamReader(process.getInputStream(),
StandardCharsets.UTF_8));
stderr = new BufferedReader(new InputStreamReader(process.getErrorStream(),
StandardCharsets.UTF_8));
stdin.write(preamble);
stdin.flush();
// Check that the shell started successfully.
final String uid = stdout.readLine();
if (!"0".equals(uid)) {
Log.w(TAG, "Root check did not return correct UID: " + uid);
throw new NoRootException(deviceNotRootedMessage);
}
if (!isRunning()) {
String line;
while ((line = stderr.readLine()) != null) {
Log.w(TAG, "Root check returned an error: " + line);
if (line.contains("Permission denied"))
throw new NoRootException(deviceNotRootedMessage);
}
throw new IOException("Shell failed to start: " + process.exitValue());
}
} catch (final IOException | NoRootException e) {
stop();
throw e;
}
}
}
public void stop() {
synchronized (lock) {
if (process != null) {
process.destroy();
process = null;
}
}
}
public static class NoRootException extends Exception {
public NoRootException(final String message, final Throwable cause) {
super(message, cause);
}
public NoRootException(final String message) {
super(message);
}
}
}
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