/* * Copyright © 2018 Samuel Holland * Copyright © 2018 Jason A. Donenfeld . 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.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=com.wireguard.android PATH=\"%s:$PATH\" TMPDIR='%s'; id -u\n", localBinaryDir, localTemporaryDir); } private static boolean isExecutableInPath(final String name) { final String path = System.getenv("PATH"); if (path == null) return false; for (final String dir : path.split(":")) if (new File(dir, name).canExecute()) return true; return false; } private boolean isRunning() { synchronized (lock) { try { // Throws an exception if the process hasn't finished yet. if (process != null) process.exitValue(); return false; } catch (final IllegalThreadStateException ignored) { // The existing process is still running. return true; } } } /** * Run a command in a root shell. * * @param output Lines read from stdout are appended to this list. Pass null if the * output from the shell is not important. * @param command Command to run as root. * @return The exit value of the command. */ public int run(@Nullable final Collection output, final String command) throws IOException, NoRootException { synchronized (lock) { /* Start inside synchronized block to prevent a concurrent call to stop(). */ start(); final String marker = UUID.randomUUID().toString(); final String script = "echo " + marker + "; echo " + marker + " >&2; (" + command + "); ret=$?; 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); } } }