RootShell: rewrite

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

2 files changed, 53 insertions, 41 deletions

diff --git a/app/src/main/java/com/wireguard/android/backends/RootShell.java b/app/src/main/java/com/wireguard/android/backends/RootShell.java
index 31b10f98..44b9dd8c 100644
--- a/app/src/main/java/com/wireguard/android/backends/RootShell.java
+++ b/app/src/main/java/com/wireguard/android/backends/RootShell.java
@@ -1,13 +1,14 @@
 package com.wireguard.android.backends;
 
 import android.content.Context;
+import android.system.OsConstants;
 import android.util.Log;
 
 import java.io.BufferedReader;
+import java.io.File;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
-import java.io.OutputStream;
 import java.nio.charset.StandardCharsets;
 import java.util.List;
 import java.util.regex.Pattern;
@@ -22,67 +23,76 @@ class RootShell {
      * Setup commands that are run at the beginning of each root shell. The trap command ensures
      * access to the return value of the last command, since su itself always exits with 0.
      */
-    private static final String SETUP_TEMPLATE = "export PATH=\"%s/bin:$PATH\"; export TMPDIR=\"%s/temp\"; trap 'echo $?' EXIT; mkdir -p \"%s/bin\" \"%s/temp\"; ln -fs \"%s/libwg.so\" \"%s/bin/wg\" || exit 99; ln -fs \"%s/libwg-quick.so\" \"%s/bin/wg-quick\" || exit 99;";
-    private static final String TAG = "RootShell";
+    private static final String TAG = "WireGuard/RootShell";
     private static final Pattern ERRNO_EXTRACTOR = Pattern.compile("error=(\\d+)");
 
-    private final byte[] setupCommands;
-    private final String shell;
+    private static final String[][] libraryNamedExecutables = {
+        { "libwg.so", "wg" },
+        { "libwg-quick.so", "wg-quick" }
+    };
+
+    private final String preamble;
 
     RootShell(final Context context) {
-        this(context, "su");
-    }
+        final String binDir = context.getCacheDir().getPath() + "/bin";
+        final String tmpDir = context.getCacheDir().getPath() + "/tmp";
+
+        new File(binDir).mkdirs();
+        new File(tmpDir).mkdirs();
+
+        preamble = String.format("export PATH=\"%s:$PATH\" TMPDIR=\"%s\";", binDir, tmpDir);
 
-    RootShell(final Context context, final String shell) {
-        final String tmpdir = context.getCacheDir().getPath();
-        final String fakelibdir = context.getApplicationInfo().nativeLibraryDir;
-        setupCommands = String.format(SETUP_TEMPLATE, tmpdir, tmpdir, tmpdir, tmpdir, fakelibdir, tmpdir, fakelibdir, tmpdir).getBytes(StandardCharsets.UTF_8);
-        this.shell = shell;
+        final String libDir = context.getApplicationInfo().nativeLibraryDir;
+        String symlinkCommand = "set -ex;";
+        for (final String[] libraryNamedExecutable : libraryNamedExecutables) {
+            final String args = "'" + libDir + "/" + libraryNamedExecutable[0] + "' '" + binDir + "/" + libraryNamedExecutable[1] + "'";
+            symlinkCommand += "ln -f " + args + " || ln -sf " + args + ";";
+        }
+        if (run(null, symlinkCommand) != 0)
+            Log.e(TAG, "Unable to establish symlinks for important executables.");
     }
 
     /**
-     * Run a series of commands in a root shell. These commands are all sent to the same shell
-     * process, so they can be considered a shell script.
+     * Run a command in a root shell.
      *
-     * @param output   Lines read from stdout and stderr are appended to this list. Pass null if the
+     * @param output   Lines read from stdout are appended to this list. Pass null if the
      *                 output from the shell is not important.
-     * @param commands One or more commands to run as root (each element is a separate line).
+     * @param command  Command to run as root.
      * @return The exit value of the last command run, or -1 if there was an internal error.
      */
-    int run(final List<String> output, final String... commands) {
-        if (commands.length < 1)
-            throw new IndexOutOfBoundsException("At least one command must be supplied");
+    int run(final List<String> output, final String command) {
         int exitValue = -1;
         try {
-            final ProcessBuilder builder = new ProcessBuilder().redirectErrorStream(true);
-            final Process process = builder.command(shell).start();
-            final OutputStream stdin = process.getOutputStream();
-            stdin.write(setupCommands);
-            for (final String command : commands)
-                stdin.write(command.concat("\n").getBytes(StandardCharsets.UTF_8));
-            stdin.close();
-            Log.d(TAG, "Sent " + commands.length + " command(s), now reading output");
+            final ProcessBuilder builder = new ProcessBuilder();
+            builder.environment().put("LANG", "C");
+            builder.command("su", "-c", preamble + command);
+            final Process process = builder.start();
+            Log.d(TAG, "Running: " + command);
             final InputStream stdout = process.getInputStream();
+            final InputStream stderr = process.getErrorStream();
             final BufferedReader stdoutReader =
                     new BufferedReader(new InputStreamReader(stdout, StandardCharsets.UTF_8));
+            final BufferedReader stderrReader =
+                    new BufferedReader(new InputStreamReader(stderr, StandardCharsets.UTF_8));
             String line;
-            String lastLine = null;
             while ((line = stdoutReader.readLine()) != null) {
-                Log.v(TAG, line);
-                lastLine = line;
                 if (output != null)
                     output.add(line);
+                Log.v(TAG, "stdout: " + line);
             }
-            process.waitFor();
-            process.destroy();
-            if (lastLine != null) {
-                // Remove the exit value line from the output
-                if (output != null)
-                    output.remove(output.size() - 1);
-                exitValue = Integer.parseInt(lastLine);
+            int linesOfStderr = 0;
+            String stderrLast = null;
+            while ((line = stderrReader.readLine()) != null) {
+                ++linesOfStderr;
+                stderrLast = line;
+                Log.v(TAG, "stderr: " + line);
             }
-            Log.d(TAG, "Session completed with exit value " + exitValue);
-        } catch (IOException | InterruptedException | NumberFormatException e) {
+            exitValue = process.waitFor();
+            process.destroy();
+            if (exitValue == 1 && linesOfStderr == 1 && stderrLast.equals("Permission denied"))
+                exitValue = OsConstants.EACCES;
+            Log.d(TAG, "Exit status: " + exitValue);
+        } catch (IOException | InterruptedException e) {
             Log.w(TAG, "Session failed with exception", e);
             final Matcher match = ERRNO_EXTRACTOR.matcher(e.toString());
             if (match.find())
diff --git a/app/src/main/java/com/wireguard/android/backends/VpnService.java b/app/src/main/java/com/wireguard/android/backends/VpnService.java
index 5e254d2e..ad16fb36 100644
--- a/app/src/main/java/com/wireguard/android/backends/VpnService.java
+++ b/app/src/main/java/com/wireguard/android/backends/VpnService.java
@@ -14,6 +14,8 @@ import android.os.IBinder;
 import android.preference.PreferenceManager;
 import android.provider.OpenableColumns;
 import android.service.quicksettings.TileService;
+import android.system.ErrnoException;
+import android.system.OsConstants;
 import android.util.Log;
 import android.widget.Toast;
 
@@ -48,7 +50,7 @@ public class VpnService extends Service
     public static final String KEY_ENABLED_CONFIGS = "enabled_configs";
     public static final String KEY_PRIMARY_CONFIG = "primary_config";
     public static final String KEY_RESTORE_ON_BOOT = "restore_on_boot";
-    private static final String TAG = "VpnService";
+    private static final String TAG = "WireGuard/VpnService";
 
     private static VpnService instance;
     private final IBinder binder = new Binder();
@@ -275,7 +277,7 @@ public class VpnService extends Service
             Log.i(TAG, "Running wg-quick up for " + config.getName());
             final File configFile = new File(getFilesDir(), config.getName() + ".conf");
             final int ret = rootShell.run(null, "wg-quick up '" + configFile.getPath() + "'");
-            if (ret == 13 /* EPERM */)
+            if (ret == OsConstants.EACCES)
                 return -0xfff0002;
             return ret;
         }