VpnService: Move it to a backends package

It should be split into two pieces: configuration file management
(loading/saving/renaming/deleting) and calling into wg-quick via
RootShell. The configuration file management part should then go
back into the main package. This is in preparation for adding
additional backends based on wg(8) and wireguard-go.

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

1 files changed, 86 insertions, 0 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
new file mode 100644
index 00000000..0b529065
--- /dev/null
+++ b/app/src/main/java/com/wireguard/android/backends/RootShell.java
@@ -0,0 +1,86 @@
+package com.wireguard.android.backends;
+
+import android.content.Context;
+import android.util.Log;
+
+import java.io.BufferedReader;
+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;
+
+/**
+ * Helper class for running commands as root.
+ */
+
+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 TMPDIR=%s\ntrap 'echo $?' EXIT\n";
+    private static final String TAG = "RootShell";
+
+    private final byte[] setupCommands;
+    private final String shell;
+
+    RootShell(final Context context) {
+        this(context, "su");
+    }
+
+    RootShell(final Context context, final String shell) {
+        final String tmpdir = context.getCacheDir().getPath();
+        setupCommands = String.format(SETUP_TEMPLATE, tmpdir).getBytes(StandardCharsets.UTF_8);
+        this.shell = shell;
+    }
+
+    /**
+     * 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.
+     *
+     * @param output   Lines read from stdout and stderr 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).
+     * @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 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 InputStream stdout = process.getInputStream();
+            final BufferedReader stdoutReader =
+                    new BufferedReader(new InputStreamReader(stdout, 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);
+            }
+            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);
+            }
+            Log.d(TAG, "Session completed with exit value " + exitValue);
+        } catch (IOException | InterruptedException | NumberFormatException e) {
+            Log.w(TAG, "Session failed with exception", e);
+        }
+        return exitValue;
+    }
+}