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package com.wireguard.android.util;
import android.content.Context;
import android.system.ErrnoException;
import android.system.OsConstants;
import android.util.Log;
import com.wireguard.android.Application.ApplicationContext;
import com.wireguard.android.Application.ApplicationScope;
import java.io.BufferedWriter;
import java.io.BufferedReader;
import java.io.OutputStreamWriter;
import java.io.InputStreamReader;
import java.io.File;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.util.List;
import java.util.UUID;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import javax.inject.Inject;
/**
* Helper class for running commands as root.
*/
@ApplicationScope
public class RootShell {
private static final Pattern ERRNO_EXTRACTOR = Pattern.compile("error=(\\d+)");
/**
* 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 TAG = "WireGuard/" + RootShell.class.getSimpleName();
private static final String[][] libraryNamedExecutables = {
{"libwg.so", "wg"},
{"libwg-quick.so", "wg-quick"}
};
private final String preamble;
private BufferedWriter stdin;
private BufferedReader stdout;
private BufferedReader stderr;
private Process process;
@Inject
public RootShell(@ApplicationContext final Context context) {
final String binDir = context.getCacheDir().getPath() + "/bin";
final String tmpDir = context.getCacheDir().getPath() + "/tmp";
final String libDir = context.getApplicationInfo().nativeLibraryDir;
new File(binDir).mkdirs();
new File(tmpDir).mkdirs();
StringBuilder builder = new StringBuilder();
for (final String[] libraryNamedExecutable : libraryNamedExecutables) {
final String arg1 = "'" + libDir + "/" + libraryNamedExecutable[0] + "'";
final String arg2 = "'" + binDir + "/" + libraryNamedExecutable[1] + "'";
builder.append(String.format("[ %s -ef %s ] || ln -sf %s %s || exit 31;", arg1, arg2, arg1, arg2));
}
builder.append(String.format("export PATH=\"%s:$PATH\" TMPDIR=\"%s\";", binDir, tmpDir));
builder.append("id;\n");
preamble = builder.toString();
}
private static boolean isExecutable(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 void ensureRoot() throws Exception {
try {
if (process != null) {
process.exitValue();
process = null;
}
} catch (IllegalThreadStateException e) {
return;
}
if (!isExecutable("su"))
throw new NoRootException();
try {
final ProcessBuilder builder = new ProcessBuilder();
builder.environment().put("LANG", "C");
builder.command("su");
process = builder.start();
stdin = new BufferedWriter(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));
Log.d(TAG, "New root shell, sending preamble: " + preamble);
stdin.write(preamble);
stdin.flush();
final String id = stdout.readLine();
try {
int errno = process.exitValue();
String line;
while ((line = stderr.readLine()) != null) {
if (line.contains("Permission denied"))
throw new NoRootException();
}
throw new ErrnoException("Unknown error when obtaining root access", errno);
} catch (IllegalThreadStateException e) {
// We're alive, so keep executing.
}
if (id == null || !id.contains("uid=0"))
throw new NoRootException();
} catch (Exception e) {
Log.w(TAG, "Session failed with exception", e);
process.destroy();
process = null;
final Matcher match = ERRNO_EXTRACTOR.matcher(e.toString());
if (match.find()) {
final int errno = Integer.valueOf(match.group(1));
if (errno == OsConstants.EACCES)
throw new NoRootException();
else
throw new ErrnoException("Unknown error when obtaining root access", errno);
}
throw e;
}
}
/**
* 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 last command run, or -1 if there was an internal error.
*/
public int run(final List<String> output, final String command) throws Exception {
ensureRoot();
StringBuilder builder = new StringBuilder();
final String marker = UUID.randomUUID().toString();
final String begin = marker + " begin";
final String end = marker + " end";
builder.append(String.format("echo '%s';", begin));
builder.append(String.format("echo '%s' >&2;", begin));
builder.append('(');
builder.append(command);
builder.append(");");
builder.append("ret=$?;");
builder.append(String.format("echo '%s' $ret;", end));
builder.append(String.format("echo '%s' $ret >&2;", end));
builder.append('\n');
Log.v(TAG, "executing: " + command);
stdin.write(builder.toString());
stdin.flush();
String line;
boolean first = true;
int errnoStdout = -1, errnoStderr = -2;
int beginEnds = 0;
while ((line = stdout.readLine()) != null) {
if (first) {
first = false;
if (!line.startsWith(begin))
throw new ErrnoException("Could not find begin marker", OsConstants.EBADMSG);
++beginEnds;
continue;
}
if (line.startsWith(end) && line.length() > end.length()) {
errnoStdout = Integer.valueOf(line.substring(end.length() + 1));
++beginEnds;
break;
}
if (output != null)
output.add(line);
Log.v(TAG, "stdout: " + line);
}
first = true;
while ((line = stderr.readLine()) != null) {
if (first) {
first = false;
if (!line.startsWith(begin))
throw new ErrnoException("Could not find begin marker", OsConstants.EBADMSG);
++beginEnds;
continue;
}
if (line.startsWith(end) && line.length() > end.length()) {
errnoStderr = Integer.valueOf(line.substring(end.length() + 1));
++beginEnds;
break;
}
Log.v(TAG, "stderr: " + line);
}
if (errnoStderr != errnoStdout || beginEnds != 4)
throw new ErrnoException("Incorrect errno reporting", OsConstants.EBADMSG);
return errnoStdout;
}
public class NoRootException extends Exception {
}
}
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