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/*
* Copyright © 2019-2020 WireGuard LLC. All Rights Reserved.
* SPDX-License-Identifier: Apache-2.0
*/
package com.wireguard.android.util;
import android.content.Context;
import android.system.OsConstants;
import android.util.Base64;
import com.wireguard.android.util.RootShell.RootShellException;
import com.wireguard.crypto.Ed25519;
import com.wireguard.util.NonNullForAll;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.charset.StandardCharsets;
import java.security.InvalidParameterException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import androidx.annotation.Nullable;
/**
* Class that implements the logic for downloading and loading signed, prebuilt modules for
* WireGuard into the running kernel.
*/
@NonNullForAll
@SuppressWarnings("MagicNumber")
public class ModuleLoader {
private static final String MODULE_LIST_URL = "https://download.wireguard.com/android-module/modules.txt.sig";
private static final String MODULE_NAME = "wireguard-%s.ko";
private static final String MODULE_PUBLIC_KEY_BASE64 = "RWRmHuT9PSqtwfsLtEx+QS06BJtLgFYteL9WCNjH7yuyu5Y1DieSN7If";
private static final String MODULE_URL = "https://download.wireguard.com/android-module/%s";
private final File moduleDir;
private final RootShell rootShell;
private final File tmpDir;
private final String userAgent;
/**
* Public constructor for ModuleLoader
*
* @param context A {@link Context} instance.
* @param rootShell A {@link RootShell} instance used to run elevated commands required for module
* loading.
* @param userAgent A {@link String} that represents the User-Agent string used for connections
* to the upstream server.
*/
public ModuleLoader(final Context context, final RootShell rootShell, final String userAgent) {
moduleDir = new File(context.getCacheDir(), "kmod");
tmpDir = new File(context.getCacheDir(), "tmp");
this.rootShell = rootShell;
this.userAgent = userAgent;
}
/**
* Check whether a WireGuard module is already loaded into the kernel.
*
* @return boolean indicating if WireGuard is already enabled in the kernel.
*/
public static boolean isModuleLoaded() {
return new File("/sys/module/wireguard").exists();
}
/**
* Download the correct WireGuard module for the device
*
* @return {@link OsConstants}.EXIT_SUCCESS if everything succeeds, ENOENT otherwise.
* @throws IOException if the remote hash list was not found or empty.
* @throws RootShellException if {@link RootShell} has a failure executing elevated commands.
* @throws NoSuchAlgorithmException if SHA256 algorithm is not available in device JDK.
*/
public Integer download() throws IOException, RootShellException, NoSuchAlgorithmException {
final List<String> output = new ArrayList<>();
rootShell.run(output, "sha256sum /proc/version|cut -d ' ' -f 1");
if (output.size() != 1 || output.get(0).length() != 64)
throw new InvalidParameterException("Invalid sha256 of /proc/version");
final String moduleName = String.format(MODULE_NAME, output.get(0));
HttpURLConnection connection = (HttpURLConnection) new URL(MODULE_LIST_URL).openConnection();
connection.setRequestProperty("User-Agent", userAgent);
connection.connect();
if (connection.getResponseCode() != HttpURLConnection.HTTP_OK)
throw new IOException("Hash list could not be found");
final byte[] input = new byte[1024 * 1024 * 3 /* 3MiB */];
int len;
try (final InputStream inputStream = connection.getInputStream()) {
len = inputStream.read(input);
}
if (len <= 0)
throw new IOException("Hash list was empty");
final Map<String, Sha256Digest> modules = verifySignedHashes(new String(input, 0, len, StandardCharsets.UTF_8));
if (modules == null)
throw new InvalidParameterException("The signature did not verify or invalid hash list format");
if (!modules.containsKey(moduleName))
return OsConstants.ENOENT;
connection = (HttpURLConnection) new URL(String.format(MODULE_URL, moduleName)).openConnection();
connection.setRequestProperty("User-Agent", userAgent);
connection.connect();
if (connection.getResponseCode() != HttpURLConnection.HTTP_OK)
throw new IOException("Module file could not be found, despite being on hash list");
tmpDir.mkdirs();
moduleDir.mkdir();
File tempFile = null;
try {
tempFile = File.createTempFile("UNVERIFIED-", null, tmpDir);
final MessageDigest digest = MessageDigest.getInstance("SHA-256");
try (final InputStream inputStream = connection.getInputStream();
final FileOutputStream outputStream = new FileOutputStream(tempFile)) {
int total = 0;
while ((len = inputStream.read(input)) > 0) {
total += len;
if (total > 1024 * 1024 * 15 /* 15 MiB */)
throw new IOException("File too big");
outputStream.write(input, 0, len);
digest.update(input, 0, len);
}
outputStream.getFD().sync();
}
if (!Arrays.equals(digest.digest(), modules.get(moduleName).bytes))
throw new IOException("Incorrect file hash");
if (!tempFile.renameTo(new File(moduleDir, moduleName)))
throw new IOException("Unable to rename to final destination");
} finally {
if (tempFile != null)
tempFile.delete();
}
return OsConstants.EXIT_SUCCESS;
}
/**
* Load the downloaded module. ModuleLoader#download must be called before this.
*
* @throws IOException if {@link RootShell} has a failure executing elevated commands.
* @throws RootShellException if {@link RootShell} has a failure executing elevated commands.
*/
public void loadModule() throws IOException, RootShellException {
rootShell.run(null, String.format("insmod \"%s/wireguard-$(sha256sum /proc/version|cut -d ' ' -f 1).ko\"", moduleDir.getAbsolutePath()));
}
/**
* Check if the module might already exist in the app's data.
*
* @return boolean indicating whether downloadable module might exist already.
*/
public boolean moduleMightExist() {
return moduleDir.exists() && moduleDir.isDirectory();
}
@Nullable
private Map<String, Sha256Digest> verifySignedHashes(final String signifyDigest) {
byte[] publicKeyBytes = Base64.decode(MODULE_PUBLIC_KEY_BASE64, Base64.DEFAULT);
if (publicKeyBytes == null || publicKeyBytes.length != 32 + 10 || publicKeyBytes[0] != 'E' || publicKeyBytes[1] != 'd')
return null;
final String[] lines = signifyDigest.split("\n", 3);
if (lines.length != 3)
return null;
if (!lines[0].startsWith("untrusted comment: "))
return null;
byte[] signatureBytes = Base64.decode(lines[1], Base64.DEFAULT);
if (signatureBytes == null || signatureBytes.length != 64 + 10)
return null;
for (int i = 0; i < 10; ++i) {
if (signatureBytes[i] != publicKeyBytes[i])
return null;
}
publicKeyBytes = Arrays.copyOfRange(publicKeyBytes, 10, 10 + 32);
signatureBytes = Arrays.copyOfRange(signatureBytes, 10, 10 + 64);
if (!Ed25519.verify(lines[2].getBytes(StandardCharsets.UTF_8), signatureBytes, publicKeyBytes))
return null;
final Map<String, Sha256Digest> hashes = new HashMap<>();
for (final String line : lines[2].split("\n")) {
final String[] components = line.split(" {2}", 2);
if (components.length != 2)
return null;
try {
hashes.put(components[1], new Sha256Digest(components[0]));
} catch (final Exception ignored) {
return null;
}
}
return hashes;
}
private static final class Sha256Digest {
private final byte[] bytes;
private Sha256Digest(final String hex) {
if (hex.length() != 64)
throw new InvalidParameterException("SHA256 hashes must be 32 bytes long");
bytes = new byte[32];
for (int i = 0; i < 32; ++i)
bytes[i] = (byte) Integer.parseInt(hex.substring(i * 2, i * 2 + 2), 16);
}
}
}
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