Download modules after verifying signify signature

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

app/build.gradle

@@ -80,6 +80,7 @@ ext {
     // If you choose to upgrade to minSDK 24 then you should also disable Jetifier from
     // gradle.properties.
     zxingEmbeddedVersion = '3.6.0'
+    eddsaVersion = '0.3.0'
 }
 
 dependencies {
@@ -94,6 +95,7 @@ dependencies {
     implementation "com.journeyapps:zxing-android-embedded:$zxingEmbeddedVersion"
     implementation "net.sourceforge.streamsupport:android-retrofuture:$streamsupportVersion"
     implementation "net.sourceforge.streamsupport:android-retrostreams:$streamsupportVersion"
+    implementation "net.i2p.crypto:eddsa:$eddsaVersion"
 }
 
 tasks.withType(JavaCompile) {

app/src/main/java/com/wireguard/android/Application.java

@@ -22,6 +22,7 @@ import com.wireguard.android.backend.WgQuickBackend;
 import com.wireguard.android.configStore.FileConfigStore;
 import com.wireguard.android.model.TunnelManager;
 import com.wireguard.android.util.AsyncWorker;
+import com.wireguard.android.util.ModuleLoader;
 import com.wireguard.android.util.RootShell;
 import com.wireguard.android.util.ToolsInstaller;
 
@@ -38,6 +39,7 @@ public class Application extends android.app.Application {
     @SuppressWarnings("NullableProblems") private RootShell rootShell;
     @SuppressWarnings("NullableProblems") private SharedPreferences sharedPreferences;
     @SuppressWarnings("NullableProblems") private ToolsInstaller toolsInstaller;
+    @SuppressWarnings("NullableProblems") private ModuleLoader moduleLoader;
     @SuppressWarnings("NullableProblems") private TunnelManager tunnelManager;
 
     public Application() {
@@ -57,9 +59,19 @@ public class Application extends android.app.Application {
         synchronized (app.futureBackend) {
             if (app.backend == null) {
                 Backend backend = null;
-                if (new File("/sys/module/wireguard").exists()) {
+                boolean didStartRootShell = false;
+                if (!app.moduleLoader.isModuleLoaded() && app.moduleLoader.moduleMightExist()) {
                     try {
                         app.rootShell.start();
+                        didStartRootShell = true;
+                        app.moduleLoader.loadModule();
+                    } catch (final Exception ignored) {
+                    }
+                }
+                if (app.moduleLoader.isModuleLoaded()) {
+                    try {
+                        if (!didStartRootShell)
+                            app.rootShell.start();
                         backend = new WgQuickBackend(app.getApplicationContext());
                     } catch (final Exception ignored) {
                     }
@@ -87,6 +99,9 @@ public class Application extends android.app.Application {
     public static ToolsInstaller getToolsInstaller() {
         return get().toolsInstaller;
     }
+    public static ModuleLoader getModuleLoader() {
+        return get().moduleLoader;
+    }
 
     public static TunnelManager getTunnelManager() {
         return get().tunnelManager;
@@ -113,6 +128,7 @@ public class Application extends android.app.Application {
         asyncWorker = new AsyncWorker(AsyncTask.SERIAL_EXECUTOR, new Handler(Looper.getMainLooper()));
         rootShell = new RootShell(getApplicationContext());
         toolsInstaller = new ToolsInstaller(getApplicationContext());
+        moduleLoader = new ModuleLoader(getApplicationContext());
 
         sharedPreferences = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());
         if (Build.VERSION.SDK_INT < Build.VERSION_CODES.Q) {

app/src/main/java/com/wireguard/android/activity/SettingsActivity.java

@@ -110,6 +110,19 @@ public class SettingsActivity extends ThemeChangeAwareActivity {
                         screen.removePreference(pref);
                 }
             });
+
+            final Preference moduleInstaller = getPreferenceManager().findPreference("module_downloader");
+            moduleInstaller.setVisible(false);
+            if (Application.getModuleLoader().isModuleLoaded()) {
+                screen.removePreference(moduleInstaller);
+            } else {
+                Application.getAsyncWorker().runAsync(Application.getRootShell()::start).whenComplete((v, e) -> {
+                    if (e == null)
+                        moduleInstaller.setVisible(true);
+                    else
+                        screen.removePreference(moduleInstaller);
+                });
+            }
         }
     }
 }

app/src/main/java/com/wireguard/android/preference/ModuleDownloaderPreference.java

@@ -0,0 +1,91 @@
+/*
+ * Copyright © 2019 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.wireguard.android.preference;
+
+import android.content.Context;
+import android.content.Intent;
+import android.system.OsConstants;
+import android.util.AttributeSet;
+import android.widget.Toast;
+
+import com.wireguard.android.Application;
+import com.wireguard.android.R;
+import com.wireguard.android.util.ModuleLoader;
+import com.wireguard.android.util.ToolsInstaller;
+
+import androidx.annotation.Nullable;
+import androidx.preference.Preference;
+
+public class ModuleDownloaderPreference extends Preference {
+    private State state = State.INITIAL;
+
+    public ModuleDownloaderPreference(final Context context, final AttributeSet attrs) {
+        super(context, attrs);
+    }
+
+    @Override
+    public CharSequence getSummary() {
+        return getContext().getString(state.messageResourceId);
+    }
+
+    @Override
+    public CharSequence getTitle() {
+        return getContext().getString(R.string.module_installer_title);
+    }
+
+    @Override
+    protected void onClick() {
+        setState(State.WORKING);
+        Application.getAsyncWorker().supplyAsync(Application.getModuleLoader()::download).whenComplete(this::onDownloadResult);
+    }
+
+    private void onDownloadResult(final Integer result, @Nullable final Throwable throwable) {
+        if (throwable != null) {
+            setState(State.FAILURE);
+            Toast.makeText(getContext(), throwable.getMessage(), Toast.LENGTH_LONG).show();
+        } else if (result == OsConstants.ENOENT)
+            setState(State.NOTFOUND);
+        else if (result == OsConstants.EXIT_SUCCESS) {
+            setState(State.SUCCESS);
+            Application.getAsyncWorker().runAsync(() -> {
+                Thread.sleep(1000 * 5);
+                Intent i = getContext().getPackageManager().getLaunchIntentForPackage(getContext().getPackageName());
+                if (i == null)
+                    return;
+                i.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
+                i.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
+                Application.get().startActivity(i);
+                System.exit(0);
+            });
+        } else
+            setState(State.FAILURE);
+    }
+
+    private void setState(final State state) {
+        if (this.state == state)
+            return;
+        this.state = state;
+        if (isEnabled() != state.shouldEnableView)
+            setEnabled(state.shouldEnableView);
+        notifyChanged();
+    }
+
+    private enum State {
+        INITIAL(R.string.module_installer_initial, true),
+        FAILURE(R.string.module_installer_error, true),
+        WORKING(R.string.module_installer_working, false),
+        SUCCESS(R.string.module_installer_success, false),
+        NOTFOUND(R.string.module_installer_not_found, false);
+
+        private final int messageResourceId;
+        private final boolean shouldEnableView;
+
+        State(final int messageResourceId, final boolean shouldEnableView) {
+            this.messageResourceId = messageResourceId;
+            this.shouldEnableView = shouldEnableView;
+        }
+    }
+}

app/src/main/java/com/wireguard/android/util/ModuleLoader.java

@@ -0,0 +1,186 @@
+/*
+ * Copyright © 2019 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.Application;
+import com.wireguard.android.BuildConfig;
+import com.wireguard.android.util.RootShell.NoRootException;
+
+import net.i2p.crypto.eddsa.EdDSAEngine;
+import net.i2p.crypto.eddsa.EdDSAPublicKey;
+import net.i2p.crypto.eddsa.spec.EdDSANamedCurveTable;
+import net.i2p.crypto.eddsa.spec.EdDSAParameterSpec;
+import net.i2p.crypto.eddsa.spec.EdDSAPublicKeySpec;
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+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.security.Signature;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import javax.annotation.Nullable;
+
+public class ModuleLoader {
+    private static final String MODULE_PUBLIC_KEY_BASE64 = "RWRmHuT9PSqtwfsLtEx+QS06BJtLgFYteL9WCNjH7yuyu5Y1DieSN7If";
+    private static final String MODULE_LIST_URL = "https://download.wireguard.com/android-module/modules.txt.sig";
+    private static final String MODULE_URL = "https://download.wireguard.com/android-module/%s";
+    private static final String MODULE_NAME = "wireguard-%s.ko";
+
+    private final File moduleDir;
+    private final File tmpDir;
+
+    public ModuleLoader(final Context context) {
+        moduleDir = new File(context.getCacheDir(), "kmod");
+        tmpDir = new File(context.getCacheDir(), "tmp");
+    }
+
+    public boolean moduleMightExist() {
+        return moduleDir.exists() && moduleDir.isDirectory();
+    }
+
+    public void loadModule() throws IOException, NoRootException {
+        Application.getRootShell().run(null, String.format("insmod \"%s/wireguard-$(sha256sum /proc/version|cut -d ' ' -f 1).ko\"", moduleDir.getAbsolutePath()));
+    }
+
+    public boolean isModuleLoaded() {
+        return new File("/sys/module/wireguard").exists();
+    }
+
+    private static final class Sha256Digest {
+        private 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);
+        }
+    }
+
+    @Nullable
+    private Map<String, Sha256Digest> verifySignedHashes(final String signifyDigest) {
+        final 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;
+
+        final 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;
+        }
+
+        try {
+            EdDSAParameterSpec parameterSpec = EdDSANamedCurveTable.getByName(EdDSANamedCurveTable.ED_25519);
+            Signature signature = new EdDSAEngine(MessageDigest.getInstance(parameterSpec.getHashAlgorithm()));
+            byte[] rawPublicKeyBytes = new byte[32];
+            System.arraycopy(publicKeyBytes, 10, rawPublicKeyBytes, 0, 32);
+            signature.initVerify(new EdDSAPublicKey(new EdDSAPublicKeySpec(rawPublicKeyBytes, parameterSpec)));
+            signature.update(lines[2].getBytes(StandardCharsets.UTF_8));
+            if (!signature.verify(signatureBytes, 10, 64))
+                return null;
+        } catch (final Exception ignored) {
+            return null;
+        }
+
+        Map<String, Sha256Digest> hashes = new HashMap<>();
+        for (final String line : lines[2].split("\n")) {
+            final String[] components = line.split("  ", 2);
+            if (components.length != 2)
+                return null;
+            try {
+                hashes.put(components[1], new Sha256Digest(components[0]));
+            } catch (final Exception ignored) {
+                return null;
+            }
+        }
+        return hashes;
+    }
+
+    public Integer download() throws IOException, NoRootException, NoSuchAlgorithmException {
+        final List<String> output = new ArrayList<>();
+        Application.getRootShell().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));
+        final String userAgent = String.format("WireGuard/%s (Android)", BuildConfig.VERSION_NAME); //TODO: expand a bit
+
+        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");
+        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);
+            MessageDigest digest = MessageDigest.getInstance("SHA-256");
+            try (final InputStream inputStream = connection.getInputStream();
+                 final OutputStream 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);
+                }
+            }
+            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;
+    }
+}

app/src/main/res/values/strings.xml

@@ -99,6 +99,12 @@
     <string name="log_export_title">Export log file</string>
     <string name="logcat_error">Unable to run logcat: </string>
     <string name="module_version_error">Unable to determine kernel module version</string>
+    <string name="module_installer_not_found">No modules are available for your device</string>
+    <string name="module_installer_initial">The experimental kernel module can improve performance</string>
+    <string name="module_installer_success">Success. The application will restart in 5 seconds</string>
+    <string name="module_installer_title">Download and install kernel module</string>
+    <string name="module_installer_working">Downloading and installing…</string>
+    <string name="module_installer_error">Something went wrong. Please try again</string>
     <string name="mtu">MTU</string>
     <string name="multiple_tunnels_error">Only one userspace tunnel can run at a time</string>
     <string name="name">Name</string>

app/src/main/res/xml/preferences.xml

@@ -6,6 +6,7 @@
         android:key="restore_on_boot"
         android:summary="@string/restore_on_boot_summary"
         android:title="@string/restore_on_boot_title" />
+    <com.wireguard.android.preference.ModuleDownloaderPreference android:key="module_downloader" />
     <com.wireguard.android.preference.ToolsInstallerPreference android:key="tools_installer" />
     <com.wireguard.android.preference.ZipExporterPreference />
     <com.wireguard.android.preference.LogExporterPreference />