Rename app module to ui

Signed-off-by: Harsh Shandilya <me@msfjarvis.dev>

11 files changed, 903 insertions, 0 deletions

diff --git a/ui/src/main/java/com/wireguard/android/util/ClipboardUtils.java b/ui/src/main/java/com/wireguard/android/util/ClipboardUtils.java
new file mode 100644
index 00000000..0df5e96a
--- /dev/null
+++ b/ui/src/main/java/com/wireguard/android/util/ClipboardUtils.java
@@ -0,0 +1,37 @@
+/*
+ * Copyright © 2017-2019 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.wireguard.android.util;
+
+import android.content.ClipData;
+import android.content.ClipboardManager;
+import android.content.Context;
+import com.google.android.material.snackbar.Snackbar;
+import android.view.View;
+import android.widget.TextView;
+
+/**
+ * Standalone utilities for interacting with the system clipboard.
+ */
+
+public final class ClipboardUtils {
+    private ClipboardUtils() {
+        // Prevent instantiation
+    }
+
+    public static void copyTextView(final View view) {
+        if (!(view instanceof TextView))
+            return;
+        final CharSequence text = ((TextView) view).getText();
+        if (text == null || text.length() == 0)
+            return;
+        final Object service = view.getContext().getSystemService(Context.CLIPBOARD_SERVICE);
+        if (!(service instanceof ClipboardManager))
+            return;
+        final CharSequence description = view.getContentDescription();
+        ((ClipboardManager) service).setPrimaryClip(ClipData.newPlainText(description, text));
+        Snackbar.make(view, description + " copied to clipboard", Snackbar.LENGTH_LONG).show();
+    }
+}
diff --git a/ui/src/main/java/com/wireguard/android/util/DownloadsFileSaver.java b/ui/src/main/java/com/wireguard/android/util/DownloadsFileSaver.java
new file mode 100644
index 00000000..7db46fa9
--- /dev/null
+++ b/ui/src/main/java/com/wireguard/android/util/DownloadsFileSaver.java
@@ -0,0 +1,98 @@
+/*
+ * Copyright © 2019 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.wireguard.android.util;
+
+import android.content.ContentResolver;
+import android.content.ContentValues;
+import android.content.Context;
+import android.database.Cursor;
+import android.net.Uri;
+import android.os.Build;
+import android.os.Environment;
+import android.provider.MediaStore;
+import android.provider.MediaStore.MediaColumns;
+
+import com.wireguard.android.R;
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.OutputStream;
+
+public class DownloadsFileSaver {
+
+    public static class DownloadsFile {
+        private Context context;
+        private OutputStream outputStream;
+        private String fileName;
+        private Uri uri;
+
+        private DownloadsFile(final Context context, final OutputStream outputStream, final String fileName, final Uri uri) {
+            this.context = context;
+            this.outputStream = outputStream;
+            this.fileName = fileName;
+            this.uri = uri;
+        }
+
+        public OutputStream getOutputStream() { return outputStream; }
+        public String getFileName() { return fileName; }
+
+        public void delete() {
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q)
+                context.getContentResolver().delete(uri, null, null);
+            else
+                new File(fileName).delete();
+        }
+    }
+
+    public static DownloadsFile save(final Context context, final String name, final String mimeType, final boolean overwriteExisting) throws Exception {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
+            final ContentResolver contentResolver = context.getContentResolver();
+            if (overwriteExisting)
+                contentResolver.delete(MediaStore.Downloads.EXTERNAL_CONTENT_URI, String.format("%s = ?", MediaColumns.DISPLAY_NAME), new String[]{name});
+            final ContentValues contentValues = new ContentValues();
+            contentValues.put(MediaColumns.DISPLAY_NAME, name);
+            contentValues.put(MediaColumns.MIME_TYPE, mimeType);
+            final Uri contentUri = contentResolver.insert(MediaStore.Downloads.EXTERNAL_CONTENT_URI, contentValues);
+            if (contentUri == null)
+                throw new IOException(context.getString(R.string.create_downloads_file_error));
+            final OutputStream contentStream = contentResolver.openOutputStream(contentUri);
+            if (contentStream == null)
+                throw new IOException(context.getString(R.string.create_downloads_file_error));
+            @SuppressWarnings("deprecation")
+            Cursor cursor = contentResolver.query(contentUri, new String[]{MediaColumns.DATA}, null, null, null);
+            String path = null;
+            if (cursor != null) {
+                try {
+                    if (cursor.moveToFirst())
+                        path = cursor.getString(0);
+                } finally {
+                    cursor.close();
+                }
+            }
+            if (path == null) {
+                path = "Download/";
+                cursor = contentResolver.query(contentUri, new String[]{MediaColumns.DISPLAY_NAME}, null, null, null);
+                if (cursor != null) {
+                    try {
+                        if (cursor.moveToFirst())
+                            path += cursor.getString(0);
+                    } finally {
+                        cursor.close();
+                    }
+                }
+            }
+            return new DownloadsFile(context, contentStream, path, contentUri);
+        } else {
+            @SuppressWarnings("deprecation")
+            final File path = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOWNLOADS);
+            final File file = new File(path, name);
+            if (!path.isDirectory() && !path.mkdirs())
+                throw new IOException(context.getString(R.string.create_output_dir_error));
+            return new DownloadsFile(context, new FileOutputStream(file), file.getAbsolutePath(), null);
+        }
+    }
+}
diff --git a/ui/src/main/java/com/wireguard/android/util/ErrorMessages.java b/ui/src/main/java/com/wireguard/android/util/ErrorMessages.java
new file mode 100644
index 00000000..481a6ffb
--- /dev/null
+++ b/ui/src/main/java/com/wireguard/android/util/ErrorMessages.java
@@ -0,0 +1,160 @@
+/*
+ * Copyright © 2018-2019 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.wireguard.android.util;
+
+import android.content.res.Resources;
+import android.os.RemoteException;
+
+import androidx.annotation.Nullable;
+
+import com.wireguard.android.Application;
+import com.wireguard.android.R;
+import com.wireguard.android.backend.BackendException;
+import com.wireguard.android.util.RootShell.RootShellException;
+import com.wireguard.config.BadConfigException;
+import com.wireguard.config.BadConfigException.Location;
+import com.wireguard.config.InetEndpoint;
+import com.wireguard.config.InetNetwork;
+import com.wireguard.config.ParseException;
+import com.wireguard.crypto.Key.Format;
+import com.wireguard.crypto.KeyFormatException;
+import com.wireguard.crypto.KeyFormatException.Type;
+
+import java.net.InetAddress;
+import java.util.EnumMap;
+import java.util.Map;
+
+import java9.util.Maps;
+
+public final class ErrorMessages {
+    private static final Map<BadConfigException.Reason, Integer> BCE_REASON_MAP = new EnumMap<>(Maps.of(
+            BadConfigException.Reason.INVALID_KEY, R.string.bad_config_reason_invalid_key,
+            BadConfigException.Reason.INVALID_NUMBER, R.string.bad_config_reason_invalid_number,
+            BadConfigException.Reason.INVALID_VALUE, R.string.bad_config_reason_invalid_value,
+            BadConfigException.Reason.MISSING_ATTRIBUTE, R.string.bad_config_reason_missing_attribute,
+            BadConfigException.Reason.MISSING_SECTION, R.string.bad_config_reason_missing_section,
+            BadConfigException.Reason.MISSING_VALUE, R.string.bad_config_reason_missing_value,
+            BadConfigException.Reason.SYNTAX_ERROR, R.string.bad_config_reason_syntax_error,
+            BadConfigException.Reason.UNKNOWN_ATTRIBUTE, R.string.bad_config_reason_unknown_attribute,
+            BadConfigException.Reason.UNKNOWN_SECTION, R.string.bad_config_reason_unknown_section
+    ));
+    private static final Map<BackendException.Reason, Integer> BE_REASON_MAP = new EnumMap<>(Maps.of(
+            BackendException.Reason.UNKNOWN_KERNEL_MODULE_NAME, R.string.module_version_error,
+            BackendException.Reason.WG_QUICK_CONFIG_ERROR_CODE, R.string.tunnel_config_error,
+            BackendException.Reason.TUNNEL_MISSING_CONFIG, R.string.no_config_error,
+            BackendException.Reason.VPN_NOT_AUTHORIZED, R.string.vpn_not_authorized_error,
+            BackendException.Reason.UNABLE_TO_START_VPN, R.string.vpn_start_error,
+            BackendException.Reason.TUN_CREATION_ERROR, R.string.tun_create_error,
+            BackendException.Reason.GO_ACTIVATION_ERROR_CODE, R.string.tunnel_on_error
+    ));
+    private static final Map<RootShellException.Reason, Integer> RSE_REASON_MAP = new EnumMap<>(Maps.of(
+            RootShellException.Reason.NO_ROOT_ACCESS, R.string.error_root,
+            RootShellException.Reason.SHELL_MARKER_COUNT_ERROR, R.string.shell_marker_count_error,
+            RootShellException.Reason.SHELL_EXIT_STATUS_READ_ERROR, R.string.shell_exit_status_read_error,
+            RootShellException.Reason.SHELL_START_ERROR, R.string.shell_start_error,
+            RootShellException.Reason.CREATE_BIN_DIR_ERROR, R.string.create_bin_dir_error,
+            RootShellException.Reason.CREATE_TEMP_DIR_ERROR, R.string.create_temp_dir_error
+    ));
+    private static final Map<Format, Integer> KFE_FORMAT_MAP = new EnumMap<>(Maps.of(
+            Format.BASE64, R.string.key_length_explanation_base64,
+            Format.BINARY, R.string.key_length_explanation_binary,
+            Format.HEX, R.string.key_length_explanation_hex
+    ));
+    private static final Map<Type, Integer> KFE_TYPE_MAP = new EnumMap<>(Maps.of(
+            Type.CONTENTS, R.string.key_contents_error,
+            Type.LENGTH, R.string.key_length_error
+    ));
+    private static final Map<Class, Integer> PE_CLASS_MAP = Maps.of(
+            InetAddress.class, R.string.parse_error_inet_address,
+            InetEndpoint.class, R.string.parse_error_inet_endpoint,
+            InetNetwork.class, R.string.parse_error_inet_network,
+            Integer.class, R.string.parse_error_integer
+    );
+
+    private ErrorMessages() {
+        // Prevent instantiation
+    }
+
+    public static String get(@Nullable final Throwable throwable) {
+        final Resources resources = Application.get().getResources();
+        if (throwable == null)
+            return resources.getString(R.string.unknown_error);
+        final Throwable rootCause = rootCause(throwable);
+        final String message;
+        if (rootCause instanceof BadConfigException) {
+            final BadConfigException bce = (BadConfigException) rootCause;
+            final String reason = getBadConfigExceptionReason(resources, bce);
+            final String context = bce.getLocation() == Location.TOP_LEVEL ?
+                    resources.getString(R.string.bad_config_context_top_level,
+                            bce.getSection().getName()) :
+                    resources.getString(R.string.bad_config_context,
+                            bce.getSection().getName(),
+                            bce.getLocation().getName());
+            final String explanation = getBadConfigExceptionExplanation(resources, bce);
+            message = resources.getString(R.string.bad_config_error, reason, context) + explanation;
+        } else if (rootCause instanceof BackendException) {
+            final BackendException be = (BackendException) rootCause;
+            message = resources.getString(BE_REASON_MAP.get(be.getReason()), be.getFormat());
+        } else if (rootCause instanceof RootShellException) {
+            final RootShellException rse = (RootShellException) rootCause;
+            message = resources.getString(RSE_REASON_MAP.get(rse.getReason()), rse.getFormat());
+        } else if (rootCause.getMessage() != null) {
+            message = rootCause.getMessage();
+        } else {
+            final String errorType = rootCause.getClass().getSimpleName();
+            message = resources.getString(R.string.generic_error, errorType);
+        }
+        return message;
+    }
+
+    private static String getBadConfigExceptionExplanation(final Resources resources,
+                                                           final BadConfigException bce) {
+        if (bce.getCause() instanceof KeyFormatException) {
+            final KeyFormatException kfe = (KeyFormatException) bce.getCause();
+            if (kfe.getType() == Type.LENGTH)
+                return resources.getString(KFE_FORMAT_MAP.get(kfe.getFormat()));
+        } else if (bce.getCause() instanceof ParseException) {
+            final ParseException pe = (ParseException) bce.getCause();
+            if (pe.getMessage() != null)
+                return ": " + pe.getMessage();
+        } else if (bce.getLocation() == Location.LISTEN_PORT) {
+            return resources.getString(R.string.bad_config_explanation_udp_port);
+        } else if (bce.getLocation() == Location.MTU) {
+            return resources.getString(R.string.bad_config_explanation_positive_number);
+        } else if (bce.getLocation() == Location.PERSISTENT_KEEPALIVE) {
+            return resources.getString(R.string.bad_config_explanation_pka);
+        }
+        return "";
+    }
+
+    private static String getBadConfigExceptionReason(final Resources resources,
+                                                      final BadConfigException bce) {
+        if (bce.getCause() instanceof KeyFormatException) {
+            final KeyFormatException kfe = (KeyFormatException) bce.getCause();
+            return resources.getString(KFE_TYPE_MAP.get(kfe.getType()));
+        } else if (bce.getCause() instanceof ParseException) {
+            final ParseException pe = (ParseException) bce.getCause();
+            final String type = resources.getString(PE_CLASS_MAP.containsKey(pe.getParsingClass()) ?
+                    PE_CLASS_MAP.get(pe.getParsingClass()) : R.string.parse_error_generic);
+            return resources.getString(R.string.parse_error_reason, type, pe.getText());
+        }
+        return resources.getString(BCE_REASON_MAP.get(bce.getReason()), bce.getText());
+    }
+
+    private static Throwable rootCause(final Throwable throwable) {
+        Throwable cause = throwable;
+        while (cause.getCause() != null) {
+            if (cause instanceof BadConfigException || cause instanceof BackendException ||
+                    cause instanceof RootShellException)
+                break;
+            final Throwable nextCause = cause.getCause();
+            if (nextCause instanceof RemoteException)
+                break;
+            cause = nextCause;
+        }
+        return cause;
+    }
+}
diff --git a/ui/src/main/java/com/wireguard/android/util/ExceptionLoggers.java b/ui/src/main/java/com/wireguard/android/util/ExceptionLoggers.java
new file mode 100644
index 00000000..5c7a38c0
--- /dev/null
+++ b/ui/src/main/java/com/wireguard/android/util/ExceptionLoggers.java
@@ -0,0 +1,36 @@
+/*
+ * Copyright © 2017-2019 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.wireguard.android.util;
+
+import androidx.annotation.Nullable;
+import android.util.Log;
+
+import java9.util.function.BiConsumer;
+
+/**
+ * Helpers for logging exceptions from asynchronous tasks. These can be passed to
+ * {@code CompletionStage.whenComplete()} at the end of an asynchronous future chain.
+ */
+
+public enum ExceptionLoggers implements BiConsumer<Object, Throwable> {
+    D(Log.DEBUG),
+    E(Log.ERROR);
+
+    private static final String TAG = "WireGuard/" + ExceptionLoggers.class.getSimpleName();
+    private final int priority;
+
+    ExceptionLoggers(final int priority) {
+        this.priority = priority;
+    }
+
+    @Override
+    public void accept(final Object result, @Nullable final Throwable throwable) {
+        if (throwable != null)
+            Log.println(Log.ERROR, TAG, Log.getStackTraceString(throwable));
+        else if (priority <= Log.DEBUG)
+            Log.println(priority, TAG, "Future completed successfully");
+    }
+}
diff --git a/ui/src/main/java/com/wireguard/android/util/Extensions.kt b/ui/src/main/java/com/wireguard/android/util/Extensions.kt
new file mode 100644
index 00000000..6b528a85
--- /dev/null
+++ b/ui/src/main/java/com/wireguard/android/util/Extensions.kt
@@ -0,0 +1,16 @@
+/*
+ * Copyright © 2020 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.wireguard.android.util
+
+import android.content.Context
+import android.util.TypedValue
+import androidx.annotation.AttrRes
+
+fun Context.resolveAttribute(@AttrRes attrRes: Int): Int {
+    val typedValue = TypedValue()
+    theme.resolveAttribute(attrRes, typedValue, true)
+    return typedValue.data
+}
diff --git a/ui/src/main/java/com/wireguard/android/util/FragmentUtils.java b/ui/src/main/java/com/wireguard/android/util/FragmentUtils.java
new file mode 100644
index 00000000..5fb9a3bc
--- /dev/null
+++ b/ui/src/main/java/com/wireguard/android/util/FragmentUtils.java
@@ -0,0 +1,27 @@
+/*
+ * Copyright © 2017-2019 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+package com.wireguard.android.util;
+
+import android.content.Context;
+import androidx.preference.Preference;
+import android.view.ContextThemeWrapper;
+
+import com.wireguard.android.activity.SettingsActivity;
+
+public final class FragmentUtils {
+    private FragmentUtils() {
+        // Prevent instantiation
+    }
+
+    public static SettingsActivity getPrefActivity(final Preference preference) {
+        final Context context = preference.getContext();
+        if (context instanceof ContextThemeWrapper) {
+            if (context instanceof SettingsActivity) {
+                return ((SettingsActivity) context);
+            }
+        }
+        return null;
+    }
+}
diff --git a/ui/src/main/java/com/wireguard/android/util/ModuleLoader.java b/ui/src/main/java/com/wireguard/android/util/ModuleLoader.java
new file mode 100644
index 00000000..bf094a5e
--- /dev/null
+++ b/ui/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.util.RootShell.RootShellException;
+
+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.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 RootShell rootShell;
+    private final String userAgent;
+    private final File moduleDir;
+    private final File tmpDir;
+
+    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;
+    }
+
+    public boolean moduleMightExist() {
+        return moduleDir.exists() && moduleDir.isDirectory();
+    }
+
+    public void loadModule() throws IOException, RootShellException {
+        rootShell.run(null, String.format("insmod \"%s/wireguard-$(sha256sum /proc/version|cut -d ' ' -f 1).ko\"", moduleDir.getAbsolutePath()));
+    }
+
+    public static 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, 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");
+        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 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;
+    }
+}
diff --git a/ui/src/main/java/com/wireguard/android/util/ObservableKeyedArrayList.java b/ui/src/main/java/com/wireguard/android/util/ObservableKeyedArrayList.java
new file mode 100644
index 00000000..0ba02184
--- /dev/null
+++ b/ui/src/main/java/com/wireguard/android/util/ObservableKeyedArrayList.java
@@ -0,0 +1,109 @@
+/*
+ * Copyright © 2017-2019 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.wireguard.android.util;
+
+import androidx.databinding.ObservableArrayList;
+import androidx.annotation.Nullable;
+
+import com.wireguard.util.Keyed;
+
+import java.util.Collection;
+import java.util.ListIterator;
+import java.util.Objects;
+
+/**
+ * ArrayList that allows looking up elements by some key property. As the key property must always
+ * be retrievable, this list cannot hold {@code null} elements. Because this class places no
+ * restrictions on the order or duplication of keys, lookup by key, as well as all list modification
+ * operations, require O(n) time.
+ */
+
+public class ObservableKeyedArrayList<K, E extends Keyed<? extends K>>
+        extends ObservableArrayList<E> implements ObservableKeyedList<K, E> {
+    @Override
+    public boolean add(@Nullable final E e) {
+        if (e == null)
+            throw new NullPointerException("Trying to add a null element");
+        return super.add(e);
+    }
+
+    @Override
+    public void add(final int index, @Nullable final E e) {
+        if (e == null)
+            throw new NullPointerException("Trying to add a null element");
+        super.add(index, e);
+    }
+
+    @Override
+    public boolean addAll(final Collection<? extends E> c) {
+        if (c.contains(null))
+            throw new NullPointerException("Trying to add a collection with null element(s)");
+        return super.addAll(c);
+    }
+
+    @Override
+    public boolean addAll(final int index, final Collection<? extends E> c) {
+        if (c.contains(null))
+            throw new NullPointerException("Trying to add a collection with null element(s)");
+        return super.addAll(index, c);
+    }
+
+    @Override
+    public boolean containsAllKeys(final Collection<K> keys) {
+        for (final K key : keys)
+            if (!containsKey(key))
+                return false;
+        return true;
+    }
+
+    @Override
+    public boolean containsKey(final K key) {
+        return indexOfKey(key) >= 0;
+    }
+
+    @Nullable
+    @Override
+    public E get(final K key) {
+        final int index = indexOfKey(key);
+        return index >= 0 ? get(index) : null;
+    }
+
+    @Nullable
+    @Override
+    public E getLast(final K key) {
+        final int index = lastIndexOfKey(key);
+        return index >= 0 ? get(index) : null;
+    }
+
+    @Override
+    public int indexOfKey(final K key) {
+        final ListIterator<E> iterator = listIterator();
+        while (iterator.hasNext()) {
+            final int index = iterator.nextIndex();
+            if (Objects.equals(iterator.next().getKey(), key))
+                return index;
+        }
+        return -1;
+    }
+
+    @Override
+    public int lastIndexOfKey(final K key) {
+        final ListIterator<E> iterator = listIterator(size());
+        while (iterator.hasPrevious()) {
+            final int index = iterator.previousIndex();
+            if (Objects.equals(iterator.previous().getKey(), key))
+                return index;
+        }
+        return -1;
+    }
+
+    @Override
+    public E set(final int index, @Nullable final E e) {
+        if (e == null)
+            throw new NullPointerException("Trying to set a null key");
+        return super.set(index, e);
+    }
+}
diff --git a/ui/src/main/java/com/wireguard/android/util/ObservableKeyedList.java b/ui/src/main/java/com/wireguard/android/util/ObservableKeyedList.java
new file mode 100644
index 00000000..be8ceb9b
--- /dev/null
+++ b/ui/src/main/java/com/wireguard/android/util/ObservableKeyedList.java
@@ -0,0 +1,19 @@
+/*
+ * Copyright © 2017-2019 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.wireguard.android.util;
+
+import androidx.databinding.ObservableList;
+
+import com.wireguard.util.Keyed;
+import com.wireguard.util.KeyedList;
+
+/**
+ * A list that is both keyed and observable.
+ */
+
+public interface ObservableKeyedList<K, E extends Keyed<? extends K>>
+        extends KeyedList<K, E>, ObservableList<E> {
+}
diff --git a/ui/src/main/java/com/wireguard/android/util/ObservableSortedKeyedArrayList.java b/ui/src/main/java/com/wireguard/android/util/ObservableSortedKeyedArrayList.java
new file mode 100644
index 00000000..1d585856
--- /dev/null
+++ b/ui/src/main/java/com/wireguard/android/util/ObservableSortedKeyedArrayList.java
@@ -0,0 +1,198 @@
+/*
+ * Copyright © 2017-2019 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.wireguard.android.util;
+
+import androidx.annotation.Nullable;
+
+import com.wireguard.util.Keyed;
+import com.wireguard.util.SortedKeyedList;
+
+import java.util.AbstractList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.List;
+import java.util.NoSuchElementException;
+import java.util.Set;
+import java.util.Spliterator;
+
+/**
+ * KeyedArrayList that enforces uniqueness and sorted order across the set of keys. This class uses
+ * binary search to improve lookup and replacement times to O(log(n)). However, due to the
+ * array-based nature of this class, insertion and removal of elements with anything but the largest
+ * key still require O(n) time.
+ */
+
+public class ObservableSortedKeyedArrayList<K, E extends Keyed<? extends K>>
+        extends ObservableKeyedArrayList<K, E> implements ObservableSortedKeyedList<K, E> {
+    @Nullable private final Comparator<? super K> comparator;
+    private final transient KeyList<K, E> keyList = new KeyList<>(this);
+
+    @SuppressWarnings("WeakerAccess")
+    public ObservableSortedKeyedArrayList() {
+        comparator = null;
+    }
+
+    public ObservableSortedKeyedArrayList(final Comparator<? super K> comparator) {
+        this.comparator = comparator;
+    }
+
+    public ObservableSortedKeyedArrayList(final Collection<? extends E> c) {
+        this();
+        addAll(c);
+    }
+
+    public ObservableSortedKeyedArrayList(final SortedKeyedList<K, E> other) {
+        this(other.comparator());
+        addAll(other);
+    }
+
+    @Override
+    public boolean add(final E e) {
+        final int insertionPoint = getInsertionPoint(e);
+        if (insertionPoint < 0) {
+            // Skipping insertion is non-destructive if the new and existing objects are the same.
+            if (e == get(-insertionPoint - 1))
+                return false;
+            throw new IllegalArgumentException("Element with same key already exists in list");
+        }
+        super.add(insertionPoint, e);
+        return true;
+    }
+
+    @Override
+    public void add(final int index, final E e) {
+        final int insertionPoint = getInsertionPoint(e);
+        if (insertionPoint < 0)
+            throw new IllegalArgumentException("Element with same key already exists in list");
+        if (insertionPoint != index)
+            throw new IndexOutOfBoundsException("Wrong index given for element");
+        super.add(index, e);
+    }
+
+    @Override
+    public boolean addAll(final Collection<? extends E> c) {
+        boolean didChange = false;
+        for (final E e : c)
+            if (add(e))
+                didChange = true;
+        return didChange;
+    }
+
+    @Override
+    public boolean addAll(int index, final Collection<? extends E> c) {
+        for (final E e : c)
+            add(index++, e);
+        return true;
+    }
+
+    @Nullable
+    @Override
+    public Comparator<? super K> comparator() {
+        return comparator;
+    }
+
+    @Override
+    public K firstKey() {
+        if (isEmpty())
+            // The parameter in the exception is only to shut
+            // lint up, we never care for the exception message.
+            throw new NoSuchElementException("Empty set");
+        return get(0).getKey();
+    }
+
+    private int getInsertionPoint(final E e) {
+        if (comparator != null) {
+            return -Collections.binarySearch(keyList, e.getKey(), comparator) - 1;
+        } else {
+            @SuppressWarnings("unchecked") final List<Comparable<? super K>> list =
+                    (List<Comparable<? super K>>) keyList;
+            return -Collections.binarySearch(list, e.getKey()) - 1;
+        }
+    }
+
+    @Override
+    public int indexOfKey(final K key) {
+        final int index;
+        if (comparator != null) {
+            index = Collections.binarySearch(keyList, key, comparator);
+        } else {
+            @SuppressWarnings("unchecked") final List<Comparable<? super K>> list =
+                    (List<Comparable<? super K>>) keyList;
+            index = Collections.binarySearch(list, key);
+        }
+        return index >= 0 ? index : -1;
+    }
+
+    @Override
+    public Set<K> keySet() {
+        return keyList;
+    }
+
+    @Override
+    public int lastIndexOfKey(final K key) {
+        // There can never be more than one element with the same key in the list.
+        return indexOfKey(key);
+    }
+
+    @Override
+    public K lastKey() {
+        if (isEmpty())
+            // The parameter in the exception is only to shut
+            // lint up, we never care for the exception message.
+            throw new NoSuchElementException("Empty set");
+        return get(size() - 1).getKey();
+    }
+
+    @Override
+    public E set(final int index, final E e) {
+        final int order;
+        if (comparator != null) {
+            order = comparator.compare(e.getKey(), get(index).getKey());
+        } else {
+            @SuppressWarnings("unchecked") final Comparable<? super K> key =
+                    (Comparable<? super K>) e.getKey();
+            order = key.compareTo(get(index).getKey());
+        }
+        if (order != 0) {
+            // Allow replacement if the new key would be inserted adjacent to the replaced element.
+            final int insertionPoint = getInsertionPoint(e);
+            if (insertionPoint < index || insertionPoint > index + 1)
+                throw new IndexOutOfBoundsException("Wrong index given for element");
+        }
+        return super.set(index, e);
+    }
+
+    @Override
+    public Collection<E> values() {
+        return this;
+    }
+
+    private static final class KeyList<K, E extends Keyed<? extends K>>
+            extends AbstractList<K> implements Set<K> {
+        private final ObservableSortedKeyedArrayList<K, E> list;
+
+        private KeyList(final ObservableSortedKeyedArrayList<K, E> list) {
+            this.list = list;
+        }
+
+        @Override
+        public K get(final int index) {
+            return list.get(index).getKey();
+        }
+
+        @Override
+        public int size() {
+            return list.size();
+        }
+
+        @Override
+        @SuppressWarnings("EmptyMethod")
+        public Spliterator<K> spliterator() {
+            return super.spliterator();
+        }
+    }
+}
diff --git a/ui/src/main/java/com/wireguard/android/util/ObservableSortedKeyedList.java b/ui/src/main/java/com/wireguard/android/util/ObservableSortedKeyedList.java
new file mode 100644
index 00000000..d796704e
--- /dev/null
+++ b/ui/src/main/java/com/wireguard/android/util/ObservableSortedKeyedList.java
@@ -0,0 +1,17 @@
+/*
+ * Copyright © 2017-2019 WireGuard LLC. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package com.wireguard.android.util;
+
+import com.wireguard.util.Keyed;
+import com.wireguard.util.SortedKeyedList;
+
+/**
+ * A list that is both sorted/keyed and observable.
+ */
+
+public interface ObservableSortedKeyedList<K, E extends Keyed<? extends K>>
+        extends ObservableKeyedList<K, E>, SortedKeyedList<K, E> {
+}