1 files changed, 186 insertions, 0 deletions
diff --git a/tunnel/src/main/java/com/wireguard/android/util/ModuleLoader.java b/tunnel/src/main/java/com/wireguard/android/util/ModuleLoader.java
new file mode 100644
index 00000000..f09d9a87
--- /dev/null
+++ b/tunnel/src/main/java/com/wireguard/android/util/ModuleLoader.java
@@ -0,0 +1,186 @@
+/*
+ * 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 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 androidx.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;
+    }
+}