TorUtils: new utility for Tor/Onion addresses

Move Tor/Onion related code there.

Also adds tests.

core/src/main/java/org/bitcoinj/core/PeerAddress.java

@@ -17,12 +17,11 @@
 
 package org.bitcoinj.core;
 
-import com.google.common.io.BaseEncoding;
 import org.bitcoinj.base.VarInt;
 import org.bitcoinj.base.internal.Buffers;
 import org.bitcoinj.base.internal.TimeUtils;
-import org.bitcoinj.crypto.internal.CryptoUtils;
 import org.bitcoinj.base.internal.ByteUtils;
+import org.bitcoinj.crypto.internal.TorUtils;
 
 import javax.annotation.Nullable;
 import java.net.Inet4Address;
@@ -58,7 +57,6 @@ public class PeerAddress {
     private final Services services;
     private final Instant time;
 
-    private static final BaseEncoding BASE32 = BaseEncoding.base32().omitPadding().lowerCase();
     private static final byte[] ONIONCAT_PREFIX = ByteUtils.parseHex("fd87d87eeb43");
 
     // BIP-155 reserved network IDs, see: https://github.com/bitcoin/bips/blob/master/bip-0155.mediawiki
@@ -191,18 +189,13 @@ public class PeerAddress {
                     case TORV2:
                         if (addrLen != 10)
                             throw new ProtocolException("invalid length of TORv2 address: " + addrLen);
-                        hostname = BASE32.encode(addrBytes) + ".onion";
+                        hostname = TorUtils.encodeOnionUrlV2(addrBytes);
                         addr = null;
                         break;
                     case TORV3:
                         if (addrLen != 32)
                             throw new ProtocolException("invalid length of TORv3 address: " + addrLen);
-                        byte torVersion = 0x03;
+                        hostname = TorUtils.encodeOnionUrlV3(addrBytes);
-                        byte[] onionAddress = new byte[35];
-                        System.arraycopy(addrBytes, 0, onionAddress, 0, 32);
-                        System.arraycopy(CryptoUtils.onionChecksum(addrBytes, torVersion), 0, onionAddress, 32, 2);
-                        onionAddress[34] = torVersion;
-                        hostname = BASE32.encode(onionAddress) + ".onion";
                         addr = null;
                         break;
                     case I2P:
@@ -222,7 +215,7 @@ public class PeerAddress {
             byte[] addrBytes = Buffers.readBytes(payload, 16);
             if (Arrays.equals(ONIONCAT_PREFIX, Arrays.copyOf(addrBytes, 6))) {
                 byte[] onionAddress = Arrays.copyOfRange(addrBytes, 6, 16);
-                hostname = BASE32.encode(onionAddress) + ".onion";
+                hostname = TorUtils.encodeOnionUrlV2(onionAddress);
             } else {
                 addr = getByAddress(addrBytes);
                 hostname = null;
@@ -273,24 +266,17 @@ public class PeerAddress {
                     throw new IllegalStateException();
                 }
             } else if (addr == null && hostname != null && hostname.toLowerCase(Locale.ROOT).endsWith(".onion")) {
-                byte[] onionAddress = BASE32.decode(hostname.substring(0, hostname.length() - 6));
+                byte[] onionAddress = TorUtils.decodeOnionUrl(hostname);
                 if (onionAddress.length == 10) {
                     // TORv2
                     buf.put((byte) 0x03);
                     VarInt.of(10).write(buf);
                     buf.put(onionAddress);
-                } else if (onionAddress.length == 32 + 2 + 1) {
+                } else if (onionAddress.length == 32) {
                     // TORv3
                     buf.put((byte) 0x04);
                     VarInt.of(32).write(buf);
-                    byte[] pubkey = Arrays.copyOfRange(onionAddress, 0, 32);
+                    buf.put(onionAddress);
-                    byte[] checksum = Arrays.copyOfRange(onionAddress, 32, 34);
-                    byte torVersion = onionAddress[34];
-                    if (torVersion != 0x03)
-                        throw new IllegalStateException("version");
-                    if (!Arrays.equals(checksum, CryptoUtils.onionChecksum(pubkey, torVersion)))
-                        throw new IllegalStateException("checksum");
-                    buf.put(pubkey);
                 } else {
                     throw new IllegalStateException();
                 }
@@ -305,7 +291,7 @@ public class PeerAddress {
                 byte[] ipBytes = addr.getAddress();
                 buf.put(mapIntoIPv6(ipBytes));
             } else if (hostname != null && hostname.toLowerCase(Locale.ROOT).endsWith(".onion")) {
-                byte[] onionAddress = BASE32.decode(hostname.substring(0, hostname.length() - 6));
+                byte[] onionAddress = TorUtils.decodeOnionUrl(hostname);
                 if (onionAddress.length == 10) {
                     // TORv2
                     buf.put(ONIONCAT_PREFIX);
@@ -358,13 +344,9 @@ public class PeerAddress {
                     throw new IllegalStateException();
                 }
             } else if (addr == null && hostname != null && hostname.toLowerCase(Locale.ROOT).endsWith(".onion")) {
-                byte[] onionAddress = BASE32.decode(hostname.substring(0, hostname.length() - 6));
+                byte[] onionAddress = TorUtils.decodeOnionUrl(hostname);
-                if (onionAddress.length == 10) {
+                if (onionAddress.length == 10 || onionAddress.length == 32) {
-                    // TORv2
+                    size += VarInt.sizeOf(onionAddress.length) + onionAddress.length;
-                    size += VarInt.sizeOf(10) + 10;
-                } else if (onionAddress.length == 32 + 2 + 1) {
-                    // TORv3
-                    size += VarInt.sizeOf(32) + 32;
                 } else {
                     throw new IllegalStateException();
                 }

core/src/main/java/org/bitcoinj/crypto/internal/CryptoUtils.java

@@ -48,17 +48,4 @@ public class CryptoUtils {
         digest.doFinal(ripmemdHash, 0);
         return ripmemdHash;
     }
-
-    /**
-     * Calculate TOR Onion Checksum (used by PeerAddress)
-     */
-    public static byte[] onionChecksum(byte[] pubkey, byte version) {
-        if (pubkey.length != 32)
-            throw new IllegalArgumentException();
-        SHA3.Digest256 digest256 = new SHA3.Digest256();
-        digest256.update(".onion checksum".getBytes(StandardCharsets.US_ASCII));
-        digest256.update(pubkey);
-        digest256.update(version);
-        return Arrays.copyOf(digest256.digest(), 2);
-    }
 }

core/src/main/java/org/bitcoinj/crypto/internal/TorUtils.java

@@ -0,0 +1,108 @@
+/*
+ * Copyright by the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.bitcoinj.crypto.internal;
+
+import com.google.common.io.BaseEncoding;
+import org.bouncycastle.jcajce.provider.digest.SHA3;
+
+import java.nio.charset.StandardCharsets;
+import java.util.Arrays;
+import java.util.Locale;
+
+import static org.bitcoinj.base.internal.Preconditions.checkArgument;
+
+/**
+ * Utilities for encoding and decoding Onion addresses.
+ */
+public class TorUtils {
+
+    private static final BaseEncoding BASE32 = BaseEncoding.base32().omitPadding().lowerCase();
+
+    /**
+     * Encode an Onion URL from a Tor V2 address.
+     * <p>
+     * See <a href="https://github.com/torproject/torspec/blob/main/address-spec.txt">address-spec.txt</a>
+     *
+     * @param onionAddrBytes Tor V2 address to encode
+     * @return encoded Onion URL
+     */
+    public static String encodeOnionUrlV2(byte[] onionAddrBytes) {
+        checkArgument(onionAddrBytes.length == 10);
+        return BASE32.encode(onionAddrBytes) + ".onion";
+    }
+
+    /**
+     * Encode an Onion URL from a Tor V3 address (pubkey).
+     * <p>
+     * See <a href="https://github.com/torproject/torspec/blob/main/address-spec.txt">address-spec.txt</a>
+     *
+     * @param onionAddrBytes Tor V3 address to encode
+     * @return encoded Onion URL
+     */
+    public static String encodeOnionUrlV3(byte[] onionAddrBytes) {
+        checkArgument(onionAddrBytes.length == 32);
+        byte torVersion = 0x03;
+        byte[] onionAddress = new byte[35];
+        System.arraycopy(onionAddrBytes, 0, onionAddress, 0, 32);
+        System.arraycopy(onionChecksum(onionAddrBytes, torVersion), 0, onionAddress, 32, 2);
+        onionAddress[34] = torVersion;
+        return BASE32.encode(onionAddress) + ".onion";
+    }
+
+    /**
+     * Decode an Onion URL into a Tor V2 or V3 address.
+     * <p>
+     * See <a href="https://github.com/torproject/torspec/blob/main/address-spec.txt">address-spec.txt</a>
+     *
+     * @param onionUrl Onion URL to decode
+     * @return decoded Tor address
+     */
+    public static byte[] decodeOnionUrl(String onionUrl) {
+        if (!onionUrl.toLowerCase(Locale.ROOT).endsWith(".onion"))
+            throw new IllegalArgumentException("not an onion URL: " + onionUrl);
+        byte[] onionAddress = BASE32.decode(onionUrl.substring(0, onionUrl.length() - 6));
+        if (onionAddress.length == 10) {
+            // TORv2
+            return onionAddress;
+        } else if (onionAddress.length == 32 + 2 + 1) {
+            // TORv3
+            byte[] pubkey = Arrays.copyOfRange(onionAddress, 0, 32);
+            byte[] checksum = Arrays.copyOfRange(onionAddress, 32, 34);
+            byte torVersion = onionAddress[34];
+            if (torVersion != 0x03)
+                throw new IllegalArgumentException("unknown version: " + onionUrl);
+            if (!Arrays.equals(checksum, onionChecksum(pubkey, torVersion)))
+                throw new IllegalArgumentException("bad checksum: " + onionUrl);
+            return pubkey;
+        } else {
+            throw new IllegalArgumentException("unrecognizable length: " + onionUrl);
+        }
+    }
+
+    /**
+     * Calculate Onion Checksum
+     */
+    private static byte[] onionChecksum(byte[] pubkey, byte version) {
+        if (pubkey.length != 32)
+            throw new IllegalArgumentException();
+        SHA3.Digest256 digest256 = new SHA3.Digest256();
+        digest256.update(".onion checksum".getBytes(StandardCharsets.US_ASCII));
+        digest256.update(pubkey);
+        digest256.update(version);
+        return Arrays.copyOf(digest256.digest(), 2);
+    }
+}

core/src/test/java/org/bitcoinj/crypto/internal/TorUtilsTest.java

@@ -0,0 +1,52 @@
+/*
+ * Copyright by the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.bitcoinj.crypto.internal;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertArrayEquals;
+
+public class TorUtilsTest {
+    @Test
+    public void roundtripOnionV2() {
+        byte[] onionAddr = new byte[10];
+        byte[] onionAddrCopy = TorUtils.decodeOnionUrl(TorUtils.encodeOnionUrlV2(onionAddr));
+        assertArrayEquals(onionAddr, onionAddrCopy);
+    }
+
+    @Test
+    public void roundtripOnionV3() {
+        byte[] onionAddr = new byte[32];
+        byte[] onionAddrCopy = TorUtils.decodeOnionUrl(TorUtils.encodeOnionUrlV3(onionAddr));
+        assertArrayEquals(onionAddr, onionAddrCopy);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void encodeOnionUrlV2_badLength() {
+        TorUtils.encodeOnionUrlV2(new byte[11]);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void encodeOnionUrlV3_badLength() {
+        TorUtils.encodeOnionUrlV2(new byte[33]);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void decodeOnionUrl_badLength() {
+        TorUtils.decodeOnionUrl("aaa.onion");
+    }
+}