KeyEncoding: Clean up and reorganize to match style

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

3 files changed, 85 insertions, 71 deletions

diff --git a/app/src/main/java/com/wireguard/config/Interface.java b/app/src/main/java/com/wireguard/config/Interface.java
index 9f74bab0..d583f37b 100644
--- a/app/src/main/java/com/wireguard/config/Interface.java
+++ b/app/src/main/java/com/wireguard/config/Interface.java
@@ -91,7 +91,7 @@ public class Interface extends BaseObservable implements Observable {
 
     public void setPrivateKey(String privateKey) {
         // Avoid exceptions from Keypair while the user is typing.
-        if (privateKey.length() != KeyEncoding.WG_KEY_LEN_BASE64)
+        if (privateKey.length() != KeyEncoding.KEY_LENGTH_BASE64)
             return;
         keypair = new Keypair(privateKey);
         notifyPropertyChanged(BR.privateKey);
diff --git a/app/src/main/java/com/wireguard/crypto/KeyEncoding.java b/app/src/main/java/com/wireguard/crypto/KeyEncoding.java
index c62657cb..070a1a99 100644
--- a/app/src/main/java/com/wireguard/crypto/KeyEncoding.java
+++ b/app/src/main/java/com/wireguard/crypto/KeyEncoding.java
@@ -1,75 +1,91 @@
-/* Copyright (C) 2015-2017 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
- *
- * This is a specialized constant-time base64 implementation that resists side-channel attacks.
- */
+/* Copyright (C) 2015-2017 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved. */
 
 package com.wireguard.crypto;
 
-public class KeyEncoding {
-	public static final int WG_KEY_LEN = 32;
-	public static final int WG_KEY_LEN_BASE64 = 44;
+/**
+ * This is a specialized constant-time base64 implementation that resists side-channel attacks.
+ */
 
-	private static void encodeBase64(char dest[], final int dest_offset, final byte src[], final int src_offset) {
-		final byte input[] = { (byte)((src[0 + src_offset] >>> 2) & 63),
-				       (byte)(((src[0 + src_offset] << 4) | ((src[1 + src_offset] & 0xff) >>> 4)) & 63),
-				       (byte)(((src[1 + src_offset] << 2) | ((src[2 + src_offset] & 0xff) >>> 6)) & 63),
-				       (byte)(src[2 + src_offset] & 63) };
-		for (int i = 0; i < 4; ++i)
-			dest[i + dest_offset] = (char)(input[i] + 'A'
-						+ (((25 - input[i]) >>> 8) & 6)
-						- (((51 - input[i]) >>> 8) & 75)
-						- (((61 - input[i]) >>> 8) & 15)
-						+ (((62 - input[i]) >>> 8) & 3));
-	}
+public class KeyEncoding {
+    public static final int KEY_LENGTH = 32;
+    public static final int KEY_LENGTH_BASE64 = 44;
+    private static final String KEY_LENGTH_BASE64_EXCEPTION_MESSAGE =
+            "WireGuard base64 keys must be 44 characters encoding 32 bytes";
 
-	public static String keyToBase64(final byte key[]) {
-		if (key.length != WG_KEY_LEN)
-			throw new IllegalArgumentException("WireGuard keys must be 32 bytes");
-		final char base64[] = new char[WG_KEY_LEN_BASE64];
-		int i;
-		for (i = 0; i < WG_KEY_LEN / 3; ++i)
-			encodeBase64(base64, i * 4, key, i * 3);
-		final byte endSegment[] = { key[i * 3 + 0], key[i * 3 + 1], 0 };
-		encodeBase64(base64, i * 4, endSegment, 0);
-		base64[WG_KEY_LEN_BASE64 - 1] = '=';
-		return new String(base64);
-	}
+    private static int decodeBase64(final char[] src, final int src_offset) {
+        int val = 0;
+        for (int i = 0; i < 4; ++i) {
+            final char c = src[i + src_offset];
+            val |= (-1
+                    + ((((('A' - 1) - c) & (c - ('Z' + 1))) >>> 8) & (c - 64))
+                    + ((((('a' - 1) - c) & (c - ('z' + 1))) >>> 8) & (c - 70))
+                    + ((((('0' - 1) - c) & (c - ('9' + 1))) >>> 8) & (c + 5))
+                    + ((((('+' - 1) - c) & (c - ('+' + 1))) >>> 8) & 63)
+                    + ((((('/' - 1) - c) & (c - ('/' + 1))) >>> 8) & 64)
+            ) << (18 - 6 * i);
+        }
+        return val;
+    }
 
-	private static int decodeBase64(final char src[], int src_offset) {
-		int val = 0;
-		for (int i = 0; i < 4; ++i)
-			val |= (-1
-				    + ((((('A' - 1) - src[i + src_offset]) & (src[i + src_offset] - ('Z' + 1))) >>> 8) & (src[i + src_offset] - 64))
-				    + ((((('a' - 1) - src[i + src_offset]) & (src[i + src_offset] - ('z' + 1))) >>> 8) & (src[i + src_offset] - 70))
-				    + ((((('0' - 1) - src[i + src_offset]) & (src[i + src_offset] - ('9' + 1))) >>> 8) & (src[i + src_offset] + 5))
-				    + ((((('+' - 1) - src[i + src_offset]) & (src[i + src_offset] - ('+' + 1))) >>> 8) & 63)
-				    + ((((('/' - 1) - src[i + src_offset]) & (src[i + src_offset] - ('/' + 1))) >>> 8) & 64)
-				) << (18 - 6 * i);
-		return val;
-	}
+    private static void encodeBase64(final byte[] src, final int src_offset,
+                                     char[] dest, final int dest_offset) {
+        final byte[] input = {
+                (byte) ((src[0 + src_offset] >>> 2) & 63),
+                (byte) ((src[0 + src_offset] << 4 | ((src[1 + src_offset] & 0xff) >>> 4)) & 63),
+                (byte) ((src[1 + src_offset] << 2 | ((src[2 + src_offset] & 0xff) >>> 6)) & 63),
+                (byte) ((src[2 + src_offset]) & 63),
+        };
+        for (int i = 0; i < 4; ++i) {
+            dest[i + dest_offset] = (char) (input[i] + 'A'
+                    + (((25 - input[i]) >>> 8) & 6)
+                    - (((51 - input[i]) >>> 8) & 75)
+                    - (((61 - input[i]) >>> 8) & 15)
+                    + (((62 - input[i]) >>> 8) & 3));
+        }
+    }
 
-	public static byte[] keyFromBase64(final String input) {
-		final char base64[] = input.toCharArray();
-		if (base64.length != WG_KEY_LEN_BASE64 || base64[WG_KEY_LEN_BASE64 - 1] != '=')
-			throw new IllegalArgumentException("WireGuard base64 keys must be 44 characters encoding 32 bytes");
-		final byte key[] = new byte[WG_KEY_LEN];
-		int i;
-		int val;
+    public static byte[] keyFromBase64(final String str) {
+        final char[] input = str.toCharArray();
+        final byte[] key = new byte[KEY_LENGTH];
+        if (input.length != KEY_LENGTH_BASE64 || input[KEY_LENGTH_BASE64 - 1] != '=')
+            throw new IllegalArgumentException(KEY_LENGTH_BASE64_EXCEPTION_MESSAGE);
+        int i;
+        for (i = 0; i < KEY_LENGTH / 3; ++i) {
+            final int val = decodeBase64(input, i * 4);
+            if (val < 0)
+                throw new IllegalArgumentException(KEY_LENGTH_BASE64_EXCEPTION_MESSAGE);
+            key[i * 3 + 0] = (byte) ((val >>> 16) & 0xff);
+            key[i * 3 + 1] = (byte) ((val >>> 8) & 0xff);
+            key[i * 3 + 2] = (byte) (val & 0xff);
+        }
+        final char[] endSegment = {
+                input[i * 4 + 0],
+                input[i * 4 + 1],
+                input[i * 4 + 2],
+                'A',
+        };
+        final int val = decodeBase64(endSegment, 0);
+        if (val < 0 || (val & 0xff) != 0)
+            throw new IllegalArgumentException(KEY_LENGTH_BASE64_EXCEPTION_MESSAGE);
+        key[i * 3 + 0] = (byte) ((val >>> 16) & 0xff);
+        key[i * 3 + 1] = (byte) ((val >>> 8) & 0xff);
+        return key;
+    }
 
-		for (i = 0; i < WG_KEY_LEN / 3; ++i) {
-			val = decodeBase64(base64, i * 4);
-			if (val < 0)
-				throw new IllegalArgumentException("WireGuard base64 keys must be 44 characters encoding 32 bytes");
-			key[i * 3 + 0] = (byte)((val >>> 16) & 0xff);
-			key[i * 3 + 1] = (byte)((val >>> 8) & 0xff);
-			key[i * 3 + 2] = (byte)(val & 0xff);
-		}
-		final char endSegment[] = { base64[i * 4 + 0], base64[i * 4 + 1], base64[i * 4 + 2], 'A' };
-		val = decodeBase64(endSegment, 0);
-		if (val < 0 || (val & 0xff) != 0)
-			throw new IllegalArgumentException("WireGuard base64 keys must be 44 characters encoding 32 bytes");
-		key[i * 3 + 0] = (byte)((val >>> 16) & 0xff);
-		key[i * 3 + 1] = (byte)((val >>> 8) & 0xff);
-		return key;
-	}
+    public static String keyToBase64(final byte[] key) {
+        final char[] output = new char[KEY_LENGTH_BASE64];
+        if (key.length != KEY_LENGTH)
+            throw new IllegalArgumentException("WireGuard keys must be 32 bytes");
+        int i;
+        for (i = 0; i < KEY_LENGTH / 3; ++i)
+            encodeBase64(key, i * 3, output, i * 4);
+        final byte[] endSegment = {
+                key[i * 3 + 0],
+                key[i * 3 + 1],
+                0,
+        };
+        encodeBase64(endSegment, 0, output, i * 4);
+        output[KEY_LENGTH_BASE64 - 1] = '=';
+        return new String(output);
+    }
 }
diff --git a/app/src/main/java/com/wireguard/crypto/Keypair.java b/app/src/main/java/com/wireguard/crypto/Keypair.java
index 71c7066c..bd6fd90f 100644
--- a/app/src/main/java/com/wireguard/crypto/Keypair.java
+++ b/app/src/main/java/com/wireguard/crypto/Keypair.java
@@ -1,7 +1,5 @@
 package com.wireguard.crypto;
 
-import android.util.Base64;
-
 import java.security.SecureRandom;
 
 /**
@@ -11,7 +9,7 @@ import java.security.SecureRandom;
 public class Keypair {
     private static byte[] generatePrivateKey() {
         final SecureRandom secureRandom = new SecureRandom();
-        final byte[] privateKey = new byte[KeyEncoding.WG_KEY_LEN];
+        final byte[] privateKey = new byte[KeyEncoding.KEY_LENGTH];
         secureRandom.nextBytes(privateKey);
         privateKey[0] &= 248;
         privateKey[31] &= 127;
@@ -20,7 +18,7 @@ public class Keypair {
     }
 
     private static byte[] generatePublicKey(byte[] privateKey) {
-        final byte[] publicKey = new byte[KeyEncoding.WG_KEY_LEN];
+        final byte[] publicKey = new byte[KeyEncoding.KEY_LENGTH];
         Curve25519.eval(publicKey, 0, privateKey, null);
         return publicKey;
     }