Fix en/decryption of XTEA messages not a multiple of the block size

Reported by Scu11.

Signed-off-by: Graham <gpe@openrs2.dev>

crypto/src/main/java/dev/openrs2/crypto/Xtea.kt

@@ -4,11 +4,14 @@ import io.netty.buffer.ByteBuf
 
 private const val GOLDEN_RATIO = 0x9e3779b9.toInt()
 private const val ROUNDS = 32
+private const val BLOCK_SIZE = 8
+private const val BLOCK_SIZE_MASK = BLOCK_SIZE - 1
 
 fun ByteBuf.xteaEncrypt(index: Int, length: Int, key: IntArray) {
     require(key.size == 4)
 
-    for (i in index until index + length step 8) {
+    val end = (index + length) and BLOCK_SIZE_MASK.inv()
+    for (i in index until end step BLOCK_SIZE) {
         var sum = 0
         var v0 = getInt(i)
         var v1 = getInt(i + 4)
@@ -27,7 +30,8 @@ fun ByteBuf.xteaEncrypt(index: Int, length: Int, key: IntArray) {
 fun ByteBuf.xteaDecrypt(index: Int, length: Int, key: IntArray) {
     require(key.size == 4)
 
-    for (i in index until index + length step 8) {
+    val end = (index + length) and BLOCK_SIZE_MASK.inv()
+    for (i in index until end step BLOCK_SIZE) {
         @Suppress("INTEGER_OVERFLOW")
         var sum = GOLDEN_RATIO * ROUNDS
         var v0 = getInt(i)

crypto/src/test/java/dev/openrs2/crypto/XteaTest.kt

@@ -15,12 +15,27 @@ object XteaTest {
     }
 
     private val TEST_VECTORS = listOf(
+        // empty
+        TestVector("00000000000000000000000000000000", "", ""),
+
+        // standard single block test vectors
         TestVector("000102030405060708090a0b0c0d0e0f", "4142434445464748", "497df3d072612cb5"),
         TestVector("000102030405060708090a0b0c0d0e0f", "4141414141414141", "e78f2d13744341d8"),
         TestVector("000102030405060708090a0b0c0d0e0f", "5a5b6e278948d77f", "4141414141414141"),
         TestVector("00000000000000000000000000000000", "4142434445464748", "a0390589f8b8efa5"),
         TestVector("00000000000000000000000000000000", "4141414141414141", "ed23375a821a8c2d"),
-        TestVector("00000000000000000000000000000000", "70e1225d6e4e7655", "4141414141414141")
+        TestVector("00000000000000000000000000000000", "70e1225d6e4e7655", "4141414141414141"),
+
+        // two blocks
+        TestVector("00000000000000000000000000000000", "70e1225d6e4e76554141414141414141",
+            "4141414141414141ed23375a821a8c2d"),
+
+        // not a multiple of the block size
+        TestVector("00000000000000000000000000000000", "01", "01"),
+        TestVector("00000000000000000000000000000000", "01020304050607", "01020304050607"),
+        TestVector("00000000000000000000000000000000", "70e1225d6e4e765501", "414141414141414101"),
+        TestVector("00000000000000000000000000000000", "70e1225d6e4e765501020304050607",
+            "414141414141414101020304050607")
     )
 
     @Test