Don't increment nonces within a CipherState unless the encryption/decryption operation succeeds

src/main/java/com/southernstorm/noise/protocol/AESGCMFallbackCipherState.java

@@ -130,8 +130,7 @@ class AESGCMFallbackCipherState implements CipherState {
 		iv[13] = 0;
 		iv[14] = 0;
 		iv[15] = 1;
-		++n;
-		
+
 		// Encrypt a block of zeroes to generate the hash key to XOR
 		// the GHASH tag with at the end of the encrypt/decrypt operation.
 		Arrays.fill(hashKey, (byte)0);
@@ -207,6 +206,7 @@ class AESGCMFallbackCipherState implements CipherState {
 		ghash.finish(ciphertext, ciphertextOffset + length, 16);
 		for (int index = 0; index < 16; ++index)
 			ciphertext[ciphertextOffset + length + index] ^= hashKey[index];
+		n += 1;
 		return length + 16;
 	}
 
@@ -247,6 +247,7 @@ class AESGCMFallbackCipherState implements CipherState {
 		if ((temp & 0xFF) != 0)
 			Noise.throwBadTagException();
 		encryptCTR(ciphertext, ciphertextOffset, plaintext, plaintextOffset, dataLen);
+		n += 1;
 		return dataLen;
 	}
 

src/main/java/com/southernstorm/noise/protocol/AESGCMOnCtrCipherState.java

@@ -190,8 +190,7 @@ class AESGCMOnCtrCipherState implements CipherState {
 		iv[13] = 0;
 		iv[14] = 0;
 		iv[15] = 1;
-		++n;
-		
+
 		// Initialize the CTR mode cipher with the key and IV.
 		cipher.init(Cipher.ENCRYPT_MODE, keySpec, new IvParameterSpec(iv));
 		
@@ -255,6 +254,7 @@ class AESGCMOnCtrCipherState implements CipherState {
 		ghash.finish(ciphertext, ciphertextOffset + length, 16);
 		for (int index = 0; index < 16; ++index)
 			ciphertext[ciphertextOffset + length + index] ^= hashKey[index];
+		n += 1;
 		return length + 16;
 	}
 
@@ -312,6 +312,7 @@ class AESGCMOnCtrCipherState implements CipherState {
 			// Shouldn't happen.
 			throw new IllegalStateException(e);
 		}
+		n += 1;
 		return dataLen;
 	}
 

src/main/java/com/southernstorm/noise/protocol/ChaChaPolyCipherState.java

@@ -138,7 +138,7 @@ class ChaChaPolyCipherState implements CipherState {
 	{
 		if (n == -1L)
 			throw new IllegalStateException("Nonce has wrapped around");
-		ChaChaCore.initIV(input, n++);
+		ChaChaCore.initIV(input, n);
 		ChaChaCore.hash(output, input);
 		Arrays.fill(polyKey, (byte)0);
 		xorBlock(polyKey, 0, polyKey, 0, 32, output);
@@ -234,6 +234,7 @@ class ChaChaPolyCipherState implements CipherState {
 		poly.update(ciphertext, ciphertextOffset, length);
 		finish(ad, length);
 		System.arraycopy(polyKey, 0, ciphertext, ciphertextOffset + length, 16);
+		n += 1;
 		return length + 16;
 	}
 
@@ -273,6 +274,7 @@ class ChaChaPolyCipherState implements CipherState {
 		if ((temp & 0xFF) != 0)
 			Noise.throwBadTagException();
 		encrypt(ciphertext, ciphertextOffset, plaintext, plaintextOffset, dataLen);
+		n += 1;
 		return dataLen;
 	}
 

src/test/java/com/southernstorm/noise/tests/CipherStateTests.java

@@ -149,10 +149,11 @@ public class CipherStateTests {
 			fail();
 		}
 
-	    // Fast-forward the nonce to just before the rollover.  We will be able
-	    // to decrypt one more block, and then the next request will be rejected.
-		cipher.setNonce(-2L);
 		try {
+			// Fast-forward the nonce to just before the rollover.  We will be able
+			// to decrypt one more block, and then the next request will be rejected.
+			cipher.setNonce(-2L);
+
 			buffer = new byte [plaintextBytes.length];
 			Arrays.fill(buffer, (byte)0xAA);
 			try {
@@ -161,6 +162,9 @@ public class CipherStateTests {
 			} catch (BadPaddingException e) {
 				// Success!
 			}
+
+			cipher.setNonce(-1L);
+
 			try {
 				cipher.decryptWithAd(adBytes, ciphertextBytes, 0, buffer, 0, ciphertextBytes.length);
 				fail();