Improve CFB8 implementation (#256)

* Add CFB8 tests & benchmark

* Improve CFB8 implementation

* Cleanup code

* Speed up with copy function

* Even faster

* Fix & more tests

* Fix tests

* Fix typo

net/CFB8/cfb8_test.go

@@ -0,0 +1,186 @@
+package CFB8
+
+import (
+	"bytes"
+	"crypto/aes"
+	"crypto/rand"
+	"encoding/hex"
+	"testing"
+)
+
+// cfb8Tests contains the test vectors from
+// https://csrc.nist.gov/publications/nistpubs/800-38a/sp800-38a.pdf, section
+// F.3.7. Modified for Minecraft CFB8 tests.
+var cfb8Tests = []struct {
+	key, iv, plaintext, ciphertext string
+}{
+	{
+		"2b7e151628aed2a6abf7158809cf4f3c",
+		"000102030405060708090a0b0c0d0e0f",
+		"6bc1bee22e409f96e93d7e117393172a",
+		"3b79424c9c0dd436bace9e0ed4586a4f",
+	},
+	{
+		"2b7e151628aed2a6abf7158809cf4f3c",
+		"3B3FD92EB72DAD20333449F8E83CFB4A",
+		"ae2d8a571e03ac9c9eb76fac45af8e51",
+		"c8b0723943d71f61a2e5b0e8cedf87c8",
+	},
+	{
+		"2b7e151628aed2a6abf7158809cf4f3c",
+		"C8A64537A0B3A93FCDE3CDAD9F1CE58B",
+		"30c81c46a35ce411e5fbc1191a0a52ef",
+		"260d20e9395d3501067286d3a2a7002f",
+	},
+	{
+		"2b7e151628aed2a6abf7158809cf4f3c",
+		"26751F67A3CBB140B1808CF187A4F4DF",
+		"f69f2445df4f9b17ad2b417be66c3710",
+		"c0af633cd9c599309f924802af599ee6",
+	},
+	{
+		"2b7e151628aed2a6abf7158809cf4f3c",
+		"000102030405060708090a0b0c0d0e0f",
+		"0ecbd6d36cd12962ce671b4d96fb95aaa902096aeac366e13a6ae57c05d48673cf320c626689d05548f65fd6a108630c1d4e3aab543b006823c7a9422e97c0431587537c384f99a11488ffd9b2e9b46f49005a7e5cef64e27e2de3cf3fb87c1524766601",
+		"5efb6f6b93cf5f0e135a0c932f59f9aaa2276e4b06cd4f5edca4baba735ac7708dd7c0f9e92c6b89d2245b0d9a6356b0e98529cd45e56df22e914ef9e0792facaab707af90c13162bfad06a240eb6adcbf3365fd84a003f8083f4662a7a27232c72c6c0c",
+	},
+}
+
+func TestCFB8VectorsNonOverlapping(t *testing.T) {
+	for i, test := range cfb8Tests {
+		key, err := hex.DecodeString(test.key)
+		if err != nil {
+			t.Fatal(err)
+		}
+		iv, err := hex.DecodeString(test.iv)
+		if err != nil {
+			t.Fatal(err)
+		}
+		plaintext, err := hex.DecodeString(test.plaintext)
+		if err != nil {
+			t.Fatal(err)
+		}
+		expected, err := hex.DecodeString(test.ciphertext)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		block, err := aes.NewCipher(key)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		ciphertext := make([]byte, len(plaintext))
+		cfb := NewCFB8Encrypt(block, iv)
+		if len(plaintext) > 50 {
+			cfb.XORKeyStream(ciphertext, plaintext[:len(plaintext)/2])
+			cfb.XORKeyStream(ciphertext[len(plaintext)/2:], plaintext[len(plaintext)/2:])
+		} else {
+			cfb.XORKeyStream(ciphertext, plaintext)
+		}
+
+		if !bytes.Equal(ciphertext, expected) {
+			t.Errorf("#%d: wrong output: got %x, expected %x", i, ciphertext, expected)
+		}
+
+		cfbdec := NewCFB8Decrypt(block, iv)
+		plaintextCopy := make([]byte, len(ciphertext))
+		if len(ciphertext) > 50 {
+			cfbdec.XORKeyStream(plaintextCopy, ciphertext[:len(ciphertext)/2])
+			cfbdec.XORKeyStream(plaintextCopy[len(ciphertext)/2:], ciphertext[len(ciphertext)/2:])
+		} else {
+			cfbdec.XORKeyStream(plaintextCopy, ciphertext)
+		}
+
+		if !bytes.Equal(plaintextCopy, plaintext) {
+			t.Errorf("#%d: wrong plaintext: got %x, expected %x", i, plaintextCopy, plaintext)
+		}
+	}
+}
+
+func TestCFB8VectorsOverlapped(t *testing.T) {
+	for i, test := range cfb8Tests {
+		key, err := hex.DecodeString(test.key)
+		if err != nil {
+			t.Fatal(err)
+		}
+		iv, err := hex.DecodeString(test.iv)
+		if err != nil {
+			t.Fatal(err)
+		}
+		plaintext, err := hex.DecodeString(test.plaintext)
+		if err != nil {
+			t.Fatal(err)
+		}
+		expected, err := hex.DecodeString(test.ciphertext)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		block, err := aes.NewCipher(key)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		buf := make([]byte, len(plaintext))
+		copy(buf, plaintext)
+		cfb := NewCFB8Encrypt(block, iv)
+		if len(buf) > 50 {
+			cfb.XORKeyStream(buf, buf[:len(buf)/2])
+			cfb.XORKeyStream(buf[len(buf)/2:], buf[len(buf)/2:])
+		} else {
+			cfb.XORKeyStream(buf, buf)
+		}
+
+		if !bytes.Equal(buf, expected) {
+			t.Errorf("#%d: wrong output: got %x, expected %x", i, buf, expected)
+		}
+
+		cfbdec := NewCFB8Decrypt(block, iv)
+		if len(buf) > 50 {
+			cfbdec.XORKeyStream(buf, buf[:len(buf)/2])
+			cfbdec.XORKeyStream(buf[len(buf)/2:], buf[len(buf)/2:])
+		} else {
+			cfbdec.XORKeyStream(buf, buf)
+		}
+
+		if !bytes.Equal(buf, plaintext) {
+			t.Errorf("#%d: wrong plaintext: got %x, expected %x", i, buf, plaintext)
+		}
+	}
+}
+
+func BenchmarkCFB8AES1KOverlapped(b *testing.B) {
+	var key [16]byte
+	var iv [16]byte
+	rand.Read(key[:])
+	rand.Read(iv[:])
+	buf := make([]byte, 1024)
+	aes, _ := aes.NewCipher(key[:])
+	stream := NewCFB8Encrypt(aes, iv[:])
+
+	b.SetBytes(int64(len(buf)))
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		stream.XORKeyStream(buf, buf)
+	}
+}
+
+func BenchmarkCFB8AES1KNonOverlapping(b *testing.B) {
+	var key [16]byte
+	var iv [16]byte
+	rand.Read(key[:])
+	rand.Read(iv[:])
+	buf := make([]byte, 1024)
+	buf2 := make([]byte, 1024)
+	aes, _ := aes.NewCipher(key[:])
+	stream := NewCFB8Encrypt(aes, iv[:])
+
+	b.SetBytes(int64(len(buf)))
+	b.ReportAllocs()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		stream.XORKeyStream(buf2, buf)
+	}
+}