monorepo fixes

crypto/auth_digest.go

@@ -0,0 +1,40 @@
+package crypto
+
+import (
+	"crypto/sha1"
+	"encoding/hex"
+	"strings"
+)
+
+func twosComplement(p []byte) []byte {
+	carry := true
+	for i := len(p) - 1; i >= 0; i-- {
+		p[i] = byte(^p[i])
+		if carry {
+			carry = p[i] == 0xff
+			p[i]++
+		}
+	}
+	return p
+}
+
+// AuthDigest stolen from https://gist.github.com/toqueteos/5372776
+func AuthDigest(elems ...[]byte) string {
+	h := sha1.New()
+	for _, elem := range elems {
+		h.Write(elem)
+	}
+	hash := h.Sum(nil)
+
+	negative := (hash[0] & 0x80) == 0x80
+	if negative {
+		hash = twosComplement(hash)
+	}
+
+	res := strings.TrimLeft(hex.EncodeToString(hash), "0")
+	if negative {
+		res = "-" + res
+	}
+
+	return res
+}

crypto/cfb8.go

@@ -0,0 +1,139 @@
+package crypto
+
+// https://github.com/Tnze/go-mc/blob/master/net/CFB8/cfb8.go
+// Package CFB8 implements CFB8 block cipher mode of operation used by Minecraft protocol.
+
+import (
+	"crypto/cipher"
+	"crypto/subtle"
+	"unsafe"
+)
+
+type CFB8 struct {
+	c         cipher.Block
+	blockSize int
+	ivPos     int
+	iv        []byte
+	de        bool
+}
+
+func NewCFB8Decrypt(c cipher.Block, iv []byte) *CFB8 {
+	return newCFB8(c, iv, true)
+}
+
+func NewCFB8Encrypt(c cipher.Block, iv []byte) *CFB8 {
+	return newCFB8(c, iv, false)
+}
+
+func newCFB8(c cipher.Block, iv []byte, de bool) *CFB8 {
+	cp := make([]byte, len(iv)*3)
+	copy(cp, iv)
+	return &CFB8{
+		c:         c,
+		blockSize: c.BlockSize(),
+		iv:        cp,
+		de:        de,
+	}
+}
+
+func (cf *CFB8) XORKeyStream(dst, src []byte) {
+	if len(src) == 0 {
+		return
+	}
+	if len(dst) < len(src) {
+		panic("cfb8: output smaller than input")
+	}
+
+	// If dst and src does not overlap in first block size,
+	// and the length of src is greater than 2*blockSize,
+	// we can use an optimized implementation.
+	if len(src) > cf.blockSize<<1 &&
+		(uintptr(unsafe.Pointer(&dst[0]))+uintptr(cf.blockSize) <= uintptr(unsafe.Pointer(&src[0])) ||
+			uintptr(unsafe.Pointer(&src[0]))+uintptr(len(src)) <= uintptr(unsafe.Pointer(&dst[0]))) {
+		// encrypt/decrypt first blockSize bytes
+		// After this, the IV will come to the same as
+		// the last blockSize of ciphertext, so
+		// we can reuse them without copy.
+		cf.xorKeyStream(dst, src[:cf.blockSize])
+		var ciphertext []byte
+		if cf.de {
+			ciphertext = src
+		} else {
+			ciphertext = dst
+		}
+		dst = dst[cf.blockSize:]
+		src = src[cf.blockSize:]
+		iv := cf.iv
+		_ = iv[0] // bounds check hint to compiler; see golang.org/issue/14808
+		var (
+			i   int
+			val byte
+		)
+		dst = dst[:len(src)]
+		if cf.de && // and requires to be non-overlapping at all
+			uintptr(unsafe.Pointer(&dst[0])) <= uintptr(unsafe.Pointer(&src[len(src)-1])) &&
+			uintptr(unsafe.Pointer(&src[0])) <= uintptr(unsafe.Pointer(&dst[len(dst)-1])) {
+			for i = 0; i < len(src)-cf.blockSize; i += 1 {
+				cf.c.Encrypt(dst[i:], ciphertext[i:])
+			}
+			subtle.XORBytes(dst, src[:i], dst)
+			for ; i < len(src); i += 1 {
+				cf.c.Encrypt(iv, ciphertext[i:])
+				dst[i] = src[i] ^ iv[0]
+			}
+		} else {
+			_ = ciphertext[len(src)]
+			for i, val = range src {
+				cf.c.Encrypt(iv, ciphertext[i:])
+				dst[i] = val ^ iv[0]
+			}
+			// for-range does not increase i in the last loop,
+			// compared to the classic for clause
+			i += 1
+		}
+		// copy the current IV for next operation
+		copy(iv, ciphertext[i:i+cf.blockSize])
+		cf.ivPos = 0
+		return
+	}
+
+	cf.xorKeyStream(dst, src)
+}
+
+func (cf *CFB8) xorKeyStream(dst, src []byte) {
+	dst = dst[:len(src)] // remove bounds check in loop
+	for i, val := range src {
+		posPlusBlockSize := cf.ivPos + cf.blockSize
+		// fast mod; 2*blockSize must be a non-negative integer power of 2
+		tempPos := posPlusBlockSize & (cf.blockSize<<1 - 1)
+		// reuse space to store encrypted block
+		cf.c.Encrypt(cf.iv[tempPos:], cf.iv[cf.ivPos:])
+		// Only the first byte of the encrypted block is used
+		// for encryption/decryption, other bytes are ignored.
+		val ^= cf.iv[tempPos]
+
+		if cf.ivPos == cf.blockSize<<1 {
+			// bound reached; move to next round for next operation
+			// copy next block to the start of the ring buffer
+			copy(cf.iv, cf.iv[cf.ivPos+1:])
+			// insert the encrypted byte to the end of IV
+			if cf.de {
+				cf.iv[cf.blockSize-1] = src[i]
+			} else {
+				cf.iv[cf.blockSize-1] = val
+			}
+			cf.ivPos = 0
+		} else {
+			// insert the encrypted byte to the end of IV
+			if cf.de {
+				cf.iv[posPlusBlockSize] = src[i]
+			} else {
+				cf.iv[posPlusBlockSize] = val
+			}
+			// move to next block
+			cf.ivPos += 1
+		}
+
+		dst[i] = val
+	}
+}