init: v1.0.0

utils/blockmode/ctr.go

@@ -0,0 +1,149 @@
+package blockmode
+
+import (
+	"fmt"
+
+	"xdx.jelly/xgcl/gerrors"
+	"xdx.jelly/xgcl/internal/subtle"
+	"xdx.jelly/xgcl/internal/xor"
+)
+
+// Counter (CTR) mode.
+
+// CTR converts a block cipher into a stream cipher by
+// repeatedly encrypting an incrementing counter and
+// xoring the resulting stream of data with the input.
+
+// See NIST SP 800-38A, pp 13-15
+
+type ctr struct {
+	b       EcbBlockMode
+	ctr     []byte //counter
+	out     []byte // out[outUsed:] is the unused encrypted counters.
+	outUsed int
+}
+
+const streamBufferSize = 4096
+
+// ctrAble is an interface implemented by ciphers that have a specific optimized
+// implementation of CTR, like crypto/aes. NewCTR will check for this interface
+// and return the specific Stream if found.
+type ctrAble interface {
+	NewCTR(iv []byte) (TernaryStream, error)
+}
+
+// NewCTR returns a Stream which encrypts/decrypts using the given Block in
+// counter mode. The length of iv must be the same as the Block's block size.
+func NewCTR(block EcbBlockMode, iv []byte) (TernaryStream, error) {
+	if ctr, ok := block.(ctrAble); ok {
+		return ctr.NewCTR(iv)
+	}
+	if len(iv) != block.BlockSize() {
+		return nil, gerrors.WithAnnotatingf(ErrInvalidIV, "input IV length(%d) must be %d bytes", len(iv), block.BlockSize())
+	}
+	bufSize := streamBufferSize
+	if bufSize < block.BlockSize() {
+		bufSize = block.BlockSize()
+	}
+	return &ctr{
+		b:       block,
+		ctr:     dup(iv),
+		out:     make([]byte, 0, bufSize),
+		outUsed: 0,
+	}, nil
+}
+
+func (x *ctr) reset(iv []byte) error {
+	if len(iv) != x.b.BlockSize() {
+		return gerrors.WithAnnotatingf(ErrInvalidIV, "input IV length(%d) must be %d bytes", len(iv), x.b.BlockSize())
+	}
+	copy(x.ctr, iv)
+	x.out = x.out[:0]
+	x.outUsed = 0
+	return nil
+}
+
+// refill 填充x.out.
+func (x *ctr) refill() {
+	begin := len(x.out) - x.outUsed
+	copy(x.out, x.out[x.outUsed:])
+	x.out = x.out[:cap(x.out)]
+	bs := x.b.BlockSize()
+	end := begin
+	for end <= len(x.out)-bs {
+		copy(x.out[end:], x.ctr)
+		end += bs
+		for i := len(x.ctr) - 1; i >= 0; i-- {
+			x.ctr[i]++
+			if x.ctr[i] != 0 {
+				break
+			}
+		}
+	}
+	_ = x.b.EcbEncCryptBlocks(x.out[begin:end], x.out[begin:end])
+	x.out = x.out[:end]
+	x.outUsed = 0
+}
+
+func (x *ctr) XORKeyStream(dst, src []byte) {
+	if len(dst) < len(src) {
+		// By definition of cipher.Stream, if len(dst) < len(src), XORKeyStream should panic.
+		panic(fmt.Sprintf("length of output buf(%d) less than the input(%d)", len(dst), len(src)))
+	}
+	if subtle.InexactOverlap(dst[:len(src)], src) {
+		panic("ctr.XORKeyStream: dst must be exact overlap with src or non-overlap with src")
+	}
+	for len(src) > 0 {
+		if x.outUsed >= len(x.out)-x.b.BlockSize() {
+			x.refill()
+		}
+		n := xor.XorBytes(dst, src, x.out[x.outUsed:])
+		dst = dst[n:]
+		src = src[n:]
+		x.outUsed += n
+	}
+}
+
+var _ TernaryStream = &ctr{}
+
+// EncryptInit implements TernaryStream
+func (x *ctr) EncryptInit(iv []byte) error {
+	return x.reset(iv)
+}
+
+// Encrypt implements TernaryStream
+func (x *ctr) Encrypt(dst []byte, in []byte) ([]byte, error) {
+	ret, out := sliceForAppend(dst, len(in))
+	x.XORKeyStream(out, in)
+	return ret, nil
+}
+
+// EncryptFinal implements TernaryStream
+func (x *ctr) EncryptFinal(dst []byte) ([]byte, error) {
+	return dst, nil
+}
+
+// EncryptUpdate implements TernaryStream
+func (x *ctr) EncryptUpdate(dst []byte, in []byte) ([]byte, error) {
+	return x.Encrypt(dst, in)
+}
+
+// Decrypt implements TernaryStream
+func (x *ctr) Decrypt(dst []byte, in []byte) ([]byte, error) {
+	return x.Encrypt(dst, in)
+}
+
+// DecryptFinal implements TernaryStream
+func (x *ctr) DecryptFinal(dst []byte) ([]byte, error) {
+	return dst, nil
+}
+
+// DecryptInit implements TernaryStream
+func (x *ctr) DecryptInit(iv []byte) error {
+	return x.reset(iv)
+}
+
+// DecryptUpdate implements TernaryStream
+func (x *ctr) DecryptUpdate(dst []byte, in []byte) ([]byte, error) {
+	return x.Encrypt(dst, in)
+}