1 files changed, 126 insertions, 0 deletions
diff --git a/ecookie.go b/ecookie.go
new file mode 100644
index 0000000..767091e
--- /dev/null
+++ b/ecookie.go
@@ -0,0 +1,126 @@
+package ecookie
+
+import (
+	"bytes"
+	"crypto/rand"
+	"encoding/hex"
+	"errors"
+	"io"
+
+	"golang.org/x/crypto/blake2b"
+	"snix.ir/rabbitio"
+)
+
+var (
+	ErrAUTHCOK = errors.New("ecookie: cookie is corrupted")
+	ErrENDDATA = errors.New("ecookie: cookie length is too short")
+	ErrNotVlid = errors.New("ecookie: data is not validated")
+
+	ErrBadKlen = errors.New("ecookie: key must be 16 byte len")
+)
+
+const (
+	lenhashfnc = 32
+	lenkrabbit = 16
+	lenivahash = lenhashfnc + lenivforkt
+	lenivforkt = 8
+)
+
+type Encryptor struct {
+	key []byte
+}
+
+type Decryptor struct {
+	key []byte
+}
+
+func NewEncryptor(key []byte) (*Encryptor, error) {
+	if len(key) != lenkrabbit {
+		return nil, ErrBadKlen
+	}
+	copyKey := make([]byte, lenkrabbit)
+	copy(copyKey, key)
+	return &Encryptor{key: copyKey}, nil
+}
+
+func NewDecryptor(key []byte) (*Decryptor, error) {
+	if len(key) != lenkrabbit {
+		return nil, ErrBadKlen
+	}
+	copyKey := make([]byte, lenkrabbit)
+	copy(copyKey, key)
+	return &Decryptor{key: copyKey}, nil
+}
+
+func randomIVGen() ([]byte, error) {
+	iv := make([]byte, lenivforkt)
+	if _, err := rand.Read(iv); err != nil {
+		return nil, err
+	}
+	return iv, nil
+}
+
+func (h *Encryptor) Encrypt(src []byte) ([]byte, error) {
+	ivx, err := randomIVGen()
+	if err != nil {
+		return nil, err
+	}
+
+	cip, _ := rabbitio.NewCipher(h.key, ivx)
+	dst := make([]byte, len(src))
+	cip.XORKeyStream(dst, src)
+	hash, err := blake2bHash(multiReader(h.key, ivx, dst))
+	if err != nil {
+		return nil, err
+	}
+
+	buff := new(bytes.Buffer)
+	_, err = io.Copy(hex.NewEncoder(buff), multiReader(hash, ivx, dst))
+	return buff.Bytes(), err
+}
+
+func multiReader(vs ...[]byte) io.Reader {
+
+	var rds []io.Reader
+	for _, x := range vs {
+		r := bytes.NewReader(x)
+		rds = append(rds, r)
+	}
+
+	return io.MultiReader(rds...)
+}
+
+func blake2bHash(r io.Reader) ([]byte, error) {
+	hasher, _ := blake2b.New256(nil)
+	if _, err := io.Copy(hasher, r); err != nil {
+		return nil, err
+	}
+	return hasher.Sum(nil), nil
+}
+
+func (h *Decryptor) Decrypt(raw []byte) ([]byte, error) {
+	bf := new(bytes.Buffer)
+	if _, err := io.Copy(bf,
+		hex.NewDecoder(bytes.NewReader(raw))); err != nil {
+		return nil, err
+	}
+
+	if bf.Len() < lenivahash {
+		return nil, ErrENDDATA
+	}
+
+	u := bf.Bytes()
+	cl, err := blake2bHash(multiReader(h.key, u[lenhashfnc:]))
+	if err != nil {
+		return nil, err
+	}
+
+	if !bytes.Equal(cl, u[:lenhashfnc]) {
+		return nil, ErrAUTHCOK
+	}
+
+	cip, _ := rabbitio.NewCipher(h.key, u[lenhashfnc:lenivahash])
+	pln := make([]byte, bf.Len()-lenivahash)
+	cip.XORKeyStream(pln, u[lenivahash:])
+	return pln, err
+}