add vendoring

vendor/gitlab.com/etke.cc/linkpearl/crypter.go

@@ -0,0 +1,73 @@
+package linkpearl
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"encoding/base64"
+	"errors"
+	"io"
+)
+
+// Crypter is special object that handles data encryption and decryption
+// apart from Matrix' standard encryption.
+// It can encrypt and decrypt arbitrary data using secret key (password)
+type Crypter struct {
+	cipher    cipher.AEAD
+	nonceSize int
+}
+
+// ErrInvalidData returned in provided encrypted data (ciphertext) is invalid
+var ErrInvalidData = errors.New("invalid data")
+
+// NewCrypter creates new Crypter
+func NewCrypter(secretkey string) (*Crypter, error) {
+	block, err := aes.NewCipher([]byte(secretkey))
+	if err != nil {
+		return nil, err
+	}
+
+	aesGCM, err := cipher.NewGCM(block)
+	if err != nil {
+		return nil, err
+	}
+
+	return &Crypter{
+		cipher:    aesGCM,
+		nonceSize: aesGCM.NonceSize(),
+	}, nil
+}
+
+// Decrypt data
+func (c *Crypter) Decrypt(data string) (string, error) {
+	datab, err := base64.StdEncoding.DecodeString(data)
+	if err != nil {
+		return data, err
+	}
+
+	if len(datab) < c.nonceSize {
+		return data, ErrInvalidData
+	}
+
+	nonce := datab[:c.nonceSize]
+	ciphertext := datab[c.nonceSize:]
+
+	plaintext, err := c.cipher.Open(nil, nonce, ciphertext, nil)
+	if err != nil {
+		return data, err
+	}
+
+	return string(plaintext), nil
+}
+
+// Encrypt data
+func (c *Crypter) Encrypt(data string) (string, error) {
+	nonce := make([]byte, c.nonceSize)
+	_, err := io.ReadFull(rand.Reader, nonce)
+	if err != nil {
+		return data, err
+	}
+
+	encrypted := c.cipher.Seal(nonce, nonce, []byte(data), nil)
+	return base64.StdEncoding.EncodeToString(encrypted), nil
+}