1 files changed, 88 insertions, 0 deletions

diff --git a/inform/crypto.go b/inform/crypto.go
new file mode 100644
index 0000000..90118c1
--- /dev/null
+++ b/inform/crypto.go
@@ -0,0 +1,88 @@
+package inform
+
+import (
+        "bytes"
+        "crypto/aes"
+        "crypto/cipher"
+        "crypto/rand"
+        "encoding/hex"
+        "errors"
+)
+
+func Pad(src []byte, blockSize int) []byte {
+        padLen := blockSize - (len(src) % blockSize)
+        padText := bytes.Repeat([]byte{byte(padLen)}, padLen)
+        return append(src, padText...)
+}
+
+func Unpad(src []byte, blockSize int) ([]byte, error) {
+        srcLen := len(src)
+        paddingLen := int(src[srcLen-1])
+        if paddingLen >= srcLen || paddingLen > blockSize {
+                return nil, errors.New("Padding size error")
+        }
+        return src[:srcLen-paddingLen], nil
+}
+
+func decodeHexKey(key string) (cipher.Block, error) {
+        decodedKey, err := hex.DecodeString(key)
+        if err != nil {
+                return nil, err
+        }
+
+        block, err := aes.NewCipher(decodedKey)
+        if err != nil {
+                return nil, err
+        }
+
+        return block, nil
+}
+
+func makeAESIV() ([]byte, error) {
+        iv := make([]byte, 16)
+        if _, err := rand.Read(iv); err != nil {
+                return nil, err
+        }
+        return iv, nil
+}
+
+// Returns ciphertext and IV, does not modify payload
+func Encrypt(payload []byte, key string) ([]byte, []byte, error) {
+        ct := make([]byte, len(payload))
+        copy(ct, payload)
+        ct = Pad(ct, aes.BlockSize)
+
+        iv, err := makeAESIV()
+        if err != nil {
+                return nil, nil, err
+        }
+
+        block, err := decodeHexKey(key)
+        if err != nil {
+                return nil, nil, err
+        }
+
+        mode := cipher.NewCBCEncrypter(block, iv)
+        mode.CryptBlocks(ct, ct)
+
+        return ct, iv, nil
+}
+
+func Decrypt(payload, iv []byte, key string) ([]byte, error) {
+        b := make([]byte, len(payload))
+
+        block, err := decodeHexKey(key)
+        if err != nil {
+                return nil, err
+        }
+
+        mode := cipher.NewCBCDecrypter(block, iv)
+        mode.CryptBlocks(b, payload)
+
+        u, err := Unpad(b, aes.BlockSize)
+        if err != nil {
+                return nil, err
+        }
+
+        return u, nil
+}