[management] Move activity store encryption to shared crypt package (#5111)

util/crypt/legacy.go

@@ -0,0 +1,71 @@
+package crypt
+
+import (
+	"bytes"
+	"crypto/aes"
+	"crypto/cipher"
+	"encoding/base64"
+	"fmt"
+)
+
+// legacyIV is the static IV used by the legacy CBC encryption.
+// Deprecated: This is kept only for backward compatibility with existing encrypted data.
+var legacyIV = []byte{10, 22, 13, 79, 05, 8, 52, 91, 87, 98, 88, 98, 35, 25, 13, 05}
+
+// LegacyEncrypt encrypts plaintext using AES-CBC with a static IV.
+// Deprecated: Use Encrypt instead. This method is kept only for backward compatibility.
+func (f *FieldEncrypt) LegacyEncrypt(plaintext string) string {
+	padded := pkcs5Padding([]byte(plaintext))
+	ciphertext := make([]byte, len(padded))
+	cbc := cipher.NewCBCEncrypter(f.block, legacyIV)
+	cbc.CryptBlocks(ciphertext, padded)
+	return base64.StdEncoding.EncodeToString(ciphertext)
+}
+
+// LegacyDecrypt decrypts ciphertext that was encrypted using AES-CBC with a static IV.
+// Deprecated: This method is kept only for backward compatibility with existing encrypted data.
+func (f *FieldEncrypt) LegacyDecrypt(ciphertext string) (string, error) {
+	data, err := base64.StdEncoding.DecodeString(ciphertext)
+	if err != nil {
+		return "", fmt.Errorf("decode ciphertext: %w", err)
+	}
+
+	cbc := cipher.NewCBCDecrypter(f.block, legacyIV)
+	cbc.CryptBlocks(data, data)
+
+	plaintext, err := pkcs5UnPadding(data)
+	if err != nil {
+		return "", fmt.Errorf("unpad plaintext: %w", err)
+	}
+
+	return string(plaintext), nil
+}
+
+// pkcs5Padding adds PKCS#5 padding to the input.
+func pkcs5Padding(data []byte) []byte {
+	padding := aes.BlockSize - len(data)%aes.BlockSize
+	padText := bytes.Repeat([]byte{byte(padding)}, padding)
+	return append(data, padText...)
+}
+
+// pkcs5UnPadding removes PKCS#5 padding from the input.
+func pkcs5UnPadding(data []byte) ([]byte, error) {
+	length := len(data)
+	if length == 0 {
+		return nil, fmt.Errorf("input data is empty")
+	}
+
+	paddingLen := int(data[length-1])
+	if paddingLen == 0 || paddingLen > aes.BlockSize || paddingLen > length {
+		return nil, fmt.Errorf("invalid padding size")
+	}
+
+	// Verify that all padding bytes are the same
+	for i := 0; i < paddingLen; i++ {
+		if data[length-1-i] != byte(paddingLen) {
+			return nil, fmt.Errorf("invalid padding")
+		}
+	}
+
+	return data[:length-paddingLen], nil
+}