major architecture refactor

internal/security/security.go

@@ -0,0 +1,98 @@
+package security
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"io"
+
+	"golang.org/x/crypto/scrypt"
+)
+
+const (
+	scryptN      = 32768
+	scryptR      = 8
+	scryptP      = 1
+	scryptKeyLen = 32
+)
+
+// Encrypt takes a plain text string and a password, returning a base64 encoded string
+// containing the salt, nonce, and ciphertext.
+func Encrypt(plainText, password string) (string, error) {
+	salt := make([]byte, 16)
+	if _, err := io.ReadFull(rand.Reader, salt); err != nil {
+		return "", fmt.Errorf("failed to generate salt: %w", err)
+	}
+
+	key, err := scrypt.Key([]byte(password), salt, scryptN, scryptR, scryptP, scryptKeyLen)
+	if err != nil {
+		return "", fmt.Errorf("failed to derive key: %w", err)
+	}
+
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return "", fmt.Errorf("failed to create cipher: %w", err)
+	}
+
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return "", fmt.Errorf("failed to create GCM: %w", err)
+	}
+
+	nonce := make([]byte, gcm.NonceSize())
+	if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
+		return "", fmt.Errorf("failed to generate nonce: %w", err)
+	}
+
+	cipherText := gcm.Seal(nonce, nonce, []byte(plainText), nil)
+
+	combined := append(salt, cipherText...)
+	return base64.StdEncoding.EncodeToString(combined), nil
+}
+
+// Decrypt takes the base64 encoded string and password, returning the plain text.
+func Decrypt(encodedData, password string) (string, error) {
+	data, err := base64.StdEncoding.DecodeString(encodedData)
+	if err != nil {
+		return "", fmt.Errorf("failed to decode base64: %w", err)
+	}
+
+	if len(data) < 16+12 { // 16 salt + 12 nonce (min)
+		return "", errors.New("invalid data length")
+	}
+
+	salt := data[:16]
+	cipherTextWithNonce := data[16:]
+
+	key, err := scrypt.Key([]byte(password), salt, scryptN, scryptR, scryptP, scryptKeyLen)
+	if err != nil {
+		return "", fmt.Errorf("failed to derive key: %w", err)
+	}
+
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return "", fmt.Errorf("failed to create cipher: %w", err)
+	}
+
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return "", fmt.Errorf("failed to create GCM: %w", err)
+	}
+
+	nonceSize := gcm.NonceSize()
+	if len(cipherTextWithNonce) < nonceSize {
+		return "", errors.New("ciphertext too short")
+	}
+
+	nonce, actualCipherText := cipherTextWithNonce[:nonceSize], cipherTextWithNonce[nonceSize:]
+
+	plainText, err := gcm.Open(nil, nonce, actualCipherText, nil)
+	if err != nil {
+		return "", errors.New("invalid password or corrupted data")
+	}
+
+	return string(plainText), nil
+}