Implement AES256+GCM encryption/decryption (cascading)

example.go

@@ -16,6 +16,19 @@ import (
 // rcw enc <text> <passwd> : Encrypts the provided text and outputs the ciphertext to encrypted-example.txt
 // rcw dec <passwd> : Decrypts the provided file and outputs the plaintext to stdout
 
+// TODO Tests:
+// Salt (aes+chacha)
+// Nonce (aes+chacha)
+// Encryption (individual+combined)
+// Decryption (individual+combined)
+// RPC password sharing
+
+// TODO Enhancements:
+// Keyfile:
+//     Store:
+//         Hash of passphrase (prevent user from losing data by accidentally providing incorrect passphrase during encryption)
+// 		   Order of algorithms (determined randomly at keyfile generation)
+
 func main() {
 	switch len(os.Args) {
 	case 2:
@@ -25,10 +38,12 @@ func main() {
 		// decrypt file
 		encBytes, _ := os.ReadFile("encrypted-example.txt")
 		decBytes := wrappers.DecryptCha(encBytes, []byte(os.Args[2]))
+		decBytes = wrappers.DecryptAES(decBytes, []byte(os.Args[2]))
 		fmt.Println(string(decBytes))
 	case 4:
 		// encrypt data (from cli args)
-		encBytes := wrappers.EncryptCha([]byte(os.Args[2]), []byte(os.Args[3]))
+		encBytes := wrappers.EncryptAES([]byte(os.Args[2]), []byte(os.Args[3]))
+		encBytes = wrappers.EncryptCha(encBytes, []byte(os.Args[3]))
 		os.WriteFile("encrypted-example.txt", encBytes, 0644)
 	default:
 		// request served data

wrappers/aes.go

@@ -0,0 +1,75 @@
+package wrappers
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"fmt"
+	"io"
+)
+
+const (
+	nonceSizeAES = 12 // GCM standard nonce size is 12 bytes
+)
+
+// EncryptAES encrypts data using AES-256-GCM
+func EncryptAES(data []byte, passphrase []byte) []byte {
+	// generate a random salt
+	salt := make([]byte, saltSize)
+	io.ReadFull(rand.Reader, salt)
+
+	// derive key from passphrase using the salt
+	key := deriveKey(passphrase, salt)
+
+	// create AES-256 cipher
+	block, _ := aes.NewCipher(key)
+
+	// create GCM mode
+	aesGCM, _ := cipher.NewGCM(block)
+
+	// generate a random nonce
+	nonce := make([]byte, nonceSizeAES)
+	io.ReadFull(rand.Reader, nonce)
+
+	// encrypt the data
+	ciphertext := aesGCM.Seal(nil, nonce, data, nil)
+
+	// format: salt + nonce + ciphertext
+	result := make([]byte, 0, saltSize+nonceSizeAES+len(ciphertext))
+	result = append(result, salt...)
+	result = append(result, nonce...)
+	result = append(result, ciphertext...)
+
+	return result
+}
+
+// DecryptAES decrypts data using AES-256-GCM
+func DecryptAES(encryptedData []byte, passphrase []byte) []byte {
+	if len(encryptedData) < saltSize+nonceSizeAES {
+		fmt.Println("Encrypted data is too short")
+		return nil
+	}
+
+	// extract salt, nonce, and ciphertext
+	salt := encryptedData[:saltSize]
+	nonce := encryptedData[saltSize : saltSize+nonceSizeAES]
+	ciphertext := encryptedData[saltSize+nonceSizeAES:]
+
+	// derive key from passphrase using the salt
+	key := deriveKey(passphrase, salt)
+
+	// create AES-256 cipher
+	block, _ := aes.NewCipher(key)
+
+	// create GCM mode
+	aesGCM, _ := cipher.NewGCM(block)
+
+	// decrypt the data
+	plaintext, err := aesGCM.Open(nil, nonce, ciphertext, nil)
+	if err != nil {
+		fmt.Printf("Decryption failed (possibly wrong passphrase): %s", err.Error())
+		return nil
+	}
+
+	return plaintext
+}

wrappers/chacha.go

@@ -10,13 +10,12 @@ import (
 
 const (
 	nonceSizeCha = chacha20poly1305.NonceSizeX
-	saltSizeCha  = 16
 )
 
 // EncryptCha encrypts data using ChaCha20-Poly1305
 func EncryptCha(data []byte, passphrase []byte) []byte {
 	// generate a random salt
-	salt := make([]byte, saltSizeCha)
+	salt := make([]byte, saltSize)
 	io.ReadFull(rand.Reader, salt)
 
 	// derive key from passphrase using the salt
@@ -24,17 +23,17 @@ func EncryptCha(data []byte, passphrase []byte) []byte {
 	key := deriveKey(passphrase, salt)
 
 	// create ChaCha20-Poly1305 cipher
-	aead, _ := chacha20poly1305.NewX(key)
+	stream, _ := chacha20poly1305.NewX(key)
 
 	// generate a random nonce
 	nonce := make([]byte, nonceSizeCha)
 	io.ReadFull(rand.Reader, nonce)
 
 	// encrypt the data
-	ciphertext := aead.Seal(nil, nonce, data, nil)
+	ciphertext := stream.Seal(nil, nonce, data, nil)
 
 	// format: salt + nonce + ciphertext
-	result := make([]byte, 0, saltSizeCha+nonceSizeCha+len(ciphertext))
+	result := make([]byte, 0, saltSize+nonceSizeCha+len(ciphertext))
 	result = append(result, salt...)
 	result = append(result, nonce...)
 	result = append(result, ciphertext...)
@@ -44,24 +43,24 @@ func EncryptCha(data []byte, passphrase []byte) []byte {
 
 // DecryptCha decrypts data using ChaCha20-Poly1305
 func DecryptCha(encryptedData []byte, passphrase []byte) []byte {
-	if len(encryptedData) < saltSizeCha+nonceSizeCha {
+	if len(encryptedData) < saltSize+nonceSizeCha {
 		fmt.Println("Encrypted data is too short")
 		return nil
 	}
 
 	// extract salt, nonce, and ciphertext
-	salt := encryptedData[:saltSizeCha]
-	nonce := encryptedData[saltSizeCha : saltSizeCha+nonceSizeCha]
-	ciphertext := encryptedData[saltSizeCha+nonceSizeCha:]
+	salt := encryptedData[:saltSize]
+	nonce := encryptedData[saltSize : saltSize+nonceSizeCha]
+	ciphertext := encryptedData[saltSize+nonceSizeCha:]
 
 	// derive key from passphrase using the salt
 	key := deriveKey(passphrase, salt)
 
 	// create ChaCha20-Poly1305 cipher
-	aead, _ := chacha20poly1305.NewX(key)
+	stream, _ := chacha20poly1305.NewX(key)
 
 	// decrypt the data
-	plaintext, err := aead.Open(nil, nonce, ciphertext, nil)
+	plaintext, err := stream.Open(nil, nonce, ciphertext, nil)
 	if err != nil {
 		fmt.Printf("Decryption failed (possibly wrong passphrase): %s", err.Error())
 		return nil

wrappers/keyDeriv.go

@@ -11,6 +11,7 @@ const (
 	argonMemory  = 64 * 1024
 	argonThreads = 4
 	argonKeyLen  = chacha20poly1305.KeySize
+	saltSize     = 16
 )
 
 // DeriveKey derives an encryption key from a passphrase using Argon2.