first commit

stego-client/decode.go

@@ -0,0 +1,129 @@
+package main
+
+import (
+	"bufio"
+	"crypto/aes"
+	"crypto/cipher"
+	"encoding/base64"
+	"fmt"
+	"image"
+	"log"
+	"os"
+
+	"github.com/auyer/steganography"
+	"github.com/chai2010/webp"
+	"gopkg.in/yaml.v3"
+)
+
+type DecodeConfig struct {
+	Security struct {
+		AESKey string `yaml:"aes_key"` // Base64 encoded 32-byte key
+	} `yaml:"security"`
+}
+
+var (
+	aesKey []byte
+	cfg    DecodeConfig
+)
+
+func loadDecodeConfig(filename string) error {
+	data, err := os.ReadFile(filename)
+	if err != nil {
+		return fmt.Errorf("config file read error: %w", err)
+	}
+
+	if err := yaml.Unmarshal(data, &cfg); err != nil {
+		return fmt.Errorf("config parse error: %w", err)
+	}
+	return nil
+}
+
+func decryptData(ciphertext []byte) ([]byte, error) {
+	block, err := aes.NewCipher(aesKey)
+	if err != nil {
+		return nil, err
+	}
+
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return nil, err
+	}
+
+	nonceSize := gcm.NonceSize()
+	if len(ciphertext) < nonceSize {
+		return nil, fmt.Errorf("ciphertext too short")
+	}
+
+	nonce, ciphertext := ciphertext[:nonceSize], ciphertext[nonceSize:]
+	return gcm.Open(nil, nonce, ciphertext, nil)
+}
+
+func decodeImage(file *os.File) (image.Image, error) {
+	reader := bufio.NewReader(file)
+
+	// Try to decode with image.Decode first
+	img, _, err := image.Decode(reader)
+	if err == nil {
+		return img, nil
+	}
+
+	// Try fallback: WebP
+	// Reset file offset to 0
+	_, _ = file.Seek(0, 0)
+	img, err = webp.Decode(file)
+	if err != nil {
+		return nil, fmt.Errorf("unsupported image format or decode failure: %w", err)
+	}
+	return img, nil
+}
+
+func main() {
+	if len(os.Args) < 2 {
+		fmt.Println("Usage: go run decode.go <encoded_image>")
+		return
+	}
+
+	if err := loadDecodeConfig("config.yaml"); err != nil {
+		log.Fatalf("Failed to load config: %v", err)
+	}
+
+	filePath := os.Args[1]
+
+	inFile, err := os.Open(filePath)
+	if err != nil {
+		fmt.Printf("Failed to open file: %v\n", err)
+		return
+	}
+	defer inFile.Close()
+
+	// Initialize AES key
+	if cfg.Security.AESKey != "" {
+		aesKey, err = base64.StdEncoding.DecodeString(cfg.Security.AESKey)
+		if err != nil {
+			log.Fatalf("Invalid AES key in config: %v", err)
+		}
+	} else {
+		log.Fatal("AES key not provided in config.")
+	}
+
+	img, err := decodeImage(inFile)
+	if err != nil {
+		fmt.Printf("Failed to decode image: %v\n", err)
+		return
+	}
+
+	size := steganography.GetMessageSizeFromImage(img)
+	message := steganography.Decode(size, img)
+	if message == nil {
+		fmt.Println("No message found in the image.")
+		return
+	}
+
+	decryptedMessage, err := decryptData(message)
+	if err != nil {
+		fmt.Printf("Failed to decrypt message: %v\n", err)
+		return
+	}
+
+	fmt.Printf("Decrypted message: %s\n", decryptedMessage)
+}