added a stricter linter configuration (#37)

.golangci.yml

@@ -0,0 +1,37 @@
+run:
+  go: "1.19"
+
+linters:
+  enable-all: true
+
+  disable:
+    # deprecated
+    - maligned
+    - scopelint
+    - varcheck
+    - interfacer
+    - structcheck
+    - nosnakecase
+    - deadcode
+    - exhaustivestruct
+    - ifshort
+    - golint
+
+    # warn for generics: https://github.com/golangci/golangci-lint/issues/2649
+    - rowserrcheck
+    - sqlclosecheck
+    - wastedassign
+
+    # others
+    - forbidigo
+
+    # to evaluate
+    - wrapcheck
+    - varnamelen
+    - noctx
+    - gomnd
+    - gochecknoglobals
+    - exhaustruct
+    - godox
+    - paralleltest
+    - testpackage

cmd/stego/stego.go

@@ -8,7 +8,6 @@ import (
 )
 
 func main() {
-	fmt.Print()
 	if err := cli.NewRootCmd().Execute(); err != nil {
 		fmt.Println(err)
 		os.Exit(1)

internal/cli/images.go

@@ -35,14 +35,17 @@ func newImagesCmd() *cobra.Command {
 	return imagesCmd
 }
 
-var client = http.Client{Timeout: 30 * time.Second}
+var (
+	client                = http.Client{Timeout: 30 * time.Second}
+	errInvalidNumOfImages = errors.New("number of images must be at least 1")
+)
 
 func runImagesCmd(cmd *cobra.Command, args []string) error {
 	if imagesNum == 0 {
-		return errors.New("number of images must be at least 1")
+		return errInvalidNumOfImages
 	}
 	// creates the output folder if it doesn't exists
-	err := os.MkdirAll(output, 0755)
+	err := os.MkdirAll(output, 0o755)
 	if err != nil {
 		return err
 	}

internal/cli/root.go

@@ -40,6 +40,7 @@ func getInputFromStdin() ([]byte, error) {
 	fmt.Print("Enter text: ")
 
 	reader := bufio.NewReader(os.Stdin)
+
 	text, err := reader.ReadBytes('\n')
 	if err != nil {
 		return nil, err

internal/decrypt/decrypt.go

@@ -37,6 +37,7 @@ func WithMasterKeyFile(filename string) OptFunc {
 		}
 
 		d.MasterKey = masterKey
+
 		return nil
 	}
 }
@@ -49,6 +50,7 @@ func WithPartialKeyFiles(filenames []string) OptFunc {
 				return err
 			}
 		}
+
 		return nil
 	}
 }
@@ -61,11 +63,12 @@ func WithPartialKeyFile(filename string) OptFunc {
 		}
 
 		d.Parts = append(d.Parts, sss.NewPart(partialKey))
+
 		return nil
 	}
 }
 
-// TODO fix
+// TODO fix.
 func WithPartialKeyImageFile(filename string) OptFunc {
 	return func(d *Decrypter) error {
 		partialKey, err := file.ReadKey(filename)
@@ -74,14 +77,16 @@ func WithPartialKeyImageFile(filename string) OptFunc {
 		}
 
 		d.Parts = append(d.Parts, sss.NewPart(partialKey))
+
 		return nil
 	}
 }
 
 func (d *Decrypter) Decrypt(content []byte, filename string) error {
-
-	var key []byte
-	var err error
+	var (
+		key []byte
+		err error
+	)
 
 	if len(d.MasterKey) > 0 {
 		key = d.MasterKey

internal/encrypt/encrypt.go

@@ -6,12 +6,11 @@ import (
 	"os"
 	"path/filepath"
 
-	"github.com/pkg/errors"
-
 	"github.com/enrichman/stegosecrets/internal/log"
 	"github.com/enrichman/stegosecrets/pkg/file"
 	"github.com/enrichman/stegosecrets/pkg/image"
 	sss "github.com/enrichman/stegosecrets/pkg/stego"
+	"github.com/pkg/errors"
 )
 
 type Encrypter struct {
@@ -44,7 +43,9 @@ func WithParts(parts int) OptFunc {
 		if parts < 0 || parts > 256 {
 			return errors.New("invalid parts")
 		}
+
 		e.Parts = parts
+
 		return nil
 	}
 }
@@ -54,7 +55,9 @@ func WithThreshold(threshold int) OptFunc {
 		if threshold < 0 || threshold > 256 {
 			return errors.New("invalid threshold")
 		}
+
 		e.Threshold = threshold
+
 		return nil
 	}
 }
@@ -63,12 +66,14 @@ func (e *Encrypter) Encrypt(reader io.Reader, filename string) error {
 	e.Logger.Print(fmt.Sprintf("Encrypting '%s'", filename))
 
 	e.Logger.Debug("generateAndSaveMasterKey")
+
 	masterKey, err := e.generateAndSaveMasterKey(filename)
 	if err != nil {
 		return err
 	}
 
 	e.Logger.Debug("encryptAndSaveMessage")
+
 	err = e.encryptAndSaveMessage(masterKey, reader, filename)
 	if err != nil {
 		return err
@@ -96,14 +101,15 @@ func (e *Encrypter) generateAndSaveMasterKey(filename string) ([]byte, error) {
 		return nil, err
 	}
 
-	if err := os.MkdirAll(outDirName, 0744); err != nil {
+	if err := os.MkdirAll(outDirName, 0o744); err != nil {
 		return nil, err
 	}
 
 	err = file.WriteKey(masterKey, fmt.Sprintf("%s/%s.enc", outDirName, filename))
 	if err != nil {
 		return nil, err
 	}
+
 	return masterKey, nil
 }
 
@@ -132,6 +138,7 @@ func (e *Encrypter) encryptAndSaveMessage(masterKey []byte, reader io.Reader, fi
 	if err != nil {
 		return err
 	}
+
 	return nil
 }
 
@@ -175,6 +182,7 @@ func (e *Encrypter) getImages(count int) ([]string, error) {
 		case ".jpg", ".jpeg", ".png":
 			images = append(images, filepath.Join(dir, file.Name()))
 		}
+
 		if len(images) >= count {
 			break
 		}
@@ -185,6 +193,7 @@ func (e *Encrypter) getImages(count int) ([]string, error) {
 	if lenImages == 0 {
 		return nil, errors.Errorf("no image files in %s dir: run 'stego images' to get some random pics", dir)
 	}
+
 	for lenImages < count {
 		images = append(images, images...)
 		lenImages = len(images)

internal/encrypt/encrypt_test.go

@@ -4,9 +4,8 @@ import (
 	"fmt"
 	"testing"
 
-	"github.com/stretchr/testify/assert"
-
 	"github.com/enrichman/stegosecrets/internal/encrypt"
+	"github.com/stretchr/testify/assert"
 )
 
 func TestNewEncrypter(t *testing.T) {

internal/log/logger.go

@@ -27,7 +27,7 @@ func (s *SimpleLogger) Debug(a ...any) {
 	}
 }
 
-// SilentLogger is a nop Logger implementation
+// SilentLogger is a nop Logger implementation.
 type SilentLogger struct{}
 
 func (s *SilentLogger) Print(a ...any) {}

pkg/file/file.go

@@ -26,17 +26,20 @@ func WriteFileChecksum(filename string) error {
 
 func WriteChecksum(content []byte, filename string) error {
 	h := sha256.New()
+
 	_, err := h.Write(content)
 	if err != nil {
 		return err
 	}
+
 	checksum := fmt.Sprintf("%x\t%s", h.Sum(nil), filepath.Base(filename))
 
 	return WriteFile([]byte(checksum), fmt.Sprintf("%s.checksum", filename))
 }
 
 func WriteKey(key []byte, filename string) error {
 	base64EncodedKey := base64.StdEncoding.EncodeToString(key)
+
 	return WriteFile([]byte(base64EncodedKey), fmt.Sprintf("%s.key", filename))
 }
 
@@ -48,6 +51,7 @@ func WriteFile(content []byte, filename string) error {
 	defer f.Close()
 
 	_, err = f.Write(content)
+
 	return err
 }
 
@@ -62,6 +66,7 @@ func ReadFile(filename string) ([]byte, error) {
 	if err != nil {
 		return nil, err
 	}
+
 	return bb, nil
 }
 
@@ -75,5 +80,6 @@ func ReadKey(filename string) ([]byte, error) {
 	if err != nil {
 		return nil, err
 	}
+
 	return decodedKey, nil
 }

pkg/file/file_test.go

@@ -2,17 +2,18 @@ package file
 
 import (
 	"fmt"
-	"github.com/stretchr/testify/require"
 	"os"
 	"path"
 	"testing"
+
+	"github.com/stretchr/testify/require"
 )
 
 func Test_WriteFileChecksum(t *testing.T) {
 	tmpDir := t.TempDir()
 	original := path.Join(tmpDir, "file")
 
-	err := os.WriteFile(original, []byte("content"), 0600)
+	err := os.WriteFile(original, []byte("content"), 0o600)
 	require.NoError(t, err)
 
 	err = WriteFileChecksum(original)

pkg/image/image.go

@@ -6,12 +6,11 @@ import (
 	"crypto/sha256"
 	"fmt"
 	"image"
+	_ "image/jpeg" // enable decoding for jpeg images.
+	_ "image/png"  // enable decoding for png images.
 	"io"
 	"os"
 
-	_ "image/jpeg"
-	_ "image/png"
-
 	"github.com/auyer/steganography"
 	"github.com/enrichman/stegosecrets/pkg/file"
 )
@@ -34,6 +33,7 @@ func EncodeSecretFromFileWithChecksum(secret []byte, inputFile, outputFile strin
 	}
 
 	checksum := fmt.Sprintf("%x\n", h.Sum(nil))
+
 	return file.WriteFile([]byte(checksum), fmt.Sprintf("%s.checksum", outputFile))
 }
 
@@ -63,12 +63,14 @@ func EncodeSecret(secret []byte, imgIn io.Reader, imgOut io.Writer) error {
 	// sizeOfMessage := steganography.MaxEncodeSize(img)
 
 	w := new(bytes.Buffer)
+
 	err = steganography.Encode(w, img, secret)
 	if err != nil {
 		return err
 	}
 
 	_, err = w.WriteTo(imgOut)
+
 	return err
 }
 
@@ -77,11 +79,13 @@ func DecodeSecret(imgIn io.Reader) ([]byte, error) {
 	if err != nil {
 		return nil, err
 	}
+
 	fmt.Println("format", format)
 
 	sizeOfMessage := steganography.GetMessageSizeFromImage(img)
 	fmt.Println("sizeOfMessage", sizeOfMessage)
 
 	msg := steganography.Decode(sizeOfMessage, img)
+
 	return msg, nil
 }

pkg/image/image_test.go

@@ -2,16 +2,18 @@ package image
 
 import (
 	"bytes"
-	"github.com/stretchr/testify/require"
 	"image"
 	"image/jpeg"
 	"testing"
+
+	"github.com/stretchr/testify/require"
 )
 
 func Test_EncodeDecodeSecret(t *testing.T) {
 	secret := []byte("test secret")
 
 	testImage := image.NewRGBA(image.Rect(0, 0, 256, 256))
+
 	var imageBuff bytes.Buffer
 	err := jpeg.Encode(&imageBuff, testImage, nil)
 	require.NoError(t, err)

pkg/stego/aes.go

@@ -8,11 +8,14 @@ import (
 	"io"
 )
 
+var errCiphertextBlockSizeTooShort = errors.New("ciphertext block size is too short")
+
 func GenerateMasterKey() ([]byte, error) {
 	key := make([]byte, 32)
 	if _, err := rand.Read(key); err != nil {
 		return nil, err
 	}
+
 	return key, nil
 }
 
@@ -46,7 +49,7 @@ func Decrypt(key []byte, cipherText []byte) ([]byte, error) {
 
 	// the length of the cipherText has to be more than 16 Bytes
 	if len(cipherText) < aes.BlockSize {
-		return nil, errors.New("ciphertext block size is too short")
+		return nil, errCiphertextBlockSizeTooShort
 	}
 
 	iv := cipherText[:aes.BlockSize]