feat(image): support tar.gz image (fanal#40)

analyzer/analyzer.go

@@ -1,10 +1,14 @@
 package analyzer
 
 import (
+	"compress/gzip"
 	"context"
 	"io"
+	"os"
 	"time"
 
+	"github.com/aquasecurity/fanal/utils"
+
 	"github.com/aquasecurity/fanal/types"
 
 	"golang.org/x/xerrors"
@@ -136,7 +140,15 @@ func Analyze(ctx context.Context, imageName string, opts ...types.DockerOption)
 	return fileMap, nil
 }
 
-func AnalyzeFromFile(ctx context.Context, r io.ReadCloser) (fileMap extractor.FileMap, err error) {
+func AnalyzeFile(ctx context.Context, f *os.File) (fileMap extractor.FileMap, err error) {
+	var r io.Reader
+	r = f
+	if utils.IsGzip(f) {
+		r, err = gzip.NewReader(f)
+		if err != nil {
+			return nil, xerrors.Errorf("failed to open gzip: %w", err)
+		}
+	}
 	e := docker.NewDockerExtractor(types.DockerOption{})
 	fileMap, err = e.ExtractFromFile(ctx, r, RequiredFilenames())
 	if err != nil {

cmd/fanal/main.go

@@ -64,7 +64,7 @@ func run() (err error) {
 			return err
 		}
 
-		files, err = analyzer.AnalyzeFromFile(ctx, rc)
+		files, err = analyzer.AnalyzeFile(ctx, rc)
 		if err != nil {
 			return err
 		}

utils/utils.go

@@ -2,6 +2,7 @@ package utils
 
 import (
 	"fmt"
+	"io"
 	"os"
 	"os/exec"
 	"path/filepath"
@@ -37,3 +38,13 @@ func IsCommandAvailable(name string) bool {
 	}
 	return true
 }
+
+func IsGzip(f *os.File) bool {
+	buf := make([]byte, 3)
+	n, _ := f.Read(buf)
+	defer f.Seek(0, io.SeekStart)
+	if n < 3 {
+		return false
+	}
+	return buf[0] == 0x1F && buf[1] == 0x8B && buf[2] == 0x8
+}

utils/utils_test.go

@@ -0,0 +1,32 @@
+package utils
+
+import (
+	"os"
+	"testing"
+)
+
+func TestIsGzip(t *testing.T) {
+	var tests = []struct {
+		in   string
+		want bool
+	}{
+		{"testdata/test.txt.gz", true},
+		{"testdata/test.tar.gz", true},
+		{"testdata/test.txt", false},
+		{"testdata/test.txt.zst", false},
+		{"testdata/aqua.png", false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.in, func(t *testing.T) {
+			f, err := os.Open(tt.in)
+			if err != nil {
+				t.Fatalf("unknown error: %s", err)
+			}
+
+			got := IsGzip(f)
+			if got != tt.want {
+				t.Errorf("got %t, want %t", got, tt.want)
+			}
+		})
+	}
+}