feat(cfssljson): Add -output argument to save files in another directory

README.md

@@ -396,6 +396,9 @@ filenames in the following way:
 * if __bundle__       is specified,                    __basename-bundle.pem__   will be produced.
 * if __ocspResponse__ is specified,                    __basename-response.der__ will be produced.
 
+If you want to save the files in another directory, you can pass the
+folder path using the `-output` argument.
+
 Instead of saving to a file, you can pass `-stdout` to output the encoded
 contents to standard output.
 

cmd/cfssljson/cfssljson.go

@@ -9,6 +9,7 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"path/filepath"
 
 	"github.com/cloudflare/cfssl/cli/version"
 )
@@ -28,6 +29,16 @@ func writeFile(filespec, contents string, perms os.FileMode) {
 	}
 }
 
+// isDirectory returns true if the given path leads to a directory.
+func isDirectory(path string) (bool, error) {
+	fileInfo, err := os.Stat(path)
+	if err != nil {
+		return false, fmt.Errorf("failed to stat the directory (--output=%s): %v\n", path, err)
+	}
+
+	return fileInfo.IsDir(), nil
+}
+
 // ResponseMessage represents the format of a CFSSL output for an error or message
 type ResponseMessage struct {
 	Code    int    `json:"int"`
@@ -54,13 +65,23 @@ func main() {
 	inFile := flag.String("f", "-", "JSON input")
 	output := flag.Bool("stdout", false, "output the response instead of saving to a file")
 	printVersion := flag.Bool("version", false, "print version and exit")
+	outputDirectory := flag.String("output", "./", "place output files in a specific directory. Must be a folder")
 	flag.Parse()
 
 	if *printVersion {
 		fmt.Printf("%s", version.FormatVersion())
 		return
 	}
 
+	if ok, err := isDirectory(*outputDirectory); !ok {
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "failed to ensure directory: %v", err)
+		} else {
+			fmt.Fprintf(os.Stderr, "output argument is not a folder (path=%s)", *outputDirectory)
+		}
+		os.Exit(1)
+	}
+
 	var baseName string
 	if flag.NArg() == 0 {
 		baseName = "cert"
@@ -205,7 +226,8 @@ func main() {
 			}
 			fmt.Fprintf(os.Stdout, "%s\n", e.Contents)
 		} else {
-			writeFile(e.Filename, e.Contents, e.Perms)
+			p := filepath.Join(*outputDirectory, e.Filename)
+			writeFile(p, e.Contents, e.Perms)
 		}
 	}
 }

cmd/cfssljson/cfssljson_test.go

@@ -18,3 +18,38 @@ func TestReadFile(t *testing.T) {
 		t.Fatal("File not read correctly")
 	}
 }
+
+func TestIsDirectory(t *testing.T) {
+	t.Run("OK", func(t *testing.T) {
+		ok, err := isDirectory("testdata")
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if ok == false {
+			t.Fatal("should be a directory")
+		}
+	})
+
+	t.Run("NOK - Not a directory", func(t *testing.T) {
+		ok, err := isDirectory("cfssljson.go")
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if ok == true {
+			t.Fatal("should not be a directory")
+		}
+	})
+
+	t.Run("NOK - File not present", func(t *testing.T) {
+		ok, err := isDirectory("notpresent")
+		if err == nil {
+			t.Fatal(err)
+		}
+
+		if ok == true {
+			t.Fatal("should not exist")
+		}
+	})
+}