Checks for windows permissions (gomods#902)

* Checks for windows permissions

* Fix bug

* fix test

* Update perms

* Fix perms

pkg/config/config.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"runtime"
 
 	"github.com/BurntSushi/toml"
 	"github.com/gomods/athens/pkg/errors"
@@ -140,8 +141,15 @@ func checkFilePerms(files ...string) error {
 			continue
 		}
 
-		if fInfo.Mode() != 0600 {
-			return errors.E(op, f+" should have 0600 as permission")
+		if runtime.GOOS == "windows" {
+			if (fInfo.Mode() & 0600) != 0600 {
+				return errors.E(op, f+" should have 0600 as permission")
+			}
+		} else {
+			// Assume unix based system (MacOS and Linux)
+			if fInfo.Mode() != 0640 {
+				return errors.E(op, f+" should have 0640 as permission")
+			}
 		}
 	}
 

pkg/config/config_test.go

@@ -297,26 +297,34 @@ func restoreEnv(envVars map[string]string) {
 	}
 }
 
-func Test_checkFilePerms(t *testing.T) {
-	// TODO: os.Chmod(..) doesn't work on Windows as it does on Unix
-	// Skip for now
-	// issue: https://github.com/gomods/athens/issues/879
+func invalidPerm() os.FileMode {
+	if runtime.GOOS == "windows" {
+		return 0200
+	}
+	return 0777
+}
+
+func correctPerm() os.FileMode {
 	if runtime.GOOS == "windows" {
-		t.SkipNow()
+		return 0600
 	}
+	return 0640
+}
+
+func Test_checkFilePerms(t *testing.T) {
 	f1, err := ioutil.TempFile(os.TempDir(), "prefix-")
 	if err != nil {
 		t.FailNow()
 	}
 	defer os.Remove(f1.Name())
-	err = os.Chmod(f1.Name(), 0777)
+	err = os.Chmod(f1.Name(), invalidPerm())
 
 	f2, err := ioutil.TempFile(os.TempDir(), "prefix-")
 	if err != nil {
 		t.FailNow()
 	}
 	defer os.Remove(f2.Name())
-	err = os.Chmod(f2.Name(), 0600)
+	err = os.Chmod(f2.Name(), correctPerm())
 
 	type args struct {
 		files []string