cli: chmod 755 for backend plugin binaries

Fixes grafana#15500. Does a simple filename check if the binary names ends
with _linux_amd64 or _darwin_amd64 then sets the file mode to 755.

pkg/cmd/grafana-cli/commands/install_command.go

@@ -57,6 +57,8 @@ func installCommand(c CommandLine) error {
 	return InstallPlugin(pluginToInstall, version, c)
 }
 
+// InstallPlugin downloads the plugin code as a zip file from the Grafana.com API
+// and then extracts the zip into the plugins directory.
 func InstallPlugin(pluginName, version string, c CommandLine) error {
 	pluginFolder := c.PluginDirectory()
 	downloadURL := c.PluginURL()
@@ -152,6 +154,10 @@ func downloadFile(pluginName, filePath, url string) (err error) {
 		return err
 	}
 
+	return extractFiles(body, pluginName, filePath)
+}
+
+func extractFiles(body []byte, pluginName string, filePath string) error {
 	r, err := zip.NewReader(bytes.NewReader(body), int64(len(body)))
 	if err != nil {
 		return err
@@ -161,12 +167,18 @@ func downloadFile(pluginName, filePath, url string) (err error) {
 
 		if zf.FileInfo().IsDir() {
 			err := os.Mkdir(newFile, 0777)
-			if PermissionsError(err) {
+			if permissionsError(err) {
 				return fmt.Errorf(permissionsDeniedMessage, newFile)
 			}
 		} else {
-			dst, err := os.Create(newFile)
-			if PermissionsError(err) {
+			fileMode := zf.Mode()
+
+			if strings.HasSuffix(newFile, "_linux_amd64") || strings.HasSuffix(newFile, "_darwin_amd64") {
+				fileMode = os.FileMode(0755)
+			}
+
+			dst, err := os.OpenFile(newFile, os.O_RDWR|os.O_CREATE|os.O_TRUNC, fileMode)
+			if permissionsError(err) {
 				return fmt.Errorf(permissionsDeniedMessage, newFile)
 			}
 
@@ -184,6 +196,6 @@ func downloadFile(pluginName, filePath, url string) (err error) {
 	return nil
 }
 
-func PermissionsError(err error) bool {
+func permissionsError(err error) bool {
 	return err != nil && strings.Contains(err.Error(), "permission denied")
 }

pkg/cmd/grafana-cli/commands/install_command_test.go

@@ -1,6 +1,8 @@
 package commands
 
 import (
+	"io/ioutil"
+	"os"
 	"testing"
 
 	. "github.com/smartystreets/goconvey/convey"
@@ -37,3 +39,42 @@ func TestFoldernameReplacement(t *testing.T) {
 		})
 	})
 }
+
+func TestExtractFiles(t *testing.T) {
+	Convey("Should preserve file permissions for plugin backend binaries for linux and darwin", t, func() {
+		err := os.RemoveAll("testdata/fake-plugins-dir")
+		So(err, ShouldBeNil)
+
+		err = os.MkdirAll("testdata/fake-plugins-dir", 0774)
+		So(err, ShouldBeNil)
+
+		body, err := ioutil.ReadFile("testdata/grafana-simple-json-datasource-ec18fa4da8096a952608a7e4c7782b4260b41bcf.zip")
+		So(err, ShouldBeNil)
+
+		err = extractFiles(body, "grafana-simple-json-datasource", "testdata/fake-plugins-dir")
+		So(err, ShouldBeNil)
+
+		//File in zip has permissions 777
+		fileInfo, err := os.Stat("testdata/fake-plugins-dir/grafana-simple-json-datasource/simple-plugin_darwin_amd64")
+		So(err, ShouldBeNil)
+		So(fileInfo.Mode().String(), ShouldEqual, "-rwxr-xr-x")
+
+		//File in zip has permission 664
+		fileInfo, err = os.Stat("testdata/fake-plugins-dir/grafana-simple-json-datasource/simple-plugin_linux_amd64")
+		So(err, ShouldBeNil)
+		So(fileInfo.Mode().String(), ShouldEqual, "-rwxr-xr-x")
+
+		//File in zip has permission 644
+		fileInfo, err = os.Stat("testdata/fake-plugins-dir/grafana-simple-json-datasource/simple-plugin_windows_amd64.exe")
+		So(err, ShouldBeNil)
+		So(fileInfo.Mode().String(), ShouldEqual, "-rw-r--r--")
+
+		//File in zip has permission 755
+		fileInfo, err = os.Stat("testdata/fake-plugins-dir/grafana-simple-json-datasource/non-plugin-binary")
+		So(err, ShouldBeNil)
+		So(fileInfo.Mode().String(), ShouldEqual, "-rwxr-xr-x")
+
+		err = os.RemoveAll("testdata/fake-plugins-dir")
+		So(err, ShouldBeNil)
+	})
+}