Backport fix to main (#42979)

* fixes

(cherry picked from commit a2c386915ce11b9422f4af8ae181eaa1a22bc5c3)
(cherry picked from commit 06706efbbe)

* fix regex

(cherry picked from commit a259213a3badc9618e969f2c8db0a0143f00faee)
(cherry picked from commit 1d7105c095)

* lint (#42970)

(cherry picked from commit afb9e8e5f3)

Co-authored-by: Will Browne <will.browne@grafana.com>
Co-authored-by: malcolmholmes <42545407+malcolmholmes@users.noreply.github.com>

pkg/api/plugins.go

@@ -490,15 +490,15 @@ func (hs *HTTPServer) pluginMarkdown(ctx context.Context, pluginId string, name
 	}
 
 	// nolint:gosec
-	// We can ignore the gosec G304 warning on this one because `plugin.PluginDir` is based
-	// on plugin the folder structure on disk and not user input.
-	path := filepath.Join(plugin.PluginDir, fmt.Sprintf("%s.md", strings.ToUpper(name)))
+	// We can ignore the gosec G304 warning since we have cleaned the requested file path and subsequently
+	// use this with a prefix of the plugin's directory, which is set during plugin loading
+	path := filepath.Join(plugin.PluginDir, mdFilepath(strings.ToUpper(name)))
 	exists, err := fs.Exists(path)
 	if err != nil {
 		return nil, err
 	}
 	if !exists {
-		path = filepath.Join(plugin.PluginDir, fmt.Sprintf("%s.md", strings.ToLower(name)))
+		path = filepath.Join(plugin.PluginDir, mdFilepath(strings.ToLower(name)))
 	}
 
 	exists, err = fs.Exists(path)
@@ -510,11 +510,15 @@ func (hs *HTTPServer) pluginMarkdown(ctx context.Context, pluginId string, name
 	}
 
 	// nolint:gosec
-	// We can ignore the gosec G304 warning on this one because `plugin.PluginDir` is based
-	// on plugin the folder structure on disk and not user input.
+	// We can ignore the gosec G304 warning since we have cleaned the requested file path and subsequently
+	// use this with a prefix of the plugin's directory, which is set during plugin loading
 	data, err := ioutil.ReadFile(path)
 	if err != nil {
 		return nil, err
 	}
 	return data, nil
 }
+
+func mdFilepath(mdFilename string) string {
+	return filepath.Clean(filepath.Join("/", fmt.Sprintf("%s.md", mdFilename)))
+}