feat(plugin): add support for nested archives (#6845)

Signed-off-by: knqyf263 <knqyf263@gmail.com>

docs/docs/plugin/user-guide.md

@@ -40,8 +40,6 @@ $ trivy plugin install referrer
 
 This command will download the plugin and install it in the plugin cache.
 
-
-
 Trivy adheres to the XDG specification, so the location depends on whether XDG_DATA_HOME is set.
 Trivy will now search XDG_DATA_HOME for the location of the Trivy plugins cache.
 The preference order is as follows:
@@ -55,7 +53,10 @@ Furthermore, it is possible to download plugins that are not registered in the i
 $ trivy plugin install github.com/aquasecurity/trivy-plugin-kubectl
 ```
 ```bash
-$ trivy plugin install myplugin.tar.gz
+$ trivy plugin install https://github.com/aquasecurity/trivy-plugin-kubectl/archive/refs/heads/main.zip
+```
+```bash
+$ trivy plugin install ./myplugin.tar.gz
 ```
 
 If the plugin's Git repository is [properly tagged](./developer-guide.md#tagging-plugin-repositories), you can specify the version to install like this:

pkg/plugin/manager.go

@@ -116,6 +116,14 @@ func (m *Manager) install(ctx context.Context, src string, opts Options) (Plugin
 	}
 	defer os.RemoveAll(tempDir)
 
+	if entries, err := os.ReadDir(tempDir); err != nil {
+		return Plugin{}, xerrors.Errorf("failed to read %s: %w", tempDir, err)
+	} else if len(entries) == 1 && entries[0].IsDir() {
+		//　A single directory may be contained within an archive file.
+		// e.g. https://github.com/aquasecurity/trivy-plugin-referrer/archive/refs/heads/main.zip
+		tempDir = filepath.Join(tempDir, entries[0].Name())
+	}
+
 	m.logger.DebugContext(ctx, "Loading the plugin metadata...")
 	plugin, err := m.loadMetadata(tempDir)
 	if err != nil {

pkg/plugin/manager_unix_test.go

@@ -63,12 +63,17 @@ func modifyManifest(t *testing.T, worktree, version string) {
 }
 
 func TestManager_Install(t *testing.T) {
-	gs := setupGitRepository(t, "test_plugin", "testdata/test_plugin")
+	gs := setupGitRepository(t, "test_plugin", "testdata/test_plugin/test_plugin")
 	t.Cleanup(gs.Close)
 
 	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		zr := zip.NewWriter(w)
-		require.NoError(t, zr.AddFS(os.DirFS("testdata/test_plugin")))
+		switch r.URL.Path {
+		case "/test_plugin.zip":
+			require.NoError(t, zr.AddFS(os.DirFS("testdata/test_plugin/test_plugin")))
+		case "/test_nested.zip":
+			require.NoError(t, zr.AddFS(os.DirFS("testdata/test_plugin")))
+		}
 		require.NoError(t, zr.Close())
 	}))
 	t.Cleanup(ts.Close)
@@ -119,6 +124,13 @@ func TestManager_Install(t *testing.T) {
 			wantFile:   ".trivy/plugins/test_plugin/test.sh",
 			wantLogs:   fmt.Sprintf(wantLogs, ts.URL+"/test_plugin.zip", "0.2.0"),
 		},
+		{
+			name:       "nested archive",
+			pluginName: ts.URL + "/test_nested.zip",
+			want:       wantPlugin,
+			wantFile:   ".trivy/plugins/test_plugin/test.sh",
+			wantLogs:   fmt.Sprintf(wantLogs, ts.URL+"/test_nested.zip", "0.2.0"),
+		},
 		{
 			name:       "local path",
 			pluginName: "testdata/test_plugin",