fix(extensions): preserve symlinks in extension source path while enforcing folder trust (#20867)

packages/a2a-server/src/agent/task.ts

@@ -28,6 +28,9 @@ import {
   type Config,
   type UserTierId,
   type ToolLiveOutput,
+  type AnsiLine,
+  type AnsiOutput,
+  type AnsiToken,
   isSubagentProgress,
   EDIT_TOOL_NAMES,
   processRestorableToolCalls,
@@ -344,10 +347,15 @@ export class Task {
       outputAsText = outputChunk;
     } else if (isSubagentProgress(outputChunk)) {
       outputAsText = JSON.stringify(outputChunk);
-    } else {
+    } else if (Array.isArray(outputChunk)) {
-      outputAsText = outputChunk
+      const ansiOutput: AnsiOutput = outputChunk;
-        .map((line) => line.map((token) => token.text).join(''))
+      outputAsText = ansiOutput
+        .map((line: AnsiLine) =>
+          line.map((token: AnsiToken) => token.text).join(''),
+        )
         .join('\n');
+    } else {
+      outputAsText = String(outputChunk);
     }
 
     logger.info(

packages/cli/src/commands/extensions/install.ts

@@ -5,6 +5,7 @@
  */
 
 import type { CommandModule } from 'yargs';
+import * as path from 'node:path';
 import chalk from 'chalk';
 import {
   debugLogger,
@@ -51,12 +52,13 @@ export async function handleInstall(args: InstallArgs) {
     const settings = loadSettings(workspaceDir).merged;
 
     if (installMetadata.type === 'local' || installMetadata.type === 'link') {
-      const resolvedPath = getRealPath(source);
+      const absolutePath = path.resolve(source);
-      installMetadata.source = resolvedPath;
+      const realPath = getRealPath(absolutePath);
-      const trustResult = isWorkspaceTrusted(settings, resolvedPath);
+      installMetadata.source = absolutePath;
+      const trustResult = isWorkspaceTrusted(settings, absolutePath);
       if (trustResult.isTrusted !== true) {
         const discoveryResults =
-          await FolderTrustDiscoveryService.discover(resolvedPath);
+          await FolderTrustDiscoveryService.discover(realPath);
 
         const hasDiscovery =
           discoveryResults.commands.length > 0 ||
@@ -69,7 +71,7 @@ export async function handleInstall(args: InstallArgs) {
           '',
           chalk.bold('Do you trust the files in this folder?'),
           '',
-          `The extension source at "${resolvedPath}" is not trusted.`,
+          `The extension source at "${absolutePath}" is not trusted.`,
           '',
           'Trusting a folder allows Gemini CLI to load its local configurations,',
           'including custom commands, hooks, MCP servers, agent skills, and',
@@ -127,10 +129,10 @@ export async function handleInstall(args: InstallArgs) {
         );
         if (confirmed) {
           const trustedFolders = loadTrustedFolders();
-          await trustedFolders.setValue(resolvedPath, TrustLevel.TRUST_FOLDER);
+          await trustedFolders.setValue(realPath, TrustLevel.TRUST_FOLDER);
         } else {
           throw new Error(
-            `Installation aborted: Folder "${resolvedPath}" is not trusted.`,
+            `Installation aborted: Folder "${absolutePath}" is not trusted.`,
           );
         }
       }

packages/cli/src/config/extension-manager.test.ts

@@ -12,6 +12,13 @@ import { ExtensionManager } from './extension-manager.js';
 import { createTestMergedSettings } from './settings.js';
 import { createExtension } from '../test-utils/createExtension.js';
 import { EXTENSIONS_DIRECTORY_NAME } from './extensions/variables.js';
+import {
+  TrustLevel,
+  loadTrustedFolders,
+  isWorkspaceTrusted,
+} from './trustedFolders.js';
+import { getRealPath } from '@google/gemini-cli-core';
+import type { MergedSettings } from './settings.js';
 
 const mockHomedir = vi.hoisted(() => vi.fn(() => '/tmp/mock-home'));
 
@@ -185,4 +192,157 @@ describe('ExtensionManager', () => {
       fs.rmSync(externalDir, { recursive: true, force: true });
     });
   });
+
+  describe('symlink handling', () => {
+    let extensionDir: string;
+    let symlinkDir: string;
+
+    beforeEach(() => {
+      extensionDir = path.join(tempHomeDir, 'extension');
+      symlinkDir = path.join(tempHomeDir, 'symlink-ext');
+
+      fs.mkdirSync(extensionDir, { recursive: true });
+
+      fs.writeFileSync(
+        path.join(extensionDir, 'gemini-extension.json'),
+        JSON.stringify({ name: 'test-ext', version: '1.0.0' }),
+      );
+
+      fs.symlinkSync(extensionDir, symlinkDir, 'dir');
+    });
+
+    it('preserves symlinks in installMetadata.source when linking', async () => {
+      const manager = new ExtensionManager({
+        workspaceDir: tempWorkspaceDir,
+        settings: {
+          security: {
+            folderTrust: { enabled: false }, // Disable trust for simplicity in this test
+          },
+          experimental: { extensionConfig: false },
+          admin: { extensions: { enabled: true }, mcp: { enabled: true } },
+          hooksConfig: { enabled: true },
+        } as unknown as MergedSettings,
+        requestConsent: () => Promise.resolve(true),
+        requestSetting: null,
+      });
+
+      // Trust the workspace to allow installation
+      const trustedFolders = loadTrustedFolders();
+      await trustedFolders.setValue(tempWorkspaceDir, TrustLevel.TRUST_FOLDER);
+
+      const installMetadata = {
+        source: symlinkDir,
+        type: 'link' as const,
+      };
+
+      await manager.loadExtensions();
+      const extension = await manager.installOrUpdateExtension(installMetadata);
+
+      // Desired behavior: it preserves symlinks (if they were absolute or relative as provided)
+      expect(extension.installMetadata?.source).toBe(symlinkDir);
+    });
+
+    it('works with the new install command logic (preserves symlink but trusts real path)', async () => {
+      // This simulates the logic in packages/cli/src/commands/extensions/install.ts
+      const absolutePath = path.resolve(symlinkDir);
+      const realPath = getRealPath(absolutePath);
+
+      const settings = {
+        security: {
+          folderTrust: { enabled: true },
+        },
+        experimental: { extensionConfig: false },
+        admin: { extensions: { enabled: true }, mcp: { enabled: true } },
+        hooksConfig: { enabled: true },
+      } as unknown as MergedSettings;
+
+      // Trust the REAL path
+      const trustedFolders = loadTrustedFolders();
+      await trustedFolders.setValue(realPath, TrustLevel.TRUST_FOLDER);
+
+      // Check trust of the symlink path
+      const trustResult = isWorkspaceTrusted(settings, absolutePath);
+      expect(trustResult.isTrusted).toBe(true);
+
+      const manager = new ExtensionManager({
+        workspaceDir: tempWorkspaceDir,
+        settings,
+        requestConsent: () => Promise.resolve(true),
+        requestSetting: null,
+      });
+
+      const installMetadata = {
+        source: absolutePath,
+        type: 'link' as const,
+      };
+
+      await manager.loadExtensions();
+      const extension = await manager.installOrUpdateExtension(installMetadata);
+
+      expect(extension.installMetadata?.source).toBe(absolutePath);
+      expect(extension.installMetadata?.source).not.toBe(realPath);
+    });
+
+    it('enforces allowedExtensions using the real path', async () => {
+      const absolutePath = path.resolve(symlinkDir);
+      const realPath = getRealPath(absolutePath);
+
+      const settings = {
+        security: {
+          folderTrust: { enabled: false },
+          // Only allow the real path, not the symlink path
+          allowedExtensions: [realPath.replace(/\\/g, '\\\\')],
+        },
+        experimental: { extensionConfig: false },
+        admin: { extensions: { enabled: true }, mcp: { enabled: true } },
+        hooksConfig: { enabled: true },
+      } as unknown as MergedSettings;
+
+      const manager = new ExtensionManager({
+        workspaceDir: tempWorkspaceDir,
+        settings,
+        requestConsent: () => Promise.resolve(true),
+        requestSetting: null,
+      });
+
+      const installMetadata = {
+        source: absolutePath,
+        type: 'link' as const,
+      };
+
+      await manager.loadExtensions();
+      // This should pass because realPath is allowed
+      const extension = await manager.installOrUpdateExtension(installMetadata);
+      expect(extension.name).toBe('test-ext');
+
+      // Now try with a settings that only allows the symlink path string
+      const settingsOnlySymlink = {
+        security: {
+          folderTrust: { enabled: false },
+          // Only allow the symlink path string explicitly
+          allowedExtensions: [absolutePath.replace(/\\/g, '\\\\')],
+        },
+        experimental: { extensionConfig: false },
+        admin: { extensions: { enabled: true }, mcp: { enabled: true } },
+        hooksConfig: { enabled: true },
+      } as unknown as MergedSettings;
+
+      const manager2 = new ExtensionManager({
+        workspaceDir: tempWorkspaceDir,
+        settings: settingsOnlySymlink,
+        requestConsent: () => Promise.resolve(true),
+        requestSetting: null,
+      });
+
+      // This should FAIL because it checks the real path against the pattern
+      // (Unless symlinkDir === extensionDir, which shouldn't happen in this test setup)
+      if (absolutePath !== realPath) {
+        await expect(
+          manager2.installOrUpdateExtension(installMetadata),
+        ).rejects.toThrow(
+          /is not allowed by the "allowedExtensions" security setting/,
+        );
+      }
+    });
+  });
 });

packages/cli/src/config/extension-manager.ts

@@ -161,7 +161,9 @@ export class ExtensionManager extends ExtensionLoader {
       const extensionAllowed = this.settings.security?.allowedExtensions.some(
         (pattern) => {
           try {
-            return new RegExp(pattern).test(installMetadata.source);
+            return new RegExp(pattern).test(
+              getRealPath(installMetadata.source),
+            );
           } catch (e) {
             throw new Error(
               `Invalid regex pattern in allowedExtensions setting: "${pattern}. Error: ${getErrorMessage(e)}`,
@@ -210,11 +212,9 @@ export class ExtensionManager extends ExtensionLoader {
       await fs.promises.mkdir(extensionsDir, { recursive: true });
 
       if (installMetadata.type === 'local' || installMetadata.type === 'link') {
-        installMetadata.source = getRealPath(
+        installMetadata.source = path.isAbsolute(installMetadata.source)
-          path.isAbsolute(installMetadata.source)
           ? installMetadata.source
-            : path.resolve(this.workspaceDir, installMetadata.source),
+          : path.resolve(this.workspaceDir, installMetadata.source);
-        );
       }
 
       let tempDir: string | undefined;
@@ -262,7 +262,7 @@ Would you like to attempt to install via "git clone" instead?`,
         installMetadata.type === 'local' ||
         installMetadata.type === 'link'
       ) {
-        localSourcePath = installMetadata.source;
+        localSourcePath = getRealPath(installMetadata.source);
       } else {
         throw new Error(`Unsupported install type: ${installMetadata.type}`);
       }
@@ -638,7 +638,9 @@ Would you like to attempt to install via "git clone" instead?`,
       const extensionAllowed = this.settings.security?.allowedExtensions.some(
         (pattern) => {
           try {
-            return new RegExp(pattern).test(installMetadata?.source);
+            return new RegExp(pattern).test(
+              getRealPath(installMetadata?.source ?? ''),
+            );
           } catch (e) {
             throw new Error(
               `Invalid regex pattern in allowedExtensions setting: "${pattern}. Error: ${getErrorMessage(e)}`,

packages/cli/src/config/trustedFolders.test.ts

@@ -506,7 +506,7 @@ describe('Trusted Folders', () => {
         const realDir = path.join(tempDir, 'real');
         const symlinkDir = path.join(tempDir, 'symlink');
         fs.mkdirSync(realDir);
-        fs.symlinkSync(realDir, symlinkDir);
+        fs.symlinkSync(realDir, symlinkDir, 'dir');
 
         // Rule uses realpath
         const config = { [realDir]: TrustLevel.TRUST_FOLDER };