Revert unintended credentials exposure (#18840)

Author: Adib234

docs/tools/mcp-server.md

@@ -739,21 +739,10 @@ The MCP integration tracks several states:
   cautiously and only for servers you completely control
 - **Access tokens:** Be security-aware when configuring environment variables
   containing API keys or tokens
-- **Environment variable redaction:** By default, the Gemini CLI redacts
-  sensitive environment variables (such as `GEMINI_API_KEY`, `GOOGLE_API_KEY`,
-  and variables matching patterns like `*TOKEN*`, `*SECRET*`, `*PASSWORD*`) when
-  spawning MCP servers using the `stdio` transport. This prevents unintended
-  exposure of your credentials to third-party servers.
-- **Explicit environment variables:** If you need to pass a specific environment
-  variable to an MCP server, you should define it explicitly in the `env`
-  property of the server configuration in `settings.json`.
 - **Sandbox compatibility:** When using sandboxing, ensure MCP servers are
-  available within the sandbox environment.
+  available within the sandbox environment
 - **Private data:** Using broadly scoped personal access tokens can lead to
   information leakage between repositories.
-- **Untrusted servers:** Be extremely cautious when adding MCP servers from
-  untrusted or third-party sources. Malicious servers could attempt to
-  exfiltrate data or perform unauthorized actions through the tools they expose.
 
 ### Performance and resource management
 

packages/cli/src/commands/mcp/add.ts

@@ -128,13 +128,6 @@ async function addMcpServer(
 
   settings.setValue(settingsScope, 'mcpServers', mcpServers);
 
-  if (transport === 'stdio') {
-    debugLogger.warn(
-      'Security Warning: Running MCP servers with stdio transport can expose inherited environment variables. ' +
-        'While the Gemini CLI redacts common API keys and secrets by default, you should only run servers from trusted sources.',
-    );
-  }
-
   if (isExistingServer) {
     debugLogger.log(`MCP server "${name}" updated in ${scope} settings.`);
   } else {

packages/core/src/services/environmentSanitization.test.ts

@@ -46,9 +46,6 @@ describe('sanitizeEnvironment', () => {
       CLIENT_ID: 'sensitive-id',
       DB_URI: 'sensitive-uri',
       DATABASE_URL: 'sensitive-url',
-      GEMINI_API_KEY: 'sensitive-gemini-key',
-      GOOGLE_API_KEY: 'sensitive-google-key',
-      GOOGLE_APPLICATION_CREDENTIALS: '/path/to/creds.json',
       SAFE_VAR: 'is-safe',
     };
     const sanitized = sanitizeEnvironment(env, EMPTY_OPTIONS);

packages/core/src/services/environmentSanitization.ts

@@ -103,9 +103,6 @@ export const NEVER_ALLOWED_ENVIRONMENT_VARIABLES: ReadonlySet<string> = new Set(
     'GOOGLE_CLOUD_PROJECT',
     'GOOGLE_CLOUD_ACCOUNT',
     'FIREBASE_PROJECT_ID',
-    'GEMINI_API_KEY',
-    'GOOGLE_API_KEY',
-    'GOOGLE_APPLICATION_CREDENTIALS',
   ],
 );
 

packages/core/src/tools/mcp-client.test.ts

@@ -1623,7 +1623,7 @@ describe('mcp-client', () => {
         {
           command: 'test-command',
           args: ['--foo', 'bar'],
-          env: { GEMINI_CLI_FOO: 'bar' },
+          env: { FOO: 'bar' },
           cwd: 'test/cwd',
         },
         false,
@@ -1634,80 +1634,11 @@ describe('mcp-client', () => {
         command: 'test-command',
         args: ['--foo', 'bar'],
         cwd: 'test/cwd',
-        env: expect.objectContaining({ GEMINI_CLI_FOO: 'bar' }),
+        env: expect.objectContaining({ FOO: 'bar' }),
         stderr: 'pipe',
       });
     });
 
-    it('should redact sensitive environment variables for command transport', async () => {
-      const mockedTransport = vi
-        .spyOn(SdkClientStdioLib, 'StdioClientTransport')
-        .mockReturnValue({} as SdkClientStdioLib.StdioClientTransport);
-
-      const originalEnv = process.env;
-      process.env = {
-        ...originalEnv,
-        GEMINI_API_KEY: 'sensitive-key',
-        GEMINI_CLI_SAFE_VAR: 'safe-value',
-      };
-      // Ensure strict sanitization is not triggered for this test
-      delete process.env['GITHUB_SHA'];
-      delete process.env['SURFACE'];
-
-      try {
-        await createTransport(
-          'test-server',
-          {
-            command: 'test-command',
-          },
-          false,
-          EMPTY_CONFIG,
-        );
-
-        const callArgs = mockedTransport.mock.calls[0][0];
-        expect(callArgs.env).toBeDefined();
-        expect(callArgs.env!['GEMINI_CLI_SAFE_VAR']).toBe('safe-value');
-        expect(callArgs.env!['GEMINI_API_KEY']).toBeUndefined();
-      } finally {
-        process.env = originalEnv;
-      }
-    });
-
-    it('should include extension settings in environment', async () => {
-      const mockedTransport = vi
-        .spyOn(SdkClientStdioLib, 'StdioClientTransport')
-        .mockReturnValue({} as SdkClientStdioLib.StdioClientTransport);
-
-      await createTransport(
-        'test-server',
-        {
-          command: 'test-command',
-          extension: {
-            name: 'test-ext',
-            resolvedSettings: [
-              {
-                envVar: 'GEMINI_CLI_EXT_VAR',
-                value: 'ext-value',
-                sensitive: false,
-                name: 'ext-setting',
-              },
-            ],
-            version: '',
-            isActive: false,
-            path: '',
-            contextFiles: [],
-            id: '',
-          },
-        },
-        false,
-        EMPTY_CONFIG,
-      );
-
-      const callArgs = mockedTransport.mock.calls[0][0];
-      expect(callArgs.env).toBeDefined();
-      expect(callArgs.env!['GEMINI_CLI_EXT_VAR']).toBe('ext-value');
-    });
-
     it('should exclude extension settings with undefined values from environment', async () => {
       const mockedTransport = vi
         .spyOn(SdkClientStdioLib, 'StdioClientTransport')

packages/core/src/tools/mcp-client.ts

@@ -34,11 +34,7 @@ import {
 } from '@modelcontextprotocol/sdk/types.js';
 import { ApprovalMode, PolicyDecision } from '../policy/types.js';
 import { parse } from 'shell-quote';
-import type {
-  Config,
-  GeminiCLIExtension,
-  MCPServerConfig,
-} from '../config/config.js';
+import type { Config, MCPServerConfig } from '../config/config.js';
 import { AuthProviderType } from '../config/config.js';
 import { GoogleCredentialProvider } from '../mcp/google-auth-provider.js';
 import { ServiceAccountImpersonationProvider } from '../mcp/sa-impersonation-provider.js';
@@ -1936,23 +1932,10 @@ export async function createTransport(
       command: mcpServerConfig.command,
       args: mcpServerConfig.args || [],
       // eslint-disable-next-line @typescript-eslint/no-unsafe-type-assertion
-      env: sanitizeEnvironment(
-        {
-          ...process.env,
-          ...getExtensionEnvironment(mcpServerConfig.extension),
-          ...(mcpServerConfig.env || {}),
-        },
-        {
-          ...sanitizationConfig,
-          allowedEnvironmentVariables: [
-            ...(sanitizationConfig.allowedEnvironmentVariables ?? []),
-            ...(mcpServerConfig.extension?.resolvedSettings?.map(
-              (s) => s.envVar,
-            ) ?? []),
-          ],
-          enableEnvironmentVariableRedaction: true,
-        },
-      ) as Record<string, string>,
+      env: {
+        ...sanitizeEnvironment(process.env, sanitizationConfig),
+        ...(mcpServerConfig.env || {}),
+      } as Record<string, string>,
       cwd: mcpServerConfig.cwd,
       stderr: 'pipe',
     });
@@ -2027,17 +2010,3 @@ export function isEnabled(
     )
   );
 }
-
-function getExtensionEnvironment(
-  extension?: GeminiCLIExtension,
-): Record<string, string> {
-  const env: Record<string, string> = {};
-  if (extension?.resolvedSettings) {
-    for (const setting of extension.resolvedSettings) {
-      if (setting.value) {
-        env[setting.envVar] = setting.value;
-      }
-    }
-  }
-  return env;
-}