fix: additional filesystem checks (#1799)

Release-As: 6.1.2

test/assumeRole.test.ts

@@ -0,0 +1,67 @@
+import * as core from '@actions/core';
+import {
+  AssumeRoleWithWebIdentityCommand,
+  GetCallerIdentityCommand,
+  STSClient,
+} from '@aws-sdk/client-sts';
+import { mockClient } from 'aws-sdk-client-mock';
+import { fs, vol } from 'memfs';
+import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
+import * as helpers from '../src/helpers';
+import { run } from '../src/index';
+import mocks from './mockinputs.test';
+
+vi.mock('node:fs');
+vi.mock('@actions/core');
+
+const mockedSTSClient = mockClient(STSClient);
+
+describe('assumeRoleWithWebIdentityTokenFile', {}, () => {
+  beforeEach(() => {
+    vi.restoreAllMocks();
+    vi.clearAllMocks();
+    mockedSTSClient.reset();
+    vol.reset();
+    helpers.withsleep(() => Promise.resolve());
+    vi.mocked(core.getInput).mockImplementation(mocks.getInput(mocks.WEBIDENTITY_TOKEN_FILE_INPUTS));
+    vi.mocked(core.getMultilineInput).mockReturnValue([]);
+    mockedSTSClient.on(GetCallerIdentityCommand).resolves({ ...mocks.outputs.GET_CALLER_IDENTITY });
+    process.env = { ...mocks.envs };
+    fs.mkdirSync('/home/github', { recursive: true });
+  });
+
+  afterEach(() => {
+    helpers.reset();
+  });
+
+  it('refuses when the token file is a symlink and never calls STS', async () => {
+    fs.mkdirSync('/etc', { recursive: true });
+    fs.writeFileSync('/etc/passwd', 'root:x:0:0::/root:/bin/sh');
+    fs.symlinkSync('/etc/passwd', '/home/github/file.txt');
+
+    await run();
+
+    expect(core.setFailed).toHaveBeenCalledWith(expect.stringMatching(/Refusing .* \(.* symbolic link\)/));
+    expect(mockedSTSClient.commandCalls(AssumeRoleWithWebIdentityCommand)).toHaveLength(0);
+    expect(fs.readFileSync('/etc/passwd', 'utf-8')).toBe('root:x:0:0::/root:/bin/sh');
+  });
+
+  it('preserves the existing missing-file error when the token file does not exist', async () => {
+    await run();
+
+    expect(core.setFailed).toHaveBeenCalledWith(expect.stringContaining('Web identity token file does not exist'));
+    expect(mockedSTSClient.commandCalls(AssumeRoleWithWebIdentityCommand)).toHaveLength(0);
+  });
+
+  it('passes token contents to STS when the file is regular', async () => {
+    fs.writeFileSync('/home/github/file.txt', 'real-token');
+    mockedSTSClient.on(AssumeRoleWithWebIdentityCommand).resolves(mocks.outputs.STS_CREDENTIALS);
+
+    await run();
+
+    expect(core.setFailed).not.toHaveBeenCalled();
+    const calls = mockedSTSClient.commandCalls(AssumeRoleWithWebIdentityCommand);
+    expect(calls).toHaveLength(1);
+    expect(calls[0]?.args[0].input.WebIdentityToken).toBe('real-token');
+  });
+});

test/helpers.test.ts

@@ -1,11 +1,16 @@
 import * as core from '@actions/core';
+import { fs, vol } from 'memfs';
 import { beforeEach, describe, expect, it, vi } from 'vitest';
 import * as helpers from '../src/helpers';
 
+vi.mock('node:fs');
+vi.mock('@actions/core');
+
 describe('Configure AWS Credentials helpers', {}, () => {
   beforeEach(() => {
     vi.restoreAllMocks();
-    vi.spyOn(core, 'debug').mockImplementation(() => {});
+    vi.clearAllMocks();
+    vol.reset();
   });
   it('removes brackets from GitHub Actor', {}, () => {
     const actor = 'actor[bot]';
@@ -97,4 +102,97 @@ describe('Configure AWS Credentials helpers', {}, () => {
     helpers.exportCredentials({ AccessKeyId: 'test', SecretAccessKey: 'test' }, false, true);
     expect(core.exportVariable).toHaveBeenCalledWith('AWS_SESSION_TOKEN', '');
   });
+
+  describe('filesystem helpers', {}, () => {
+    describe('isSymlink', {}, () => {
+      it('returns true for a symlink', {}, () => {
+        fs.mkdirSync('/dir', { recursive: true });
+        fs.writeFileSync('/dir/target', 'data');
+        fs.symlinkSync('/dir/target', '/dir/link');
+        expect(helpers.isSymlink('/dir/link')).toBe(true);
+      });
+
+      it('returns false for a regular file', {}, () => {
+        fs.mkdirSync('/dir', { recursive: true });
+        fs.writeFileSync('/dir/file', 'data');
+        expect(helpers.isSymlink('/dir/file')).toBe(false);
+      });
+
+      it('returns false for a missing path', {}, () => {
+        expect(helpers.isSymlink('/nonexistent')).toBe(false);
+      });
+    });
+
+    describe('readFileUtf8', {}, () => {
+      it('returns content for a regular file', {}, () => {
+        fs.mkdirSync('/dir', { recursive: true });
+        fs.writeFileSync('/dir/file', 'hello');
+        expect(helpers.readFileUtf8('/dir/file')).toBe('hello');
+      });
+
+      it('returns null when the file does not exist', {}, () => {
+        fs.mkdirSync('/dir', { recursive: true });
+        expect(helpers.readFileUtf8('/dir/missing')).toBe(null);
+      });
+
+      it('refuses to read through a symlink at the target', {}, () => {
+        fs.mkdirSync('/dir', { recursive: true });
+        fs.writeFileSync('/dir/secret', 'sensitive');
+        fs.symlinkSync('/dir/secret', '/dir/link');
+        expect(() => helpers.readFileUtf8('/dir/link')).toThrow(/Refusing .* \(.* symbolic link\)/);
+      });
+
+      it('refuses to read when the parent directory is a symlink', {}, () => {
+        fs.mkdirSync('/real/.aws', { recursive: true });
+        fs.writeFileSync('/real/.aws/credentials', 'data');
+        fs.mkdirSync('/home', { recursive: true });
+        fs.symlinkSync('/real/.aws', '/home/.aws');
+        expect(() => helpers.readFileUtf8('/home/.aws/credentials')).toThrow(/Refusing .* \(.* symbolic link\)/);
+      });
+
+      it('refuses to read when the path is a directory', {}, () => {
+        fs.mkdirSync('/dir/subdir', { recursive: true });
+        expect(() => helpers.readFileUtf8('/dir/subdir')).toThrow(/not a regular file/);
+      });
+    });
+
+    describe('writeFileUtf8', {}, () => {
+      it('writes content with the specified mode', {}, () => {
+        fs.mkdirSync('/dir', { recursive: true });
+        helpers.writeFileUtf8('/dir/file', 'payload', 0o600);
+        expect(fs.readFileSync('/dir/file', 'utf-8')).toBe('payload');
+        expect(fs.statSync('/dir/file').mode & 0o777).toBe(0o600);
+      });
+
+      it('refuses to follow a symlink at the target and leaves the target file untouched', {}, () => {
+        fs.mkdirSync('/dir', { recursive: true });
+        fs.writeFileSync('/dir/target', 'original');
+        fs.symlinkSync('/dir/target', '/dir/link');
+        expect(() => helpers.writeFileUtf8('/dir/link', 'attacker', 0o600)).toThrow(/Refusing .* \(.* symbolic link\)/);
+        expect(fs.readFileSync('/dir/target', 'utf-8')).toBe('original');
+      });
+
+      it.skipIf(process.platform === 'win32')('tightens mode on existing files', () => {
+        fs.mkdirSync('/dir', { recursive: true });
+        fs.writeFileSync('/dir/file', 'old', { mode: 0o644 });
+        helpers.writeFileUtf8('/dir/file', 'new', 0o600);
+        expect(fs.statSync('/dir/file').mode & 0o777).toBe(0o600);
+      });
+    });
+
+    describe('mkdir', {}, () => {
+      it('is idempotent on a regular directory', {}, () => {
+        helpers.mkdir('/some/nested/dir', 0o700);
+        helpers.mkdir('/some/nested/dir', 0o700);
+        expect(fs.statSync('/some/nested/dir').isDirectory()).toBe(true);
+      });
+
+      it('refuses when the target directory is a symlink', {}, () => {
+        fs.mkdirSync('/real', { recursive: true });
+        fs.mkdirSync('/home', { recursive: true });
+        fs.symlinkSync('/real', '/home/.aws');
+        expect(() => helpers.mkdir('/home/.aws', 0o700)).toThrow(/Refusing .* \(.* symbolic link\)/);
+      });
+    });
+  });
 });

test/profileManager.test.ts

@@ -11,13 +11,14 @@ import {
   writeProfileFiles,
 } from '../src/profileManager';
 
+vi.mock('node:fs');
+vi.mock('@actions/core');
+
 describe('Profile Manager', {}, () => {
   beforeEach(() => {
     vi.restoreAllMocks();
-    vi.mock('node:fs');
+    vi.clearAllMocks();
     vol.reset();
-    vi.spyOn(core, 'debug').mockImplementation(() => {});
-    vi.spyOn(core, 'info').mockImplementation(() => {});
   });
 
   describe('parseIni', {}, () => {
@@ -721,4 +722,69 @@ describe('Profile Manager', {}, () => {
       );
     });
   });
+
+  describe('symlink hardening', {}, () => {
+    const credsPath = '/home/user/.aws/credentials';
+    const configPath = '/home/user/.aws/config';
+
+    beforeEach(() => {
+      process.env.AWS_SHARED_CREDENTIALS_FILE = credsPath;
+      process.env.AWS_CONFIG_FILE = configPath;
+    });
+
+    it('mergeProfileSection refuses when the credentials path is a symlink and leaves the target unchanged', {}, () => {
+      fs.mkdirSync('/home/user/.aws', { recursive: true });
+      fs.mkdirSync('/etc', { recursive: true });
+      fs.writeFileSync('/etc/passwd', 'root:x:0:0::/root:/bin/sh');
+      fs.symlinkSync('/etc/passwd', credsPath);
+
+      expect(() => mergeProfileSection(credsPath, 'dev', { aws_access_key_id: 'AKIA' }, true)).toThrow(
+        /Refusing .* \(.* symbolic link\)/,
+      );
+      expect(fs.readFileSync('/etc/passwd', 'utf-8')).toBe('root:x:0:0::/root:/bin/sh');
+    });
+
+    it('mergeProfileSection refuses when the config path is a symlink', {}, () => {
+      fs.mkdirSync('/home/user/.aws', { recursive: true });
+      fs.mkdirSync('/etc', { recursive: true });
+      fs.writeFileSync('/etc/sensitive', 'do not overwrite');
+      fs.symlinkSync('/etc/sensitive', configPath);
+
+      expect(() => mergeProfileSection(configPath, 'profile dev', { region: 'us-east-1' }, true)).toThrow(
+        /Refusing .* \(.* symbolic link\)/,
+      );
+      expect(fs.readFileSync('/etc/sensitive', 'utf-8')).toBe('do not overwrite');
+    });
+
+    it('ensureAwsDirectoryExists refuses when ~/.aws is a symlink', {}, () => {
+      fs.mkdirSync('/real-target', { recursive: true });
+      fs.mkdirSync('/home/user', { recursive: true });
+      fs.symlinkSync('/real-target', '/home/user/.aws');
+
+      expect(() => ensureAwsDirectoryExists(credsPath)).toThrow(/Refusing .* \(.* symbolic link\)/);
+    });
+
+    it('writeProfileFiles refuses to overwrite a pre-existing symlink at the credentials path', {}, () => {
+      fs.mkdirSync('/home/user/.aws', { recursive: true });
+      fs.mkdirSync('/etc', { recursive: true });
+      fs.writeFileSync('/etc/passwd', 'root:x:0:0::/root:/bin/sh');
+      fs.symlinkSync('/etc/passwd', credsPath);
+
+      expect(() =>
+        writeProfileFiles('dev', { AccessKeyId: 'AKIA', SecretAccessKey: 'secret' }, 'us-east-1', true),
+      ).toThrow(/Refusing .* \(.* symbolic link\)/);
+
+      expect(fs.lstatSync(credsPath).isSymbolicLink()).toBe(true);
+      expect(fs.readFileSync('/etc/passwd', 'utf-8')).toBe('root:x:0:0::/root:/bin/sh');
+    });
+
+    it('happy path still writes both files with mode 0o600 when no symlinks are present', {}, () => {
+      writeProfileFiles('dev', { AccessKeyId: 'AKIA', SecretAccessKey: 'secret' }, 'us-east-1', false);
+
+      expect(fs.statSync(credsPath).mode & 0o777).toBe(0o600);
+      expect(fs.statSync(configPath).mode & 0o777).toBe(0o600);
+      expect(fs.lstatSync(credsPath).isSymbolicLink()).toBe(false);
+      expect(fs.lstatSync(configPath).isSymbolicLink()).toBe(false);
+    });
+  });
 });