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fix(core): block $VAR and ${VAR} variable expansion bypass (GHSA-wpqr-6v78-jr5g) #28403

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fix(core): block $VAR and ${VAR} variable expansion bypass (GHSA-wpqr-6v78-jr5g) #28403

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7 changes: 5 additions & 2 deletions .github/workflows/gemini-automated-issue-dedup.yml
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Original file line number Diff line number Diff line change
Expand Up @@ -28,7 +28,10 @@ jobs:
if: |-
github.repository == 'google-gemini/gemini-cli' &&
vars.TRIAGE_DEDUPLICATE_ISSUES != '' &&
(github.event_name == 'issues' ||
((github.event_name == 'issues' &&
(github.event.issue.author_association == 'OWNER' ||
github.event.issue.author_association == 'MEMBER' ||
github.event.issue.author_association == 'COLLABORATOR')) ||
github.event_name == 'workflow_dispatch' ||
(github.event_name == 'issue_comment' &&
contains(github.event.comment.body, '@gemini-cli /deduplicate') &&
Expand Down Expand Up @@ -62,7 +65,7 @@ jobs:
uses: 'google-github-actions/run-gemini-cli@a3bf79042542528e91937b3a3a6fbc4967ee3c31' # ratchet:google-github-actions/run-gemini-cli@v0
id: 'gemini_issue_deduplication'
env:
GITHUB_TOKEN: '${{ secrets.GITHUB_TOKEN }}'
GITHUB_TOKEN: ''
ISSUE_TITLE: '${{ github.event.issue.title }}'
ISSUE_BODY: '${{ github.event.issue.body }}'
ISSUE_NUMBER: '${{ github.event.issue.number }}'
Expand Down
198 changes: 198 additions & 0 deletions packages/core/src/utils/shell-utils.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,7 @@ import {
normalizeCommand,
hasRedirection,
resolveExecutable,
detectCommandSubstitution,
} from './shell-utils.js';
import path from 'node:path';

Expand Down Expand Up @@ -676,3 +677,200 @@ describe('resolveExecutable', () => {
expect(resolveExecutable('anything')).toBeUndefined();
});
});

describe('detectCommandSubstitution', () => {
beforeAll(async () => {
await initializeShellParsers();
});

afterEach(() => {
vi.unstubAllEnvs();
});

describe('should block variable expansion on both platforms', () => {
it.each([
'echo $GITHUB_TOKEN',
'echo $GOOGLE_CLOUD_ACCESS_TOKEN',
'echo $ACTIONS_ID_TOKEN_REQUEST_TOKEN',
'echo $GEMINI_API_KEY',
'echo ${GITHUB_TOKEN}',
'echo ${GOOGLE_CLOUD_ACCESS_TOKEN}',
'echo "value=$GITHUB_TOKEN"',
'echo "hello $USER"',
'cat $HOME/.ssh/id_rsa',
])('blocks on both bash and PowerShell: %s', (cmd) => {
mockPlatform.mockReturnValue('linux');
expect(detectCommandSubstitution(cmd)).toBe(true);
mockPlatform.mockReturnValue('win32');
vi.stubEnv('ComSpec', 'powershell.exe');
expect(detectCommandSubstitution(cmd)).toBe(true);
});
});

describe('should block bash-specific substitution', () => {
it.each([
'echo $(whoami)',
'echo `whoami`',
'cat <(ls)',
'diff <(cat a) >(cat b)',
])('blocks: %s', (cmd) => {
mockPlatform.mockReturnValue('linux');
expect(detectCommandSubstitution(cmd)).toBe(true);
});
});

describe('should block PowerShell-specific variable syntax', () => {
beforeEach(() => {
mockPlatform.mockReturnValue('win32');
vi.stubEnv('ComSpec', 'powershell.exe');
});

it.each([
'Write-Output $env:GEMINI_API_KEY',
'Write-Output $env:GITHUB_TOKEN',
'echo $env:GOOGLE_CLOUD_ACCESS_TOKEN',
'echo ${env:GEMINI_API_KEY}',
'echo ${env:GITHUB_TOKEN}',
'Write-Output "token=$env:GEMINI_API_KEY"',
'echo "DUPLICATE_ISSUES_CSV=$env:TOKEN" >> file',
])('blocks: %s', (cmd) => {
expect(detectCommandSubstitution(cmd)).toBe(true);
});
});

describe('should block PowerShell subexpressions', () => {
beforeEach(() => {
mockPlatform.mockReturnValue('win32');
vi.stubEnv('ComSpec', 'powershell.exe');
});

it.each(['echo $(Get-Process)', 'Write-Output @(1,2,3)'])(
'blocks: %s',
(cmd) => {
expect(detectCommandSubstitution(cmd)).toBe(true);
},
);
});

describe('should allow safe commands on both platforms', () => {
it.each([
'echo hello world',
'echo 42',
"echo 'literal $VAR not expanded'",
])('allows on both bash and PowerShell: %s', (cmd) => {
mockPlatform.mockReturnValue('linux');
expect(detectCommandSubstitution(cmd)).toBe(false);
mockPlatform.mockReturnValue('win32');
vi.stubEnv('ComSpec', 'powershell.exe');
expect(detectCommandSubstitution(cmd)).toBe(false);
});
});

describe('should allow safe bash-specific commands', () => {
it.each(['ls -la /tmp', 'cat /etc/hostname', 'grep -r "pattern" .'])(
'allows: %s',
(cmd) => {
mockPlatform.mockReturnValue('linux');
expect(detectCommandSubstitution(cmd)).toBe(false);
},
);
});

describe('should allow safe PowerShell-specific commands', () => {
beforeEach(() => {
mockPlatform.mockReturnValue('win32');
vi.stubEnv('ComSpec', 'powershell.exe');
});

it.each([
'Get-ChildItem C:\\Users',
'Write-Output "hello world"',
"echo 'literal $env:VAR not expanded'",
'dir C:\\temp',
])('allows: %s', (cmd) => {
expect(detectCommandSubstitution(cmd)).toBe(false);
});
});

it('should allow escaped dollar in double quotes (bash)', () => {
mockPlatform.mockReturnValue('linux');
expect(detectCommandSubstitution('echo "price is \\$5"')).toBe(false);
});

it('should allow dollar at end of string on both platforms', () => {
mockPlatform.mockReturnValue('linux');
expect(detectCommandSubstitution('echo cost is $')).toBe(false);
mockPlatform.mockReturnValue('win32');
vi.stubEnv('ComSpec', 'powershell.exe');
expect(detectCommandSubstitution('echo cost is $')).toBe(false);
});

it('should allow backtick-escaped dollar (PowerShell)', () => {
mockPlatform.mockReturnValue('win32');
vi.stubEnv('ComSpec', 'powershell.exe');
expect(detectCommandSubstitution('echo `$env:VAR')).toBe(false);
});

it('should allow $VAR inside single quotes on both platforms', () => {
mockPlatform.mockReturnValue('linux');
expect(detectCommandSubstitution("echo '$USER'")).toBe(false);
mockPlatform.mockReturnValue('win32');
vi.stubEnv('ComSpec', 'powershell.exe');
expect(detectCommandSubstitution("echo '$env:SECRET'")).toBe(false);
});

describe('should allow bash safe automatic variables', () => {
it('allows $_ (last argument)', () => {
mockPlatform.mockReturnValue('linux');
expect(detectCommandSubstitution('echo $_')).toBe(false);
});

it('allows $_ followed by space', () => {
mockPlatform.mockReturnValue('linux');
expect(detectCommandSubstitution('echo $_ something')).toBe(false);
});

it('blocks $_SECRET (not an exact match)', () => {
mockPlatform.mockReturnValue('linux');
expect(detectCommandSubstitution('echo $_SECRET')).toBe(true);
});

it('blocks $_1 (not an exact match)', () => {
mockPlatform.mockReturnValue('linux');
expect(detectCommandSubstitution('echo $_1')).toBe(true);
});
});

describe('should allow PowerShell safe automatic variables', () => {
beforeEach(() => {
mockPlatform.mockReturnValue('win32');
vi.stubEnv('ComSpec', 'powershell.exe');
});

it.each([
'Write-Output $true',
'Write-Output $True',
'Write-Output $TRUE',
'Write-Output $false',
'Write-Output $FALSE',
'Write-Output $null',
'Write-Output $Null',
'ForEach-Object { $_ }',
'echo $args',
'echo $ARGS',
])('allows: %s', (cmd) => {
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expect(detectCommandSubstitution(cmd)).toBe(false);
});

it.each([
'echo $trueVar',
'echo $_FOO',
'echo $TOKEN',
'echo $env:SECRET',
'echo $nullify',
'echo $true:SECRET',
])('blocks: %s', (cmd) => {
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expect(detectCommandSubstitution(cmd)).toBe(true);
});
});
});
51 changes: 47 additions & 4 deletions packages/core/src/utils/shell-utils.ts
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Expand Up @@ -1092,6 +1092,10 @@ export function detectCommandSubstitution(command: string): boolean {
return detectBashSubstitution(command);
}

const BASH_SAFE_VARS = new Set(['_']);
const PS_SAFE_VARS = new Set(['true', 'false', 'null', 'args', '_']);
const VAR_NAME_RE = /[a-zA-Z_]\w*/y;

function detectBashSubstitution(command: string): boolean {
let inSingleQuote = false;
let inDoubleQuote = false;
Expand Down Expand Up @@ -1124,8 +1128,26 @@ function detectBashSubstitution(command: string): boolean {
continue;
}
}
if (char === '$' && command[i + 1] === '(') {
return true;
if (char === '$' && i + 1 < command.length) {
const next = command[i + 1];
// Block $() command substitution
if (next === '(') {
return true;
}
// Block ${VAR} variable expansion
if (next === '{') {
return true;
}
// Block $VAR variable expansion ($ followed by letter or underscore)
// Allow known-safe bash automatic variables: $_ (last argument)
if (/[a-zA-Z_]/.test(next)) {
VAR_NAME_RE.lastIndex = i + 1;
const varMatch = VAR_NAME_RE.exec(command);
const varName = varMatch ? varMatch[0] : '';
if (!BASH_SAFE_VARS.has(varName)) {
return true;
}
}
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}
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if (
!inDoubleQuote &&
Expand Down Expand Up @@ -1171,8 +1193,29 @@ function detectPowerShellSubstitution(command: string): boolean {
i += 2;
continue;
}
if (char === '$' && command[i + 1] === '(') {
return true;
if (char === '$' && i + 1 < command.length) {
const next = command[i + 1];
// Block $() subexpression
if (next === '(') {
return true;
}
// Block ${...} braced variable expansion (e.g. ${env:GITHUB_TOKEN})
if (next === '{') {
return true;
}
// Block $VAR bare variable expansion (e.g. $env:GEMINI_API_KEY)
// Allow known-safe PowerShell automatic variables
if (/[a-zA-Z_]/.test(next)) {
VAR_NAME_RE.lastIndex = i + 1;
const varMatch = VAR_NAME_RE.exec(command);
const varName = varMatch ? varMatch[0].toLowerCase() : '';
if (
!PS_SAFE_VARS.has(varName) ||
command[i + 1 + varName.length] === ':'
) {
return true;
}
}
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}
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if (!inDoubleQuote && char === '@' && command[i + 1] === '(') {
return true;
Expand Down
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