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Auto-approve writes to null device files (/dev/null, $null) #276263

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Merged
merged 6 commits into from
Nov 14, 2025
Merged

Auto-approve writes to null device files (/dev/null, $null) #276263

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d625eb0
Initial plan
Copilot Nov 8, 2025
f310c11
Add auto-approval for writes to null device files
Copilot Nov 8, 2025
39ee93f
Merge branch 'main' into copilot/allow-write-to-dev-null
Tyriar Nov 10, 2025
9fb8b07
Simplify null device detection
Tyriar Nov 10, 2025
7afcca6
Update src/vs/workbench/contrib/terminalContrib/chatAgentTools/browse…
Tyriar Nov 11, 2025
b0b7f21
Merge branch 'main' into copilot/allow-write-to-dev-null
Tyriar Nov 11, 2025
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47 changes: 37 additions & 10 deletions ...lContrib/chatAgentTools/browser/tools/commandLineAnalyzer/commandLineFileWriteAnalyzer.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -10,12 +10,16 @@ import { localize } from '../../../../../../../nls.js';
import { IConfigurationService } from '../../../../../../../platform/configuration/common/configuration.js';
import { IWorkspaceContextService } from '../../../../../../../platform/workspace/common/workspace.js';
import { TerminalChatAgentToolsSettingId } from '../../../common/terminalChatAgentToolsConfiguration.js';
import { type TreeSitterCommandParser } from '../../treeSitterCommandParser.js';
import { TreeSitterCommandParserLanguage, type TreeSitterCommandParser } from '../../treeSitterCommandParser.js';
import type { ICommandLineAnalyzer, ICommandLineAnalyzerOptions, ICommandLineAnalyzerResult } from './commandLineAnalyzer.js';
import { OperatingSystem } from '../../../../../../../base/common/platform.js';
import { isString } from '../../../../../../../base/common/types.js';
import { ILabelService } from '../../../../../../../platform/label/common/label.js';

const nullDevice = Symbol('null device');

type FileWrite = URI | string | typeof nullDevice;

export class CommandLineFileWriteAnalyzer extends Disposable implements ICommandLineAnalyzer {
constructor(
private readonly _treeSitterCommandParser: TreeSitterCommandParser,
Expand All @@ -28,7 +32,7 @@ export class CommandLineFileWriteAnalyzer extends Disposable implements ICommand
}

async analyze(options: ICommandLineAnalyzerOptions): Promise<ICommandLineAnalyzerResult> {
let fileWrites: URI[] | string[];
let fileWrites: FileWrite[];
try {
fileWrites = await this._getFileWrites(options);
} catch (e) {
Expand All @@ -41,14 +45,18 @@ export class CommandLineFileWriteAnalyzer extends Disposable implements ICommand
return this._getResult(options, fileWrites);
}

private async _getFileWrites(options: ICommandLineAnalyzerOptions): Promise<URI[] | string[]> {
let fileWrites: URI[] | string[] = [];
const capturedFileWrites = await this._treeSitterCommandParser.getFileWrites(options.treeSitterLanguage, options.commandLine);
private async _getFileWrites(options: ICommandLineAnalyzerOptions): Promise<FileWrite[]> {
let fileWrites: FileWrite[] = [];
const capturedFileWrites = (await this._treeSitterCommandParser.getFileWrites(options.treeSitterLanguage, options.commandLine))
.map(this._mapNullDevice.bind(this, options));
if (capturedFileWrites.length) {
const cwd = options.cwd;
if (cwd) {
this._log('Detected cwd', cwd.toString());
fileWrites = capturedFileWrites.map(e => {
if (e === nullDevice) {
return e;
}
const isAbsolute = options.os === OperatingSystem.Windows ? win32.isAbsolute(e) : posix.isAbsolute(e);
if (isAbsolute) {
return URI.file(e);
Expand All @@ -65,7 +73,18 @@ export class CommandLineFileWriteAnalyzer extends Disposable implements ICommand
return fileWrites;
}

private _getResult(options: ICommandLineAnalyzerOptions, fileWrites: URI[] | string[]): ICommandLineAnalyzerResult {
private _mapNullDevice(options: ICommandLineAnalyzerOptions, rawFileWrite: string): string | typeof nullDevice {
if (options.treeSitterLanguage === TreeSitterCommandParserLanguage.PowerShell) {
return rawFileWrite === '$null'
? nullDevice
: rawFileWrite;
}
return rawFileWrite === '/dev/null'
? nullDevice
: rawFileWrite;
}

private _getResult(options: ICommandLineAnalyzerOptions, fileWrites: FileWrite[]): ICommandLineAnalyzerResult {
let isAutoApproveAllowed = true;
if (fileWrites.length > 0) {
const blockDetectedFileWrites = this._configurationService.getValue<string>(TerminalChatAgentToolsSettingId.BlockDetectedFileWrites);
Expand All @@ -79,6 +98,11 @@ export class CommandLineFileWriteAnalyzer extends Disposable implements ICommand
const workspaceFolders = this._workspaceContextService.getWorkspace().folders;
if (workspaceFolders.length > 0) {
for (const fileWrite of fileWrites) {
if (fileWrite === nullDevice) {
this._log('File write to null device allowed', URI.isUri(fileWrite) ? fileWrite.toString() : fileWrite);
continue;
}

if (isString(fileWrite)) {
const isAbsolute = options.os === OperatingSystem.Windows ? win32.isAbsolute(fileWrite) : posix.isAbsolute(fileWrite);
if (!isAbsolute) {
Expand Down Expand Up @@ -106,9 +130,12 @@ export class CommandLineFileWriteAnalyzer extends Disposable implements ICommand
}
}
} else {
// No workspace folders, consider all writes as outside workspace
isAutoApproveAllowed = false;
this._log('File writes blocked - no workspace folders');
// No workspace folders, allow safe null device paths even without workspace
const hasOnlyNullDevices = fileWrites.every(fw => fw === nullDevice);
if (!hasOnlyNullDevices) {
isAutoApproveAllowed = false;
this._log('File writes blocked - no workspace folders');
}
}
break;
}
Expand All @@ -121,7 +148,7 @@ export class CommandLineFileWriteAnalyzer extends Disposable implements ICommand

const disclaimers: string[] = [];
if (fileWrites.length > 0) {
const fileWritesList = fileWrites.map(fw => `\`${URI.isUri(fw) ? this._labelService.getUriLabel(fw) : fw}\``).join(', ');
const fileWritesList = fileWrites.map(fw => `\`${URI.isUri(fw) ? this._labelService.getUriLabel(fw) : fw === nullDevice ? '/dev/null' : fw.toString()}\``).join(', ');
if (!isAutoApproveAllowed) {
disclaimers.push(localize('runInTerminal.fileWriteBlockedDisclaimer', 'File write operations detected that cannot be auto approved: {0}', fileWritesList));
} else {
Expand Down
6 changes: 4 additions & 2 deletions ...AgentTools/test/electron-browser/commandLineAnalyzer/commandLineFileWriteAnalyzer.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -110,10 +110,11 @@ import { Workspace } from '../../../../../../../platform/workspace/test/common/t
test('absolute path - /etc - block', () => t('echo hello > /etc/config.txt', 'outsideWorkspace', false, 1));
test('absolute path - /home - block', () => t('echo hello > /home/user/file.txt', 'outsideWorkspace', false, 1));
test('absolute path - root - block', () => t('echo hello > /file.txt', 'outsideWorkspace', false, 1));
test('absolute path - /dev/null - block', () => t('echo hello > /dev/null', 'outsideWorkspace', false, 1));
test('absolute path - /dev/null - allow (null device)', () => t('echo hello > /dev/null', 'outsideWorkspace', true, 1));

// Special cases
test('no workspace folders - block', () => t('echo hello > file.txt', 'outsideWorkspace', false, 1, []));
test('no workspace folders - /dev/null allowed', () => t('echo hello > /dev/null', 'outsideWorkspace', true, 1, []));
test('no redirections - allow', () => t('echo hello', 'outsideWorkspace', true, 0));
test('variable in filename - block', () => t('echo hello > $HOME/file.txt', 'outsideWorkspace', false, 1));
test('command substitution - block', () => t('echo hello > $(pwd)/file.txt', 'outsideWorkspace', false, 1));
Expand All @@ -131,6 +132,7 @@ import { Workspace } from '../../../../../../../platform/workspace/test/common/t
test('pipeline with redirection inside workspace', () => t('cat file.txt | grep "test" > output.txt', 'outsideWorkspace', true, 1));
test('multiple redirections mixed inside/outside', () => t('echo hello > file.txt && echo world > /tmp/file.txt', 'outsideWorkspace', false, 1));
test('here-document', () => t('cat > file.txt << EOF\nhello\nEOF', 'outsideWorkspace', true, 1));
test('error output to /dev/null - allow', () => t('cat missing.txt 2> /dev/null', 'outsideWorkspace', true, 1));
});

suite('no cwd provided', () => {
Expand Down Expand Up @@ -235,7 +237,7 @@ import { Workspace } from '../../../../../../../platform/workspace/test/common/t
});

suite('edge cases', () => {
test('redirection to $null (variable) - block', () => t('Write-Host "hello" > $null', 'outsideWorkspace', false, 1));
test('redirection to $null (PowerShell null device) - allow', () => t('Write-Host "hello" > $null', 'outsideWorkspace', true, 1));
test('relative path with backslashes - allow', () => t('Write-Host "hello" > server\\share\\file.txt', 'outsideWorkspace', true, 1));
test('quoted filename inside workspace - allow', () => t('Write-Host "hello" > "file with spaces.txt"', 'outsideWorkspace', true, 1));
test('forward slashes on Windows (relative) - allow', () => t('Write-Host "hello" > subdir/file.txt', 'outsideWorkspace', true, 1));
Expand Down
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