# P8-016: Security — Tool Path Hardening + Sandbox Escape Prevention

## Status: in-progress

## Branch: feat/p8-016-tool-hardening

## Issue: #169

## Scope

Harden file, git, and shell tool factories so no path operation escapes `sandboxDir`.

## Files to Create

- `apps/gateway/src/agent/tools/path-guard.ts` (new)
- `apps/gateway/src/agent/tools/path-guard.test.ts` (new)

## Files to Modify

- `apps/gateway/src/agent/tools/file-tools.ts`
- `apps/gateway/src/agent/tools/git-tools.ts`
- `apps/gateway/src/agent/tools/shell-tools.ts`

## Analysis

### file-tools.ts

- Has existing `resolveSafe()` function but uses weak containment check (relative path)
- Replace with `guardPath` (for reads/lists on existing paths) and `guardPathUnsafe` (for writes)
- Error pattern: return `{ content: [{ type: 'text', text: 'Error: ...' }], details: undefined }`

### git-tools.ts

- Has `clampCwd()` that silently falls back to sandbox root on escape attempt
- Replace with strict `guardPath` that throws SandboxEscapeError, caught and returned as error
- Also need to guard the `path` parameter in `git_diff`

### shell-tools.ts

- Has `clampCwd()` same silent-fallback approach
- Replace with strict `guardPath` that throws SandboxEscapeError

## Key Design Decisions

- `guardPath`: uses `realpathSync.native` to resolve symlinks, requires path to exist
- `guardPathUnsafe`: lexical only (`path.resolve`), for paths that may not exist yet
- Both throw `SandboxEscapeError` on escape attempt
- Callers catch and return error result

## Verification

- pnpm typecheck
- pnpm lint
- pnpm format:check
- pnpm test
