feat(gateway): tool path hardening + sandbox escape prevention (P8-016) (#177)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

apps/gateway/src/agent/tools/file-tools.ts

@@ -1,20 +1,7 @@
 import { Type } from '@sinclair/typebox';
 import type { ToolDefinition } from '@mariozechner/pi-coding-agent';
 import { readFile, writeFile, readdir, stat } from 'node:fs/promises';
-import { resolve, relative, join } from 'node:path';
-
-/**
- * Safety constraint: all file operations are restricted to a base directory.
- * Paths that escape the sandbox via ../ traversal are rejected.
- */
-function resolveSafe(baseDir: string, inputPath: string): string {
-  const resolved = resolve(baseDir, inputPath);
-  const rel = relative(baseDir, resolved);
-  if (rel.startsWith('..') || resolve(resolved) !== resolve(join(baseDir, rel))) {
-    throw new Error(`Path escape detected: "${inputPath}" resolves outside base directory`);
-  }
-  return resolved;
-}
+import { guardPath, guardPathUnsafe, SandboxEscapeError } from './path-guard.js';
 
 const MAX_READ_BYTES = 512 * 1024; // 512 KB read limit
 const MAX_WRITE_BYTES = 1024 * 1024; // 1 MB write limit
@@ -37,8 +24,14 @@ export function createFileTools(baseDir: string): ToolDefinition[] {
       const { path, encoding } = params as { path: string; encoding?: string };
       let safePath: string;
       try {
-        safePath = resolveSafe(baseDir, path);
+        safePath = guardPath(path, baseDir);
       } catch (err) {
+        if (err instanceof SandboxEscapeError) {
+          return {
+            content: [{ type: 'text' as const, text: `Error: ${err.message}` }],
+            details: undefined,
+          };
+        }
         return {
           content: [{ type: 'text' as const, text: `Error: ${String(err)}` }],
           details: undefined,
@@ -99,8 +92,14 @@ export function createFileTools(baseDir: string): ToolDefinition[] {
       };
       let safePath: string;
       try {
-        safePath = resolveSafe(baseDir, path);
+        safePath = guardPathUnsafe(path, baseDir);
       } catch (err) {
+        if (err instanceof SandboxEscapeError) {
+          return {
+            content: [{ type: 'text' as const, text: `Error: ${err.message}` }],
+            details: undefined,
+          };
+        }
         return {
           content: [{ type: 'text' as const, text: `Error: ${String(err)}` }],
           details: undefined,
@@ -151,8 +150,14 @@ export function createFileTools(baseDir: string): ToolDefinition[] {
       const target = path ?? '.';
       let safePath: string;
       try {
-        safePath = resolveSafe(baseDir, target);
+        safePath = guardPath(target, baseDir);
       } catch (err) {
+        if (err instanceof SandboxEscapeError) {
+          return {
+            content: [{ type: 'text' as const, text: `Error: ${err.message}` }],
+            details: undefined,
+          };
+        }
         return {
           content: [{ type: 'text' as const, text: `Error: ${String(err)}` }],
           details: undefined,