Jason Woltje
7f6464bbda
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Co-authored-by: Jason Woltje <jason@diversecanvas.com> Co-committed-by: Jason Woltje <jason@diversecanvas.com>
59 lines
2.2 KiB
TypeScript
59 lines
2.2 KiB
TypeScript
import path from 'node:path';
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import fs from 'node:fs';
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/**
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* Resolves a user-provided path and verifies it is inside the allowed sandbox directory.
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* Throws SandboxEscapeError if the resolved path is outside the sandbox.
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*
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* Uses realpathSync to resolve symlinks in the sandbox root. The user-supplied path
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* is checked for containment AFTER lexical resolution but BEFORE resolving any symlinks
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* within the user path — so symlink escape attempts are caught too.
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*
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* @param userPath - The path provided by the agent (may be relative or absolute)
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* @param sandboxDir - The allowed root directory (already validated on session creation)
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* @returns The resolved absolute path, guaranteed to be within sandboxDir
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*/
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export function guardPath(userPath: string, sandboxDir: string): string {
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const resolved = path.resolve(sandboxDir, userPath);
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const sandboxResolved = fs.realpathSync.native(sandboxDir);
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// Normalize both paths to resolve any symlinks in the sandbox root itself.
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// For the user path, we check containment BEFORE resolving symlinks in the path
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// (so we catch symlink escape attempts too — the resolved path must still be under sandbox)
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if (!resolved.startsWith(sandboxResolved + path.sep) && resolved !== sandboxResolved) {
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throw new SandboxEscapeError(userPath, sandboxDir, resolved);
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}
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return resolved;
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}
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/**
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* Validates a path without resolving symlinks in the user-provided portion.
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* Use for paths that may not exist yet (creates, writes).
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*
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* Performs a lexical containment check only using path.resolve.
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*/
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export function guardPathUnsafe(userPath: string, sandboxDir: string): string {
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const resolved = path.resolve(sandboxDir, userPath);
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const sandboxAbs = path.resolve(sandboxDir);
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if (!resolved.startsWith(sandboxAbs + path.sep) && resolved !== sandboxAbs) {
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throw new SandboxEscapeError(userPath, sandboxDir, resolved);
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}
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return resolved;
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}
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export class SandboxEscapeError extends Error {
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constructor(
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public readonly userPath: string,
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public readonly sandboxDir: string,
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public readonly resolvedPath: string,
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) {
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super(
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`Path escape attempt blocked: "${userPath}" resolves to "${resolvedPath}" which is outside sandbox "${sandboxDir}"`,
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);
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this.name = 'SandboxEscapeError';
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}
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}
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