Path safety and sandboxing

Now that the agent can read and write files, what stops it from reading /etc/passwd or writing to /usr/bin? Nothing, unless we add a boundary. The safe_path() function resolves any path and checks it stays within the workspace directory. Path traversal attacks like ../../etc/passwd get caught.

03-tool-design/agent.py

python

WORKDIR = Path.cwd()

def safe_path(p: str) -> Path:
    """Resolve path and verify it stays within workspace."""
    path = (WORKDIR / p).resolve()
    if not path.is_relative_to(WORKDIR):
        raise ValueError(f"Path escapes workspace: {p}")
    return path

Every file tool calls safe_path() before touching the filesystem. Three lines that prevent workspace escape.

Quiz: Quiz

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