feat: sandbox exec calls with bwrap and run container as non-root

nanobot/agent/tools/sandbox.py

@@ -0,0 +1,49 @@
+"""Sandbox backends for shell command execution.
+
+To add a new backend, implement a function with the signature:
+    _wrap_<name>(command: str, workspace: str, cwd: str) -> str
+and register it in _BACKENDS below.
+"""
+
+import shlex
+from pathlib import Path
+
+
+def _bwrap(command: str, workspace: str, cwd: str) -> str:
+    """Wrap command in a bubblewrap sandbox (requires bwrap in container).
+
+    Only the workspace is bind-mounted read-write; its parent dir (which holds
+    config.json) is hidden behind a fresh tmpfs.
+    """
+    ws = Path(workspace).resolve()
+    try:
+        sandbox_cwd = str(ws / Path(cwd).resolve().relative_to(ws))
+    except ValueError:
+        sandbox_cwd = str(ws)
+
+    required  = ["/usr"]
+    optional  = ["/bin", "/lib", "/lib64", "/etc/alternatives",
+                 "/etc/ssl/certs", "/etc/resolv.conf", "/etc/ld.so.cache"]
+
+    args = ["bwrap"]
+    for p in required: args += ["--ro-bind",     p, p]
+    for p in optional: args += ["--ro-bind-try", p, p]
+    args += [
+        "--proc", "/proc", "--dev", "/dev", "--tmpfs", "/tmp",
+        "--tmpfs", str(ws.parent),        # mask config dir
+        "--dir", str(ws),                 # recreate workspace mount point
+        "--bind", str(ws), str(ws),
+        "--chdir", sandbox_cwd,
+        "--", "sh", "-c", command,
+    ]
+    return shlex.join(args)
+
+
+_BACKENDS = {"bwrap": _bwrap}
+
+
+def wrap_command(sandbox: str, command: str, workspace: str, cwd: str) -> str:
+    """Wrap *command* using the named sandbox backend."""
+    if backend := _BACKENDS.get(sandbox):
+        return backend(command, workspace, cwd)
+    raise ValueError(f"Unknown sandbox backend {sandbox!r}. Available: {list(_BACKENDS)}")

nanobot/agent/tools/shell.py

@@ -7,6 +7,7 @@ from pathlib import Path
 from typing import Any
 
 from nanobot.agent.tools.base import Tool
+from nanobot.agent.tools.sandbox import wrap_command
 
 
 class ExecTool(Tool):
@@ -19,10 +20,12 @@ class ExecTool(Tool):
         deny_patterns: list[str] | None = None,
         allow_patterns: list[str] | None = None,
         restrict_to_workspace: bool = False,
+        sandbox: str = "",
         path_append: str = "",
     ):
         self.timeout = timeout
         self.working_dir = working_dir
+        self.sandbox = sandbox
         self.deny_patterns = deny_patterns or [
             r"\brm\s+-[rf]{1,2}\b",          # rm -r, rm -rf, rm -fr
             r"\bdel\s+/[fq]\b",              # del /f, del /q
@@ -84,6 +87,11 @@ class ExecTool(Tool):
         if guard_error:
             return guard_error
 
+        if self.sandbox:
+            workspace = self.working_dir or cwd
+            command = wrap_command(self.sandbox, command, workspace, cwd)
+            cwd = str(Path(workspace).resolve())
+
         effective_timeout = min(timeout or self.timeout, self._MAX_TIMEOUT)
 
         env = os.environ.copy()