Run shell commands in a lightweight sandbox (using `bubblewrap`)

sbx.sh

sbx() {
  : '
  sbx - run a command in a minimal bubblewrap sandbox

  Overview:
    - Only the current working directory has read-write permissions and allows persistent changes
    - Host filesystem mounted read-only
    - /proc and /dev are also sandboxed
    - Existing PATH/env are kept, so system + conda tools work normally

  bwrap flags explanation:
    --unshare-all      Unshare all namespaces (mount, pid, ipc, uts, cgroup, user, etc.)
    --share-net        Keep host network (remove if you also want network isolation)
    --new-session      Start a new session; helps avoid TTY injection tricks
    --die-with-parent  Kill the sandbox when the calling shell exits
    --ro-bind / /      Mount host / as read-only root inside the sandbox
    --dev /dev         Create a minimal /dev inside the sandbox
    --proc /proc       Mount a fresh /proc
    --tmpfs /tmp       Use an in-memory /tmp (no writes to host /tmp)
    --bind $PWD $PWD   Bind current directory read-write (real changes allowed here)
    --chdir $PWD       Start the command in the current directory

  Usage:
    sbx <command> [args...]
      sbx ./script.sh
      sbx python run.py --flag
      sbx bash         # to run custom commands; when finished, run `exit`

  NB!
    sbx echo 111 > ../111.txt   # this will bypass the sandbox!

  To install bubblewrap, use:
    Debian/Ubuntu/Mint:   sudo apt install bubblewrap
    Fedora:               sudo dnf install bubblewrap
  '

  if [ "$#" -eq 0 ]; then
    echo "Usage: sbx <command> [args...]" >&2
    return 1
  fi

  local CURRENTDIR="$PWD"

  bwrap \
    --unshare-all --share-net \
    --new-session \
    --die-with-parent \
    --ro-bind / / \
    --dev /dev \
    --proc /proc \
    --tmpfs /tmp \
    --bind "$CURRENTDIR" "$CURRENTDIR" \
    --chdir "$CURRENTDIR" \
    "$@"
}