bwclaude.bash

#!/bin/bash
set -euo pipefail

if [ $# -eq 0 ]; then
  echo "Usage: $(basename "$0") <command> [args...]" >&2
  exit 1
fi

# Re-exec inside pasta netns
# When pasta calls us back, SANDBOX_STAGE=nft
if [ "${SANDBOX_STAGE:-}" = "nft" ]; then
  # We're now inside pasta's netns with CAP_NET_ADMIN.
  # Set up nftables before dropping into bwrap.

  ANTHROPIC_V4="160.79.104.0/23"
  ANTHROPIC_V6="2607:6bc0::/48"

  nft -f - <<EOF
table inet filter {
  chain output {
    type filter hook output priority 0; policy drop;
    oifname "lo" accept
    udp dport 53 accept
    tcp dport 53 accept
    ip daddr { 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, 169.254.0.0/16 } accept
    ip6 daddr { ::1/128, fe80::/10, fd00::/8 } accept
    ip daddr $ANTHROPIC_V4 accept
    ip6 daddr $ANTHROPIC_V6 accept
    reject with icmpx admin-prohibited
  }
}
EOF

  # ── Read-only paths to expose under $HOME ──
  RO_HOME_PATHS=(
    .cargo
    .local/bin
    .local/share
    .config/git
    .gitconfig
    .bashrc
    .profile
    .subversion
  )

  # ── Read-write paths under $HOME ──
  RW_HOME_PATHS=(
    .claude
    .claude.json
    .config/claude
    .rustup
    .local/share/pnpm
  )

  # ── Build bwrap args ──
  args=(
    --ro-bind / /
    --tmpfs "$HOME"
    --bind "$SANDBOX_CWD" "$SANDBOX_CWD"
    --bind "$SANDBOX_CWD" "/tmp/project"
    --dev /dev
    --proc /proc
    --tmpfs /tmp
    --unshare-all
    --share-net
    --die-with-parent
  )

  for p in "${RO_HOME_PATHS[@]}"; do
    src="$HOME/$p"
    [ -e "$src" ] && args+=(--ro-bind "$src" "$src")
  done

  for p in "${RW_HOME_PATHS[@]}"; do
    src="$HOME/$p"
    [ -e "$src" ] && args+=(--bind "$src" "$src")
  done

  exec bwrap "${args[@]}" \
    --uid "$SANDBOX_UID" --gid "$SANDBOX_GID" \
    --setenv USER "$USER" \
    --setenv HOME "$HOME" \
    --setenv RUSTUP_TOOLCHAIN "nightly" \
    "$@"
fi

# Guard against running from inside $HOME
if [[ "$(pwd)" == "$HOME" ]]; then
  echo "Error: don't run this from \$HOME itself, it'll punch through the tmpfs" >&2
  exit 1
fi

export SANDBOX_STAGE=nft
export SANDBOX_CWD="$(pwd)"
export SANDBOX_UID="$(id -u)"
export SANDBOX_GID="$(id -g)"
exec osc11wrap pasta --config-net -- "$0" "$@"