#!/usr/bin/env bash
set -uo pipefail

# CASAN Track C-MVP — Runtime sandbox scaffold (C6, V22).
#
# Generated code/tests must not read secrets, reach the network, fork-bomb, write
# outside the workspace, or fill the disk. Full isolation needs a container with
# namespaces/seccomp/network-off (documented below as the production target).
# This scaffold provides two enforceable layers WITHOUT root/Docker:
#   1. Static policy pre-check — refuse to launch a command that matches a known
#      dangerous operation (BLOCK before anything runs). This is the deterministic
#      gate the tests assert on.
#   2. Runtime rlimits (ulimit) — file-size, CPU, and process caps as a backstop,
#      plus the existing wall-clock timeout (tool-exec.sh).
#
# HONEST SCOPE — this is NOT kernel isolation. A determined payload using a
# syscall the static check doesn't model can still act within the rlimits. The
# production requirement is: run inside `docker run --network=none --read-only
# --pids-limit ... --memory ... -v <workspace>:/work:rw`. Do not present this as
# a full sandbox. See TODO(C6-prod) below.
#
# Usage:
#   sandbox-run.sh --workspace <dir> [--max-file-kb N] [--cpu-seconds N]
#                  [--max-procs N] [--timeout N] -- <command...>
# Exit: 2 policy-blocked, 124 timeout, else the command's own exit code.

SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
# shellcheck source=casan-log.sh
source "$SCRIPT_DIR/casan-log.sh"

WORKSPACE="$PWD"
MAX_FILE_KB="${CASAN_SANDBOX_MAX_FILE_KB:-51200}"   # 50 MB default
CPU_SECONDS="${CASAN_SANDBOX_CPU_SECONDS:-30}"
# Process cap is OPT-IN: `ulimit -u` is a per-USER limit, so forcing a low value
# on a busy host makes legitimate commands fail to fork. The fork-bomb static
# check is the real gate; a container --pids-limit is the production backstop.
MAX_PROCS="${CASAN_SANDBOX_MAX_PROCS:-}"
TIMEOUT="${CASAN_SANDBOX_TIMEOUT:-30}"

while [[ "$#" -gt 0 ]]; do
  case "$1" in
    --workspace) WORKSPACE="${2:-}"; shift 2 ;;
    --max-file-kb) MAX_FILE_KB="${2:-}"; shift 2 ;;
    --cpu-seconds) CPU_SECONDS="${2:-}"; shift 2 ;;
    --max-procs) MAX_PROCS="${2:-}"; shift 2 ;;
    --timeout) TIMEOUT="${2:-}"; shift 2 ;;
    --) shift; break ;;
    *) echo "sandbox-run.sh: unknown arg $1" >&2; exit 64 ;;
  esac
done

if [[ "$#" -eq 0 ]]; then
  echo "Usage: sandbox-run.sh --workspace <dir> -- <command...>" >&2
  exit 64
fi

# C6 production form: CASAN_SANDBOX_MODE=container runs under TRUE kernel
# isolation (sandbox-container.sh: --network=none --read-only --pids-limit …).
# Default stays the static-policy + ulimit scaffold so existing behaviour is
# unchanged. Falls back to the scaffold if Docker is unavailable.
if [[ "${CASAN_SANDBOX_MODE:-static}" == "container" ]] && command -v docker >/dev/null 2>&1 && docker info >/dev/null 2>&1; then
  exec "$SCRIPT_DIR/sandbox-container.sh" --workspace "$WORKSPACE" --timeout "$TIMEOUT" -- "$@"
fi

CMD_STR="$*"
low="$(printf '%s' "$CMD_STR" | tr '[:upper:]' '[:lower:]')"

# ── 1. Static policy pre-check ──────────────────────────────────────────────
block() {
  casan_log error sandbox "SANDBOX_BLOCKED reason=$1 cmd=${CMD_STR:0:120}"
  echo "SANDBOX_BLOCKED reason=$1" >&2
  exit 2
}

# Read of SSH / credential material.
printf '%s' "$low" | grep -Eq '(\.ssh/|id_rsa|id_ed25519|authorized_keys|known_hosts|/etc/shadow|/etc/passwd|\.aws/credentials|\.netrc)' \
  && block "read_sensitive_credentials"
# Network egress of any kind (sandboxed code should be offline).
printf '%s' "$low" | grep -Eq '(\bcurl\b|\bwget\b|\bnc\b|\bncat\b|\bscp\b|\bsftp\b|\bssh\b|\btelnet\b|\bftp\b|/dev/tcp/|\bnslookup\b|\bdig\b)' \
  && block "network_egress"
# Fork bomb / uncontrolled process spawning.
printf '%s' "$CMD_STR" | grep -Eq ':\(\)\s*\{\s*:?\s*\|?\s*:?\s*&?\s*\}|\bfork\s*\(\)\s*while|while\s*\(\s*true\s*\)\s*\{\s*fork' \
  && block "fork_bomb"
# Huge-file / disk-fill.
printf '%s' "$low" | grep -Eq '\bdd\b[^\n]*of=|truncate\s+-s\s*[0-9]+\s*[gt]|fallocate\s+-l\s*[0-9]+\s*[gt]|head\s+-c\s*[0-9]+\s*[gt]|\byes\b[^\n]*>' \
  && block "huge_file_or_disk_fill"
# Writes outside the workspace: redirection to an absolute path not under $WORKSPACE, or path traversal.
WS_ABS="$(cd "$WORKSPACE" 2>/dev/null && pwd || echo "$WORKSPACE")"
while read -r target; do
  [[ -z "$target" ]] && continue
  case "$target" in
    /*) [[ "$target" == "$WS_ABS"* || "$target" == /tmp/* || "$target" == /var/folders/* || "$target" == /dev/null ]] || block "write_outside_workspace:$target" ;;
    *"../"*) block "path_traversal_write:$target" ;;
  esac
done < <(printf '%s\n' "$CMD_STR" | grep -oE '>>?[[:space:]]*[^[:space:];|&]+' | sed -E 's/^>>?[[:space:]]*//')

# ── 2. Runtime rlimits + wall-clock timeout ─────────────────────────────────
casan_log debug sandbox "SANDBOX_RUN workspace=$WS_ABS file_kb=$MAX_FILE_KB cpu=$CPU_SECONDS procs=$MAX_PROCS timeout=$TIMEOUT"
(
  ulimit -f "$((MAX_FILE_KB * 2))" 2>/dev/null || true   # ulimit -f is in 512-byte blocks
  ulimit -t "$CPU_SECONDS" 2>/dev/null || true
  [[ -n "$MAX_PROCS" ]] && { ulimit -u "$MAX_PROCS" 2>/dev/null || true; }
  cd "$WS_ABS" 2>/dev/null || true
  exec "$SCRIPT_DIR/tool-exec.sh" "$TIMEOUT" -- "$@"
)
rc=$?
exit "$rc"

# TODO(C6-prod): replace the rlimit backstop with true isolation:
#   docker run --rm --network=none --read-only --pids-limit=$MAX_PROCS \
#     --memory=512m --cpus=1 -v "$WORKSPACE":/work:rw -w /work <image> <cmd>
# and/or bubblewrap/nsjail on Linux CI. Track as a Track-C production task.