#!/bin/bash
# @file tmux-member.sh
# @description Server mode, one Linux user per account (S3): installed as
# /opt/agenthub/libexec/tmux-member, the one tmux the host may run AS a
# member (sudoers). Called as `tmux-member -S <socket> <tmux args…>`, it runs
# the args with the binary of the tmux server already listening on that
# socket (`/proc/<pid>/exe`, which still runs after an upgrade replaced the
# file), else with TMUX_BIN from /etc/agenthub/server.conf (no server yet:
# this call starts one, on the installed version). A client must match its
# server: a tmux 3.8 client asking a 3.6 server kept it at 100% CPU.
#
# It runs as the member and execs only a process THEY own (under hidepid they
# see no other), so it can run nothing they could not run themselves.
# @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
set -u
bin=$(sed -n 's/^TMUX_BIN=//p' /etc/agenthub/server.conf 2>/dev/null | head -n 1)
[[ "$bin" == /* ]] || { echo "tmux-member: no TMUX_BIN in /etc/agenthub/server.conf" >&2; exit 2; }
if [ "${1:-}" = -S ] && [ -n "${2:-}" ]; then
  # /proc/net/unix: Num RefCount Protocol Flags Type St Inode Path; 00010000 = listening.
  inode=$(awk -v s="$2" '$4 == "00010000" && $8 == s { print $7; exit }' /proc/net/unix 2>/dev/null)
  if [ -n "$inode" ]; then
    for d in /proc/[0-9]*; do
      [ -O "$d" ] || continue
      read -r comm <"$d/comm" 2>/dev/null || continue
      [[ "$comm" == tmux* ]] || continue
      for fd in "$d"/fd/*; do
        if [ "$(readlink "$fd" 2>/dev/null)" = "socket:[$inode]" ] && [ -x "$d/exe" ]; then
          exec "$d/exe" "$@"
        fi
      done
    done
  fi
fi
exec "$bin" "$@"