nuageinit: fix command injection and related issues

- Add shell_escape() helper to safely escape shell arguments
- Apply shell_escape to all user-controlled values in shell commands:
  adduser (usershow, useradd, lock, primary_group, groups)
  addgroup (groupshow, groupadd, members)
  exec_change_password (usermod)
  settimezone (tzsetup root and timezone)
  install_package (pkg package names)
- Escape double quotes in hostname when writing rc.conf.d/hostname
- Add missing 'local' declaration for resolvconf_command in nameservers()
- Escape interface name in resolvconf -a command
- Change open_resolvconf_conf() from 'w' to 'a' mode to prevent
  data loss when nameservers() is called multiple times
- Clean up stale resolvconf.conf at the start of each boot
  (skip on postnet to preserve config written by first call)

MFC After: 1 day

(cherry picked from commit 8b70a203be10411c560ed303ab25713d70b316e9)

0 files changed, 0 insertions, 0 deletions