Inspired by: Description and guidelines on creating system service agent accounts on Mac OS X (Tiger) and HiddenAdminCreate

Use at your own risk!

1. create a system service agent account

#!/bin/bash

if [[ "$(/usr/bin/whoami)" != "root" ]]; then printf '\nMust be run as root!\n\n'; exit 1; fi

OPATH=$PATH
export PATH=/usr/bin:/usr/sbin:/bin:/sbin

OIFS=$IFS
export IFS=$' \t\n'

printf '\n\e[1mYou are going to create a system service agent account!\e[m\n\n'

declare sudo=/usr/bin/sudo dscl=/usr/bin/dscl


# first name 

printf "\e[1mEnter first name\e[m: "
read fn

# no spaces in names
if [[ -z "$(printf -- "$fn" | /usr/bin/grep -Eo "^[^[:space:]]+$")" ]]; then
   printf '\nUse a name without spaces! \nPlease, try again!\n\n'
   exit 1
fi

# name must not begin with a number
if [[ -n "$(printf -- "$fn" | /usr/bin/grep -E "^[[:digit:]]")" ]]; then
   printf '\nName must not begin with a number! \nPlease, try again!\n\n'
   exit 1
fi


# make sure the user name is unique
new_user="$(/usr/bin/dscl . -search /Users name "$fn" 2>/dev/null)"

if [[ -z "$new_user" ]]; then
  new_user="$fn"               
else
  printf "\nUser name already exists: $fn \nPlease, modify your name and try it again\x21\n\n"
  exit 1
fi 


# make sure the agent's primary group name is unique 
# note: the agent's primary group name is also based on the first name!

new_group="$(/usr/bin/dscl . -search /Groups name "$fn")"

if [[ -z "$new_group" ]]; then
  new_group="$fn"             
else
  printf "\nThe agent's primary group name already exists: $fn\x21 \nPlease, try again\x21\n\n"
  exit 1
fi 


# last name

printf '\nNote: The \e[1mlast name\e[m is \e[1moptional\e[m and defaults to "agent" if you just press !\n'
printf "\e[1mEnter last name\e[m: "
read ln

if [[ -z "$ln" ]]; then ln="agent"; fi

# no spaces in names
if [[ -z "$(printf -- "$ln" | /usr/bin/grep -Eo "^[^[:space:]]+$")" ]]; then
   printf '\nUse a name without spaces! \nPlease, try again!\n\n'
   exit 1
fi

# name must not begin with a number
if [[ -n "$(printf -- "$ln" | /usr/bin/grep -E "^[[:digit:]]")" ]]; then
   printf '\nName must not begin with a number! \nPlease, try again!\n\n'
   exit 1
fi


# user shell

printf '\nNote: The \e[1muser shell\e[m is \e[1moptional\e[m and defaults to "/usr/bin/false" if you just press !\n'
printf "\e[1mEnter user shell\e[m: "
read sh

if [[ -z "$sh" ]]; then sh="/usr/bin/false"; fi

# test if user shell exists
if [[ ! -e "$sh" ]]; then
   printf "\nUser shell does not exist: $sh\n\n"
   exit 1
fi


# home directory

printf '\nNote: The \e[1mhome directory\e[m is \e[1moptional\e[m and defaults to "/private/var/empty" if you just press !\n'
printf "\e[1mEnter home directory\e[m: "
read hd

if [[ -z "$hd" ]]; then 
   hd="/private/var/empty"
elif [[ "${hd:0:1}" != '/' ]]; then
   printf '\nThe home directory path does not begin with a slash "/".\nPlease, try again!\n\n'
   exit 1
elif [[ -e "$hd" ]]; then
   printf "\nHome directory already exists: $hd \nPlease, try again\x21\n\n"
   exit 1
fi

hd=${hd%/}      # remove a trailing slash character "/" if necessary



# get unique id numbers (uid, gid)
unset -v new_uid new_gid i
declare -i new_uid=0 new_gid=0 i=100

while [[ $i -lt 500 ]]; do      # try to get $new_uid and $new_gid between 100 and 500
   i=$[i+1]
   if [[ -z "$(/usr/bin/dscl . -search /Users uid $i)" ]] && [[ -z "$(/usr/bin/dscl . -search /Groups gid $i)" ]]; then
      new_uid=$i
      new_gid=$i
      break
   fi
done


if [[ $new_uid -eq 0 ]] || [[ $new_gid -eq 0 ]]; then     # get $new_uid and $new_gid greater than 500
   i=500
   idvar=0

   while [[ $idvar -eq 0 ]]; do 
      i=$[i+1]
      if [[ -z "$(/usr/bin/dscl . -search /Users uid $i)" ]] && [[ -z "$(/usr/bin/dscl . -search /Groups gid $i)" ]]; then
         new_uid=$i
         new_gid=$i
         idvar=1
         #break
      fi
   done

fi


if [[ $new_uid -eq 0 ]] || [[ $new_gid -eq 0 ]]; then printf 'Getting unique id numbers (uid, gid) failed!\n'; exit 1; fi



# check once again ...

if [[ $new_uid -eq $new_gid ]] && [[ "$new_user" == "$fn" ]] && [[ "$new_group" == "$fn" ]]; then

# create home directory
if [[ "$hd" != "/private/var/empty" ]]; then
   $sudo /bin/mkdir -p "$hd"
fi

# create the agent's primary group
$sudo /usr/sbin/dseditgroup -o create -r "$fn $ln" -i $new_gid "$new_group"
$sudo $dscl  . -append "/Groups/$new_group" passwd "*"

# create the system service agent
$sudo $dscl . -create /Users/$new_user
$sudo $dscl . -append /Users/$new_user RealName "$fn $ln"
$sudo $dscl . -append /Users/$new_user uid $new_uid
$sudo $dscl . -append /Users/$new_user gid $new_gid
$sudo $dscl . -append /Users/$new_user shell "$sh"
$sudo $dscl . -append /Users/$new_user home "$hd"
$sudo $dscl . -create /Users/$new_user passwd "*"

$sudo $dscl  . -append "/Groups/$new_group" GroupMembership "$new_user"    # add new agent to the agent's primary group
#$sudo /usr/sbin/dseditgroup -o edit -a "$new_group" -t user "$new_user"

else

   printf "\nConfiguration of system service agent account: $fn failed\x21 \nPlease, try again\x21\n\n"
   exit 1

fi

# create further subdirectories if necessary
#if [[ "$hd" != "/private/var/empty" ]]; then
#
#if [[ "$new_user" == "clamavadmin" ]]; then
#   # additional subdirectories for the clamavadmin system service agent account
#   $sudo /bin/mkdir  -p "$hd"/log
#   $sudo /usr/bin/touch "$hd"/log/clamd.log
#   $sudo /bin/mkdir  -p "$hd"/tmp
#   $sudo /bin/mkdir  -p "$hd"/share/clamav
#   $sudo /usr/sbin/chown -R $new_user:$new_user "$hd"
#   $sudo /bin/chmod -R 750 "$hd"
#fi
#
#fi


printf "\nSystem service agent account:  \e[1m$fn\e[m  successfully created\x21\n\n"

export IFS=$OIFS
export PATH=$OPATH

exit 0


#---------------------------

# test
dscl . list /Users
dscl . -read /Users/

dscl . list /Groups
dscl . -read /Groups/
dscl . list /Groups GroupMembership

2. delete a system service agent account

#!/bin/bash


if [[ "$(/usr/bin/whoami)" != "root" ]]; then printf '\nMust be run as root!\n\n'; exit 1; fi

OPATH=$PATH
export PATH=/usr/bin:/usr/sbin:/bin:/sbin

OIFS=$IFS
export IFS=$' \t\n'

declare sudo=/usr/bin/sudo


printf "\n\e[1mDelete system service agent account\e[m: "
read agent

if [[ -z "$agent" ]]; then printf '\nNo name for system service agent specified! Please, try again!\n\n'; exit 1; fi

# make sure the agent exists
agenttest="$(/usr/bin/dscl . -search /Users name "$agent")"

if [[ -z "$agenttest" ]]; then printf "\nThe system service agent does not exist: $agent\n\n"; exit 1; fi 


# find the agent's home directory
home=$(/usr/bin/dscl . -read /Users/$agent home | awk -F ': ' '{ print $NF; }' )


# get the agent's group memberships
groups_of_agent="$(/usr/bin/id -Gn $agent)"

# delete the agent's group memberships
if [[ $? -eq 0 ]] && [[ -n "$(/usr/bin/dscl . -search /Groups GroupMembership "$agent")" ]]; then

   for group in $groups_of_agent; do
      $sudo /usr/bin/dscl . -delete "/Groups/$group"  GroupMembership "$agent"
      #$sudo /usr/sbin/dseditgroup -o edit -d "$agent" -t user "$group"           
   done

fi


# delete the agent's primary group
if [[ -n "$(/usr/bin/dscl . -search /Groups name "$agent")" ]]; then
   $sudo /usr/sbin/dseditgroup -o delete "$agent"
fi

# if the agent's primary group has not been deleted ...
if [[ -n "$(/usr/bin/dscl . -search /Groups name "$agent")" ]]; then
printf "
   \e[1mWarning\e[m:
   The group memberships of the system service agent \e[1m$agent\e[m have been deleted\x21
   groups_of_agent: $groups_of_agent
   The agent's primary group \e[1m$agent\e[m, however, has not been deleted\x21
   Please, try again\x21
   Exiting ...\n
"
  exit 1
fi


# find the GeneratedUID of the agent and remove the password hash file 
# from /private/var/db/shadow/hash/
# sudo ls -a /private/var/db/shadow/hash
# sudo ls -l /private/var/db/shadow/hash/

guid="$(/usr/bin/dscl . -read "/Users/$agent" GeneratedUID | /usr/bin/awk '{print $NF;}')"

if [[ -f "/private/var/db/shadow/hash/$guid" ]]; then
   $sudo /bin/rm -f /private/var/db/shadow/hash/$guid
fi


# delete the agent
$sudo /usr/bin/dscl . -delete "/Users/$agent"

# make a backup
if [[ -d "$home" ]] && [[ "$home" != "/private/var/empty" ]]; then
   $sudo /usr/bin/ditto -rsrc -c -k "$home" "${home}-archive-$(/bin/date).zip"
fi

# remove the agent's home directory
if [[ -d "$home" ]] && [[ "$home" != "/private/var/empty" ]]; then
   $sudo /bin/rm -rf "$home"
fi


printf "\nSystem service agent account:  \e[1m$agent\e[m  successfully deleted\x21\n\n"


export IFS=$OIFS
export PATH=$OPATH

exit 0