AD Plugin UID calculation from ObjectGUID

convert.sh

#!/bin/bash

#
# Author:   Calum Hunter
# Date:     28/11/2016
# Version:  1.0
# Purpose:  To generate a Mac UID from the objectGUID attribute
#           (GeneratedUID) in AD. 
#           This uses the same method that the Apple
#           AD Plugin uses
#

## Start by loading up our ldap query variables
SVC_ACCOUNT_NAME="srv_acct"
SVC_ACCOUNT_PASS="password"
DOMAIN="domain.com"
LDAP_SERVER="domain.com"
SEARCH_BASE="dc=domain,dc=com"
SAM_ACCOUNTNAME=$1

DECODE_BASE64(){
    # This function takes the encoded output from ldapsearch and decodes it 
    # It then needs to be "hex-dumped" in order to get it into regular text
    # So that we can work with it
    OBJECT_ID="$1"
    BASE64_DECODED=$(echo $OBJECT_ID | base64 -D)
    G=($(echo ${BASE64_DECODED} | hexdump -e '16/1 " %02X"'))
    OBJECTGUID="${G[3]}${G[2]}${G[1]}${G[0]}-${G[5]}${G[4]}-${G[7]}${G[6]}-${G[8]}${G[9]}-${G[10]}${G[11]}${G[12]}${G[13]}${G[14]}${G[15]}"
}

# Search LDAP for our user account
RESULT=$(ldapsearch -LLL -H ldap://$LDAP_SERVER -o ldif-wrap=no -x -D ${SVC_ACCOUNT_NAME}@$DOMAIN -w ${SVC_ACCOUNT_PASS} -b "${SEARCH_BASE}" "(sAMAccountName=$SAM_ACCOUNTNAME)" "objectGUID")


# Get our user DN and objectGUID from the result above.
USER_DN=$(echo "$RESULT" | grep "dn:")
USER_GUID_BASE64=$(echo "$RESULT" | awk -F "::" '/objectGUID/ {print $2}')

# Get our GeneratedUID from LDAPSEARCH by decoding and hex dumping it
DECODE_BASE64 "$USER_GUID_BASE64"

# Now lets get the first 32 bits of our GUID
GUID_32=${OBJECTGUID:0:8}
echo $GUID_32

# Now convert this to decimal 
# This should ensour that if this is greater than the largest decimal figure allowed for a mac UID (32Bit Integer) 
# It'll do some magic
GUID_32_DEC=$(echo $(($(echo "ibase=16; $GUID_32" | bc) & 2147483647)))

# Echo our output
echo "User: $(echo $USER_DN | awk -F "dn:" '{print $2}')"
echo "ObjectGUID: $OBJECTGUID"
echo "Mac UID: $GUID_32_DEC"