#!/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="Username"
SVC_ACCOUNT_PASS="Password"
DOMAIN="my.domain"
LDAP_SERVER="dc.my.domain:389"
SEARCH_BASE="OU=Users,DC=My,DC=Domain"

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 ${BASE64_DECODED} | hexdump -e '1/1 " %02X"'))
    OBJECTGUID="${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 -E pr=1000/noprompt -o ldif-wrap=no -x -D ${SVC_ACCOUNT_NAME}@$DOMAIN -w ${SVC_ACCOUNT_PASS} -b "${SEARCH_BASE}" \
-s sub -a always "(objectClass=user)" "sAMAccountName" "objectGUID")

i=1
s=1
declare -a RESULT_ARRAY
while IFS= read -r line; do
    # If we find an empty line, then we increase the counter (i),
    # set the flag (s) to one, and skip to the next line
    [[ $line == "" ]] && ((i++)) && s=1 && continue

    # If the flag (s) is zero, then we are not in a new line of the block
    # so we set the value of the array to be the previous value concatenated
    # with the current line
    [[ $s == 0 ]] && RESULT_ARRAY[$i]="${RESULT_ARRAY[$i]}
$line" || {
            # Otherwise we are in the first line of the block, so we set the value
            # of the array to the current line, and then we reset the flag (s) to zero
            RESULT_ARRAY[$i]="$line"
            s=0;
    }
done <<< "$RESULT"

for USER in "${RESULT_ARRAY[@]}"; do
    USER_DN=$(echo "$USER" | grep "dn:")
    USER_GUID_BASE64=$(echo "$USER" | 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=$(echo "$OBJECTGUID" | awk -F "-" '{print $1}')
    # Now convert this to decimal
    GUID_32_DEC=$(echo "ibase=16; $GUID_32" | bc)
    if [ $GUID_32_DEC -gt 2147483647 ]; then
        # Get the first character of our 32bit GUID
        FIRST_CHAR=${GUID_32:0:1}
        # Use the below table to replace the first character with number it represents. ie: A=2
        case $FIRST_CHAR in
            A)
                NUMBER=2 ;;
            B)
                NUMBER=3 ;;
            C)
                NUMBER=4 ;;
            D)
                NUMBER=5 ;;
            E)
                NUMBER=6 ;;
            F)
                NUMBER=7 ;;
            9)
                NUMBER=1 ;;
            8)
                NUMBER=0 ;;
            *)
        esac
        # Now lets replace the first character with our new number
        A=$(echo $GUID_32 | cut -c2-)
        NEW_32_GUID="${NUMBER}${A}"
        GUID_32_DEC=$(echo "ibase=16; $NEW_32_GUID" | bc)
    fi
    # Echo our output
    USERNAME=$(echo $USER_DN | awk -F "dn:" '{print $2}')
    echo "$USERNAME,$GUID_32_DEC"
    echo "$USERNAME,$GUID_32_DEC" >> users_with_UID.csv
done