# FindDuplIDs.ps1
# Script to find objects with duplicates among the following AD attributes:
# userPrincipalName, mail, msRTCSIP-PrimaryUserAddress, proxyAddresses
#
# Copyright (c) 2018-2019 Richard L. Mueller
# Version 1.0 - December 8, 2018
# Version 1.1 - March 1, 2019
#               Quote attribute with lDAPDisplayName msRTCSIP-PrimaryUserAddress.
#
# ----------------------------------------------------------------------
# You have a royalty-free right to use, modify, reproduce, and
# distribute this script file in any way you find useful, provided that
# you agree that the copyright owner above has no warranty, obligations,
# or liability for such use.

# Retrieve all objects where any of the attributes are assigned values.
$Prop = @("userPrincipalName","mail","msRTCSIP-PrimaryUserAddress","proxyAddresses")
$Filter = "(|(userPrincipalName=*)(mail=*)(msRTCSIP-PrimaryUserAddress=*)(proxyAddresses=*))"
$Objects = Get-ADObject -LDAPFilter $Filter -Properties $Prop

# Hash table of IDs. The key is the ID (the value of one of the 4 attributes),
# the value is the DN of the objects with the value (and the attribute names).
# The DNs in the value are separated by the "@" character. It is assumed that
# no distinguished names have this character.
$IDs = @{}

# Loop through the objects.
ForEach ($Object In $Objects)
{
    # Retrieve attribute values.
    $DN = $Object.distinguishedName
    $UPN = $Object.userPrincipalName
    $Mail = $Object.mail
    $PrimAddr = $Object."msRTCSIP-PrimaryUserAddress"
    $ProxyAddrs = $Object.proxyAddresses

    # Check userPrincipalName.
    If ($UPN)
    {
        # Check if this ID has been seen already.
        If ($IDs.ContainsKey($UPN))
        {
            # Duplicate ID, append to value.
            $IDs[$UPN] = $IDs[$UPN] + "@$DN `(UPN)"
        }
        Else
        {
            # Add this ID to the hash table.
            $IDs.Add($UPN, "$DN `(UPN)")
        }
    }
    # Check mail.
    If ($Mail)
    {
        # Only consider value after any colon character.
        $Mail = ($Mail.Split(":"))[-1]
        # Check if this ID has been seen already.
        If ($IDs.ContainsKey($Mail))
        {
            # Check for the current DN.
            If ($IDs[$Mail] -Like "*$DN `(*")
            {
                # Add mail to the list of attributes for this DN.
                $IDs[$Mail] = $IDs[$Mail].Replace("$DN `(","$DN `(mail,")
            }
            Else
            {
                # Duplicate ID, append to value.
                $IDs[$Mail] = $IDs[$Mail] + "@$DN `(Mail)"
            }
        }
        Else
        {
            # Add this ID to the hash table.
            $IDs.Add($Mail, "$DN `(mail)")
        }
    }
    # Check msRTCSIP-PrimaryUserAddress.
    If ($PrimAddr)
    {
        # Only consider value after any colon character.
        $PrimAddr = ($PrimAddr.Split(":"))[-1]
        # Check if this ID has been seen already.
        If ($IDs.ContainsKey($PrimAddr))
        {
            # Check for the current DN.
            If ($IDs[$PrimAddr] -Like "*$DN `(*")
            {
                # Add msRTCSIP-PrimaryUserAddress to the list of attributes for this DN.
                $IDs[$PrimAddr] = $IDs[$PrimAddr].Replace("$DN `(","$DN `(msRTCSIP-PrimaryUserAddress,")
            }
            Else
            {
                # Duplicate ID, append to value.
                $IDs[$PrimAddr] = $IDs[$PrimAddr] + "@$DN `(msRTCSIP-PrimaryUserAddress)"
            }
        }
        Else
        {
            # Add this ID to the hash table.
            $IDs.Add($PrimAddr, "$DN `(msRTCSIP-PrimaryUserAddress)")
        }
    }
    # Check proxyAddresses.
    If ($ProxyAddrs)
    {
        # Check each address in proxyAddresses.
        ForEach ($Addr In $ProxyAddrs)
        {
            # Only consider value after any colon character.
            $Addr = ($Addr.Split(":"))[-1]
            # Check if this ID has been seen already.
            If ($IDs.ContainsKey($Addr))
            {
                # Check for the current DN.
                If ($IDs[$Addr] -Like "*$DN `(*")
                {
                    # Add proxyAddresses to the list of attributes for this DN.
                    $IDs[$Addr] = $IDs[$Addr].Replace("$DN `(","$DN `(proxyAddresses,")
                }
                Else
                {
                    # Duplicate ID, append to value.
                    $IDs[$Addr] = $IDs[$Addr] + "@$DN `(proxyAddresses)"
                }
            }
            Else
            {
                # Add this ID to the hash table.
                $IDs.Add($Addr, "$DN `(proxyAddresses)")
            }
        }
    }
}

# Enumerate all IDs.
ForEach ($ID In $IDs.Keys)
{
    $Values = $IDs[$ID].Split("@")
    If ($Values.Count -gt 1)
    {
        "Duplicate ID: $ID"
        ForEach ($Entry In $Values)
        {
            "    $Entry"
        }
    }
}