#get-dmarcinfo
#
# Script to collect the domains of DMARC recipient mailaddresses from a list of domains
# Get the target Domain as parameter or fom a textfile and query them with resolve-dnsname
# parse the results and extract the SMTP-Domain of the Addresses
# Generate a hashtable with the domains for further processing
#
# (c) 2025 Frank Carius  https://www.msxfaq.de


param (
    [Parameter(Mandatory = $true, Position = 0,ValueFromPipeline = $true,HelpMessage = "Domainname or list of domains to query for DMARC records")]
    [string]$Domain
)


begin {
    Write-Verbose "Starting DMARC information retrieval for domains: $($Domains -join ', ')"
    $count= 0
    if (-not $Domain) {
        Write-Error "No domains provided. Please specify at least one domain."
        return
    }

}

process {
    $count++
    Write-Host "Domain ($count): $domain"
    try {
        $dmarcRecord = Resolve-DnsName -Name "_dmarc.$domain" -Type TXT -ErrorAction Stop
        foreach ($record in $dmarcRecord) {
            if ($record.Strings -match "v=DMARC1") {
                $dmarcInfo = [pscustomobject][ordered] @{
                    Domain = $domain
                    Record = $record.Strings
                    Policy = $null
                    SMTPDomain = $null
                }
                $record.Strings.split(";").trim() | ForEach-Object {
                    Write-Verbose "Processing record: $_"
                    if ($_.startswith("p=")) {
                        $dmarcinfo.Policy = $_.replace("p=","").trim()
                        Write-Verbose "Found policy: $Policy"   
                    }
                    if ($_.startswith("rua=")) {
                        Write-Verbose "Found rua tag: $_"
                        foreach ($entry in ($_.replace("rua=","").split(","))) {
                            Write-Verbose "Processing entry: $entry"
                            if ($entry.startswith("mailto:")) {
                                Write-Verbose "Found mailto entry: $entry"
                                $smtpDomain = $entry.split("@")[1]
                                $dmarcInfo.SMTPDomain = $smtpDomain
                                $dmarcInfo
                            }
                        }
                    }
                }
            }
        }
    } catch {
        Write-Warning "Failed to resolve DMARC record for domain '$domain': $_"
    }


}

end {
    Write-Verbose "DMARC information retrieval completed."
}