CertBot manual auth hook for Azure DNS using Azure CLI

certbot-authhook-az-cli-annotated.sh

#!/bin/bash

# The hook supports 2 actions, 'create' and 'delete', passed as the first argument.
# When 'create' is passed in, a validation TXT record is added, 
# 'delete' cleans up that record after validation
ACTION=$1
# The second the name of the Azure Account that contains the DNS Zone Resource
AZ_ACCOUNT=$2
echo $AZ_ACCOUNT
# set the name of the Azure Resource Group that contains the DNS Zone Resource
AZ_GROUP=$3
echo $AZ_GROUP
# the name of the DNS Zone in Azure
AZ_ZONE=$4
echo $AZ_ZONE

AZ_DOMAIN=$CERTBOT_DOMAIN
AZ_RECORD_SET_VALUE=$CERTBOT_VALIDATION

# handle requestts for wildcard DNS entry, 
if [ ${AZ_DOMAIN:0:2} == "*." ]; then AZ_DOMAIN=${AZ_DOMAIN:2}; fi

AZ_RECORD_SET="_acme-challenge.${AZ_DOMAIN:0:(($(echo -n $AZ_DOMAIN | wc -m)-$(echo -n $AZ_ZONE | wc -m)-1))}"

if [ "$ACTION" == "create" ]; then
  az network dns record-set txt add-record -g "${AZ_GROUP}" -z "${AZ_ZONE}" --record-set-name "${AZ_RECORD_SET}" -v="${AZ_RECORD_SET_VALUE}"
  sleep 30;
fi

if [ "$ACTION" == "delete" ]; then
  az network dns record-set txt delete -g "${AZ_GROUP}" -z "${AZ_ZONE}" -n "${AZ_RECORD_SET}";
fi

have you seen the https://noobient.com/2018/04/10/free-wildcard-certificates-using-azure-dns-lets/