"Certificate does not contain any CA certificate" error when I create a SSL profile on Azure Application Gateway - azure-web-app-service

Question

Let me explain more about the scenario.
I have a web application that is hosted on an Azure App Service Plan.
I created two certificates "Root" and "Child" with the blow command:
Generate root cert:
$pwd = ConvertTo-SecureString -String "123" -Force -AsPlainText
$filepath = 'C:\Users\Desktop\certificates\'
$rootcert = New-SelfSignedCertificate -CertStoreLocation Cert:\LocalMachine\My -Subject "IdentityServerCN"-Provider "Microsoft Strong Cryptographic Provider"-HashAlgorithm "SHA512"-NotAfter (Get-Date).AddYears(5) -KeyUsageProperty All -KeyUsage CertSign, CRLSign, DigitalSignature
Export-PfxCertificate -cert ('Cert:\LocalMachine\My\' + $rootcert.thumbprint) -FilePath ($filepath+'IdentityServerCertificate.pfx')  -Password $pwd
 
Generate child cert:
$pwd = ConvertTo-SecureString -String "123" -Force -AsPlainText
$scope = "app"
$env = "develoepr"
$filepath = 'C:\Users\Desktop\certificates\test\'
$certname = $scope + "_"+ $env
$childcert = New-SelfSignedCertificate -CertStoreLocation Cert:\LocalMachine\My -Subject "IdentityServerCN"-Provider "Microsoft Strong Cryptographic Provider"-HashAlgorithm "SHA512"-NotAfter (Get-Date).AddYears(5) -Signer $rootcert  -FriendlyName $certname
Export-PfxCertificate -cert ('Cert:\LocalMachine\My\' + $childcert.thumbprint) -FilePath ($filepath + $certname+'.pfx') -Password $pwd
When I directly open the web app URL https://app-test-platform.azurewebsites.net/index.html the application request a certificate. I selecet the child certificate and then the application opened.
Now, I want to move this app behind the Azure Application Gateway and I configure all settings (backend, listeners and etc). Based on this document for this solution I need SSL Profile. First of all, I need to export the trusted CA certificate chain (this document). I have done all steps and when I back to Application Gateway and created an SSL profile I received this error when I want to upload *.cer files.
Failed to save configuration changes to application gateway 'XXXX'. Error: TrustedClientCertificate XXXX/providers/Microsoft.Network/applicationGateways/XXXX/trustedClientCertificates/XXX'>XXXX/XXX does not contain any CA certificate. A CA certificate contains the basic constraint extension with the subject type as CA.

Answer 1

You can use the below powershell command to create the root and leaf certificates for mutual authentication.
Root:
$cert = New-SelfSignedCertificate -Type Custom -KeySpec Signature -Subject "CN=MutualAuthRoot" -KeyExportPolicy Exportable -HashAlgorithm sha256 -KeyLength 2048 -TextExtension #("2.5.29.19={text}CA=true") -CertStoreLocation "Cert:\CurrentUser\My" -KeyUsageProperty Sign -KeyUsage CertSign
Client:
New-SelfSignedCertificate -Type Custom -DnsName MutualAuthLeaf -KeySpec Signature -Subject "CN=MutualAuthLeaf" -KeyExportPolicy Exportable -HashAlgorithm sha256 -KeyLength 2048 -CertStoreLocation "Cert:\CurrentUser\My" -Signer $cert -TextExtension #("2.5.29.37={text}1.3.6.1.5.5.7.3.2")