Reddit Thread Answer: Azure AD – Autologon endpoint

[string]$username= Read-Host -Prompt "Enter UserName"
$securedValue = Read-Host -AsSecureString -Prompt "uurPass"
$bstr = [System.Runtime.InteropServices.Marshal]::SecureStringToBSTR($securedValue)
$password = [System.Runtime.InteropServices.Marshal]::PtrToStringAuto($bstr)
$requestid = [System.Guid]::NewGuid().guid
$domain = ($username -split "@")[1]
Invoke-RestMethod -Method Get -UseBasicParsing ("https://login.microsoftonline.com/common/userrealm/$username" + "?api-version=1.0") -UserAgent $userAgent
$headers = @{
"client-request-id"=$requestid
"return-client-request-id"="true"
}
$uri2 = "https://autologon.microsoftazuread-sso.com/$domain/winauth/trust/2005/usernamemixed?client-request-id=$requestid"
[xml]$data = '<?xml version="1.0" encoding="UTF-8"?>
<s:Envelope xmlns:s="http://www.w3.org/2003/05/soap-envelope" xmlns:a="http://www.w3.org/2005/08/addressing" xmlns:u="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd">
  <s:Header>
    <a:Action s:mustUnderstand="1">http://schemas.xmlsoap.org/ws/2005/02/trust/RST/Issue</a:Action>
    <a:MessageID>urn:uuid:36a6762f-40a9-4279-b4e6-b01c944b5698</a:MessageID>
    <a:ReplyTo>
      <a:Address>http://www.w3.org/2005/08/addressing/anonymous</a:Address>
    </a:ReplyTo>
    <a:To s:mustUnderstand="1">https://autologon.microsoftazuread-sso.com/dewi.onmicrosoft.com/winauth/trust/2005/usernamemixed?client-request-id=30cad7ca-797c-4dba-81f6-8b01f6371013</a:To>
    <o:Security xmlns:o="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd" s:mustUnderstand="1">
      <u:Timestamp u:Id="_0">
        <u:Created>2019-01-02T14:30:02.068Z</u:Created>
        <u:Expires>2019-01-02T14:40:02.068Z</u:Expires>
      </u:Timestamp>
      <o:UsernameToken u:Id="uuid-ec4527b8-bbb0-4cbb-88cf-abe27fe60977">
        <o:Username>DefinedLater</o:Username>
        <o:Password>DefinedLater</o:Password>
      </o:UsernameToken>
    </o:Security>
  </s:Header>
  <s:Body>
    <trust:RequestSecurityToken xmlns:trust="http://schemas.xmlsoap.org/ws/2005/02/trust">
      <wsp:AppliesTo xmlns:wsp="http://schemas.xmlsoap.org/ws/2004/09/policy">
        <a:EndpointReference>
          <a:Address>urn:federation:MicrosoftOnline</a:Address>
        </a:EndpointReference>
      </wsp:AppliesTo>
      <trust:KeyType>http://schemas.xmlsoap.org/ws/2005/05/identity/NoProofKey</trust:KeyType>
      <trust:RequestType>http://schemas.xmlsoap.org/ws/2005/02/trust/Issue</trust:RequestType>
    </trust:RequestSecurityToken>
  </s:Body>
</s:Envelope>
'
[string]$UsernameToken  = [System.Guid]::NewGuid().guid
[string]$messageId = "urn:uuid:" + ([System.Guid]::NewGuid().guid)
 $data.Envelope.Header.Security.UsernameToken.Id =$UsernameToken
 $data.Envelope.Header.Security.UsernameToken.Username = $username
 $data.Envelope.Header.Security.UsernameToken.Password = $password
 $data.Envelope.Header.MessageID = $messageId
 $data.Envelope.Header.To.'#text'= $uri2
$req = Invoke-RestMethod -UseBasicParsing -Uri $uri2 -Method Post -Headers $headers -Body  $data -ContentType "application/soap+xml; charset=utf-8" -UserAgent $userAgent 
$samltoken = $req.Envelope.Body.RequestSecurityTokenResponse.RequestedSecurityToken.Assertion.DesktopSsoToken
$token ='<saml:Assertion xmlns:saml="urn:oasis:names:tc:SAML:1.0:assertion"><DesktopSsoToken>SAMLSSO</DesktopSsoToken></saml:Assertion>' -replace "SAMLSSO", $samltoken
$bytes = [System.Text.Encoding]::ASCII.GetBytes($token)
$base64 = [System.Convert]::ToBase64String($bytes);$base64
$uri3 = "https://login.microsoftonline.com/common/oauth2/token"
$body =@{
    client_id="cb1056e2-e479-49de-ae31-7812af012ed8"
    resource="https://graph.microsoft.com"
    grant_type="urn:ietf:params:oauth:grant-type:saml1_1-bearer"
    assertion=$base64
    }
    
$req = Invoke-RestMethod -UseBasicParsing -Uri $uri3 -Method Post -Headers $headers -ContentType "application/x-www-form-urlencoded" -Body $body
$headers = @{
    "Authorization" = ($req.token_type) +" "+ ($req.access_token)
    }
    
    $me = Invoke-RestMethod -Uri ($body.resource + "/v1.0/me") -Method Get -Headers $headers; $me