Q: Using Powershell to get Azure AD Token (jwt) I am trying to get a jwt token from AAD using Powershell using Username/Password authentication.  
I am writing a powershell script that will to call an API using a bearer token. What I have works if I copy & paste the token from an SPA that uses the API. I am looking for a way to retrieve the token from my powershell. 
This looks really promising: https://github.com/Azure-Samples/active-directory-dotnet-native-headless/blob/master/TodoListClient/Program.cs
I feel like I'm smacking my head against a wall trying to create a 'UserPasswordCredential' object. Any clues to how I can do this would be super-helpful. 
I have Add-Type-ed:
- Microsoft.IdentityModel.Clients.ActiveDirectory.dll
- Microsoft.IdentityModel.Clients.ActiveDirectory.platform.dll (adds nothing?)
- Microsoft.IdentityModel.Clients.ActiveDirectory.WindowsForms.dll
- Microsoft.IdentityModel.Clients.ActiveDirectory.WindowsForms.dll  
The docs page for 'UserPasswordCredential' :
https://learn.microsoft.com/en-us/dotnet/api/microsoft.identitymodel.clients.activedirectory.userpasswordcredential
It should be in one of the first two dlls
This, under 'Constraints & Limitations', makes me think it may not actually be possible from powershell: 
http://www.cloudidentity.com/blog/2014/07/08/using-adal-net-to-authenticate-users-via-usernamepassword/
Looking at the code below, the first acquire token succeeds, the second fails - possibly/probably because $cred is a UserCredential not a UserPasswordCredential.
Is is possible to do this with powershell? 

Finally, on a totally different track, how do I find the values for redirectUri and resourceAppIdURI that my application needs? When I look in the AAD console, and browser to my Enterprise Application, I can find the AppId (which I can use as $clientId).
I'm not sure the redirectUri is strictly necessary for me as all I really want is the token, but I can have a good guess at what it should be. 
When I try to call the first AquireToken method (without $cred) using my app details, it fails with this message:  
Exception calling "AcquireToken" with "4" argument(s): "AADSTS50001: The application named https://myappwithapi/Login was not found in the tenant named me.onmicrosoft.com.

Is it possible for me to find the require value for resourceAppIdURI by looking in my azure portal?
'https://myappwithapi/Login' is from my azure portal > enterprise apps > [app' > properties > HomepageUrl 

code: 
#setup
$TenantName = "mme.onmicrosoft.com"
$clientId = "1950a258-227b-4e31-a9cf-717495945fc2" # Microsoft
$clientId = "03faf8db-..........................." #

$username = "me@me.onmicrosoft.com"
$password = Read-Host -AsSecureString -Prompt "Enter Password"


# add dlls
$adal = "${env:ProgramFiles(x86)}\Microsoft SDKs\Azure\PowerShell\ServiceManagement\Azure\Services\Microsoft.IdentityModel.Clients.ActiveDirectory.dll"
$adalforms = "${env:ProgramFiles(x86)}\Microsoft SDKs\Azure\PowerShell\ServiceManagement\Azure\Services\Microsoft.IdentityModel.Clients.ActiveDirectory.WindowsForms.dll"
$adalplatform = "${env:ProgramFiles(x86)}\Microsoft SDKs\Azure\PowerShell\ServiceManagement\Azure\Services\Microsoft.IdentityModel.Clients.ActiveDirectory.platform.dll"
[System.Reflection.Assembly]::LoadFrom($adal) | Out-Null
[System.Reflection.Assembly]::LoadFrom($adalforms) | Out-Null
[System.Reflection.Assembly]::LoadFrom($adalplatform) | Out-Null



#prep request
$redirectUri = "urn:ietf:wg:oauth:2.0:oob" # Microsoft
$resourceAppIdURI = "https://graph.windows.net"
$authority = "https://login.windows.net/$TenantName"
$authContext = New-Object "Microsoft.IdentityModel.Clients.ActiveDirectory.AuthenticationContext" -ArgumentList $authority


# Get Token prompting for creds
$authResult = $authContext.AcquireToken($resourceAppIdURI, $clientId, $redirectUri, "Always")
$authResult


# Get the cred
$cred = New-Object -TypeName 'Microsoft.IdentityModel.Clients.ActiveDirectory.UserCredential' -ArgumentList $username, $password
#$cred = New-Object -TypeName 'Microsoft.IdentityModel.Clients.ActiveDirectory.UserPassCredential' -ArgumentList $username, $password
$authResult = $authContext.AcquireToken($resourceAppIdURI, $clientId, $cred)

$authResult


A: This post has more the one question in it.
Your base use case 'Using Powershell to get Azure AD Token (jwt)' is a common one and there are several samples and pre-built examples to leverage. For example:
https://github.com/pcgeek86/AzureADToken
A PowerShell module that allows you to get a JSON Web Token (JWT) from Azure Active Directory (AAD).
https://gallery.technet.microsoft.com/Get-Azure-AD-Bearer-Token-37f3be03
This script acquires a bearer token that can be used to authenticate to the Azure Resource Manager API with tools such as Postman. It uses the Active Directory Authentication Library that is installed with the Azure SDK.
See if those two resources resolves your use base line use case.
As for this...
"Is it possible for me to find the require value for resourceAppIdURI by looking in my azure portal?"
You can do this via a remote PowerShell logon to AzureAD. Install the AAD PowerShell module. 
https://learn.microsoft.com/en-us/powershell/azure/overview?view=azurermps-5.1.1
https://msdn.microsoft.com/en-us/library/dn135248(v=nav.70).aspx
Download and install MSOL. Sign in with the MSOL 
https://www.microsoft.com/en-US/download/details.aspx?id=39267
The Microsoft Online Services Sign-In Assistant provides end user sign-in capabilities 
and use the built-in cmdlets to pull your information from your organization settings, and or hit the MSGraph API and query.
https://learn.microsoft.com/en-us/powershell/azure/active-directory/install-adv2?view=azureadps-2.0
You can use the Azure Active Directory PowerShell Module Version for Graph for Azure AD administrative tasks
As for this one:
"how do I find the values for redirectUri and resourceAppIdURI that my application needs?"
This is in your app registration section of your portal. The developer team provide the redir uri not Azure. It's part of the registration process all else is generated by Azure App Reg process.
The app registration process is here and of course you are someone else had to register this app in AzureAD, and thus can retrieve it at any time.:
https://blogs.msdn.microsoft.com/onenotedev/2015/04/30/register-your-application-in-azure-ad 
Any registered apps and their details can be retrieved using...
Get-AzureADApplication
Get-AzureADApplication | Select -Property *
(Get-AzureADApplication).ReplyUrls
Get-AzureADApplication | Select -Property AppID, DisplayName,ReplyUrls

https://learn.microsoft.com/en-us/powershell/module/azuread/get-azureadapplication?view=azureadps-2.0
