Get SharedAccessSignature for API Management (v1 REST API) using PowerShell

get-apim-access.ps1

$Source = @" 
namespace Microsoft.Apim 
{ 
	using System;   
	using System.Net;
	using System.Text;   
	using System.Globalization;   
	using System.Security.Cryptography;
	
	public static class Tools
	{
		public static string GetSharedAccessSignature(string id, string key)
		{
			DateTime then = DateTime.UtcNow.AddMinutes(10);
			// seconds must be zero for this to work
			DateTime expiry = new DateTime(then.Year, then.Month, then.Day, then.Hour, then.Minute, 0, DateTimeKind.Utc);
			using (HMACSHA512 hmac = new HMACSHA512(Encoding.UTF8.GetBytes(key)))
			{
				string dataToSign = id + "\n" + expiry.ToString("O", CultureInfo.InvariantCulture);
				byte[] hash = hmac.ComputeHash(Encoding.UTF8.GetBytes(dataToSign));
				string signature = Convert.ToBase64String(hash);
				
				return string.Format("SharedAccessSignature {0}&{1:yyyyMMddHHmm}&{2}", id, expiry, signature);
			}
		}
	}
}
"@ 

Add-Type -TypeDefinition $Source -Language CSharp

if ($(Get-AzureRmContext) -eq $null) {
	Login-AzureRmAccount
}

$apimContext = New-AzureRmApiManagementContext -ResourceGroupName "<resource group name>" -ServiceName "<service name>"
$access = Get-AzureRmApiManagementTenantAccess -Context $apimContext

$id = $access.Id
$key = $access.PrimaryKey

$token = [Microsoft.Apim.Tools]::GetSharedAccessSignature($id, $key)

$token

$contentType = "application/json"
$headers = @{
  "Authorization" = $token; 
  "Content-Type" = $contentType; # tell APIM we're using a swagger definition
  "If-Match" = "*"; # allows us to overwrite the existing API definition in APIM
}

$uri = "https://$($apimContext.ServiceName).management.azure-api.net/apis?api-version=2017-03-01"

Write-Output "Getting list of apis from '$uri' `n"

[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12 #force TLS 1.2
$response = Invoke-RestMethod -Uri $uri -Headers $headers -ContentType $contentType -Method Get

$response.Value