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A simple way to get an access token for working with Azure REST API from PowerShell

· 2 min read

This post is sort of a follow up on a previous post where I attempted to prevent a duplicate login when accessing both Azure Resource Manager and Azure AD in the same PowerShell script, still without success by the way. But I can use something I learned there to accomplish something else: getting an access token for working with the Azure REST API.

Getting the access token​

Getting the access token follows the same steps as described in my earlier post:

$rmAccount = Add-AzureRmAccount -SubscriptionId $subscriptionId
$tenantId = (Get-AzureRmSubscription -SubscriptionId $subscriptionId).TenantId
$tokenCache = $rmAccount.Context.TokenCache
$cachedTokens = $tokenCache.ReadItems() `
        | where { $_.TenantId -eq $tenantId } `
        | Sort-Object -Property ExpiresOn -Descending
$accessToken = cachedTokens[0].AccessToken

Of course, you have to login using an account that has sufficient permissions to access the REST API.

Using the token​

We can now use the token to call the REST API. For example, to retrieve all the resource groups in a subscription. The easiest way is via the Invoke-RestMethod PowerShell cmdlet:

$apiVersion = "2017-05-10"
Invoke-RestMethod -Method Get `
                  -Uri ("https://management.azure.com/subscriptions/" + $subscriptionId +
                        "/resourcegroups" +
                        "?api-version=" + $apiVersion) `
                  -Headers @{ "Authorization" = "Bearer " + $accessToken }