Azure Functions: How to access the host key programmatically using C# code?

Question

I'm writing an Azure Function App that needs to provide a HTML page with a form. The form should post back to one of the endpoints of the App. The App shall be protected with Azure's Authorization Key functionality.

Azure allows the caller to provide his/her key in two ways:

1. With a code request query parameter.
2. With a x-functions-clientid HTTP header.

To make the call to the other endpoint of the Azure Function App successful, I will therefore need to provide the Host Key along with my request. For example like this:

    <form method='post' action='DoSomething?code={{{WHERE TO GET THIS FROM?}}}'>
        <input name='someInput' />
        <input type='submit' />
    </form>

I'm using C# to generate the HTML code. What's the most bullet-proof way to get the/a Host Key programmatically?

Answer 1

You could use Microsoft.Azure.Management.ResourceManager.Fluent and Microsoft.Azure.Management.Fluent to do that.

Refer this SO thread for more information.

string clientId = "client id";
 string secret = "secret key";
 string tenant = "tenant id";
 var functionName ="functionName";
 var webFunctionAppName = "functionApp name";
 string resourceGroup = "resource group name";
 var credentials = new AzureCredentials(new ServicePrincipalLoginInformation { ClientId = clientId, ClientSecret = secret}, tenant, AzureEnvironment.AzureGlobalCloud);
 var azure = Azure
          .Configure()
          .Authenticate(credentials)
          .WithDefaultSubscription();

 var webFunctionApp = azure.AppServices.FunctionApps.GetByResourceGroup(resourceGroup, webFunctionAppName);
 var ftpUsername = webFunctionApp.GetPublishingProfile().FtpUsername;
 var username = ftpUsername.Split('\\').ToList()[1];
 var password = webFunctionApp.GetPublishingProfile().FtpPassword;
 var base64Auth = Convert.ToBase64String(Encoding.Default.GetBytes($"{username}:{password}"));
 var apiUrl = new Uri($"https://{webFunctionAppName}.scm.azurewebsites.net/api");
 var siteUrl = new Uri($"https://{webFunctionAppName}.azurewebsites.net");
 string JWT;
 using (var client = new HttpClient())
  {
     client.DefaultRequestHeaders.Add("Authorization", $"Basic {base64Auth}");

     var result = client.GetAsync($"{apiUrl}/functions/admin/token").Result;
     JWT = result.Content.ReadAsStringAsync().Result.Trim('"'); //get  JWT for call funtion key
   }
 using (var client = new HttpClient())
 {
    client.DefaultRequestHeaders.Add("Authorization", "Bearer " + JWT);
    var key = client.GetAsync($"{siteUrl}/admin/functions/{functionName}/keys").Result.Content.ReadAsStringAsync().Result;
  }