FunctionClientCredentials.cs

#r "Newtonsoft.Json"
#r "System.Configuration"
#r "Microsoft.IdentityModel.Clients.ActiveDirectory.dll"

using System.Net; 
using System.Configuration;
using System.Security.Claims; 
using System.Net.Http.Headers;
using Newtonsoft.Json;
using Microsoft.IdentityModel.Clients.ActiveDirectory;

/// A "reduced" user object containing only a few attributes
public class AADUser
{
    public string displayName { get; set; }
    public string userPrincipalName { get; set; }
    public string mobilePhone { get; set; }
}

public static async Task<HttpResponseMessage> Run(HttpRequestMessage req, TraceWriter log)
{
    log.Verbose($"C# HTTP trigger function processed a request. RequestUri={req.RequestUri}");
    
    // parse query parameter
    string name = req.GetQueryNameValuePairs()
        .FirstOrDefault(q => string.Compare(q.Key, "name", true) == 0)
        .Value;

    // Get request body
    dynamic data = await req.Content.ReadAsAsync<object>();

    // Set name to query string or body data
    name = name ?? data?.name;

    string resourceId = "https://graph.microsoft.com";
    string tenantId = String.Empty;
    string authString = String.Empty;
    string upn = String.Empty;
    string clientId = String.Empty;
    string clientSecret = ConfigurationManager.AppSettings["clientSecret"];

    foreach (Claim claim in ClaimsPrincipal.Current.Claims)
    {
        if (claim.Type == "aud")
        {
            clientId = claim.Value;
            log.Verbose("Claim: " + claim.Type + " Value: " + claim.Value);
        }
        if (claim.Type == "http://schemas.microsoft.com/identity/claims/tenantid")
        {
            tenantId = claim.Value;
            authString = "https://login.microsoftonline.com/" + tenantId;
            log.Verbose("Claim: " + claim.Type + " Value: " + claim.Value);
        }
        if (claim.Type == "http://schemas.xmlsoap.org/ws/2005/05/identity/claims/upn")
        {
            if (claim.Value != name)
            {
                log.Verbose("Claim: " + claim.Type + " Value: " + claim.Value);
                return req.CreateResponse(HttpStatusCode.BadRequest, "Name not matching claims.");
            }
            else
            {
                log.Verbose("Claim: " + claim.Type + " Value: " + claim.Value);
                upn = claim.Value;
            }
        }
        //Uncomment to print all claims to log output for debugging
        //log.Verbose("Claim: " + claim.Type + " Value: " + claim.Value);
    }
    
    var authenticationContext = new AuthenticationContext(authString, false);
    
    // Config for OAuth client credentials 
    ClientCredential clientCred = new ClientCredential(clientId, clientSecret);
    AuthenticationResult authenticationResult = await authenticationContext.AcquireTokenAsync(resourceId,clientCred);
    string token = authenticationResult.AccessToken;
    log.Verbose(token);

    var outputName = String.Empty;
    var responseString = String.Empty;
    var phone = String.Empty;
    
    using (var client = new HttpClient())
    {        
        string requestUrl = $"https://graph.microsoft.com/v1.0/users/{upn}";
        
        HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Get, requestUrl);
        request.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
        log.Verbose(request.ToString());
        
        HttpResponseMessage response = client.SendAsync(request).Result;
        responseString = response.Content.ReadAsStringAsync().Result;  
        var user = JsonConvert.DeserializeObject<AADUser>(responseString);
        phone = user.mobilePhone;
        outputName = user.displayName;
        
        log.Verbose(responseString);
    } 

    return name == null
        ? req.CreateResponse(HttpStatusCode.BadRequest, "Please pass a name on the query string or in the request body")
        : req.CreateResponse(HttpStatusCode.OK, "Hello " + outputName + ", your phone number is: " + phone);
}