diff --git a/Program.cs b/Program.cs
index a174956..ef0308c 100644
--- a/Program.cs
+++ b/Program.cs
@@ -1,7 +1,19 @@
+using budgetbud.Services;
+
 var builder = WebApplication.CreateBuilder(args);
 builder.Services.AddControllers();
 builder.Services.AddSwaggerGen();
 
+if (builder.Environment.IsDevelopment())
+{
+    builder.Services.AddScoped<IIdentityService, FakeIdentityService>();
+}
+else
+{
+    builder.Services.AddScoped<IIdentityService, AzureIdentityService>();
+}
+
+
 var app = builder.Build();
 
 app.UseDefaultFiles();
diff --git a/api/services/azure_identity_service.cs b/api/services/azure_identity_service.cs
index e69de29..eb346f4 100644
--- a/api/services/azure_identity_service.cs
+++ b/api/services/azure_identity_service.cs
@@ -0,0 +1,47 @@
+using System.Diagnostics;
+using System.Text.Json;
+using budgetbud.Services;
+
+namespace budgetbud.Services;
+
+public class AzureIdentityService : IIdentityService
+{
+    private readonly IHttpContextAccessor _httpContextAccessor;
+
+    public AzureIdentityService(IHttpContextAccessor httpContextAccessor)
+    {
+        _httpContextAccessor = httpContextAccessor;
+    }
+
+    public string GetUserIdentity()
+    {
+        if (_httpContextAccessor.HttpContext != null && _httpContextAccessor.HttpContext!.Request.Headers.TryGetValue("X-MS-CLIENT-PRINCIPAL-ID", out var userId))
+        {
+            string decoded_userId = System.Text.Encoding.UTF8.GetString(Convert.FromBase64String(userId!));
+            dynamic claims = JsonSerializer.Deserialize<dynamic>(decoded_userId) ?? throw new Exception("Claims not valid JSON");
+            string provider = claims.provider_name;
+            switch (provider)
+            {
+                case "github":
+                    return ProcessGithub(claims);
+                default:
+                    throw new Exception("Provider not supported");
+            }
+        }
+
+        throw new Exception("X-MS-CLIENT-PRINCIPAL-ID header not found");
+    }
+
+    private static string ProcessGithub(dynamic json)
+    {
+        string? claims = json.user_claims;
+        foreach (dynamic claim in claims)
+        {
+            if (claim.typ == "http://schemas.xmlsoap.org/ws/2005/05/identity/claims/nameidentifier")
+            {
+                return "github:" + claim.val;
+            }
+        }
+        throw new Exception("Name claim not found");
+    }
+}
\ No newline at end of file
diff --git a/api/services/fake_identity_service.cs b/api/services/fake_identity_service.cs
index e69de29..29f703d 100644
--- a/api/services/fake_identity_service.cs
+++ b/api/services/fake_identity_service.cs
@@ -0,0 +1,21 @@
+namespace budgetbud.Services;
+
+public class FakeIdentityService : IIdentityService
+{
+    private readonly IWebHostEnvironment _environment;
+
+    public FakeIdentityService(IWebHostEnvironment environment)
+    {
+        _environment = environment;
+    }
+
+    public string GetUserIdentity()
+    {
+        if (_environment.IsProduction())
+        {
+            throw new Exception("FakeIdentityService should not be used in production");
+        }
+        return "fake_user:123";
+    }
+
+}
\ No newline at end of file
diff --git a/api/user_data_controller.cs b/api/user_data_controller.cs
index 96d72ad..451878a 100644
--- a/api/user_data_controller.cs
+++ b/api/user_data_controller.cs
@@ -1,3 +1,4 @@
+using budgetbud.Services;
 using Microsoft.AspNetCore.Mvc;
 
 namespace budgetbud.Controllers;
@@ -6,6 +7,13 @@ namespace budgetbud.Controllers;
 [Route("api/[controller]")]
 public class UserDataController : ControllerBase
 {
+    private readonly IIdentityService _identityService;
+
+    public UserDataController(IIdentityService identityService)
+    {
+        _identityService = identityService;
+    }
+
     [HttpGet("hello-world")]
     public IActionResult Get()
     {
@@ -15,15 +23,13 @@ public IActionResult Get()
     [HttpGet("user-id")]
     public IActionResult GetUserId()
     {
-        if (HttpContext.Request.Headers.TryGetValue("X-MS-CLIENT-PRINCIPAL", out var clientPrincipal))
+        try
         {
-            // Use the clientPrincipal value here
-            var decodedClientPrincipal = System.Text.Encoding.UTF8.GetString(Convert.FromBase64String(clientPrincipal));
-            return Ok(decodedClientPrincipal);
+            return Ok(_identityService.GetUserIdentity());
         }
-        else
+        catch (Exception e)
         {
-            return BadRequest("X-MS-CLIENT-PRINCIPAL header not found");
+            return BadRequest(e.Message);
         }
     }
 }
\ No newline at end of file