Microsoft.Azure.WebJobs.Extensions.AuthenticationEvents (.NET)

Azure Functions extension for handling Microsoft Entra ID custom authentication events.

Installation

dotnet add package Microsoft.Azure.WebJobs.Extensions.AuthenticationEvents

Current Version: v1.1.0 (stable)

Supported Events

OnTokenIssuanceStart

OnAttributeCollectionStart

OnAttributeCollectionSubmit

OnOtpSend

Core Workflows

1. Token Enrichment (Add Custom Claims)

Add custom claims to access or ID tokens during sign-in.

using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.AuthenticationEvents;
using Microsoft.Azure.WebJobs.Extensions.AuthenticationEvents.TokenIssuanceStart;
using Microsoft.Extensions.Logging;

public static class TokenEnrichmentFunction
{
    [FunctionName("OnTokenIssuanceStart")]
    public static WebJobsAuthenticationEventResponse Run(
        [WebJobsAuthenticationEventsTrigger] WebJobsTokenIssuanceStartRequest request,
        ILogger log)
    {
        log.LogInformation("Token issuance event for user: {UserId}", 
            request.Data?.AuthenticationContext?.User?.Id);

        // Create response with custom claims
        var response = new WebJobsTokenIssuanceStartResponse();
        
        // Add claims to the token
        response.Actions.Add(new WebJobsProvideClaimsForToken
        {
            Claims = new Dictionary<string, string>
            {
                { "customClaim1", "customValue1" },
                { "department", "Engineering" },
                { "costCenter", "CC-12345" },
                { "apiVersion", "v2" }
            }
        });

        return response;
    }
}

2. Token Enrichment with External Data

Fetch claims from external systems (databases, APIs).

using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.AuthenticationEvents;
using Microsoft.Azure.WebJobs.Extensions.AuthenticationEvents.TokenIssuanceStart;
using Microsoft.Extensions.Logging;
using System.Net.Http;
using System.Text.Json;

public static class TokenEnrichmentWithExternalData
{
    private static readonly HttpClient _httpClient = new();

    [FunctionName("OnTokenIssuanceStartExternal")]
    public static async Task<WebJobsAuthenticationEventResponse> Run(
        [WebJobsAuthenticationEventsTrigger] WebJobsTokenIssuanceStartRequest request,
        ILogger log)
    {
        string? userId = request.Data?.AuthenticationContext?.User?.Id;
        
        if (string.IsNullOrEmpty(userId))
        {
            log.LogWarning("No user ID in request");
            return new WebJobsTokenIssuanceStartResponse();
        }

        // Fetch user data from external API
        var userProfile = await GetUserProfileAsync(userId);
        
        var response = new WebJobsTokenIssuanceStartResponse();
        response.Actions.Add(new WebJobsProvideClaimsForToken
        {
            Claims = new Dictionary<string, string>
            {
                { "employeeId", userProfile.EmployeeId },
                { "department", userProfile.Department },
                { "roles", string.Join(",", userProfile.Roles) }
            }
        });

        return response;
    }

    private static async Task<UserProfile> GetUserProfileAsync(string userId)
    {
        var response = await _httpClient.GetAsync($"https://api.example.com/users/{userId}");
        response.EnsureSuccessStatusCode();
        var json = await response.Content.ReadAsStringAsync();
        return JsonSerializer.Deserialize<UserProfile>(json)!;
    }
}

public record UserProfile(string EmployeeId, string Department, string[] Roles);

3. Attribute Collection - Customize UI (Start Event)

Customize the attribute collection page before it's displayed.

using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.AuthenticationEvents;
using Microsoft.Azure.WebJobs.Extensions.AuthenticationEvents.Framework;
using Microsoft.Extensions.Logging;

public static class AttributeCollectionStartFunction
{
    [FunctionName("OnAttributeCollectionStart")]
    public static WebJobsAuthenticationEventResponse Run(
        [WebJobsAuthenticationEventsTrigger] WebJobsAttributeCollectionStartRequest request,
        ILogger log)
    {
        log.LogInformation("Attribute collection start for correlation: {CorrelationId}",
            request.Data?.AuthenticationContext?.CorrelationId);

        var response = new WebJobsAttributeCollectionStartResponse();

        // Option 1: Continue with default behavior
        response.Actions.Add(new WebJobsContinueWithDefaultBehavior());

        // Option 2: Prefill attributes
        // response.Actions.Add(new WebJobsSetPrefillValues
        // {
        //     Attributes = new Dictionary<string, string>
        //     {
        //         { "city", "Seattle" },
        //         { "country", "USA" }
        //     }
        // });

        // Option 3: Show blocking page (prevent sign-up)
        // response.Actions.Add(new WebJobsShowBlockPage
        // {
        //     Message = "Sign-up is currently disabled."
        // });

        return response;
    }
}

4. Attribute Collection - Validate Submission (Submit Event)

Validate and modify attributes after user submission.

using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.AuthenticationEvents;
using Microsoft.Azure.WebJobs.Extensions.AuthenticationEvents.Framework;
using Microsoft.Extensions.Logging;

public static class AttributeCollectionSubmitFunction
{
    [FunctionName("OnAttributeCollectionSubmit")]
    public static WebJobsAuthenticationEventResponse Run(
        [WebJobsAuthenticationEventsTrigger] WebJobsAttributeCollectionSubmitRequest request,
        ILogger log)
    {
        var response = new WebJobsAttributeCollectionSubmitResponse();

        // Access submitted attributes
        var attributes = request.Data?.UserSignUpInfo?.Attributes;
        
        string? email = attributes?["email"]?.ToString();
        string? displayName = attributes?["displayName"]?.ToString();

        // Validation example: block certain email domains
        if (email?.EndsWith("@blocked.com") == true)
        {
            response.Actions.Add(new WebJobsShowBlockPage
            {
                Message = "Sign-up from this email domain is not allowed."
            });
            return response;
        }

        // Validation example: show validation error
        if (string.IsNullOrEmpty(displayName) || displayName.Length < 3)
        {
            response.Actions.Add(new WebJobsShowValidationError
            {
                Message = "Display name must be at least 3 characters.",
                AttributeErrors = new Dictionary<string, string>
                {
                    { "displayName", "Name is too short" }
                }
            });
            return response;
        }

        // Modify attributes before saving
        response.Actions.Add(new WebJobsModifyAttributeValues
        {
            Attributes = new Dictionary<string, string>
            {
                { "displayName", displayName.Trim() },
                { "city", attributes?["city"]?.ToString()?.ToUpperInvariant() ?? "" }
            }
        });

        return response;
    }
}

5. Custom OTP Delivery

Send one-time passwords via custom channels (SMS, email, push notification).

using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.AuthenticationEvents;
using Microsoft.Azure.WebJobs.Extensions.AuthenticationEvents.Framework;
using Microsoft.Extensions.Logging;

public static class CustomOtpFunction
{
    [FunctionName("OnOtpSend")]
    public static async Task<WebJobsAuthenticationEventResponse> Run(
        [WebJobsAuthenticationEventsTrigger] WebJobsOnOtpSendRequest request,
        ILogger log)
    {
        var response = new WebJobsOnOtpSendResponse();

        string? phoneNumber = request.Data?.OtpContext?.Identifier;
        string? otp = request.Data?.OtpContext?.OneTimeCode;

        if (string.IsNullOrEmpty(phoneNumber) || string.IsNullOrEmpty(otp))
        {
            log.LogError("Missing phone number or OTP");
            response.Actions.Add(new WebJobsOnOtpSendFailed
            {
                Error = "Missing required data"
            });
            return response;
        }

        try
        {
            // Send OTP via your SMS provider
            await SendSmsAsync(phoneNumber, $"Your verification code is: {otp}");
            
            response.Actions.Add(new WebJobsOnOtpSendSuccess());
            log.LogInformation("OTP sent successfully to {PhoneNumber}", phoneNumber);
        }
        catch (Exception ex)
        {
            log.LogError(ex, "Failed to send OTP");
            response.Actions.Add(new WebJobsOnOtpSendFailed
            {
                Error = "Failed to send verification code"
            });
        }

        return response;
    }

    private static async Task SendSmsAsync(string phoneNumber, string message)
    {
        // Implement your SMS provider integration (Twilio, Azure Communication Services, etc.)
        await Task.CompletedTask;
    }
}

6. Function App Configuration

Configure the Function App for authentication events.

// Program.cs (Isolated worker model)
using Microsoft.Extensions.Hosting;

var host = new HostBuilder()
    .ConfigureFunctionsWorkerDefaults()
    .Build();

host.Run();

// host.json
{
  "version": "2.0",
  "logging": {
    "applicationInsights": {
      "samplingSettings": {
        "isEnabled": true
      }
    }
  },
  "extensions": {
    "http": {
      "routePrefix": ""
    }
  }
}

// local.settings.json
{
  "IsEncrypted": false,
  "Values": {
    "AzureWebJobsStorage": "UseDevelopmentStorage=true",
    "FUNCTIONS_WORKER_RUNTIME": "dotnet"
  }
}

Key Types Reference

WebJobsAuthenticationEventsTriggerAttribute

WebJobsTokenIssuanceStartRequest

WebJobsTokenIssuanceStartResponse

WebJobsProvideClaimsForToken

WebJobsAttributeCollectionStartRequest

WebJobsAttributeCollectionStartResponse

WebJobsAttributeCollectionSubmitRequest

WebJobsAttributeCollectionSubmitResponse

WebJobsSetPrefillValues

WebJobsShowBlockPage

WebJobsShowValidationError

WebJobsModifyAttributeValues

WebJobsOnOtpSendRequest

WebJobsOnOtpSendResponse

WebJobsOnOtpSendSuccess

WebJobsOnOtpSendFailed

WebJobsContinueWithDefaultBehavior

Entra ID Configuration

After deploying your Function App, configure the custom extension in Entra ID:

1. Register the API in Entra ID → App registrations
2. Create Custom Authentication Extension in Entra ID → External Identities → Custom authentication extensions
3. Link to User Flow in Entra ID → External Identities → User flows

Required App Registration Settings

Expose an API:
  - Application ID URI: api://<your-function-app-name>.azurewebsites.net
  - Scope: CustomAuthenticationExtension.Receive.Payload

API Permissions:
  - Microsoft Graph: User.Read (delegated)

Best Practices

1. Validate all inputs — Never trust request data; validate before processing
2. Handle errors gracefully — Return appropriate error responses
3. Log correlation IDs — Use

   CorrelationId

   for troubleshooting
4. Keep functions fast — Authentication events have timeout limits
5. Use managed identity — Access Azure resources securely
6. Cache external data — Avoid slow lookups on every request
7. Test locally — Use Azure Functions Core Tools with sample payloads
8. Monitor with App Insights — Track function execution and errors

Error Handling

[FunctionName("OnTokenIssuanceStart")]
public static WebJobsAuthenticationEventResponse Run(
    [WebJobsAuthenticationEventsTrigger] WebJobsTokenIssuanceStartRequest request,
    ILogger log)
{
    try
    {
        // Your logic here
        var response = new WebJobsTokenIssuanceStartResponse();
        response.Actions.Add(new WebJobsProvideClaimsForToken
        {
            Claims = new Dictionary<string, string> { { "claim", "value" } }
        });
        return response;
    }
    catch (Exception ex)
    {
        log.LogError(ex, "Error processing token issuance event");
        
        // Return empty response - authentication continues without custom claims
        // Do NOT throw - this would fail the authentication
        return new WebJobsTokenIssuanceStartResponse();
    }
}

Related SDKs

Microsoft.Azure.WebJobs.Extensions.AuthenticationEvents

dotnet add package Microsoft.Azure.WebJobs.Extensions.AuthenticationEvents

Microsoft.Identity.Web

dotnet add package Microsoft.Identity.Web

Azure.Identity

dotnet add package Azure.Identity

Reference Links

When to Use

This skill is applicable to execute the workflow or actions described in the overview.