microsoft-azure-webjobs-extensions-authentication-events-dotnet

description	Microsoft Entra Authentication Events SDK for .NET. Azure Functions triggers for custom authentication extensions. Use for token enrichment, custom claims, attribute collection, and OTP customization in Entra ID. Triggers: "Authentication Events", "WebJobsAuthenticationEventsTrigger", "OnTokenIssuanceStart", "OnAttributeCollectionStart", "custom claims", "token enrichment", "Entra custom extension", "authentication extension".
name	microsoft-azure-webjobs-extensions-authentication-events-dotnet
source_file	SKILL.md
title	Microsoft.Azure.WebJobs.Extensions.AuthenticationEvents (.NET)

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

Event	Purpose
OnTokenIssuanceStart	Add custom claims to tokens during issuance
OnAttributeCollectionStart	Customize attribute collection UI before display
OnAttributeCollectionSubmit	Validate/modify attributes after user submission
OnOtpSend	Custom OTP delivery (SMS, email, etc.)

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

Type	Purpose
WebJobsAuthenticationEventsTriggerAttribute	Function trigger attribute
WebJobsTokenIssuanceStartRequest	Token issuance event request
WebJobsTokenIssuanceStartResponse	Token issuance event response
WebJobsProvideClaimsForToken	Action to add claims
WebJobsAttributeCollectionStartRequest	Attribute collection start request
WebJobsAttributeCollectionStartResponse	Attribute collection start response
WebJobsAttributeCollectionSubmitRequest	Attribute submission request
WebJobsAttributeCollectionSubmitResponse	Attribute submission response
WebJobsSetPrefillValues	Prefill form values
WebJobsShowBlockPage	Block user with message
WebJobsShowValidationError	Show validation errors
WebJobsModifyAttributeValues	Modify submitted values
WebJobsOnOtpSendRequest	OTP send event request
WebJobsOnOtpSendResponse	OTP send event response
WebJobsOnOtpSendSuccess	OTP sent successfully
WebJobsOnOtpSendFailed	OTP send failed
WebJobsContinueWithDefaultBehavior	Continue with default flow

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

SDK	Purpose	Install
Microsoft.Azure.WebJobs.Extensions.AuthenticationEvents	Auth events (this SDK)	dotnet add package Microsoft.Azure.WebJobs.Extensions.AuthenticationEvents
Microsoft.Identity.Web	Web app authentication	dotnet add package Microsoft.Identity.Web
Azure.Identity	Azure authentication	dotnet add package Azure.Identity

Reference Links

Resource	URL
NuGet Package	https://www.nuget.org/packages/Microsoft.Azure.WebJobs.Extensions.AuthenticationEvents
Custom Extensions Overview	https://learn.microsoft.com/entra/identity-platform/custom-extension-overview
Token Issuance Events	https://learn.microsoft.com/entra/identity-platform/custom-extension-tokenissuancestart-setup
Attribute Collection Events	https://learn.microsoft.com/entra/identity-platform/custom-extension-attribute-collection
GitHub Source	https://github.com/Azure/azure-sdk-for-net/tree/main/sdk/entra/Microsoft.Azure.WebJobs.Extensions.AuthenticationEvents