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MSAL.NET 3 released

Carlo Mendoza edited this page Mar 11, 2019 · 47 revisions

MSAL.NET 3.0.0 released


We are excited to announce the release of MSAL.NET 3.0-preview, which has a number of changes that we hope, you'll love. In this article, you'll learn about:

Contrary to the previous versions for which the NuGet package had lost its -preview, the NuGet package for this version is 3.0.0-preview as we'd want to have your feedback about our changes, the new API, and the Plans for deprecation in MSAL.NET 3.x and MSAL.NET 4.x

We'd appreciate if you took the time to provide feedback, for instance answering questions or adding any comments in the following GitHub issue [Feedback Request] What do you think of MSAL 3.0.0-preview? #933

Changes in MSAL.NET 3.x

The following paragraph explains the exhaustive reference list of changes in MSAL.NET in more detail.

Reference - list of changes in MSAL.NET 3

Breaking changes in MSAL.NET 3:

  • UIBehavior was renamed to Prompt (breaking change)
  • TokenCacheNotificationArgs now surfaces an ITokenCache instead of a TokenCache. This will allow MSAL.NET to provide, in the future, various token cache implementations.
  • TokenCacheExtensions was removed and its methods moved to ITokenCache (this is a binary breaking change, but not a source level breaking change)
  • The Serialize and Deserialize methods on TokenCacheExtention (which were serializing/deserializing the cache to the MSAL v2 format) were moved to ITokenCache and renamed SerializeMsaV2 and `DeserializeV2

Changes related to improving app creation and configuration

  • New class ApplicationOptions helps you build an application, for instance, from a configuration file.
  • New interface IMsalHttpClientFactory to pass-in the HttpClient to be used by MSAL.NET to communicate with the endpoints of Microsoft identity platform for developers.
  • New classes PublicClientApplicationBuilder and ConfidentialClientApplicationBuilder propose a fluent API to instantiate respectively classes implementing IPublicClientApplication and IConfidentialClientApplication including from configuration files, setting the targetted cloud and audience, but also setting per application logging and telemetry, and setting the HttpClient.
  • New delegates TelemetryCallback and TokenCacheCallback can be set at application construction
  • New enumerations AadAuthorityAudience and AzureCloudInstance help you write applications for sovereign and national clouds, and choose the audience for your application.

Changes related to improving token acquisition:

  • ClientApplicationBase now implements IClientApplicationBase and has new members:
    • AppConfig of new type IAppConfig contains the configuration of the application
    • UserTokenCache of new type ITokenCache contains the user token cache (for both public and confidential client applications for all flows, but AcquireTokenForClient)
      • New fluent API AcquireTokenSilent
  • PublicClientApplication and IPublicClientApplication have four new fluent APIs: AcquireTokenByIntegratedWindowsAuth, AcquireTokenByUsernamePassword, AcquireTokenInteractive, AcquireTokenWithDeviceCode.
  • ConfidentialClientApplication has new members:
    • AppTokenCache used by AcquireTokenForClient
    • Five new fluent APIs: AcquireTokenByAuthorizationCode, AcquireTokenForClient, AcquireTokenOnBehalfOf, GetAuthorizationRequestUrl, IByRefreshToken.AcquireTokenByRefreshToken
  • New extensibility mechanism to enable public client applications to securly provide their own browsing experience to let the user interact with the Microsoft identity platform endpoint (advanced). For this, applications need to implement the ICustomWebUi interface and throw MsalCustomWebUiFailedException exceptions in case of failure. This can be useful in the case of platforms which don't yet have a Web browser. For instance, the Visual Studio Feedback tool is an Electron application which uses this mechanism.
  • MsalServiceException now surfaces two new properties:
    • CorrelationId which can be useful when you interact with Microsoft support.
    • SubError which indicates more details about why the error happened, including hints on how to communicate with the end user.

Changes related to the token cache:

  • New interface ITokenCache contains primitives to serialize and deserialize the token cache and set the delegates to react to cache changes
  • New methods SerializeMsalV3 and DeserializeMsalV3 on ITokenCache serialize/deserialize the token cache to a new layout format compatible with other MSAL libraries on Windows/Linux/MacOS.

Configuring an app got simpler

With MSAL.NET 3.x, we made it much simpler to configure your application. You don't need to choose an override for a constructor. The recommended way is to use the static PublicClientApplicationBuilder and ConfidentiaClientApplicationBuilder classes and call the Create() or CreateFromOption() method. They both return a builder, to which you chain optional properties. When you have all your properties, you call Build() and that's it!

Simple scenarios are simple

If you want to create a desktop application, you can do it with minimal information.

IPublicClientApplication app;
app = PublicClientApplicationBuilder.Create(clientId)

By default, this application will target Work and School Accounts and Microsoft personal accounts from the Microsoft Azure public cloud.

Now, let's assume that your application is a line of business application which is only for your organization, then you can write:

IPublicClientApplication app;
app = PublicClientApplicationBuilder.Create(clientId)
        .WithAuthority(AzureCloudInstance.AzurePublic, tenantId)

More complex scenarios remain simple

Where it becomes interesting is that programming for national clouds has now become simple: if you want your application to be a multi-tenant application in a national or sovereign cloud, you write could for instance:

IPublicClientApplication app;
app = PublicClientApplicationBuilder.Create(clientId)
        .WithAuthority(AzureCloudInstance.AzureUsGovernment, AadAuthorityAudience.AzureAdMultipleOrgs)

Finally, if you are an Azure AD B2C developer, you can specify your tenant like this. Note that you don't need to say that you want to bypass authority validation, which, we heard, was scary.

IPublicClientApplication app;
app = PublicClientApplicationBuilder.Create(clientId)

Of course there are several overloads of .WithAuthority with many different cases. For more information see Client applications

You can now configure your application more easily through config files

Now, chances are that you probably have the application configuration in a file, rather than in the code. This is also possible as the application builder can create an application from Options. Here is how:

PublicClientApplicationOptions = GetOptions(); // your own method.
var app = PublicClientApplicationBuilder.CreateWithApplicationOptions(options)

You'll find a more complete code sample in Client applications

Acquiring a token also got simpler

Once you have your application, you want to acquire tokens. The same kind of pattern is used where you call:

app.AcquireTokenXXX(scopes, mandatory-parameters)

This means you no longer have numerous overrides as you can now choose the parameters you want to set. Finally ExecuteAsync() had an override taking a CancellationToken argument, making all the AcquireTokenXXX methods cancellable, as requested!

app.AcquireTokenXXX(scopes, mandatory-parameters)

For details, see Acquiring tokens and Scenarios and the links from these articles on the detailed token acquisition methods

You can provide your own web view

Implement ICustomWebUI

As explained in You told us you needed extensibility, below, we have added extensibility that allows you provide your own UI in public client applications, and to let the user go through the /Authorize endpoint of the identity provider and let them sign-in and consent. MSAL.NET will then be able to redeem the authentication code and get a token.

If you need to provide your own Web UI:

  1. Implement the ICustomWebUi interface (See here. You'll basically need to implement one method AcquireAuthorizationCodeAsync accepting the authorization code URL (computed by MSAL.NET), letting the user go through the interaction with the identity provider, and then returning back the URL by which the identity provider would have called your implemetnation back (including the authorization code). In case of issues, your implementation should throw a MsalExtensionException exception in order to nicely cooperate with MSAL.
  2. In your AcquireTokenInteractiveCall, you can use the .WithCustomUI() modifier passing the instance of your custom web UI

MSAL.NET UI tests also use this mechanism

We have rewritten our UI tests to leverage this extensibility mechanism. In case you are interested you can have a look at the SeleniumWebUI class in the MSAL.NET source code

Security is respected

Note that, in public client applications, MSAL.NET leverages the PKCE standard (RFC 7636 - Proof Key for Code Exchange by OAuth Public Clients) to ensure that security is respected: Only MSAL.NET can redeem the code.

Breaking changes in MSAL.NET 3.x

As mentionned in Why did MSAL move from 2.x to 3.x?, as we were cleaning up the public API, and simplifying it, we introduced a small number of breaking changes which we expect should not affect you too much for most of the scenarios if you use the MSAL 2.x type API.

  • We renamed a type (UIBehavior)
  • Setting some properties of IClientApplicationBase and ClientApplicationBase after building the application did not make sense any longer, and was getting in the way of testability
  • the application builder now creates the token cache for you, we recommand you to use this mechanism, not instantiate TokenCache yourself.

UIBehavior renamed to Prompt

The UIBehavior class was used until MSAL.NET 2.x to specify, in AcquireTokenAsync (interactive) which prompt the application developer wanted to expose to the user. The class was renamed to Prompt, as explained in Naming-could-be-improved

Logger and Telemetry are now set per application, and during its construction

Until MSAL.NET 3.0, you used to set the logger by setting properties on a static class named Logger. These properties were, therefore, the same for all the applications in your executable

If you have a method to log information

void MyLoggingMethod(LogLevel level, string message, bool containsPii)
 Console.WriteLine($"MSAL {level} {containsPii} {message}");

you used to write:

Logger.LogCallback = MyLoggingMethod;
Logger.Level = LogLevel.Verbose;
Logger.PiiLoggingEnabled = true;

This is no longer possible. You'll need to use the new fluent API if you want to provide logging:

IPublicClientApplication app;
app = PublicClientApplicationBuilder.Create(config.ClientId)
        .WithLogging(MyLoggingMethod, LogLevel.Verbose,
                     enablePiiLogging: true,
                     enableDefaultPlatformLogging: true)

For more details see Logging in MSAL.NET

Some properties on Applications now need to be set by builders, and read through the configuration

Some properties in the V2.0 API style were settable after the application construction. The V3 builder style makes the application properties immutable. From MSAL.NET 3.x, if you need to use these properties, you now need to:

  • Set them when you are building the application (that is with .WithParameter clauses on the application builder)
  • Read them from the application's configuration

Here is the detail. They all are held by:

Property Description Which method of the application builder to user How to read it?
Component Identifier of the component (libraries/SDK) consuming MSAL.NET (telemetry) .WithComponent(component) app.AppConfig.Component
SliceParameters Used for dogfood testing or debugging as a string of segments of the form key=value separated by an ampersand character .WithExtraQueryParameters
ValidateAuthority No longer needed .WithAADAuthority does not require it, .WithB2CAuthority either, .WithAuthority still has a Boolean for specific cases
RedirectUri URI at which the identity provider will contact back the application with the tokens Set to defaults, or, for client applications, in the constructor with .WithRedirectUri app.AppConfig.RedirectUri

How to maintain SSO with apps written with ADAL v3, ADAL v4, MSAL.NET v2

Breaking change in the MSAL.NET cache serialization format and API

MSAL 2.x was providing two serialization mechanisms:

  • One to serialize/deserialize the cache to the unified cache format (V2). This was done through the Serialize and Deserialize extension methods on TokenCacheExtension.
  • The other to serialize/deserialize the cache with both the MSAL V2 formats and the ADAL V3 format at once, therefore, in the case of deserializing, merging the information from several serialization files if both were available (DeserializeUnifiedAndAdalCache and SerializeUnifiedAndAdalCache)

We've taken a breaking change in order to let you:

  • benefit out of the box from a “True” Unified Cache serialized json format across libraries on Windows, Linux and MacOS
  • upgrade your apps easily from ADAL v3 and ADAL v4 to MSAL v3 with-out loosing SSO (if you need it)
  • easily upgrade your apps from MSAL v2 to MSAL v3 with-out loosing SSO (if you need it)

In MSAL.NET 3.x:, the ITokenCache interface is the following:

public interface ITokenCache
 void DeserializeMsalV2(byte[] msalV2State);               // MSAL V2.0 format (was Deserialize() in MSAL 2.x)
 void DeserializeUnifiedAndAdalCache(CacheData cacheData); // Deprecated: ADAL V3.0 and MSAL V3.0 format
 void DeserializeMsalV3(byte[] bytes);                     // New: MSAL V3.0 unified cache format
 void DeserializeAdalV3(byte[] bytes);                     // New ADAL V3.0 format only with merge

 byte[] SerializeMsalV2();                                 // MSAL V2.0 format (was Serialize() in MSAL 2.x)
 CacheData SerializeUnifiedAndAdalCache();                 // Deprecated: ADAL V3.0 and MSAL V3.0 format
 byte[] SerializeMsalV3();                                 // New: MSAL V3.0 unified cache format
 byte[] SerializeAdalV3();                                 // New: for ADAL v3.0 cache format

 void SetAfterAccess(TokenCacheCallback afterAccess);
 void SetBeforeAccess(TokenCacheCallback beforeAccess);
 void SetBeforeWrite(TokenCacheCallback beforeWrite);
  • CacheData and its methods are obsolete with an link to the explanations (this document)
  • Instead of TokenCacheExtensions.SerializeUnifiedAndAdalCache we recommend using, SerializeAdalV3 and SerializeMsalV3 with an link.
  • Instead of TokenCacheExtensions.DeserializeUnifiedAndAdalCache we recommend using, DeserializeAdalV3 and DeserializeMsalV3 with override=false, and an link.
  • Instead of TokenCacheExtensions.Serialize we recommend using SerializeMsalV3 with an link.
  • Instead of TokenCacheExtensions.Deserialize we recommend using and DeserializeMsalV3 with an link.

Support plans for serialization formats

In future versions of MSAL (and ADAL), we'd want to start obsoleting some of the cache serialization format. Here is, for the moment, our proposed support matrix:

Library/version Adal 3.x Format MSAL 2.x Format Msal 3.x format
ADAL.NET 3.0 Supported - -
ADAL.NET 4.0 Supported Supported -
ADAL.NET 5.0 Supported Deprecate (Error) Supported
ADAL.NET 6.0 Supported** Removed Supported
MSAL.NET 2.0* Supported Supported -
MSAL.NET 3.0 Supported Deprecate (Error) Supported
MSAL.NET 4.0 * Removed Supported
MSAL.NET 3.0 + 12m* Deprecate (Error) * Supported
MSAL.NET 3.0 + 24m* Removed * Supported

Supported: means available and Supported

*: We plan on removing v3 support after sometime to make sure our codebase stays as simple as possible. As we ship MSAL 3.0 we mark MSAL v2 and as not supported (same with MSAL v1). We would monitor adoption to understand when the right moment is, to remove support for the v3 cache. Again your feedback would be valuable.

** : Leaving for now but we could consider removing that to ensure that even if you are sticking to ADAL, you'd be using the new format.

Example of code showing how to migrate from MSAL.NET v2 to MSAL.NET v3

There are two scenarios depending on the type of app: one time migration and side by side migration:

  • One time migration. This is the recommended approach for MSAL public client applications which don’t share the cache with other apps or generations of apps, and for confidential client applications that don’t use a distributed cache shared between several web instances: it’s simple (try read V3, if it fails read V2, in any case write V3). This approach is possible as of today with MSAL 3.0.0-preview

    /// <summary>
    /// Enables persistence of the token cache to some storage
    /// </summary>
    /// <param name="unifiedCacheStorageKey">Key (for instance file name in the cache of a
    //  file storage) where the cache is serialized with the Unified cache format
    /// </param>
    public static void EnableFilePersistence(ITokenCache userTokenCache,
                                                   string unifiedCacheStorageKey)
     UnifiedCacheStorageKey = unifiedCacheFileName;
    /// <summary>
    /// File path where the token cache is serialiazed with the unified cache format
    /// </summary>
    public static string UnifiedCacheStorageKey { get; private set; }
    public static void BeforeAccessNotification(TokenCacheNotificationArgs args)
     byte[] serializedData = ReadFromStorageIfExists(UnifiedCacheStorageKey);
     catch (MsalUnexpectedCacheFormatException)
    public static void AfterAccessNotification(TokenCacheNotificationArgs args)
     // if the access operation resulted in a cache update
     if (args.HasStateChanged)
      byte[] serializedCache = args.TokenCache.SerializeMsalV3();
      WriteToStorageIfNotNull(UnifiedCacheStorageKey, serializedCache);
  • For MSAL public client apps that share the cache with other apps or web apps/apis that share the cache between several instances, you'll need to implement a dual MSAL V2 / MSAL V3 for a while until all apps or web instances have migrated. Then remove the support for the MSAL V2 cache format. For this we provide an API enabling you to deserialize with merge.

Note: For the moment (MSAL.NET 3.0.0), if you try to use the Deserialize APIs with merge=true, MSAL will throw a NotImplementedException with a meaningful message; b

/// <summary>
/// Enables persistence of the token cache to some storage
/// </summary>
/// <param name="msalV2CacheStorageKey">Key (for instance file name in the cache of a
//  file storage) where the cache is serialized with the Unified cache format of
/// MSAL 2.x
/// <param name="msalV3CacheStorageKey">Key (for instance file name in the cache of a
//  file storage) where the cache is serialized with the Unified cache format of
/// MSAL 3.x
/// </param>
public static void EnableFilePersistence(ITokenCache userTokenCache,
                                         string msalV2CacheStorageKey,
                                         string msalV3CacheStorageKey)
 MsalV2CacheStorageKey = msalV2CacheStorageKey;
 MsalV3CacheStorageKey = msalV3CacheStorageKey;

/// <summary>
/// File path where the token cache is serialiazed with the unified cache format
/// </summary>
public static string UnifiedCacheStorageKey { get; private set; }

public static void BeforeAccessNotification(TokenCacheNotificationArgs args)

 byte[] serializedData = ReadFromStorageIfExists(MsalV2CacheStorageKey);
 args.TokenCache.DeserializeMsalV2(serializedData, merge:true);
 serializedData = ReadFromStorageIfExists(MsalV3CacheStorageKey);
 args.TokenCache.DeserializeMsalV3(serializedData, merge:true);

public static void AfterAccessNotification(TokenCacheNotificationArgs args)
 // if the access operation resulted in a cache update
 if (args.HasStateChanged)
  byte[] serializedCache = args.TokenCache.SerializeMsalV3();
  WriteToStorageIfNotNull(MsalV3CacheStorageKey, serializedCache);
  serializedCache = args.TokenCache.SerializeMsalV2();
  WriteToStorageIfNotNull(MsalV2CacheStorageKey, serializedCache);

Example code demonstrating how it will be possible (in MSAL 3.1+) to share SSO across all versions

Here are our plans to help you with updating the SSO state in all the possible ways leveraging

// Assigning a token cache to the public client (it's similar for Confidential client, though there a cache for the Application is also avaialble):
IPublicClientApplication app = PublicClientApplicationBuilder.Create(ClientId)

// Setting up the cache allowing loading and persisting the data
TokenCache usertokenCache = app.UserTokenCache

// Event handlers
private void BeforeAccessNotification(TokenCacheNotificationArgs args)
 // Load cache state from file
 byte[] adalV3State = FileStorage.ReadFromFileIfExists(AdalV3FileName);
 byte[] msalv2State = FileStorage.ReadFromFileIfExists(MsalV2FileNAme);
 byte[] msalv3State = FileStorage.ReadFromFileIfExists(MsalV3FileName);

 // To be deprecated

 // Each deserialize call will merge from what has already been loaded
 // Add the cache deserializers ou need
 // Writes to cache used in ClientApplication

private void AfterAccessNotification(TokenCacheNotificationArgs args)
    if (!args.HasStateChanged)

    // Deprecate
    CacheData cacheData = args.TokenCache.SerializeUnifiedAndAdalCache();
    var prevAdalV3State = cacheData.AdalV3State;
    var prevMsalV2State = cacheData.UnifiedState;

    // Add the following cache serializers
    // Reads from the cache in the ClientApplication
    byte[] adalV3State = args.TokenCache.SerializeAdalV3();
    byte[] msalv2State = args.TokenCache.SerializeMsalV2();
    byte[] msalv3State = args.TokenCache.SerializeMsalV3();

    // Persist cache state to file (depending on the migration scenario)
    FileStorage.WriteToFileIfNotNull(AdalV3FileName, adalV3State);
    FileStorage.WriteToFileIfNotNull(MsalV2FileNAme, msalv2State);
    FileStorage.WriteToFileIfNotNull(MsalV3FileName, msalv3State);

Plans for deprecation in MSAL.NET 3.x and MSAL.NET 4.x

As seen above, we are proposing a new MSAL.NET V3.0 API based on builders. For the moment (MSAL 3.0), uses this new API side by side with the previous V2.0 APIs (still having AcquireTokenXXXAsync, and many overrides of these), in order to leave you time to migrate to the new API.

Here is the current proposal, on which we'd like to get your feedback:

  • In 3 months, supposing that, like us, you love the new APIs, we'd want to deprecate the old V2.0 API. At that point, if you still use the old-style API, you'll see warnings encouraging you to move to the new API.
  • Then in the next major version of MSAL.NET, the old V2.0 style APIs would disappear, leaving a very simple shape for the API. In the class diagram below, we've hidden the V2.0 style APIs; that gives you an idea of what the public API could be in the next major release.


Why MSAL.NET moved from MSAL 2.x to MSAL 3.x

This paragraph explains why MSAL.NET's major version number was bumped-up from 2 to 3.

Reacting to your feedback

In August, we released MSAL.NET 2.0 and you've been using it and providing feedback eversince. Since then we've released fourteen incremental updates of MSAL.NET, improving both the API and the behavior of the library. You've been awesome helping us make MSAL.NET a great authentication library. But you also told us that things could be improved upon, and that you needed more flexibility. If you are interested in the analysis of your feedback with links to issues you raised, see the following GitHub issue [New API] Improved 3.x API leveraging builders #810). We wanted to bring you these improvements, but we reached a limit in terms of API complexity. Here are the details of this journey.

You told us you needed more configuration for applications

Providing your own HttpClient, supporting Http proxy and customization of user agent headers

We understand that there are cases where you want fine grained control on the Http proxy for instance, which we had not been able to provide you at all (on .NET core), or in a limited way (.NET framework). Also, ASP.NET Core has some very efficient ways of pooling the HttpClient instance, and MSAL.NET clearly did not benefit from it (for details see Use HttpClientFactory to implement resilient HTTP requests)

IMsalHttpClientFactory httpClientFactory = new MyHttpClientFactory();

var pca = PublicClientApplicationBuilder.Create(MsalTestConstants.ClientId) 
Configuring your app to target national and sovereign clouds was not straightforward

As some of you start working on writing apps that can not only target users in the Azure public cloud, but also in national and sovereign clouds (for instance the US government cloud), you gave us the feedback that you'd need help making this transition easier. There are several ongoing initiatives for this, but MSAL.NET could already make it easier for you to configure the cloud instance you want to target, and the audience of your application. Along the same lines, we also came to the realization that we could help you with the configuration of the application from configuration files, and provide guidance on how to do that better.

var pca = PublicClientApplicationBuilder.Create(MsalTestConstants.ClientId)
Partial summary: Better configuration for apps

It was clear that you needed more configuration options for instantiating applications … therefore more parameters to the constructors, and help to support configuration files.

More flexibility in methods acquiring tokens

MSAL.NET enables you to get access tokens to call protected APIs in different ways, depending on your scenario, on the kind of app you build, and on the platform. See Scenarios.

All MSAL methods are async, so they should accept a CancellationToken.

Similarly, the only way to react to conditional access exceptions in MSAL 2.x was, as explained in Handling Claim challenge exceptions in MSAL.NET, to use the extraQueryParameter. Unfortunately, this parameter was available only in two overrides of the AcquireTokenAsync (interactive) flow, and it was not working correctly. We needed to fix it, and provide a proper claims parameter to AcquireTokenXXXAsync methods, including AcquireTokenSilentAsync.

Finally, some advanced end-user scenarios, like letting the user pre-consent ahead of time were really hard to achieve, as you'll see in the next paragraph.

A limit was reached in terms of method overloads

Let's take one of the scenarios where the developer experience was not good: acquiring a token interactively in a desktop or mobile application (The same reasoning can be extended to other scenarios). In that case you had to call AcquireTokenAsync, but the issue is that this method had 14 overloads (for details of all the parameters see Acquiring tokens interactively).


But what's worse is that to achieve one goal (for instance, letting the end user pre-consent to specific scopes ahead of time), you had to use one specific overload with 7 parameters, and, just to pass extraScopesToConsent, you had to fill-in all the other parameters, and as a result, you had to study the documentation in detail to understand what could be good values for these parameters. This pain is illustrated in this article How to get consent for several resources, where you see that you had to write code like this just to be able to pass-in scopesForVendorApi (and some of you had no idea what to use for uiBehavior, or authority)

var result = await app.AcquireTokenAsync(scopesForCustomerApi,

With each new addition, there would be an explosion in the number of AcquireTokenAsync methods and method params, making the API unusable.

The standard practice to deal with this is to use builder objects, which is introduced in MSAL 3.

var result = await app.AcquireTokenInteractive(scopesForCustomerApi)

More extensibility

Another request you made was to allow developers to bring their own UI - allow public applications to acquire token via authorization code #863. In .NET Core we don't provide interactive authentication because no Web control is available there (yet). But there are cases, like what the Azure CLI team has done, where you want to let the user sign-in and consent into the machine browser on the desktop. This can be done, but at the same time you don't want to sacrifice the security. Therefore you asked us to provide an extensible way to let you do that. Another example of this is our own Visual Studio team who has Electron applications (VS Feedback and Azure Storage explorer) and wanted sign-in to be delegated in their UI, while still benefiting from the rest of MSAL.NET.

  // Here we inject a custom web UI that is controlled by Selenium to test authentication. 
  // See 
  AuthenticationResult result = await pca
                .AcquireTokenInteractive(_scopes, null)
                .WithCustomWebUi(CreateSeleniumCustomWebUI(labResponse.User, false))

Naming could be improved

Finally we heard that we could improve the naming of things a bit. Here is an example UIBehavior was the mechanism, in MSAL 2.x by which you could customize the user experience and direct the Microsoft identity platform to present a particular prompt experience. We got the feedback that the name UIBehavior did not speak much, and everybody in the industry is naming it Prompt therefore we've decided to rename UIBehavior to Prompt in all MSAL libraries, starting with MSAL 3.x

Testability of your app could be improved

In the past to help you test your app (for instance in MSAL 2.5.0-preview), it was still not easy to test the cache, and the applications due to a lack of interfaces (for instance ITokenCache), and the mutability of application configuration (for example it was possible to set the RedirectUri of an app after constructing it)

Unified cache layout format change

MSAL 2.0 already enabled common token cache scenarios between ADAL and MSAL on the platforms supported by ADAL, and also between MSAL libraries on different platforms. However as we were recently working on initiatives to enable SSO between tools written in different languages, we discovered that, on Windows/Linux/MacOS, MSAL.NET and MSAL.Python (for instance), although using the same cache schema, did not share the same layout for the blob that is serialized when you implement your own custom cache serialization. Therefore, we slightly changed the layout format of the token cache blob to harmonize the format between MSAL.NET, MSAL Python and MSAL.Java. This is a breaking change, but we also provided a migration path. See how to maintain SSO with apps written with ADAL v3, ADAL v4, MSAL.NET v2 if you are interested in one of these.

Summarizing the feedback

To summarize what we learned, you needed:

  • More flexibility in configuring your apps,
  • More options to acquire tokens
  • An API which enables your apps to be more testable
  • Customization of the Web view should be possible (on .NET Core)

We had to change the API to enable this flexibility without making it overly complex. Therefore we've decided that MSAL.NET 3 would bring a lot of changes, including a few breaking changes.

Future plans

  • AcquireTokenInteractive for .NET Core 3+ on Windows
  • Leveraging the desktop default browser on MacOS and Linux
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