What Does Your User Agent Say About You?


A user agent is a computer program representing a person, for example, a browser in a Web context.

Besides a browser, a user agent could be a bot scraping webpages, a download manager, or another app accessing the Web. Along with each request they make to the server, browsers include a self-identifying User-Agent HTTP header called a user agent (UA) string. This string often identifies the browser, its version number, and its host operating system.

Spam bots, download managers, and some browsers often send a fake UA string to announce themselves as a different client. This is known as user agent spoofing.

The user agent string can be accessed with JavaScript on the client side using the navigator.userAgent property.

A typical user agent string looks like this: "Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:35.0) Gecko/20100101 Firefox/35.0".


User Agent String

Browser Data

Useragentapplication Logout

Christina Perez
• Friday, 30 July, 2021
• 7 min read

Before you can get tokens to access APIs in your application, you need an authenticated user context. You can also optionally pass the scopes of the APIs for which you need the user to consent at the time of sign-in.



If you don't want users to move away from your main application page during authentication, we recommend the pop-up method. Because the authentication redirect happens in a pop-up window, the state of the main application is preserved.

The redirect methods don't return a promise because of the move away from the main app. To process and access the returned tokens, you need to register success and error callbacks before you call the redirect methods.

The Meal library provides a logout method that clears the cache in browser storage and sends a sign-out request to Azure Active Directory (Azure AD). After sign-out, the library redirects back to the application start page by default.

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Acquires an access token using interactive authentication via a popup Window. acquireTokenRedirect (AuthRequest request) void Acquires an access token by redirecting the user to the authorization endpoint.

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GetPostLogoutRedirectUri () String Returns the post- logout redirect URI currently configured. getRedirectUri () String Returns the redirect URI currently configured.

Initiates the login process by opening a popup browser window. loginRedirect () void Initiates the login process by redirecting the user to the authorization endpoint.

Logout () void Logs out the current user, and redirects to the postLogoutRedirectUri. SsoSilent (AuthRequest request) Future < Autoresponder > Establishes user context silently with SSO when an existing session is known.

Making statements based on opinion; back them up with references or personal experience. The acquireTokenSilent method which lies at the core of this functionality will try to get a cached access token from either session or localStorage depending upon your configurations above if it fails to find one or the access token is close to expiring/has expired, it will request a new one if authentication fails when requesting the new access token due to the session expiring in AAD's back end, it will indicate “interaction required” at which point our code makes an interactive request, essentially requiring the user to re-enter their credentials to keep the session alive.

Using our above authService, lets us show how we can use it in combination with React, Redux, Redux-Sagas, and Axis to build the basis of an application. Axis, being our HTTP request client, is the easiest place to start.

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We create a client at the start, you can see that we have an Azure API product subscription key in our headers as a fun side-note. Import axis from 'axis' import configuration from './configuration.Jason' ; import authService from './authService' ; var apical = configuration.gateway; export coast client = axis.create({base URL: apical, rejectUnauthorized: false, crossbowman: true, headers: {'Ocp-Apim-Subscription-Key' : configuration. Applications} }); coast request = (options) {return authService.fetchAccessToken() .then((accession) {if (!options.headers) options.headers = {}; options.headers = `bearer ${accession}`; return client(options) .then(response {return;}).

Catch (error Promise.reject(error.response || error.message));});} import axis from 'axis' import configuration from './configuration.Jason' ; import authService from './authService' ; var apical = configuration.gateway; export coast client = axis.create({base URL: apical, rejectUnauthorized: false, crossbowman: true, headers: {'Ocp-Apim-Subscription-Key' : configuration. Applications} }); coast request = (options) {return authService.fetchAccessToken() .then((accession) {if (!options.headers) options.headers = {}; options.headers = `bearer ${accession}`; return client(options) .then(response {return;}). If our application is using Redux to manage state, it makes sense to take our abstraction of authService a step further and handle those methods using a reducer and actions.

Tab or window) or code is called to deliberately log the user out. Choosing local Storage will instead create indefinite session life unless code is called to deliberately log the user out.

Logout is rather simple to implement as compared to log in. Let us proceed with the Layout view because we want to build a UI that has some links.

All the information you need to build this UI is available from the Razor view context. We will have to build a logout button inside a form, which will be posted to the web server.


This has to be done as it will create certain unsavory conditions, if you allow a simple GET REQUEST to allow a user out. We will force this to be a post, and when the user submits this form, all we need to do is hit on the Logout action, which we will implement through the AccountController, and logout the user.

If the user is not signed in, and we have an anonymous user, then we need to show a link that will go to the AccountController, specifically to the Login action, and it can display the text Login. We can return a task of IActionResult and the action is named Logout.

The view will be redirected to the home page, and we will go back to the list of employees. To begin with, we will need a new Remodel to pull the login data because logging in is very different from registering.

When the users log in, they have to provide some information like the username, password. To allow this feature we have added a Boolean property RememberMe, and we have used a Display annotation.

Now when we build a label, the text Remember Me gets displayed with a space. The last information that we actually want as part of this Remodel is to have a property that will store the Returner.

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Let us now add the Login action that will respond to the Get request as shown in the following program. In the middle pane, select the MVC View Page and call it Log in.HTML and then Click on the Add button.

We need to use a tag helper, asp-route-returnurl, to make sure that the Returner is there in the URL that the form posts back to. Anything that you add after asp-route-, id or returner, whatever you have there, that will go into the request somewhere, either into the URL path or as a query string parameter.

We have our ValidationSummary and inputs for Username, Password, and Remember Me, and then we have a Submit button. This will be an Asynchronous method because we will need to call into the Identity framework and return a task or IActionResult.

If it is valid, then sign in the user by calling an API on the SignInManager. We also need to add a model error that prompts if there is an Invalid login attempt.

When you click on the Login button, the browser will ask you if you would you like to save your password for the localhost. Making statements based on opinion; back them up with references or personal experience.

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This article describes initializing Microsoft Authentication Library for JavaScript (MSAL.js) with an instance of a user-agent application. The instance and sign-in audience, when concatenated, make up the authority. Directory (tenant) IDOptionalSpecify this if you're building a line-of-business application solely for your organization, often referred to as a single-tenant application. Redirect URIOptionalIf you're building a web app, the redirected specifies where the identity provider (the Microsoft identity platform) should return the security tokens it has issued.

Initialize the Meal authentication context by instantiating a PublicClientApplication with a Configuration object. .then is invoked and tokenResponse is truth: The application is returning from a redirect operation that was successful.

.then is invoked and tokenResponse is false (null): The application is not returning from a redirect operation. Initialize the Meal 1.x authentication context by instantiating a UserAgentApplication with a configuration object.

Explicitly registering the callback is required in MSAL.js 1.2.x and earlier because redirect flows do not return promises like the methods with a pop-up experience do. Multiple instances of UserAgentApplication or PublicClientApplication are not recommended as they cause conflicting cache entries and behavior in the browser.

Instead, start with the index.html which is still very raw, but includes an applicationConfig object, functionaries the login flow, and also has a basic UX. It seems to do a lot of different things like listen for the callback from the popup window that gets created, and captures the returned ID and access token to be ingested by the acquireToken functions.

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This was a really awful experience, which then made me go down the path of switching loginPopup to loginRedirect so that the user would stay on the same page the whole time. Besides showing off MSAL.js in a really simple website, I think this app will be useful when trying to use other tools like Postman where you will need to have a valid access token, and generating one may not be so straight forward to the end user.

While this sample in its current form is pretty cool, it does not satisfy all the goals I listed above. I still need to figure out exactly how to call a custom API using a V2 application (which may not even be possible to configure right now until a new UX which a co-worker of mine is working on becomes available).

I hope this was useful for some of you, and if there are additional things I could add to make this project work better for you, just let me know through a GitHub issue.

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10: Malicious User Agent Definition
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