I have a .Net 5 Web API hosted on Azure App Service.
The API has three Background services running as hosted services, which perform long running processes such as bulk emailing and SMSing, as well as other functionality that runs once a day on a timer.
I am thinking about moving out these hosted/background services into separate Azure Functions, which I would then call / trigger from my API via an HTTP request (except for the one that runs on a timer)
My concern is regarding authentication. How does that work with Azure Functions? Currently, my Web API is using Auth0 as the authentication server. So, when the user uses the front-end web app (Angular), he logs in (via Auth0's login form) and then the front-end retrieves an access/bearer token from AUth0, which it then includes in every call to the API (in an Authentication header).
Now, obviously I don't want just anyone to be able to call the Azure Functions - only my Web API should be able to do so. But how does that work? Does the API need to forward the access token it received from the front end to the Azure Function when calling it? Or is there something I need to set up in Azure Portal to tell it that my API must be allowed access to the Azure Function (and block any requests from any other origin)?
I've never used Azure Functions or even WebJobs before, so I'm a bit lost.
Thanks
When creating an HTTP-triggered Azure Function, by default it is set to have authorization level = Function, which means that any app trying to invoke that function via its URL needs to know the specific access key that is generated for that function upon creation.
In your example, your web API would store that function's invocation URL and access key in its configuration, and invoke your function with that key. Since the key remains entirely server-side on Azure, nothing else can access it, so it's completely secure.
Depending on your requirements, you can then also layer other types of authorization/authentication (e.g. bearer token) on top of the access key mechanism, or use those instead of access keys (by setting the function to allow anonymous access).
For maximum security, I would recommend using both the function access key as a first step to ensure that nobody except your apps can successfully invoke the function, and then passing along and authenticating the bearer token to ensure that the app trying to invoke that function is indeed permitted to do so.
Just be aware that Azure Functions is a slightly different beast to standard ASP.NET Core, particularly in regards to middleware which it doesn't really support yet, so you'll likely need to roll your own code for reading the bearer token from the incoming HTTP request's headers, and verifying that it's valid.
Reference: https://learn.microsoft.com/en-us/azure/azure-functions/functions-bindings-http-webhook-trigger?tabs=csharp#authorization-keys
For this requirement, you just need to enable "Authentication/Authorization" of your function app.
Follow the steps in the screenshot above and when you click the forth red box, choose "Express" tab and click "ok" at the bottom of the page without do anything. It will create an application in your Azure AD which has same name with your function app.
After that, when you request the function app url in browser, it will ask you to login.
For more details of the steps, you can refer to this document.
Hury's guidance is best - you want to avoid using API keys on your production functions and use this just for testing. Official guidance is here:
https://learn.microsoft.com/en-us/azure/azure-functions/functions-bindings-http-webhook-trigger?tabs=in-process%2Cfunctionsv2&pivots=programming-language-csharp#secure-an-http-endpoint-in-production
Configure your Functions for AuthorizationLevel.Anonymous, and require Authentication on your Function as Hury describes. This will not only require end users to authenticate, but supports System Assigned Managed Identity when your function is called from other App Services. Less keys to vault or configure means less to steal.
Depends on what you mean by authentication.
If you just want to secure your functions you can use the authorization level = function.
However, if you need authentication with login, and you need to know the user making the request, you have to use bearer token with OpenIDConnect server.
Always use stateless authentication regardless your method.
Related
I've implemented an ASP.NET Web API app as an Azure App Service. It has an App Registration, everything works as expected. I can hit the API from a browser and see all the JSON it returns. Now what I want to do is ensure that nothing except one or more applications from a set list can actually get anything from this endpoint. The applications needing access will all be custom ones in my organization/tenant. With all the flexibility and options, I'm having a very hard time determining what I need to do to lock the API down in this way.
I was envisioning having some client secrets the API knows about, and let the authorized applications supply them. Other methods would certainly be acceptable.
I'm certain this must be a duplicate question, but due to the plethora of information out there, and the myriad techniques for running applications on Azure, I can't seem to find just the right solution for my simple case.
It sounds like you have implemented interactive browser redirect-based authentication on the API.
Instead, you should implement JWT authentication on the API.
Then in Azure AD you can define permissions that can be granted to client applications.
In that way you can control which app can do what.
https://joonasw.net/view/azure-ad-authentication-aspnet-core-api-part-1
https://joonasw.net/view/azure-ad-authentication-aspnet-core-api-part-2
https://learn.microsoft.com/en-us/azure/active-directory/develop/scenario-protected-web-api-overview
https://learn.microsoft.com/en-us/azure/active-directory/develop/v2-permissions-and-consent
I have configured Azure Application Insight for monitoring our systems and was trying to enable the alerting. I'm using app insight availability test which provides a functionality to call a webhook URL.
I wrote a webhook using HTTP triggered Azure function, but the problem is it exposes a public URL which if called will raise an alarm on our internal alerting system. So I plan to authenticate the call to webhook.
Is there any way I can authenticate the call possibly using OAUTH.I don't want to provide the token in URL, looking for something secure. Another problem with manually using token in URL is that token rotation will require manual work.
Any suggestions on I can automate this task which will take care of secret rotation will be appreciated.
I believe token based authentication is the only possible route as of today as documented here.
But I think you should still be able to use a Function App without worrying about key rotation since the function keys can be read through the Functions API if the AzureWebJobsSecretStorageType app setting is set to files as documented here.
I'm using Azure Functions with my app, most functions needs to be protected by the authentication scheme I've set up however some functions need to be accessible anonymously.
What I'd like to accomplish with this design is to have my app pass in a refresh_token to the azure function which contains the client secret to refresh the token for the user without the end device ever needing to know about the secret key.
Another option I can do is have a separate azure project with some publicly accessible functions.
You have 3 options when doing Auth in Azure Functions:
Use API Keys via the code query/header (authLevel setting in function.json in front of individual Functions.
Use "Easy Auth" which can put AAD in front of all your Functions
Do it yourself
I'd recommend just using a jwt library or something similar to do it yourself if you're doing something fancy.
I also recommend not having unauthenticated and authenticated Functions on the same Function App, just create two different Apps. This makes it harder to accidentally have escalation of privilege issues pop up.
I'm making an iOS/Android app using Xamarin (not Xamarin.Forms, just regular Xamarin). I'm using the shared library set up rather than PCL. I want my app to call an Azure function but I'm unsure of the safest/best way to handle this. I have it set to "Function" for the "Authorization level". The test URL includes the "?code=..." portion in it. I was under the impression that if I put that in my C# code with the "code" value exposed that it was considered a bad idea from a security perspective.
I'm lost as to the safest/best way to deal with this. I've read that setting it in app.config is also a bad idea. I found some references for a web app that suggest using the connection strings that are available in the azure portal, but since this isn't a web app, I'm unsure of how I'd actually retrieve those values in my code (or if that's even possible).
So how would you suggest I handle setting the value for "code" so that I can call my function and avoid a security problem?
UPDATE: Providing more info as per request:
I'm using MSAL to authenticate my users with a B2C active directory. I already have that part working and have received a token authenticating the user.
I also just now enabled authentication in my functions.
I was under the impression that to call my function from my mobile client I had to make a new HttpRequestMessage. I'm unsure of then what I'd place in it to pass my token along.
Just to make sure I understand, your concern is about embedding secrets (the ?code=XXX value) in your iOS/Android app, correct? If so, yes, this is generally considered bad security practice. It's best to assume that anyone who can download your app will have the ability to discover these secrets and use them any way they want.
The recommended way to authenticate with a backend service, such as Azure Functions, from a mobile device is to use interactive authentication - i.e. some kind of OAuth flow. You can build it yourself, or you can use the built-in functionality of Azure Functions and Azure App Service to help you (Azure Functions is built on top of App Service). Here is a resource which might be useful:
https://learn.microsoft.com/en-us/azure/app-service/app-service-authentication-overview
https://contos.io/working-with-identity-in-an-azure-function-1a981e10b900#.vcjit3ntw
The API Key (code) is indeed not meant to be used by clients you distribute externally, so it shouldn't be used by your mobile app.
The most straight forward option here would be to use the built in App Service Authentication features with Azure Functions and implement an authentication flow in your app, which would allow you to securely authenticate the user.
Sharing more information about your scenario may help identify alternatives.
I am using Nodejs,expressjs,and mongoose to develop a application.Now what is procedure or way to identify that the request hit of my rest api service is from my front end application not from any unknown request.
If your front end application is a browser web page, then there is no real way to limit your REST API service to only your web app.
The issue is that by its very nature the REST API service is available on the web to any client that wants to access it. You could add some authentication (some sort of secret key) that is required before the REST API service can be accessed, but you cannot hide that secret key in a browser web page. If the browser web page can get access to the key, then so can anyone else who looks at the code in the web page or on the wire.
Because browsers, by default, will not allow cross origin Ajax calls, you are already protected from some other web pages (on a different site) using your REST API service from the browser. But, other servers can still use your REST API service.
One common way that services attempt to manage the use of their APIs is that they require an API key be obtained for each legitimate use of the API. If a particular API key is found to be abusing the service, you can revoke the privileges of that API key. You can grant your own applications API keys (embedded in your web pages ) and you can even change those web keys regular (such as daily) to keep people from copying them once and then using them for a long time. But a determined hacker will still find a working API key and use it for awhile.
One common way that services attempt to prevent excess usage of their API and protect the integrity of their service is to implement rate limiting. You establish what you think is a reasonable number of API calls per second (or some such metric) that your own app would not exceed and you measure the number of API calls coming from each endpoint and if they exceed some threshold, then you either delay or deny or error their calls until they stop exceeding your threshold.