As part of a trust-less system, I plan on using OpenID to generate a client-side secret. To do so, the idea is to use the authentication implicit flow of the OpenID Connect protocol, and let the user confirm he is who he says he is :)
As far as I understand, the sub property you get back is a unique identifier of the user. This is good. However, from what I've read, this sub can either be specific for a given client (good for my purpose, could be used as the secret), or shared amongst all clients. This is not good in my case, as any bad actor could find out about this identifier through another app and use it as a secret in my system.
Two questions :
is my reasoning sound ?
is there any other property in either the OAuth or OpenID protocols that could be used as a secret, because it would be both unique for that user AND specific to my app ?
Cheers
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I read a lot about OAuth 2.0 and OpenId Connect and in theory I understand both concepts now.
But if I go into practice, some things are still confusing for me and I hope you can enlighten me in some way...
First thing is, that in all code samples how to secure a .net core API in an AAD-environment I find lines like this in the configure-section:
app.UseAuthentication()
and lines like this in the ConfigureServices section:
services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
.AddJwtBearer(options =>
{
options.Authority = "https://login.microsoftonline.com/xxxxxxxx";
options.Audience = "xxxx-xxx-xxx-xxx-xxxx";
});
However, to access my API I am not using an ID token, but an access token what is Authorization, not "Authentication" like in the code samples.
This works - but I do not understand it 100%.
So my first question is:
Is the access token also "authenticating" in some way?
The second thing:
I read that access tokens have no standardized format. They can be JWT or not, can have an audience or not etc. For this reason you could even put user information in the token like microsoft does. The access tokens contain claims like a "family name" or "given name" etc.
Id tokens in contrast have a standardized format to ensure that authentication is done in the same way by everyone.
If people are accessing my apis with an access token, I can read their name or e-mail address with "user.identity.name" for example. This value I can use to store the information who edited something or who inserted something.
So I am fetching information about the user with access tokens!
So my second question is:
Am I doing the right thing here? Or should this be done in another way.
and:
Should access tokens ever contain information about the user?
Is the access token also "authenticating" in some way?
Yes.
Your API is validating the access token when it receives it.
This is the authentication part, when your API verifies that the token signature is valid, came from the Azure AD tenant that you trust, that it is meant for your API and that it has not expired.
The authorization is when you check what permissions the token contains.
Your API can define different permissions that are given to client applications, allowing them different levels of access.
A valid token can pass authentication, but it might not pass authorization if it lacks the necessary permissions.
Am I doing the right thing here? Or should this be done in another way.
Fundamentally your are doing the correct thing.
The token tells you who the user is that is using the client application, and if you need to know who it was who did something, that's the info you use.
However, if you really want to connect an action to a user, I suggest you use their object identifier / object id / oid instead of their name / username as those can change.
Unless you just want their display name.
Should access tokens ever contain information about the user?
In the context of Azure AD, an access token will always contain info about the user if a client application is accessing an API on behalf of a user.
This includes authentication flows like authorization code, device code, implicit, and on-behalf-of.
They all use delegated permissions aka scopes to call APIs on behalf of the user.
Thus the token contains info about the calling app and the user.
If an app acquires an access token using the client credentials flow where a user is not involved, there will be no user info in the token.
In this case, application permissions are used instead of delegated permissions in Azure AD.
An application acts as itself, not on behalf of any user.
If your API supports both of these scenarios, sometimes the tokens contain user info and sometimes not.
The part about token formats is basically correct from a specification standpoint.
OAuth doesn't define a strict format for access tokens, while OpenID Connect does define one for ID tokens.
Using an access token to call your API is definitely correct.
The ID token is only meant for the app that initiated the user authentication, not for any APIs that it calls.
That's what access tokens are for.
if you check here: https://learn.microsoft.com/en-us/azure/active-directory/develop/access-tokens
in the newer access tokens, by default it follows the standard of not having any personal information about the user. which is what the standards suggest, Access tokens should not contain much or any information About the user. rather just information for authorization (things that user can access).
However you can always add the optional claims (and azure lets you do it) for personal info, but best practice suggests you shouldn't.
in terms of the addauthentication: Authentication is basically proving who you say you are. addauthentication(), basically calls microsoft azure ad to perform this task, saying hey aad please ask this person who he is, azure then checks and says ya this is a real person, but i won't tell you anything about him other than an id, and they have access to your api/application. So from your snippit, it's fine.
at this point, your serverside shouldn't have any personal information about the user, just that they have access and what scopes/roles. If it wants info about the user, it should then take that authorization (access token) and request it from whatever endpoint that token has access to (graph)
here's a great read about it: https://auth0.com/blog/why-should-use-accesstokens-to-secure-an-api/
Hopefully this helped clarify somewhat, and not add more confusion to the issue.
I have read a lot about OIDC and OAuth2, I know the id token is mainly used for the client to know who the user is and whether the user is still online currently.
Furthermore, Id token can prevent a class of impersonation attacks [You can find more details in this article].
But what if the id token is stolen? Can the attacker uses the id token to impersonate a user?
In our project, we just ensure https besides the OIDC. What else security consideration should I take to mitigate the impersonation attacks?
The goal or purpose of OIDC is not to be more secure than OAuth2, and this kind of comparison doesn't make sense. They solve different problems.
Let's start with OAuth2. In very short and somewhat simplified, OAuth2 solves the problem when a website holds data of a user, and that user wants to grant access to some of their data to another website. Say you have a Facebook account, but want to allow my application to access some of your data on Facebook, or for a more concrete example, you want to allow my awesomeapp.com app to post a link to your Facebook wall. For this, my website redirects you to Facebook, you log in, get an access token, and send that access token back to my website so that I can use it in your name to get what you allowed me to.
Note that there is one thing missing. I have no idea who you are. I just had an access token, with which I can do stuff, but I don't have identity info about you. Sure, this can be abused in different ways, the access token can hold your email address or whatever, but it's limited, the size matters, and there is no standard way.
At least not until OIDC comes in the picture. OIDC provides the identity element.
The purpose of the ID token is to provide identity info, to tell me claims about who you are. It may claim what your email address is, what security groups you are in, which company you work for, or anything else. Also it may be used to download more claims, in case they don't all fit in the actual token (see userinfo). These claims come from the Identity Provider, say Facebook, which my application then has to trust of course, i.e. I will believe whatever Facebook tells me about you.
This is all possible with pure OAuth2, but there is no standard, well known way to do so (or well, it is OIDC :) ). You could invent and implement something yourself, but these things are more complicated than they may first seem to be. That's why OIDC was invented, so you don't have to. But after all, OIDC is just a way to use OAuth2 to provide identity. In the end, it's just an extended OAuth2 if you like.
As for what security considerations you need to take into account - this part of your question is way too broad and can't be answered unfortunately. Security is a very complex topic.
I'm not really a security purist so my additions to Gabor's points are from a more practical viewpoint, as someone responsible for building well architected UIs and APIs:
An id token represents proof of authentication to a UI
An id token is NEVER used by APIs, which must use access tokens instead
An id token is the only type of token a UI should ever read, and it is mandated to have a JWT format
For Web UI logins an id token provides extra security, since it enables the UI to validate tokens and protect against some types of token substitution attack - so yes - OIDC is more secure
An id token is sometimes needed in order for logout to work
You should ALWAYS use a certified security library that does this type of work for you, rather than reading tokens directly in your own code.
My users authenticate via OpenID Connect, an authentication extension to OAuth2.
I'd like to secure my users' data by encrypting it using a key only they hold (not me).
In terms of repeatable state, all I get from OpenID Connect is a deterministic sub (subject) field. Which is a public identifier, hence unsuitable for key derivation.
Is there any mechanism or flow supported in the OpenID Connect or OAuth2 standards that will allow a user to either:
share a secret with me (upon login).
cryptographically sign a message for me.
I have been reading and searching and I just cannot believe that this requirement is not covered somewhere.
Maybe there exists a different protocol that is equally widespread and supported by common OAuth2 providers like Google, Microsoft, etc?
Any pointers will help. Thank you.
I understand the security issues around attempting to use OAuth for authentication from a provider's point of view. However I've been asked to provide users the facility to log on to a new web application using OAuth and obtain their basic identity info from the likes of Google and Twitter, from which a new user account within the client application will be created. Additionally users will be able to regster/login directly via user/passwords for anyone not wishing to use third party accounts.
We do not require any access to the user's details/info or providers APIs, just their basic identity when they first logon, and of course allow them to login via the provider in the future. Not exactly the use case OAuth is intended for, OpenId would have been preferred, but OAuth has been specified and without valid concerns would need to be adhered to.
My question is how safe is it to assume that the user has correctly authenticated themselves with the relevant provider. If I trust say Google to perform adequate authentication and I obtain an access token and their identity, presumably I can consider that a legitimate user? There are obviously issues if some one has access to the resource owners machine and saved passwords in the browser but that issue is present for those users who elect to register directly.
Presumably it possible to fake an access token, e.g. man in the middle pretending to be google? A MITM could fake an access token and supply identity details that matched a registered user's google id? I don't see anything for a client to know that the information definitely came from the provider. Obviously this problem is not unique to OAuth.
Are there another ways someone could illegitimately access an account that used OAuth to authenticate themselves.
OAuth allows that an application to access a specific user resource (that has been provided permission by the user) and it cannot go outside that scope. I have not seen the documentation that refers to creating a new user using OAuth based application.
That being said:
We do not require any access to the user's details/info or providers
APIs, just their basic identity when they first logon
This violates OAuth authorization process. The Service Provider does the authentication and provides the relevant tokens (based on the success of the authentication). This is to ensure that there are no 3rd party authentication done during the OAuth authentication process.
My question is how safe is it to assume that the user has correctly
authenticated themselves with the relevant provider.
This all depends on the service provider itself. To conform to OAuth protocol, one of the requirement is that user authentication must be done in a secured transport layer with a digital certificate (for HTTP, it must be done in HTTPS). OAuth consumer don't have any reference to the authentication process. Also the authentication process basically asks the user if the consumer can access the resource of the specific user (and not anyone else, since he doesn't have authorization to it).
Is it possible to fake an access token, e.g. man in the middle
pretending to be google?
Spoofing a Service Provider IS possible but it'll be tedious. For one, you will have to create a whole OAuth handshake process, create the exact API as the service provider, also setup an environment that is secured (as OAuth recommends). The only thing the spoofing service provider can obtain is the client credentials. If it has its user credentials, there is no need to use the application as there is no way of providing a user credentials using an application to do malicious damage.
Secondly, access tokens do expire so even if you spoof and retrieve an access token, the original application owner can ask for the service provider to block the application and the access token can be useless.
A man in the middle attack won't be possible. You will have to replicate the service provider in a sense that the end user won't be able to distinguish between the original and the spoofing service provider in order to capture all relevant credentials (from both the application and end user).
Sadly saying, the scenario from your last sentence is the truth.
But you should realise that the security is a huge and complex issue, especially in client side. It's not happen just in a single point but many points through the whole internet access life cycle. The scenario you given is not what OAuth try to solve.
I am working on an web application. Which uses oauth to authenticate from different services.
Is there any risk of securing these tokens and secret directly into database. Or should I encrypt them ?
What are the general security pattern for saving oauth token and secret
This thread answers all of your questions:
Securly Storing OpenID identifiers and OAuth tokens
Essentially, the following are dependent among themselves one or other way:
Consumer key
Consumer secret
Access token
Access token secret
Unless the consumer key/secret are also at risk, you don't need to encrypt the access token/secret. The access tokens can only be used in combination with the consumer key/secret which generated them.
I'm assuming you're talking about the typical "Service Provider," "Consumer" and "User" setup?
If so, the session and cookies are good enough for saving tokens, but the problem is that it's your Consumers (your clients, as I understand) that need to be saving them and not you. Is there a session/cookie available in the scope of the calls to your API?
In either case, if the tokens are stored in the session or cookies, they will be "temporary" keys and the User will have to re-authenticate when they expire. But there is nothing wrong with that as far as the oAuth spec is concerned - as long as the Users don't mind re-authenticating.
Also bear in mind that the tokens are tied to a given service and user, and not to any IP address or device UUID, for example. They could not be used with different API and secret keys, as they are tied to the application they were issued for.
This way the user can de-authorize on a by-application basis, and every app can have a different set of permissions (e.g. read-only access). So your answer is you don't need to encrypt them, and you need them in plaintext anyway (if you're the User).