Our application uses oauth2 & openid connect for auth&auth. It's built using an angular client that calls a REST API. I would like to know how to authorize access to the API, based on the possession of an unguessable url.
I'll explain this a little more. In the application, a user can invite another user. When this happens, an email is sent to the second user. When user 2 clicks a link in the email, he is sent to a webpage with details about the invitation.
Only user 2 should be allowed to see the invitation page. I was planning to solve this by using an 'unguessable url' in the email. Upon visiting the url, the user must somehow be authorized to fetch the invitation details from the API.
The question: how do I authorize a user, based on knowing the unguessable url? How do I assign a claim when the page is loaded, and how do I verify this claim in the API call that follows? The only solution I see, is to set a cookie containing a token. But this is not in line with our existing auth mechanism. I prefer not writing my own token validation code, and let the Identity Provider handle this.
Additional info: user 2 may or may not have an account in the system, and he may or may not be logged in. Neither should prevent the user from seeing the invitation details. In other words: a totally unknown user should be able to see the page. The knowledge of the url should be the only requirement.
Any solution to this problem? Or am I handling it all wrong?
After asking around, the general consensus is to NOT let the external auth mechanism take care of this, but to validate the link ourselves.
The solution is to turn the unguessable part of the url (the 'link id') in some kind of token, which can be validated upon calling the API. This is done by the API itself, not by the Identity Server.
Applied to the invitation issue: when an invitation is created, store the link id together with some info, i.e. what kind of access it allows (invitation access) and the id of the invitation. When the user calls the API to get the invitation, pass the link id for validation. Match the invitation id with the invitation id stored in the link, and if it doesn't, throw an error.
Related
I am currently using a client-side React component to have a user login to Facebook via OAuth in my application. On the server-side, I use the npm package passport-facebook-token to validate the authenticity of the accessToken after a successful client-side login.
One practice I do not see often is in addition to asking Facebook if the accessToken is valid, shouldn't the server also check if the email provided by the client's payload matches the e-mail coming back from Facebook? Allow me to use defined client/server technologies to illustrate my question:
1) User uses React component on the client to authenticate with Facebook.
2) React component successfully authenticates with Facebook and fires an HTTP request to the server with an access token and the user's email.
3) The server, running Node.JS and passport-facebook, now needs to verify the authenticity of the access token directly from Facebook. Facebook does not care for an e-mail. It will just verify the access token.
4) Facebook returns a response to Node.js confirming the authenticity of the access token. The response also contains other metadata about the user, including their email and other profile data.
My question is, should Node.js take the email that's also coming back from Facebook's access token verification payload, and verify that it is what came back from the React client? Would this not prevent someone from brute-forcing an accessToken and require them to not only have an accessToken but also know who the accessToken belongs to? This could prevent a user from submitting a bunch of HTTP POST requests to the Node.js server attempting different access tokens. They would not only have to guess an access token assigned to the application's clientID, but also know the e-mail it belongs to. Is this an over-engineered approach?
Really the best way I can think of to make your OAuth accessToken and 'code' value less prone to brute-forcing is using a Cryptographic Number Generator to create a 128-bit length string of random data and encoding it with base 64 to use as your code. It's extremely unlikely that it would be guessed by a computer or by someone redirecting to and from the authorization endpoint and the redirect-uri with query parameters.
Another method of fortification is limiting the rate of authorizations by IP address (which you can do instead of email through Node.js) but that is usually not a problem for most well-equipped hackers. I highly advise the first method for creating a more secure service.
Your approach to validate the email as well as the token is a bit superfluous because Facebook's opaque user access tokens are inherently tied to email.
From Facebook
An access token is an opaque string that identifies a user, app, or Page
"opaque" is defined by Auth0 here
Opaque Access Tokens are tokens in a proprietary format that typically contain some identifier to information in a server’s persistent storage
In your case, the identifier is the user's email, and the server belongs to Facebook.
I will elaborate further. Here is your step by step with some edits:
User uses React component on the client to authenticate with Facebook, inputting both their email and password directly to Facebook. React component gets the token from Facebook on login success.
React component successfully authenticates with Facebook and fires an HTTP request to the server with an access token and the user's email.
The server, running Node.JS and passport-facebook, now needs to verify the authenticity of the access token directly from Facebook. Facebook does not care for an e-mail. It will just verify the access token because the access token is already tied to the email.
Facebook returns a response to Node.js confirming the authenticity of the access token. The response also contains other metadata about the user, including their email and other profile data.
This is Facebook's bug bounty program. If their OAuth was really as cracked as to require a second email validation, it would have been patched almost immediately by this incentive.
I'm working on creating a REST API and one feature is to allow users to register. The general flow is the following:
The user specifies his email and password using the client application (SPA application) and presses the submit button.
A request to the API is made. The API adds the user to the database, generates a verification token and sends an email to the user.
The user verifies his email and clicks a confirmation link.
The API marks the user account as verified.
My question is regarding the confirmation link.
Should the link point to the client SPA application? In this case, the client application will make a POST request to the API with the verification token and the user email.
Also, how should the API know the link to the client application (the link needs to be added in the email and this is done by the API). Should the API store this link, or should the SPA client send the verification link to the API when sending the request to register the user?
Another approach would be for the link to go to an endpoint defined by the API. In this case a GET request will be made with the user email and verification token and the API will set the account as verified and inform the user that his account is now active.
I have read that this approach doesn't conform to the REST principles because a GET request should never change the state of a resource. In this case, the user resource will be modified.
I'm not sure which of the 2 solutions is better or if there is a better solution, so my question is what is the best approach?
Thanks!
Should the link point to the client SPA application?
If your 'Client SPA application' is the sole frontend for end-users, then yes: it should point there. Some people deploy a separate oauth2 / authentication server but that doesn't sound like it's the case here.
The client application will make a POST request to the API with the verification token and the user email.
The token should be enough. I'd avoid sending email addresses through urls.
Also, how should the API know the link to the client application (the link needs to be added in the email and this is done by the API). Should the API store this link, or should the SPA client send the verification link to the API when sending the request to register the user?
Both seem like really valid designs. If you want the API to be completely unaware of the front-end and support a multitude of frontends, it would make sense to me that the client sends their own endpoints. There is a security concern though, you don't want arbitrary clients to register arbitrary urls.
If you're just building a single frontend, I don't see a problem with the API knowing the activation url. It also sounds like it would be easy to change if your requirements change later.
I'm not sure which of the 2 solutions is better or if there is a better solution, so my question is what is the best approach?
Ultimately it doesn't really matter that much. Neither approach sounds like you're really painting yourself into a corner. Either you have a standard endpoint that uses a javascript HTTP request to activate a user, or you have a separate endpoint that redirects a user after activation. Both will work.
I would like to ask little theoretically.
I have an angular6 + spring app that has its own client, app-specific client data.
These data can be divided into two groups
managment-data: Like client roles that allow client to visit different parts of app
client-data: personal settings, history of activities etc.
Because I would like to make login as user-friendly as possible, I would like to implement facebook login.
After user click "FB login button", facebook returns me some-user info and mainly a security token. How could I use this to securely communicate with my BE.
When someone sends request to BE, I need to be sure, that its the same person that logged in to facebook.
If I send this token as part of request, what stops possible attacker to somehow obtain token and then impersonate original user?
In what form I should send data I got from Facebook to my own server?
How should I work with token on server?
How can I validate its authenticity?
Thank you for answers
Filip Širc
You should look into the usage of OpenID Connect along with OAuth protocol. It allows you to authenticate the user to your client application (Angular6 + Spring app) to verify the user details.
When you are sending an access token to access a certain resource, you should avoid sending it as a request parameter. Usually it is encouraged to send it under the Authorization header of the request as a bearer token. However, if you want it to be extra secure, you could encode the token before sending so that it would be difficult to decode it and steal any valuable information.
Also, when you are sending sensitive information, it ise better to send them in the form of a JSON Web Token (JWT). You can use a third party library to create a jwt to include the information that need to be sent to the server. You can sign the jwt with your own signature which can be validated later. Refer https://www.rfc-editor.org/rfc/rfc7519 for detailed information about jwts.
You should use the claims in your access token to grant a user access to the resource you are protecting. Since most of the tokens are sent in the form of jwts, you can decode them and get check the necessary claims such as scopes, audience (client app), subject (user), etc.
Most importantly, you should validate the signature of the token sent from Facebook to make sure its an authentic one. For this, you have to get the public key details from Facebook's jwks endpoint and validate the signature using a third party library (auth0, nimbusds, etc.). Facebook's digital signature will be unique and this verification process is the best way to ensure the security. Also, you can check whether certain claims in the token match your expected values to validate the token. This can also be done through libraries such as ones mentioned above. Here's auth0 repo for you to get a general idea.
I've been reading a lot about the topic but all I find are obsolete or partial answers, which don't really help me that much and actually just confused me more.
I'm writing a Rest API (Node+Express+MongoDB) that is accessed by a web app (hosted on the same domain than the API) and an Android app.
I want the API to be accessed only by my applications and only by authorized users.
I also want the users to be able to signup and login only using their Facebook account, and I need to be able to access some basic info like name, profile pic and email.
A possible scenario that I have in mind is:
The user logs-in on the web app using Facebook, the app is granted
permission to access the user Facebook information and receives an
access token.
The web app asks the API to confirm that this user
is actually registered on our system, sending the email and the
token received by Facebook.
The API verifies that the user
exists, it stores into the DB (or Redis) the username, the token and
a timestamp and then goes back to the client app.
Each time the
client app hits one of the API endpoint, it will have to provide the
username and the token, other than other info.
The API each time
verifies that the provided pair username/token matches the most
recent pair username/token stored into the DB (using the timestamp
to order), and that no more than 1 hour has passed since we stored
these info (again using the timestamp). If that's the case, the API
will process the request, otherwise will issue a 401 Unauthorized
response.
Does this make sense?
Does this approach have any macroscopic security hole that I'm missing?
One problem I see using MongoDB to store these info is that the collection will quickly become bloated with old tokens.
In this sense I think it would be best to use Redis with an expire policy of 1 hour so that old info will be automatically removed by Redis.
I think the better solution would be this:
Login via Facebook
Pass the Facebook AccessToken to the server (over SSL for the
android app, and for the web app just have it redirect to an API endpoint
after FB login)
Check the fb_access_token given, make sure its valid. Get user_id,email and cross-reference this with existing users to
see if its a new or old one.
Now, create a random, separate api_access_token that you give back to the webapp and android app. If you need Facebook for
anything other than login, store that fb_access_token and in your
DB associate it with the new api_access_token and your user_id.
For every call hereafter, send api_access_token to authenticate it. If you need the fb_access_token for getting more info, you can
do so by retrieving it from the DB.
In summary: Whenever you can, avoid passing the fb_access_token. If the api_access_token is compromised, you have more control to see who the attacker is, what they're doing etc than if they were to get ahold of the fb_access_token. You also have more control over settings an expiration date, extending fb_access_tokens, etc
Just make sure whenever you pass a access_token of any sort via HTTP, use SSL.
I know I'm late to the party, but I'd like to add a visual representation of this process as I'm dealing with this problem right now (specifically in dealing with the communication between the mobile app and the web api by securing it with a 3rd party provider like facebook).
For simplicity, I haven't included error checks, this is mostly just to outline a reasonable approach. Also for simplicity, I haven't included Tommy's suggestion to only pass your own custom api token once the authorization flow is over, although I agree that this is probably a good approach.
Please feel free to criticize this approach though, and I'll update as necessary.
Also, in this scenario, "My App" refers to a mobile application.
I'm working on a proof of concept app. The basic functionality works, where I can log into one website, link to another site that shares the same STS, and the partner site picks up the credentials properly.
However, the partner site only requests the token if the page that we link to requires authentication (which kind of makes sense I guess).
Ideally, I'd like to link to a partner page that does not require you to be authenticated, BUT if the user IS already authenticated, I'd like to at least be able to recognize them on the partner site.
Currently, if my partner landing page does not require authentication, it doesn't appear that the user is logged in when they arrive. As soon as the user requests a page on the partner site that does require authentication, it then grabs the token without requiring the user to log in.
I've tried playing around with the SecurityTokenReceived and RedirectingToIdentityProvider events, but so far I'm stumped.
Any thoughts are appreciated.
So, the problem you are running up against is in dealing with the SessionAuthenticationModule hijacking the request. This module is responsible for detecting if the user has a valid session (based on a cookie that is written upon a successful redirect from the STS) and if not, to redirect the user to the STS to fetch a valid token. The WSFederationAuthenticationModule supplies the eventing necessary to hook into various stages of the redirection/authentication process.
Based on your description, it sounds like you want the following to happen:
User clicks on a link that redirects to the partner site
At the partner site, the request is intercepted and the system determines if the user is signed-in to the STS or anonymous
If the user has a valid session with the STS, then pull the claims for that user
The problem is, your RP cannot know that the user has a valid session without sending the user to the STS first (the RP's do not talk to each other or the STS. The user's brower is used as the means of communication between the RP's and the STS in the form of WS-Fed directives and SAML tokens passed in the url during redirects). If the user is sent to the STS, then they must authenticate, which could be a problem for anonymous users.
So, I do not think there is a "trick" that you can pull via configuration or interception of the request to determine if the user has a valid session with the STS. You might be able to pass a hint, however, from the referrer that is intercepted by the partner site. This hint could take the form of a parameter on the url that indicates to the partner site that the current user has a valid session and to go ahead and redirect to the STS (absence of this hint would indicate an anonymous user). You could also build a system to "hand-off" knowledge of the signed-in user using a resource that both sites have access to (i.e. database).
As you are sure to learn soon, more often than not, WIF offers pieces to the puzzle, but every situation is different and you have to supply the other pieces on your own.
Hope this helps!