I have an app which presents a login screen on first launch. When the user logs in, I give them an option to remain logged in. This establishes a session with an expiry on my server. What's the most appropriate way to do the following things:
Store whether the user is logged in or not.
Present the user with a login or logout option on application launch based on the validity
of their session.
End their current session if they choose to logout (or if their session is expired).
I'm guessing this is a common design pattern and there should be tried and tested ways to do this but I seem to be using the wrong terms to search because I haven't found a satisfactory answer.
Some ideas:
I would suggest you store your sensitive session information in the application's KeyChain. I wouldn't store here the state of wether the user is logged in or not, just store that in memory. Your webservice should be able to return an error when the session ceases to exist, or if the user has logged out.
If the backend determines the session's validity, then you should have a RESTful call where you can pass the session information, returning whether the session is still valid.
Again, if they choose to logout, then you could perform another call to your backend passing the session information.
For the Keychain, use the KeychainItemWrapper from Apple's examples.
Related
I am in the process to design a login for a new app that will be associated with a domain, i.e. be the counterpart to an SPA.
Obviously I want to use
iOS 11 Password Autofill, and
Shared Web Credentials
I have read the documentation on autofill as well as watched the WWDC video about it. Also, I checked the article on Shared Web credentials, which I think is older than the new, reworked autofill. Said article recommends:
Do not use the shared web credentials as your primary storage for secure user credentials. Instead, save the user’s credentials in the keychain, and only use the shared web credentials when you can’t find the login credentials in the keychain.
This strikes me a little odd, because it
- Means I have to cover more possible inconsistencies, i.e. synchronize the keychain somehow wit the shared web credentials (what if I have credentials in the keychain as well as the shared web credentials, but they're different?)
- Potentially leaves "garbage" behind in the keychain if my user user uninstalls my app (naturally I hope they won't ever do this, but let's be realistic, some will)
Especially the last point had always bothered me in the past (before shared web credentials and autofill were a thing, or when my app doesn't have an associated domain). Unlike on macOS, the iOS Accounts & Passwords feature (in the Settings app) doesn't list ALL passwords, but only the ones used by Safari (i.e. the shared web credentials), correct? Keychain Access on macOS instead offers a means to view and manage all credentials, even those that aren't synchronized over iCloud.
I understand why the same is not offered on iOS, but it also means that for those passwords that my app saves (locally) to "its" keychain "part" can only be managed if I offer a UI for this in my app. And if the user uninstalls the app before using this, the item will stay in the keychain, at least it was that way when I tried it a couple of years ago.
My main question now is, wouldn't it be easier to disregard the article's advice and only rely on the shared web credentials for password storage? That's the part they can edit in Settings (if ever need be) and also it will reflect any password changes done on the website. I would design my app like this then:
First launch: App starts on the Login screen and offers the username/password via Autofill
User logs in: App saves a simple flag in the shared user defaults indicating the user is logged in.
App gets relaunched, e.g. after a device reboot: The app skips the login screen due to the flag and gets the password and user name from the shared web credentials (assuming the user previously granted it permission, of course)
User explicitly logs out: The app deletes the flag, basically setting everything back to first launch
User deletes the username and password from the shared web credentials (e.g. in the Settings app or with Keychain Access on macOS): The app falls back to the login screen as soon as it detects this (e.g. when attempting a remote request, or after relaunch), regardless of the flag. I think this matches the user intention best (if you delete a password you don't want some apps to hold onto it until you log them out)
This setup would avoid any issues with different items in the keychain and shared web storage and it would immediately propagate updates done in the webpage to the app as well (which is what I'd intent for my app anyways). Is there anything that would keep this app flow from working?
(Note: I asked the same question on the apple developer forums, so if you see that as well don't be confused. I will update any potential answers from there to here and vice versa.)
Edit to address #Aaron's answer:
Thank you so much for the info. Your answer helped me realize I misunderstood something about shared web credentials: I assumed that for an app with associated domain, you can access the credentials without user interaction (after perhaps an initial authorization). Like you can set the checkbox on macOS when an application requests credentials. I now realize this is wrong and on iOS you would always have to verify with the user, thanks.
For completeness sake, I still want to point out some of the other things you said:
You are right, we will eventually use token based authentication, so I will save that in the keychain (probably in addition to the password, see below). I just tried to keep the question simple enough at first.
Our app is like an email client where you update new incoming "mail". The mentioned "login flag" in something like the user defaults would thus just indicate whether the app should behave as if subscribed to an inbox or not. Like in Mail, you wouldn't expect to have to login even after relaunch.
For this reason I will probably eventually save the user's password in the (local) keychain along with a token. If the token expires, I can request a new one without user interaction, that's important in our general site and app design. Only if that request fails I would use the shared web credentials (updating my local copy of the creds in the process).
For what it's worth, the last point you mentioned is probably debatable. On macOS, for example (where you can edit the entire keychain, not just Safari passwords) de facto logs you out of an app. Mail, again, as an example. If the keychain item for an inbox is gone, Mail re-asks that the next time it is launched and tries to access the content (effectively a "kind of" login in a way).
Again, thank you a lot for answering, now I can close an open todo. :) Also thanks to #HamZa for giving out a bounty!
Considering this advice:
Do not use the shared web credentials as your primary storage for secure user credentials. Instead, save the user’s credentials in the keychain, and only use the shared web credentials when you can’t find the login credentials in the keychain.
The main issue here is that the shared web credentials process is a little clunky — it requires user interaction and takes time to resolve the credentials. So if the user has already authenticated with your app you want to avoid showing them the login page at all. You can do this by storing credentials in your app's keychain where you can access them immediately without a network connection or user permission.
This doesn't mean you need to store the user's password in the keychain. Typically you would store something like an OAuth access token in the keychain. The presence of this token means the user is authenticated - and if an API endpoint rejects your token then you can take them back to the login page.
This suggestion:
User logs in: App saves a simple flag in the shared user defaults indicating the user is logged in.
is possibly insecure depending on what you're hiding behind the login page, but typically any content belonging to the user should require a valid token to access, not just a bool in the user defaults.
I think this matches the user intention best (if you delete a password you don't want some apps to hold onto it until you log them out)
I disagree with this; I would not expect an iOS app to log out because I deleted a password from my Safari keychain.
I am working on my own app that uses instagram; but I think that this question is generalizable:
If my app determines that there is no auth token and requires the user to login; what should be done by the app in the way of cleanup after its done?
does it : leave the user "logged in" and let it be the responsibility of the user to invalidate the token ?
or: should the app basically leave things at the same base state as it found it? Going along with this reasoning; then it would require the app to keep track of weather it logged the user in or were they already logged in " valid authorization token" before the app was run ?
thanks
You need to implement a renew mechanism for your token.
Basically check that the token is still valid, otherwise delete it and unlog the user.
To unlog, simple, just delete the token (and user related datas).
If your app requires for the user to be logged in then you can just check if there is a token before displaying the related view.
Your user is unaware of the token (and everything related to it) and that needs to stay this way, period. If the token needs to be invalidated at some point, your app needs to handle it.
I'm using firebase authentication for my app and I have the users sign up, login, and log out all set up and going. However, I'm a little confused on how to manage the state of the users login status. Currently, if a user is logged into the app, but doesn't use the app for an extended period of time, firebase doesn't recognize them as logged in. I'm looking at the documentation and the approach is a bit unclear.
Should I be storing a FIRAuthCredential every time the user logs in, and then call reauthenticateWithCredential using that credential?
Firebase Auth only requires recent sign-in for sensitive operations like: deleting a user, changing a user's email or password. These are for obvious reasons. You want to make sure it is the same user before making such sensitive changes. Otherwise, the user is considered signed in indefinitely by the Firebase Auth backend (your assumption that "firebase doesn't recognize them as logged in" is not correct). Of course, a developer may also require re-auth before other operations like updating credit card, shipping address, etc. A developer would check the auth_time on the Firebase ID token. Only in such cases would you re-auth. You should never store credentials such as password on the client to avoid prompting the user to reauthenticate. It is needed to protect the user's account.
yes I think that is going to be right approach or second approach you can try is like when a user press login button instead of directly calling Authenticate User put a check in which last login timestamp value will be stored when user login compare timestamp value and then perform selected operation as you want . NOTE - you will be required to check weather user exist or not , but I think first approach will be better as if you had noticed in many Social apps like kik it ask for reauthentication after a long period of time but first it authenticate user instead of displaying home screen it take to reAuthenticate screen
Context
I am using Parse.com as my backend for a mobile app. I use Facebook login only for now.
Assuming the user has logged in with Facebook and now has an account created on Parse already.
Question
Every time the user opens the app, should I do a check if his account is still valid by using PFUser.currentUser().become()? Or should I use the cached PFUser.currentUser()?
I have found out that if I delete the user account in the Parse backend, if I don't do a become(), the PFUser.currentUser() is still valid, even if the account does not exist anymore.
What is the best practice?
It's generally better to add a column to the user such as 'disabled', and when the app starts you can refresh the user, check that flag and display a message to the user and logout. That, from a user point of view, is similar to using become (at least as long as you check and notify the user).
So, you should do something if you're going to be removing or disabling users in the background. The main question is wether you fully delete the account or just delete the contents but leave the (empty) user in the system as a record.
I have a JSF login page using form authentication. I login users by calling HttpServletRequest.login(username, password). Logging out is done by first calling ExternalContext.invalidateSession() and then calling HttpServletRequest.logout() for the current user.
My plan is to keep track of the logged in user in an application scoped list by adding to the list anytime a user logs in and removing from the list when a user logs out.
I have two concerns with this approach:
If a user that was already logged in tries to log in again without first logging out, I want to invalidate the existing session and do some cleanup. How do I access the session for a given logged in user? I could also use this functionality to forcefully logout some users.
If a session expires (e.g. timeout) I want to remove the user from the list of logged in users. How do I listen for a session expiration?
Maintain a Map<User, HttpSession> logins in application scope yourself. During login, check if logins.put(user, session) doesn't return null and then invalidate it.
Let the User implement HttpSessionBindingListener and implement valueUnbound() accordingly so that it does a logins.remove(this). Or, if you don't have control over User, then implement HttpSessionListener#sessionDestroyed() instead to perform the remove.
Unrelated to the concrete problem, calling HttpServletRequest#logout() is unnecessary if you already invalidate the session. The user is tied to the session anyway.