I need to understand if a refresh token from OAuth 2.0 for Google data expires or not if unused for more than 6 months?
At many places it is called out that it doesn't expire and at some places it is said that it will expire if unused for 6 months.
For example, in this question, the accepted answer says that it never expires but one of the comments suggest that it can expire if unused for 6 months.
This Google doc calls out that refresh token will never expire while this doc says it can expire if not used for 6 months.
Although I am using a safety check for the cases where refresh token is expired due to any reason, but still want to make sure I understand the behavior correctly.
You are correct the two pages Using OAuth 2.0 for Web Server Applications and Using OAuth 2.0 to Access Google APIs don't have the same information.
Using OAuth 2.0 to Access Google APIs is correct.
You should write your code to anticipate the possibility that a
granted token might no longer work. A token might stop working for one
of these reasons:
The user has revoked access.
The token has not
been used for six months.
The user account has exceeded a certain
number of token requests.
There is currently a 25-token limit per Google user account. If a user
account has 25 valid tokens, the next authentication request succeeds,
but quietly invalidates the oldest outstanding token without any
user-visible warning.
If you need to authorize multiple programs, machines, or devices, one
workaround is to limit the number of clients that you authorize per
user account to 15 or 20. If you are a Google Apps admin, you can
create additional admin users and use them to authorize some of the
clients.
A refresh token that hasn't been used for 6 months will expire.
I have sent in a bug report on the first URL. Google should clear up the discrepancy the next time they go though the documents.
Related
I've seen this issue in a lot of questions, but so far, none seem to apply to my situation.
The problem we are having is we are getting an "invalid_grant" error when we attempt to get an access token. This only happens to some accounts, but when it does happen, in every case I looked at, the refresh token worked before, and now has stopped working. This is happening far to frequently for it to be customers revoking access (seems to be nearly 20% of the channels we manage in the last couple weeks have been invalidated).
As a note, we have a backend process that uploads the videos to our customer's YouTube channels.
We use OAuth2 to get a refresh token, here are the parameters we send...
scope = "https://www.googleapis.com/auth/youtube",
client_id = "",
response_type = "code",
access_type = "offline",
approval_prompt = "force",
redirect_uri = "http://www.us.com/OAuth/YouTube"
NOTE: for client_id we use the email address that is in the Google API manager (or was, I just looked and it is no longer there). We used to use the client ID from this page, but that caused us problems as well. Did this change? Should we be using the client ID from this page now?
We exchange the code that is returned for a refresh and access token and store the refresh token in our database.
The backend process exchanges the refresh token for an access token and this is where we seem to be getting the "invalid_grant" error.
Guaranteed only a single access token for the channel is in use at any time (25 limit doesn't apply). We don't store the access token, we get a fresh one every time we process a channel.
Any ideas what might be happening? Something to look for? See note above about client ID. This might have something to do with it, but I'm hesitant to try it since using the "Client ID" from the API manager caused problems before.
Guaranteed only a single access token for the channel is in use at any time (25 limit doesn't apply). We don't store the access token, we get a fresh one every time we process a channel.
This statement is incorrect: Access tokens can be used as many times as you need while they are still good (for an hour).
Answer:
"invalid_grant" basically means that your refresh token no longer works. The only solution to the problem is to request access again and get a new one. The question should be why is it expiring in the first place.
Assuming that the user did not revoke access, and that the refresh token has been used to request a new access token within the last six months. This is probably an issue with it being over written.
When a user authenticates your application you are given a refresh token. This refresh token is associated to the client id of your application and the user who has just authenticated. If said user then authenticates your application again you will get another refresh token. Again this refresh token is associated to the user and your projects client id. Both of these refresh tokens will work. Your user can keep doing this up to 25 (Note I think the changed it recently to 50 but I haven't tested it with all APIs yet) once they have hit this magic number the first refresh token will expired and if you try and use it you will get an invalid grant.
The only solution is then to just request authentication again. It is important to always save the most recent refresh token that your user has granted your application. In the event (like me) you have an application that is stored on a number of servers all requiring authentication. Your going to have to tell them not to refresh it to many times or they will have to go back and reauthenticate the first one that they expired.
If this is happening with ALL of your requests. You can also check that you server is sync with (NTP) and that you are sending the payload of your request in the post field. Not attached to the authentication end point like a HTTP GET (been there done that).
Here are the possible reasons why a token stops working and becomes invalid:
The user has revoked access.
The token has not been used for six months.
The user changed passwords and the token contains Gmail scopes.
The user account has exceeded a certain number of token requests.
As you can see, it's not recommended that you request a fresh one every time you process a channel. As also mentioned in Token expiration:
If you need to authorize multiple programs, machines, or devices, one workaround is to limit the number of clients that you authorize per user account to 15 or 20. If you are a Google Apps admin, you can create additional admin users and use them to authorize some of the clients.
With regards to the use of client_ID, it is usually needed to call the sign-in API as mentioned in Creating a Google API Console project and client ID.
And lastly, this Google Groups discussion - OAuth 2.0 400 - error:invalid_grant and ideas? might also help.
I am implementing an App Store for my application where third-party developers can build there own apps based on my API. I have everything working and understand the concepts of OAuth 2.0, but I don't see how an external app can have timeless access with an access code that expires after one hour. Now you can use a refresh token to request a new one, but that one expires after some time too.
So how can an external app continuously connect to my API when the user of that app allows it only once?
My authorization codes expire after 10 minutes, the access tokens after 1 hour and the refresh tokens after 2 weeks.
I don't see how the app can retrieve data after those periods of time without the user re-allowing/re-installing the application through oauth.
How are bigger companies like Facebook etc. approaching this? Do they have an access token that never expires?
Expanding on my comment, the general recommendation when using bearer tokens is that their lifetime should be reduced in order to mitigate the impact of an access token being compromised.
On the other hand, asking the user credentials every hour or so would be an UX nightmare so OAuth 2.0 has the notion of refresh tokens which will normally have a longer lifetime allowing the application to request a new access token without requiring user intervention.
I'm unfamiliar with the implementation details around Facebook persistent tokens so I won't comment on that, but they are most likely safe. However, you're not Facebook, so my recommendation would be for you to follow public standards like OAuth 2.0/OpenID Connect instead of trying to provide a customized approach.
Regarding your comment about refresh tokens that never expire, it's an acceptable solution, but their lifetime is just one part of the equation. You should consider if they are multi-use or single-use, they can only be used by the client application that they were issued to, they should not be used by browser-based applications due to the difficulties of ensuring secure storage, etc.
Is there any maximum number of requests to get a brand new access token using a refresh token?
Yes. 25 according to Google's developer documentation
Access tokens have a lifetime of 3600 seconds. Requesting a new access token before that time is up works fine but it's inefficient for your app to do so often. I don't think Google publishes a limit on how many non-expired access tokens a refresh token can have but you may get errors and it's non-optimal.
For most apps, refreshing an access token 10 minutes before the current access token expires (later if your not to worried about clock drift) works well.
The number of requests depend on the authorization server security policy.
Some servers allow only one request (the refresh token is invalidate after the request), other servers may allow 10, 100 or even unlimited requests.
My app needs to access user's data even when the user is not present. So my request for authorization code includes access_type=offline meaning I will get back a refresh token if this is the first time the user authenticates my app. I save the refresh token and use it later on.
Everything works as expected and pretty well. But what bothers me is a statement in the documentation:
Note that there are limits on the number of refresh tokens that will
be issued; one limit per client/user combination, and another per use across all clients. You should save refresh tokens in long-term
storage and continue to use them as long as they remain valid. If your
application requests too many refresh tokens, it may run into these
limits, in which case older refresh tokens will stop working.
If I understand this correctly, it is possible the refresh token I save to become invalid if the user authorizes too many applications?! Is this correct? How should the application react in such situations? Ask for another refresh token?
Thanks in advance.
EDIT: I created a test PHP script that would request refresh tokens from 4 Google clients (by client I mean generated credentials in the Dev console). Three of them are linked to one gmail address and the forth to a different one. For the first email, I generated 2 projects and for the first project, I generated 2 client ids. So:
email X, project A, client id abc
email X, project A, client id def
email X, project B, client id mno
email Y, project C, client id xyz
I started the test by requesting a refresh token for each client. Then I requested 24 more refresh tokens for the first client id abc. At this point all refresh tokens were valid even though for email X I had 27 refresh tokens. Then when I requested another refresh token for client with id abc, the first one for this client got invalidated, so hitting the 25 token limit per email/client combination. All other tokens were still valid and I managed to generate new tokens for client def. This client is for the same project A and the same email X. So I can't hit the second limit. What do these statements mean is still a complete mistery to me:
https://developers.google.com/accounts/docs/OAuth2#expiration
If you need to authorize multiple programs, machines, or devices, one
workaround is to limit the number of clients that you authorize per
user account to 15 or 20. If you are a Google Apps admin, you can
create additional admin users and use them to authorize some of the
clients.
https://developers.google.com/accounts/docs/OAuth2WebServer#refresh
Note that there are limits on the number of refresh tokens that will
be issued; one limit per client/user combination, and another per user
across all clients.
It actually isn't as bad as you think. Refresh tokens are application specific, that meaning specific to your client id. If the user installs your application a number of times then they have a number of Refresh tokens related to your application.
I ran into this issue with a SSIS Connection manager if the user had my connection manager running on more then 20 SSIS packages the first one the installed would stop working.
https://developers.google.com/accounts/docs/OAuth2#expiration
Token expiration
You should write your code to anticipate the possibility that a granted token might
no longer work.
A token might stop working for one of these reasons:
The user has revoked access.
The token has not been used for six months.
The user account has exceeded a certain number of token requests.
There is currently a 25-token limit per Google user account. If a user
account has 25 valid - tokens, the next authentication request
succeeds, but quietly invalidates the oldest outstanding token without
any user-visible warning.
If you need to authorize multiple programs, machines, or devices, one
workaround is to limit the number of clients that you authorize per
user account to 15 or 20. If you are a Google Apps admin, you can
create additional admin users and use them to authorize some of the
clients.
So as long as your application isn't being installed more then 15 times by the same user you shouldn't have a problem. If it is a problem you can suggest that they use a different / dedicated login for your application.
Facebook's deprecation of the offline_access permission is coming May 2012 and the documentation isn't giving us enough information on how to handle it.
We have an iOS app and corresponding service that powers it and integrates with Facebook in a deep way to leverage a user's friend list within out app (so if your FB friends are also using the app you can more easily connect). This is like how all social apps seem to work, so nothing special here.
Client
Our app uses Facebook iOS SDK to allow user to login, which we currently ask for offline_access. The token is persisted in our iOS app, but also sent to our server where it is saved. The client acts on behalf of user to post updates to a user's newsfeed (we also ask for publish_stream permission).
Server
Our server periodically checks to see if user's FB friends are now using our app. Next time user signs in, we expose content and relationships in a certain way to promote that user's friends. The server also acts on behalf of the user to periodically connect to the graph API and get the user's current friends list. This is so we can account for changes in a user's relationships and have them reflected in our app. We do this when the user isn't currently using the app so they have the best experience the next time they do use it. To enable this, our iOS app sends the access token to our server which it uses and why we ask for offline_access.
Note: If user signs out of our app explicitly, we delete the access tokens from both client and server.
Problems
Now that there is no longer a perpetual access token we can use, I'm trying to figure out the best practice for still enabling our scenarios while leveraging facebook's new intended way of handling and extending access tokens. The documentation is unfortunately not totally helpful.
Questions
A. When you authenticate through the newest Facebook iOS SDK, what is the default lifetime of the access token you get? This document says an extended token request will give you one that lasts 60 days. This other document talks about the first access token request and mentions varying validities but it's unclear and does it talk about specific validity times:
(emphasis is mine)
When you obtain an access token from Facebook, it will be valid
immediately and usable in requests to the API for some time period
defined by Facebook. After that period has elapsed, the access token
is considered to have expired and the user will need to be
authenticated again in order for your app to obtain a fresh access
token. The duration for which a given access token is valid depends on
how it was generated.
There are also events which may cause an access token to become
invalid before its expected expiry time. Such events include the user
changing their password, an application refreshing it's App Secret.
Dealing with varying access token expiry times, and handling the case
when an access token becomes invalid before its expected expiry time
is essential for building robust social experiences.
B. For the client, now that the access token isn't necessarily long lived, is the right approach for us to:
Let use login through FB, then detect whenever the access token is expired. If it is, then call into FB iOS SDK to re-authentication/re-authorize? (this should just trigger user to bounce out to FB iOS app, and in most cases come immediately back to our app with a new access token).
C. According to this blog post I found, you can only extend an access token once:
Can I exchange my 60 day access token for a new 60 day access token?
No, sorry you cannot. You can only exchange a valid (meaning current)
user access token for an extended one. You cannot extend an already
extended access token.
On the client, I can just handle this by prompting a re-authentication/re-authorization as I mentioned in Question B. However, this doesn't work on our server. We could certainly have the server renew it once to 60 days, but what happens on the 61st day? The server just stops being able to sync the friend's list?
D. It seems to make sense to check the validity of the FB access token every time the app starts or re-hydrates from sleep. What is the best way for our iOS app to check this? Is there a recommended endpoint to call to validate a token? Should we just call into https://graph.facebook.com/me passing the access token and checking the response?
Note: we can certainly record the expires time when we get the initially extended token, but this isn't reliable since the user could revoke our app's permission anytime which makes the expires time an unreliable data point on validity
Overview
I believe that the root of what facebook is trying to achieve is to prevent an app from having perpetual ever-lasting access to a user's account. So, with the new migration an app can only access an account for 60 days unless the user signs in again.
I don't work for facebook, but here are my findings from playing around with the facebook graph api.
General Solution
Whenever a user signs in, take their access token and immediately extend/refresh it, and save it
Record the expiration date of the access token
When an access token expires (either from the recorded date, or a graph API exception telling you so), then notify the user that you don't have access, and ask them to sign in again.
Answers
A. When you authenticate through the newest Facebook iOS SDK, what is the default lifetime of the access token you get? This document says an extended token request will give you one that lasts 60 days. This other document talks about the first access token request and mentions varying validities but it's unclear and does it talk about specific validity times:
Here's how it works:
The first sign-in grants you approximately two hours
By refreshing the access token, you can get up to 60 days
If the user doesn't sign in to those 60 days, there is no way to get access for longer without having them sign in.
If the user de-authorizes your app, that 60 day windows ends immediately, and you will no longer have access.
B. For the client, now that the access token isn't necessarily long lived, is the right approach for us to: Let use login through FB, then detect whenever the access token is expired. If it is, then call into FB iOS SDK to re-authentication/re-authorize? (this should just trigger user to bounce out to FB iOS app, and in most cases come immediately back to our app with a new access token).
If the users access token is expired, your only option is to have them go through a login loop like you are talking about.
C. According to this blog post I found, you can only extend an access token once. On the client, I can just handle this by prompting a re-authentication/re-authorization as I mentioned in Question B. However, this doesn't work on our server. We could certainly have the server renew it once to 60 days, but what happens on the 61st day? The server just stops being able to sync the friend's list?
You can only extend an access token once. On the 61st day, you are out of luck. Best notify the user and let them know that unless they sign in, you won't be able to do anything.
D. It seems to make sense to check the validity of the FB access token every time the app starts or re-hydrates from sleep. What is the best way for our iOS app to check this? Is there a recommended endpoint to call to validate a token? Should we just call into https://graph.facebook.com/me passing the access token and checking the response?
I haven't be able to find an API equivalent of the Debug Console. This FB blog article talks about invalidated access tokens, but doesn't mention any API methods in particular meant to test the API.
I your suggestion of hitting https://graph.facebook.com/me would work just fine is exactly what they recommend in their example. In fact, I might use this approach in my app as a pro-active way of checking an access token.
Tid Bits
When you "refresh" an access token, a new access token will be returned. The response looks like: access_token=TOKEN&expires=5183912
You can only "refresh" an access token once. If you try to "refresh" the long-lived token returned from a previous call, it will return the same token, but doesn't throw an exception unless the token has expired. (in other words, you can safely try to refresh your token)
The default access token length seems to be around 2 hours
If you "refresh" an access token, that new access tokens seems to be the one that you'll get from the facebook API afterwards (instead of returning the original, short-lived access token)
Also, if you want to play around, these tools make it easy to test out your use case in a browser before burying it in your code:
Graph API Explorer - For creating and getting access tokens
Debug Console - For checking the expiry date of tokens before/after refresh
Refresh Endpoint - For manually testing extending your tokens
Great answer, one important addition : the default token lasts between 1 and 2 hours. You get the remaining of the hour during which the user signs up, plus 1 full hour. For example if a user signs up at 3:45pm, the access token will expire at 5pm. To be safe developers should assume it only lasts 1hour.