How does gmail keep track of my sign-in status ?

ZoZoZo · 18-04-2021 12:57pm #1

Hi,

I'm trying to figure out how gmail keeps track of my signed in status. eg. if another site offers the option 'Sign in with Google' I enter my gmail credentials to get access to another site, if I then open Gmail in another tab it goes straight to my inbox (no credentials required) so it is clearly keeping track of the fact that I already logged in (albeit on another site). So, I'm trying to figure out how Google keeps track of my signed-in status ? I would have assumed it was via a cookie. So I go to Firefox -> preferences -> Privacy & Security -> Clear Data.
After this Firefox lists:
Cookies and Site Data (0 bytes)
Cached website content (0 bytes)
Yet if I open gmail in a new tab I'm still getting straight through to my inbox, no credentials required. So, how is Google doing this ? It's highly undesirable and very creepy. Does this suggest a bug in Firefox (that its not actually clearing data as it should) ? I'm using version 87.0 on Ubuntu 18.04 LTS.

Thanks,

Zozo

DeconSheridan · 18-04-2021 7:40pm

You are signed in on your device, not just your browser. On your google account Security settings you can see what devices are signed in. Google uses OAuth protocol for any third party "Sign In with Google" API access.

see myaccount.google.com for devices signed in

ZoZoZo · 18-04-2021 9:12pm

> You are signed in on your device, not just your browser
Well this sounds even more disturbing. So you are saying Google has planted something like a cookie somewhere on my hardware that my browser is unaware of and therefore is unable to delete. Where is this information stored and how do I delete it ?

And how does this work exactly if its just identifying the device then does this mean if someone else uses a different account on the same device they can see my inbox ? This seems like a security nightmare.

19-04-2021 11:29am

Just tested this with a fresh Firefox profile (87.0, Windows 10):

Sign in at mail.google.com
Tools => Options => Privacy and Security => Clear Data => Clear
Refresh the mail.google.com tab

Result: need to sign in again. So it looks like a problem specific to your setup OP. Unless you can replicate it in a fresh Firefox profile?

DeconSheridan · 22-04-2021 8:50pm

ZoZoZo wrote: »

> You are signed in on your device, not just your browser
Well this sounds even more disturbing. So you are saying Google has planted something like a cookie somewhere on my hardware that my browser is unaware of and therefore is unable to delete. Where is this information stored and how do I delete it ?

And how does this work exactly if its just identifying the device then does this mean if someone else uses a different account on the same device they can see my inbox ? This seems like a security nightmare.

A lot of apps now use the Google api to facilitate a single sign-on type user experience, there's more to websites than cookies and cache as companies use persistent browser functionality and google services running in the background on most devices to sync or wait then sync when next connected to the internet, always-on type services.

Stay signed in or out of your Google Account

Turn sync on and off

ZoZoZo · 25-04-2021 4:37pm

28064212 wrote: »

Just tested this with a fresh Firefox profile (87.0, Windows 10):
Sign in at mail.google.com

Tools => Options => Privacy and Security => Clear Data => Clear

Refresh the mail.google.com tab

Result: need to sign in again. So it looks like a problem specific to your setup OP. Unless you can replicate it in a fresh Firefox profile?

When I do this on my setup after step 3. I still get straight to my inbox, no sign-in required, although ironically, at the Clear Data step a pop-up warns me 'this may sign me out' of any websites I'm logged into. The fact that they use may is a bit disturbing and indeed the fact that I don't get logged out in the case of gmail.

I have found that if I close Firefox altogether and then relaunch it and go to gmail I am logged out. So this is looking more and more like a bug in Firefox on Linux.

But from DeaconSheridan's link:

If you're using a public computer or someone else's device:

Browse in private.
When you’re done, close all private browsing windows. You'll be automatically signed out.

Note this says close all private browsing windows as opposed to tabs which I guess suggests that what I'm seeing is expected although that wouldn't explain how Google are doing this, as I certainly haven't knowingly installed any Google services that could be running in the background on my system. Moreover it doesn't explain why the same thing doesn't happen on Windows 10.

Zozo

markpb · 25-04-2021 10:01pm

ZoZoZo wrote: »

although ironically, at the Clear Data step a pop-up warns me 'this may sign me out' of any websites I'm logged into. The fact that they use may is a bit disturbing and indeed the fact that I don't get logged out in the case of gmail.

They say may because not all sites use cookies or local storage to persist sessions. Sites can use IDs in the URL or query string, they may use NTML, they could even use IP address if they wanted.

08-09-2021 9:12pm

As they say, a little knowledge is a dangerous thing.

Victor · 08-09-2021 9:18pm

How can one trust website XYW has a bona fide 'Sign in with Google' and it isn't just taking your login credentials?

08-09-2021 9:53pm

https://www.boards.ie/discussion/comment/117865734#Comment_117865734

Because the first step of "Sign in with Google" is to take you to https://accounts.google.com/o/oauth2/v2/auth/... So long as the URL is HTTPS and on the Google domain, XYW can't fake that.

Now, if the site says "put in your google password in this text box =>" and you do, then yes, you're screwed

TitanHQ · 09-09-2021 4:10pm

Session cookies allow the functionality you describe:

Session cookie

A session cookie (also known as an in-memory cookie, transient cookie or non-persistent cookie) exists only in temporary memory while the user navigates a website.[21] Session cookies expire or are deleted when the user closes the web browser.[22] Session cookies are identified by the browser by the absence of an expiration date assigned to them.

Source: HTTP cookie - Wikipedia

Since these do not exist as a file using "Clear Data" will not remove them, you need to close the browser. As well as allowing you to log in automtatically, session cookies are susceptible to hijacking which will give an attacker the same level of access:

Session hijacking attack Software Attack | OWASP Foundation

Capt'n Midnight · 13-09-2021 12:18am

https://coveryourtracks.eff.org/ = Your browser fingerprint appears to be unique among the 218,645 tested in the past 45 days.

They haven't needed cookies for a long time.

Timing, location, and other metrics can also localise you.

How does gmail keep track of my sign-in status ?

Comments

Session cookie

Source: HTTP cookie - Wikipedia