Hi Tom!

Removing the cookie lifetime policy feature does not change how we treat 
session cookies. Enabling `network.cookie.lifetimePolicy` simply meant that 
all cookies would be downgraded to session cookies, no matter how they were 
set. However, the feature didn't avoid disk-writes when it came to other 
storages 
<https://searchfox.org/mozilla-central/rev/34289456cccd8bcacd5e8665102cca7543b35213/browser/modules/Sanitizer.jsm#856-862>
.
When the user has clearing on shutdown enabled, now that we've switched 
over to the sanitize-on-shutdown mechanism, cookies are no longer 
downgraded, but stored normally (on disk) and cleared on shutdown (or 
startup if there was a crash).
If you're trying to avoid disk-writes for both cookies & storage I'd 
suggest using private browsing mode (e.g. via `browser.privatebrowsing.
autostart`).

Best Regards,
Paul

On Tuesday, 19 July 2022 at 20:33:03 UTC+2 Tom Ritter wrote:

> The first email referenced in-memory handling of cookies, so (with my Tor 
> hat, not my Mozilla hat) the concern would be that this will cause disk 
> writes.  Tor Browser tries hard to avoid writing anything to disk, 
> especially not information that leaks the browsing history.  If session 
> cookies (or non-session cookies treated as session cookies, or non-session 
> cookies that will be wiped at the end of the session) are being written to 
> disk (either before this change, or after it) it would be something we 
> should make Tor aware of so Tor can determine how to handle the situation.  
> (Which might be backing out the Mozilla patch in Tor Browser, or asking 
> Mozilla very nicely if they would reconsider.)  I'm going to cc the Tor 
> Browser lead in on the email...
>
> -tom
>
> On Tue, Jul 19, 2022 at 12:12 PM Hannah Peuckmann <[email protected]> 
> wrote:
>
>> The original intent to unship might be a bit misleading in regards to 
>> session cookies.
>> We are not going to remove the concept of a session cookie. We are just 
>> not downgrading cookies to session anymore if shutdown cleaning is 
>> activated via “clear cookies and site data when Nightly is closed”. With 
>> network.cookie.lifetimePolicy activated, cookies were downgraded to 
>> session. The sanitizeOnShutdown mechanism does not do this. Network.
>> cookie.lifetimePolicy did not manage session cookies or cleaned up 
>> cookies that reached their expiration date. So, the way session cookies are 
>> handled will not be changed. In general, if we crash and could not clean on 
>> shutdown we have a mechanism to  run the sanitization on startup. I hope 
>> this answers your question.
>>
>>
>> On Monday, July 18, 2022 at 4:42:56 PM UTC+2 Tom Ritter wrote:
>>
>>> I'm sorry I missed this email the first time and am now raising 
>>> questions on it.  How does this relate to disk writes?  Will we now write 
>>> session cookies to disk (and then sanitize them on shutdown?)  What if we 
>>> crash, and don't run the sanitization code, will we detect them and 
>>> sanitize them on startup?
>>>
>>> -tom
>>>
>>> On Mon, Jul 18, 2022 at 4:02 AM Hannah Peuckmann <[email protected]> 
>>> wrote:
>>>
>>>> Update:
>>>>
>>>> We postponed our work to Fx103. We granted our patches an additional 
>>>> cycle in Nighty to be on the safe side in regards to bugs. Hence, Starting 
>>>> from Fx103, activating “Delete cookies and site data when nightly is 
>>>> closed” will trigger the sanitization mechanism, the feature that is 
>>>> behind 
>>>> the “Clear history when Nightly closes” 
>>>> <https://support.mozilla.org/en-US/kb/delete-browsing-search-download-history-firefox#w_how-do-i-make-firefox-clear-my-history-automatically>
>>>>  
>>>> option, to perform the same data cleaning as network.cookie.lifetimePolicy 
>>>> did. Starting from Fx104, network.cookie.lifetimePolicy will be removed 
>>>> from the code base entirely.
>>>>
>>>> On Monday, May 2, 2022 at 11:37:11 AM UTC+2 Hannah Peuckmann wrote:
>>>>
>>>>> With the release of Fx102 we intend to remove 
>>>>> network.cookie.lifetimePolicy on desktop. 
>>>>>
>>>>> Bug to remove: Bug 1681493 - [meta] Deprecate and remove 
>>>>> network.cookie.lifetimePolicy 
>>>>> <https://bugzilla.mozilla.org/show_bug.cgi?id=1681493>
>>>>>
>>>>> For most users, the concept of "session" cookies is very hard to 
>>>>> understand and so we try to make it a little more opaque by calling the 
>>>>> option "Delete cookies and site data when Nightly is closed". Because 
>>>>> this 
>>>>> can already be done with sanitization preferences we effectively end up 
>>>>> with two different ways in Firefox to clear cookies and site data on 
>>>>> exit. 
>>>>> The difference between them is almost impossible to understand for anyone 
>>>>> who is not a Firefox engineer.
>>>>>
>>>>> In addition to usability concerns, having "in-memory-only" session 
>>>>> cookie lifetime has meant adding ugly hacks and workarounds for most of 
>>>>> our 
>>>>> storage technologies for a long time now (or simply disabling them in 
>>>>> that 
>>>>> mode). We had already decided in the past to stop treating "session 
>>>>> lifetime" as equivalent to "in-memory" to avoid these issues. At that 
>>>>> point 
>>>>> there's no real reason to have the concept of session lifetime anymore 
>>>>> when 
>>>>> all of it can be handled through sanitization.
>>>>>
>>>>> We will remove the network.cookie.lifetimePolicy pref that is 
>>>>> controlled by the  "Delete cookies and site data when Nightly is 
>>>>> closed" 
>>>>> <https://support.mozilla.org/en-US/kb/clear-cookies-and-site-data-firefox#w_clear-cookies-for-any-website>
>>>>>  
>>>>> option. Starting from Fx102, activating “Delete cookies and site data 
>>>>> when 
>>>>> nightly is closed” will trigger the sanitization mechanism, the feature 
>>>>> that is behind the “Clear history when Nightly closes” 
>>>>> <https://support.mozilla.org/en-US/kb/delete-browsing-search-download-history-firefox#w_how-do-i-make-firefox-clear-my-history-automatically>
>>>>>  
>>>>> option, to perform the same data cleaning as 
>>>>> network.cookie.lifetimePolicy 
>>>>> did.
>>>>>
>>>>> The UI though will not experience any changes, also, the feature of 
>>>>> being able to declare exceptions to “Delete cookies and site data when 
>>>>> Nightly is closed” through the “Manage exceptions 
>>>>> <https://support.mozilla.org/en-US/kb/clear-cookies-and-site-data-firefox#w_clear-cookies-for-any-website>”
>>>>>  
>>>>> button will still be taken into account when cleaning on shutdown (Bug 
>>>>> 1681701 <https://bugzilla.mozilla.org/show_bug.cgi?id=1681701>).
>>>>>
>>>>> Bug 1681498 <https://bugzilla.mozilla.org/show_bug.cgi?id=1681498> will 
>>>>> take care of migrating all users of the “Delete cookies and site data 
>>>>> when 
>>>>> Nightly is closed" option to matching sanitization prefs. According to 
>>>>> telemetry 
>>>>> data <https://sql.telemetry.mozilla.org/queries/85568/source#211908>those 
>>>>> are around 5.5% of the users on Release and 8%  of the Nightly users. 
>>>>>
>>>>> Removing the network.cookie.lifetimePolicy will lead to a cleaner code 
>>>>> base and a more convenient, more uniform sanitization process.
>>>>>
>>>> -- 
>>>>
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>>>> https://groups.google.com/a/mozilla.org/d/msgid/dev-platform/6089e716-2f2c-42cd-9c9f-cceab03ec7afn%40mozilla.org
>>>>  
>>>> <https://groups.google.com/a/mozilla.org/d/msgid/dev-platform/6089e716-2f2c-42cd-9c9f-cceab03ec7afn%40mozilla.org?utm_medium=email&utm_source=footer>
>>>> .
>>>>
>>>

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