[tor-bugs] #19508 [Applications/Tor Browser]: Proposal to drop Tor Browser's plugin patches

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#19508: Proposal to drop Tor Browser's plugin patches
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 Reporter:  arthuredelstein           |          Owner:  tbb-team
     Type:  defect                    |         Status:  new
 Priority:  Medium                    |      Milestone:
Component:  Applications/Tor Browser  |        Version:
 Severity:  Normal                    |     Resolution:
 Keywords:  TorBrowserTeam201606      |  Actual Points:
Parent ID:                            |         Points:
 Reviewer:                            |        Sponsor:
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Description changed by arthuredelstein:

Old description:

> Tor Browser has three patches related to blocking plugins:
> * #3547 adds a function that whitelists the flash plugin only and
> excludes loading all other plugins
> * #8312 hides the link to "Manage plugins" when the plugin is disabled
> * #10280 adds a UI for enabling/disabling plugins in the add-ons page
>
> These patches were introduced when Flash was still in fairly wide use.
> But since then, Flash has been disabled by default in Firefox, and is
> replaced on a substantial number of websites by HTML5 video and
> JavaScript. Furthermore, we want to strongly discourage users from using
> Flash as there is a significant risk that it will bypass the proxy or
> expose the user to tracking or security vulnerabilities.
>
> First, from what I can see, when the pref `plugin.disable` is set to true
> (as it is in `browser/app/profile/000-tor-browser.js`), all plugins
> (including Flash) are blocked from ever loading into the Firefox process.
> Therefore the code in our #3547 is never exercised.
>
> Second, #10280 only makes it more likely for the user to set
> "plugin.disable" to false, by exposing that pref in the UI.
>
> Finally, #8312 seems unnecessary because, when "plugin.disable" is true,
> no "Manage plugins" link appears. Instead, the only message is "A plugin
> is needed to display this content." Also, various popular video sites,
> such as YouTube and Vimeo, now use HTML5 video without any complaints
> about missing Flash.
>
> So I would suggest we can drop these three patches. Instead we might
> consider a couple of UI tweaks to improve user safety:
> 1. Hide the Plugins section of about:addons altogether to prevent the
> user from even considering loading any plugins
> 2. Change the plugin failure message to "A plugin would be needed to
> display this content. For security reasons, Tor Browser does not support
> plugins."
>
> I think both of these changes could be implemented as XUL overlays in
> torbutton.
>
> Finally, for extra safety, we could add an extra C++ patch that ensures
> that whenever an nsPluginsDir::LoadPlugin implementation is called, the
> "plugin.disabled" pref is checked and, if it is true, the function loads
> nothing and returns an error code. I think such a patch might be
> upstreamable.

New description:

 Tor Browser has three patches related to blocking plugins:
 * #3547 adds a function that whitelists the flash plugin only and excludes
 loading all other plugins
 * #8312 hides the link to "Manage plugins" when the plugin is disabled
 * #10280 adds a UI for enabling/disabling plugins in the add-ons page

 These patches were introduced when Flash was still in fairly wide use. But
 since then, Flash has been disabled by default in Firefox, and is replaced
 on a substantial number of websites by HTML5 video and JavaScript.
 Furthermore, we want to strongly discourage users from using Flash as
 there is a significant risk that it will bypass the proxy or expose the
 user to tracking or security vulnerabilities.

 First, from what I can see, when the pref `plugin.disable` is set to true
 (as it is in `browser/app/profile/000-tor-browser.js`), all plugins
 (including Flash) are blocked from ever loading into the Firefox process.
 Therefore the code in our #3547 is never exercised.

 Second, #10280 only makes it more likely for the user to set
 "plugin.disable" to false, by exposing that pref in the UI.

 Finally, #8312 seems unnecessary because, when "plugin.disable" is true,
 no "Manage plugins" link appears. Instead, the only message is "A plugin
 is needed to display this content." Also, various popular video sites,
 such as YouTube and Vimeo, now use HTML5 video without any complaints
 about missing Flash.

 So I would suggest we can drop these three patches. Instead we might
 consider a couple of UI tweaks to improve user safety:
 1. Hide the Plugins section of about:addons altogether to prevent the user
 from even considering loading any plugins
 2. Change the plugin failure message to "A plugin would be needed to
 display this content. For security reasons, Tor Browser does not support
 plugins."

 I think both of these changes could be implemented as XUL overlays in
 torbutton.

 Finally, for extra safety, we could add an extra C++ patch that ensures
 that whenever an nsPluginsDir::LoadPlugin implementation is called, the
 `plugin.disable` pref is checked and, if it is true, the function loads
 nothing and returns an error code. I think such a patch might be
 upstreamable.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/19508#comment:1>
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