1390392 - content sandbox breaks font rendering when running under flatpak [was: Github can't see text]

Status: RESOLVED DUPLICATE of bug 1396733

(Core :: Security: Process Sandboxing, defect)

Description

[Sébastien Blin [:sblin] [:amarok]]

Attachment: 1502761916_2151_14082017_.png

User Agent: Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:54.0) Gecko/20100101 Firefox/54.0
Build ID: 20170725113540

Steps to reproduce:

Go to https://github.com/mozilla

Fedora 26
Latest Nightly from Flatpack

Font: Default, DejaVu Serif


Actual results:

See screenshot.

Can't see the text on the page and can't click on repositories


Expected results:

I should see text and buttons.

Comment 1

[Kohei Yoshino [:kohei]]

Please upgrade your graphics driver: https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration

Comment 2

[Bas Schouten (:bas.schouten)]

(In reply to Kohei Yoshino [:kohei] from comment #1)
> Please upgrade your graphics driver:
> https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-
> acceleration

We don't use acceleration on Linux, so that's unlikely to help..

Nical, ever seen anything like this on Fedora?

Comment 3

[Sébastien Blin [:sblin] [:amarok]]

(In reply to Bas Schouten (:bas.schouten) from comment #2)
> (In reply to Kohei Yoshino [:kohei] from comment #1)
> > Please upgrade your graphics driver:
> > https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-
> > acceleration
> 
> We don't use acceleration on Linux, so that's unlikely to help..
> 
> Nical, ever seen anything like this on Fedora?

Yeap (and my system is pretty up-to-date).

If you want, if I have time this week-end, I can build firefox from sources and investigate the output.

Comment 4

[Sébastien Blin [:sblin] [:amarok]]

Oh.

I just retried. And I removed the font-family attribute (for twitter it's ""Helvetica Neue",Helvetica,Arial,sans-serif" on body and for github "-apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol"". And now, I can see the text.

Comment 5

[Nicolas Silva [:nical]]

The font appears to not be loaded properly. It's not just rendering because the size of some of the boxes that should contain text is changed (like the tags on the github issues) so at the layout stage we already have a problem.

Lee you know more about fonts than I do, does this ring any bell? This appears to be the same as bug 1390390 and bug 1391246.

Comment 6

[Nicolas Silva [:nical]]

Jonathan, maybe probably knows more about the font loading business.

Comment 7

[Jonathan Kew [:jfkthame]]

(In reply to Sébastien Blin [:sblin] [:amarok] from comment #4)
> Oh.
> 
> I just retried. And I removed the font-family attribute (for twitter it's
> ""Helvetica Neue",Helvetica,Arial,sans-serif" on body and for github
> "-apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial,
> sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol"". And
> now, I can see the text.

I notice in both cases there is "Helvetica" in the font-family list. Does just removing that fix things? Or inserting an available font name such as "DejaVu Sans" (presumably) at the *start* of the list, so it will be used in preference to Helvetica?

I'm wondering if you have a Helvetica font, or a substitution set up in fontconfig, that for some reason is failing. What does fontconfig show if you run

  fc-match :family=Helvetica

in a terminal?

Comment 8

[Sébastien Blin [:sblin] [:amarok]]

(In reply to Jonathan Kew (:jfkthame) from comment #7)
> (In reply to Sébastien Blin [:sblin] [:amarok] from comment #4)
> > Oh.
> > 
> > I just retried. And I removed the font-family attribute (for twitter it's
> > ""Helvetica Neue",Helvetica,Arial,sans-serif" on body and for github
> > "-apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial,
> > sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol"". And
> > now, I can see the text.
> 
> I notice in both cases there is "Helvetica" in the font-family list. Does
> just removing that fix things? Or inserting an available font name such as
> "DejaVu Sans" (presumably) at the *start* of the list, so it will be used in
> preference to Helvetica?
> 
> I'm wondering if you have a Helvetica font, or a substitution set up in
> fontconfig, that for some reason is failing. What does fontconfig show if
> you run
> 
>   fc-match :family=Helvetica
> 
> in a terminal?

Yeah, if I enter Deja Vu, it works.

```
fc-match :family=Helvetica
texgyreheros-regular.otf: "TeX Gyre Heros" "Regular"
```

Comment 9

[Jonathan Kew [:jfkthame]]

Interesting.... where is the texgyreheros-regular.otf file installed?

I'm wondering if this might be a sandboxing issue. If you set security.sandbox.content.level to 1 in about:config (default on Nightly is 3, I believe), and restart the browser, does that make any difference?

Comment 10

[Sébastien Blin [:sblin] [:amarok]]

/usr/share/texlive/texmf-dist/fonts/opentype/public/tex-gyre/texgyreheros-regular.otf

And yes it's a sanboxing issue because I test the nightly without flatpak and it works.

Comment 11

[Jonathan Kew [:jfkthame]]

(In reply to Sébastien Blin [:sblin] [:amarok] from comment #10)
> /usr/share/texlive/texmf-dist/fonts/opentype/public/tex-gyre/texgyreheros-
> regular.otf
> 
> And yes it's a sanboxing issue because I test the nightly without flatpak
> and it works.

Aha... I think that means the flatpak sandbox is blocking Firefox from accessing the font file. You should report this to whoever is creating/maintaining the flatpak distribution.

Actually, a quick search turns up https://github.com/xhorak/firefox-devedition-flatpak/issues/36, which sounds very much like your issue.

Comment 12

[Jonathan Kew [:jfkthame]]

The comments there suggest that adding /run/host/fonts/ to security.sandbox.content.read_path_whitelist may be a solution. If this is a widespread issue, perhaps that should be included in the default settings.

Comment 13

[Jonathan Kew [:jfkthame]]

gcp: See comments above, and the linked Github flatpak issue. Should we do anything about this in mozilla, e.g. by adding the required path(s) in SandboxBrokerPolicyFactory.cpp, or should this be left as something for the packager/distro to address via the whitelist pref?

Comment 15

[Grey Nicholson (they/them)]

I can reproduce this bug on Ubuntu 17.04, with Flatpak 0.8.5-1, using org.mozilla.FirefoxNightly from https://firefox-flatpak.mojefedora.cz/; the About box reports its version as "57.0a1 (2017-09-12) (64-bit)".

I added "/run/host/fonts/" to security.sandbox.content.read_path_whitelist in about:config (this value was previously empty) and restarted Firefox, and I no longer see the bug.

Comment 16

[Gian-Carlo Pascutto [:gcp]]

(In reply to Jonathan Kew (:jfkthame) from comment #12)
> The comments there suggest that adding /run/host/fonts/ to
> security.sandbox.content.read_path_whitelist may be a solution. If this is a
> widespread issue, perhaps that should be included in the default settings.

Yes, let's do that. We have the prefs so the distros can customize what they need if they put stuff in "odd" places, but for the initial rollout let's be proactive and cover things that we can.