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Fontconfig warning: remove 'blank' configuration

    • Closed Issue created by cypherpunks @cypherpunks

    In the log:

    Fontconfig warning: line 145: blank doesn't take any effect anymore. please remove it from your fonts.conf

    Quickly skimming fontconfig's changelog one finds:

    commit 46b2c62faa64250eec3981ee816e91a9a3dee857 Author: Akira TAGOH akira@tagoh.org Date: Wed Jun 17 16:29:08 2015 +0900

    Add a warning for blank in fonts.conf

and remove the unnecessary code for parsing blanks

    src/fcxml.c | 7 +++++++ 1 file changed, 7 insertions(+)

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    • Activity

    • morgan moved from tor-browser#22787 (moved)

      moved from tor-browser#22787 (moved)

    • cypherpunks added component::applications/tor browser in Legacy / Trac owner::tbb-team in Legacy / Trac parent::18097 in Legacy / Trac priority::medium in Legacy / Trac severity::normal in Legacy / Trac status::new in Legacy / Trac tbb-fingerprinting-fonts in Legacy / Trac type::defect in Legacy / Trac labels

      added component::applications/tor browser in Legacy / Trac owner::tbb-team in Legacy / Trac parent::18097 in Legacy / Trac priority::medium in Legacy / Trac severity::normal in Legacy / Trac status::new in Legacy / Trac tbb-fingerprinting-fonts in Legacy / Trac type::defect in Legacy / Trac labels

    • Georg Koppen
      Georg Koppen @gk ·
      Developer

      I guess we can't remove that part of fonts.conf, though, until all distros we support have updated to a more recent fontconfig?

      Trac:
      Cc: N/A to dcf

      • D
        David Fifield @dcf ·
        Contributor

        Here is the upstream commit (2015-06-17): https://cgit.freedesktop.org/fontconfig/commit/?id=46b2c62faa64250eec3981ee816e91a9a3dee857

        But before that (2015-02-17), they had removed <blank></blank> from the default fonts.conf and made the blanks be hardcoded in the library: https://cgit.freedesktop.org/fontconfig/commit/?id=d6a5cc665a1d7e91332944353e92c83ad114368c https://bugs.freedesktop.org/show_bug.cgi?id=79956

        I am sure that when I set up fonts.conf for Tor Browser initially, I cargo-culted most of the config from somewhere, including the <blank> section. I don't really know what it does.

        According to fonts.dtd, the <blank> section is optional, so I would guess that we can remove it without causing crashes on old versions of fontconfig.

        But we may have to deal with this as a new fingerprinting vector (whether we remove the <blank> or not). If we are using the system fontconfig, and the system fontconfig has a built-in set of blanks that varies across systems (it looks like they update it with new Unicode versions), and it's possible for a web page to detect the difference, then it could be used for fingerprinting.

        The set of built-in blanks isn't even under version control, because they have a makefile that fetches a list from unicode.org at build time :( So it's likely to be whatever randomly happened to be there when someone built a release.

        To test, we could repurpose the fontfp code and replace the list of code points with the unicode.org list. !https://repo.eecs.berkeley.edu/git-anon/users/fifield/fontfp.git

        Trac:
        Keywords: N/A deleted, tbb-fingerprinting added

      • morgan
        morgan @morgan ·
        Owner

        @pierov another reason perhaps to build/bundle our own font config

      • ruihildt
        ruihildt @ruihildt ·

        Our support team encountered that issue while testing.

        Is it of any consequence?

      • Pier Angelo Vendrame
        Pier Angelo Vendrame @pierov ·
        Maintainer

        Is it of any consequence?

        I think there isn't any consequence for those who have a "recent enough" version of fontconfig.

        https://cgit.freedesktop.org/fontconfig/commit/?id=d6a5cc665a1d7e91332944353e92c83ad114368c

        This commit was included in Fontconfig 2.11.93, released at the beginning of March 2015.

        Probably all the distributions we want to support have a more recent version (the very old version of Debian we use to build with high compatibility was released in 2017...).

        If we wanted to be extra careful, we could measure the blanks from the list in our fontconfig.conf, with and without the section in the file (they should match).

      • Pier Angelo Vendrame
        Pier Angelo Vendrame @pierov ·
        Maintainer

        If we wanted to be extra careful, we could measure the blanks from the list in our fontconfig.conf, with and without the section in the file (they should match).

        I wrote a very quick test: test.html.

        Be careful, that you might need to run it twice, because Firefox looks up for characters in an async way, and some might be rendered as a tofu initially.

        So, removing the blanks doesn't seem to change anything (at least after refreshing), but I didn't take into account this part:

        According to fonts.dtd, the <blank> section is optional, so I would guess that we can remove it without causing crashes on old versions of fontconfig.

        But we may have to deal with this as a new fingerprinting vector (whether we remove the <blank> or not). If we are using the system fontconfig, and the system fontconfig has a built-in set of blanks that varies across systems (it looks like they update it with new Unicode versions), and it's possible for a web page to detect the difference, then it could be used for fingerprinting.

        The set of built-in blanks isn't even under version control, because they have a makefile that fetches a list from unicode.org at build time :( So it's likely to be whatever randomly happened to be there when someone built a release.

        So, I dug up another bit, and found 8f4c4d278d013f6cc69ba7d7bf0f8aed11398dfb.

        FontConfig completely removed this feature in 2017. That could also explain why I am measuring different sizes and seeing some tofus (I expected to see everything with the same size as a space).

        So, I think that for this issue we can indeed drop our blank configuration (2017 is more recent than 2015, but I think we can still do it).

        As for providing FontConfig on our own, it would have some advantages, but we'd also like not being dependent on it (tor-browser#41799 (closed)), and have the first line of defense inside the browser.

        Anyway, I think we could open a new issue for that.

      • Please register or sign in to reply
    • Georg Koppen
      Georg Koppen @gk ·
      Developer

      Interesting. Seems to be worth investigating further.

      Trac:
      Keywords: tbb-fingerprinting deleted, tbb-fingerprinting-fonts added
      Severity: Minor to Normal

    • Georg Koppen
      Georg Koppen @gk ·
      Developer

      Trac:
      Parent: N/A to legacy/trac#18097 (moved)

    • Georg Koppen
      Georg Koppen @gk ·
      Developer

      Nowadays we have systems where we get line 85: unknown element "blank" messages. Resolved legacy/trac#28198 (moved) as a duplicate.

      Trac:
      Cc: dcf to dcf, traumschule

    • Georg Koppen mentioned in issue legacy/trac#28198 (moved)

      mentioned in issue legacy/trac#28198 (moved)

    • Trac moved from legacy/trac#22787 (moved)

      moved from legacy/trac#22787 (moved)

    • Trac added Bug label and removed 1 deleted label

      added Bug label and removed 1 deleted label

    • Trac added Fingerprinting label and removed 1 deleted label

      added Fingerprinting label and removed 1 deleted label

    • S
      shanzhanz @shanzhanz ·

      Too many warning messages in journalctl due to the same issue, This is an e.g:

      + echo 'May 30 12:19:37 host qubes.StartApp+janondisttorbrowser-dom0[5637]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 12:19:38 host qubes.StartApp+janondisttorbrowser-dom0[5637]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 12:19:38 host qubes.StartApp+janondisttorbrowser-dom0[5637]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 12:19:39 host qubes.StartApp+janondisttorbrowser-dom0[5637]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 12:19:39 host qubes.StartApp+janondisttorbrowser-dom0[5637]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 12:19:39 host qubes.StartApp+janondisttorbrowser-dom0[5637]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 12:19:57 host qubes.StartApp+janondisttorbrowser-dom0[5637]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 12:25:35 host qubes.StartApp+janondisttorbrowser-dom0[5637]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 20:08:30 host qubes.StartApp+janondisttorbrowser-dom0[5637]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 20:08:30 host qubes.StartApp+janondisttorbrowser-dom0[5637]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 20:09:30 host qubes.StartApp+janondisttorbrowser-dom0[7098]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 20:09:30 host qubes.StartApp+janondisttorbrowser-dom0[7098]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 20:09:30 host qubes.StartApp+janondisttorbrowser-dom0[7098]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 20:09:31 host qubes.StartApp+janondisttorbrowser-dom0[7098]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 20:09:32 host qubes.StartApp+janondisttorbrowser-dom0[7098]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 20:09:32 host qubes.StartApp+janondisttorbrowser-dom0[7098]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 20:09:36 host qubes.StartApp+janondisttorbrowser-dom0[7098]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 20:11:32 host qubes.StartApp+janondisttorbrowser-dom0[7098]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 20:11:36 host qubes.StartApp+janondisttorbrowser-dom0[7098]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 20:14:14 host qubes.StartApp+janondisttorbrowser-dom0[7098]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 20:14:18 host qubes.StartApp+janondisttorbrowser-dom0[7098]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 20:14:20 host qubes.StartApp+janondisttorbrowser-dom0[7098]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 20:14:26 host qubes.StartApp+janondisttorbrowser-dom0[7098]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 20:15:47 host qubes.StartApp+janondisttorbrowser-dom0[7098]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 20:47:48 host qubes.StartApp+janondisttorbrowser-dom0[8073]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 20:47:48 host qubes.StartApp+janondisttorbrowser-dom0[8073]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 20:47:49 host qubes.StartApp+janondisttorbrowser-dom0[8073]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 20:47:50 host qubes.StartApp+janondisttorbrowser-dom0[8073]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 20:47:50 host qubes.StartApp+janondisttorbrowser-dom0[8073]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 20:47:50 host qubes.StartApp+janondisttorbrowser-dom0[8073]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 20:47:52 host qubes.StartApp+janondisttorbrowser-dom0[8073]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 20:49:00 host qubes.StartApp+janondisttorbrowser-dom0[8073]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
+ IFS=
+ read -r line
+ echo 'May 30 20:49:27 host qubes.StartApp+janondisttorbrowser-dom0[8073]: Fontconfig warning: "/home/user/.tb/tor-browser/Browser/TorBrowser/Data/fontconfig/fonts.conf", line 85: unknown element "blank"<br />'
+ tee -a /tmp/tmp.Z9hSQqbni1/journalctl_warn.txt_br
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