1634834 - Webfont with 13-character ligature rejected by sanitizer

Status: RESOLVED FIXED

(Core :: Layout: Text and Fonts, defect, P3)

Description

[Anders Kaseorg]

https://andersk.github.io/woff-ligature-test/ (source code) has a webfont with a 13-character ligature. One might assume that a real font would never have a 13-character ligature, but in fact it’s easy to create such a font by accident using webfonts-loader, which automatically generates ligatures from the names of the input SVG files. This showed up in zulip/zulip#14434.

Firefox nightly fails to load the webfont unless gfx.downloadable_fonts.otl_validation is configured to false. It gives these errors in the console:

downloadable font: GSUB: Bad component count of 13 (font-family: "iconfont" style:normal weight:400 stretch:100 src index:0) source: https://andersk.github.io/woff-ligature-test/built/iconfont.woff2
downloadable font: GSUB: Failed to parse ligature 0 (font-family: "iconfont" style:normal weight:400 stretch:100 src index:0) source: https://andersk.github.io/woff-ligature-test/built/iconfont.woff2
downloadable font: GSUB: Failed to parse ligature set 0 (font-family: "iconfont" style:normal weight:400 stretch:100 src index:0) source: https://andersk.github.io/woff-ligature-test/built/iconfont.woff2
downloadable font: Layout: Failed to parse lookup subtable 3 (font-family: "iconfont" style:normal weight:400 stretch:100 src index:0) source: https://andersk.github.io/woff-ligature-test/built/iconfont.woff2
downloadable font: Layout: Failed to parse subtable 0 (font-family: "iconfont" style:normal weight:400 stretch:100 src index:0) source: https://andersk.github.io/woff-ligature-test/built/iconfont.woff2
downloadable font: Layout: Failed to parse lookup 0 (font-family: "iconfont" style:normal weight:400 stretch:100 src index:0) source: https://andersk.github.io/woff-ligature-test/built/iconfont.woff2
downloadable font: GSUB: Failed to parse lookup list table (font-family: "iconfont" style:normal weight:400 stretch:100 src index:0) source: https://andersk.github.io/woff-ligature-test/built/iconfont.woff2
downloadable font: GSUB: Failed to parse table (font-family: "iconfont" style:normal weight:400 stretch:100 src index:0) source: https://andersk.github.io/woff-ligature-test/built/iconfont.woff2
downloadable font: rejected by sanitizer (font-family: "iconfont" style:normal weight:400 stretch:100 src index:0) source: https://andersk.github.io/woff-ligature-test/built/iconfont.woff2
downloadable font: GSUB: Bad component count of 13 (font-family: "iconfont" style:normal weight:400 stretch:100 src index:1) source: https://andersk.github.io/woff-ligature-test/built/iconfont.woff
downloadable font: GSUB: Failed to parse ligature 0 (font-family: "iconfont" style:normal weight:400 stretch:100 src index:1) source: https://andersk.github.io/woff-ligature-test/built/iconfont.woff
downloadable font: GSUB: Failed to parse ligature set 0 (font-family: "iconfont" style:normal weight:400 stretch:100 src index:1) source: https://andersk.github.io/woff-ligature-test/built/iconfont.woff
downloadable font: Layout: Failed to parse lookup subtable 3 (font-family: "iconfont" style:normal weight:400 stretch:100 src index:1) source: https://andersk.github.io/woff-ligature-test/built/iconfont.woff
downloadable font: Layout: Failed to parse subtable 0 (font-family: "iconfont" style:normal weight:400 stretch:100 src index:1) source: https://andersk.github.io/woff-ligature-test/built/iconfont.woff
downloadable font: Layout: Failed to parse lookup 0 (font-family: "iconfont" style:normal weight:400 stretch:100 src index:1) source: https://andersk.github.io/woff-ligature-test/built/iconfont.woff
downloadable font: GSUB: Failed to parse lookup list table (font-family: "iconfont" style:normal weight:400 stretch:100 src index:1) source: https://andersk.github.io/woff-ligature-test/built/iconfont.woff
downloadable font: GSUB: Failed to parse table (font-family: "iconfont" style:normal weight:400 stretch:100 src index:1) source: https://andersk.github.io/woff-ligature-test/built/iconfont.woff
downloadable font: rejected by sanitizer (font-family: "iconfont" style:normal weight:400 stretch:100 src index:1) source: https://andersk.github.io/woff-ligature-test/built/iconfont.woff

Comment 1

[Jonathan Kew [:jfkthame]]

Yeah, looks like this is simply an error in the OTS sanitizer for GSUB tables; I'll post a patch there to fix it. Thanks for reporting!

Comment 2

[Jonathan Kew [:jfkthame]]

Upstream pull request filed: https://github.com/khaledhosny/ots/pull/206.

Comment 3

[Jonathan Kew [:jfkthame]]

Attachment: Bug 1634834 - Update OTS to upstream commit bbd729f8f39c28db9818371b20f9e5ed44226c2f to fix invalid ligature component count check. r=lsalzman

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/95797bc3e1b9
Update OTS to upstream commit bbd729f8f39c28db9818371b20f9e5ed44226c2f to fix invalid ligature component count check. r=lsalzman

Comment 5

[Daniel Varga [:dvarga]]

https://hg.mozilla.org/mozilla-central/rev/95797bc3e1b9