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OpenType Sanitizer

The OpenType Sanitizer (OTS) parses and serializes OpenType files (OTF, TTF) and WOFF and WOFF2 font files, validating them and sanitizing them as it goes.

The C library is integrated into Chromium and Firefox, and also simple command line tools to check files offline in a Terminal.

The CSS font-face property is great for web typography. Having to use images in order to get the correct typeface is a great sadness; one should be able to use vectors.

However, on many platforms the system-level TrueType font renderers have never been part of the attack surface before, and putting them on the front line is a scary proposition... Especially on platforms like Windows, where it's a closed-source blob running with high privilege.

Building from source

Instructions below are for building standalone OTS utilities, if you want to use OTS as a library then the recommended way is to copy the source code and integrate it into your existing build system. Our build system does not build a shared library intentionally.

General build instructions

Build OTS:

$ meson build
$ ninja -C build

Run the tests (if you wish):

$ ninja -C build test

Developer build instructions

If you would like to see the source code lines related to reported errors, then replace meson call above with:

$ meson -Ddebug=true build

For example:

$ ./ots-sanitize ~/fonts/ofl/merriweathersans/MerriweatherSans-Bold.ttf
ERROR at src/ (ParseScriptTable)
ERROR: Layout: DFLT table doesn't satisfy the spec. for script tag DFLT
ERROR at src/ (ParseScriptListTable)
ERROR: Layout: Failed to parse script table 0
ERROR at src/ (ots_gsub_parse)
ERROR: GSUB: Failed to parse script list table
ERROR at src/ (ProcessGeneric)
Failed to sanitize file!


See docs

Thanks to Alex Russell for the original idea.