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Design

This document contains a high-level technical description of ungoogled-chromium and its components.

Overview

ungoogled-chromium consists of the following major components:

The following sections describe each component.

Configuration

Configuration is a broad term that refers to patches, build flags, and metadata about Chromium source code. It consists of the following components:

The following sections describe each component in more depth.

Configuration Files

Configuration files (or config files) are files that store build configuration and source code changes for a build.

IMPORTANT: For consistency, all config files must be encoded in UTF-8.

List of configuration files:

  • chromium_version.txt - The Chromium version used by ungoogled-chromium
  • revision.txt - The revision of the changes on top of the given Chromium version.
  • pruning.list - See the Source File Processors section
  • domain_regex.list - See the Source File Processors section
  • domain_substitution.list - See the Source File Processors section
  • downloads.ini - Archives to download and unpack into the buildspace tree. This includes code not bundled in the Chromium source code archive that is specific to a non-Linux platform. On platforms such as macOS, this also includes a pre-built LLVM toolchain for convenience (which can be removed and built from source if desired).
  • flags.gn - GN arguments to set before building.

Source File Processors

Source file processors are utilities that directly manipulate the Chromium source tree before building. Currently, there are two such utilities: binary pruning, and domain substitution.

Binary Pruning: Strips binaries from the source code. This includes pre-built executables, shared libraries, and other forms of machine code. Most are substituted with system or user-provided equivalents, or are built from source; those binaries that cannot be removed do not contain machine code.

The list of files to remove are determined by the config file pruning.list. This config file is generated by devutils/update_lists.py.

Domain Substitution: Replaces Google and several other web domain names in the Chromium source code with non-existent alternatives ending in qjz9zk. These changes are mainly used as a backup measure to detect potentially unpatched requests to Google. Note that domain substitution is a crude process, and may not be easily undone.

With a few patches from ungoogled-chromium, any requests with these domain names sent via net::URLRequest in the Chromium code are blocked and notify the user via a info bar.

Similar to binary pruning, the list of files to modify are listed in domain_substitution.list; it is also updated with devutils/update_lists.py.

The regular expressions to use are listed in domain_regex.list; the search and replacement expressions are delimited with a pound (#) symbol. The restrictions for the entries are as follows:

  • All replacement expressions must end in the TLD qjz9zk.
  • The search and replacement expressions must have a one-to-one correspondence: no two search expressions can match the same string, and no two replacement expressions can result in the same string.

Patches

All of ungoogled-chromium's patches for the Chromium source code are located in patches/. This directory conforms to the default GNU Quilt format. That is:

  • All patches must reside inside patches/
  • There is a patches/series text file that defines the order to apply all the patches. These patches are listed as a relative path from the patches directory.
    • Lines starting with the pound symbol (#) are ignored
    • For lines with patch paths: If there is a space followed by a pound symbol, the text after the patch path will be ignored.

All patch files in ungoogled-chromium must satisfy these formatting requirements:

  • Patch filenames must end with the extension .patch
  • The content must be in unified format.
  • All paths in the hunk headers must begin after the first slash (which corresponds to the argument -p1 for GNU patch).
  • All patches must apply cleanly (i.e. no fuzz).
  • It is recommended that hunk paths have the a/ and b/ prefixes, and a context of 3 (like the git default).
  • All patches must be encoded in UTF-8 (i.e. same encoding as config files).

Patches are categorized into two directories directly under patches/:

  1. core: Changes regarding background requests, code specific to Google web services, or code using pre-made binaries. They must be kept up-to-date with all of the changes in Chromium.
  2. extra: Changes to features regarding control and transparency. They are not guaranteed to persist across updates to Chromium.

Within each category, patches are grouped by the following:

  • debian/ - Patches from Debian's Chromium
    • Patches are not modified unless they conflict with Inox's patches
    • These patches are not Debian-specific. For those, see the debian/patches directory
  • inox-patchset/ - Contains a modified subset of patches from Inox patchset.
  • bromite/ - Patches from Bromite
  • iridium-browser/ - Contains a modified subset of patches from Iridium Browser.
    • Some patches such as those that change branding or URLs to point to Iridium's own servers are omitted
    • Patches are not modified unless they conflict with Debian's or Inox's patches
    • Patches are from the patchview branch of Iridium's Git repository. Git webview of the patchview branch
  • opensuse/ - Patches from openSUSE's Chromium
  • ubuntu/ - Patches from Ubuntu's Chromium
  • ungoogled-chromium/ - Patches by ungoogled-chromium developers

Packaging

Packaging is the process of downloading, building, and producing a distributable package of ungoogled-chromium.

Packaging files use the code from this repository to build ungoogled-chromium. Each platform and configuration has an associated packaging repository under the ungoogled-software organization. For more information about each packaging repository, see the building documentation.

Packaging generally consists of the major steps:

  1. Download and unpack the source tree
  2. Prune binaries
  3. Apply patches
  4. Substitute domains
  5. Build GN via tools/gn/bootstrap/bootstrap.py
  6. Run gn gen with the GN flags
  7. Build Chromium via ninja
  8. Create package(s) of build output (usually in out/Default)