|
|
|
|
Deterministic OSX Dmg Notes.
|
|
|
|
|
|
|
|
|
|
Working OSX DMGs are created in Linux by combining a recent clang,
|
|
|
|
|
the Apple's binutils (ld, ar, etc), and DMG authoring tools.
|
|
|
|
|
|
|
|
|
|
Apple uses clang extensively for development and has upstreamed the necessary
|
|
|
|
|
functionality so that a vanilla clang can take advantage. It supports the use
|
|
|
|
|
of -F, -target, -mmacosx-version-min, and --sysroot, which are all necessary
|
|
|
|
|
when building for OSX. A pre-compiled version of 3.2 is used because it was not
|
|
|
|
|
available in the Precise repositories at the time this work was started. In the
|
|
|
|
|
future, it can be switched to use system packages instead.
|
|
|
|
|
|
|
|
|
|
Apple's version of binutils (called cctools) contains lots of functionality
|
|
|
|
|
missing in the FSF's binutils. In addition to extra linker options for
|
|
|
|
|
frameworks and sysroots, several other tools are needed as well such as
|
|
|
|
|
install_name_tool, lipo, and nmedit. These do not build under linux, so they
|
|
|
|
|
have been patched to do so. The work here was used as a starting point:
|
|
|
|
|
https://github.com/mingwandroid/toolchain4
|
|
|
|
|
|
|
|
|
|
In order to build a working toolchain, the following source packages are needed
|
|
|
|
|
from Apple: cctools, dyld, and ld64.
|
|
|
|
|
|
|
|
|
|
These tools inject timestamps by default, which produce non-deterministic
|
|
|
|
|
binaries. The ZERO_AR_DATE environment variable is used to disable that.
|
|
|
|
|
|
|
|
|
|
This version of cctools has been patched to use the current version of clang's
|
|
|
|
|
headers and and its libLTO.so rather than those from llvmgcc, as it was
|
|
|
|
|
originally done in toolchain4.
|
|
|
|
|
|
|
|
|
|
To complicate things further, all builds must target an Apple SDK. These SDKs
|
|
|
|
|
are free to download, but not redistributable.
|
|
|
|
|
To obtain it, register for a developer account, then download the XCode 6.1.1 dmg:
|
|
|
|
|
https://developer.apple.com/downloads/download.action?path=Developer_Tools/xcode_6.1.1/xcode_6.1.1.dmg
|
|
|
|
|
|
|
|
|
|
This file is several gigabytes in size, but only a single directory inside is
|
|
|
|
|
needed: Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk
|
|
|
|
|
|
|
|
|
|
Unfortunately, the usual linux tools (7zip, hpmount, loopback mount) are incapable of opening this file.
|
|
|
|
|
To create a tarball suitable for gitian input, mount the dmg in OSX, then create it with:
|
|
|
|
|
$ tar -C /Volumes/Xcode/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/ -czf MacOSX10.9.sdk.tar.gz MacOSX10.9.sdk
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
The gitian descriptors build 2 sets of files: Linux tools, then Apple binaries
|
|
|
|
|
which are created using these tools. The build process has been designed to
|
|
|
|
|
avoid including the SDK's files in Gitian's outputs. All interim tarballs are
|
|
|
|
|
fully deterministic and may be freely redistributed.
|
|
|
|
|
|
|
|
|
|
genisoimage is used to create the initial DMG. It is not deterministic as-is,
|
|
|
|
|
so it has been patched. A system genisoimage will work fine, but it will not
|
|
|
|
|
be deterministic because the file-order will change between invocations.
|
|
|
|
|
The patch can be seen here:
|
|
|
|
|
https://raw.githubusercontent.com/theuni/osx-cross-depends/master/patches/cdrtools/genisoimage.diff
|
|
|
|
|
No effort was made to fix this cleanly, so it likely leaks memory badly. But
|
|
|
|
|
it's only used for a single invocation, so that's no real concern.
|
|
|
|
|
|
|
|
|
|
genisoimage cannot compress DMGs, so afterwards, the 'dmg' tool from the
|
|
|
|
|
libdmg-hfsplus project is used to compress it. There are several bugs in this
|
|
|
|
|
tool and its maintainer has seemingly abandoned the project. It has been forked
|
|
|
|
|
and is available (with fixes) here: https://github.com/theuni/libdmg-hfsplus .
|
|
|
|
|
|
|
|
|
|
The 'dmg' tool has the ability to create DMGs from scratch as well, but this
|
|
|
|
|
functionality is broken. Only the compression feature is currently used.
|
|
|
|
|
Ideally, the creation could be fixed and genisoimage would no longer be necessary.
|
|
|
|
|
|
|
|
|
|
Background images and other features can be added to DMG files by inserting a
|
|
|
|
|
.DS_Store before creation. The easiest way to create this file is to build a
|
|
|
|
|
DMG without one, move it to a device running OSX, customize the layout, then
|
|
|
|
|
grab the .DS_Store file for later use. That is the approach taken here.
|
|
|
|
|
|
|
|
|
|
As of OSX Mavericks (10.9), using an Apple-blessed key to sign binaries is a
|
|
|
|
|
requirement in order to satisfy the new Gatekeeper requirements. Because this
|
|
|
|
|
private key cannot be shared, we'll have to be a bit creative in order for the
|
|
|
|
|
build process to remain somewhat deterministic. Here's how it works:
|
|
|
|
|
|
|
|
|
|
- Builders use gitian to create an unsigned release. This outputs an unsigned
|
|
|
|
|
dmg which users may choose to bless and run. It also outputs an unsigned app
|
|
|
|
|
structure in the form of a tarball, which also contains all of the tools
|
|
|
|
|
that have been previously (deterministically) built in order to create a
|
|
|
|
|
final dmg.
|
|
|
|
|
- The Apple keyholder uses this unsigned app to create a detached signature,
|
|
|
|
|
using the script that is also included there.
|
|
|
|
|
- Builders feed the unsigned app + detached signature back into gitian. It
|
|
|
|
|
uses the pre-built tools to recombine the pieces into a deterministic dmg.
|
