I support Mac code signing and notarisation for DTS and, as part of that work, I often need to look inside various Apple-specific archive file formats. This post explains how I do this. It’s mostly for the benefit of Future Quinn™, but I figured other folks would appreciate it as well.
IMPORTANT This post explains low-level techniques for inspecting archives. Do not use them to create archives. Instead, create your archives using the highest-level tool that will get the job done (1).
A flat installer package — appropriate for uploading to the Mac App Store or the notary service — is actually a xar archive. Unpack it using the xar tool. For example:
See the xar man page for more info on that tool.
The resulting Bom file is a ‘bill of materials’. For more on this, see the bom man page for details. Use lsbom to dump this:
The Payload file contains… you guessed it… the installer’s payload. This is a gzipped cpio archive. To unpack it, pipe the file through cpio:
See the cpio man page for more info on that tool.
To extract a xip archive (pronounced, I believe, as chip archive), run the xip tool with the --expand argument:
However, if that doesn’t work you’ll need to dig into the archive. First, undo the outer xar wrapper:
This produces two files, Content and Metadata:
The Metadata file is an XML property list:
The Content file is a yaa archive. Unpack this using the yaa tool:
See the yaa man page for more info on that tool.
Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"
(1) For installer package specifically, productbuild is your friend, but you can also use the lower-level tools like productsign, pkgbuild, and pkgutil.
IMPORTANT This post explains low-level techniques for inspecting archives. Do not use them to create archives. Instead, create your archives using the highest-level tool that will get the job done (1).
Flat Installer Package
A flat installer package — appropriate for uploading to the Mac App Store or the notary service — is actually a xar archive. Unpack it using the xar tool. For example:
Code Block % # List the contents: % % xar -tf InstallTest-1.0d1.pkg com.example.apple-samplecode.InstallTest.pkg com.example.apple-samplecode.InstallTest.pkg/Bom com.example.apple-samplecode.InstallTest.pkg/Payload com.example.apple-samplecode.InstallTest.pkg/PackageInfo Distribution % % # Actually unpack: # % mkdir tmp % cd tmp % xar -xf ../InstallTest-1.0d1.pkg % find . . ./Distribution ./com.example.apple-samplecode.InstallTest.pkg ./com.example.apple-samplecode.InstallTest.pkg/Bom ./com.example.apple-samplecode.InstallTest.pkg/Payload ./com.example.apple-samplecode.InstallTest.pkg/PackageInfo
See the xar man page for more info on that tool.
The resulting Bom file is a ‘bill of materials’. For more on this, see the bom man page for details. Use lsbom to dump this:
Code Block % lsbom ./com.example.apple-samplecode.InstallTest.pkg/Bom . 0 0/0 ./InstallTest.app … ./InstallTest.app/Contents … ./InstallTest.app/Contents/Info.plist … ./InstallTest.app/Contents/MacOS … ./InstallTest.app/Contents/MacOS/InstallTest … …
The Payload file contains… you guessed it… the installer’s payload. This is a gzipped cpio archive. To unpack it, pipe the file through cpio:
Code Block % cpio -i < com.example.apple-samplecode.InstallTest.pkg/Payload 5072 blocks % find InstallTest.app InstallTest.app InstallTest.app/Contents InstallTest.app/Contents/Info.plist InstallTest.app/Contents/MacOS InstallTest.app/Contents/MacOS/InstallTest …
See the cpio man page for more info on that tool.
Xip Archives
To extract a xip archive (pronounced, I believe, as chip archive), run the xip tool with the --expand argument:
Code Block % xip --expand XipTest.xip
However, if that doesn’t work you’ll need to dig into the archive. First, undo the outer xar wrapper:
Code Block % xar -xf XipTest.xip
This produces two files, Content and Metadata:
Code Block % ls -l total 7552 -rw-r--r-- 1 quinn staff 1683391 10 Jun 17:05 Content -rw-r--r-- 1 quinn staff 287 10 Jun 17:08 Metadata -rw-r--r-- 1 quinn staff 1697157 10 Jun 17:05 XipTest.xip
The Metadata file is an XML property list:
Code Block % cat Metadata … <dict> <key>UncompressedSize</key> <integer>2598653</integer> <key>Version</key> <integer>1</integer> </dict> </plist>
The Content file is a yaa archive. Unpack this using the yaa tool:
Code Block % yaa extract -ignore-eperm -i Content -d tmp % find tmp tmp tmp/XipTest tmp/XipTest/XipTest.app tmp/XipTest/XipTest.app/Contents tmp/XipTest/XipTest.app/Contents/Info.plist tmp/XipTest/XipTest.app/Contents/MacOS tmp/XipTest/XipTest.app/Contents/MacOS/QCodeIndex tmp/XipTest/XipTest.app/Contents/MacOS/XipTest …
See the yaa man page for more info on that tool.
Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"
(1) For installer package specifically, productbuild is your friend, but you can also use the lower-level tools like productsign, pkgbuild, and pkgutil.
