Code signing coming to Firefox Mac builds

A few weeks ago a new Developer Preview of OS X 10.8 was released and it was discovered that as things stand now, Firefox will not run on it. With the current default settings, 10.8 will not allow any software to run unless it's signed with an Apple Developer ID (essentially, a certificate issued by a particular Apple Root CA). We don't know exactly when 10.8 will be released to the public but some have speculated that it could be as early as the week of June 11th at WWDC 2012. We must have a signed and released Firefox out there before the general public starts upgrading and we've been working hard to make that happen as soon as possible. This post will give a short history of Mac signing at Mozilla and talk about our timeline for enabling it.


Code signing of Mac builds has been on our radar for a long time. Bug 400296 was originally filed in 2007. In late 2010 Syed Albiz did a ton of great work figuring out the Apple tools and how we can integrate them into our automation. That work didn't quite get finished before his internship was completed and the bug stagnated for some time afterwards. At the start of this year there was renewed energy when Erick Dransch picked up the bug. We attempted to land his work and enable signing on nightlies in mid-April, but that ended up bouncing due to some conflicts with our upgrade to 10.7-based build machines. Erick's internship expired before everything could be fixed up, and the bug fell to me.

After gaining access to Mozilla's Apple Developer account on Monday there was a lot of early iteration before we got to the point where we could sign a build in a way that Mountain Lion liked. There's multiple certificates types that one can get from Apple ("Development Certificate", "Mac App Certificate", "Developer ID Certificate") and multiple versions of OS X and XCode (each with their own quirks) that one can sign with. Mostly thanks to Steven Michaud's knowledge and assistance we figured out exactly what combination of these we'll need to use to have signed Firefox builds that work everywhere.

Where we're at now

At this point in time we've got all the tools we need to sign all Mac Firefox builds. The only blocking issue at this point is figuring out access restrictions to our Apple Developer Account, so that we can generate our final Developer ID certificates.


Like with Windows Authenticode signing we will have 3 different certificates for different types of Firefox builds. Dep and try builds are at the lowest level of trust and have no regular users and therefore will be signed with a self signed certificate. This means that they will not run on 10.8 unless the user has allowed "applications downloaded from anywhere" to run (which is not the default). Nightly and Aurora are at an elevated level of trust and have a userbase. These will be signed with their own Developer ID certificate. Finally, Beta and Release builds are at the highest level of trust and oversight, and represent the majority of our users. They will be signed with a separate Developer ID certificate. From a user standpoint, Nightly, Aurora, Beta and Release will all look the same but using separate certificates gives us some degree of isolation in terms of certificate revocation.


I intend to have dep and try builds signed by the end of the week. After we figure out the access restrictions to our Developer Account we will turn on signing of Nightly builds, hopefully early/mid next week. After letting those settle for a day or two we will turn on signing of Aurora and Beta builds, hopefully by the end of next week.

If you're interested in the technical details of signing Mac builds Erick wrote an excellent blog post detailing the trials and tribulations of writing tools around them.


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