Thursday, April 20, 2023

April patch set for TenFourFox

As promised, there are new changesets to pick up in the TenFourFox tree. (If you're new to rolling your own TenFourFox build, these instructions still generally apply.) I've tried to limit their scope so that people with a partial build can just pull the changes (git pull) and gmake -f build without having to "clobber" the tree (completely erase and start over). You'll have to do that for the new ESR when that comes out in a couple months, but I'll spare you that today. Most of these patches are security-related, including one that prevents naughty cookies which would affect us as well, though the rest are mostly crash-preventers and would require PowerPC-specific attacks to be exploitable. There is also an update to the ATSUI font blacklist. As always, if you find problematic fonts that need to be suppressed, post them to issue 566 or in the comments, but read this first.

However, there is one feature update in this patchset: a CSS grid whitelist. Firefox 45, which is the heavily patched underpinning of TenFourFox FPR, has a partially working implementation of CSS grid as explained in this MDN article. CSS grid layout is a more flexible and more generalized way of putting elements on a page than the earlier tables method. Go ahead and try to read that article with the current build before you pull the changes and you'll notice that the page has weirdly scrunched up elements (before a script runs and blanks the whole page with an error). After you build with the updates, you'll notice that while the page still doesn't lay out perfectly right, you can now actually read things. That's because there's a whitelist entry now in TenFourFox that allows grid automatically on (a new preference defaults to true which is checked for by new code in the CSS parser, and there is also an entry in the problematic scripts filter to block the script that ends up blanking the page when it bugs out). The other issues on that page are unrelated to CSS grid.

This will change things for people who set the global pref layout.css.grid.enabled to true, which we have never shipped in TenFourFox because of (at times significant) bugs in the implementation. This pref is now true, but unless the URL hostname is in the whitelist, CSS grid will still be disabled dynamically and is never enabled for chrome resources. If you set the global pref to false, however, then CSS grid is disabled everywhere. If you were using this for a particular site that lays out better with grid on, post the URL to issue 659 or in the comments and I'll consider adding it to the default set (or add it yourself in about:config).

The next ESR (Firefox 115) comes out end of June-early July, and we'll do the usual root updates then.

Tuesday, April 18, 2023

Power Mac ransomware? Yes, but it's complicated

Wired ran an article today (via Ars Technica) about apparent macOS-compatible builds of LockBit, a prominent encrypting ransomware suite, such as this one for Apple silicon. There have been other experimental ransomware samples that have previously surfaced but this may be the first known example of a prominent operation specifically targeting Macs, and it is almost certainly not the last.

What caught my eye in the article was a report of PowerPC builds. I can't seem to get an alleged sample to analyse (feel free to contact me at ckaiser at floodgap dawt com if you can provide one) but the source for that assertion appears to be this tweet.

Can that file run on a Power Mac? It appears it's indeed a PowerPC binary, but the executable format is ELF and not Mach-O, so the file can only run natively on Linux or another ELF-based operating system, not PowerPC Mac OS X (or, for that matter, Mac OS 9 and earlier). Even if the raw machine code were sprayed into memory for an exploitable Mac application to be tricked into running, ELF implies System V ABI, which is similar but different from the PowerOpen ABI used for PowerPC-compatible versions of Mac OS, and we haven't even started talking about system calls. Rather than a specific build targetting Power Macs, most likely this is evidence that the LockBit builders simply ran every crosscompiler variation they could find on their source code: there are no natively little-endian 32-bit PowerPC CPUs, for example, yet there's a ppcle build visible in the screenshot. Heck, there's even an s390x build. Parents, don't let your mainframes out unsupervised.

This is probably a good time to mention that I've been working on security patches for TenFourFox and a couple minor feature adjustments, so stay tuned. It's been awhile but such are hobbies.