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We were seeing some strange behavior with Mac client machines on the network lately, specifically with DNS queries (I’d guess that a lot of it has to do with Bonjour), but the discussion touched on the DNS Changer trojan for Mac. I’d really never heard about it before, and after some basic reading, it really got me thinking about the state of software packaging, updates, and distribution. Granted, some of my observations would require sweeping changes to how packaging is handled (even on the *nixes), and would require buy-in from more than just the vendor and distributor (well, I guess MS can probably pressure ISVs to do whatever they want), but seems to be the only way to keep appliancization from becoming the solution to security issues. I’ve written about this before, and a while ago in respect to Linux, but here’s my current take on what needs to be done to software packaging to allow our machines to stay secure, no matter what OS they run.

  1. Allow packages to be installed as a user. This is a mammoth task under Windows or Mac, but still an issue under Linux. The DNS Changer trojan is a case in point - there’s no reason a “video codec” would need to be installed system-wide, and if that were simply installed user-specific, the malicious installer would never have the privileges to change system-wide DNS settings. This is also a big issue under Linux. Yum, apt, rpm, etc. should (if run as a non-root user) install packages in a user-local path under /home by default. Of course, this would mean many things would need to change in order to cope - perhaps even a change to the LSB spec.
  2. Warn about inconsistencies on package installation. The package installation program should warn a user (whether installing packages system-wide or local to a user) if the package is going to modify system-wide files, i.e. files not specifically placed by that package and that package only.
  3. Real package management for Windows and Mac It’s about time that Apple and Microsoft admit that people without billions in funding can come up with good ideas. Get rid of these Installer programs (the many many different ones). Each OS should pick a package format, develop a yum-like (or, even better, zypper-like) package management program that understands repositories. I don’t know how they’d cope with the pervasive license keys and DRM in the non-nix world, but I’m sure they could figure out a way that still allowed sane package management. The idea here is that vendors run repositories and are responsible for their GPG keys, so trojans claiming to be an update to a given vendor’s software would be rejected. Also, isn’t it about time that you can update all your software on Windows or Mac through one tool?
  4. Filesystem-based IDS for Windows and Mac Assuming it will take a while to get everyone onboard with the packaging idea, and noting that users of these OSes like installing applications from arbitrary sources, there should be an OS-level feature to audit all filesystem changes made by untrusted/unsigned applications, and a way to alert the user to these changes if they appear suspisious (essentially what Spybot Search & Destroy / TeaTimer do, but builtin to the OS).
  5. Vendor support of packaging/repositories - Along with the idea of repositories, vendors should have a trust or signing system for ISVs signing keys. If users are installing arbitrary software, making them trust an arbitrary key won’t do anything to improve security. Microsoft and Apple need to run a CA that signs the package signing keys of their ISVs. The also - and here’s the big one - need to have a parallel framework for “independent developers”. I.e. something that doesn’t cost any money for the packagers, and allows them to at least give a “this person is who they say they are” message.
  6. Finally, Make package management pervasive - Have a real push to apply the packaging and signing keys standard to all software for the OS.

On a final note, applicable to both the current state of Linux packaging and my ideas about Mac and Windows… DNS is the ideal method of key distribution (granted, yes, this just means that the security of the packager’s DNS records, and their servers and signing key, is just more of an issue). But even with Yum and Zypper, it seems to me to be logical that the packager’s public key should be stored in a DNS record (or at a URL stored in a DNS TXT record). That way, it wouldn’t be up to an end user to import and trust a key, they’d just have to trust the repository (i.e. software.adobe.com) and the package manager would pull down the key and verify that package X in software.adobe.com is, in fact, signed by the software.adobe.com key.


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