Comment 0 for bug 1150737

I've encountered at least five different Amazon AMIs which all fail debsums right out of the box. The offending binaries are upstart: /sbin/initctl and dpkg: /sbin/start-stop-daemon. Both are handy locations to drop a rootkit. Most prominently, the banner-choice for the GUI AWS console wizard in us-east-1 is ami-3fec7956, which seems to be created by Canonical (ami-3fec7956 099720109477/ubuntu/images/ebs/ubuntu-precise-12.04-amd64-server-20130124).

us-east-1: ami-3fec7956, ami-de0d9eb7
us-west-1: ami-b81230fd
us-west-2: ami-da1810ae
ap-northeast-1: ami-77cf4976

I analyzed only initctl, as it was the first to trip my alarms. In the following examples, the left side is the one from the upstart package version dpkg claims to have installed, the right is the one actually on the system.

* A side-by-side hex/ascii of the diff : http://pastebin.com/raw.php?i=JGN1rMC5
* The same, with some color: http://cl.ly/image/2x2l3S1j1f38
* A side-by-side comparison of objdump --disassemble-all: http://pastebin.com/raw.php?i=5ppcJG2H
* The same, with some color: http://cl.ly/image/2d0w1I3W083x

The file size is the same, but clearly it is not the one from the package. objdump interpreted this delta as having a mov instruction, then executing a conditional jump. This "looks" scary, but I'm no expert. This may be only a side-effect of trying to disassemble code.

This is either malicious, or a totally benign mistake, but in either case, Canonical should not be distributing AMIs which cannot pass rudimentary integrity checks.

To reproduce, simply start an AWS instance with one of these AMIs, install debsums, and run something like:

for PKG in `dpkg --get-selections | awk '{print $1}'`; do echo ${PKG}: >> failsums; debsums $PKG | grep FAILED >> failsums; done