On 20/12/15 10:28, Gordon Messmer wrote:
On 12/19/2015 09:49 AM, Alice Wonder wrote:
With third party repositories the key and configuration file is often distributed separately. That's the potential attack vector for trojan keys.
Examples?
All of the notable repositories that I'm aware of publish an x-release.rpm that installs their key and yum repo file. But if your concern is that users might manually install a repo file and public key, then I don't see how modifying yum would change that. The attacker would probably include a key that contains an address they control and validates properly against it.
In other words, I think the solution to the problem is simply to make sure that the repositories publish their "release" rpm over https and that documentation reflects the secure URL. I notice now that EPEL links directly to the https URL for their release rpm, but their FAQ still provides a command-line example for installation using an http URL.
The FAQ should be updated. That method is a potential security problem because it doesn't use https and doesn't check the package signature. But the solution is simply to replace http with https in the FAQ. yum isn't used to install the release package, and I think the solution is to make sure that malicious release packages don't get installed, not to try to behave well on a system where an attacker already installed malicious data.
Unless I'm mistaken RPM in el5 does not support the https protocol.