Security implications of using ControlMaster

Damien Miller
Tue, 21 Jan 2020 01:18:52 -0000

On Mon, 20 Jan 2020, Stephen Harris wrote:

> On Tue, Jan 21, 2020 at 11:08:51AM +1100, Damien Miller wrote:
> > So IMO disallowing session multiplexing is at most a speedbump that an
> > attacker will cross with relative ease. Speedbumps make sense
sometimes,
>
> An attacker getting root on the jumphost gets immediate control of
> any _current_ persistent connections and new connections.  Without
> ControlMaster it's a _lot_ harder to take control of current
connections,
> but pretty easy to subvert new connections.

I wouldn't say it's a lot harder to take control of current connections
-
writing a ptrace-based tool that hijacked a running ssh client and
injected a one-off implant payload via keystrokes doesn't seem like
much work.

-d