Re: [kernel-hardening] [PATCH v1 1/1] Add Trusted Path Execution as a stackable LSM

[Jann Horn]

On Sat, Jun 3, 2017 at 7:53 AM, Matt Brown <matt@xxxxxxxxx> wrote:
> This patch was modified from Brad Spengler's Trusted Path Execution (TPE)
> feature in Grsecurity and also incorporates logging ideas from
> cormander's tpe-lkm.
>
> Modifications from the Grsecurity implementation of TPE were made to
> turn it into a stackable LSM using the existing LSM hook bprm_set_creds.
> Also, denial messages were improved by including the full path of the
> disallowed program. (This idea was taken from cormander's tpe-lkm)
[...]
> Threat Models:
[...]
> 2. Attacker on system replaces binary used by a privileged user with a
>    malicious one
>
> *  This situation arises when administrator of a system leaves a binary
>    as world writable.
>
> *  TPE is very effective against this threat model

How do you end up with world-writable binaries in $PATH?