Dear Vitaly
On 5/10/22 05:24, Vitaly Krasheninnikov wrote:
Hi Elmar,
Thank you for debcheckroot. I think it is a great project, which makes us one
step closer to a verifiable Debian system.
In this particular case, I'd like to point out the exact flags from fileserror.lis that you showed
us: "..._.GM" and "..._..M".
According to the description on your website, it means the modification of the
file permissions, not the actual content.
...
So while I truly consider the debcheckroot very useful, I think in this case it
was a false positive due to the side effects of the postinst scripts of the
relevant packages.
Thank you,
Vitaly
Thanks for pointing that out! I have not used the tool for long on my
own, so that I forgot about the change indication marker letters. Of
course there isn´t much you can say about the modified group and file
permission of a file. See here what Sylvain Sécherre had written me in
her original email:
On 5/6/22 15:05, Sylvain Sécherre wrote to estel...@elstel.org,
(BCC possible):
> Hello Elmar,
> ...
> Here's the fileserror.lis:
> ..._.GM /usr/bin/crontab cron_3.0pl1-137_amd64 root root 755
> ..._..M /usr/bin/pkexec policykit-1_0.105-31+deb11u1_amd64 root root 755
> ..._.GM /usr/bin/ssh-agent openssh-client_1:8.4p1-5_amd64 root root 755
> ..._..M /usr/libexec/polkit-agent-helper-1
> ...
> The file filesunverified.lis is very long, while pkgcorrupt.lis is empty.
>
> I ran debcheckroot on a possibly infected machine.
>
> Thank you for your help!
>
> Best regards,
>
> Sylvain
If debcheckroot was executed inside the infected root file system,
then no wonder it can´t find anything. The rootkits I know, and I have
discovered and burned several root kits on blue ray, have behaved like
this: Inside the root infected executables compare ok against the
pristine version, but not so outside the rootkit root when you have a
fresh boot. The fact that group and file permissions of these
executables have changed could at least be interpreted as suspicious
though, since normally I´d truly believe there will be nobody who
modifies that.
Regards,
Elmar
