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Is there sense in set up LSM after the system was installed?
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as.gentoo
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PostPosted: Thu Sep 06, 2018 11:14 am    Post subject: Is there sense in set up LSM after the system was installed? Reply with quote

Greets!

Assuming that the gentoo handbook was followed until after building the kernel and rebooting.

AFAIK most LSM have a learning mode. How can I be sure that there is no backdoor/rootkit/trojan/virus in the system before the LSM was used? These could compromise the system (LSM config files, /etc/…/<scripts>, /{,usr}/{,s}bin, /usr/src/.config, source code). The LSM will not block access because everything before using it is usually considered to be clean, right?

You can probably edit the config files but I guess that's a several thousand - maybe more - entries to check…
I might be better to use a LSM ASAP - as well effort-wise because rule creation would be kind of step-by-step and not a thousand rules for all X and none-X programs, correct? What's speaking against that?

Thanks in advance!


PS: I heard that a system is ~30% slower when a LSM is used. Is that true for system w/ many cores - let's say (real) 8 cores?

EDIT: title changed 2018-09-06
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Maitreya
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PostPosted: Thu Sep 06, 2018 11:35 am    Post subject: Reply with quote

Quote:

...
How can I be sure that there is no backdoor/rootkit/trojan/virus in the system before the LSM was used?
...


You can't. You can however try as much checking sources and control your bootstrap. How far do you want to go?

http://wiki.c2.com/?TheKenThompsonHack


That being said, you need Trust™ somewhere
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Hu
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PostPosted: Fri Sep 07, 2018 1:59 am    Post subject: Reply with quote

LSM collectively refers to a group of defensive technologies. They probably each have a cost, but I doubt it is that high. Some of them are so simple that it would be completely unreasonable for them to be that slow. Could you point us to where you saw that speed claim?
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