Signed binaries [LWN.net]

Signed binaries

Posted Jul 25, 2005 6:17 UTC (Mon) by Ross (subscriber, #4065)
In reply to: OLS: Linux and trusted computing by zblaxell
Parent article: OLS: Linux and trusted computing

I suspect they would load more slowly... at least the first time; everytime
if there is no caching. However the problem with such things is that an
attacker need only find a bug in the kernel or any of the signed binaries
which allows running of unsigned code. Even worse consider that the only
protected "code" in this situation are machine code binaries and libraries.
Any language implemented at a higher level (scripts, macros, etc.) would not
be checked. If you want to be able to run bash you are suddenly trusting
all the scripts written in bash (though the commands they call may not be
allowed unless they are built-ins). 99% of interpreters do not have any way
to even know which actions should be allowed.

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Signed scripts

Posted Jul 26, 2005 1:12 UTC (Tue) by xoddam (subscriber, #2322) [Link]

> Even worse consider that the only protected "code" in this situation are
> machine code binaries and libraries.

Shebang scripts (starting with a line like #!/usr/bin/perl) can have their signatures checked by the kernel's binfmt_script executable loader in exactly the same way as it's done for ELF binaries.

Checking signatures on scripts loaded in other ways (including modules) would need interpreter support. A large job, but not insurmountable.