Port of secure fd handling to LSM

offerat_private

Attached is a quick port of that part of grsecurity (1.6) that deals with
handling fds 0,1,2 securely. (thanks to Matt Block for pointing out the 2.4
port).

Its a proof of concept, its not an example of good coding (there's a huge
memory leak there)

There is also a patch to add a new hook 

    static void dummy_binprm_flush (struct linux_binprm *bprm);

that is called from flush_old_exec().

Here is a test case to prove that the policy is working

int main(int argc, char **argv)
{

        int     fd;

        fd=open("sfd.c.tmp",1);

        write(1,"hello\n",6);

        return 0;

}

    % touch sfd.c.tmp

Compile this and run it using strace,

    % strace ./sfd 1>&-

you'll see the value of fd changes from 1 to 3 when the module is present.

Can we have our fds in now please ? :-)

OffTopic:
    Should we create a new de-facto standard directory for policies to be
located in the kernel tree ? It would make it easier if we all had a single
location for them... 

richard.

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Richard Offer                     Technical Lead, Trust Technology, SGI
"Specialization is for insects"
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