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Date: Tue, 16 Aug 2011 07:47:30 -0400
From: Rich Felker <dalias@...ifal.cx>
To: musl@...ts.openwall.com
Subject: Re: LD_PRELOAD and RTLD_NEXT support
On Tue, Aug 16, 2011 at 10:34:10AM +0400, Vasiliy Kulikov wrote:
> Rich,
>
> On Tue, Aug 16, 2011 at 01:17 -0400, Rich Felker wrote:
> > (fully disabled for any suid/sgid binary)
>
> if ((aux[0]&0x7800)!=0x7800 || aux[AT_UID]!=aux[AT_EUID]
> || aux[AT_GID]!=aux[AT_EGID]) {
>
> Two things here:
>
> 1) This check should be extended to support AT_SECURE (dumpable flag,
> any LSM security domains, capabilities).
Indeed, I'll add this. Do I just check for aux[AT_SECURE] != 0?
> 2) As you check for (aux[0] & 0x7800) you assume some of these elements
> can be absent. I feel it's wrong to assume you're not s*id'ed in this
You misread the test. Absence of any of the 4 fields causes the
program to be treated as if it were suid.
> case. Instead, it's better to check for (getuid()!=geteuid() ||
> getgid()!=getegid()).
I don't see how this helps, and this takes us down the glibc path of
abysmal startup times for every tiny program called from ./configure,
which is the reason ./configure takes so damn long...
Rich
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