Re: [PATCH] ELF: implement AT_RANDOM for future glibc use

[Kees Cook <kees dot cook at canonical dot com>]

On Mon, Oct 06, 2008 at 05:57:48PM -0700, Ulrich Drepper wrote:
> Kees Cook wrote:
> > It sounds like it's not very safe,
> 
> Then investigate it.

As was suspected, each int is the same.

> > but on the other hand, glibc doesn't really care?
> 
> Of course we care.  Especially for SUID and uid==0 binaries.

I meant based on what was said about "if it's as strong as the ASLR
randomness, it's good enough for this".  While the ultimate solution
would be to bolt a better PRNG into the kernel, is the following good
enough for now for glibc:

$ ./rands
0x2b 0x06 0xb7 0x53 0x2b 0x06 0xb7 0x53 0x2b 0x06 0xb7 0x53 0x2b 0x06 0xb7 0x53
$ ./rands
0xc2 0xb5 0x42 0xdc 0xc2 0xb5 0x42 0xdc 0xc2 0xb5 0x42 0xdc 0xc2 0xb5 0x42 0xdc
$ ./rands
0x5f 0x39 0xc6 0xc0 0x5f 0x39 0xc6 0xc0 0x5f 0x39 0xc6 0xc0 0x5f 0x39 0xc6 0xc0
$ ./rands
0xfb 0x4a 0x82 0xbd 0xfb 0x4a 0x82 0xbd 0xfb 0x4a 0x82 0xbd 0xfb 0x4a 0x82 0xbd

-Kees

-- 
Kees Cook
Ubuntu Security Team