Upcoming FreeBSD Security Advisory

[Ivan Voras]

Borja Marcos wrote:
> On Dec 1, 2009, at 2:20 AM, FreeBSD Security Officer wrote:
> 
>> A short time ago a "local root" exploit was posted to the full-disclosure
>> mailing list; as the name suggests, this allows a local user to execute
>> arbitrary code as root.
> 
> Dr. Strangelove, or How I learned to love the MAC subsystem.

Hi,

Could you point to, or write, some tutorial-like documentation on how 
you use the MAC for this particular purpose?

I tried reading the mac* man pages in several instances before but can't 
seem to connect the theory described in there with how to apply it in a 
practical way.

> # uname -a
> FreeBSD test 7.2-RELEASE FreeBSD 7.2-RELEASE #0: Fri Nov 20 13:20:06 CET 2009
> root at test:/usr/obj/usr/src/sys/TEST amd64
> 
> 
> $ gcc -o program.o -c program.c -fPIC
> $ gcc -shared -Wl,-soname,w00t.so.1 -o w00t.so.1.0 program.o -nostartfiles
> $ ./env
> /libexec/ld-elf.so.1: environment corrupt; missing value for 
> /libexec/ld-elf.so.1: environment corrupt; missing value for 
> /libexec/ld-elf.so.1: environment corrupt; missing value for 
> /libexec/ld-elf.so.1: environment corrupt; missing value for 
> /libexec/ld-elf.so.1: environment corrupt; missing value for 
> ALEX-ALEX
> # id
> uid=1001(user) gid=1001(user) euid=0(root) groups=1001(portero),0(wheel)
> # /usr/sbin/getpmac
> biba/high(low-high)
> 
> And of course it's root.
> 
> Now,
> 
> $ setpmac biba/low\(low-low\) csh
> %pwd
> /tmp
> %./env
> /libexec/ld-elf.so.1: environment corrupt; missing value for 
> /libexec/ld-elf.so.1: environment corrupt; missing value for 
> /libexec/ld-elf.so.1: environment corrupt; missing value for 
> /libexec/ld-elf.so.1: environment corrupt; missing value for 
> /libexec/ld-elf.so.1: environment corrupt; missing value for 
> ALEX-ALEX
> # 
> ** OMG!! IT WORKED!!. 
> 
> BUT
> 
> # touch /etc/testing_the_exploit
> touch: /etc/testing_the_exploit: Permission denied
> # ls -l /usr/sbin/getpmac
> -r-xr-xr-x  1 root  wheel  7144 May  1  2009 /usr/sbin/getpmac
> # /usr/sbin/getpmac
> biba/low(low-low)
> 
> OOHHHHH, we have a toothless root. Maybe a "riit"?
> 
> 
> Pity these serious security mechanisms don't get a widespread usage.
> 
> 
> 
> 
> 
> 
> Borja.
> 
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