Discovery / credits: Malvuln (John Page aka hyp3rlinx) (c) 2024
Original source: https://malvuln.com/advisory/3b9e9e130d52fe95c8be82aa4b8feb74.txt
Contact: malvuln13@gmail.com
Media: twitter.com/malvuln

Threat: Win32.STOP.Ransomware (smokeloader)
Vulnerability: Remote Code Execution (MITM)
Family: Stop
Type: PE32
MD5 3b9e9e130d52fe95c8be82aa4b8feb74
Vuln ID: MVID-2024-0676
Disclosure: 03/22/2024
Description:
There are two roads to exploitation for this particular ransomware, network "man-in-the-middle" or localized code execution, this advisory explores the network route.
Stop ransomware makes several HTTP GET requests over an insecure protocol TCP port 80 to download secondary PE files "build2.exe" and "build3.exe"
Moreover, no integrity checks are made on these files, well positioned third-party attackers who can intercept traffic can send back arbitrary exploit PE files.

[Domains contacted]
api.2ip.ua
sajdfue.com
sdfjhuz.com

[URLs]
/test2/get.php?pid=A41BF90C9233CFB5AAFE279642C3793D&first=true
/dl/build2.exe
/files/1/build3.exe

Stop ransomware actions.
1) Creates two directories under AppData\Local, named with unique ID e.g. "2197cd80-6ccb-4fe1-97c0-57d05945fac6"
2) Sets deny permissions on the directory for everyone Everyone (OI)(CI)(DENY)(D,DC)
3) Creates Windows registry Run key "SysHelper" for persistence, that points to a directory in AppData\Local
     e.g. \Users\Victim\AppData\Local\407868e1-6d5a-44f2-81ba-a8fedd9ea8db\StopCrypt.exe
4) Copies downloaded malware to a second created directory under AppData\Local

Exploit PE file executes as a child of the parent process malware and does following on our behalf.

1) Kill the parent process leveraging WIN32 API
     GetCurrentProcessId()
     Get parent process ID using CreateToolhelp32Snapshot()
     Call OpenProcess(PROCESS_TERMINATE, FALSE,  ppid)

2) Delete registry persistence Run key "SysHelper" 
3) Modify permissions on Stops backup directory to full access for everyone user group "/grant Everyone (OI)(CI)F" 
4) Deletes the malware backup directory under AppData\Local

[PoC/Video URL]
https://www.youtube.com/watch?v=S6E62YIOczo

[Sample]
https://bazaar.abuse.ch/sample/caeecccfee0962fbe3d4fb4ab336bf3d1230b12ad0821ff66f7a2cabc289c954/

By the way, "urlmon.dll" DLL file exported by "RansomLord v2" can be used against this sample for local exploitation.
Download: https://github.com/malvuln/RansomLord

All tests conducted successfully in a virtual machine environment using DNS and traffic redirection techniques.

Network Exploit/PoC
1) Compile the below "StopExploit.c" code as "build2.exe" and "build3.exe"
2) Create directory "dl" and save build2.exe here
3) Create directories "files/1" and save build3.exe here 
     Note, In my tests exploitation worked with just the "build2.exe" saved in the "dl" directory.
4) Start web server on TCP port 80 
     python -m http.server 80
5) Intercept the Stop Ransomware traffic and DNS to server we control, send back exploit files.

"StopExploit.c" 

#include "windows.h"
#include "stdio.h"
#include "tlhelp32.h"
#include "psapi.h"
#define BUFFER 512

//[+] Win32 STOP (smokeloader) Ransomware
//[+] MD5 3b9e9e130d52fe95c8be82aa4b8feb74
//[+] Remote Code Execution PoC
//[+] By John Page (aka hyp3rlinx) - malvuln
//[+] ApparitionSec
//[+] March 19, 2024 
//=========================================================================
//Abuses MITM insecure download over TCP port 80 to serve exploits to kill "Win32.Stop" malware
//Deletes persistence Run key "SysHelper" and secondary malware backup directory
//Tested successfully in Virtual Machine environment using DNS and network traffic redirection.
//=========================================================================
//
//linker -lpsapi (Dev-C++) x32
//
//=========================================================================
/** DISCLAIMER
Author is NOT responsible for any damages whatsoever by using this software or improper malware
handling. By using this code you assume and accept all risk implied or otherwise.
**/
//=========================================================================
DWORD getParentPID(DWORD pid);
void Kill_StopCrypt();
void DelSysHelper();
void EvictBackupMalware(char *maldir);

int main(void){
    Sleep(3000);
    DelSysHelper();
    return 666;
}

void Kill_StopCrypt(){
        DWORD pid, ppid;
        pid = GetCurrentProcessId();
        ppid = getParentPID(pid);
        HANDLE handle = OpenProcess(PROCESS_TERMINATE, FALSE,  ppid); 
     if (NULL != handle){
        DelSysHelper();
        TerminateProcess(handle, 0);
        CloseHandle(handle);
     }
}

void DelSysHelper(){
  char value[BUFFER];
  DWORD BufferSize = sizeof value;
  LONG rc = RegGetValueA(HKEY_CURRENT_USER, (LPCSTR)"Software\\Microsoft\\Windows\\CurrentVersion\\Run", (LPCSTR)"SysHelper", RRF_RT_ANY, NULL, (PVOID)&value, &BufferSize);
  if(rc == ERROR_SUCCESS){
     rc = RegDeleteKey(HKEY_CURRENT_USER, (LPTSTR)"Software\\Microsoft\\Windows\\CurrentVersion\\Run");
      if(rc == ERROR_SUCCESS){
         Kill_StopCrypt();
      }
      EvictBackupMalware(value);
   } 
}

DWORD getParentPID(DWORD pid){
    HANDLE h = NULL;
    PROCESSENTRY32 pe={0};
    DWORD ppid = 0;
    pe.dwSize = sizeof(PROCESSENTRY32);
    h = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
    if(Process32First(h, &pe)){
        do {
          if (pe.th32ProcessID==pid){
            ppid = pe.th32ParentProcessID;
            break;
         }
        } while(Process32Next(h, &pe));
    }
    CloseHandle(h);
    return (ppid);
}

char* concat(const char *s1, const char *s2){
   char *result = malloc(strlen(s1) + strlen(s2) + 1);
   strcpy(result, s1);
   strcat(result, s2);
   return result;
}

void EvictBackupMalware(char *maldir){
  char *infected_dir_path;
  int j = 0;
  int cnt = 0; 
  int i;
  char array[255][255];
  for (i=0; i <= (strlen(maldir)); i++){
    if (maldir[i] == '\\' || maldir[i]=='\0'){
        array[cnt][j]='\0';
        cnt++;
        j=0; 
    }else{
      array[cnt][j]=maldir[i];
      j++;  
      }
   }
    char result[256]="C:\\Users\\";
    char *r1;
    char *r2;
    for (i = 0; i < cnt; i++) {
        //printf(" %s %d\n", array[i],i);
        r1 = concat(result, array[2]);
        r2 = concat(r1, "\\AppData\\Local\\");
        //reg run key path points to this infected directory
        infected_dir_path = concat(r2, array[5]);
    }

    //printf("target: %s", infected_dir_path);
    char perm[256]="icacls ";
    char *r3;
    char *perm_cmd;
    r3 = concat(perm, infected_dir_path);

    //reset permissions on dir created by Stop ransomware
    perm_cmd = concat(r3, " /grant Everyone:(OI)(CI)F");

    system(perm_cmd);

    //evict backed up malware and dir
    char del_cmd[256]="RD ";
    char *force_del = concat(del_cmd, infected_dir_path);
    char *bye_bye_douche = concat(force_del, " /S /Q");

    system(bye_bye_douche);
}

//malvuln circa 2024

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