How to generate string for bruteforce attack using batchfile

Question

I have some code which can crack numeric rar file passwords. The code just increments the value of a variable (starting from 0) and I use that to check against the password to unrar using unrar command. But I want to generate strings for brute force attacks.

SET PASSWORD=0

:START
SET /A PASSWORD=%PASSWORD%+1  
UNRAR E -INUL -P%PASSWORD% "%PATH%\%NAME%" "%DESTINATION%"
IF /I %ERRORLEVEL% EQU 0 GOTO CLOSE
GOTO START

:CLOSE
echo Password Cracked...
echo Password is %PASSWORD%

Here

• %PATH% is path where rar file is located

• %NAME% is name of rar file

• %DESTINATION% is place where file is stored after UNRAR, In my code DESTINATION is "%TEMP%\%RANDOM%"

By applying this I am able to get the password, but it is not useful for strings which contain alpha characters.

How do I generate strings starting from "a", so I am able to crack alphabetic passwords too?

Answer 1

I consider this a crazy idea to do in CMD/batch, but it at least sounded like an interesting challenge. So, playing the part of the Professor from Gilligan's Island, I've decided to attempt to build a particle accelerator from coconuts.

Here's my entry. There might likely be a better solution using CMD/batch. The most favorable thing I can say about it is that it works. To adapt it to your purpose, change the ECHO statement inside the :INFINITE_LOOP to do something meaningful, like attempt to decompress the file and exit on success.

Here's a sample of the output as it runs:

'0'
'1'
...
'9'
...
'A'
'B'
...
'Y'
'Z'
'a'
'b'
...
'y'
'z'
'00'
'01'
...
'zy'
'zz'
'000'
'001'
...
'Car'
'Cas'
'Cat'
'Cau'
'Cav'
'Caw'
...

This solution should work with many characters (CHARSET contains all the characters to be used in the output string) with the exception of characters that cannot be assigned simply without escaping them in some manner (e.g. double quote, percent (maybe?), exclamation, ...). The script doesn't completely clean up after itself (you'll have to manually erase %ITER_FILE%), but it isn't too messy.

@ECHO OFF
SETLOCAL ENABLEDELAYEDEXPANSION

SET "CHARSET=0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghikjlmnopqrstuvwxyz"



:: ======================================================================
:: Setup

CALL :CONFIGURE_CHARSET "%CHARSET%"
REM ECHO MAX_INDEX: !MAX_INDEX!
REM SET

:: Put the smallest value in the file.
SET ITER_FILE=%TEMP%\ITERATOR_%RANDOM%.txt
ECHO.0>"%ITER_FILE%"



:: ======================================================================
:: Main Loop

:INFINITE_LOOP
CALL :READ_ITER "%ITER_FILE%" _ITER_CONTENTS
ECHO '!_ITER_CONTENTS!'
CALL :NEXT_ITER "%ITER_FILE%"

GOTO :INFINITE_LOOP

EXIT /B




:: "Increment" the contents of the "state variable" file.
:NEXT_ITER
SETLOCAL
SET "FILE=%~1"
SET "NEXT_FILE=%TEMP%\ITERATOR_NEXT_%RANDOM%.txt"
SET CARRY=1
FOR /F %%n IN (%FILE%) DO (
    IF !CARRY! EQU 1 (
        SET /A I_VALUE=%%n+1
        IF !I_VALUE! GTR %MAX_INDEX% (
            SET I_VALUE=0
            SET CARRY=1
        ) ELSE (
            SET CARRY=0
        )
    ) ELSE (
        SET I_VALUE=%%n
    )
    ECHO !I_VALUE!>>"!NEXT_FILE!"
)
REM    Add a new digit place.
IF !CARRY! EQU 1 (ECHO.0>>"!NEXT_FILE!")
MOVE /Y "%NEXT_FILE%" "%FILE%" >NUL
ENDLOCAL
EXIT /B


:: Read the contents of the "state variable" file and translate it
::   into a string.
:: The file is a series of lines (LSB first), each containing a single
::   number (an index).
:: Each index represents a single character from the CHARSET.
:READ_ITER
SETLOCAL
SET "FILE=%~1"
SET "VAR=%~2"
SET VALUE=
SET _V=
FOR /F %%n IN (%FILE%) DO (
    SET "VALUE=!VALUE_%%n!!VALUE!"
)
ENDLOCAL && SET %VAR%=%VALUE%
EXIT /B



:: Translate the index number to a character.
:TRANS_INDEX
SETLOCAL
SET "VAR=%~1"
SET "C=%~2"
SET IDX=
FOR /L %%i IN (0,1,%MAX_INDEX%) DO (
    IF "!VALUE_%%i!"=="!C!" SET IDX=%%i
)
SET "TRANS=!VALUE_%%i!"
ENDLOCAL && SET "%VAR%=%TRANS%"
EXIT /B




:: This is ugly magic.
:: Create variables to hold the translation of an index to a character.
:: As a side effect, set MAX_INDEX to the largest used index.
:CONFIGURE_CHARSET
SET CONFIG_TEMP=%TEMP%\CONFIG_%RANDOM%.cmd
IF EXIST "%CONFIG_TEMP%" DEL /Q "%CONFIG_TEMP%"
CALL :WRITE_CONFIG "%CONFIG_TEMP%" "%~1"
REM   Import all the definitions.
CALL "%CONFIG_TEMP%"
EXIT /B

REM Create a means to "add one" to a value.
:WRITE_CONFIG
SETLOCAL
SET "FILE=%~1"
SET "STR=%~2"

REM This is the "index" of the symbol.
SET "INDEX=%~3"
IF "!INDEX!"=="" SET INDEX=0

IF NOT "%STR%"=="" (
   SET "C=!STR:~0,1!"
   IF NOT "%~4"=="" (
       SET "FIRST=%~4"
   ) ELSE (
       SET "FIRST=!C!"
   )
   SET "D=!STR:~1,1!"
    IF "!D!"=="" (
        SET CARRY=1
        SET "D=!FIRST!"
    ) ELSE (
        SET CARRY=0
    )
    ECHO SET VALUE_!INDEX!=!C!>>"!FILE!"

    SET /A NEXT_INDEX=INDEX+1

    REM Recurse...
    SET MAX_INDEX=!INDEX!
    CALL :WRITE_CONFIG "!FILE!" "!STR:~1!" "!NEXT_INDEX!" "!FIRST!"
    IF !INDEX! GTR !MAX_INDEX! SET MAX_INDEX=!INDEX!
)
ENDLOCAL && SET MAX_INDEX=%MAX_INDEX%
EXIT /B