Often you also need to use a real debugger like gdb, which is in a different challenge.
section .text
global _start
_start:
mov edx, len_buf_in
mov ecx, buf_in
mov ebx, 1
mov eax, 3 ; 3 = sys_read
int 0x80
mov al, [buf_in]
shl al, 1 ; double
add al, al ; add one more
mov [buf_out], al
mov edx, len_buf_out
mov ecx, buf_out
mov ebx, 1
mov eax, 4 ; 4 = sys_write
int 0x80
mov eax, 1 ; 1 = exit
int 0x80
section .data
buf_in db " ", 10, 13
len_buf_in equ $ - buf_in
buf_out db " ", 10, 13
len_buf_out equ $ - buf_out
The goal was to read numbers and triple them, but it fails, as shown below.
section .text
global _start
_start:
mov edx, len_buf_in
mov ecx, buf_in
mov ebx, 1
mov eax, 3 ; 3 = sys_read
int 0x80
mov al, [buf_in]
call print_c ; diagnostic
shl al, 1 ; double
call print_c ; diagnostic
add al, al ; add one more
call print_c ; diagnostic
mov [buf_out], al
mov edx, len_buf_out
mov ecx, buf_out
mov ebx, 1
mov eax, 4 ; 4 = sys_write
int 0x80
mov eax, 1 ; 1 = exit
int 0x80
print_c: ; prints the character in al
push eax
mov [print_cs+5], al
mov edx, len_print_cs
mov ecx, print_cs
mov ebx, 1
mov eax, 4
int 0x80
pop eax
ret
section .data
buf_in db " ", 10, 13
len_buf_in equ $ - buf_in
buf_out db " ", 10, 13
len_buf_out equ $ - buf_out
print_cs db " D: ", 10, 13
len_print_cs equ $ - print_cs
Now it prints out the result after each step, as shown below. This makes it easier to find errors.
ASM 104.1: Hex (10 pts)
Create a program that accepts a decimal number and converts it to hex, as shown below.
Convert this number to hex to obtain the flag:
ASM 104.2: Binary (10 pts)
Create a program that accepts a decimal number and converts it to binary, as shown below.
Convert this number to binary to obtain the flag:
ASM 104.3: Base64 (10 pts)
Create a program that accepts a decimal number and converts it to Base64, as shown below.
Convert this number to Base64 to obtain the flag:
ASM 104.4: Base58 (10 pts)
Create a program that accepts a decimal number and converts it to Base58Check, as shown below.
Convert this number to Base58 to obtain the flag:
