Hello I am quite a beginner in nasm. I am trying to write a program that executes a script, that takes one argument, with /bin/bash.
SECTION .data
command db '/bin/bash', 0
script db 'path/to/script', 0
script_arg db 'my_arg', 0
arguments dd command
dd script ; arguments to pass to commandline, in this case just the path to the script
dd script_arg
dd 0
SECTION .text
global _start
_start:
mov edx, 0 ; no environment variables are being used
mov ecx, arguments ; array of pointers has to be passed
mov ebx, command ; bash
mov eax, 11 ; invoke SYS_EXECVE
int 80h
The code above just executes the script with bash but does not add any arguments to the script itself. I tried to pass it as an additional argument but that does nothing. If I add the argument to the path to script string (path/to/script arg1) it breaks the terminal (color theme is set to just white text) and other than that does nothing.
Also what would be the easiest way of changing the contents of the arguments pointer array? How would I define that in .bss section and change its contents while the program is running? At least a point to the documentation about that would be nice...
When I put in run-bash.asm :
SECTION .data
command db '/bin/bash', 0
script db './test.sh', 0
script_arg db 'my_arg', 0
arguments dd command
dd script ; arguments to pass to commandline, in this case just the path to the script
dd script_arg
dd 0
SECTION .text
global _start
_start:
mov edx, 0 ; no environment variables are being used
mov ecx, arguments ; array of pointers has to be passed
mov ebx, command ; bash
mov eax, 11 ; invoke SYS_EXECVE
int 80h
And put in test.sh :
#!/usr/bin/env bash
echo "First argument is : $1"
The run it with :
nasm -f elf run-bash.asm
ld -m elf_i386 run-bash.o -o run-bash
chmod +x run-bash
./run-bash
# Output :
# First argument is : my_arg