How do I type in hex input into radare2 debug mode?

Question

#include<stdio.h>
#include<stdlib.h>
int main() {
    puts("Enter input: ");
    char buf[100];
    fgets(buf, 100, stdin);
    printf("%s", buf);
}

Suppose I am debugging a program, such as the one above, where I need to type in some input. Usually, what radare2 does is that it will allow me to type in any ascii input whenever the program demands that I have user input, and it will look like the following:

Enter input: Hello
Hello

However, what if I need to type in hex input? Normally, if I wanted to use hex input for my program outside of radare2, I would use a command that looks like the following:

python -c "print('\x48\x65\x6c\x6c\x6f')" | ./program

But if I am debugging the program with radare2 and use something like \x48\x65\x6c\x6c\x6f as the input, radare2 will literally interpret the backlash x as a string that looks like "\x" instead of interpreting the input as hexadecimal. How would I go about inputting hex while inside of radare2 properly?

Answer 1

• Write the string in a file:

  $ echo -e '\x48\x65\x6c\x6c\x6f' > p.text    
  

  or

  $ python -c "print('\x48\x65\x6c\x6c\x6f')" > p.text   
  

• Execute radare2:

  $ r2 -d program 
  

• Once inside of r2 execute dor (an alias for rarun2) and set the stdin to the file:

  [0x7f1a2522a090]> dor stdin=p.text
  [0x7fb15f311e06]> doo # Reopen in debugger mode