crashitoooo.py

import tempfile
import os
import sys

INCLUDES = """
#include <stdio.h>
#include <unistd.h>
#include <stdint.h>
#include <stdlib.h>
#include <time.h>
#include <stdbool.h>
"""

RAND_HEADER = """
static bool RANDOM_IS_SET = 0;
#define FAIL_PROBA 0.5
"""

RAND_CODE = """
    if (!RANDOM_IS_SET)
        srand(time(NULL));
    RANDOM_IS_SET = 1;
    if (((double)rand() / (double)RAND_MAX) < FAIL_PROBA)
        return NULL;
"""

MALLOC_BEGIN = """
void *malloc(size_t s)
{
    void *ptr;
"""

MALLOC_FAIL = """
    return NULL;
}
"""

MALLOC_GOOD = """
    ptr = sbrk(0);
    if ((intptr_t)(sbrk(s)) < 0)
        return NULL;
    return (uint8_t *)ptr + s;
}
"""

FREE = "void free(void *) { return; }\n"

BINARY = "crashito.so"

def generate(rand = None, n = None):
    tmp = tempfile.NamedTemporaryFile(delete=False)
    try:
        print(tmp.name)
        x = tmp.name + ".c"
        os.rename(tmp.name, x)
        tmp.name = x
        tmp.write(INCLUDES.encode())
        if rand is True:
            tmp.write(RAND_HEADER.format(n / 100).encode())
        tmp.write(MALLOC_BEGIN.encode())
        if rand is True:
            tmp.write(RAND_CODE.encode())
        if rand is True:
            tmp.write(MALLOC_GOOD.encode())
        else:
            tmp.write(MALLOC_FAIL.encode())
        tmp.write(FREE.encode())
        tmp.flush()
        os.system(f"gcc -shared -fPIC {tmp.name} -o {os.getcwd()}/{BINARY}")
    finally:
        tmp.close()
        os.unlink(tmp.name)

def main():
    if (len(sys.argv) == 1):
        print("all mallocs will fail !")
        generate()
        return 0
    rand = sys.argv[1].endswith("%")
    n = 0
    try:
        n = int(sys.argv[1].removesuffix("%"))
    except:
        return 84
    if rand:
        print(f"there will be a {n}% chance that the malloc fails !")
        generate(True, n)
    else:
        print(f"crashes after {n} mallocs")
        print("soon")
    return 0

if __name__ == "__main__":
    exit(main())