Crashme

Can you make this program crash?
nc 0.cloud.chals.io 17289

We’re given an ELF binary, a C source file, and a service to connect to. Here’s crashme.c:

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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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int main(int argc, char *argv[]){
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    char buffer[32];
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    printf("Give me some data: \n");
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    fflush(stdout);
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    fgets(buffer, 64, stdin);
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    printf("You entered %s\n", buffer);
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    fflush(stdout);
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    return 0;
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}

Seems like a very simple program. Simple programs require simple methods. fgets() can be vulnerable to buffer overflow, so why don’t we try to send a large number of characters? I sent aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa to the local program, which immediately resulted in a Segmentation fault.

This is what we need then! Send the same input to the program to get the flag:

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flag{segfaults_a_hackers_best_friend}