pset4 recover - rick rolled - thinking about this the wrong way?

Question

This is my humble, little code. The comments shows my though process:

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char *argv[])
{
    if(argc != 2)
    {
        printf("Usage: ./recover image\n");
        return 1;
    }

    FILE *file = fopen(argv[1], "r");
    if (file == NULL)
    {
        return 2;
    }

    unsigned char bytes[512]; // since we're writing 512 bytes at the time
    char ch;

    while((ch = fgetc(file)) != EOF) // Loop through file as long as we dont meet EOF
    {
        fread(bytes, 512, 1, file); // read chunks of 512bytes, place it in array bytes
        printf("%s\n", bytes); // Get rick rolled

        if(bytes[0] == 0xff && bytes[1] == 0xd8 && bytes[2] == 0xff && (buffer[3] & 0xf0) == 0xe0;)
        {
          // nothing here, because apparently, by looking through the file
          // this way, all you get is a bit of a url to a Rick Astley song

        }
    }
    fclose(file); // close file after failing miserably. 
}

Output: 50.ly/surprise

If I put cs in front of 50, and go to that URL, i get rick rolled.

If I change my ch to an int, and run it, it seems like the output is more like machine code / printed noise.

I tried changing the while loop with a for loop:

for (int c = fgetc(file); c != EOF; c = fgetc(file))
    {
        fread(bytes, 512, 1, file);
        printf("%s", bytes);
        if(bytes[0] == 0xff && bytes[1] == 0xd8 && bytes[2] == 0xff)
        {
            printf("Nothing gets printed here\n");
        }  
    }

Doing it this way, all I get is noise. I am not able to get that URL by using a for loop.

The noise looks kind of like this:

iB.sȖG#=g߉7|իXmhvaY!t(q'        Qj5TQ@[_K3oHKzd[J
<thyƎbt\T`B\KEF
                ڇi/a1f{>smdak$#yPI=M`P|{q#Jb1#b4qEa!H^PFG$9_nl8ԻgKsOr
%n8T
    @).\X
*MNsp*E

What am I missing? What is this stuff I am reading out? Where are the jpeg's?

Answer 1

I figured it out. By using fread(bytes, 512, 1, file); as the while loop condition, I was able to move further into creating this problem, and eventually solve it.