pset2 crack.c Random Characters Follow When Getting Salt

Question

I've been scratching my head at this for the better part of a day now:

When I try to save the salt in a separate string called salt using the first and second characters of the second element of argv[], it comes back with 50, which is correct, and then most of the time 1 or 2 random characters will follow, even though I've specified the string length of salt to be 2.

I have used eprintf to see what the values are, and as you can see below, when I use eprintf("User salt is: %c%c\n", argv[1][0], argv[1][1]); straight away, the salt comes back correct, but when I use char salt[2] = {argv[1][0], argv[1][1]};, there is an extra tT after my salt of 50.

// Get the hashed password
int main(int argc, string argv[])
{
    // Only 2 words should be entered at the command-line
    if (argc == 2)
    {
        // Take the hashed password

        // Get the salt: the "salt" is the first 2 characters of the hashed keyword
        char salt[2] = {argv[1][0], argv[1][1]};
        eprintf("User hash is: %s\n", argv[1]);
        eprintf("User salt is: %c%c\n", argv[1][0], argv[1][1]);

        eprintf("Current salt string is: %s\n", salt);

Terminal:

~/workspace/pset2/crack/ $ ./crack 50JGnXUgaafgc
crack.c:19: User hash is: 50JGnXUgaafgc
crack.c:20: User salt is: 50
crack.c:22: Current salt string is: 50ؓtT
crack.c:33: Hash with current salt is: sawJaWbek0YZw
~/workspace/pset2/crack/ $ 

Any help would be very much appreciated!

Answer 1

Where's the end of string marker \0?

printf will keep printing whatever follows in memory until it sees the EOS marker, even into other areas of memory.

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