Lesson:

Buffer Overflows

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Take a look at this very simple C program that does not check the length of the input. Try entering a username that is longer than 8 characters and watch what happens.

oops.c
c void askForUsername()
{
  // Buffer can only hold 8 characters!
  char buffer[8];

  printf("Enter your username:\n");
  scanf("%s", buffer);
  printf("You entered: %s\n", buffer);
}

int main()
{
  while(1) askForUsername();

  return 0;
}

Running: "oops.c"

  Enter your username: 