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How can we prevent format string vulnerabilities ?

Preventing format string vulnerabilities :

1.Always specify a format string as part of the program, not as an input:

  • Imagine you have a program that uses format strings, like “%s”. Instead of letting users input the format string, make it a fixed part of your code.
  • Example: Instead of taking a user input for the format string, use printf("Hello, %s!\n", name); where “%s” is part of the code, not something a user can control.

2. Make the format string a constant:

  • Constants are values that don’t change during the program’s execution. If possible, use constants for your format strings.
  • Example: Instead of printf(format, data);, use printf("%s", data); where “%s” is a constant format string.

3. If the above two practices are not possible, use defenses such as Format_Guard:

  • Sometimes, you might need user input as part of the format string. In such cases, use additional defenses or tools like Format_Guard to ensure that the input is safe.
  • Example: If you have to use user input in a format string, make sure it’s sanitized and doesn’t contain any malicious characters or sequences.

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