Format string vulnerabilities and preventive measures and examples in C language

Format String - It is an ASCII string used to format strings. It is an ASCII string consisting of text and formatting parameters.

For program output formatting, there are various format strings in C.

Format String Vulnerabilities

These errors occur due to programming mistakes that are easy for programmers to make. If any such error-prone code is passed to an output function such as printf, sprintf, etc., the write operation will be performed to an arbitrary memory address.

Example

#include<stdio.h>
#include<string.h>

int main(){

   char buffer[100];
   strncpy(buffer, "Hii ", 5);
   printf(buffer);

   return 0;
}

Precautions

There are some steps you can take to prevent format string vulnerabilities

• Try using the format string as The program replaces the input data. These problems can be easily solved using the "%s" string format.

• Create format string using constants and extract all variable strings as arguments to function calls instead of using them in constants string.

• For the case of constant and variable string initialization specifications Unable to follow usage format protection.

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