Software assurance labs.

Parte importante de cyber security es poder arreglar código. Aquí hay 5 labs que pueden servirles para entender porque. Fueron mi lab1 de mi materia de software assurance en Queen’s University Belfast, 2016.

Lab2_q1.c

/********************************************************/
/*    ELE8094 SwA Assessed Practical 2 Q1 2016          */
/*                                                      */
/* What is the value of result in the code              */
/* Explain the flaw                                     */
/* Define a variable fix and write a statement          */
/* with the correct expression                          */
/********************************************************/
#include <stdio.h>

int main(void)
{
  float a = 23;
  short b = 45;
  float c = 3.1415927;
  float result;

  result = a / b * c;
  printf("%f",result);
  return 0;
}

Lab2_q2.c

/********************************************************/
/*    ELE8094 SwA Assessed Practical 2 Q2 2016          */
/*                                                      */
/* What is the value of result in the code              */
/* Explain the flaw                                     */
/* Define a variable fix and write a statement          */
/* with the correct expression                          */
/********************************************************/
#include <stdio.h>

/* Integer Promotion */

int main(void)
{
  int a = -1;
  int b = 1;
  
  printf("%d\n", a < b);
 
  return 0;
}

Lab2_q3.c

/********************************************************/
/*    ELE8094 SwA Assessed Practical 2 Q3 2016          */
/*                                                      */
/* Explain the vulnerability in the                     */
/* code below.  Write code to provide a fix.            */
/********************************************************/
#include <stdio.h>
#include <string.h>
int main(void)
{
  char *pFirstName = "FirstName ";
  char *pLastName  = "LastName";
  char name[strlen(pLastName)+strlen(pFirstName)];


  strcat(strcpy(name, pFirstName), pLastName);
  printf("Name: %s\n", name);


  return 0;
}

Lab2_q4.c

/********************************************************/
/*    ELE8094 SwA Assessed Practical 2 Q4 2015          */
/*                                                      */
/* The following code accepts an 8 character            */
/* password from the user that must contain only        */
/* alphanumeric characters.                             */
/* Write a function to sanitise the input               */
/********************************************************/
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>

void getPassword(void);


int main(void)
{
  getPassword();

  return 0;
}

void getPassword(void)
{
  char password[9];
  int c=0;
  fputs("Enter Password of 8 Characters Containing Only Letters and Numbers\n", stdout);
   fgets(password, 9, stdin);
   for (int i = 0;i<8;i++){
    if (isalpha(password[i]) || isdigit(password[i])){c++;}}
    if (c!=8){
	c=0;
	printf("Please try again, your password does not match the criteria password: %s\n",password);}
else{printf("The password matches the criteria, congratulations, you can continue password: %s\n",password);} 
   
  return;
}

Lab2_q5.c

/********************************************************/
/*    ELE8094 SwA Assessed Practical 2 Q5 2016          */
/*                                                      */
/* Identify and Explain the vulnerability in the        */
/* code below.  Provide a fix.                          */
/********************************************************/

//the problem is that it does not have a null terminator
//this can cause undefined behavior if reading or worst in writing like Format
//String attack reference: http://wiki.c2.com/?NonNullTerminatedString

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

#define MAC_ADDRESS_LENGTH 36 
#define LINELENGTH 56         
#define SEPERATOR ':'


int GetMacAddress(char *MacAddress);
char outPutMacAddress[MAC_ADDRESS_LENGTH];

int main()
{

  if (1 == GetMacAddress(outPutMacAddress))
  {
    printf("Failed to get Mac address\n");
  }
  else
  {
    printf("%s\n", outPutMacAddress);
  }

  return 0;
}


int GetMacAddress(char *MacAddress)
{
  FILE *fp = NULL;
  char line[LINELENGTH];
  unsigned char counter = 1; 
  unsigned char i = 0;
  char *address;
  
  if (-1 == system("/sbin/ifconfig |grep --binary-files=text HWaddr >macAddress"))
  {
    printf("SYSTEM_ERROR_GET_MAC_ADDRESS_FAILURE\n");
    return 1;
  }
  else
  {
    fp=fopen("macAddress", "r");
    if(NULL == fp)
    {
      printf("Error reading macAddress file\n");
      return 1;
    }
    else
    {
      if (NULL == fgets(line, sizeof(line), fp))
      {
        printf("Error reading line from file - mac adddr\n");
        return 1;
      }
      else
      {
        address = strchr(line, SEPERATOR);
        if (NULL == address)
        {
          printf("Error in line format\n");
          return 1;
        }
        else
        {
          while ((address[counter] != 0) && (i < MAC_ADDRESS_LENGTH))
          {
            MacAddress[i] = address[counter];
            counter++;
            i++;
          }
        }
      }
      fclose(fp);
    }
  }
  if (-1 == remove("macAddress"))
  {
    printf("Error removing file\n");
    return 1;
  }  
  return 0;
}

Explanation in pdf. SanchezRicardo_40183863_Lab1