20CYS113-20CYS181-Computer-Programming-and-Lab

20CYS113 - Computer-Programming and 20CYS181 - Computer Programming Lab

Overflow and Underflow

char

char overflow = 127;   // Maximum value for a char
char underflow = -128;  // Minimum value for a char

overflow++;  // Overflow: Value wraps around to -128
underflow--; // Underflow: Value wraps around to 127

unsigned char

unsigned char overflow = 255; // Maximum value for an unsigned char
unsigned char underflow = 0;  // Minimum value for an unsigned char

overflow++;  // Overflow: Value wraps around to 0
underflow--; // Underflow: Value wraps around to 255

short

short overflow = 32767;     // Maximum value for a short
short underflow = -32768;   // Minimum value for a short

overflow++;  // Overflow: Value wraps around to -32768
underflow--; // Underflow: Value wraps around to 32767

unsigned short

unsigned short overflow = 65535; // Maximum value for an unsigned short
unsigned short underflow = 0;    // Minimum value for an unsigned short

overflow++;  // Overflow: Value wraps around to 0
underflow--; // Underflow: Value wraps around to 65535

int

int overflow = 2147483647;   // Maximum value for an int
int underflow = -2147483648; // Minimum value for an int

overflow++;  // Overflow: Value wraps around to -2147483648
underflow--; // Underflow: Value wraps around to 2147483647

unsigned int

unsigned int overflow = 4294967295; // Maximum value for an unsigned int
unsigned int underflow = 0;         // Minimum value for an unsigned int

overflow++;  // Overflow: Value wraps around to 0
underflow--; // Underflow: Value wraps around to 4294967295

long

long overflow = 9223372036854775807;     // Maximum value for a long
long underflow = -9223372036854775808;   // Minimum value for a long

overflow++;  // Overflow: Value wraps around to -9223372036854775808
underflow--; // Underflow: Value wraps around to 9223372036854775807

unsigned long

unsigned long overflow = 18446744073709551615; // Maximum value for an unsigned long
unsigned long underflow = 0;                    // Minimum value for an unsigned long

overflow++;  // Overflow: Value wraps around to 0
underflow--; // Underflow: Value wraps around to 18446744073709551615

float

float overflow = FLT_MAX;      // Maximum value for a float
float underflow = FLT_MIN;     // Minimum normalized value for a float

overflow *= 2;  // Overflow: Value becomes infinity
underflow /= 2;  // Underflow: Value becomes denormalized or rounded to zero

double

double overflow = DBL_MAX;    // Maximum value for a double
double underflow = DBL_MIN;   // Minimum normalized value for a double

overflow *= 2;   // Overflow: Value becomes infinity
underflow /= 2;  // Underflow: Value becomes denormalized or rounded to zero

long double

long double overflow = LDBL_MAX;    // Maximum value for a long double
long double underflow = LDBL_MIN;   // Minimum normalized value for a long double

overflow *= 2;   // Overflow: Value becomes infinity
underflow /= 2;  // Underflow: Value becomes denormalized or rounded to zero

Example of Overflow and Underflow Vulnerability

#include <stdio.h>

// Function to perform a deposit operation
// Takes the current balance and the deposit amount as parameters
// Returns the updated balance after the deposit
unsigned int deposit(unsigned int balance, unsigned int amount) {
    return balance + amount;
}

// Function to perform a withdrawal operation
// Takes the current balance and the withdrawal amount as parameters
// Returns the updated balance after the withdrawal
unsigned int withdraw(unsigned int balance, unsigned int amount) {
     return balance - amount;
}

int main() {
    unsigned int balance = 1004967295; // Initial balance of ₹1004967295

    printf("Initial balance: ₹%u\n", balance);

    // Deposit
    unsigned int depositAmount = 3290000001; // Deposit amount of ₹3290000001
    balance = deposit(balance, depositAmount);
    printf("Balance after deposit: (Overflow) ₹%u\n", balance);

    // Withdraw
    unsigned int withdrawAmount = 10; // Withdraw amount of ₹10
    balance = withdraw(balance, withdrawAmount);
    printf("Balance after withdrawal: (Underflow) ₹%u\n", balance);

    return 0;
}

Handling Overflow and Underflow Vulnerability

#include <stdio.h>
#include <stdbool.h>
#include <limits.h>

// Function to perform a deposit operation
// Returns the updated balance after the deposit
unsigned int deposit(unsigned int balance, unsigned int amount) {
    // Check if the deposit amount exceeds the maximum balance
    if (UINT_MAX - balance < amount) {
        printf("Deposit amount exceeds the maximum balance.\n");
        return balance;
    } else {
        return balance + amount;
    }
}

// Function to perform a withdrawal operation
// Returns the updated balance after the withdrawal
unsigned int withdraw(unsigned int balance, unsigned int amount) {
    // Check if the balance is insufficient for withdrawal
    if (balance < amount) {
        printf("Insufficient balance for withdrawal.\n");
        return balance;
    } else {
        return balance - amount;
    }
}

int main() {
    unsigned int balance = 1004967295; // Initial balance of ₹1004967295

    printf("Initial balance: ₹%u\n", balance);

    // Deposit
    unsigned int depositAmount = 3290000001; // Deposit amount of ₹3290000001
    balance = deposit(balance, depositAmount);
    printf("Balance after deposit: ₹%u\n", balance);

    // Withdraw
    unsigned int withdrawAmount = 10; // Withdraw amount of ₹10
    balance = withdraw(balance, withdrawAmount);
    printf("Balance after withdrawal: ₹%u\n", balance);

    return 0;
}