Concept explainers
Videos
a.
Explanation of Solution
Program:
File name: “DrugTests2.java”
//Define a class named DrugTests2
public class DrugTests2
{
//Define a main method
public static void main(String[] args)
{
//Declare the variables and initialize the values
int testedEmployee;
int week;
final int WEEKS = 52;
final int EMPLOYEES = 30;
int[] counts = new int[EMPLOYEES];
int countNeverTested = 0;
int x;
/*For loop to be executed until a list of randomly
selected employees who will be tested each
week for the next 52 weeks*/
for(week = 1; week <= WEEKS; ++week)
{
//Calculate the number of times each employee is selected
testedEmployee = 1 + (int) (Math.random() * EMPLOYEES);
//Print the result
System.out.print("week " + week + " Emp # " +
testedEmployee + " ");
//If remainder of week % 4 equals 0
if(week % 4 == 0)
//Print the result
System.out.println();
//Increment counts
counts[testedEmployee - 1]++;
}
//For loop to be executed until x exceeds 30
for(x = 0; x < EMPLOYEES; ++x)
{
//Print the result
System...
b.
Explanation of Solution
Program:
File name: “DrugTests3.java”
//Define a class named DrugTests3
public class DrugTests3
{
//Define a main method
public static void main(String[] args)
{
//Declare the variables and initialize the values
int testedEmployee;
int week;
final int WEEKS = 52;
final int EMPLOYEES = 30;
int[] counts = new int[EMPLOYEES];
int countNeverTested = 0;
int x;
int previousEmployee = -1;
/*For loop to be executed until a list of randomly
selected employees who will be tested each
week for the next 52 weeks*/
for(week = 1; week <= WEEKS; ++week)
{
/*Calculate the number of times each employee is selected*/
testedEmployee = 1 + (int) (Math.random() * EMPLOYEES);
/*If an employee number is selected
immediately after it was already selected*/
if(testedEmployee == previousEmployee)
{
//Decrement week
week--;
//Print the result
System.out.println("Employee #" + testedEmployee + " was selected two weeks in a row -- making new selection");
}
//Else
else
{
//Print the result
System.out.print("week " + week + " Emp # " +
testedEmployee + " ");
//If remainder of week % 4 equals 0
if(week % 4 == 0)
//Print the result
System...
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Chapter 8 Solutions
Java Programming, Loose-leaf Version
- The next problem concerns the following C code: /copy input string x to buf */ void foo (char *x) { char buf [8]; strcpy((char *) buf, x); } void callfoo() { } foo("ZYXWVUTSRQPONMLKJIHGFEDCBA"); Here is the corresponding machine code on a Linux/x86 machine: 0000000000400530 : 400530: 48 83 ec 18 sub $0x18,%rsp 400534: 48 89 fe mov %rdi, %rsi 400537: 48 89 e7 mov %rsp,%rdi 40053a: e8 d1 fe ff ff 40053f: 48 83 c4 18 add callq 400410 $0x18,%rsp 400543: c3 retq 0000000000400544 : 400544: 48 83 ec 08 sub $0x8,%rsp 400548: bf 00 06 40 00 mov $0x400600,%edi 40054d: e8 de ff ff ff callq 400530 400552: 48 83 c4 08 add $0x8,%rsp 400556: c3 This problem tests your understanding of the program stack. Here are some notes to help you work the problem: • strcpy(char *dst, char *src) copies the string at address src (including the terminating '\0' character) to address dst. It does not check the size of the destination buffer. You will need to know the hex values of the following characters:arrow_forwardA ROP (Return-Oriented Programming) attack can be used to execute arbitrary instructions by chaining together small pieces of code called "gadgets." Your goal is to create a stack layout for a ROP attack that calls a function located at '0x4018bd3'. Below is the assembly code for the function 'getbuf', which allocates 8 bytes of stack space for a 'char' array. This array is then passed to the 'gets' function. Additionally, you are provided with five useful gadgets and their addresses. Use these gadgets to construct the stack layout. Assembly for getbuf 1 getbuf: 2 sub $8, %rsp 3 mov %rsp, %rdi 4 call gets 56 add $8, %rsp ret #Allocate 8 bytes for buffer #Load buffer address into %rdi #Call gets with buffer #Restore the stack pointer #Return to caller. Stack Layout (fill in Gadgets each 8-byte section) Address Gadget Address Value (8 bytes) 0x4006a7 pop %rdi; ret 0x7fffffffdfc0 Ox4006a9 pop %rsi; ret 0x7fffffffdfb8 0x4006ab pop %rax; ret 0x7fffffffdfb0 0x7fffffffdfa8 Ox4006ad mov %rax,…arrow_forwardIn each of the following C code snippets, there are issues that can prevent the compilerfrom applying certain optimizations. For each snippet:• Circle the line number that contains compiler optimization blocker.• Select the best modification to improve optimization.1. Which line prevents compiler optimization? Circle one: 2 3 4 5 6Suggested solution:• Remove printf or move it outside the loop.• Remove the loop.• Replace arr[i] with a constant value.1 int sum( int ∗ ar r , int n) {2 int s = 0 ;3 for ( int i = 0 ; i < n ; i++) {4 s += a r r [ i ] ;5 p r i n t f ( ”%d\n” , s ) ;6 }7 return s ;8 }2. Which line prevents compiler optimization? Circle one: 2 3 4 5 6Suggested solution:• Move or eliminate do extra work() if it’s not necessary inside the loop.• Remove the loop (but what about scaling?).• Replace arr[i] *= factor; with arr[i] = 0; (why would that help?).1 void s c a l e ( int ∗ ar r , int n , int f a c t o r ) {2 for ( int i = 0 ; i < n ; i++) {3 a r r [ i ] ∗= f a c t o r…arrow_forward
- 123456 A ROP (Return-Oriented Programming) attack can be used to execute arbitrary instructions by chaining together small pieces of code called "gadgets." Your goal is to create a stack layout for a ROP attack that calls a function located at 'Ox4018bd3'. Below is the assembly code for the function 'getbuf, which allocates 8 bytes of stack space for a 'char' array. This array is then passed to the 'gets' function. Additionally, you are provided with five useful gadgets and their addresses. Use these gadgets to construct the stack layout. Assembly for getbuf 1 getbuf: sub mov $8, %rsp %rsp, %rdi call gets add $8, %rsp 6 ret #Allocate 8 bytes for buffer #Load buffer address into %rdi #Call gets with buffer #Restore the stack pointer #Return to caller Stack each Layout (fill in Gadgets 8-byte section) Address Gadget Address Value (8 bytes) 0x7fffffffdfc0 0x7fffffffdfb8 0x7fffffffdfb0 0x7fffffffdfa8 0x7fffffffdfa0 0x7fffffffdf98 0x7fffffffdf90 0x7fffffffdf88 Original 0x4006a7 pop %rdi;…arrow_forwardCharacter Hex value || Character Hex value | Character Hex value 'A' 0x41 יני Ox4a 'S' 0x53 0x42 'K' 0x4b 'T" 0x54 0x43 'L' Ox4c 0x55 0x44 'M' Ox4d 0x56 0x45 'N' Ox4e 'W' 0x57 0x46 Ox4f 'X' 0x58 0x47 'P' 0x50 'Y' 0x59 'H' 0x48 'Q' 0x51 'Z' Охба 'T' 0x49 'R' 0x52 '\0' 0x00 Now consider what happens on a Linux/x86 machine when callfoo calls foo with the input string "ZYXWVUTSRQPONMLKJIHGFEDCBA". A. On the left draw the state of the stack just before the execution of the instruction at address Ox40053a; make sure to show the frames for callfoo and foo and the exact return address, in Hex at the bottom of the callfoo frame. Then, on the right, draw the state of the stack just after the instruction got executed; make sure to show where the string "ZYXWVUTSRQPONMLKJIHGFEDCBA" is placed and what part, if any, of the above return address has been overwritten. B. Immediately after the ret instruction at address 0x400543 executes, what is the value of the program counter register %rip? (That is…arrow_forwardDraw out the way each of these structs looks in memory, including padding! Number the offsets in memory. 1 struct okay Name 2 { short a; 3 4 long number; 5 int also_a_number; 6 7 }; char* text; 1 struct badName 2 { 3 4 5 }; short s; struct okay Name n;arrow_forward
- You can create your own AutoCorrect entries. Question 19Select one: True Falsearrow_forwardBy default, all text is formatted using the Normal Style. Question 20Select one: True Falsearrow_forwardNode.js, Express.js, MongoDB, and Mongoose: Create, Read, Update, and Delete Operations There is a program similar to this assignment given as the last example, CRUD, in the lecture notes for the week that discusses the introduction to MongoDB. Basically, you need to adapt this example program to the data given in this assignment. This program will take more time that previous assignments. So, hopefully you'll start early and you've kept to the schedule in terms of reading the lecture notes. You can use compass if you want to create this database. Or, when your connection string in the model runs it will create the database for you if one does not yet exist. So, ⚫ create a Mongoose model based on the info given below. The index.html page is given in the same folder as these notes. • When you successfully run index.js and instantiate the model, your database is created. • Once the database is created, you need to perfect the addCar route so you can add data using the index.html page. •…arrow_forward
- 1. Enabled with SSL, HTTPS protocol is widely used to provide secure Web services to Web users using Web browsers on the Internet. How is a secure communication channel established at the start of communication between a Web server running HTTPS and a Web browser? Consider the following threats to Web security and how each of these threats is countered by a particular feature of SSL. Man-in-the-middle attack: An attacker interposes during key exchange, acting as the client to the server and as the server to the client. Password sniffing: Passwords in HTTP or other application traffic are “eavesdropped.” SYN flooding: An attacker sends TCP SYN messages to request a connection but does not respond to the final message to establish the connection fully. The attacked TCP module typically leaves the “half-open” connection around for a few minutes. Repeated SYN messages can clog the TCP module.arrow_forwardSQL Injection on UPDATE Statement for educational purpose only Based on the information below how do i update this code in order to update the emplyees field, eg admin nickname, email,address, phone number etc? ' ; UPDATE users SET NickName='Hacked' WHERE role='admin' -- If a SQL injection vulnerability happens to an UPDATE statement, the damage will be more severe, because attackers can use the vulnerability to modify databases. In our Employee Management application, there is an Edit Profile page (Figure 2) that allows employees to update their profile information, including nickname, email, address, phone number, and password. To go to this page, employees need to log in first. When employees update their information through the Edit Profile page, the following SQL UPDATE query will be executed. The PHP code implemented in unsafe edit backend.php file is used to update employee’s profile information. The PHP file is located in the /var/www/SQLInjection directory.arrow_forwardAnswer two JAVA OOP questions.arrow_forward
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