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CMPT479 Assignment 1

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CMPT479
Assignment 1

Written assignment
1. [9 points] Read each of the following news stories about malware:
(a) In 2019, a new type of Linux malware called Skidmap is found which makes the
victim’s computer mine Bitcoins for the attacker. Bitcoin mining consumes computational cycles to generate profit for the attacker. The malware is delivered by
tricking the user into running it and giving it administrator privileges. Once installed, Skidmap hides from the user by overwriting the “rm” (delete file) binary,
so that if the user attempts to remove it, Skidmap would schedule a re-installation
of itself again at a later date. Users usually cannot detect the presence of Skidmap.
(b) The UK’s National Health Service has suffered severe disruption to its services after
its computers were infected with the WannaCry ransomware in May 2017. WannaCry spreads with the EternalBlue exploit, which can infect computers remotely
using a specially crafted packet targeting vulnerable background daemons. Once
infected, the computer’s files are encrypted and cannot be encrypted without paying
money to the attackers, although the attackers often did not give the decryption
key even when paid. As of 2019, more than 1 million devices are sitll vulnerable to
this exploit.
(c) Two men were charged with bribing AT&T employees with more than 1 million
USD to install malware in the company’s computers. The malware recorded the
victim employees’ actions on AT&T computers and sends the data remotely to the
attackers to help the attackers penetrate its infrastructure. It appears that the
ultimate goal of the attackers was to steal unlock codes for AT&T phones.
For each of the above news stories, answer the following questions and explain:
i. [3 points] Which of the CIA principles is being violated?
ii. [3 points] Classify the malware by method of spread.
iii. [3 points] Classify the malware by payload.
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2. [10 points] State whether each of the following statements is true or false. For each,
explain why.
(a) [2 points] Cryptographic protocols generally rely on open design, even the ones that
use secret keys.
(b) [2 points] Buffer overflow attacks are made more powerful because of poor implementation of the principle of least common mechanism.
(c) [2 points] Modern PC operating systems generally do not follow the principle of
least privilege.
(d) [2 points] XSRF attacks usually require the attacker to gain full control over the
web server first.
(e) [2 points] A format string vulnerability gives both buffer overread and buffer overflow capabilities.
3. [16 points] Writing prompt: In the 1990s and 2000s, the most dangerous computer
malware were viruses and worms. Since then, viruses and worms have all but died out,
and trojan horses have become the dominant form of malware in frequency, prominence,
and impact. Based on your research and understanding of computer technology, why
did this happen?
The suggested word length for your answer is 300 to 500 words. Some sub-questions
that may help you organize your answer include:
• What has changed about our computer systems and how we interact with them?
• What assets are being protected using computer systems now that were not 20
years ago, or vice-versa?
• How has defensive strategy and mechanisms changed in the last 20 years?
• What are some societal changes linked to technological advances?
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Programming assignment
Buffer Overflow Vulnerabilities [45 points]
You have been given login.cpp, a simple program to check if the user’s login matches
a stored username and password using three different methods. Compile it and test it
with user input. Normally, the program checks a secret password.txt file to match your
input with the stored username and password, and grant access if they match. For your
convenience, you have been provided with such a password.txt file to test your code,
but you should assume the true password.txt file is different from the one you were
provided when you write your exploit.
There are three ways to log in using login.cpp:
1. ./login -i <username> <password> will check your username and password against
the secret password.txt file. It uses a randomized canary to detect buffer overflows, just like stack canaries.
2. ./login -j <username> <password> will check your username and password against
the secret password.txt file. This time, its hardcoded canary is dynamically computed against your username. Furthermore, the canary is placed in a different
location in memory.
3. ./login -k <username> <password> will check your username and password against
the secret password.txt file. This time, you cannot expect to overwrite the canary
correctly.
The login program is simplified: upon a successful login, it shows a congratulatory
message and does not do anything else. You are free to imagine that it will then allow
you to perform some privileged action, such as allowing access to confidential data or
launching a missile.
Your username must start with your own @sfu.ca username. For example, if my
e-mail is [email protected], I can choose taowang123 as my username for this assignment.
This is meant to discourage plagiarism so that each student’s answer will be unique.
(a) [15 points] Using a buffer overflow exploit, log in to the program using the first
method. Submit your username and password in a file called a1a.txt, with exactly
two lines, the first line being the username, and the second line being the password.
(Do not write anything else in your submitted file.) To repeat the above, the
username you choose must start with your own @sfu.ca username.
(b) [15 points] Using a buffer overflow exploit, log in to the program using the second
method. Submit your username and password in a file called a1b.txt exactly as in
part (a). The above restrictions apply.
(c) [15 points] Using a buffer overflow exploit, log in to the program using the third
method. Submit your username and password in a file called a1c.txt exactly as in
part (a). The above restrictions apply.
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For each part, as long as “Login successful!” appears, the attempt is considered successful
even if other warning messages appear.
All of your exploits should work on your own computer, considering all the buffer overflow
defenses. Therefore, you should not be trying to overwrite the return address. To
emphasize, you should not use any information in the password.txt file: it is there only
for your convenience.
Hints
To study the login.cpp code, you can try to modify it, for example, to log the values of
the variables at different lines in the code. It may also be a good idea to learn how to use
a memory disassembler like gdb to find where the variables are. Just remember to remove
your modifications to test your username and password against the original login.cpp file.
struct is used in this code to ensure that the variables are always placed in the right
order; the compiler would not re-arrange the order of variables.
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Submission instructions
You should submit the following files by the deadline:
• a1.pdf, with your answers to the written component.
• a1a.txt, a1b.txt, a1c.txt, with your answers to the programming component. These
must be textfiles, not, for example, Word documents renamed with a .txt extension.
Do not zip any files. You can submit these files any number of times and the system
will accept the last submission for each file, which overwrites previous submissions. You
are encouraged to make submissions as early as possible. It is important to name your files
correctly. Otherwise, we may not mark them!
Keep in mind that plagiarism is a serious academic offense; you may discuss the assignment, but write your assignment alone and do not show anyone your answers and code.
The submission system will be closed exactly 48 hours after the due date of the assignment. The 48 hours act as a no-penalty grace period. Submissions after then will not be
accepted unless you have requested an extension before the due date of the assignment. You
may receive no marks if there is no submission within 48 hours after the due date.
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Command Line Arguments
C++ (and most other languages) can accept command line arguments, which are additional commands given while running the code. Suppose we compiled mycode from mycode.cpp.
If we run the binary code file mycode as such:
./mycode abc 3 1
We say that mycode is run with 3 command line arguments; the first one is abc, the
second one is 3, and the third one is 1.
In mycode.cpp, the main function header will be written as follows:
int main(int argc, char ** argv) {

}
In this code, argc is an integer that counts the number of arguments (plus one, because
mycode also counts), and argv is a list of character arrays that contains the arguments. For
example:
int main(int argc, char ** argv) {
printf(“Number of arguments is: %d, first argument is %s\n”, argc, argv[1]);
return 0;
}
The output will be:
Number of arguments is 4, first argument is abc
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