CSSE2310/CSSE7231 — Semester 2, 2023 Assignment 2
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CSSE2310/CSSE7231 — Semester 2, 2023
Assignment 2 (version 1.0)
Marks: 5o
weighting: 1o%
Due: 4:00pm Thursday 7 september, 2023
Introduction
The goal of this assignment is to ensure you have gained familiarity and skills with both the C programming
language and using a debugger (such as gdb(1)) to examine various characteristics of running programs. These 3
will be essential skills in other assignments for this course. For this assignment you will be given an executable
program (the“bomb”) which you have to “defuse” by entering the correct defusing phrases into the program 5
for each of the 1o bomb phases.
student conduct
This is an individual assignment. You should work on defusing your own bomb by yourself. You should feel 8
free to discuss aspects of C programming and the use of debuggers with your fellow students, but you shouldn,t
actively help (or seek help from) anyone with the defusing of particular phases. Do not share your approaches 10
to solving the bomb phases — even after the assignment deadline (as extensions may be given to other students). 11
You should note that each student will receive a diferent bomb and the strings that defuse your bomb will
be diferent to the strings that defuse another student,s bomb.
In short — don,t risk it! If you,re having trouble, seek help early from a member of the teaching staf. 14
Don,t be tempted to cheat. You should read and understand the statements on student misconduct in the
course proile and on the school website:
https://eecs.uq.edu.au/current-students/guidelines-and-policies-students/student-conduct 17
obtaining the “Bomb”
while logged in to moss.labs.eait.uq.edu.au, you should type the following command: 19
getbomb
This will create a subdirectory within your current directory named csse2310a2 and place the bomb iles into 21
that directory. The iles will include an executable called bomb and a number of source iles (.h and .c iles). 22
Your bomb (executable and source) will be diferent to the bombs for all other students. You will not receive 23
all of the source iles — just some of them — so you will not be able to build the bomb yourself. There is enough 24
information contained within the bomb executable and the supplied source iles in order for you to successfully
defuse all phases (although some of them are more di伍cult than others). You should note that some of the 26 bomb,s modules have been compiled with debugging support (-g lag to gcc) and some haven,t. 27
Running the “Bomb”
The bomb program will only run on moss.labs.eait.uq.edu.au and you are the only user who can run your bomb 29
program. Any attempt to run the program on another host or to run another user,s bomb will cause the bomb
to exit immediately. while in your csse231oa2 directory, you can execute the bomb by typing
./bomb
You may not want to do this until you are ready to try defusing the bomb. when you start the bomb program,
it will print out details of any phases you have already defused and it will print your current mark (out of 5o)
and the maximum mark you can obtain based on your attempts to date.
The bomb will then prompt you to enter the number of the phase to defuse next, followed by the string that
you believe defuses that phase (or a test string). You will be prompted for conirmation before that string is 37
tested. If you conirm your attempt and the string is incorrect then the bomb will “explode” and exit. If the 38 string is correct, then that phase is defused and you will not be able to solve it again. You will lose marks for 39 every time the bomb “explodes”. 40
The goal of this assignment is to enter the correct defusing strings for each phase, not to “hack”the bomb so 41
that it thinks the phases have been defused. The bomb checks for attempts to tamper with the bomb and will
“explode”if tampering is detected (e.g. if internal variables or data structures are modiied in a way that causes 43
the required defusing string to change). we also log all defusing attempts and will adjust marks afterwards (i.e. 44
reduce your marks) if the bomb has not been properly defused.
Hints
There are two demo phases that do not count for marks. You may attempt these as many times as you like by 47 entering either “demo1” or “demo2” when prompted for a phase to defuse. There is no mark penalty if either 48 of these demo phases “explodes.” 49
You should carefully read the supplied source code and be familiar with the use of gdb before attempting
to run the bomb. It is suggested you run the bomb from within a debugger rather than standalone but note
that attempts to defuse the bomb through the debugger are counted just the same as those without using a
debugger - i.e. if the bomb explodes when run through the debugger then this attempt still counts. Note that 53
you may get a warning message about“Missing separate debuginfos...”when you run the bomb within 54
gdb - you can safely ignore this message.
All phases have associated code and some debugging information and you will need to use a debugger to
set breakpoints, examine various variables etc. in order to determine the defusing strings. You may need to 57 learn about and use a number of features of gdb including (but possibly not limited to) watchpoints, automatic 58 display, conditional breakpoints, and/or breakpoint command lists to solve the phases more e伍ciently. 59
You should note that the code that determines each defusing string is not executed until AFTER the defusing
text is read from the user so you may need to enter some arbitrary text, debug the code to determine the defusing
string, quit the program and then run it again to enter the defusing string for that phase.
The bomb is deterministic - the same sequence of inputs from program startup will result in the same
operation each time, so the defusing string for each phase will not vary between runs of the bomb. However, 64
many of the functions within the bomb are not deterministic - they may return something diferent each time
they are called, and they may change internal data structures. This means that a defusing string may change over
time within a single run of the bomb program if you call functions from within gdb. Your goal is to determine
the defusing string that would have to be entered from a fresh run of the bomb - not the defusing string that
might apply after you have perhaps modiied the internal state of the bomb by using gdb commands.
submission
Every time you run the bomb, a record is kept of your interactions with it and your success/failure at defusing
each phase so no formal assignment submission is necessary - you can stop when you,ve solved all the phases
or when you are satisied with your mark.
Your submission time for the assignment will be considered to be the time of your last attempt to
defuse any phase of the bomb. You must make at least one attempt in order to be considered to have made
a submission. An attempt means either that the bomb explodes or a phase is defused.
Late penalties will apply as described in the CSSE231o/CSSE7231 course proile. Any attempt to defuse 77
the bomb after the deadline will result in a late penalty being applied to your whole assignment mark. You
may run the bomb program after the deadline in order to check your mark but if you attempt to defuse the
bomb (i.e. the bomb explodes or you successfully defuse a phase) then a penalty will apply. 80
Marks
There are 1o phases, each worth 5 marks. The mark you achieve for each phase is determined by the number
of attempts taken before you successfully defuse that phase. If you do not defuse a phase you will receive zero
marks for that phase. If you defuse a phase on the irst attempt, you will receive 5 marks for that phase. If it 84
takes you more than one attempt, your mark for that phase will be
4 x o.75(numbeT-of-attempts-2) 86
i.e. if it takes you 2 attempts, your mark for that phase will be 4 out of 5; 3 attempts gives you 3 out of 5; 4 87
attempts gives you 2.25 out of 5; etc. There is no limit on the number of attempts you can make at any phase 88
before succeeding. You should note that although each phase is worth the same number of marks, they are not 89
of equal difficulty. All marks are subject to an audit of our logs to ensure that you have correctly entered the
defusing strings and haven,t tampered with the bomb to defuse it in some other way. If you have not defused
a phase with the expected defusing string then you will receive zero marks for that phase.
2023-09-01