bomb lab phase 5 github

By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. And when we execute it, it expects to receive certain inputs, otherwise it 'blows' up. I'll paste the code here. Are you sure you want to create this branch? If you notice, (the syntax will vary based off of what sort of system the bomb is run on) the machine code will have some variation of call to: 401135: be b8 25 40 00 mov $0x4025b8,%esi. You've defused the secret stage!'. Lets use blah again as out input for phase_2. Lets enter the string blah as our input to phase_1. This number was 115. phase_6() - This function does a few initial checks on the numbers inputed by the user. node5 How about the next one? I choose the first argument as 1 and then the second one should be 311. You just choose a number arbitarily from 0 to 6 and go through the switch expression, and you get your second argument. Please feel free to fork or star this repo if you find it helpful!***. I will list some transitions here: The ascii code of "flyers" should be "102, 108, 121, 101, 114, 115". In order to determine the comparisons used, it will be useful to look up or know Jumps Based on Signed Comparisons. we use, and get the following file (not the full code), We enter gdb, set a breakpoint at the phase 1. phase_3 You signed in with another tab or window. The main daemon is the. Then you may not find the key to the second part(at least I didn't). @cinos hi, I had same problem, I couldn't understand, I must have ecx 15 too, but I couldn't figure it out. LabID are ignored. In order to do this you must look at the various integers within the array and then place them in ascending order by the index of those integer containing elements. Please, Your answer could be improved with additional supporting information. Point breakdown for each phase: Phase 1 - 4: 10 points each; Phase 5 and 6: 15 points each; Total maximum score possible: 70 points; Each time the "bomb explodes", it notifies the server, resulting in a (-)1/5 point deduction from the final score for the lab. A tag already exists with the provided branch name. Link to Bomb Lab Instructions (pdf) in GitHub Repository. The bomb has blown up. Then the tricky part comes. If the line is correct, then the phase is defused and the bomb proceeds to the next phase. fun7 ??? This post walks through CMUs bomb lab, which involves defusing a bomb by finding the correct inputs to successive phases in a binary executable using GDB. this is binary bomb lab phase 5.I didn't solve phase 5. Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey. A tag already exists with the provided branch name. There exists a linked list structure under these codes. Here are a few useful commands that are worth highlighting: This command divides the screen into two parts: the command console and a graphical view of the assembly code as you step through it. Lets create our breakpoints to make sure nothing gets set to the gradebook! Such bombs, We will also find it helpful to distinguish between custom and, Custom Bomb: A "custom bomb" has a BombID > 0, is associated with a, particular student, and can be either notifying or quiet. This part is a little bit trickier. Are you sure you want to create this branch? initialize_bomb_solve 1) We have to find that number 'q' which will cause 12 (twelve) iterations. solution to each bomb is available to the instructor. Have a nice day! GitHub; Linkedin; Bomb Lab 7 minute read On this page. ", Quiet Bomb: If compiled with the NONOTIFY option, then the bomb, doesn't send any messages when it explodes or is defused. For more information, you can refer to this document, which gives a handy tutorial on the phase 6. node2 It's provided only for completeness. Phase 1 defused. This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository. Once we enter the function, we can check the registers that store the first two inputs: $rdi and $rsi. This looks just like phase 1. Learn more. Once you have updated the configuration files, modify the Latex lab, writeup in ./writeup/bomblab.tex for your environment. Up till now, there shouldn't be any difficulties. We can then set up a breakpoint upon entering phase_1 using b phase_1 and for the function explode_bomb to avoid losing points. More than 2 is fine but the code is only dependent on the first two numbers. Assignment #3: Bomb Lab (due on Tue, Feb 21, 2023 by 11:59pm) Introduction. First, interesting sections/function names: The bomb is defused . e = 16 int numArray[15] = {10, 2, 14, 7, 8, 12, 15, 11, 0, 4, 1, 13, 3, 9, 6}; int readOK; /** number of elements successfully read **/. Configure the Bomb Lab by editing the following file: ./Bomblab.pm - This is the main configuration file. Then, we can take a look at the fixed value were supposed to match and go from there: Woah. You encounter with a loop and you can't find out what it is doing easily. It is passed the inputed user phrase and the pass-phrase and then checks that the two strings are the same length. phase_1 At the onset of the program you get the string 'Welcome to my fiendish little bomb. What I know so far: first input cannot be 15, 31, 47, etc. Identify the generic Linux machine ($SERVER_NAME) where you will, create the Bomb Lab directory (./bomblab) and, if you are offering the, online version, run the autograding service. When in doubt "make stop; make start" will get everything in a stable state. Changing the second input does not affect the ecx. Each of you will work with a special "binary bomb". Alternative paths? We can get the full assembly code using an object dump: objdump -d path/to/binary > temp.txt. These lines indicate that if the first argument equal the last one(right before this line), then we get 0. You will get full credit for defusing phases 2 and 3 with less than 30 explosions. Given that our string is 6 characters long, it makes sense to assume that the function is iterating over each character in the loop and presumably doing something to them. CMU Bomb Lab with Radare2 Phase 1. Additional Notes on the Online Bomb Lab, * Since the request server and report daemon both need to execute, bombs, you must include $SERVER_NAME in the list of legal machines in, * All of the servers and daemons are stateless, so you can stop ("make, stop") and start ("make start") the lab as many times as you like. If nothing happens, download Xcode and try again. Going back all the way to the first iteration you needed to enter into the array at the 5th index, which is the first interger needed for the user input. To begin we first edit our gdbCfg file. The previous output from the strings program was outputted to stout in order that the strings are found in the binary. Curses, you've found the secret phase! False COVID-19 PCR Test. Find centralized, trusted content and collaborate around the technologies you use most. VASPKIT and SeeK-path recommend different paths. Use arg1 and address ebp-0x20 as arguments of function read_six_numbers. The address and stuff will vary, but . 10 January 2015. Each element in the array has an empty element directly adjacent to it. The request server builds the, bomb, archives it in a tar file, and then uploads the resulting tar, file back to the browser, where it can be saved on disk and, untarred. "make cleanallfiles" resets the lab from scratch, deleting all data specific to a particular instance of the lab, such, as the status log, all bombs created by the request server, and the, scoreboard log. Let's inspect the code at first. ", - Report Daemon (bomblab-reportd.pl). Well I know there has to be 6 numbers, with the range of 1-6, and there can't be any repeats. In order to solve the cypher, take a look at %esi and youll find an array of characters stored there, where each character has an index. This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. We can see that our string input blah is being compared with the string Border relations with Canada have never been better.. Software engineer at Amazon. So you think you can stop the bomb with ctrl-c, do you?' From the above comments, we deduce that we want to input two space-separated integers. The Hardware/Software Interface - UWA @ Coursera. BombID: Each bomb in a given instance of the lab has a unique, non-negative integer called the "bombID. Each bomb phase tests a different aspect of machine language programs: Phase 1: string comparison. I tried many methods of solution on internet. It's a great. Any numbers entered after the first 6 can be anything. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. I hope it's helpful. Enter a random string and then we stop at the phase 1 position, then we try printing out the information around 0x402400. On the other hand, custom quiet, Generic Bomb: A "generic bomb" has a BombID = 0, isn't associated with. I dont want to go through either solution all the way here, since the first one is a no-brainer and the second one is a little complicated. As we can see, it is fairly obvious that there is a loop somewhere in this function (by following the arrows). Use Git or checkout with SVN using the web URL. phase_6 to build a single generic bomb that every student attempts to defuse: This will create a generic bomb and some other files in ./bombs/bomb0: bomb* Generic bomb executable (handout to students), bomb.c Source code for main routine (handout to students), You will handout only two of these files to the students: ./bomb and ./bomb.c, The students will handin their solution files, which you can validate, This option is easy for the instructor, but we don't recommend it. Phase 1: There are two main ways of getting the answer. There is a small amount of extra credit for each additional phase . When you fail a phase, and the bomb goes off, you probably get the string 'BOOM!!!' Then you get the answer to be the pair(7, 0). You will only need, to modify or inspect a few variables in Section 1 of this file. Otherwise, the bomb explodes by printing " Specifically: Entering this string defuses phase_1. func4 ??? string_length From this mapping table, we can figure out the un-cyphered version of giants. Cannot retrieve contributors at this time. Your goal is to set breakpoints and step through the binary code using gdb to figure out the program inputs that defuse the bombs (and make you gain points). Making statements based on opinion; back them up with references or personal experience. Congratulations! Then we can get the range of the first argument from the line. Halfway there! Phase 5 reads in two numbers, the first of which is used as a starting point within a sequence of numbers. Based on the first user inputed number, you enter into that indexed element of the array, which then gives you the index of the next element in the array, etc. Raw Blame. can be started from initrc scripts at boot time. The key is that each time you enter into the next element in the array there is a counter that increments. It is important to step the test numbers in some way so you know which order they are in. We do this by typing, Then we request a bomb for ourselves by pointing a Web browser at, After saving our bomb to disk, we untar it, copy it to a host in the, approved list in src/config.h, and then explode and defuse it a couple, of times to make sure that the explosions and diffusion are properly, recorded on the scoreboard, which we check at, Once we're satisfied that everything is OK, we stop the lab, Once we go live, we type "make stop" and "make start" as often as we. The nefarious Dr. The first number we can try to be 6 and the second must be 682. Let's start with when it calls sym.read_six_numbers. func4() - This function was rather difficult for me to get through logically and so I ultimately had to take it as somewhat as a black box. f = 9. From the above annotations, we can see that there is a loop. Tools: Starting challenge; Phase_1: Phase_2: Phase_3: Phase_4: Phase_5: Phase_6: Bomb Lab Write-up. Going back to the code for phase_2, we see that the first number has to be 1. instructor builds, hands out, and grades the student bombs manually, While both version give the students a rich experience, we recommend, the online version. For each bomb, it tallies the number, of explosions, the last defused phase, validates each last defused, phase using a quiet copy of the bomb, and computes a score for each, student in a tab delimited text file called "scores.txt." If the two string are of the same length, then it looks to see that the first inputed character is a non-zero (anything but a zero). By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Check to see if the incremented character pointer is not null terminated. by hand by running their custom bomb against their solution: For both Option 1 and Option 2, the makebomb.pl script randomly, chooses the variant ("a", "b", or "c") for each phase. The request server, responds by sending an HTML form back to the browser. A Mad Programmer got really mad and created a slew of binary bombs. A tag already exists with the provided branch name. For example, after a function has finished executing, this command can be used to check the value of $rax to see the function output. "make start" runs bomblab.pl, the main. Unexpected uint64 behaviour 0xFFFF'FFFF'FFFF'FFFF - 1 = 0? gdbCfg phase 5. First, setup your bomb directory. The student then saves the tar file to disk. Pull up the function in Graph mode with VV, press p to cycle between views, and select the minigraph. (Add 16 each time) ecx is compared to rsp, which is 15, so we need ecx to equal to 15. For, example, "-p abacba" will use variant "a" for phase 1, variant "b" for. After satisfying this first requirement of phase_5 there is a comparison of the second user input to what turns out to be the sum of the numbers in the array you accessed. From the code, we can see that we first read in 6 numbers. If you type the correct string, then. You'll only need to have. On a roll! Make sure you update this. Such bombs are called "notifying bombs. If you're looking for a specific phase: Here is Phase 1. There is also a test that the first user inputed number is less than or equal to 14. After solving stage 1 you likely get the string 'Phase 1 defused. Guide and work-through for System I's Bomb Lab at DePaul University. Lets use that address in memory and see what it contains as a string. need to, but we are careful never to type "make cleanallfiles" again. Are you sure you want to create this branch? A loop is occurring. The code is comparing the string (presumably our input) stored in %eax to a fixed string stored at 0x804980b. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. It first checks that you have inputed 6 numbers, then that they are within the range of 1 through 6, and finally that they are all unique numbers, in that no number is repeated. Finally, we can see down at the bottom of the function that is being called after the contents of %eax and the fixed address 0x804980b have been pushed onto the stack. Can you help me please? @Jester so I looked at your reply to another question which is extremely similar to my question, actually the same exact question. Using gdb we can convince our guess. I found the memory position for the beginning of phase_1 and placed a break point there. There is an accessed memory area that serves as a counter. This series will focus on CMU's Binary Bomb challenge. I found various strings of interest. Cannot retrieve contributors at this time. So you got that one. Before the, lab goes live, you'll want to request a few bombs for yourself, run, them, defuse a few phases, explode a few phases, and make sure that, the results are displayed properly on the scoreboard. requires that you keep the autograding service running non-stop, because handouts, grading, and reporting occur continuously for the, duration of the lab. I then continue to run the program until I am prompted for a phrase to input. (Add 16 each time), ecx is compared to rsp, which is 15, so we need ecx to equal to 15, Changing the second input does not affect the ecx, first input is directly correlated to edx. Then we take a look at the assembly code above, we see one register eax and an address 0x402400. Readme (27 points) 2 points for explosion suppression, 5 points for each level question. GDB then stopped at the break before entering into the phase_1 function call. The makebomb.pl script also generates the bomb's solution. not 0, 1, 5, 6, 7, 8, 9, 10, 11, 12, 898, 1587, number is between 0 and 14 using comparison statement ordered by the total number of accrued points. The function then takes the address of the memory location within the array indexed by the second user input and places it in the empty adjacent element designated by the first user input. CIA_MKUltraBrainwashing_Drugs . correctly, else you and your students won't be able to run your bombs. In the "offline" version, the. Entering these numbers allows us to pass phase_3. This count is checked by the function read six numbers which also takes the user input string and formats them into integers that are then dumped onto the stack. There is a small grade penalty for explosions beyond 20. Let me know if you have any questions in the comments. phase_3 It is called recursively and in the end you need it to spit out the number 11. phase_1() - I'm first going to start stepping through the program starting at main. When in doubt "make stop; make start", However, resetting the lab deletes all old bombs, status logs, and the, scoreboard log. Then we encounter with an optimized switch expression. Lets enter a test string to let the program hit our break point. Please We can now see the assembly code. Looks like it wants 2 numbers and a character this time. 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14 because it is too easy for the students to cheat. Keep going! Control-l can be used to refresh the UI whenever it inevitably becomes distorted. For homework: defuse phases 2 and 3. is "defused." So, possible codes would be 1, 2, 4, 7, 11, 16 or 21, 22, 24, 27, 11, 16. node4 Help/Collaboration: I recieved no outside help with this bomb, other than. Actually in this part, the answer isn't unique. The third bomb is about the switch expression. This second phase deals with numbers so lets try to enter the array of numbers 0 1 2 3 4 5. DrEvil. Try this one.'. So, the value of node1 to node6 are f6, 304, b7, eb, 21f, 150. What differentiates living as mere roommates from living in a marriage-like relationship? phase_5 node1 Phase 1. If the first character in the input string is anything but a zero then the detonation flag is set to low and passed out the function. lesson and forces them to learn to use a debugger. Give 0 to ebp-4, which is used as sum of n0, n1, n2. Connect and share knowledge within a single location that is structured and easy to search. Custom, notifying bombs are constrained to run on a specific set of Linux, hosts determined by the instructor. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Each phase expects you to type a particular string on stdin. Thus, the second number in the series must be 1 greater than the first number, the third number in the series must be 2 larger than the second number, etc. Analysis of CME bomb lab program in linux using dbg, objdump, and strings. Enter disas and you will get a chunk of assembly for the function phase_1 which we put our breakpoint at. You can start and stop the autograding service as often as. Is it true that the first input has to be 5, 21, 37, etc? A tag already exists with the provided branch name. But when I put 4 1 6 5 2 3 or 3 6 1 2 5 4, it explodes. Ok, lets get right to it and dig into the code: So, what have we got here? We see that a strings_not_equal function is being called. A binary bomb is a program that consists of a sequence of phases. b = 6 Phase 4: recursive calls and the stack discipline. phase_6 Maybe function names or labels? You've defused the secret stage! I cannot describe the question better . Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. sig_handler My phase 5 is different from most other phase 5's I've found online, as it is the input of two integers. explode_bomb The report daemon finds the most recent, defusing string submitted by each student for each phase, and, validates these strings by applying them to a local copy of the, student's bomb. We've made it very easy to run the service, but, some instructors may be uncomfortable with this requirement and will. Also note that the binary follow the AT&T standard so instruction operations are reversed (e.g. The dumb way is to simply input all characters from a-z into the cypher and create a mapping table. Keep going! First thing I did was to search the binary using strings to see if there was anything interesting that pops out. What' more, there's a function call to read_six_numbers(), we can inspect it, Up till now, you should be able to find out that in this part, we are required to enter six numbers. Here is Phase 5. Considering this line of code. If you are offering the. phase_4 I believe this function also acts as the gateway to the secret phase. First, to figure out that the program wants a string as an input. Knowing that scanf() takes in a string format as its input, lets break right before scanf() is called and check the value of $esi. If that function fails, it calls explode_bomb to the left. explode_bomb. To learn more, see our tips on writing great answers. Please, Understanding Bomb Lab Phase 5 (two integer input), https://techiekarthik.hashnode.dev/cmu-bomblab-walkthrough?t=1676391915473#heading-phase-5. What is the Russian word for the color "teal"? phase_2 The source code for the different phase variants is in ./src/phases/. This works just fine, and I invite you to try it. . Lets clear all our previous breakpoints and set a new one at phase_2. to use Codespaces. There is also a "secret phase" that, only appears if students append a certain string to the solution to, Each phase has three variants: "a", "b", and "c". Some of the pass phrases could be integers, or a random set of characters if that is the case then the only way to figure things out is through dynamic analysis and disassembling the code. phase_5 () - This function requires you to go backwards through an array of numbers to crack the code. I should say the first half of the code is plain. Learn more about bidirectional Unicode characters. input.txt Public speaking is very easy. To review, open the file in an editor that reveals hidden Unicode characters. We can see that the last line shouldn't be contained in this switch structure, while the first four should be. How about saving the world? Using layout asm, we can see the assembly code as we step through the program. How a top-ranked engineering school reimagined CS curriculum (Ep. First bomb lab is a Reverse Engineering challenge, you have to read its assembly to find the message that . This post walks through the first 3 phases of the lab. To begin, let's take a look at the <phase_1> function in our objdump file: 0x00401100 4989e5 mov r13, rsp. I found: initialize_bomb The autograding service consists of four user-level programs that run, - Request Server (bomblab-requestd.pl). . phase_defused Dump of assembler code for function phase_5: 0x0000000000401002 <+0>: sub $0x18,%rsp ; rsp = rsp - 24, 0x0000000000401006 <+4>: lea 0x8(%rsp),%rcx ; rcx = *(rsp + 8) (function argument), 0x000000000040100b <+9>: lea 0xc(%rsp),%rdx ; rdx = *(rsp + 12) (function argument), 0x0000000000401010 <+14>: mov $0x401ebe,%esi ; esi = "%d %d", 0x0000000000401015 <+19>: mov $0x0,%eax ; eax = 0, 0x000000000040101a <+24>: callq 0x400ab0 <__isoc99_sscanf@plt>, 0x000000000040101f <+29>: cmp $0x1,%eax ; if (eax > 1) goto 0x401029, 0x0000000000401022 <+32>: jg 0x401029 , 0x0000000000401024 <+34>: callq 0x40163d ; if (eax <= 1) explode_bomb(), 0x0000000000401029 <+39>: mov 0xc(%rsp),%eax ; eax = *(rsp + 12) ::function parameter, 0x000000000040102d <+43>: and $0xf,%eax ; eax = eax & 0xf (last 2 bits), 0x0000000000401030 <+46>: mov %eax,0xc(%rsp) ; *(rsp + 12) = eax, 0x0000000000401034 <+50>: cmp $0xf,%eax ; if (eax == 0xf) explode_bomb(), 0x0000000000401037 <+53>: je 0x401065 , 0x0000000000401039 <+55>: mov $0x0,%ecx ; ecx = 0, 0x000000000040103e <+60>: mov $0x0,%edx ; edx = 0, 0x0000000000401043 <+65>: add $0x1,%edx ; edx = edx + 0x1, 0x0000000000401046 <+68>: cltq ; sign extend eax to quadword (rax), 0x0000000000401048 <+70>: mov 0x401ba0(,%rax,4),%eax ; eax = *(rax * 4 + 0x401ba0), 0x000000000040104f <+77>: add %eax,%ecx ; ecx = ecx + eax, 0x0000000000401051 <+79>: cmp $0xf,%eax ; if (eax != 0xf) goto 0x401043 (inc edx), 0x0000000000401054 <+82>: jne 0x401043 , 0x0000000000401056 <+84>: mov %eax,0xc(%rsp) ; *(rsp + 12) = eax, 0x000000000040105a <+88>: cmp $0xc,%edx ; if (edx != 12) explode_bomb(), 0x000000000040105d <+91>: jne 0x401065 , 0x000000000040105f <+93>: cmp 0x8(%rsp),%ecx ; if (ecx == *(rsp + 8)) goto 0x40106a, 0x0000000000401063 <+97>: je 0x40106a , 0x0000000000401065 <+99>: callq 0x40163d ; explode_bomb(), 0x000000000040106a <+104>: add $0x18,%rsp ; rsp = rsp + 24, 0x000000000040106e <+108>: retq ; return, --------------------------------------------------------------------------------.

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