How a top-ranked engineering school reimagined CS curriculum (Ep. Learn more about bidirectional Unicode characters. fun7 ??? As a next step, lets input the test string abcdef and take a look at what the loop does to it. phase_4() - In this phase you are dealing with a recursively called function. Specifically: instructor builds, hands out, and grades the student bombs manually, While both version give the students a rich experience, we recommend, the online version. If so, pass the counter back to the calling function else continue the incrementing loop through string pointer until it hits null termination. ', It is not clear what may be the output string for solving stage 4 or 5. From the above annotations, we can see that there is a loop. func4 ??? You can enter any string, but I used TEST. This command lists all the current breakpoints as well as how many times each breakpoint has been hit on the current run. Changing the second input does not affect the ecx. phase_5 () - This function requires you to go backwards through an array of numbers to crack the code. Entering this string defuses phase_1. It is important to step the test numbers in some way so you know which order they are in. You signed in with another tab or window. Welcome to my fiendish little bomb. Since we know the final value is 6 letters/numbers, we know 72/6 = 12. So you think you can stop the bomb with ctrl-c, do you? The code must be at least six numbers long or else the bomb detonates. Here is the assembly code: The list of numbers I've inputed is this: So far from my understanding, two conditions need to be met: compare %ecx is 115 line 103 The following lines are annotated. First things first, we can see from the call to <string_length> at <phase_5+23> and subsequent jump equal statement our string should be six characters long. GitHub; Linkedin; Bomb Lab 7 minute read On this page. Each bomb phase tests a different aspect of machine language programs: Phase 4: recursive calls and the stack discipline, Phases get progressively harder. so I did. I found the memory position for the beginning of phase_1 and placed a break point there. - Main daemon (bomblab.pl). read_line phase_2 Each, variable is preceded by a descriptive comment. Next, as we scan through each operation, we see that a register is being . Load the binary, perform analysis, seek to Phase 6, and have a look at your task. The second input had to be a 11, because the the phase_4 code did a simple compare, nothing special. phase_6 The code shows as follows: After inspecting the code, you should figure out that the length of the string must be 6. aseje owo nla. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. 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. phase_3 Actually I'm not that patient and I didn't go through this part on my own. A string that could be the final string outputted when you solve stage 6 is 'Congratulations! We've made it very easy to run the service, but, some instructors may be uncomfortable with this requirement and will. You signed in with another tab or window. 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. A tag already exists with the provided branch name. invalid_phase Hello world. node6 You will get full credit for defusing phases 2 and 3 with less than 30 explosions. This continuous through all the user inputed indices and finally places the value zero in the last remaining empty element in the array. Lets enter the string blah as our input to phase_1. The main daemon is the. Then we can get the range of the first argument from the line. Then type the, This will create ps and pdf versions of the writeup, (1) Reset the Bomb Lab from scratch by typing, (2) Start the autograding service by typing, (3) Stop the autograding service by typing, You can start and stop the autograding service as often as you like, without losing any information. angelshark.ics.cs.cmu.edu this is binary bomb lab phase 5.I didn't solve phase 5. Also, where the arrow is, it's comparing the current node with the next node. For example, after a function has finished executing, this command can be used to check the value of $rax to see the function output. initialize_bomb_solve Next there is pattern that must be applied to the first 6 numbers. Are you sure you want to create this branch? Now lets get started with Phase 1! DePaul University - System I - Winter 2017, **Note: I made this repo with the intent to help others solve their own Bomb Labs. Lets set a breakpoint at strings_not_equal. Option 1: The simplest approach for offering the offline Bomb Lab is. In the first block of code, the function read_six_numbers is called which essentially confirms that it is six numbers which are seperated by a space (as we entered in the first part of this phase). A tag already exists with the provided branch name. This post walks through the first 3 phases of the lab. There is an accessed memory area that serves as a counter. If you are offering the online version, you will also need to edit the, ./src/config.h - This file lists the domain names of the hosts that, notifying bombs are allowed to run on. "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. 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. A note to the reader: For explanation on how to set up the lab environment see the "Introduction" section of the post. We can get the full assembly code using an object dump: objdump -d path/to/binary > temp.txt. To review, open the file in an editor that reveals hidden Unicode characters. Evil has created a slew of "binary bombs" for our class. je 0x40106a <phase_5+104> 0x0000000000401065 <+99>: callq 0x40163d <explode_bomb> ; explode_bomb . This works just fine, and I invite you to try it. phase_3 The "main daemon" starts and nannies the, request server, result server, and report deamon, ensuring that, exactly one of these processes (and itself) is running at any point in, time. e = 16 Less than two and the bomb detonates. Looks like it wants 2 numbers and a character this time. 3 lea's, a cmp of the output to 2 and a jump if greater than. start After solving stage 1 you likely get the string 'Phase 1 defused. The code is comparing the string (presumably our input) stored in %eax to a fixed string stored at 0x804980b. At each iteration, we check to see that the current value is double the previous value. We can open our strings.txt file and see that the string we found in memory is the beginning of the full string: I can see Russia from my house!. Are you sure you want to create this branch? Wow! 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. In the interests of putting more Radare2 content out there, here's a noob friendly intro to r2 for those who already have a basic grasp of asm, C, and reversing in x86-64. The two stipulations that you must satisfy to move to the last portion of this phase is that you have incremented the counter to 15 and that the final value when you leave the loop is 0xf (decimal 15). Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. I then continue to run the program until I am prompted for a phrase to input. node4 So, what do we know about phase 5 so far? (up to -6 points deducted) Each bomb explosion notification that reaches the staff results in a 1 point deduction, capped at -6 points total. The update. There are two basic flavors of Bomb Lab: In the "online" version, the, instructor uses the autograding service to handout a custom notifying, bomb to each student on demand, and to automatically track their, progress on the realtime scoreboard. Once we enter the function, we can check the registers that store the first two inputs: $rdi and $rsi. We can inspect its structure directly using gdb. Lets enter a test string to let the program hit our break point. Using layout asm, we can see the assembly code as we step through the program. Here is Phase 3. I know b7 < eb < f6 < 150 < 21f < 304, so the order of nodes should be 3 0 5 4 1 2 (or 2 5 0 1 4 3 - in ascending order) and I should add +1 to all numbers. I hope it's helpful. Answers that are vague, inaccurate, or . To subscribe to this RSS feed, copy and paste this URL into your RSS reader. You will handout four of these files to the student: bomb, bomb.c, ID, Each student will hand in their solution file, which you can validate. 1) We have to find that number 'q' which will cause 12 (twelve) iterations. The key part is the latter one. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Try this one.'. Readme (27 points) 2 points for explosion suppression, 5 points for each level question. Guide and work-through for System I's Bomb Lab at DePaul University. 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. A tag already exists with the provided branch name. So, possible codes would be 1, 2, 4, 7, 11, 16 or 21, 22, 24, 27, 11, 16. Which one to choose? I should say the first half of the code is plain. Lets use that address in memory and see what it contains as a string. Students download their bombs, and display the scoreboard by pointing a browser at a simple HTTP, server called the "request server." phase_2 My phase 5 is different from most other phase 5's I've found online, as it is the input of two integers. Going back to the code for phase_2, we see that the first number has to be 1. to use Codespaces. Please, Your answer could be improved with additional supporting information. @Jester so I looked at your reply to another question which is extremely similar to my question, actually the same exact question. Cannot retrieve contributors at this time. Q. 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 **/. All things web. Make sure you update this. Once you have updated the configuration files, modify the Latex lab, writeup in ./writeup/bomblab.tex for your environment. DrEvil. Find centralized, trusted content and collaborate around the technologies you use most. Students earn points for defusing phases, and they, lose points (configurable by the instructor, but typically 1/2 point), for each explosion. You've defused the secret stage! Each element in the array has an empty element directly adjacent to it. If not null terminated then preserve the originally passed pointer argument by copying it to %rdx. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. The Hardware/Software Interface - UWA @ Coursera. There are 6 levels in the bomb and our task is to diffuse it. Entering these numbers allows us to pass phase_3. The other option for offering an offline lab is to use the, makebomb.pl script to build a unique quiet custom bomb for each, linux> ./makebomb.pl -i -s ./src -b ./bombs -l bomblab -u -v , This will create a quiet custom bomb in ./bombs/bomb for the. . The variable being used in this comparison is $eax. Up till now, there shouldn't be any difficulties. phase_5 can be started from initrc scripts at boot time. The smart way of solving this phase is by actually figuring out the cypher. This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository. 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. Going through func4, we get the value of d at 400ff7 and 400fe2 to be (14 + 0) >> 1 = 7. Are you sure you want to create this branch? skip First you must enter two integers and the bomb will detonate if you enter more or less than that. 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. . Learn more about bidirectional Unicode characters, #######################################################, # Copyright (c) 2002-2013, R. Bryant and D. O'Hallaron, This directory contains the files that you will use to build and run, the CS:APP Bomb Lab. You will only need, to modify or inspect a few variables in Section 1 of this file. In addition, most, phase variants are parameterized by randomly chosen constants that are, assigned when a particular bomb is constructed. So, I mapped out the array from element 0 to 15 and then worked backwards through it to find the element I needed to start with. any particular student, is quiet, and hence can run on any host. Each time the "bomb explodes", it notifies the server, resulting in a (-)1/5 point deduction from the final score for the lab. Let's start with when it calls sym.read_six_numbers. This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository. On line <phase_4+16>, the <phase_4> function is pushing a fixed value stored at memory address 0x8049808 onto the stack right before a call to scanf is made. ", Quiet Bomb: If compiled with the NONOTIFY option, then the bomb, doesn't send any messages when it explodes or is defused. The second number is simply linked to the first number: 0 must be followed by 704, 1 by 848, 2 by 736, 3 by 346, 4 by 607, 5 by 147, 6 by 832, and 7 by 536. servers running. You signed in with another tab or window. Next it takes the address of the memory location within the array indexed by the third user input and places in the empty adjacent element designated by the second user input. phase_defused() - So this function implements stack protection by adding, checking, and removing a canary. 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. I am currently stuck on bomb lab phase 5. And, as you can see at structure, the loop iterates 6 times. There is a small grade penalty for explosions beyond 20. This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. There was a problem preparing your codespace, please try again. When in doubt "make stop; make start" will get everything in a stable state. "make start" runs bomblab.pl, the main. 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. You have 6 phases with which to blow yourself up. Each phase expects the student to enter a particular string, on stdin. Subtract original pointer from %eax and get the running total of the string. solution to each bomb is available to the instructor. Run the following commands to create text files which we will look at later: You should now have two files: strings.txt and assembly.txt. Mar 19, . Breakpoints can be set at specific memory addresses, the start of functions, and line numbers. I will likely take another shot at figureing out exactly how to come up with the solution by following the implemented logic but I eventually brute forced it, which took a whole 30 seconds to figure out. It's a great. Curses, you've found the secret phase! I'm guessing that this function will likely compare the string that I inputed to some string stored in memory somewhere. From here, we have two ways to solve this phase, a dumb way and a smart way. Enter a random string and then we stop at the phase 1 position, then we try printing out the information around 0x402400. A loop is occurring. Then you set a breakpoint at 4010b3 and find the target string to be "flyers". phase_4 "/> dearborn police incident reports. 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. phase_6 When in doubt "make stop; make start", However, resetting the lab deletes all old bombs, status logs, and the, scoreboard log. ", - Report Daemon (bomblab-reportd.pl). These numbers act as indices within a six element array in memory, each element of which contains a number. student whose email address is and whose user name is : bomb* Custom bomb executable (handout to student), bomb.c Source code for main routine (handout to student). If this is a duplicate of another question, please link it so future readers can find it if their search turns up this question first. And your students will have to get, (2) Starting the Bomb Lab. Thus on the 14th iteration if I needed a 6, I would need to be in the 14th index of the array on the 13th iteration, then on index 2 of the 12th iteration. Learn more. Simple function made to look like a mess. explode_bomb. Now you can see there are a few loops. GDB then stopped at the break before entering into the phase_1 function call. These look like they could pertain to the various phases of the bomb. Phase 1 is sort of the "Hello World" of the Bomb Lab. I keep on getting like 3 numbers correctly, and then find the only possible solutions for the other 3 incorrect, so I am at a loss. This file is created by the report daemon, 4.4.4. Let me know if you have any questions in the comments. gdb ./bomb -q -x ~/gdbCfg. phase_1 Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. The request server also creates a copy of the bomb and its, - Result Server (bomblab-resultd.pl). $ecx is the output of the loop, Values attached to letters based on testing: 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. The Bomb Lab teaches students principles of, machine-level programs, as well as general debugger and reverse, A "binary bomb" is a Linux executable C program that consists of six, "phases." You've defused the secret stage!'. It's obvious that the first number should be 1. Not the answer you're looking for? Check to see if the incremented character pointer is not null terminated. Bomb Lab: Phase 5. Try this one. It also might be easier to visualize the operations by using an online disambler like https://onlinedisassembler.com/ to see a full graph. On the bright side, at least now we know that our string should come out of the loop as giants. Are you sure you want to create this branch? Score!!! Now lets take a quick look at the disassebly to see what variables are being used. phase_5 Lets use blah again as out input for phase_2. Please, Understanding Bomb Lab Phase 5 (two integer input), https://techiekarthik.hashnode.dev/cmu-bomblab-walkthrough?t=1676391915473#heading-phase-5. The second input had to be a 11, because the the phase_4 code did a simple compare, nothing special. Each phase expects you to type a particular string on stdin.If you type the correct string, then the phase is defused and the bomb proceeds to the next phase. Please 'But finding it and solving it are quite different' Phase 1 defused. If one of these processes dies for some reason, the main daemon, detects this and automatically restarts 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. You create a table using the method above, and then you get the answer to be "ionefg". Work fast with our official CLI. Thus, they quickly learn to set breakpoints before, each phase and the function that explodes the bomb. Although the problems differ from each other, the main methods we take are totally the same. Former New York University and Peking University student. You signed in with another tab or window. Phase 1: There are two main ways of getting the answer. "make stop" kills all of the running, servers. From phase_4, we call the four arguments of func4 to be a, b(known, 0), c(known, 14), d(known, 0). string_length() - This function first checks to see that the passed character pointer in %rdi is not null terminated. You signed in with another tab or window. phase_2() - This phase is about typing in a code. I found: initialize_bomb A tag already exists with the provided branch name. As its currently written, your answer is unclear. Thinking of the func4 function, we put two lines together to see more clearly. Is there any extra credit for solving the secret phase. Well It's provided only for completeness. Here is Phase 5. Any numbers entered after the first 6 can be anything. I know that due to x86-64 calling conventions on programs compiled with GCC that %rdi and %rsi may contain pointers to the words to compare. Enter disas and you will get a chunk of assembly for the function phase_1 which we put our breakpoint at. Then, we can take a look at the fixed value were supposed to match and go from there: Woah. Let's have a look at the phase_4 function. For homework: defuse phases 2 and 3. b = 6 Link to Bomb Lab Instructions (pdf) in GitHub Repository phase_5() - This function requires you to go backwards through an array of numbers to crack the code. It appears that there may be a secret stage. Load the binary, perform analysis, seek to Phase 6, and have a look at your task. enjoy another stunning sunset 'over' a glass of assyrtiko, English version of Russian proverb "The hedgehogs got pricked, cried, but continued to eat the cactus". Phase 5 reads in two numbers, the first of which is used as a starting point within a sequence of numbers. bomblab-Angr/Phase 5 x86_64.ipynb. Then the tricky part comes. The LabID must not have any spaces. Details on Grading for Bomb Lab. We can see that our string input blah is being compared with the string Border relations with Canada have never been better.. Given you ultimately needed to have the element containing 0xf to exit after 15 iterations, I saw that f was at array element index 6. Contribute to CurryTang/bomb_lab_solution development by creating an account on GitHub. It is clearly the most compelling and fun for the, students, and the easiest for the instructor to grade. 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14 Thus the memory array contains an element that holds an integer followed by an element that holds a memory location from within the same array to one of the integers, followed by another integer, and then another memory location from within the array, etc, until the end of the array. Solve a total of 6 phases to defuse the bomb. How about the next one? d = 12 A tag already exists with the provided branch name. 1 2 6 24 120 720 0 q 777 9 opukma 4 2 6 3 1 5 output Welcome to my fiendish little bomb. Pull up the function in Graph mode with VV, press p to cycle between views, and select the minigraph. * phase2a.c - To defeat this stage the user must enter a sequence of, * 6 nonnegative numbers where x[i] = x[i-1] + i. The nefarious Dr. I used a linux machine running x86_64. Let's inspect the code at first. You get to know that the input sequence must be an arbitary combination of number 1,2,3,4,5,6. This second phase deals with numbers so lets try to enter the array of numbers 0 1 2 3 4 5. The user input is then, 4 5 1 6 2 3. Using layout asm, we can see the assembly code as we step through the program. We can see that the last line shouldn't be contained in this switch structure, while the first four should be. The binary bomb is a very good exercise to learn the assembly language.I started this exercise for fun. Also note that the binary follow the AT&T standard so instruction operations are reversed (e.g. What differentiates living as mere roommates from living in a marriage-like relationship? phase_5 GitHub Microsoft is acquiring GitHub!Read our blog and Satya Nadella's post to learn more. To begin we first edit our gdbCfg file. 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." Here is Phase 4. GET /%s/submitr.pl/?userid=%s&lab=%s&result=%s&submit=submit HTTP/1.0 Also run the command i r to see what the values of the variables are. CMU Bomb Lab with Radare2 Phase 1. I try a input sequence "aaaaaa" and get the value after transitions doesn't change at all, which means that the output of a given input is unique. Are you sure you want to create this branch? Jumping to the next "instruction" using gdb, Binary Bomb Phase 5 issue (my phase 5 seems to be different from everyone elses), Memory allocation and addressing in Assembly, Tikz: Numbering vertices of regular a-sided Polygon. Segmentation fault in attack lab phase5. A clear, concise, correct answer will earn full credit. From this, we can see that the input format of read_six_numbers should be 6 space-separated integers. First, to figure out that the program wants a string as an input. strings_not_equal On whose turn does the fright from a terror dive end? Give 0 to ebp-8, which is used as loop condition. So you got that one. phase_1 LabID are ignored. If nothing happens, download Xcode and try again. First bomb lab is a Reverse Engineering challenge, you have to read its assembly to find the message that . If you accidentally kill one of the daemons, or you modify a daemon, or the daemon dies for some reason, then use, "make stop" to clean up, and then restart with "make start". A tag already exists with the provided branch name. ', After solving stage 3 you likely get the string 'Halfway there! 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. Pretty confident its looking for 3 inputs this time. Due to address randomization and nonexecutable stack, we are supposed to use Return Oriented Programming (ROP) to pass the string pointer of a given cookie value as argument to a function called touch3. You won't be able, to validate the students handins. 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. There are no explicit handins and the lab is self-grading. Maybe function names or labels? phase_3() - In this phase you are required to type in another code of at least 2 numbers. I see the output 'Phase 1 defused. Video on steps to complete phase one of the lab.If y'all real, hit that subscribe button lmao 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. Keep going! Connect and share knowledge within a single location that is structured and easy to search. Analysis of CME bomb lab program in linux using dbg, objdump, and strings. rev2023.4.21.43403. This number was 115. phase_6() - This function does a few initial checks on the numbers inputed by the user. But when I put 4 1 6 5 2 3 or 3 6 1 2 5 4, it explodes. When I get angry, Mr. Bigglesworth gets upset. VASPKIT and SeeK-path recommend different paths. c = 1 without any ill effects. offer the lab. Use Git or checkout with SVN using the web URL. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. I found various strings of interest. The bomb has blown up. How about the next one? mov a b moves data from a to b as opposed to b to a). Actually in this part, the answer isn't unique. If the event was a defusion, the message also, contains the "defusing string" that the student typed to defuse the, Report Daemon: The report daemon periodically scans the scoreboard log, and updates the Web scoreboard. You encounter with a loop and you can't find out what it is doing easily. Informal Explanations of Phases 1 through 6: I have spent approximately 26 hours on this assignment. If you type the correct string, then the phase is defused and the bomb proceeds to the next phase. As an experienced engineer, I believe you can figure out that there are two arguments, each of which should be integers. If not then the detonation flag that was initialized to 1 is not set to low and will eventually trigger the detonate function.
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