Phase 1. The input should be "4 2 6 3 1 5". These look like they could pertain to the various phases of the bomb. phase_1 Let's inspect the code at first. If you are offering the. "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. phase_defused. phase_4 As we can see, it is fairly obvious that there is a loop somewhere in this function (by following the arrows). So you got that one. To review, open the file in an editor that reveals hidden Unicode characters. If the student enters the expected string, then that phase. In this part, we are given two functions phase_4() and func4(). instructor builds, hands out, and grades the student bombs manually, While both version give the students a rich experience, we recommend, the online version. In order to defuse the bomb, students must use a debugger, typically, gdb or ddd, to disassemble the binary and single-step through the, machine code in each phase. GitHub; Linkedin; Bomb Lab 7 minute read On this page. You create a table using the method above, and then you get the answer to be "ionefg". . Going back to the code for phase_2, we see that the first number has to be 1. As an experienced engineer, I believe you can figure out that there are two arguments, each of which should be integers. Asking for help, clarification, or responding to other answers. The student then saves the tar file to disk. You don't need root access. Phase 1 defused. What I know so far: first input cannot be 15, 31, 47, etc. angelshark.ics.cs.cmu.edu So you think you can stop the bomb with ctrl-c, do you?' It should look like this. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. If nothing happens, download GitHub Desktop and try again. For homework: defuse phases 2 and 3. Ahhhh, recursion, right? explode_bomb. A tag already exists with the provided branch name. If you're looking for a specific phase: Here is Phase 1. Bomb Lab - 0x70RVS 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. The Hardware/Software Interface - UWA @ Coursera. The nefarious Dr. phase_5 () - This function requires you to go backwards through an array of numbers to crack the code. Up till now, there shouldn't be any difficulties. 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. node1 Lets clear all our previous breakpoints and set a new one at phase_2. To begin we first edit our gdbCfg file. From the code, we can see that we first read in 6 numbers. It is clearly the most compelling and fun for the, students, and the easiest for the instructor to grade. You can tell, makebomb.pl to use a specific variant by using the "-p" option. In memory there is a 16 element array of the numbers 0-15. This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. The answer is that the first input had to be 1. A string that could be the final string outputted when you solve stage 6 is 'Congratulations! On whose turn does the fright from a terror dive end? Keep going! Ok, let's get right to it and dig into the <phase_5> code: So, what have we got here? We can inspect its structure directly using gdb. This file is created by the report daemon, 4.4.4. Contribute to hengyingchou/CSE351 development by creating an account on GitHub. can be started from initrc scripts at boot time. Phase 4: recursive calls and the stack discipline. solution to each bomb is available to the instructor. secret_phase !!! phase_5 Assignment #3: Bomb Lab (due on Tue, Feb 21, 2023 by 11:59pm) Introduction. First, interesting sections/function names: ordered by the total number of accrued points. The first argument must be less than 7, right? A note to the reader: For explanation on how to set up the lab environment see the "Introduction" section of the post. Please feel free to fork or star this repo if you find it helpful!***. Entering this string defuses phase_1. I dereference the string pointed to by %rdi using x/s $rdi and see that the string pointed to is 'blah'. This question is based on the same project as the other Binary Bomb Phase 6 questions (most likely will be related links), but for some reason I can't find the nodes themselves, to check their incr. and/or the string 'The bomb has blown up.' node3 If you type the correct string, then the phase is defused and the bomb proceeds to the next phase. As the students work on their bombs, each, explosion and defusion is streamed back to the server, where the, current results for each bomb are displayed on a Web "scoreboard.". frequency is a configuration variable in Bomblab.pm. CMU Bomb Lab with Radare2 Phase 6 | by Mark Higgins - Medium To begin, let's take a look at the <phase_1> function in our objdump file: Since we know the final value is 6 letters/numbers, we know 72/6 = 12. What differentiates living as mere roommates from living in a marriage-like relationship? Did the Golden Gate Bridge 'flatten' under the weight of 300,000 people in 1987? This post walks through the first 3 phases of the lab. This part is a little bit trickier. The key is that each time you enter into the next element in the array there is a counter that increments. Explosion and, diffusions from bombs whose LabIDs are different from the current. c = 1 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!. A binary bomb is a program that consists of a sequence of six phases. The Hardware/Software Interface - UWA @ Coursera. initialize_bomb 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. You signed in with another tab or window. Curses, you've found the secret phase! We can find the latter numbers from the loop structure. sig_handler Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. You signed in with another tab or window. Here is Phase 5. In this version of the lab, you build your own quiet bombs manually, and then hand them out to the students. We can see that the last line shouldn't be contained in this switch structure, while the first four should be. Binary-Bomb/phase2a.c at master lukeknowles/Binary-Bomb - Github Also note that the binary follow the AT&T standard so instruction operations are reversed (e.g. Well Binary Bomb Lab :: Phase 4 - Zach Alexander You will only need, to modify or inspect a few variables in Section 1 of this file. 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. Next, as we scan through each operation, we see that a register is being . You can enter any string, but I used TEST. 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, --------------------------------------------------------------------------------. Assignment #3: Bomb Lab - CS356 Introduction to Computer Systems From the above comments, we deduce that we want to input two space-separated integers. Lets use blah again as out input for phase_2. Use Git or checkout with SVN using the web URL. correctly, else you and your students won't be able to run your bombs. 'But finding it and solving it are quite different' At the . I then continue to run the program until I am prompted for a phrase to input. fun7 ??? When you fail a phase, and the bomb goes off, you probably get the string 'BOOM!!!' For, example, "-p abacba" will use variant "a" for phase 1, variant "b" for. This command lists out all the values that each of the registers hold. Learn more. GDB then stopped at the break before entering into the phase_1 function call. How about the next one? You will get full credit for defusing phases 2 and 3 with less than 30 explosions. @cinos hi, I had same problem, I couldn't understand, I must have ecx 15 too, but I couldn't figure it out. Can you help me please? A tag already exists with the provided branch name. Contribute to xmpf/cse351 development by creating an account on GitHub. Ok, lets get right to it and dig into the code: So, what have we got here? b = 6 In the "offline" version, the. 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. initialize_bomb_solve Check to see if the incremented character pointer is not null terminated. The bomb explodes if the number calculated by this function does not equal 49. Next, as we scan through each operation, we see that a register is being incremented at , followed by a jump-less-than statement right afterwards that takes us back up to . which to blow yourself up. Help with Binary Bomb Lab Phase 6 : r/learnprogramming - Reddit !", deducting points from your problem set grade, and then terminating. 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. I have given a detailed explanation for phase_5 here: https://techiekarthik.hashnode.dev/cmu-bomblab-walkthrough?t=1676391915473#heading-phase-5. sign in If nothing happens, download Xcode and try again. read_six_numbers() - Checks that the user inputed at least 6 numbers and if less than 6 numbers then detonate the bomb. Are you sure you want to create this branch? CSAPP-Labs/README-bomblab at master - Github Maybe function names or labels? To see the format of how we enter the six numbers, lets set a breakpoint at read_six_numbers. Changing the second input does not affect the ecx. Each binary bomb is a program, running a sequence of phases. The students work on defusing, their bombs offline (i.e., independently of any autograding service), and then handin their solution files to you, each of which you grade, You can use the makebomb.pl script to build your own bombs. mov a b moves data from a to b as opposed to b to a). If so, put zero in %eax and return. Unexpected uint64 behaviour 0xFFFF'FFFF'FFFF'FFFF - 1 = 0? Become familiar with Linux VM and Linux command-line, Use and navigate through gdb debugger to examine memory and registers, view assembly code, and set breakpoints within the gdb debugger, Read and understand low level assembly code. 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. 1) We have to find that number 'q' which will cause 12 (twelve) iterations. to use Codespaces. Solve a total of 6 phases to defuse the bomb. Work fast with our official CLI. Segmentation fault in attack lab phase5. You don't need to understand any of this to. How about the next one? Is there any extra credit for solving the secret phase. You signed in with another tab or window. This command lists all the current breakpoints as well as how many times each breakpoint has been hit on the current run. You have 6 phases with which to blow yourself up. But finding it and solving it are quite different I'll paste the code here. If nothing happens, download GitHub Desktop and try again. Now lets take a quick look at the disassebly to see what variables are being used. While layout asm is helpful, also helpful to view the complete disassembled binary. Link to Bomb Lab Instructions (pdf) in GitHub Repository Find centralized, trusted content and collaborate around the technologies you use most. A tag already exists with the provided branch name. The answer is that the first input had to be 1. I cannot describe the question better . read_six_numbers There is also a test that the first user inputed number is less than or equal to 14. In order to determine the comparisons used, it will be useful to look up or know Jumps Based on Signed Comparisons. For lab: defuse phase 1. CMU Bomb Lab with Radare2 Phase 1 | by Mark Higgins - Medium The variable being used in this comparison is $eax. 0000000000401062 <phase_5>: 401062: 53 push % rbx 401063: 48 83 ec 20 sub $ 0x20, % rsp 401067: 48 89 fb mov % rdi, % rbx 40106a: . I see the output 'Phase 1 defused. What are the advantages of running a power tool on 240 V vs 120 V? You will have to run through the reverse engineering process, but there won't be much in the way of complicated assembly to decipher or tricky mental hoops to jump through. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. This series will focus on CMU's Binary Bomb challenge. string_length() - This function first checks to see that the passed character pointer in %rdi is not null terminated. 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." The autograding service consists of four user-level programs that run, - Request Server (bomblab-requestd.pl). 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. So we can plug in 6 d characters and get a valid comparison! The goal for the students is to defuse as many phases as possible. The idea is to understand what each, assembly statement does, and then use this knowledge to infer the, defusing string. Bomb Lab Write-up. 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 1: There are two main ways of getting the answer. Are you sure you want to create this branch? PHASE 3. From this, we can deduce that the input for phase_2 should be 1 2 4 8 16 32. For more information, you can refer to this document, which gives a handy tutorial on the phase 6. @Jester so I looked at your reply to another question which is extremely similar to my question, actually the same exact question. Could there be a randomization of stages or two planned routes through the bomb? Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. If nothing happens, download Xcode and try again. phase_4 From phase_4, we call the four arguments of func4 to be a, b(known, 0), c(known, 14), d(known, 0). makoshark.ics.cs.cmu.edu, Dunno, lets just get a static printout of the disassembled code and see what comes out. Raw Blame. we use, and get the following file (not the full code), We enter gdb, set a breakpoint at the phase 1. 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). There was a bunch of manipulation of stack space but there was nothing in the stack at that location and so it is likely a bunch of leg work. Next there is pattern that must be applied to the first 6 numbers. You have 6 phases with strings_not_equal() - This function implements the test of equality between the user inputed string and the pass-phrase for phase_1 of the bomb challenge. Once we enter the function, we can check the registers that store the first two inputs: $rdi and $rsi. ", Notifying Bomb: A bomb can be compiled with a NOTIFY option that, causes the bomb to send a message each time the student explodes or, defuses a phase. 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." The bomb is defused . First bomb lab is a Reverse Engineering challenge, you have to read its assembly to find the message that . Each, variable is preceded by a descriptive comment. Using layout asm, we can see the assembly code as we step through the program. 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. You've defused the secret stage! string_length Enter disas and you will get a chunk of assembly for the function phase_1 which we put our breakpoint at. any particular student, is quiet, and hence can run on any host. Thanks for contributing an answer to Stack Overflow! There are two hard coded variables that are then initialized and they, as well as the first user inputed value, are passed to func4. Could this mean alternative endings? p # Change print mode in Visual/Graph mode. Ultimately to pass this test all you need to do is input any string of 46 characters in length that does not start with a zero. Looks like it wants 2 numbers and a character this time. At the onset of the program you get the string 'Welcome to my fiendish little bomb. 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. Then enter this command. 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. ", Quiet Bomb: If compiled with the NONOTIFY option, then the bomb, doesn't send any messages when it explodes or is defused. I don't want to run the program/"pull the pin" on the bomb by running it, so this tells me that there are likely 6 stages to the bomb. 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. What was the actual cockpit layout and crew of the Mi-24A? There are 6 levels in the bomb and our task is to diffuse it. invalid_phase I'm guessing that this function will likely compare the string that I inputed to some string stored in memory somewhere. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. 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. If the function succeeds, it follows the green arrow on the right to the third box. You've defused the secret stage!'. phase_6 Moreover, it's obvious that the second one must be zero being aware of the line, So the problem becomes easier. 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. Each element in the array has an empty element directly adjacent to it. Here are the directions for offering both versions of the lab. Try this one. You signed in with another tab or window. Learn more about bidirectional Unicode characters. Contribute to xmpf/cse351 development by creating an account on GitHub. Let me know if you have any questions in the comments. However, you do need to handle recursion actually. phase_defused Load the binary, perform analysis, seek to Phase 6, and have a look at your task. In this write-up, I will show you how i solve bomb lab challenge. This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository. 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". I choose the first argument as 1 and then the second one should be 311. Are you sure you want to create this branch? Try this . 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. No description, website, or topics provided. Do this when you're ready for the lab to go "live" to, Resetting is also useful while you're preparing the lab. Have a nice day! I found various strings of interest. f7 ff ff callq 400bf0 <__isoc99_sscanf@plt>, : e8 a1 ff ff ff callq 40143a , fc ff ff callq 400bf0 <__isoc99_sscanf@plt>, : e8 c7 fb ff ff callq 400bf0 <__isoc99_sscanf@plt>, fa ff ff callq 400b30 <__stack_chk_fail@plt>. Lets use that address in memory and see what it contains as a string. This number was 115. phase_6() - This function does a few initial checks on the numbers inputed by the user. The LabID must not have any spaces. From this, we can see that the input format of read_six_numbers should be 6 space-separated integers. 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). At each iteration, we check to see that the current value is double the previous value. We can get the full assembly code using an object dump: objdump -d path/to/binary > temp.txt. Each phase has a password/key that is solved through the hints found within the assembly code. - Main daemon (bomblab.pl). A Mad Programmer got really mad and created a slew of binary bombs. So my understanding is that the first input is the starting point of the array, so it should be limited to between 0 and 14, and the second input is the sum of all the values that I visited starting from array[first input]. 0,1,2,3,4,5,6,7,8,9,10,11,12,13,14 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. As its currently written, your answer is unclear. Q. Actually in this part, the answer isn't unique. The dumb way is to simply input all characters from a-z into the cypher and create a mapping table. cse351/solution-explanation-of-phase-5.text at master - Github Keep going! Content Discovery initiative April 13 update: Related questions using a Review our technical responses for the 2023 Developer Survey. phase_5 You've defused the bomb!'. Bomb_Lab/Analysis.md at master MarkHyphen/Bomb_Lab GitHub CurryTang/bomb_lab_solution - Github Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior.
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