Question

Binary Bomb Phase 3

Asked by: purewin

I'm working on phase three of the bomb and I think I have a general idea on what kind of input I need was wondering if someone could verify.

It looks like I need to pass two inputs and the inputs can vary. The first input would be stored at
0x08048cd7 <phase_3+6>: lea    -0x8(%ebp),%eax
stored at (ebp-8)

then the second input would be stored at
0x08048cde <phase_3+13>:        lea    -0x4(%ebp),%eax
stored at (ebp-4)

then if input 2 at (ebp-4) <= 7
switch(*(ebp-4))
which switches to one of the statements depending on what the value of *(ebp-4) is.
which would then set the value of eax depending on the statement switched to.
which would then jump to the memory location referenced in the switch case which then performs an operation on eax and sets eax equal to the result.
then if *(ebp - 4) > 5 or eax != *(ebp - 8)
bomb_explode is called
otherwise phase is diffused

Am i interpreting this correctly?

Dump of assembler code for function phase_3:
0x08048cd1 <phase_3+0>: push   %ebp
0x08048cd2 <phase_3+1>: mov    %esp,%ebp
0x08048cd4 <phase_3+3>: sub    $0x28,%esp
0x08048cd7 <phase_3+6>: lea    -0x8(%ebp),%eax
0x08048cda <phase_3+9>: mov    %eax,0xc(%esp)
0x08048cde <phase_3+13>:        lea    -0x4(%ebp),%eax
0x08048ce1 <phase_3+16>:        mov    %eax,0x8(%esp)
0x08048ce5 <phase_3+20>:        movl   $0x80497bb,0x4(%esp)
0x08048ced <phase_3+28>:        mov    0x8(%ebp),%eax
0x08048cf0 <phase_3+31>:        mov    %eax,(%esp)
0x08048cf3 <phase_3+34>:        call   0x8048828 <sscanf@plt>
0x08048cf8 <phase_3+39>:        cmp    $0x1,%eax
0x08048cfb <phase_3+42>:        jg     0x8048d02 <phase_3+49>
0x08048cfd <phase_3+44>:        call   0x8048f2c <explode_bomb>
0x08048d02 <phase_3+49>:        cmpl   $0x7,-0x4(%ebp)
0x08048d06 <phase_3+53>:        ja     0x8048d73 <phase_3+162>
0x08048d08 <phase_3+55>:        mov    -0x4(%ebp),%eax
0x08048d0b <phase_3+58>:        jmp    *0x804974c(,%eax,4)
0x08048d12 <phase_3+65>:        mov    $0x0,%eax
0x08048d17 <phase_3+70>:        jmp    0x8048d6c <phase_3+155>
0x08048d19 <phase_3+72>:        mov    $0x0,%eax
0x08048d1e <phase_3+77>:        xchg   %ax,%ax
0x08048d20 <phase_3+79>:        jmp    0x8048d67 <phase_3+150>
0x08048d22 <phase_3+81>:        mov    $0x0,%eax
0x08048d27 <phase_3+86>:        jmp    0x8048d62 <phase_3+145>
0x08048d29 <phase_3+88>:        mov    $0x0,%eax
0x08048d2e <phase_3+93>:        xchg   %ax,%ax
0x08048d30 <phase_3+95>:        jmp    0x8048d5d <phase_3+140>
0x08048d32 <phase_3+97>:        mov    $0x0,%eax
0x08048d37 <phase_3+102>:       jmp    0x8048d58 <phase_3+135>
0x08048d39 <phase_3+104>:       mov    $0x0,%eax
0x08048d3e <phase_3+109>:       xchg   %ax,%ax
0x08048d40 <phase_3+111>:       jmp    0x8048d53 <phase_3+130>
0x08048d42 <phase_3+113>:       mov    $0x6a,%eax
0x08048d47 <phase_3+118>:       jmp    0x8048d4e <phase_3+125>
0x08048d49 <phase_3+120>:       mov    $0x0,%eax
0x08048d4e <phase_3+125>:       sub    $0x363,%eax
0x08048d53 <phase_3+130>:       add    $0x396,%eax
0x08048d58 <phase_3+135>:       sub    $0x39d,%eax
0x08048d5d <phase_3+140>:       add    $0x1d2,%eax
0x08048d62 <phase_3+145>:       sub    $0x2ed,%eax
0x08048d67 <phase_3+150>:       add    $0x2ed,%eax
0x08048d6c <phase_3+155>:       sub    $0x331,%eax
0x08048d71 <phase_3+160>:       jmp    0x8048d7d <phase_3+172>
0x08048d73 <phase_3+162>:       call   0x8048f2c <explode_bomb>
---Type <return> to continue, or q <return> to quit---
0x08048d78 <phase_3+167>:       mov    $0x0,%eax
0x08048d7d <phase_3+172>:       cmpl   $0x5,-0x4(%ebp)
0x08048d81 <phase_3+176>:       jg     0x8048d88 <phase_3+183>
0x08048d83 <phase_3+178>:       cmp    -0x8(%ebp),%eax
0x08048d86 <phase_3+181>:       je     0x8048d8d <phase_3+188>
0x08048d88 <phase_3+183>:       call   0x8048f2c <explode_bomb>
0x08048d8d <phase_3+188>:       leave  
0x08048d8e <phase_3+189>:       xchg   %ax,%ax
0x08048d90 <phase_3+191>:       ret    
End of assembler dump.

                                  
1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
15:
16:
17:
18:
19:
20:
21:
22:
23:
24:
25:
26:
27:
28:
29:
30:
31:
32:
33:
34:
35:
36:
37:
38:
39:
40:
41:
42:
43:
44:
45:
46:
47:
48:
49:
50:
51:
52:
53:
54:
55:
56:
57:

Select allOpen in new window

This Question has been solved and asker verified All Experts Exchange premium technology solutions are available to subscription members.

Subscribe now for full access to Experts Exchange and get

Instant Access to this Solution

  • Plus...
  • 30 Day FREE access, no risk, no obligation
  • Collaborate with the world's top tech experts
  • Unlimited access to our exclusive solution database
  • Never be left without tech help again

Subscribe Now

Asked On
2009-10-19 at 14:23:01ID24825166
Topics

Assembly Programming Language

,

C Programming Language

,

Algorithms

Participating Experts
2
Points
500
Comments
6

Trusted by hundreds of thousands everyday for fast, accurate and reliable tech support.

  • "The time we save is the biggest benefit of Experts Exchange to Warner Bros. What could take multiple guys 2 hours or more each to find is accessed in around 15 minutes on Experts Exchange." Mike Kapnisakis, Warner Bros.
  • "Our team likes having a resource that is more secure than just using Google and most experts using this service really know their stuff. It's nice to look here first versus using Google." Dayna Sellner, Lockheed Martin
  • "Anytime that I've been stumped with a problem, 9 out of 10 times Experts Exchange has either the accepted solution or an open discussion of the potential solution to the problem." Kenny Red, eBay Inc.

See what Experts Exchange can do for you.

Got a question?

We've got the answer.

Experts Exchange has been collecting answers to technology questions since 1996…3 million and counting! If you have a question, chances are we already have your answer.

Screenshot of Experts Exchange Knowledgebase

Need individual assistance?

Our experts are ready to help.

If you can't find the exact answer you're looking for, ask our exclusive community of 50,000 experts. You’ll get a personalized answer from a trusted professional.

Screenshot of Experts Exchange Knowledgebase

Want to learn from the best?

Read articles from industry experts.

Thousands of free tech tips, tricks, how-to’s and tutorials are available in our peer reviewed articles section. See for yourself how smart our experts are, no login required.

Screenshot of an Article

Working on a long term project?

Store your work and research.

Save solutions to your questions, answers you’ve discovered through searching plus helpful articles in your personal knowledgebase for easy future access.

Screenshot of Experts Exchange Knowledgebase

Access the answers to your technology questions today.

Subscribe Now

30-day free trial. Register in 60 seconds.

What Makes Experts Exchange Unique?

Members of the expert community talk about why the experience at Experts Exchange is different than what you will find anywhere else.

Trusted by the world's most respected brands.

image of each brand's logo

Faithfully serving IT professionals since 1996.

Experts Exchange Logo

Try it out and discover for yourself.

Subscribe Now

30-day free trial. Register in 60 seconds.

Related Solutions

  1. Binary Bomb Phase 2 Problem
    I am working on this binary bomb for class, and am stuck at phase_2. Here is the disassembled code with comments I made. I also included read_six_numbers as I think that is where the answer is. Been looking in eax and the address it holds everytime it is pushed on the stac...
  2. Binary Bomb Phase 4
    Alright i'm on phase 4 of the binary bomb problem, have analyzed the assembly and this is what I have. Dump of assembler code for function phase_4: 0x08048c2c <phase_4+0>: push %ebp 0x08048c2d <phase_4+1>: mov %esp,%ebp 0x08048c2f <phase_4+3>: sub $...
  3. Binary Bomb Phase 5
    Infinity08 your comments are really helping me understand this better. Could you please let me know if what I wrote is going on here is correct. I can't seem to figure out exactly what this wants, except know it wants a string that is length 6. Thanks again Dump of assemb...
  4. Binary Bomb Final Phase
    Alright, on the last phase of the binary bomb. I have the code commented and just wanted to know if what I think is happening really is. So far I just think it is a bunch of nested loops and that the input will be 5 or less numbers. Alright any feedback would be very appre...
  5. Binary Bomb Phase 2
    Hello, I am needing help with the Binary Bomb Assignment. I have completed phase one by using the x /s command. I am now stuck on phase 2. From what I understand, the the function call read_six_numbers will take in my entered string (six numbers with spaces) and scanf will ...
  6. diffusing a bomb
    hey, I need to diffuse a "bomb", I was hoping I could get some advice, I have a vague idea of what I need to do. 080519c4 <phase_1>: 80519c4: 55 push %ebp 80519c5: 89 e5 mov %esp,%ebp 80519c7: 83 ec 10 s...

Free Tech Articles

  1. WARNING: 5 Reasons why you should NEVER fix a computer for free.
    It is in our nature to love the puzzle. We are obsessed. The lot of us. We love puzzles. We love the challenge. We thrive on finding the answer. We hate disarray. It bothers us deep in our soul. W...
  2. SCCM OSD Basic troubleshooting
    SCCM 2007 OSD is a fantastic way to deploy operating systems, however, like most things SCCM issues can sometimes be difficult to resolve due to the sheer volume of logs to sift through and the dispe...
  3. Migrate Small Business Server 2003 to Exchange 2010 and Windows 2008 R2
    This guide is intended to provide step by step instructions on how to migrate from Small Business Server 2003 to Windows 2008 R2 with Exchange 2010. For this migration to work you will need the fo...
  4. Create a Win7 Gadget
    This article shows you how to create a simple "Gadget" -- a sort of mini-application supported by Windows 7 and Vista. Gadgets can be dropped anywhere on the desktop to provide instant information, ...
  5. Outlook continually prompting for username and password
    There have been a lot of questions recently regarding Outlook prompting for a username and password whilst using Exchange 2007. There are a few reasons why this would happen and I will try to cover t...
  6. Backup Exchange 2010 Information Store using Windows Backup
    There seems to be quite a lot of confusion around the ability to backup Exchange 2010 using the built in Windows Backup feature. This stems from the omission of this feature prior to Exchange 2007 s...

Cloud Class Webinars

  1. Avoiding Bugs in Microsoft Access
    Alison Balter takes and in-depth look at avoiding bugs in Access. In this webinar you will learn about using the immediate window to debug your applications, invoking the debugger, using breakpoints to troubleshoot, stepping through code, setting the next statement to execute, ...
  2. Top 10 Best New Features in Visio 2010
    Scott Helmers gives live demonstrations of the top 10 new features in Visio 2010. This webinar will teach you how to create compelling diagrams by adding shapes to the page with a single click, linking the shapes in a diagram to data in Excel (or SQL Server, or SharePoint), ...
  3. IT Consultant Business Secrets Revealed
    Michael Munger, Experts Exchange tech pro and IT consultant, pulls back the curtain on his very successful businesses and answers question on every IT consultant and business owner should know about. He shares secrets on what he did to solve the 5 most common problems in IT, ...
  4. Disaster Recovery and Business Continuity
    Quest CTO, Mike Billon, gives an overview of the steps involved in building a dunamic disaster recovery plan. Through case studies and an examination of software/hardware tooles for monitoring and testing, you'll gain a better understandin of where you are, where you want ...
  5. Organize Your Visio Diagrams with Containers and Lists
    Scott Helmers uses cross functional flowcharts, wireframe diagrams, data graphic legends and seating charts to teach you: how to ustilize all three new structured diagram components in Visio 2010, the best practices for organizeing shapes in previous version of Visio, how to organize ...
  6. How to Us Objects, Properties, Events and Methods in Microsoft Access
    Alison Dalter gives an in-depbth look at objects, properties, events and methods in Microsoft Access. In this webinar you will learn about using the object browser, referring to objects, working with properties and methods, working with object variables, understanding the ...

Join the Community

Give a Little. Get a Lot.

Join the community of experts here and help other tech pros by answering question in your area of expertise. You can earn FREE access to all Experts Exchange's premium features and resources.

Join the Community

Answers

 

by: Infinity08Posted on 2009-10-19 at 15:28:47ID: 25609563

>> The first input would be stored at
>> 0x08048cd7 <phase_3+6>: lea    -0x8(%ebp),%eax
>> stored at (ebp-8)
>> 
>> then the second input would be stored at
>> 0x08048cde <phase_3+13>:        lea    -0x4(%ebp),%eax
>> stored at (ebp-4)

It's the other way around (the parameters to sscanf are pushed on the stack in reverse order), but those two addresses will indeed contain the two values read from the string by sscanf.

>> Am i interpreting this correctly?

The rest is pretty much what happens :) Now just put some actual values in your description of what happens, and figure out what the input needs to be ;)

 

by: purewinPosted on 2009-10-19 at 15:43:31ID: 25609632

so the two numbers i need to enter as input would be entered in reverse order? i.e. if input = 3 6
(ebp+8) = 6
(ebp+4) = 3

Also I've been looking at the conditionals and it seems (ebp - 4) has to be either 2,3, or 4 and then based on which value it is there would be a jump to one of these memory locations
if 2 jump to 0x08048d53
if 3 jump to 0x08048d58
if 4 jump to 0x08048d5d
then after performing a calculation at those locations set = eax
a conditional that if *(ebp-4) > 5 or eax != *(ebp-8) equals tru the bomb explodes otherwise diffused

that being said i could use 2,3 or 4 and then based on which i choose and where it jumps from on the conditional i would need to solve the calculation for the second user input?

Is the what is happening and upon doing so I would get the needed second value?

 

by: purewinPosted on 2009-10-19 at 17:00:46ID: 25609990

Also what does
0x08048d1e <phase_3+77>:        xchg   %ax,%ax
do? Never seen this before, not even in my textbook.

 

by: purewinPosted on 2009-10-19 at 17:58:36ID: 25610234

Phase 3 done. Watch how eax changes. :)

 

by: Infinity08Posted on 2009-10-19 at 22:37:02ID: 25611256

>> so the two numbers i need to enter as input would be entered in reverse order? i.e. if input = 3 6
>> (ebp+8) = 6
>> (ebp+4) = 3

They're not entered in reverse order. But the code is pushing them onto the stack in reverse order. You can use your debugger to see where both values are put.


>> Also what does
>> 0x08048d1e <phase_3+77>:        xchg   %ax,%ax
>> do? Never seen this before, not even in my textbook.

xchg is the exchange instruction. It swaps around the two arguments. ie. :

        xchg a, b

after this instruction, the a and b will have been swapped.


>> Phase 3 done. Watch how eax changes. :)

Great. You're moving along nicely now ;)

 

by: thehagmanPosted on 2009-10-20 at 12:23:45ID: 25617496

In other words, "xchg %ax,%ax" is just a fancy "nop" (occupies two bytes for code alignment, but executes faster than two nops)

20120131-EE-VQP-002

3 Ways to Join

30-Day Free Trial

The Experts

98% positive feedback on 31,087 answers since March 2000. angeliii is a Microsoft Most Valuable Professional for his work with MS SQL Server & Develoment.

He has also proven his knowledge of Visual Basic Programming, PHP Scripting and Oracle Databases.

The Experts

97% positive feedback on 10,752 answers since July 2000. lrmoore has more than 18 years experience in the networking industry.

The six-time Mircosoft MVPs specialties include firewalls, virtual private networking, and network management.

Testimonials

"...and excellent source for support... Kind of like having your very own IT dept." Electriciansnet

Testimonials

"I was apprehensive at signing up at first. However... it has already made my life as an IT administrator much easier." JaCrews

Testimonials

"WOW! You guys have great, active, and knowledgeable people on here." moore50

Business Clients

Business Clients

In the Press

"If you’ve got a question... Experts Exchange can supply an answer.”

In the Press

"...an invaluable aid for both IT professionals and those who require tech support."

In the Press

"where IT professionals provide quick answers on just about any topic"

Business Account Plans

Loading Advertisement...