What Time Does the Library Open?
A "Cinderella" protection for beginners
most stupid
Most stupid protection
02 December 1998
by Sojourner
Courtesy of Reverser's page of reverse engineering
slightly edited by reverser+
fra_00xx
981292
Sojourner
1000
P7
PC
A simple "Cinderella" protection, well explained, for beginners and gullible protectors alike.
There is a crack, a crack in everything That's how the light gets in
Rating
(x)Beginner ( )Intermediate ( )Advanced ( )Expert

"A useful essay for beginners to see a different perspective of the common time functions in order to reverse more fully a useful prog and to see a different kind of function called to impede us"

What Time Does the Library Open?

Written by Sojourner


Introduction

Originally I had been a Beta tester for this freely available program from ftp://ftp.mcneel.com/pub/rhino/rhino32.exe. Now ftp://ftp.mcneel.com/pub/1.00/demo. Go there and have a look around if you'r interested. I did. The "latest" demo is still there, along with models, plugs for 3DS Max, etc. How nice for us! Since I work on 3D projects I had a personal interest in this nice piece of software, and had grown to like its easy user interface and its capabilities.
Also, I suspected that my beta format would have been very close to the version 1.00 release that we were told would be shipping after the expiration... the "full" version would retail for only around $795. Thanks, but no thanks, there's no way I can pay such a sum for a 'full' version, when my own beta could work just the same.
Since the last beta had a "Cinderella protection" dated October 1998, and used a very bad protection scheme, I could have used it for the infinity just resetting my PC clock everytime I needed it... as I suspect most lusers around are doing. But, hey, after all I'm (beginning to be) a reverser! And I decided to have a look at the code!
Since this was only the second reversing I had tried, I was a little scared to tell the truth. After I had read Tristan's essay from 31 December 1997, and he encouraged "newbies, to try your hand," I was more encouraged and bold. Also I had read and "studied intensely" at least 30 of the other essays from the +HCU 'student essays' area. Additionally, I thought to myself, " If I can do this reverse, I'll have a nice useful tool to study. If not, well then I'll have at least learned something about code!" Time was running out and I didn't want to keep setting my clock time to run that program to suit its fancy. I put my gray cells to work.
A brief note: you will need at least close to 200 meg of free space on whatever drive you use to disassemble this with WDASM 89 or your time is wasted. The rhino_main.exe is what we'll be disassembling and it creates an 80 meg file to start! Enjoy.Take 20-30 minutes and go do something else while WDASM 89 does its thing. As always when you reverse, take good notes. It will save you hours of needless toil in the future. Get a good assembly and WinAPI reference also. If possible even a Win95,98 or NT programming book.They are invaluable.



Tools required
WDASM89, UltraEdit, Soft-Ice 3.2

Target's URL/FTP
Get Rhino Here!

Program History
This program started off as a beta nurbs modeler and is now in full production after about three years

Essay

Reversing Started:
There are two separate areas that will be involved in the successful reversing of this prog. Both involve time in some way. A note- I want to make sure you have already installed this program and are not trying to reverse the initial executable that needs to be unpacked first. We need to be at the same start point. Thanks :-)

Inside WDASM 89 you'll need to open up the "Import Functions" box and look for Kernel32 GetLocaltime. Why? Upon startup, Rhino is doing some checking with the local scene to see what time it is and then making comparisons with some predefined parameters, namely, 1998 (07CEh) and 11 (000Bh). See below in code. If everything is ok, you can stay. If not, well, you know what happens! Additionally, you could do a string search for "This beta version of Rhino has expired" and in this case you would be right where you needed to be. This is just because this protection is particularly stupid and doesn't always happen so easily, though.
* Reference To: KERNEL32.GetLocalTime, Ord:00F5h 
                                  | 
:00488AE9 FF15088D8C00            Call dword ptr [008C8D08] 
:00488AEF 66817C2404CE07          cmp word ptr [esp+04], 07CE <== Here and 
:00488AF6 7508                    jne 00488B0E 
:00488AF8 66837C24060B            cmp word ptr [esp+06], 000B <== Here 
:00488AFE 7D00                    jnl 00488B0E 
As you can see, these two compares above check local time against the "factory" authorized times. Both factory times are in hex. The first will jump you out if the year isn't exactly 1998 and the second will jump you out if the month isn't less than November. These come out of the WinAPI function for GetLocalTime. But wait. See below at 00488B00. There soon follows a ret which completes our local time function--IF everything is okay. If not you are sent to the 00488B0E expired nag and then out the door.
:00488B00 33C0                    xor eax, eax 
:00488B02 5B                      pop ebx 
:00488B03 83C410                  add esp, 00000010 
:00488B06 C3                      ret 
 
:00488B07 6A00                    push 00000000 

* Possible StringData Ref from Data Obj ->"Beta copy expired" 
                                  | 
:00488B09 6810C67F00              push 007FC610 

* Possible StringData Ref from Data Obj ->"This beta version of Rhino has " 
                                        ->"expired." 
                                  |
:00488B0E 68E8C47F00              push 007FC4E8 
:00488B13 6A00                    push 00000000 
So we must change some things to help us out. Change

:00488AF6 7508          jne 00488B0E     <== Here to EB08   jmp 00488B00   
                                   (be sure to get the right offset first) 
:00488AF8 66837C24060B  cmp word ptr [esp+06], 000B 
:00488AFE 7D00          jnl 00488B0E     <== Here to EB00   jmp 00488B00 
 
Now we get to stay no matter what time it is. Yippee! Case solved
Uh. Sorry. Not quite true!.
Go ahead and make these changes in WDASM 89 and let it run with your clock at different times. It will LOAD up perfectly and appear to function alright. Make these changes with your favorite hex editor permanent before going on. Now for the acid test. Set your clock ahead, to say, 2010, and run WDASM again with your "fixes." It will allow you to start up the program without that nasty nag screen to bother you. Also, it will not kick you out. So what's the problem you may ask. Remember the file we saved earlier? Go ahead and load it now. Have you loaded it? Good. Now modify it in some small way and save. Boom! Bamm! Bong! We're out the door again. What the heck happened? I thought we fixed that bugger! Well, I must admit, I agonized over this. Whenever you just touched the "Save" button you were history and fast! Originally, I thought it was due to the GetLocalTime function in some way and set appropriate breakpoints in WDASM to catch these. There are several by the way. I also could not catch the process that called the "Exit Process" function this time. I couldn't get any breakpoint "nibbles" here, so I decided to try another route to one of the functions that may check up on buttons and their status. Nada, not jack squat! I knew in my bones it had to be a check to a time function somewhere so on my next go round I fired up SoftIce3.2, loaded rhino_main.exe and set a breakpoint at GetLocalTime. (BPX GetLocalTime), Ctrl-D to get back to the running of the prog and immediately you get "bites." As a matter of fact those two points we just "fixed" earlier are checked. You did fix them in the hex editor didn't you? You may CTRL-D again to get back to your running prog and eventually you'll be at the correct screen to allow you to work. Load your file back in, that is, the one we made earlier in Rhino and do some slight modification to it and hit "Save" as before. Now this time SoftIce will catch a GetLocalTime function call and if you F-12, then F-10 awhile you will land up below. This is a WDASM 89 listing of the same since I didn't catch this in SoftIce. As you see there is a call to "Free Library" here. Who'd a thought? As you're F-10'ing in SoftIce down at 0041785E there is a comparison to a dword ptr [ebp+FFFFFF6C], eax. What the heck is all this crap? SoftIce shows you what's actually there. See my note below. Tricky fellows. Then just below there at 0041786A is another comparison. What are we comparing here?
* Reference To: KERNEL32.FreeLibrary, Ord:0098h
                                  |
:00417832 FF15A88C8C00            Call dword ptr [008C8CA8] 
:00417838 8B857CFFFFFF            mov eax, dword ptr [ebp+FFFFFF7C] 
:0041783E 25FFFF0000              and eax, 0000FFFF 
:00417843 898578FFFFFF            mov dword ptr [ebp+FFFFFF78], eax 
:00417849 33C0                    xor eax, eax 
:0041784B 668B857EFFFFFF          mov ax, word ptr [ebp+FFFFFF7E] 
:00417852 898564FFFFFF            mov dword ptr [ebp+FFFFFF64], eax 
:00417858 8B8578FFFFFF            mov eax, dword ptr [ebp+FFFFFF78] 
:0041785E 39856CFFFFFF            cmp dword ptr [ebp+FFFFFF6C], eax  
				[Here eax has the current year loaded from    ]
                                [GetLocalTime, whereas [ebp+FFFFFF6C] has 07C ]
                                [(1998) already loaded                        ]
:00417864 0F8516000000            jne 00417880 
:0041786A 8B8564FFFFFF            mov eax, dword ptr [ebp+FFFFFF64 
:00417870 3945F8                  cmp dword ptr [ebp-08], eax        
                                [Here eax has the current month loaded from   ]
                                [GetLocalTime, whereas [ebp-08] has 000B (11) ]
                                [already loaded                               ]
:00417873 0F8E07000000            jle 00417880 
:00417879 33C0                    xor eax, eax 
:0041787B E925000000              jmp 004178A5 
As seen below this current point (00417880) has two important jump points to it and they will both kick you out quickly The very ones we need to fix in order to be able to save our files any time we want to. I tried several different methods to fix this and the one that worked best was to simply (see above )use 6 nops at 00417864 and 6 nops at 00417873. The program then correctly places us at 004178A5 (see below) after xoring eax, as seen from above jump. Thereafter the program runs perfectly and forever. I used times from 1980 to 2095 without any hassle. Now go fix these in your hex editor and enjoy Rhino!
* Referenced by a Jump at Addresses: 
|
:00417880 C70508488C0000000000    mov dword ptr [008C4808], 00000000 
:0041788A E8514F0300              call 0044C7E0 
:0041788F A1844F8C00              mov eax, dword ptr [008C4F84] 
:00417894 50                      push eax 

* Reference To: USER32.DestroyWindow, Ord:008Ah 
                                  | 
:00417895 FF1544918C00            Call dword ptr [008C9144] 
:0041789B B801000000              mov eax, 00000001 
:004178A0 E900000000              jmp 004178A5 

* Referenced by a Jump at Addresses:
|:004177FD(U), :0041781F(U), :0041787B(U), :004178A0(U) | :004178A5 5F pop edi :004178A6 5E pop esi :004178A7 5B pop ebx :004178A8 C9 leave :004178A9 C3 ret

Your text, duh



Final Notes

You should know that nothing is ever easy, even if it looks like it is. It took hours of piddling around for me (a newbie) to come up with this info. Experience helps a lot as well as what +orc decribes as "zen", but experience is not everything, if you don't have some sound teachings. I can't thank enough everyone who has taken time to write their own essays. We need good teachers (and good tools, tools made by ourself). Keep up the good work! All of you! Research! Delve inside the code! Write! So that crackers and protectors alike can learn and evolve!
Future Requests: More to do with calls to outside .dlls! Also how about a REAL listing of the various ways to trap
functions, windows, messages, etc. in SoftIce which are more specific for reversers. Thanks! :-)



Ob Duh
I wont even bother explaining you that you should BUY this target program if you intend to use it for a longer period than the allowed one. Should you want to STEAL this software instead, you don't need to crack its protection scheme at all: you'll find it on most Warez sites, complete and already regged, farewell.

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