The flags-faking approach
Well, i decided to write this little essay for everyone (especially
newbies) who does not like to spend a lot of time trying to decypher
lines and lines of (meaningless?) code inside too many protection
schemes.
For example, have u ever found a serial number protected program which
u were not able to crack? I bet you have! You change a lot of bytes,
and yet it still sayd "Unregistered" and the "only for registered
users" options were still disabled.
On the other hand, did the following ever happen to you? A crippled
program with some options disabled and u DO NOT FIGURE how to enable
them? Well, go to the nearest tobacconist, buy a cool box of Marlboro
Lights (or the red ones, if you prefer), choose a rainy day (the best
for cracking purposes), sit in front of your PC and load this essay in
your favourite text-editor (i use old, good dos EDIT). By the way, i
hope you'll be able to read it, coz i dunno if the +HCU will really be
interested on this piece of text.... in fact it doesn't describe any
new protection scheme, it describes merely a different approach on
cracking a lot of programs.
Ok, let's start!
I will take as example a program called "HyperCam" v1.19, sort of an
AVI recorder of what happens on your screen... really good, especially
if u want to create an animated "cracking essay" for your new brand
cool target :-)
To get it go to www.hyperionics.com - HYPERCAM.ZIP - 251819 bytes (i'm
not really sure of the ZIP name, i found it on a CD. But I believe it
should be right)
Well, it's nothing new from the point of view of the protection
scheme, as I said... the only thing to notice is that it uses a very
very nasty key creation algorithm, maybe not understandable by most
newbie-crackers. Also, it stores the registration infos in a file
called HYPERCAM.LIC, so it needs quite a lot of work to crack it.
Ok, but this time we don't want to crack it with the usual "BMSG xxxx
WM_COMMAND" no?
We want to try something new! Light your cigarettes, fire your SoftICE
and install a good disassembler (i use now WDasm 8 <- thanx a lot to
Frog's Print for cracking it! very good work!).
The "protection" consist, basically, in the following scheme:
1) It displays a nag screen at the beginning
2) It adds a boring "HyperCam Unregistered" to all your nice AVI
creations
So, let's begin examining the "Unregistered Hypercam" add-on to the
AVIs, i.e. the nagstring:
Since we want to crack it without really "registering" it, we have to
take care of the flags that the program controls in order to know if
it's registered or not.
Usually, a program will store in a location a "00" if unregistered
(=FALSE) and a "01" if it's registered (=TRUE)... that's most of the
times NOT a protectionist choice, that's the overbloated programming
language doing it whithout ever letting them to know that this happens
:-)
We have to find this "holy" location. How? In this way:
1) Load up WDasm and disassemble HYPERCAM.EXE, save the *.alf. (be
sure to use the cracked one by FrogPrint!! If you use the demo one u
will not be able to examine the textfile at leisure inside your
wordprocessor!)
2) Search the nagstring it adds to all your AVIs: "Unregistered
Hypercam" YEAH!!!! FOUND IT! Examine this piece of code: (don't care
about my comments now, yu'll look at them after)
* Referenced by a Jump at Address :00401464(C)
|
:0040151C A1C0A34300 mov eax, [0043A3C0] *** < Now is "0"
:00401521 85C0 test eax, eax < If "0"
:00401523 740F je 00401534 *** < You suck!
:00401525 8B0D045E4300 mov ecx, [00435E04] < Checks again
:0040152B A1C0504300 mov eax, [004350C0] < with another flag
:00401530 3BC8 cmp ecx, eax *** < Final Check
:00401532 7418 je 0040154C < Equal? BRAVO=!!
Here we see that if the TEXT EAX,EAX fails at :401521 it will jump to
401534 Hmmm..... maybe DS:43A3C0 is the holy location where our flag
is stored? YES!!!!
* Referenced by a Jump at Address :00401523(C)
|
:00401534 8B1534A14300 mov edx, [0043A134] < not equal ?
:0040153A 6A15 push 00000015 < NISBA! (italian)
* Possible StringData Ref from Data Obj ->"Unregistered HyperCam"
|
:0040153C 68D0504300 push 004350D0 < the Unregistered
:00401541 6A00 push 00000000 < string is added
:00401543 6A00 push 00000000 < to your AVIs
:00401545 52 push edx
(lines tagged with a "***" will be the targets of our crack)
We found something interesting nah? Well, fire your ice (eh... i mean
Winice!), run the program and set a BPX which let us return the
debugger after doing something.... for example, i often use
KERNEL!HMEMCPY and choose an option in which i can enter some
strings.... but it's only an example, you could do it in a lot of
other ways.... Well,
:BPX KERNEL!HMEMCPY
* CTRL-D and select now an option in which you can enter some text (for
example, the "License" option). After entering, you will land in
Winice again
* Now hit F12 (trace-back) until you reach the code of HYPERCAM Remember
to remove first the KERNEL!HMEMCPY breakpoint!
* Reached? ok, search now in this segment the first bytes of our code
for me it is 22f, so :
:S 22f:0 lffffffff A1 C0 A3 43 00 85 C0 74 0F 8B
if you don't find it, it's simply bcoz maybe that piece of code isn't
loaded in memory yet, it is not yet "pinpointed". So, choose the "AVI
record" option and record something. Then retry and you'll find it.
* Set a BPX now at address you found these bytes in (the beginning of
the code showed before). For me, it is 22f:1ef91c, so :
:BPX 22F:1EF91C
* Ok, now we have set the breakpoint, hoping the best when we reload it
and try to create an avi (or even when the program is restarted, we
don't know now if it will work or not) it should break inside
softice... TRY!
* Now examine the comments in my code, and u should see that the flag
which control all is located at DS:43A3C0. Infact if the 2 checks
fails, the PUSH 004350D0 will save in stack the "Unregistered
Hypercam" string (you can see it by dumping memory D 4350D0 as soon as
you reach the push).
Well, now we know where the flag is... can we suppose that it controls
the initial nagscreen as well? yes of course! :)
Remove all the BPXs, set a new BPM DS:43A3C0 and restart the program!
Now we can see what happens to that "flag" location since the
beginning... You will land in softice 2 times, and after the 2nd time
the nagscreen will appear. So, what does this mean? Easy: the first
time softice pops up inside a piece of code which resets the flags,
the second time (our target) when the programs checks it. But look:
2nd popup:
:00404958 8BCD mov ecx, ebp
:0040495A E83C610200 call 0042AA9B
:0040495F 39BD48010000 cmp [ebp+00000148], edi < you will land here
:00404965 750D jne 00404974 < if not equal jump
:00404967 6AFF push FFFFFFFF < if not.....
:00404969 57 push edi < after some calls
:0040496A 688B000000 push 0000008B < the nag pops up!
:0040496F E886270200 call 004270FA
as u have noticed, EBP+148 is our "flag" location : 43A3C0 !!!
We are finished now!
Change .CMP [EBP+148],EDI with .MOVE BYTE PTR [EBP+148],1 < move always 1
.JNE 404974 .JMP 404974 < in our flag
Back to 401530, change also the JE 40154C to JMP 40154C to fool
completely the protection scheme.
Note that you have to change all of these, 'coz only removing the nag
or the string doesn't work. You can check this yourself examining the
code....
Ah.... a little side effects of this kind of approach *MAY BE* that
the program still say it isn't registered... even if all the options
are now cracked and enabled and even if the nag screens has been
removed.
This is what happens in HyperCam... but could happen in other programs
too ('bcoz obviously you don't register them normally, whit this
approach you don't enter any name/serial, you only fool the program to
*THINK* it's registered...). But who cares? The main thing is to have
a fully working version nah?
Well, i hope this little piece of txt could help you... it is often
easier and faster to handle (read crack) the flags than trying to
bypass the "real" number check or whatever the protection scheme
does... also you can apply this approach to nearly every kind of
protection... the main steps you should follow are:
1) Search references to the nag/unregistered/ecc. things in the code
2) Correctly identify the flags
3) BPM their locations and examine the code which refers to them.
4) Modify them to let the program think it's registered/deprotected.
CIAO!
by [>Xoanon<]/PiNNACLE 1997