27 May 2015

Static Enigma Virtual Box unpacker, part 2

Here comes a new version. smile This time I added support for unpacking external packages. "External packages" are data files that can be loaded by Enigma Virtual Box and can contain both embedded files and registry entries.

I also made my unpacker 100% Unicode-aware - there should not be any more problems with non-english filenames. But I had to switch to Delphi 2009 compiler to do this, so there might be some unexpected bugs lurking around.

And, of course, lots of internal bugs had to be fixed. My code is not perfect, you know! wink

EnigmaVB Unpacker v0.30

Download link: Please get latest version from this post

P.S. Thanks to Manofwar for giving me few example files for development & testing!

25 May 2015

Blogging is hard

When I started this blog, I wanted to try and see what will happen. I thought that I have so many things to say and to write about. I still do. smile

But as I found out soon enough, making a decent-quality blog post takes hours. And I don't have that much free time. So, I had to choose between making half-assed posts with pretty kittens and lists of "Top-X things you don't really care about", or taking my time to write a proper post about something (technical) that I learned recently - at the expense of less frequent updates.

I chose to write less often. Currently I'm managing to make one proper post per week - and I really hope to keep it up that way. Of course, the more feedback I get, the more motivated I'd be to write. So, it's all in your hands.. wink

On a related subject, I added a simple captcha to the comment form. Looks like it's working really well to keep most of the spambots away. But if you encounter any problems with it, please let me know.

19 May 2015

Static linking of Bassmod in Delphi

BASS and BASSMOD are very well known freeware libraries for playing XM, IT, WAV and many more sound file formats. They are widely used in keygens and other apps. However, authors only distribute them in a DLL form, there is no LIB file or any other option for linking them statically.

Last week someone resurrected an old thread at Tuts4You and asked how to convert DLL to LIB and link it statically with Delphi. I gave poster the standard answer but he was still running in all sorts of issues. So, can it be done?

Then answer is - yes. But it's not easy.

Note - This article is written for good old Delphi 6/7/2007. Since Delphi XE2 the process should be easier as the linker was improved to use COFF OBJ files directly. However, I don't have those new Delphi versions, so I can't test the claims.

Steps to be taken

I'll make a list of all necessary steps first and then I'll discuss them in details.

  1. Unpack the DLL properly
  2. Convert DLL to LIB
  3. Extract OBJ files from LIB
  4. Convert COFF OBJ files to OMF OBJ files
  5. Make those OMF files usable by Delphi
  6. Write a wrapper unit that works around Delphi limitations

Unpack the DLL properly

First step sounds easy, right? It isn't.

The LIB provided in Tuts4you thread is badly unpacked. Sure, it can work when compiled with MASM. It can be made work with Delphi, but you'll need to hex-edit compiled EXE file first. The reason for this is extremely primitive Delphi compiler/linker. You have no control over PE section names or attributes. It relies on specific section names and always makes code section read-only. But the LIB from tuts4you uses one segment for both code and data and it must have read-write-execute characteristics. Ooops.

So, we need to unpack DLL ourselves using all the standard steps. PE packer is a very simple one, so you can easily find OEP, dump the file, load DLL at different imagebase, find the OEP and make a 2nd dump, use 2 dumps to fix the relocations using Relox and finally restore Import Table using Scylla or ImpRec. Nothing new here.

Once you've unpacked the DLL, you will have to detect section boundaries and create new PE section table. When you're at OEP of bass.dll, check the memory map in some process exploring tool. You'll see the sections and their characteristics nicely:
BASS memory map in PETools

Now use any PE editor to create appropriate PE section headers:
Section headers in CFF
To make Delphi happy, code section should be named _TEXT and data section should be named _DATA. All the sections you don't need in final OBJ file, should be named ".reloc", ".edata" or similar - Dll2lib will remove them automatically.

Convert DLL to LIB

Well, this step is easy. Use DLL2LIB (google "DLL.To.Lib.v1.42.Full.Retail-DLL2Lib" or get trial version from official site), leave all the default settings and press "Start convert".


Extract OBJ files from LIB

For next few steps you'll need objconv.exe by Agner Fog. It's better to download the latest version, as earlier versions didn't support extracting LIB files.

It's a simple command objconv.exe -lx bass.lib

Convert COFF OBJ files to OMF OBJ files

That's also simple. Just run objconv.exe -fomf bass.obj bass-omf.obj

Make those OMF files usable by Delphi

Delphi imposes quite a few limitations to OBJ file format. Some of them are documented, some of them aren't. So, it's better to rely on special tools made for this purpose, like omf2d.exe by EliCZ.

I'm sure that objconv.exe can do the same, but I'm too lazy to try to figure the right command line parameters. So, just run omd2f.exe bassmod-omf.obj bassmod-omf-d.obj

Note - omd2d.exe will mess up some decorated names from msvcrt.dll, like "??2@YAPAXI@Z". That's not a problem, we'll fix that in the wrapper unit.

Write a wrapper unit that works around Delphi limitations

This is also tough. And again the problems are caused by the primitive Delphi compiler/linker.

Delphi doesn't support direct API calls, all API calls will go through the thunk table. When you try to reference any external API from Delphi code, in reality you'll get address of the thunk code.

For the same reason in Delphi you can't access exported global variables from another DLL.

Unfortunately BASS/BASSMOD uses both direct API calls and global variables from msvcrt.dll. Little bit of clever hacking is required to work around that - you'll have to load msvcrt and other DLLs from unit initialization code and use GetProcAddress to get the required addresses.

So, the implementation part of the unit will look like this:

In addition to that we need to call the original DllMain function to make sure that BASS is initialized properly:

As a final touch, in the finalization part of unit we'll have to call DllMain again to make sure all resources are freed properly.

Putting it all together

I already outlined all the steps needed. Anyone with proper skills should be able to replicate them and make his/her own BASS unit.

For those who are lazy - here is the package with Delphi units+obj files + all the intermediate files + compiled projects from BASS/BASSMOD examples to show that it really works.

Have fun!

Useful links

Unpacking DLLs #1: Tutorial by Mr. eXodia
Unpacking DLLs #2: How to use Relox in few simple steps
Omf2d: https://www.mediafire.com/?hsksyjwnwlaw3zb

13 May 2015

Fixing choppy sound in Chrome within RDP connection

Some things and services are banned from work computers. Like your collection of MP3s. Or p2p-based television. Or access to Pandora. smile But everyone knows that music is a really great motivator! So, I decided to try a small trick - use RDP connection to my home PC and play my MP3s from home PC.

It turns out that playing MP3s in Winamp works great. However, playing Pandora radio or anything else in Chrome produced a very choppy sound and video framerate was around 3fps.. That's not great at all.

Quick Google search locates this 1.5-years old Chrome bug: Issue 310983: choppy sound playing videos within RDP session (not only Flash, also HTML5). As it happens quite often - it's reproduced by several people but nobody gives a flying fcuk about actually fixing it. So much for the open-source and quick fixes..

Lucky for me, there was a workaround suggested in the comments - install RDP 8.0 server and client.

Hmm, I haven't heard anything about RDP versoin 8.0. How is that possible?

Turns out, it comes by default on Windows 8.x but must be manually installed and explicitly enabled on Windows 7. It's one of those hidden treasures very few people know about!

So, on my home Win7 box I installed updates KB2574819, KB2592687 and restarted. Automatically received Security Update KB2965788 and got another restart. Made the necessary changes in group policy settings, and - you guessed right - yet another restart. Got locked out of my box because suddenly my username was not in "Remote Users" group, and I had to re-add it manually. Logged in and everything works as it should. Pandora sounds great, video is suddenly smooth and watchable and my work productivity goes... UP! smile

Happy happy joy joy!

Further reading

List of new features in RDP v8.0
Technical blog explaining technologies behind RDP v8.0 magic

11 May 2015

Improving Meltdown

More than 2 years ago I released Meltdown. It's a proof-of-concept tool that showed several security issues in Faronics DeepFreeze products. Faronics are infamous for their attempts to hide the issues, so I was really curious how it will work out.

Bugs in my code

First, a few bugs in my code surfaced. None of them were in the core components dealing with DeepFreeze, I had that part tested thoroughly. But I overlooked issues with UAC, possibility that Windows are not installed on drive C:\, empty passwords and other edge cases.

All in all, it was a good learning experience.

Requests for source code

The very first version of Meltdown came with a full source code and explanation of the vulnerabilities in Faronics products. Once I started fixing bugs, I released only the updated binary. Yet quite a few people kept asking for the updated source.

To be honest, I have no idea why. So far, I haven't seen a single tool that would be based on my source code, not even a straightforward rip with a changed name and copyrights. Weird..

Bug reports

People reported bugs. Big bugs, small bugs, non-bugs and everything in between.

Most bug reports came from arabic-speaking guys. Some of them even didn't bother to use Google Translate and wrote in their native language. No, I really don't speak Arabic, German, French or Indonesian.

Also, most bug reports came without any actionable information whatsoever. Just "It doesn't work". Well, that's not helpful at all! I really want to help you, but you must tell me more than that. In later versions, I added information to main window about detected OS, 32/64bits, detected DF version, etc, etc. And then I can just ask for a screenshot, it contains most of the info I need to replicate the issue.

It was a good learning experience again. I learned how to make my tools more user-proof.

Faronics response

For a year, there was none.

Then in June 2014 they released DeepFreeze Enterprise 8.11 where the issue was fixed. At least the changelog says so:

7936 Resolved a security issue that could result in the user accessing Deep Freeze without authorization.

Yeah, right.. In reality they just added yet-another-layer of xor-encryption and removed useful data from frzstate2k.exe. But the same data are still present in dfserv.exe.

Wow, that's what I call "resolving a security issue"! smile

In September 2014 they released DeepFreeze Standard 8.10 where the other vulnerability was fixed. However, there was no mention of anything like that in the changelog. From a quick glance, it looks like they finally got their code right and aren't sending xor-encrypted password from driver to usermode anymore.

What now?

I'm presenting you an updated version of Meltdown.

Meltdown v1.5
It shows that vulnerabilities in Enterprise version are still present, just slightly more obfuscated. But security through obscurity does not work!

The glaring vulnerability in Standard version is fixed, and 8.x Standard versions seem to be safe. Funny, isn't it - you'd expect a corporate product to provide better security than home-edition, yet this is not the case.. smile

Download link for Meltdown v1.5: http://www.mediafire.com/?0wc0vv1kauhwxbb