6 ms·

Breaking SecuROM 7 – A Dissection

140 points by davikr 3y ago

farmdve 3y ago
Ah yes, right up my alley. Sort of. I spent many months reverse engineering a SC8 executable for fun, yep purely for fun. 10 years ago now. I have more experience with SecuROM 8. Did you guys know there is a hidden flag that is parsed on executable running that initializes a separate application which generates a file you can send to the authors of SecuROM that holds the version of SecuROM and quite a lot of other details? Opaque predicates, VM, simple code integrity checks(int 3), xchg used as control flow obfuscation? It was all there. It took me a while to get the program running under a debugger. Once I did there were a bunch of threads running which would detect tampering or pausing of the threads and kill the process. After suspending those I could do whatever I want. The DRM used a lot of control flow methods, especially hardware breakpoints and UD2 instruction. At the time of Unicorn engine's popularity I made a custom plugin to emulate the zlib code embedded inside to search for hidden API calls, unfortunately due to the way QEMU emitted some instructions for the helpers some instructon hooks were called a few times more e.g those with a rep prefix severely skewing instruction counting. Anyway, VM hunting was difficult. The VM had quite a few single-threaded VM contexts so it could run a lot of programs. From then on it was a matter of reverse engineering the opcodes. at the time I used Olly to trace and log the instruction handlers and opcodes and then using Notepad++ magic I could clean it up from the control flow in a single coherent picture. Honestly I've forgotten most of it now. But a few years ago I did write my own Control flow graph generator in Java just to find the 20 or 30 thousand code integrity checks and trace them statically and then was going to use it on the VM. The most unusual thing is, I often communicated with one of the devs of SecuROM on IRC, of course I did not ask him anything nor did he reveal anything, that is of course illegal. I remember asking him about the little "Cut my life into pieces" tidbit he left just after VMEnter. Needless to say it is thanks to SecuROM that I gained an interest in RE. Yes I was a novice and dived deep down into a commercial DRM. Thanks to it I learned a lot and is helping me even today, yep as I type this I am working on a SH2 architecture firmware. But back in the day SecuROM inspired me to write this little ugly thing https://github.com/farmdve/TextVM https://github.com/farmdve/TextVM
- markus_zhang 3y ago
  Thanks for sharing. I'm not a student of the RE art so just curious about what you just said -- by saying VM did you mean the whole SC8 is running some core code inside a VM (of course within the same executable)? I assume that the intermediate code is definitely not public so people like you have to RE all those stuffs too?
  - farmdve 3y ago
    It's called an Obfuscation Virtual Machine running custom opcodes. These opcodes were decoded in a special way and a single x86 instruction like mov imm, reg would get translated in 20-30 instructions most of them junk, but they were not laid out contiguously, you would execute one junk instruction and then return to the dispatcher to get to the next one, if I remember correctly. This made the VM and tracing dog slow. Additionally it used a small 256 or 1024 byte scratch buffer for the virtual registers that held data. I've forgotten now how it was exactly. The entire VM used only jmp instructions which was how you would spot it.
    - markus_zhang 3y ago
      Thanks. I got the idea. Looks like they really wanted to slow you guys down :D I wonder if modern AI could solve that for you. "Oh look, that huge block essentially just set some variable to 127".
renegat0x0 3y ago
It is a nice hollow shell of a page. Some links are already dead. Mentions of forums lead to nowhere. Tools were discontinued on 2014. Funny how things move, and some parts become history and myths.
- userbinator 3y ago
  web.archive.org is extremely useful for digging back into history.
  - mdaniel 3y ago
    And, fun fact, DDG has a bang so one can just command-l, command-c, type "!wayback ", command-v and it'll redirect to https://web.archive.org/web/*/http://forums.accessroot.com/index.php?showtopic=4361&st=0 https://web.archive.org/web/*/http://forums.accessroot.com/i... but in this case the 4 captures are all captures of the forum's 404 page, and thus were not taken early enough to actually preserve the history I didn't check any of the rest of the links, figuring they were in the same boat of "too obscure to have been preserved"
nekitamo 3y ago
I’m glad someone preserved these tutorials. I was focused on cracking Safedisc games at the time, and even wrote some Safedisc/Safecast tutorials myself. I never had the skills to crack Securom though, respect to Human and Deroko and the others on the ARTeam forums at the time. Also iirc after this tutorial deroko wrote another one one breaking the Securom VM obfuscation. It was great work, one of the first public tutorials at the time on breaking such obfuscation. I wonder if its also been archived. Finally, it should be noted that Securom is a predecessor to Denuvo. I remember debugging early versions of Denuvo and being struck by how similar they are. I wonder how much of the code and techniques are in common between the two, especially now in 2024. The old reversing scene has changed. I guess everyone grew up and got families and jobs. But when I see what the kids are up to in the multiplayer cheating forums, I see the spirit is still alive and well. Cheers and happy debugging.
- jsheard 3y ago
  The cracking scene seems to be split between two extremes nowadays, on one end most new games are just using the basic Steam or Epic DRM, which are trivially defeated with open source wrappers so making a pirate release is mostly just boring acquisition and packaging work that basically anyone can do. The other extreme is Denuvo protected games which are so tedious to crack that there's almost no overlap between people with the skills to do it and those with the time and patience to do it.
  - punkybr3wster 3y ago
    And seemingly the few that are willing are somewhat insane. I know it takes a special type but wowzers.
    - jsheard 3y ago
      Shout-out to that one guy who has figured out Denuvo but only appears once a year to crack the latest Football Manager game, refuses to elaborate, and leaves until the next Football Manager game comes out. They know what they like, and it's Football Manager, exclusively.
jsheard 3y ago
Are there any public breakdowns of techniques used by Denuvo? That's still proving to be a PITA for cracking groups to deal with.
- jasondoty 3y ago
  Bulgarian cracker Voksi, also alleged to be the man behind Empress, made a video for V4 https://youtu.be/suABtb8_2Zk https://youtu.be/suABtb8_2Zk
cf1241290841 3y ago
If you are going down a DRM search trip, both Widevine key dumping and DMCA compliant HDMI / HDCP downgrade hardware are quite interesting topics.
atVelocet 3y ago
There was a strange situation when SecuROM came onto the scene: The first patch for most games had no SecuROM at all and so it was just patching the usual CD checks.
mschuster91 3y ago
> From what I can see the flag at [EAX+4] is somehow switched on when debugged. I wonder if a look into the leaked Windows kernel source code files (I _think_ the most current dump is still old Win2k?) could help out to decipher what these two RESERVED flags are used for? PEB_LDR_DATA still has them named as RESERVED1/2 [1]. [1] https://learn.microsoft.com/de-de/windows/win32/api/winternl/ns-winternl-peb_ldr_data https://learn.microsoft.com/de-de/windows/win32/api/winternl...
- CSm1n 3y ago
  It is a flag that says whether the loader data is initialized or not. The layout of PEB_LDR_DATA “leaked” long time ago in public PDBs. More context: It has nothing to do with debugging. However, if you attach to the process early enough, you might see the flag as 0 and eventually it would switch to 1. That is probably what threw him off.
  - lukan 3y ago
    "you might see the flag as 0 and eventually it would switch to 1" Sorry, noob question: Were there easy avaiable tools (in the debugger), to monitor a variable like this and have the debugger stop exactly when it was going to change, so you could see which thread and function did it and why?
    - DaiPlusPlus 3y ago
      Yes, x86 kernel-mode debuggers support hardware breakpoints that cause the attached debugger (running on a separate machine, of course) to break not just when a specific address/instruction is executed, but also whenever some address is written to (and also possibly read-from too, I think?)
    - jasomill 3y ago
      Yes: many debuggers support setting watchpoints[1] that break on writes to a particular memory location. Depending on the platform and the debugger, these can be implemented using CPU architecture-specific debugging features, or in software, by single-step program execution and checking watched addresses for changes after each step. [1] https://sourceware.org/gdb/current/onlinedocs/gdb.html/Set-Watchpoints.html https://sourceware.org/gdb/current/onlinedocs/gdb.html/Set-W...
matheusmoreira 3y ago
> As you can see exe is 97Mb, biohazard exe without securom is Just 6Mb, that’s how protections hurt customers, not my fault then. A 93.8% reduction... That's brutal.

140 points by davikr 3y ago

Ah yes, right up my alley. Sort of. I spent many months reverse engineering a SC8 executable for fun, yep purely for fun. 10 years ago now. I have more experience with SecuROM 8. Did you guys know there is a hidden flag that is parsed on executable running that initializes a separate application which generates a file you can send to the authors of SecuROM that holds the version of SecuROM and quite a lot of other details? Opaque predicates, VM, simple code integrity checks(int 3), xchg used as control flow obfuscation? It was all there. It took me a while to get the program running under a debugger. Once I did there were a bunch of threads running which would detect tampering or pausing of the threads and kill the process. After suspending those I could do whatever I want. The DRM used a lot of control flow methods, especially hardware breakpoints and UD2 instruction. At the time of Unicorn engine's popularity I made a custom plugin to emulate the zlib code embedded inside to search for hidden API calls, unfortunately due to the way QEMU emitted some instructions for the helpers some instructon hooks were called a few times more e.g those with a rep prefix severely skewing instruction counting. Anyway, VM hunting was difficult. The VM had quite a few single-threaded VM contexts so it could run a lot of programs. From then on it was a matter of reverse engineering the opcodes. at the time I used Olly to trace and log the instruction handlers and opcodes and then using Notepad++ magic I could clean it up from the control flow in a single coherent picture. Honestly I've forgotten most of it now. But a few years ago I did write my own Control flow graph generator in Java just to find the 20 or 30 thousand code integrity checks and trace them statically and then was going to use it on the VM. The most unusual thing is, I often communicated with one of the devs of SecuROM on IRC, of course I did not ask him anything nor did he reveal anything, that is of course illegal. I remember asking him about the little "Cut my life into pieces" tidbit he left just after VMEnter. Needless to say it is thanks to SecuROM that I gained an interest in RE. Yes I was a novice and dived deep down into a commercial DRM. Thanks to it I learned a lot and is helping me even today, yep as I type this I am working on a SH2 architecture firmware. But back in the day SecuROM inspired me to write this little ugly thing https://github.com/farmdve/TextVM https://github.com/farmdve/TextVM

markus_zhang 3y ago
Thanks for sharing. I'm not a student of the RE art so just curious about what you just said -- by saying VM did you mean the whole SC8 is running some core code inside a VM (of course within the same executable)? I assume that the intermediate code is definitely not public so people like you have to RE all those stuffs too?
- farmdve 3y ago
  It's called an Obfuscation Virtual Machine running custom opcodes. These opcodes were decoded in a special way and a single x86 instruction like mov imm, reg would get translated in 20-30 instructions most of them junk, but they were not laid out contiguously, you would execute one junk instruction and then return to the dispatcher to get to the next one, if I remember correctly. This made the VM and tracing dog slow. Additionally it used a small 256 or 1024 byte scratch buffer for the virtual registers that held data. I've forgotten now how it was exactly. The entire VM used only jmp instructions which was how you would spot it.
  - markus_zhang 3y ago
    Thanks. I got the idea. Looks like they really wanted to slow you guys down :D I wonder if modern AI could solve that for you. "Oh look, that huge block essentially just set some variable to 127".

renegat0x0 3y ago

It is a nice hollow shell of a page. Some links are already dead. Mentions of forums lead to nowhere. Tools were discontinued on 2014. Funny how things move, and some parts become history and myths.

userbinator 3y ago
web.archive.org is extremely useful for digging back into history.
- mdaniel 3y ago
  And, fun fact, DDG has a bang so one can just command-l, command-c, type "!wayback ", command-v and it'll redirect to https://web.archive.org/web/*/http://forums.accessroot.com/index.php?showtopic=4361&st=0 https://web.archive.org/web/*/http://forums.accessroot.com/i... but in this case the 4 captures are all captures of the forum's 404 page, and thus were not taken early enough to actually preserve the history I didn't check any of the rest of the links, figuring they were in the same boat of "too obscure to have been preserved"

nekitamo 3y ago

I’m glad someone preserved these tutorials. I was focused on cracking Safedisc games at the time, and even wrote some Safedisc/Safecast tutorials myself. I never had the skills to crack Securom though, respect to Human and Deroko and the others on the ARTeam forums at the time. Also iirc after this tutorial deroko wrote another one one breaking the Securom VM obfuscation. It was great work, one of the first public tutorials at the time on breaking such obfuscation. I wonder if its also been archived. Finally, it should be noted that Securom is a predecessor to Denuvo. I remember debugging early versions of Denuvo and being struck by how similar they are. I wonder how much of the code and techniques are in common between the two, especially now in 2024. The old reversing scene has changed. I guess everyone grew up and got families and jobs. But when I see what the kids are up to in the multiplayer cheating forums, I see the spirit is still alive and well. Cheers and happy debugging.

jsheard 3y ago
The cracking scene seems to be split between two extremes nowadays, on one end most new games are just using the basic Steam or Epic DRM, which are trivially defeated with open source wrappers so making a pirate release is mostly just boring acquisition and packaging work that basically anyone can do. The other extreme is Denuvo protected games which are so tedious to crack that there's almost no overlap between people with the skills to do it and those with the time and patience to do it.
- punkybr3wster 3y ago
  And seemingly the few that are willing are somewhat insane. I know it takes a special type but wowzers.
  - jsheard 3y ago
    Shout-out to that one guy who has figured out Denuvo but only appears once a year to crack the latest Football Manager game, refuses to elaborate, and leaves until the next Football Manager game comes out. They know what they like, and it's Football Manager, exclusively.

jsheard 3y ago

Are there any public breakdowns of techniques used by Denuvo? That's still proving to be a PITA for cracking groups to deal with.

jasondoty 3y ago
Bulgarian cracker Voksi, also alleged to be the man behind Empress, made a video for V4 https://youtu.be/suABtb8_2Zk https://youtu.be/suABtb8_2Zk

cf1241290841 3y ago

If you are going down a DRM search trip, both Widevine key dumping and DMCA compliant HDMI / HDCP downgrade hardware are quite interesting topics.

atVelocet 3y ago

There was a strange situation when SecuROM came onto the scene: The first patch for most games had no SecuROM at all and so it was just patching the usual CD checks.

mschuster91 3y ago

> From what I can see the flag at [EAX+4] is somehow switched on when debugged. I wonder if a look into the leaked Windows kernel source code files (I _think_ the most current dump is still old Win2k?) could help out to decipher what these two RESERVED flags are used for? PEB_LDR_DATA still has them named as RESERVED1/2 [1]. [1] https://learn.microsoft.com/de-de/windows/win32/api/winternl/ns-winternl-peb_ldr_data https://learn.microsoft.com/de-de/windows/win32/api/winternl...

CSm1n 3y ago
It is a flag that says whether the loader data is initialized or not. The layout of PEB_LDR_DATA “leaked” long time ago in public PDBs. More context: It has nothing to do with debugging. However, if you attach to the process early enough, you might see the flag as 0 and eventually it would switch to 1. That is probably what threw him off.
- lukan 3y ago
  "you might see the flag as 0 and eventually it would switch to 1" Sorry, noob question: Were there easy avaiable tools (in the debugger), to monitor a variable like this and have the debugger stop exactly when it was going to change, so you could see which thread and function did it and why?
  - DaiPlusPlus 3y ago
    Yes, x86 kernel-mode debuggers support hardware breakpoints that cause the attached debugger (running on a separate machine, of course) to break not just when a specific address/instruction is executed, but also whenever some address is written to (and also possibly read-from too, I think?)
  - jasomill 3y ago
    Yes: many debuggers support setting watchpoints[1] that break on writes to a particular memory location. Depending on the platform and the debugger, these can be implemented using CPU architecture-specific debugging features, or in software, by single-step program execution and checking watched addresses for changes after each step. [1] https://sourceware.org/gdb/current/onlinedocs/gdb.html/Set-Watchpoints.html https://sourceware.org/gdb/current/onlinedocs/gdb.html/Set-W...

matheusmoreira 3y ago

> As you can see exe is 97Mb, biohazard exe without securom is Just 6Mb, that’s how protections hurt customers, not my fault then. A 93.8% reduction... That's brutal.