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vladimir

   

.NIET

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.NIET is an IDA Pro plugin. Its purpose is to import missing symbols (usually few thousands) which are resolved at runtime by .NET Native compiled binaries. These symbols lie in SharedLibrary.dll and are not exported by this one.

.NIET has been tested on IDA Pro 7.5 using python 3.8 on the following platforms:

  • Windows
  • Linux

This plugin currently supports the following .NET Native framework versions:

  • 1.3
  • 1.6
  • 1.7
  • 2.2

Please create an issue if you encounter another version.

Installation

Copy these elements to your IDA Pro plugin directory:

dotNIET_plugin.py
dotNIET\

Dependencies

.NIET relies on pefile in order to parse resources directories.

pefile can be installed as follows:

pip install pefile

Requirements

Because symbols are imported from SharedLibrary.dll, this one must be provided to .NIET along with its pdb (its location is searched by the plugin within _NT_SYMBOL_PATH).

Helpers are implemented to identify .NET Native framework versions and verifying that SharedLibrary.dll pdb exists within the configured symbols path.

Usage

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.NIET can be launched using shortcut Alt-Shift-N or through the Edit/Plugins menu.

Upon launch, the plugin tries to identify current binary .NET Native framework version. All you have to do is to select SharedLibrary.dll in the right version then click Run.

.NIET will identify target dll .NET Native framework version and prompt a message if versions are not the same. Major and Minor version numbers are usually the only ones that matter.

Functioning

.NIET looks for .NET Native custom import descriptors table within the .rdata section. To proceed so, it reads at specific offsets of a Custom Header structure then parses an ordinals array.

This ordinals array points to various locations within a SharedLibrary.dll's custom table entries.

Symbol resolution is achieved by launching an IDA Pro headless instance through its binary idat in order to parse SharedLibrary.dll pdb

Imported symbols naming convention

Symbols are imported as is if possible but some corner cases may be encountered:

  • sometimes imported addresses are solely jmpstubs symbols to offsets or single jmp instructions to symbols. Their symbol name is replaced by .NIET to the target function's name prepended with jmp_
  • some addresses resolved by the .NET Native runtime point to symbols after multiple derefences. If .NIET cannot find a symbol at an imported address it tries to dereference until it finds one. deref_X is appended to this symbol name, if found, with X being the number of derefs.
  • some addresses points to offsets within an EETableSection table. Being new to .NET Native, I have no idea what this is (yet?) so these addresses are labeled EETableSection_XXX, XXX being offsets from EETableSection within SharedLibrary.dll

Known limitations

  • Does not work (yet) on macOS IDA Pro version
  • .NIET is pretty slow as it requires to parse pdb of fairly huge binaries
  • "restore .idata" option (kind of "undo" option) solely unsets imported symbols. Because IDA automagically propagates names during import, you will likely need to run auto-analysis again if you want to remove all traces of imported symbols. A workaround could be to create a database snapshot before running the plugin.
  • .NIET parses symbols solely from SharedLibrary.dll module although the original routine in charge of symbols resolution likely offers the possibility to parse other modules (I don't know if this really occurs apart from SharedLibrary.dll module)

Troubleshooting

idat logfile is defined to %tmpdir%/dotNIETlogs.txt

Why such a name

Because reversing .NET Native is a nightmare