Symless

Automatic structures recovering plugin for IDA. Able to reconstruct structures/classes and virtual tables used in a binary.

Features

• Automatic creation of identified structures (c++ classes, virtual tables and others)
• Xrefs on structures usages
• Functions typing using gathered information

Two modes are available: Pre-Analysis and Plugin.

Plugin mode

Interactive IDA plugin. Uses static analysis from an entry point selected by the user to build and propagate a structure.

Installation

$ python plugin/install.py [-u]

Manual installation: copy the symless directory and symless_plugin.py into IDA plugins folder.

Usage

While in IDA disassembly view:

• Right-click a register that contains a structure pointer
• Select Propagate structure
• Select which structure & shift to apply

Symless will then propagate the structure, build it and type untyped functions / operands with the harvested information. This action can be undone with Ctrl-Z. A new structure can be created, an existing one can be completed.

Pre-Analysis mode

Before use

Specify your IDA installation:

export IDA_DIR="$HOME/idapro-M.m"

Edit the config file to suit your case:

Specify the memory allocation functions used in your executable in the imports.csv file. Syntax is discussed there.

Symless uses those to find structures creations from memory allocations. C++ classes can also be retrieved from their virtual tables.

Usage

    $ python3 symless.py [-c config.csv] <target(s)>

• config.csv - configuration to be used (defaults to imports.csv)
• target(s) - one or more binaries / IDA bases

Symless will create a new IDA base when given an executable as an argument. Otherwise keep in mind it may overwrite user-modifications on existing bases.

Once done the IDA base will be populated with information about identified structures.

Support

Both stripped and non-stripped binaries are supported. Symbols are only used to name the created structures.

x64 and i386 binairies using the following calling conventions are supported:

• Windows x64 (__fastcall)
• Windows i386 (__stdcall & __thiscall)
• System V x64 (__fastcall)
• System V i386 (__stdcall)

IDA Pro 7.6 or newer & python 3

Disclaimer

Symless is still in development and might not fit every use cases.