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reverse-engineering-nim-and-other-exotic-binaries

Reverse engineers malware written in less-common compiled languages (Nim, Crystal, V, Zig, D) by detecting language-specific runtime signatures, name-mangling, and runtime strings to orient analysis. Activates for requests to reverse Nim malware, identify the source language of an exotic binary, or analyze Crystal/V/Zig/D compiled samples.

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See how to install

Files included (4)

  • SKILL.md2.8 KB
  • LICENSE340 B
  • references/api-reference.md1.2 KB
  • scripts/analyst.py1.9 KB

SKILL.md (original)

Review the instructions the agent will receive before you install.

Reverse Engineering Nim and Other Exotic Binaries

When to Use

  • You have a compiled binary that is not C/C++/Go/Rust/.NET and need to identify its source language (Nim, Crystal, V, Zig, D) to orient analysis.
  • Symbol/runtime patterns are unfamiliar and you want language-specific landmarks.

Do not use this for already-supported languages (Go/Rust have dedicated skills). This skill reads the binary statically and executes nothing.

Prerequisites

  • The binary (read inertly).

Safety & Handling

  • Read bytes statically; treat strings as untrusted.

Workflow

Step 1: Detect the source language

python scripts/analyst.py detect sample.bin

Scans for language runtime signatures: Nim (@m..nim, nimrtl, fatal.nim, stack trace, @ /nim), Crystal (Crystal::, crystal-lang), V (vlib/, _vinit), Zig (zig, panic: , std.builtin), and D (_Dmain, core.runtime, TypeInfo_).

Step 2: Locate runtime landmarks

Use the detected language's panic/exception and module strings to find main/init and error paths.

Step 3: Handle name mangling

Apply the language's mangling convention (e.g., Nim's proc__module_NNN) to recover readable names.

Step 4: Proceed with analysis

With the language identified, analyze logic; many exotic-language samples wrap the same C2/loader behavior.

Validation

  • Language detection is based on multiple corroborating runtime strings, not one weak hit.
  • Identified landmarks (panic/init) are consistent with the language.
  • Name demangling matches the language's documented scheme.

Pitfalls

  • Statically linked C runtime strings causing misclassification — weight language-specific markers.
  • Stripped binaries with few runtime strings.
  • Stagers in exotic languages that quickly hand off to shellcode.

References

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