re-yara

MCP server wrapping the YARA pattern-matching engine for binary triage.

re-yara is intentionally rule-agnostic: the server compiles whatever rule directory the analyst points it at, then scans files or directories against the compiled rules. No rules are bundled with the plugin — YARA rules describe categories of binary behaviour (e.g. encrypted-VM bytecode interpreter dispatcher, MBA-obfuscated arithmetic routine, legacy disc-based protection handshake) and writing them is an analyst decision, not a plugin one.

Tools

Tool	What it does
check_yara	Health check — return YARA version + whether yara-python is importable
compile_rules	Compile all *.yar / *.yara files under a directory into a YARA ruleset
scan_binary	Run a compiled ruleset against a single file
scan_directory	Walk a directory and run the compiled ruleset against every file

Install

Part of the RE-AI plugin; ./install.sh installs the package. To install standalone:

pip install -e ./servers/re-yara

Requires the yara C library (libyara) at runtime — yara-python links against it. Most package managers ship yara as a system package; on Debian/Ubuntu:

sudo apt-get install yara libyara-dev

Run

re-yara                           # stdio transport (default for MCP)
python -m re_yara                 # equivalent

Workflow

1. Author or download a directory of *.yar files. Each rule describes a category of behaviour the analyst wants to find.
2. Call compile_rules(rules_dir=<path>) to validate + compile.
3. Call scan_binary(path=<file>, rules_dir=<path>) for a single file, or scan_directory(path=<dir>, rules_dir=<path>) for a whole tree.

compile_rules is the heavy step (parses every rule file). The scan tools re-compile as needed — they're cheap if the rules haven't changed.

Why no bundled rules

YARA rules are an analyst artefact: they describe what you are looking for, which is a question only the user can answer. The plugin gives the engine; the user brings the policies. The server is also compatible with the signature-base and [MalwareBazaar] rule collections — point rules_dir at any of them.