reverse-skills-max: initial public release (restored, redacted, hardened)

vendor-new/analyst-ai-pack/skills/unpacking-upx-and-common-packers/scripts/analyst.py

@@ -0,0 +1,88 @@
+#!/usr/bin/env python3
+"""Detect common packers from PE section names, entropy, and import sparsity.
+
+Heuristic, signature-light packer detection on file bytes. It parses the PE section table
+directly (no third-party deps), computes per-section entropy, and matches known packer
+section names. It reads bytes only and never executes the sample.
+"""
+from __future__ import annotations
+
+import argparse
+import json
+import math
+import struct
+import sys
+from collections import Counter
+from pathlib import Path
+
+PACKER_SECTIONS = {
+    "UPX0": "UPX", "UPX1": "UPX", "UPX2": "UPX",
+    ".aspack": "ASPack", ".adata": "ASPack",
+    ".themida": "Themida", ".winlice": "WinLicense",
+    ".vmp0": "VMProtect", ".vmp1": "VMProtect",
+    ".petite": "Petite", ".mpress1": "MPRESS", ".mpress2": "MPRESS",
+    "FSG!": "FSG", ".nsp0": "NsPack", ".pec1": "PECompact",
+}
+
+
+def entropy(data: bytes) -> float:
+    if not data:
+        return 0.0
+    counts = Counter(data)
+    n = len(data)
+    return -sum((c / n) * math.log2(c / n) for c in counts.values())
+
+
+def parse_sections(data: bytes) -> list[dict]:
+    if data[:2] != b"MZ":
+        raise ValueError("not a PE")
+    e_lfanew = struct.unpack_from("<I", data, 0x3C)[0]
+    if data[e_lfanew:e_lfanew + 4] != b"PE\x00\x00":
+        raise ValueError("no PE signature")
+    num = struct.unpack_from("<H", data, e_lfanew + 6)[0]
+    opt = struct.unpack_from("<H", data, e_lfanew + 20)[0]
+    base = e_lfanew + 24 + opt
+    sections = []
+    for i in range(num):
+        b = base + i * 40
+        name = data[b:b + 8].rstrip(b"\x00").decode("latin-1", "replace")
+        raw_size = struct.unpack_from("<I", data, b + 16)[0]
+        raw_ptr = struct.unpack_from("<I", data, b + 20)[0]
+        blob = data[raw_ptr:raw_ptr + raw_size]
+        sections.append({"name": name, "raw_size": raw_size,
+                         "entropy": round(entropy(blob), 3)})
+    return sections
+
+
+def detect(path: str) -> dict:
+    data = Path(path).read_bytes()
+    sections = parse_sections(data)
+    hits = sorted({PACKER_SECTIONS[s["name"]] for s in sections
+                   if s["name"] in PACKER_SECTIONS})
+    high_entropy = [s["name"] for s in sections if s["entropy"] > 7.2]
+    whole = round(entropy(data), 3)
+    likely_packed = bool(hits) or whole > 7.2 or len(high_entropy) >= max(1, len(sections) - 1)
+    return {
+        "packer_signatures": hits,
+        "sections": sections,
+        "high_entropy_sections": high_entropy,
+        "whole_file_entropy": whole,
+        "likely_packed": likely_packed,
+        "recommendation": ("upx -d" if "UPX" in hits else
+                           "manual unpack in debugger" if likely_packed else
+                           "no packing indicators"),
+    }
+
+
+def main(argv: list[str] | None = None) -> int:
+    parser = argparse.ArgumentParser(description="Detect common packers")
+    sub = parser.add_subparsers(dest="cmd", required=True)
+    p = sub.add_parser("detect")
+    p.add_argument("file")
+    args = parser.parse_args(argv)
+    print(json.dumps(detect(args.file), indent=2))
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())