feat(phase-22): add import services for Sigma, LOLBAS, GTFOBins, CALDERA, Elastic and data sources panel (T-203 to T-207)
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308
backend/app/services/sigma_import_service.py
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308
backend/app/services/sigma_import_service.py
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"""Sigma Rules import service.
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Downloads the SigmaHQ repository ZIP from GitHub, parses every YAML rule
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file under ``rules/``, extracts MITRE ATT&CK tags, and creates
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:class:`DetectionRule` records in the database.
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Strategy
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--------
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1. Download the full SigmaHQ repo as a ZIP archive.
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2. Extract in a temporary directory.
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3. Walk all ``.yml`` files under ``rules/``.
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4. Parse each YAML file — extract title, description, logsource,
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detection tags, severity (``level``), and the raw YAML content.
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5. Filter: only import rules that have at least one ``attack.tXXXX`` tag.
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6. Create / skip ``DetectionRule`` rows keyed by ``(source, source_id)``.
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7. Clean up the temporary directory.
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Idempotency
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-----------
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Running the import twice does **not** create duplicates. Existing
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rules are identified by ``source = "sigma"`` + ``source_id`` (relative
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file path) and simply skipped.
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"""
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import io
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import logging
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import re
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import shutil
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import tempfile
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import zipfile
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from datetime import datetime
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from pathlib import Path
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import requests as _requests
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import yaml
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from sqlalchemy.orm import Session
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from app.models.detection_rule import DetectionRule
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from app.models.data_source import DataSource
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from app.services.audit_service import log_action
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logger = logging.getLogger(__name__)
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# ---------------------------------------------------------------------------
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# Constants
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# ---------------------------------------------------------------------------
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SIGMA_ZIP_URL = (
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"https://github.com/SigmaHQ/sigma/archive/refs/heads/main.zip"
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)
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_DOWNLOAD_TIMEOUT = 300
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_ZIP_ROOT_PREFIX = "sigma-main"
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# Regex to extract MITRE ATT&CK technique IDs from Sigma tags
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# e.g. "attack.t1059.001" → "T1059.001"
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_ATTACK_TAG_RE = re.compile(r"attack\.(t\d{4}(?:\.\d{3})?)", re.IGNORECASE)
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# Sigma severity levels
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_SEVERITY_MAP = {
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"informational": "informational",
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"low": "low",
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"medium": "medium",
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"high": "high",
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"critical": "critical",
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}
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# ---------------------------------------------------------------------------
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# Internal helpers
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# ---------------------------------------------------------------------------
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def _download_zip(url: str = SIGMA_ZIP_URL) -> bytes:
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"""Download the SigmaHQ ZIP and return raw bytes."""
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logger.info("Downloading SigmaHQ ZIP from %s …", url)
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resp = _requests.get(url, timeout=_DOWNLOAD_TIMEOUT, stream=True)
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resp.raise_for_status()
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content = resp.content
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logger.info("Downloaded %.1f MB", len(content) / (1024 * 1024))
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return content
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def _extract_zip(zip_bytes: bytes, dest: str) -> Path:
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"""Extract *zip_bytes* into *dest* and return the path to rules/ dir."""
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with zipfile.ZipFile(io.BytesIO(zip_bytes)) as zf:
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zf.extractall(dest)
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rules_dir = Path(dest) / _ZIP_ROOT_PREFIX / "rules"
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if not rules_dir.is_dir():
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raise FileNotFoundError(
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f"Expected rules directory not found at {rules_dir}"
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)
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return rules_dir
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def _extract_attack_tags(tags: list) -> list[str]:
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"""Extract MITRE technique IDs from Sigma tag list.
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Example input: ["attack.defense_evasion", "attack.t1059.001", "cve.2021.44228"]
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Example output: ["T1059.001"]
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"""
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technique_ids = []
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for tag in tags:
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m = _ATTACK_TAG_RE.match(str(tag).strip())
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if m:
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technique_ids.append(m.group(1).upper())
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return list(set(technique_ids))
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def _parse_sigma_rules(rules_dir: Path) -> list[dict]:
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"""Walk the rules directory and parse all Sigma YAML files.
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Returns a flat list of dicts, one per (rule, technique) combination.
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A single Sigma rule tagged with N techniques produces N entries.
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"""
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results: list[dict] = []
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yaml_files = sorted(rules_dir.rglob("*.yml"))
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logger.info("Found %d YAML files to parse", len(yaml_files))
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for yaml_path in yaml_files:
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relative_path = str(yaml_path.relative_to(rules_dir.parent))
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try:
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with open(yaml_path, "r", encoding="utf-8") as fh:
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data = yaml.safe_load(fh)
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except Exception as exc:
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logger.debug("Failed to parse %s: %s", yaml_path, exc)
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continue
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if not isinstance(data, dict):
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continue
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title = data.get("title", "").strip()
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if not title:
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continue
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# Extract ATT&CK technique IDs from tags
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tags = data.get("tags", [])
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if not isinstance(tags, list):
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continue
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technique_ids = _extract_attack_tags(tags)
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if not technique_ids:
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continue # Skip rules without ATT&CK mapping
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description = data.get("description", "")
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level = str(data.get("level", "")).lower()
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severity = _SEVERITY_MAP.get(level)
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# Extract logsource
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logsource = data.get("logsource", {})
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if not isinstance(logsource, dict):
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logsource = {}
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# Read full YAML content for storage
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try:
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with open(yaml_path, "r", encoding="utf-8") as fh:
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raw_content = fh.read()
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except Exception:
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raw_content = yaml.dump(data, default_flow_style=False)
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# False positive assessment
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falsepositives = data.get("falsepositives", [])
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if isinstance(falsepositives, list) and len(falsepositives) > 3:
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fp_rate = "high"
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elif isinstance(falsepositives, list) and len(falsepositives) > 1:
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fp_rate = "medium"
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else:
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fp_rate = "low"
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# Create one entry per technique
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for tech_id in technique_ids:
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source_url = (
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f"https://github.com/SigmaHQ/sigma/blob/main/"
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f"{relative_path.replace(chr(92), '/')}"
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)
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results.append({
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"mitre_technique_id": tech_id,
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"title": title[:500],
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"description": str(description)[:2000] if description else None,
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"source_id": relative_path,
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"source_url": source_url,
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"rule_content": raw_content,
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"severity": severity,
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"log_sources": logsource if logsource else None,
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"false_positive_rate": fp_rate,
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"platforms": _platforms_from_logsource(logsource),
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})
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logger.info("Parsed %d (rule, technique) pairs total", len(results))
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return results
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def _platforms_from_logsource(logsource: dict) -> list[str]:
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"""Infer platform list from Sigma logsource."""
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platforms = []
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product = str(logsource.get("product", "")).lower()
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service = str(logsource.get("service", "")).lower()
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if "windows" in product or "windows" in service:
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platforms.append("windows")
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if "linux" in product or "linux" in service:
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platforms.append("linux")
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if "macos" in product or "macos" in service:
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platforms.append("macos")
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# Sysmon → Windows
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if "sysmon" in service and "windows" not in platforms:
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platforms.append("windows")
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return platforms if platforms else None
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# ---------------------------------------------------------------------------
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# Public API
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# ---------------------------------------------------------------------------
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def sync(db: Session) -> dict:
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"""Download and import Sigma detection rules.
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Parameters
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----------
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db : Session
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Active SQLAlchemy database session.
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Returns
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-------
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dict
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Summary with ``created``, ``skipped_existing``, ``total_parsed``.
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"""
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tmp_dir = tempfile.mkdtemp(prefix="aegis_sigma_")
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try:
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zip_bytes = _download_zip()
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rules_dir = _extract_zip(zip_bytes, tmp_dir)
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parsed_rules = _parse_sigma_rules(rules_dir)
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finally:
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shutil.rmtree(tmp_dir, ignore_errors=True)
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logger.info("Cleaned up temp directory %s", tmp_dir)
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# Pre-load existing source_ids for dedup
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existing_ids: set[str] = {
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row[0]
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for row in db.query(DetectionRule.source_id)
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.filter(DetectionRule.source == "sigma")
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.filter(DetectionRule.source_id.isnot(None))
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.all()
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}
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created = 0
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skipped = 0
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for item in parsed_rules:
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# Dedup key: source_id (relative path). A rule file may produce
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# multiple entries (one per technique), but we deduplicate by
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# source_id so re-runs are safe. For multi-technique rules we
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# only skip if the exact same source_id is already present.
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dedup_key = f"{item['source_id']}::{item['mitre_technique_id']}"
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if item["source_id"] in existing_ids:
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skipped += 1
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continue
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rule = DetectionRule(
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mitre_technique_id=item["mitre_technique_id"],
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title=item["title"],
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description=item["description"],
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source="sigma",
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source_id=item["source_id"],
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source_url=item["source_url"],
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rule_content=item["rule_content"],
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rule_format="sigma_yaml",
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severity=item["severity"],
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platforms=item["platforms"],
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log_sources=item["log_sources"],
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false_positive_rate=item["false_positive_rate"],
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is_active=True,
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)
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db.add(rule)
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existing_ids.add(item["source_id"])
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created += 1
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db.commit()
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summary = {
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"created": created,
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"skipped_existing": skipped,
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"total_parsed": len(parsed_rules),
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}
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# Update DataSource record
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ds = db.query(DataSource).filter(DataSource.name == "sigma").first()
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if ds:
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ds.last_sync_at = datetime.utcnow()
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ds.last_sync_status = "success"
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ds.last_sync_stats = summary
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db.commit()
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logger.info("Sigma import complete — %s", summary)
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log_action(
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db,
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user_id=None,
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action="import_sigma_rules",
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entity_type="detection_rule",
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entity_id=None,
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details=summary,
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)
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return summary
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