#!/usr/bin/env python3
"""Agent for implementing and auditing AppLocker application whitelisting policies."""

import json
import argparse
import re
import xml.etree.ElementTree as ET
from datetime import datetime
from pathlib import Path


APPLOCKER_EVENT_IDS = {
    8002: ("EXE/DLL allowed", "INFO"),
    8003: ("EXE/DLL denied", "HIGH"),
    8004: ("EXE/DLL would be denied (audit)", "MEDIUM"),
    8005: ("Script allowed", "INFO"),
    8006: ("Script denied", "HIGH"),
    8007: ("Script would be denied (audit)", "MEDIUM"),
    8020: ("Packaged app allowed", "INFO"),
    8021: ("Packaged app denied", "HIGH"),
    8022: ("Packaged app would be denied (audit)", "MEDIUM"),
}


def parse_applocker_policy(xml_path):
    """Parse an exported AppLocker policy XML file."""
    tree = ET.parse(xml_path)
    root = tree.getroot()
    ns = {"al": "http://schemas.microsoft.com/windows/2006/applocker"}
    rules = []
    for collection in root.findall(".//al:RuleCollection", ns):
        rule_type = collection.get("Type", "")
        mode = collection.get("EnforcementMode", "NotConfigured")
        for rule in collection:
            rule_data = {
                "collection": rule_type,
                "enforcement_mode": mode,
                "name": rule.get("Name", ""),
                "action": rule.get("Action", ""),
                "user_or_group": rule.get("UserOrGroupSid", ""),
                "type": rule.tag.replace(f"{{{ns.get('al', '')}}}", ""),
            }
            conditions = rule.findall(".//*")
            for cond in conditions:
                if "Path" in cond.tag:
                    rule_data["path"] = cond.get("Path", "")
                elif "Publisher" in cond.tag:
                    rule_data["publisher"] = cond.get("PublisherName", "")
                elif "Hash" in cond.tag:
                    rule_data["hash"] = cond.get("Data", "")
            rules.append(rule_data)
    return rules


def audit_applocker_rules(rules):
    """Audit AppLocker rules for security weaknesses."""
    findings = []
    for rule in rules:
        if rule.get("enforcement_mode") == "AuditOnly":
            findings.append({
                "collection": rule["collection"],
                "issue": "audit_mode_only",
                "severity": "MEDIUM",
                "recommendation": "Switch to Enforce mode after validation",
            })
        if rule.get("enforcement_mode") == "NotConfigured":
            findings.append({
                "collection": rule["collection"],
                "issue": "not_configured",
                "severity": "HIGH",
                "recommendation": "Enable enforcement for this rule collection",
            })
        path = rule.get("path", "")
        if path and rule.get("action") == "Allow":
            risky_paths = [r"\\Users\\", r"\\Temp\\", r"\\Downloads\\",
                          r"\\AppData\\", r"\\ProgramData\\"]
            for rp in risky_paths:
                if re.search(rp, path, re.IGNORECASE):
                    findings.append({
                        "rule_name": rule["name"],
                        "path": path,
                        "issue": "allow_from_user_writable_path",
                        "severity": "CRITICAL",
                    })
                    break
        if rule.get("user_or_group") == "S-1-1-0" and rule.get("action") == "Allow":
            findings.append({
                "rule_name": rule["name"],
                "issue": "allow_for_everyone",
                "severity": "MEDIUM",
            })
    return findings


def analyze_applocker_events(log_path):
    """Analyze AppLocker event logs for blocked and audit events."""
    events = []
    with open(log_path) as f:
        for line in f:
            try:
                entry = json.loads(line)
            except json.JSONDecodeError:
                continue
            event_id = int(entry.get("EventID", entry.get("event_id", 0)))
            if event_id in APPLOCKER_EVENT_IDS:
                desc, severity = APPLOCKER_EVENT_IDS[event_id]
                events.append({
                    "event_id": event_id,
                    "description": desc,
                    "severity": severity,
                    "timestamp": entry.get("TimeCreated", entry.get("timestamp", "")),
                    "computer": entry.get("Computer", entry.get("hostname", "")),
                    "user": entry.get("User", entry.get("user", "")),
                    "file_path": entry.get("FilePath", entry.get("file_path", "")),
                    "publisher": entry.get("Publisher", ""),
                })
    denied = [e for e in events if "denied" in e["description"].lower()]
    audit = [e for e in events if "audit" in e["description"].lower()]
    return {"total_events": len(events), "denied": denied, "audit_blocks": audit}


def generate_baseline_policy():
    """Generate a baseline AppLocker policy recommendation."""
    return {
        "exe_rules": {
            "enforcement_mode": "Enforce",
            "default_rules": [
                {"action": "Allow", "path": "%PROGRAMFILES%\\*", "scope": "Everyone"},
                {"action": "Allow", "path": "%WINDIR%\\*", "scope": "Everyone"},
                {"action": "Allow", "path": "*", "scope": "BUILTIN\\Administrators"},
            ],
        },
        "script_rules": {
            "enforcement_mode": "Enforce",
            "default_rules": [
                {"action": "Allow", "path": "%PROGRAMFILES%\\*", "scope": "Everyone"},
                {"action": "Allow", "path": "%WINDIR%\\*", "scope": "Everyone"},
            ],
        },
        "dll_rules": {
            "enforcement_mode": "AuditOnly",
            "note": "Start with audit mode due to high volume",
        },
    }


def main():
    parser = argparse.ArgumentParser(description="AppLocker Whitelisting Agent")
    parser.add_argument("--policy", help="Exported AppLocker policy XML")
    parser.add_argument("--events", help="AppLocker event log (JSON lines)")
    parser.add_argument("--output", default="applocker_audit_report.json")
    parser.add_argument("--action", choices=["audit", "events", "baseline", "full"],
                        default="full")
    args = parser.parse_args()

    report = {"generated_at": datetime.utcnow().isoformat(), "findings": {}}

    if args.action in ("audit", "full") and args.policy:
        rules = parse_applocker_policy(args.policy)
        findings = audit_applocker_rules(rules)
        report["findings"]["policy_audit"] = findings
        report["findings"]["total_rules"] = len(rules)
        print(f"[+] Policy rules: {len(rules)}, Issues: {len(findings)}")

    if args.action in ("events", "full") and args.events:
        result = analyze_applocker_events(args.events)
        report["findings"]["event_analysis"] = result
        print(f"[+] Events: {result['total_events']}, Denied: {len(result['denied'])}")

    if args.action in ("baseline", "full"):
        baseline = generate_baseline_policy()
        report["findings"]["baseline_policy"] = baseline
        print("[+] Baseline policy generated")

    with open(args.output, "w") as fout:
        json.dump(report, fout, indent=2, default=str)
    print(f"[+] Report saved to {args.output}")


if __name__ == "__main__":
    main()