enodia-sentinal/enodia_sentinel/web.py

# SPDX-License-Identifier: GPL-3.0-or-later
"""Read-only web dashboard, served by the stdlib http.server (zero deps).

Exposes a small JSON API over the log directory plus a single self-contained
page. It is deliberately read-only — no actions, no writes — because it serves
sensitive forensic data. By default it binds the host's Tailscale address and
requires a bearer token; on loopback the token is optional.
"""
from __future__ import annotations

import hmac
import json
import os
import re
import secrets
import subprocess
import time
from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer
from pathlib import Path
from urllib.parse import parse_qs, urlparse

from . import __version__
from .config import Config

_STATIC = Path(__file__).parent / "static"
_ALERT_NAME = re.compile(r"^alert-\d{8}-\d{6}\.(json|log)$")


# --- network helpers -------------------------------------------------------

def detect_tailscale_ip() -> str | None:
    """Best-effort Tailscale IPv4 of this host."""
    try:
        out = subprocess.run(["tailscale", "ip", "-4"], capture_output=True,
                             text=True, timeout=4).stdout.strip().splitlines()
        if out and out[0]:
            return out[0].strip()
    except (OSError, subprocess.SubprocessError):
        pass
    try:
        out = subprocess.run(["ip", "-o", "-4", "addr", "show", "tailscale0"],
                             capture_output=True, text=True, timeout=4).stdout
        m = re.search(r"inet (\d+\.\d+\.\d+\.\d+)", out)
        if m:
            return m.group(1)
    except (OSError, subprocess.SubprocessError):
        pass
    return None


def resolve_bind(cfg: Config) -> str:
    if cfg.web_bind:
        return cfg.web_bind
    return detect_tailscale_ip() or "127.0.0.1"


def is_loopback(addr: str) -> bool:
    return addr.startswith("127.") or addr in ("::1", "localhost")


def ensure_token(cfg: Config) -> str:
    if cfg.web_token:
        return cfg.web_token
    path = cfg.log_dir / ".web_token"
    try:
        if path.is_file():
            tok = path.read_text().strip()
            if tok:
                return tok
    except OSError:
        pass
    tok = secrets.token_urlsafe(24)
    try:
        cfg.log_dir.mkdir(parents=True, exist_ok=True)
        path.write_text(tok)
        path.chmod(0o600)
    except OSError:
        pass
    return tok


# --- data layer (pure, testable) ------------------------------------------

def list_alerts(cfg: Config, limit: int = 200) -> list[dict]:
    out = []
    for p in sorted(cfg.log_dir.glob("alert-*.json"), reverse=True)[:limit]:
        try:
            d = json.loads(p.read_text())
        except (OSError, ValueError):
            continue
        out.append({
            "name": p.with_suffix(".log").name,
            "time": d.get("time", ""),
            "host": d.get("host", ""),
            "severity": d.get("severity", ""),
            "signatures": sorted({a.get("signature", "") for a in d.get("alerts", [])}),
            "sids": sorted({a.get("sid", 0) for a in d.get("alerts", []) if a.get("sid")}),
            "count": len(d.get("alerts", [])),
        })
    return out


def get_alert(cfg: Config, name: str) -> dict | None:
    if not _ALERT_NAME.match(name):
        return None
    base = cfg.log_dir / name
    jpath = base.with_suffix(".json")
    try:
        data = {"json": json.loads(jpath.read_text())} if jpath.is_file() else {}
        lpath = base.with_suffix(".log")
        if lpath.is_file():
            data["text"] = lpath.read_text()
        return data or None
    except (OSError, ValueError):
        return None


def tail_events(cfg: Config, limit: int = 100) -> list[str]:
    try:
        lines = cfg.events_log.read_text().splitlines()
    except OSError:
        return []
    return lines[-limit:]


def daemon_status(cfg: Config) -> dict:
    pid_alive = False
    pidfile = cfg.log_dir / "sentinel.pid"
    try:
        pid = int(pidfile.read_text().strip())
        os.kill(pid, 0)
        pid_alive = True
    except (OSError, ValueError):
        pid_alive = False
    alerts = list_alerts(cfg, limit=10000)
    counts: dict[str, int] = {}
    for a in alerts:
        counts[a["severity"]] = counts.get(a["severity"], 0) + 1
    ebpf = "unknown"
    for line in reversed(tail_events(cfg, 200)):
        if "eBPF exec monitor:" in line:
            ebpf = line.split("eBPF exec monitor:", 1)[1].strip()
            break
    return {
        "version": __version__,
        "running": pid_alive,
        "total_alerts": len(alerts),
        "counts": counts,
        "last_alert": alerts[0]["time"] if alerts else None,
        "ebpf": ebpf,
        "host": os.uname().nodename,
    }


# --- HTTP layer ------------------------------------------------------------

class _Handler(BaseHTTPRequestHandler):
    server_version = "EnodiaSentinel"

    def log_message(self, *a):  # quiet by default
        pass

    def _authorized(self) -> bool:
        token = self.server.token  # type: ignore[attr-defined]
        if not token:
            return True
        supplied = ""
        auth = self.headers.get("Authorization", "")
        if auth.startswith("Bearer "):
            supplied = auth[7:]
        if not supplied:
            supplied = parse_qs(urlparse(self.path).query).get("token", [""])[0]
        return hmac.compare_digest(supplied, token)

    def _json(self, obj, status=200):
        body = json.dumps(obj).encode("utf-8")
        self.send_response(status)
        self.send_header("Content-Type", "application/json")
        self.send_header("Content-Length", str(len(body)))
        self.end_headers()
        self.wfile.write(body)

    def do_GET(self):
        path = urlparse(self.path).path
        if not self._authorized():
            self._json({"error": "unauthorized"}, 401)
            return
        cfg: Config = self.server.cfg  # type: ignore[attr-defined]

        if path in ("/", "/index.html", "/dashboard.html"):
            self._serve_static("dashboard.html", "text/html; charset=utf-8")
        elif path == "/api/status":
            self._json(daemon_status(cfg))
        elif path == "/api/alerts":
            self._json(list_alerts(cfg))
        elif path.startswith("/api/alerts/"):
            alert = get_alert(cfg, path.rsplit("/", 1)[-1])
            self._json(alert if alert else {"error": "not found"},
                       200 if alert else 404)
        elif path == "/api/events":
            self._json({"events": tail_events(cfg)})
        else:
            self._json({"error": "not found"}, 404)

    def _serve_static(self, name, ctype):
        try:
            body = (_STATIC / name).read_bytes()
        except OSError:
            self._json({"error": "missing asset"}, 500)
            return
        self.send_response(200)
        self.send_header("Content-Type", ctype)
        self.send_header("Content-Length", str(len(body)))
        self.end_headers()
        self.wfile.write(body)


def build_server(cfg: Config) -> tuple[ThreadingHTTPServer, str, str]:
    """Construct the server (without serving). Returns (httpd, bind, token)."""
    bind = resolve_bind(cfg)
    token = cfg.web_token
    if not is_loopback(bind) and not token:
        token = ensure_token(cfg)
    httpd = ThreadingHTTPServer((bind, cfg.web_port), _Handler)
    httpd.cfg = cfg          # type: ignore[attr-defined]
    httpd.token = token      # type: ignore[attr-defined]
    return httpd, bind, token


def serve(cfg: Config) -> None:
    httpd, bind, token = build_server(cfg)
    suffix = f"/?token={token}" if token else "/"
    url = f"http://{bind}:{cfg.web_port}{suffix}"
    msg = f"{time.strftime('%FT%T%z')} dashboard serving at {url}"
    print(msg, flush=True)
    try:
        with open(cfg.events_log, "a") as fh:
            fh.write(msg + "\n")
    except OSError:
        pass
    try:
        httpd.serve_forever()
    except KeyboardInterrupt:
        httpd.shutdown()