gods-eye-view/server/providers/overpass/query.js

import {
  OVERPASS_MAX_AROUND_M,
  OVERPASS_MAX_BBOX_DEG,
  OVERPASS_AREA_ELEMENT_RE,
  OVERPASS_SELECTOR_RE,
  OVERPASS_BBOX_RE,
  OVERPASS_MAX_QL_TIMEOUT,
} from './constants.js';

/**
 * Whether a normalized Overpass query is BOUNDARY-class (admin `is_in` lookups
 * and area→relation pivots) — the static, expensive geometry that earns the
 * 30-day disk TTL. The enclosing-compound sweep and road fetches keep the
 * default TTL. Exported for tests.
 */
function isOverpassBoundaryQuery(cacheKey) {
  return /is_in\s*\(|\bpivot\b/i.test(String(cacheKey || ''));
}

/**
 * Validate + clamp an Overpass form body. Defends the generic proxy against
 * planet-scale abuse: requires exactly one `data` query in which EVERY element
 * selector is individually spatially bounded (around / bbox / is_in / poly /
 * area-set / pivot), rejects oversized radii and world-sized bboxes, and clamps
 * every `[timeout:]` directive. Comments + quoted literals are stripped first so
 * a fake bound inside a tag value can't satisfy the check.
 *
 * Every real app caller passes (annotations/locations/cctv use `around:`/`is_in`/
 * `area.`/`pivot`; traffic uses a small `(s,w,n,e)` bbox); a mixed query that
 * pairs one bounded selector with a global one is rejected.
 *
 * @returns {{ok:true, body:string} | {ok:false, error:string}}
 */
/**
 * Single-pass lexer: blank out quoted literals (→ empty quotes) and strip line
 * and block comments — recognizing each in one walk so a comment marker INSIDE a
 * quoted string is treated as string content, not a comment (and vice versa).
 * Chained regex replaces get the ordering wrong (a quoted slash-slash would hide
 * the rest of the line), which is exactly the bypass this avoids.
 */
function stripOverpassNoise(src) {
  let out = '';
  let i = 0;
  const n = src.length;
  while (i < n) {
    const c = src[i];
    if (c === '"' || c === "'") {
      const quote = c;
      i += 1;
      while (i < n) {
        if (src[i] === '\\') {
          i += 2;
          continue;
        } // escaped char
        if (src[i] === quote) {
          i += 1;
          break;
        } // closing quote
        i += 1;
      }
      out += quote + quote; // collapse the literal to empty quotes
      continue;
    }
    if (c === '/' && src[i + 1] === '*') {
      i += 2;
      while (i < n && !(src[i] === '*' && src[i + 1] === '/')) i += 1;
      i += 2;
      out += ' ';
      continue;
    }
    if (c === '/' && src[i + 1] === '/') {
      i += 2;
      while (i < n && src[i] !== '\n') i += 1;
      out += ' ';
      continue;
    }
    out += c;
    i += 1;
  }
  return out;
}

function sanitizeOverpassBody(rawBody) {
  let params;
  try {
    params = new URLSearchParams(rawBody);
  } catch {
    return { ok: false, error: 'Malformed query body' };
  }
  const all = params.getAll('data');
  if (all.length !== 1)
    return { ok: false, error: 'Exactly one data query is required' };
  const data = all[0];
  if (!data || !data.trim())
    return { ok: false, error: 'Missing Overpass data query' };

  // Blank quoted literals + strip comments in one lexer pass so a fake bound or a
  // `//` inside a string can't hide an unbounded selector (or satisfy a bound).
  const stripped = stripOverpassNoise(data);

  // Reject oversized radii in EVERY around form — point `around:r,lat,lon` AND the
  // input-set form `around.set:r` — and parse the full numeric token so scientific
  // notation (`5e7`) can't slip a planet-scale radius past the cap.
  for (const m of stripped.matchAll(/around(?:\.\w+)?:\s*([\d.eE+-]+)/gi)) {
    const radius = Number(m[1]);
    if (!Number.isFinite(radius) || radius > OVERPASS_MAX_AROUND_M) {
      return { ok: false, error: 'Overpass around radius too large' };
    }
  }
  // Reject world-sized / oversized bboxes.
  for (const m of stripped.matchAll(
    /\(\s*(-?\d+(?:\.\d+)?)\s*,\s*(-?\d+(?:\.\d+)?)\s*,\s*(-?\d+(?:\.\d+)?)\s*,\s*(-?\d+(?:\.\d+)?)\s*\)/g,
  )) {
    const s = Number(m[1]);
    const w = Number(m[2]);
    const n = Number(m[3]);
    const e = Number(m[4]);
    if (
      Math.abs(n - s) > OVERPASS_MAX_BBOX_DEG ||
      Math.abs(e - w) > OVERPASS_MAX_BBOX_DEG
    ) {
      return { ok: false, error: 'Overpass bbox too large' };
    }
  }

  // Reject control-flow constructs the app never uses — their set/bound semantics
  // are hard to validate statically. The app only uses plain selectors + is_in /
  // area / pivot / recursion, so this denylist closes loop/transform escape hatches.
  if (/\b(?:foreach|complete|retro|compare|convert|make)\b/i.test(stripped)) {
    return { ok: false, error: 'Unsupported Overpass construct' };
  }
  // `poly:` has unchecked extent and the app never uses it — reject outright
  // (position-independent, so tag filters can't hide it).
  if (/\bpoly\s*:/i.test(stripped)) {
    return { ok: false, error: 'Overpass poly filter not allowed' };
  }

  // Every selector statement must be individually bounded, WITH set provenance: a
  // set counts as a bound only if it was assigned (->.set) by an already-bounded
  // statement. So `way[...]->.a` (global assigned to a set) is rejected, while the
  // app's `is_in(...)->.a; area.a[...]` and `area(id)->.x; rel(pivot.x)` validate.
  const boundedSets = new Set();
  for (let stmt of stripped.split(';')) {
    stmt = stmt.trim();
    if (!stmt || stmt.startsWith('[') || /^out\b/.test(stmt)) continue;

    // Strip output-set assignments (NOT input bounds), then strip bracket tag
    // filters so a tag KEY/value (e.g. `way[is_in]`, `node[around]`) can never be
    // misread as a spatial bound. Bounds live in (...) / function calls / set
    // refs, never inside [...], so the probe loses nothing real.
    const outSets = [];
    const body = stmt.replace(/->\s*\.(\w+)/g, (_, name) => {
      outSets.push(name);
      return ' ';
    });
    const probe = body.replace(/\[[^\]]*\]/g, ' ');

    // Reject element-in-area scans on the TAG-STRIPPED probe, so a tag filter
    // between the selector and the area filter (way["highway"](area.a)) can't hide
    // it. An area has unbounded extent (could be a whole country); the app only
    // SELECTS admin areas (area.set) and pivots (rel(pivot.x)), never node/way/
    // relation(area...). The probe collapses tags so `way (area.a)` is caught.
    if (OVERPASS_AREA_ELEMENT_RE.test(probe)) {
      return {
        ok: false,
        error: 'Overpass area-bounded element selector not allowed',
      };
    }

    const hasSelector = OVERPASS_SELECTOR_RE.test(probe);
    const inputSets = [...probe.matchAll(/(?<!\d)\.([a-z_]\w*)/gi)].map(
      (m) => m[1],
    );
    const directBound =
      /around:\s*\d/.test(probe) ||
      OVERPASS_BBOX_RE.test(probe) ||
      /is_in\s*\(/.test(probe) || // is_in(lat,lon) — the function form only
      /\barea\s*\(/.test(probe); // area(id) — bounded as a set definition

    const setBound = inputSets.some((s) => boundedSets.has(s));
    const bounded = directBound || setBound;

    if (hasSelector && !bounded) {
      return { ok: false, error: 'Overpass query has an unbounded selector' };
    }
    // Only a bounded statement can mark its output sets as bounded.
    if (bounded) for (const name of outSets) boundedSets.add(name);
  }

  const clamped = data.replace(
    /\[timeout:\s*(\d+)\s*\]/gi,
    (_, n) =>
      `[timeout:${Math.min(Number(n) || OVERPASS_MAX_QL_TIMEOUT, OVERPASS_MAX_QL_TIMEOUT)}]`,
  );
  return { ok: true, body: `data=${encodeURIComponent(clamped)}` };
}

export { isOverpassBoundaryQuery, sanitizeOverpassBody };