mdg-filius/packages/fls/test/dnsHosts.test.ts

// Java's reading of /dns/hosts (DNSServer.leseRecordListe): every case in
// dns-hosts.cases.txt was run through Java (dns-hosts.java.json) and through
// Swift's hosts-file codec (dns-hosts.swift.json, tools/swift-oracle). The
// reader must match Java except where Java errs (JAVA_BUGS); the records the
// model keeps must match Swift except where Java's format says otherwise —
// each case named below.

import { readFileSync } from 'node:fs';
import { dirname, join } from 'node:path';
import { fileURLToPath } from 'node:url';
import { describe, expect, it } from 'vitest';
import { dnsRecordsOf, readDnsHosts } from '../src/dnsHosts.js';

const here = dirname(fileURLToPath(import.meta.url));
type Row = [string, string, number, string];
const javaMeasured = JSON.parse(readFileSync(join(here, 'dns-hosts.java.json'), 'utf8')) as [string, Row[]][];
const swiftMeasured = JSON.parse(readFileSync(join(here, 'dns-hosts.swift.json'), 'utf8')) as [string, Row[]][];

/** The cases file's escapes: a backslash, `u` and four hex digits for one UTF-16 unit. */
function unescape(line: string): string {
  return line.replace(/\\u([0-9a-fA-F]{4})/g, (_, hex: string) => String.fromCharCode(Number.parseInt(hex, 16)));
}

function modelRows(line: string, warnings: string[] = []): Row[] {
  return dnsRecordsOf(readDnsHosts(unescape(line)), (message) => warnings.push(message)).map((record) => [
    record.name,
    record.type,
    record.ttlSeconds,
    record.target,
  ]);
}

/** Lines Swift reads as records that Java never answers. */
const SWIFT_READS_JAVA_NEVER_ANSWERS: { reason: string; lines: string[] }[] = [
  {
    reason: 'Java splits fields at single spaces only: a tab or NBSP is part of a field',
    lines: [
      String.raw`www.filius.de\u0009A\u00093600\u00091.2.3.4\u000A`,
      String.raw`www.filius.de\u00A0A 3600 1.2.3.4\u000A`,
      String.raw`www.filius.de A 3600 1.2.3.4\u00A0\u000A`,
      String.raw`www.filius.de \u0009 A 3600 1.2.3.4\u000A`,
      String.raw`www.filius.de A \u0009 3600 1.2.3.4\u000A`,
    ],
  },
  {
    reason: 'Java splits lines at LF only: CR, LS and NEL stay in the line',
    lines: [
      String.raw`www.filius.de A 3600 1.2.3.4\u000Dmail.filius.de A 3600 1.2.3.5\u000D`,
      String.raw`www.filius.de A 3600 1.2.3.4\u2028mail.filius.de A 3600 1.2.3.5\u000A`,
      String.raw`www.filius.de A 3600 1.2.3.4\u0085\u000A`,
    ],
  },
  {
    reason: 'Java has no comments, no "IN" and no zone-file order',
    lines: [
      String.raw`www.filius.de A 3600 1.2.3.4#x\u000A`,
      String.raw`www.filius.de A IN 3600 1.2.3.4\u000A`,
      String.raw`www.filius.de 3600 IN A 1.2.3.4\u000A`,
    ],
  },
  {
    reason: 'two final dots make the name empty in Java',
    lines: [String.raw`www.filius.de.. A 3600 1.2.3.4\u000A`],
  },
  {
    reason: 'an MX or NS target must be a name Java accepts: no preference, no address, one final dot',
    lines: [
      String.raw`filius.de MX 3600 10 mail.filius.de\u000A`,
      String.raw`filius.de MX 3600 1.2.3.4\u000A`,
      String.raw`filius.de NS 3600 dns.filius.de..\u000A`,
    ],
  },
];

/** Lines Java answers that Swift drops or reads otherwise. */
const JAVA_ANSWERS_SWIFT_DROPS: { reason: string; lines: string[] }[] = [
  {
    reason: 'a TTL that is no number, or a negative one, is 3600',
    lines: [
      String.raw`www.filius.de A x 1.2.3.4\u000A`,
      String.raw`www.filius.de A 4294967295 1.2.3.4\u000A`,
      String.raw`www.filius.de A 99999999999 1.2.3.4\u000A`,
      String.raw`www.filius.de A 2147483648 1.2.3.4\u000A`,
      String.raw`www.filius.de A -5 1.2.3.4\u000A`,
      String.raw`www.filius.de A -2147483648 1.2.3.4\u000A`,
    ],
  },
  {
    reason: "a TTL is read by Java's Integer.parseInt, in any script's digits",
    lines: [String.raw`www.filius.de A \u0661\u0660 1.2.3.4\u000A`],
  },
  {
    reason: 'Java trims control characters off a line (String.trim)',
    lines: [
      String.raw`www.filius.de A 3600 1.2.3.4\u0001\u000A`,
      String.raw`\u001Fwww.filius.de A 3600 1.2.3.4\u000A`,
    ],
  },
  {
    reason: 'an NS record may name the root',
    lines: [
      String.raw`de. NS 3600 .\u000A`,
    ],
  },
  {
    reason: 'duplicates stay, as in Java\'s list',
    lines: [
      String.raw`www.filius.de A 3600 1.2.3.4\u000Awww.filius.de A 3600 1.2.3.4\u000A`,
      String.raw`www.filius.de A 3600 1.2.3.4\u000Awww.filius.de A 7200 1.2.3.4\u000A`,
      String.raw`www.filius.de A 3600 1.2.3.4\u000AWWW.filius.de. A 3600 1.2.3.4\u000A`,
    ],
  },
];

/** Lines where Java errs and this reader does not (see dnsHosts.ts). */
const JAVA_BUGS: { reason: string; lines: string[] }[] = [
  {
    reason: 'a label may start with a digit (RFC 1123); Java empties the name',
    lines: [String.raw`1und1.de A 3600 1.2.3.4\u000A`, String.raw`www.1und1.de A 3600 1.2.3.4\u000A`],
  },
  {
    reason: "a label holds no backslash; Java's pattern lets one in after the first label",
    lines: [String.raw`www.a\u005Cb.de A 3600 1.2.3.4\u000A`],
  },
  {
    reason: 'the type is read in any case (RFC 4343); Java never answers "a" or "mx"',
    lines: [String.raw`www.filius.de a 3600 1.2.3.4\u000A`, String.raw`filius.de mx 3600 mail.filius.de\u000A`],
  },
  {
    reason: 'a negative TTL is invalid (RFC 2181) and so 3600; Java keeps it',
    lines: [String.raw`www.filius.de A -5 1.2.3.4\u000A`, String.raw`www.filius.de A -2147483648 1.2.3.4\u000A`],
  },
];

const javaBugs = new Map(JAVA_BUGS.flatMap(({ reason, lines }) => lines.map((line) => [line, reason] as const)));

const departures = new Map(
  [...SWIFT_READS_JAVA_NEVER_ANSWERS, ...JAVA_ANSWERS_SWIFT_DROPS].flatMap(({ reason, lines }) =>
    lines.map((line) => [line, reason] as const),
  ),
);

describe('readDnsHosts against Java, but for its errors', () => {
  it('covers every line of the cases file, in both oracles', () => {
    const lines = readFileSync(join(here, 'dns-hosts.cases.txt'), 'ascii').split('\n').slice(0, -1);
    expect(javaMeasured.map(([line]) => line)).toEqual(lines);
    expect(swiftMeasured.map(([line]) => line)).toEqual(lines);
  });

  it('names only cases of the cases file as Java bugs', () => {
    const lines = new Set(javaMeasured.map(([line]) => line));
    expect([...javaBugs.keys()].filter((line) => !lines.has(line))).toEqual([]);
  });

  for (const [line, expected] of javaMeasured) {
    const bug = javaBugs.get(line);
    it(bug === undefined ? JSON.stringify(line) : `${JSON.stringify(line)} (Java errs: ${bug})`, () => {
      const records = readDnsHosts(unescape(line)).map((record) => [record.domainName, record.type, record.ttl, record.rdata]);
      if (bug === undefined) expect(records).toEqual(expected);
      else expect(records).not.toEqual(expected);
    });
  }
});

describe('the records the model keeps, against Swift', () => {
  it('names only cases of the cases file as departures', () => {
    const lines = new Set(swiftMeasured.map(([line]) => line));
    expect([...departures.keys()].filter((line) => !lines.has(line))).toEqual([]);
  });

  for (const [line, swift] of swiftMeasured) {
    const reason = departures.get(line);
    it(reason === undefined ? JSON.stringify(line) : `${JSON.stringify(line)} (departs: ${reason})`, () => {
      if (reason === undefined) expect(modelRows(line)).toEqual(swift);
      else expect(modelRows(line)).not.toEqual(swift);
    });
  }
});

describe('the records Java answers', () => {
  it('leave out records Java never answers: an empty name, or a type other than A, MX, NS', () => {
    expect(modelRows(String.raw`a_b.de A 3600 1.2.3.4\u000Afilius.de CNAME 3600 www.filius.de\u000A1.2.3.4 A 3600 1.2.3.4`)).toEqual([]);
  });

  it('read a name with a digit first and a type in any case, but no numeric last label', () => {
    expect(modelRows(String.raw`1und1.de a 60 1.2.3.4\u000A1und1.de Mx 60 mx.1und1.de\u000A1und1.de MX 60 10`)).toEqual([
      ['1und1.de', 'A', 60, '1.2.3.4'],
      ['1und1.de', 'MX', 60, 'mx.1und1.de.'],
    ]);
  });

  it('take names in lower case without the final dot, A targets as FILIUS normalises addresses', () => {
    expect(modelRows(String.raw`WWW.Filius.DE. A 60 010.000.0.1\u000Afilius.de MX 3600 Mail.Filius.DE\u000A. NS 3600 dns-root`)).toEqual([
      ['www.filius.de', 'A', 60, '10.0.0.1'],
      ['filius.de', 'MX', 3600, 'mail.filius.de.'],
      ['.', 'NS', 3600, 'dns-root.'],
    ]);
  });

  it('warn about an A record Java answers with an address FILIUS cannot use', () => {
    const warnings: string[] = [];
    expect(modelRows(String.raw`www.filius.de A 3600 .1.2.3`, warnings)).toEqual([]);
    expect(warnings).toEqual(["DNS record 'www.filius.de A .1.2.3' has no usable IPv4 address, left out (it stays in /dns/hosts)"]);
  });
});