dateKeys-dart/test/securitycms_support.dart

// Helpers of the tests of the signatures of alg 2 and the seals of
// seal_type 2 against the vectors of Go: the areas of
// test/vectors/securitycms_vectors.json, which tool/security_go_vectors.go
// makes and evaluates with package capsule of the reference, put together
// again from their pieces, or from a base and its edit. They read no file,
// so that the tests that run on Node.js can use them.
library;

import 'dart:typed_data';

import 'package:datekeys/datekeys.dart';
import 'package:datekeys/src/sha256.dart' show sha256;

import 'open_vectors_support.dart';
import 'tlock_support.dart' show applyEdits;

/// The bytes of [pieces]: the hexadecimal of some bytes, or the index of a
/// chunk of [chunks].
Uint8List joinPieces(List<Object?> pieces, List<Uint8List> chunks) =>
    concatBytes([
      for (final p in pieces) p is int ? chunks[p] : fromHex(p! as String),
    ]);

/// The chunks of a vector file, each made of the ones before it.
List<Uint8List> chunksOf(Json f) {
  final out = <Uint8List>[];
  for (final c in (f['chunks']! as List).cast<Json>()) {
    out.add(joinPieces(c['pieces']! as List<Object?>, out));
  }
  return out;
}

/// The bases of the file, from their pieces, or their hexadecimal in the
/// part of the file that the tests compiled to JavaScript read.
List<Uint8List> basesOf(Json f, List<Uint8List> chunks) => [
  for (final b in f['bases']! as List)
    b is String
        ? fromHex(b)
        : joinPieces((b as Json)['pieces']! as List<Object?>, chunks),
];

/// The area of the case [c]: its hexadecimal, its pieces, or its base with
/// the edit of its target, the SignedData of key 2 (value), its SIGNERS
/// (signers) or the token of key 3 (token), written again with the
/// encoders of this library as Go writes it with those of capsule. The
/// first 8 bytes of its SHA-256 must be those of Go's.
Uint8List cmsAreaOf(Json c, List<Uint8List> chunks, List<Uint8List> bases) {
  final Uint8List area;
  final hex = c['hex'] as String?;
  final pieces = c['pieces'] as List<Object?>?;
  if (hex != null) {
    area = fromHex(hex);
  } else if (pieces != null) {
    area = joinPieces(pieces, chunks);
  } else {
    final w = decodeSecurity(bases[c['base']! as int])!;
    final edits = (c['edits']! as List).cast<Object?>();
    var signature = w.signature;
    var seal = w.seal;
    switch (c['target']) {
      case 'value' || 'signers':
        final a = decodeAuthorSignature(signature!)!;
        final value = c['target'] == 'value';
        signature = encodeAuthorSignature(
          algCms,
          value ? a.key : applyEdits(a.key, edits),
          value ? applyEdits(a.value, edits) : a.value,
        );
      case 'token':
        final s = decodeSeal(seal!)!;
        seal = encodeSeal(sealTypeRfc3161, applyEdits(s.token, edits));
      default:
        throw StateError('a target ${c['target']}');
    }
    area = encodeSecurityWith(signature: signature, seal: seal);
  }
  if (toHex(sha256(area).sublist(0, 8)) != c['sha256']) {
    throw StateError('the area of ${canonical(c)} is not the one of Go');
  }
  return area;
}