dateKeys-dart/test/large_capsule.dart

// Capsules with a large content, made from the time_only fixtures as
// whoever knows their keys can (spec §36.1): PAYLOAD_AGE sealed again over
// another plaintext with the file key that I_PAYLOAD unwraps and the nonce
// of the fixture, and in format 3 CONTROL_CBOR sealed again with the L of
// the new BODY, with FK_TIME, which the release of the fixture unwraps. The
// streaming tests and tool/open_bench.dart open them. They read no file.
library;

import 'dart:typed_data';

import 'package:datekeys/datekeys.dart';
import 'package:datekeys/src/age.dart';
import 'package:datekeys/src/body.dart';
import 'package:datekeys/src/sha256.dart';
import 'package:datekeys/src/tlock.dart';

import 'age_support.dart' show streamSeal;

export 'age_support.dart' show pattern;

/// The parts of an age file: its header, its nonce and its STREAM.
({Uint8List header, Uint8List nonce, Uint8List stream}) ageParts(
  Uint8List file,
) {
  final h = parseAgeHeader(file).length;
  return (
    header: Uint8List.sublistView(file, 0, h),
    nonce: Uint8List.sublistView(file, h, h + 16),
    stream: Uint8List.sublistView(file, h + 16),
  );
}

/// The plaintext of the STREAM of [file] under [fileKey].
Uint8List openStream(Uint8List file, Uint8List fileKey) {
  final p = ageParts(file);
  final d = AgePayloadDecryptor(
    hkdfSha256(fileKey, p.nonce, 'payload'.codeUnits, 32),
  );
  final out = BytesBuilder(copy: false);
  for (final c in d.add(p.stream)) {
    out.add(c);
  }
  out.add(d.close());
  return out.takeBytes();
}

/// [file] with its STREAM sealed again over [plaintext], its header and its
/// nonce kept.
Uint8List resealStream(Uint8List file, Uint8List fileKey, Uint8List plaintext) {
  final p = ageParts(file);
  return concatBytes([
    p.header,
    p.nonce,
    streamSeal(fileKey, p.nonce, plaintext),
  ]);
}

/// The file key of PAYLOAD_AGE of [dkc], which [payloadIdentity] unwraps.
Uint8List payloadFileKey(Uint8List dkc, Uint8List payloadIdentity) {
  final payload = splitCapsule(dkc).payload;
  return X25519Identity(payloadIdentity)
      .unwrap(parseAgeHeader(payload).stanzas);
}

/// [dkc], a time_only fixture of format 1, with [content] as its content.
Uint8List withContent1(
  Uint8List dkc,
  Uint8List payloadIdentity,
  Uint8List content,
) {
  final s = splitCapsule(dkc);
  final fk = payloadFileKey(dkc, payloadIdentity);
  return concatBytes([
    s.preludeBytes,
    s.publicHeader,
    s.sealedControl!,
    resealStream(s.payload, fk, content),
  ]);
}

/// [dkc], a time_only fixture of format 3 opened by [release], with a BODY
/// of the files [files], each a path and its content, in the order of their
/// paths, its security area kept, and the control that declares its L.
Uint8List withFiles3(
  Uint8List dkc,
  Uint8List payloadIdentity,
  Release release,
  List<(String, Uint8List)> files,
) {
  final s = splitCapsule(dkc);
  final h = decodeHeader(s.publicHeader);
  final p = quicknet();
  final sealed = s.sealedControl!;
  final tlock = parseAgeHeader(sealed).stanzas.single;
  final fkTime = unwrapTlockStanza(
    p,
    h.dateKey.round,
    release,
    tlock.args,
    tlock.body,
  );
  final control = decodeControl(
    openStream(sealed, fkTime),
    CapsuleFormat.format3,
  );

  // The BODY of the fixture, for its security area and its salt.
  final fk = payloadFileKey(dkc, payloadIdentity);
  final old = openStream(s.payload, fk);
  final frame = parseBodyFrame(
    Uint8List.sublistView(old, 0, bodyFrameSize),
    control.payloadLength!,
  );
  final area = Uint8List.sublistView(
    old,
    bodyFrameSize,
    bodyFrameSize + frame.areaLen,
  );
  final oldHead = decodeHead(
    Uint8List.sublistView(
      old,
      bodyFrameSize + frame.areaLen,
      bodyFrameSize + frame.areaLen + frame.headLen,
    ),
  );
  var end = 0;
  final head = encodeHead(
    Head(
      salt: oldHead.salt,
      files: [
        for (final (path, content) in files)
          HeadFile(
            path: path,
            size: content.length,
            start: end,
            end: end += content.length,
            sha256: sha256(content),
          ),
      ],
    ),
  );
  final body = concatBytes([
    bodyFrameBytes(BodyFrame(frame.areaLen, frame.securityLen, head.length)),
    area,
    head,
    for (final (_, content) in files) content,
  ]);
  final l = body.length;
  final padded = paddedLength(l, control.padding!);
  final newControl = encodeControl(
    Control(
      headerBinding: control.headerBinding,
      payloadIdentity: control.payloadIdentity,
      critical: control.critical,
      noncritical: control.noncritical,
      payloadLength: l,
      padding: control.padding,
    ),
    CapsuleFormat.format3,
  );
  return concatBytes([
    s.preludeBytes,
    s.publicHeader,
    resealStream(sealed, fkTime, newControl),
    resealStream(s.payload, fk, concatBytes([body, Uint8List(padded - l)])),
  ]);
}