Class: PQCrypto::Seal::Format::HeaderCodec

Inherits:
Object
  • Object
show all
Defined in:
lib/pq_crypto/seal/format.rb

Class Method Summary collapse

Class Method Details

.build(payload_id:, payload_nonce:, recipient_capacity:, slot_size:, padded_inner_length:, public_metadata:, padding_policy_id:) ⇒ Object

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# File 'lib/pq_crypto/seal/format.rb', line 84

def build(payload_id:, payload_nonce:, recipient_capacity:, slot_size:,
          padded_inner_length:, public_metadata:, padding_policy_id:)
  public_metadata = String(public_metadata).b
  validate_build_input!(
    payload_id, payload_nonce, public_metadata, padding_policy_id
  )

  body = [
    Binary.u16(CONTENT_SUITE_AEGIS256),
    Binary.u8(LOOKUP_HINT),
    Binary.u16(FLAGS),
    Binary.u8(padding_policy_id),
    payload_id,
    payload_nonce,
    Binary.u16(recipient_capacity),
    Binary.u16(slot_size),
    Binary.u64(padded_inner_length),
    Binary.u32(public_metadata.bytesize),
    public_metadata
  ].join.b

  header = MAGIC + Binary.u8(VERSION) + Binary.u32(HEADER_PREFIX_BYTES + body.bytesize) + body
  raise InvalidConfigurationError, "header is too large" if header.bytesize > MAX_HEADER_BYTES

  header
end

.parse(bytes) ⇒ Object

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# File 'lib/pq_crypto/seal/format.rb', line 111

def parse(bytes)
  source = String(bytes).b
  prefix = Binary::Reader.new(source)
  expect!(prefix.bytes(MAGIC.bytesize), MAGIC, "invalid envelope magic")
  expect!(prefix.u8, VERSION, "unsupported format version")
  header_length = prefix.u32
  validate_header_length!(header_length, prefix.offset)

  Binary.ensure_available!(source, 0, header_length)
  raw = source.byteslice(0, header_length).b
  fields = Binary::Reader.new(raw, prefix.offset)

  content_suite = fields.u16
  expect_suite!(content_suite, CONTENT_SUITE_AEGIS256, "content")
  lookup_mode = fields.u8
  expect_suite!(lookup_mode, LOOKUP_HINT, "lookup mode")
  flags = fields.u16
  expect!(flags, FLAGS, "unknown header flags")
  padding_policy_id = Format.validate_padding_policy_id!(fields.u8, error: FormatError)
  payload_id = fields.bytes(PAYLOAD_ID_BYTES)
  payload_nonce = fields.bytes(NONCE_BYTES)
  capacity = Format.validate_capacity!(fields.u16, error: FormatError)
  slot_size = Format.validate_slot_size!(fields.u16, error: FormatError)
  padded_inner_length = fields.u64
  raise FormatError, "padded inner frame is too short" if padded_inner_length < INNER_PREFIX_BYTES

  public_length = fields.u32
  raise FormatError, "public metadata is too large" if public_length > MAX_PUBLIC_METADATA_BYTES
  public_metadata = fields.bytes(public_length)
  raise FormatError, "non-canonical header length" unless fields.finished?

  Header.new(
    raw: raw,
    content_suite_id: content_suite,
    lookup_mode: lookup_mode,
    flags: flags,
    padding_policy_id: padding_policy_id,
    payload_id: payload_id,
    payload_nonce: payload_nonce,
    recipient_capacity: capacity,
    slot_size: slot_size,
    padded_inner_length: padded_inner_length,
    public_metadata: public_metadata
  )
end