Module: Rubrik::FillSignature

Extended by:
FillSignature, T::Sig
Includes:
Kernel
Included in:
FillSignature
Defined in:
lib/rubrik/fill_signature.rb

Constant Summary collapse

FIRST_OFFSET = 
0

Instance Method Summary collapse

Instance Method Details

#call(io, signature_value_ref:, private_key:, certificate:, certificate_chain: []) ⇒ Object 



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# File 'lib/rubrik/fill_signature.rb', line 20

def call(io, signature_value_ref:, private_key:, certificate:, certificate_chain: [])
  io.rewind

  signature_value_offset = PDF::Reader::XRef.new(io)[signature_value_ref]

  io.pos = signature_value_offset
  io.gets("/Contents")
  io.gets("<")

  first_length = io.pos - 1
  # We need to sum +2 to account for "<" and ">" of the hex string
  second_offset = first_length + Document::SIGNATURE_SIZE + 2
  second_length = io.size - second_offset

  byte_range_array = [FIRST_OFFSET, first_length, second_offset, second_length]

  io.pos = signature_value_offset

  io.gets("/ByteRange")
  byte_range_start = io.pos - "/ByteRange".size

  io.gets("]")
  byte_range_end = io.pos

  byte_range_size = byte_range_end - byte_range_start + 1
  actual_byte_range = " /ByteRange [#{byte_range_array.join(" ")}]".ljust(byte_range_size, " ")

  io.seek(-byte_range_size, IO::SEEK_CUR)
  io.write(actual_byte_range)

  io.pos = FIRST_OFFSET
  data_to_sign = T.must(io.read(first_length))

  io.pos = second_offset
  data_to_sign += T.must(io.read(second_length))

  signature = PKCS7Signature.call(data_to_sign, private_key:, certificate:)
  hex_signature = T.let(signature, String).unpack1("H*")

  padded_contents_field = "<#{hex_signature.ljust(Document::SIGNATURE_SIZE, "0")}>"

  io.pos = first_length
  io.write(padded_contents_field)

  io.rewind
  io
end