Question

I’ve implemented a local script to insert digital signatures into local pdf files recurring to Origami, but don’t quite know what would be the best approach to do this within a rails server, and with amazon s3 stored files.

I am guessing i would need to download the file from s3 to my server (or capture it before uploading to amazon, which is what i am doing with paperclip) insert the signature, and sent it back to s3 again.

Here is the PDF.read method in pdf.rb file of origami solution:

 class << self

      #
      # Reads and parses a PDF file from disk.
      #
      def read(filename, options = {})
        filename = File.expand_path(filename) if filename.is_a?(::String)
        PDF::LinearParser.new(options).parse(filename)
      end

How could i adapt this so that i treat an in-memory binary file?

Do you have any suggestions?

You can find more about origami here

And my code below

require 'openssl'

begin
  require 'origami'
rescue LoadError
  ORIGAMIDIR = "C:\RailsInstaller\Ruby1.9.3\lib\ruby\gems\1.9.1\gems\origami-1.2.4\lib"
  $: << ORIGAMIDIR
  require 'origami'
end
include Origami

INPUTFILE = "Sample.pdf"
@inputfile = String.new(INPUTFILE)
OUTPUTFILE = @inputfile.insert(INPUTFILE.rindex("."),"_signed")
CERTFILE = "certificate.pem"
RSAKEYFILE = "private_key.pem"
passphrase = "your passphrase"

key4pem=File.read RSAKEYFILE

key = OpenSSL::PKey::RSA.new key4pem, passphrase
cert = OpenSSL::X509::Certificate.new(File.read CERTFILE)

pdf = PDF.read(INPUTFILE)
page = pdf.get_page(1)

# Add signature annotation (so it becomes visibles in pdf document)

sigannot = Annotation::Widget::Signature.new
sigannot.Rect = Rectangle[:llx => 89.0, :lly => 386.0, :urx => 190.0, :ury => 353.0]

page.add_annot(sigannot)

# Sign the PDF with the specified keys
pdf.sign(cert, key, 
  :method => 'adbe.pkcs7.sha1',
  :annotation => sigannot, 
  :location => "Portugal", 
  :contact => "[e-mail]", 
  :reason => "Proof of Concept"
)

# Save the resulting file
pdf.save(OUTPUTFILE)

Answer 1

PDF.read and PDF.save methods both accept either a file path or a Ruby IO object.

One method to create a PDF instance from a string (which, I suppose, is what you mean when you say “in-memory”) is to use a StringIO object.

For example, the following session in the Origami shell will create a PDF instance, save it to a StringIO object and reload it using its own output string.

>>> PDF.new.save(strio = StringIO.new)
...

>>> strio.string
"%PDF-1.0\r\n1 0 obj\r\n<<\r\n\t/Pages 2 0 R ..."

>>> strio.reopen(strio.string, 'r')
#<StringIO:0xffbea6cc>

>>> pdf = PDF.read(strio)
...

>>> pdf.class
Origami::PDF