Create a signed PDF using Ruby or Ruby on Rails

Question

I am working on a Rails application that uses shrimp to create PDF files. In short, we want to be able to digitally sign generated PDF files. I'm not sure where to start reading for sure. I just wanted to ask if anyone else could have done this before, and if so, what resources should I use for this.

Thank!

Answer 1

I would advise you to take a look at https://github.com/joseicosta/odf-report . This is a gem for creating ODFs, but they can easily be converted to PDF, plus it supports templates.

Answer 2

Although this question has an answer and is quite old, I would like to add an appropriate link for information.

MrWater shared his code with Insert Digital Signature into an Existing PDF File .

VERSION 1 - Create a certificate and key file and paste them directly into the document

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

# Code below is based on documentation available on
# http://www.ruby-doc.org/stdlib-1.9.3/libdoc/openssl/rdoc/OpenSSL.html
key = OpenSSL::PKey::RSA.new 2048

open 'private_key.pem', 'w' do |io| io.write key.to_pem end
open 'public_key.pem', 'w' do |io| io.write key.public_key.to_pem end

cipher = OpenSSL::Cipher::Cipher.new 'AES-128-CBC'
pass_phrase = 'Origami rocks'

key_secure = key.export cipher, pass_phrase

open 'private_key.pem', 'w' do |io|
  io.write key_secure
end

#Create the certificate

name = OpenSSL::X509::Name.parse 'CN=nobody/DC=example'

cert = OpenSSL::X509::Certificate.new
cert.version = 2
cert.serial = 0
cert.not_before = Time.now
cert.not_after = Time.now + 3600

cert.public_key = key.public_key
cert.subject = name


OUTPUTFILE = "test.pdf"

contents = ContentStream.new.setFilter(:FlateDecode)
contents.write OUTPUTFILE,
  :x => 350, :y => 750, :rendering => Text::Rendering::STROKE, :size => 30

pdf = PDF.read('Sample.pdf')


# Open certificate files

#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)

VERSION 2 - Use of existing certificates for signing a PDF document

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)