Class: Decidim::Initiatives::PdfSignatureExample

Inherits:
Object
  • Object
show all
Defined in:
app/services/decidim/initiatives/pdf_signature_example.rb

Overview

Example of service to add a signature to a pdf

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(args = {}) ⇒ PdfSignatureExample

Public: Initializes the service. pdf - The pdf document to be signed



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# File 'app/services/decidim/initiatives/pdf_signature_example.rb', line 14

def initialize(args = {})
  @pdf = args.fetch(:pdf)
end

Instance Attribute Details

#pdf ⇒ Object

Returns the value of attribute pdf.



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# File 'app/services/decidim/initiatives/pdf_signature_example.rb', line 10

def pdf
  @pdf
end

Instance Method Details

#signed_pdf ⇒ Object

Public: PDF signed using a new certificate generated by the service



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# File 'app/services/decidim/initiatives/pdf_signature_example.rb', line 19

def signed_pdf
  signed_file = Tempfile.new("signed_pdf")

  doc = HexaPDF::Document.new(io: StringIO.new(pdf))

  # Prepare the document for embedding of the digital signature
  data = nil # Used for storing the to-be-signed data
  signing_mechanism = lambda do |io, byte_range|
    # Store the to-be-signed data in the local variable data
    io.pos = byte_range[0]
    data = io.read(byte_range[1])
    io.pos = byte_range[2]
    data << io.read(byte_range[3])
    ""
  end
  doc.sign(signed_file.path, signature: signature_widget(doc), reason: caption, signature_size: 10_000, external_signing: signing_mechanism)

  signature = OpenSSL::PKCS7.sign(certificate, key, data,
                                  # [HexaPDF.demo_cert.sub_ca, HexaPDF.demo_cert.root_ca],
                                  [],
                                  OpenSSL::PKCS7::DETACHED | OpenSSL::PKCS7::BINARY).to_der

  # Embed the signature
  HexaPDF::DigitalSignature::Signing.embed_signature(File.open(signed_file.path, "rb+"), signature)

  File.binread(signed_file.path)
ensure
  signed_file.close
  signed_file.unlink
end