process password protected pdf files

lib/pdf_utils.rb

@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+module PdfUtils
+  module_function
+
+  def encrypted?(data, password: nil)
+    HexaPDF::Document.new(io: StringIO.new(data), decryption_opts: { password: })
+
+    false
+  rescue HexaPDF::EncryptionError
+    true
+  end
+
+  def decrypt(data, password)
+    encrypted_doc = HexaPDF::Document.new(io: StringIO.new(data), decryption_opts: { password: })
+
+    decrypted_doc = HexaPDF::Document.new
+
+    encrypted_doc.pages.each do |page|
+      decrypted_doc.pages << decrypted_doc.import(page)
+    end
+
+    decrypted_io = StringIO.new
+
+    decrypted_doc.write(decrypted_io, validate: false)
+
+    decrypted_io.tap(&:rewind).read
+  end
+end

lib/templates/create_attachments.rb

@@ -5,6 +5,7 @@ module Templates
     PDF_CONTENT_TYPE = 'application/pdf'
     ANNOTATIONS_SIZE_LIMIT = 6.megabytes
     InvalidFileType = Class.new(StandardError)
+    PdfEncrypted = Class.new(StandardError)
 
     module_function
 
@@ -19,6 +20,15 @@ module Templates
         document = template.documents.create!(blob:)
 
         if blob.content_type == PDF_CONTENT_TYPE && blob.metadata['pdf'].nil?
+          data = maybe_decrypt_pdf_or_raise(document_data, params)
+
+          if data != document_data
+            blob = ActiveStorage::Blob.create_and_upload!(
+              io: StringIO.new(new_data), filename: blob.filename
+            )
+            document_data = data
+          end
+
           annotations =
             document_data.size > ANNOTATIONS_SIZE_LIMIT ? [] : Templates::BuildAnnotations.call(document_data)
 
@@ -41,6 +51,8 @@ module Templates
         data = file.read
 
         if file.content_type == PDF_CONTENT_TYPE
+          data = maybe_decrypt_pdf_or_raise(data, params)
+
           annotations = data.size > ANNOTATIONS_SIZE_LIMIT ? [] : Templates::BuildAnnotations.call(data)
           metadata = { 'identified' => true, 'analyzed' => true,
                        'sha256' => Base64.urlsafe_encode64(Digest::SHA256.digest(data)),
@@ -56,6 +68,16 @@ module Templates
       end
     end
 
+    def maybe_decrypt_pdf_or_raise(data, params)
+      if data.size < ANNOTATIONS_SIZE_LIMIT && PdfUtils.encrypted?(data)
+        PdfUtils.decrypt(data, params[:password])
+      else
+        data
+      end
+    rescue HexaPDF::EncryptionError
+      raise PdfEncrypted
+    end
+
     def handle_file_types(_document_data, blob)
       raise InvalidFileType, blob.content_type
     end