Add bin and edit workflow

bin/gems/pdf-reader-2.14.1/lib/pdf/reader/key_builder_v5.rb

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+# coding: utf-8
+# typed: strict
+# frozen_string_literal: true
+
+require 'digest/md5'
+require 'rc4'
+
+class PDF::Reader
+
+  # Processes the Encrypt dict from an encrypted PDF and a user provided
+  # password and returns a key that can decrypt the file.
+  #
+  # This can generate a decryption key compatible with the following standard encryption algorithms:
+  #
+  # * Version 5 (AESV3)
+  #
+  class KeyBuilderV5
+
+    def initialize(opts = {})
+      @key_length   = 256
+
+      # hash(32B) + validation salt(8B) + key salt(8B)
+      @owner_key    = opts[:owner_key] || ""
+
+      # hash(32B) + validation salt(8B) + key salt(8B)
+      @user_key     = opts[:user_key] || ""
+
+      # decryption key, encrypted w/ owner password
+      @owner_encryption_key = opts[:owner_encryption_key] || ""
+
+      # decryption key, encrypted w/ user password
+      @user_encryption_key  = opts[:user_encryption_key] || ""
+    end
+
+    # Takes a string containing a user provided password.
+    #
+    # If the password matches the file, then a string containing a key suitable for
+    # decrypting the file will be returned. If the password doesn't match the file,
+    # and exception will be raised.
+    #
+    def key(pass)
+      pass = pass.byteslice(0...127).to_s   # UTF-8 encoded password. first 127 bytes
+
+      encrypt_key   = auth_owner_pass(pass)
+      encrypt_key ||= auth_user_pass(pass)
+      encrypt_key ||= auth_owner_pass_r6(pass)
+      encrypt_key ||= auth_user_pass_r6(pass)
+
+      raise PDF::Reader::EncryptedPDFError, "Invalid password (#{pass})" if encrypt_key.nil?
+      encrypt_key
+    end
+
+    private
+
+    # Algorithm 3.2a - Computing an encryption key
+    #
+    # Defined in PDF 1.7 Extension Level 3
+    #
+    # if the string is a valid user/owner password, this will return the decryption key
+    #
+    def auth_owner_pass(password)
+      if Digest::SHA256.digest(password + @owner_key[32..39] + @user_key) == @owner_key[0..31]
+        cipher = OpenSSL::Cipher.new('AES-256-CBC')
+        cipher.decrypt
+        cipher.key = Digest::SHA256.digest(password + @owner_key[40..-1] + @user_key)
+        cipher.iv = "\x00" * 16
+        cipher.padding = 0
+        cipher.update(@owner_encryption_key) + cipher.final
+      end
+    end
+
+    def auth_user_pass(password)
+      if Digest::SHA256.digest(password + @user_key[32..39]) == @user_key[0..31]
+        cipher = OpenSSL::Cipher.new('AES-256-CBC')
+        cipher.decrypt
+        cipher.key = Digest::SHA256.digest(password + @user_key[40..-1])
+        cipher.iv = "\x00" * 16
+        cipher.padding = 0
+        cipher.update(@user_encryption_key) + cipher.final
+      end
+    end
+
+    def auth_owner_pass_r6(password)
+      if r6_digest(password, @owner_key[32..39].to_s, @user_key[0,48].to_s) == @owner_key[0..31]
+        cipher = OpenSSL::Cipher.new('AES-256-CBC')
+        cipher.decrypt
+        cipher.key = r6_digest(password, @owner_key[40,8].to_s, @user_key[0, 48].to_s)
+        cipher.iv = "\x00" * 16
+        cipher.padding = 0
+        cipher.update(@owner_encryption_key) + cipher.final
+      end
+    end
+
+    def auth_user_pass_r6(password)
+      if r6_digest(password, @user_key[32..39].to_s) == @user_key[0..31]
+        cipher = OpenSSL::Cipher.new('AES-256-CBC')
+        cipher.decrypt
+        cipher.key = r6_digest(password, @user_key[40,8].to_s)
+        cipher.iv = "\x00" * 16
+        cipher.padding = 0
+        cipher.update(@user_encryption_key) + cipher.final
+      end
+    end
+
+    # PDF 2.0 spec, 7.6.4.3.4
+    # Algorithm 2.B: Computing a hash (revision 6 and later)
+    def r6_digest(password, salt, user_key = '')
+      k = Digest::SHA256.digest(password + salt + user_key)
+      e = ''
+
+      i = 0
+      while i < 64 or e.getbyte(-1).to_i > i - 32
+        k1 = (password + k + user_key) * 64
+
+        aes = OpenSSL::Cipher.new("aes-128-cbc").encrypt
+        aes.key = k[0, 16].to_s
+        aes.iv = k[16, 16].to_s
+        aes.padding = 0
+        e = String.new(aes.update(k1))
+        k = case unpack_128bit_bigendian_int(e) % 3
+            when 0 then Digest::SHA256.digest(e)
+            when 1 then Digest::SHA384.digest(e)
+            when 2 then Digest::SHA512.digest(e)
+            end
+        i = i + 1
+      end
+
+      k[0, 32].to_s
+    end
+
+    def unpack_128bit_bigendian_int(str)
+      ints = str[0,16].to_s.unpack("N*")
+      (ints[0].to_i << 96) + (ints[1].to_i << 64) + (ints[2].to_i << 32) + ints[3].to_i
+    end
+
+  end
+end
+