Class: Axlsx::MsOffCrypto

Inherits:
Object
  • Object
show all
Defined in:
lib/axlsx/util/ms_off_crypto.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(password = "passowrd") ⇒ MsOffCrypto

Returns a new instance of MsOffCrypto.



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# File 'lib/axlsx/util/ms_off_crypto.rb', line 10

def initialize(password = "passowrd")
  @password = password
  @salt_size = 0x10
  @key_size = 0x100
  @verifier = rand(16**16).to_s 

  #fixed salt for testing
  @salt = [0x90,0xAC,0x68,0x0E,0x76,0xF9,0x43,0x2B,0x8D,0x13,0xB7,0x1D,0xB7,0xC0,0xFC,0x0D].join
  # @salt =Digest::SHA1.digest(rand(16**16).to_s)
end

Instance Attribute Details

#key ⇒ Object (readonly)

2.3.4.7 ECMA-376 Document Encryption Key Generation (Standard Encryption)



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# File 'lib/axlsx/util/ms_off_crypto.rb', line 57

def key
  @key
end

#verifier ⇒ Object (readonly)

Returns the value of attribute verifier.



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# File 'lib/axlsx/util/ms_off_crypto.rb', line 7

def verifier
  @verifier
end

Instance Method Details

#decrypt(data) ⇒ Object 



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# File 'lib/axlsx/util/ms_off_crypto.rb', line 80

def decrypt(data)
  aes = OpenSSL::Cipher.new("AES-128-ECB")     
  aes.decrypt
  aes.key = key
  aes.update(data)
end

#encrypt(data) ⇒ Object 



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# File 'lib/axlsx/util/ms_off_crypto.rb', line 73

def encrypt(data)
  aes = OpenSSL::Cipher.new("AES-128-ECB")     
  aes.encrypt
  aes.key = key
  aes.update(data)
end

#encrypted_verifier ⇒ Object

2.3.3



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# File 'lib/axlsx/util/ms_off_crypto.rb', line 45

def encrypted_verifier
  @encrypted_verifier ||= encrypt(@verifier)
end

#encrypted_verifier_hash ⇒ Object

2.3.3



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# File 'lib/axlsx/util/ms_off_crypto.rb', line 50

def encrypted_verifier_hash
  verifier_hash = Digest::SHA1.digest(@verifier)
  verifier_hash << Array.new(32 - verifier_hash.size, 0).join('')
  @encrypted_verifier_hash ||= encrypt(verifier_hash)
end

#encryption_info ⇒ Object 



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# File 'lib/axlsx/util/ms_off_crypto.rb', line 21

def encryption_info
  #         v.major v.minor flags           header length   flags           size            # AES 128 bit
  header = [3, 0, 2, 0, 0x24, 0, 0, 0, 0xA4, 0, 0, 0, 0x24, 0, 0, 0, 0, 0, 0, 0, 0x0E, 0x66, 0, 0]
  header.concat [0x04, 0x80, 0, 0, 0x80, 0, 0, 0, 0x18, 0, 0, 0, 0xA0, 0xC7, 0xDC, 0x2, 0, 0, 0, 0]
  header.concat "Microsoft Enhanced RSA and AES Cryptographic Provider (Prototype)".bytes.to_a.pack('s*').bytes.to_a
  header.concat [0, 0]
  header.concat [0x10, 0, 0, 0]
  header.concat [0x90,0xAC,0x68,0x0E,0x76,0xF9,0x43,0x2B,0x8D,0x13,0xB7,0x1D,0xB7,0xC0,0xFC,0x0D]
  header.concat encrypted_verifier.bytes.to_a.pack('c*').bytes.to_a
  header.concat [20, 0,0,0]
  header.concat encrypted_verifier_hash.bytes.to_a.pack('c*').bytes.to_a
  header.flatten!
  header.pack('c*')
end

#encryption_verifier ⇒ Object 



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# File 'lib/axlsx/util/ms_off_crypto.rb', line 36

def encryption_verifier
  {:salt_size => @salt_size, 
   :salt => @salt, 
   :encrypted_verifier => encrypted_verifier,
   :varifier_hash_size => 0x14,
    :encrypted_verifier_hash =>  encrypted_verifier_hash}
end

#verify_password ⇒ Object 



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# File 'lib/axlsx/util/ms_off_crypto.rb', line 69

def verify_password
  puts decrypt(@encrypted_verifier)
end