Class: Zip::AESDecrypter

Inherits:
Decrypter show all
Includes:
AESEncryption
Defined in:
lib/zip/crypto/aes_encryption.rb

Overview

:nodoc:

Constant Summary

Constants included from AESEncryption

Zip::AESEncryption::AUTHENTICATION_CODE_LENGTH, Zip::AESEncryption::BITS, Zip::AESEncryption::BLOCK_SIZE, Zip::AESEncryption::KEY_LENGTHS, Zip::AESEncryption::SALT_LENGTHS, Zip::AESEncryption::STRENGTHS, Zip::AESEncryption::STRENGTH_128_BIT, Zip::AESEncryption::STRENGTH_192_BIT, Zip::AESEncryption::STRENGTH_256_BIT, Zip::AESEncryption::VERIFIER_LENGTH, Zip::AESEncryption::VERSIONS, Zip::AESEncryption::VERSION_AE_1, Zip::AESEncryption::VERSION_AE_2

Instance Method Summary collapse

Methods included from AESEncryption

#gp_flags, #header_bytesize, #initialize

Instance Method Details

#check_integrity!(io) ⇒ Object

Raises:



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# File 'lib/zip/crypto/aes_encryption.rb', line 208

def check_integrity!(io)
  auth_code = io.read(AUTHENTICATION_CODE_LENGTH)
  raise Error, 'Integrity fault' if @hmac.digest[0...AUTHENTICATION_CODE_LENGTH] != auth_code
end

#decrypt(encrypted_data) ⇒ Object 



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# File 'lib/zip/crypto/aes_encryption.rb', line 171

def decrypt(encrypted_data)
  @hmac.update(encrypted_data)

  idx = 0
  decrypted_data = +''
  amount_to_read = encrypted_data.size

  while amount_to_read.positive?
    @cipher.iv = [@counter + 1].pack('Vx12')
    begin_index = BLOCK_SIZE * idx
    end_index = begin_index + [BLOCK_SIZE, amount_to_read].min
    decrypted_data << @cipher.update(encrypted_data[begin_index...end_index])
    amount_to_read -= BLOCK_SIZE
    @counter += 1
    idx += 1
  end

  # JRuby requires finalization of the cipher. This is a bug, as noted in
  # jruby/jruby-openssl#182 and jruby/jruby-openssl#183.
  decrypted_data << @cipher.final if defined?(JRUBY_VERSION)
  decrypted_data
end

#reset!(header) ⇒ Object

Raises:



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# File 'lib/zip/crypto/aes_encryption.rb', line 194

def reset!(header)
  salt = header[0...@salt_length]
  pwd_verify = header[-VERIFIER_LENGTH..]
  enc_key, enc_hmac_key, enc_pwd_verify = derive_keys(salt)

  raise Error, 'Bad password' if enc_pwd_verify != pwd_verify

  @counter = 0
  @cipher = OpenSSL::Cipher::AES.new(@bits, :CTR)
  @cipher.decrypt
  @cipher.key = enc_key
  @hmac = OpenSSL::HMAC.new(enc_hmac_key, OpenSSL::Digest.new('SHA1'))
end