Class: RubyRNCryptor

Inherits:
Object
  • Object
show all
Includes:
OpenSSL
Defined in:
lib/ruby_rncryptor.rb

Class Method Summary collapse

Class Method Details

.decrypt(data, password) ⇒ Object 



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# File 'lib/ruby_rncryptor.rb', line 12

def self.decrypt(data, password)

  version =      data[0,1]
  raise "RubyRNCryptor only decrypts version 2 or 3" unless (version == "\x02" || version == "\x03")
  options =      data[1,1]
  encryption_salt =  data[2,8]
  hmac_salt =      data[10,8]
  iv =       data[18,16]
  cipher_text =    data[34,data.length-66]
  hmac =       data[data.length-32,32]

  msg = version + options + encryption_salt + hmac_salt + iv + cipher_text

  # Verify password is correct. First try with correct encoding
  hmac_key = PKCS5.pbkdf2_hmac_sha1(password, hmac_salt, 10000, 32)
  verified = eql_time_cmp([HMAC.hexdigest('sha256', hmac_key, msg)].pack('H*'), hmac)

  if !verified && version == "\x02"
    # Version 2 Cocoa version truncated multibyte passwords, so try truncating.
    password = RubyRNCryptor.truncate_multibyte_password(password)
    hmac_key = PKCS5.pbkdf2_hmac_sha1(password, hmac_salt, 10000, 32)
    verified = eql_time_cmp([HMAC.hexdigest('sha256', hmac_key, msg)].pack('H*'), hmac)
  end

  raise "Password may be incorrect, or the data has been corrupted. (HMAC could not be verified)" unless verified

  # HMAC was verified, now decrypt it.
  cipher = Cipher.new('aes-256-cbc')
  cipher.decrypt
  cipher.iv = iv
  cipher.key = PKCS5.pbkdf2_hmac_sha1(password, encryption_salt, 10000, 32)

  cipher.update(cipher_text) + cipher.final
end

.encrypt(data, password, version = 3) ⇒ Object 



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# File 'lib/ruby_rncryptor.rb', line 47

def self.encrypt(data, password, version = 3)

  raise "RubyRNCryptor only encrypts version 2 or 3" unless (version == 2 || version == 3)

  version =      version.chr.to_s   # Currently version 3
  options =      1.chr.to_s       # Uses password
  encryption_salt =  SecureRandom.random_bytes(8)
  hmac_salt =      SecureRandom.random_bytes(8)
  iv =       SecureRandom.random_bytes(16)
  cipher_text =    data[34,data.length-66]

  hmac_key = PKCS5.pbkdf2_hmac_sha1(password, hmac_salt, 10000, 32)

  cipher = Cipher.new('aes-256-cbc')
  cipher.encrypt
  cipher.iv = iv
  cipher.key = PKCS5.pbkdf2_hmac_sha1(password, encryption_salt, 10000, 32)
  cipher_text = cipher.update(data) + cipher.final

  msg = version + options + encryption_salt + hmac_salt + iv + cipher_text
  hmac = [HMAC.hexdigest('sha256', hmac_key, msg)].pack('H*')

  msg + hmac
end

.eql_time_cmp(a, b) ⇒ Object

From ruby-doc.org/stdlib-2.0.0/libdoc/openssl/rdoc/OpenSSL/PKCS5.html#module-OpenSSL::PKCS5-label-Important+Note+on+Checking+Passwords



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# File 'lib/ruby_rncryptor.rb', line 80

def self.eql_time_cmp(a, b)
  unless a.length == b.length
    return false
  end
  cmp = b.bytes.to_a
  result = 0
  a.bytes.each_with_index {|c,i|
    result |= c ^ cmp[i]
  }
  result == 0
end

.truncate_multibyte_password(str) ⇒ Object 



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# File 'lib/ruby_rncryptor.rb', line 72

def self.truncate_multibyte_password(str)
  if str.bytes.to_a.count == str.length
    return str
  end
  str.bytes.to_a[0...str.length].map {|c| c.chr}.join
end