Class: Slosilo::Symmetric

Inherits:
Object
  • Object
show all
Defined in:
lib/slosilo/symmetric.rb

Constant Summary collapse

VERSION_MAGIC = 
'G'
TAG_LENGTH = 
16

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Symmetric

Returns a new instance of Symmetric.



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# File 'lib/slosilo/symmetric.rb', line 6

def initialize
  @cipher = OpenSSL::Cipher.new 'aes-256-gcm' # NB: has to be lower case for whatever reason.
end

Instance Method Details

#cipher_name ⇒ Object

This lets us do a final sanity check in migrations from older encryption versions



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# File 'lib/slosilo/symmetric.rb', line 11

def cipher_name
  @cipher.name
end

#decrypt(ciphertext, opts = {}) ⇒ Object 



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# File 'lib/slosilo/symmetric.rb', line 26

def decrypt ciphertext, opts = {}
  version, tag, iv, ctext = unpack ciphertext

  raise "Invalid version magic: expected #{VERSION_MAGIC} but was #{version}" unless version == VERSION_MAGIC

  @cipher.reset
  @cipher.decrypt
  @cipher.key = opts[:key]
  @cipher.iv = iv
  @cipher.auth_tag = tag
  @cipher.auth_data = opts[:aad] || ""
  @cipher.update(ctext) + @cipher.final
end

#encrypt(plaintext, opts = {}) ⇒ Object 



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# File 'lib/slosilo/symmetric.rb', line 15

def encrypt plaintext, opts = {}
  @cipher.reset
  @cipher.encrypt
  @cipher.key = (opts[:key] or raise("missing :key option"))
  @cipher.iv = iv = random_iv
  @cipher.auth_data = opts[:aad] || "" # Nothing good happens if you set this to nil, or don't set it at all
  ctext = @cipher.update(plaintext) + @cipher.final
  tag = @cipher.auth_tag(TAG_LENGTH)
  "#{VERSION_MAGIC}#{tag}#{iv}#{ctext}"
end

#random_iv ⇒ Object 



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# File 'lib/slosilo/symmetric.rb', line 40

def random_iv
  @cipher.random_iv
end

#random_key ⇒ Object 



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# File 'lib/slosilo/symmetric.rb', line 44

def random_key
  @cipher.random_key
end