mirror of https://github.com/mastodon/mastodon
78 lines
3.3 KiB
Ruby
78 lines
3.3 KiB
Ruby
# frozen_string_literal: true
|
|
|
|
# TODO: This file is here for legacy support during devise-two-factor upgrade.
|
|
# It should be removed after all records have been migrated.
|
|
|
|
module LegacyOtpSecret
|
|
extend ActiveSupport::Concern
|
|
|
|
private
|
|
|
|
# Decrypt and return the `encrypted_otp_secret` attribute which was used in
|
|
# prior versions of devise-two-factor
|
|
# @return [String] The decrypted OTP secret
|
|
def legacy_otp_secret
|
|
return nil unless self[:encrypted_otp_secret]
|
|
return nil unless self.class.otp_secret_encryption_key
|
|
|
|
hmac_iterations = 2000 # a default set by the Encryptor gem
|
|
key = self.class.otp_secret_encryption_key
|
|
salt = Base64.decode64(encrypted_otp_secret_salt)
|
|
iv = Base64.decode64(encrypted_otp_secret_iv)
|
|
|
|
raw_cipher_text = Base64.decode64(encrypted_otp_secret)
|
|
# The last 16 bytes of the ciphertext are the authentication tag - we use
|
|
# Galois Counter Mode which is an authenticated encryption mode
|
|
cipher_text = raw_cipher_text[0..-17]
|
|
auth_tag = raw_cipher_text[-16..-1] # rubocop:disable Style/SlicingWithRange
|
|
|
|
# this alrorithm lifted from
|
|
# https://github.com/attr-encrypted/encryptor/blob/master/lib/encryptor.rb#L54
|
|
|
|
# create an OpenSSL object which will decrypt the AES cipher with 256 bit
|
|
# keys in Galois Counter Mode (GCM). See
|
|
# https://ruby.github.io/openssl/OpenSSL/Cipher.html
|
|
cipher = OpenSSL::Cipher.new('aes-256-gcm')
|
|
|
|
# tell the cipher we want to decrypt. Symmetric algorithms use a very
|
|
# similar process for encryption and decryption, hence the same object can
|
|
# do both.
|
|
cipher.decrypt
|
|
|
|
# Use a Password-Based Key Derivation Function to generate the key actually
|
|
# used for encryptoin from the key we got as input.
|
|
cipher.key = OpenSSL::PKCS5.pbkdf2_hmac_sha1(key, salt, hmac_iterations, cipher.key_len)
|
|
|
|
# set the Initialization Vector (IV)
|
|
cipher.iv = iv
|
|
|
|
# The tag must be set after calling Cipher#decrypt, Cipher#key= and
|
|
# Cipher#iv=, but before calling Cipher#final. After all decryption is
|
|
# performed, the tag is verified automatically in the call to Cipher#final.
|
|
#
|
|
# If the auth_tag does not verify, then #final will raise OpenSSL::Cipher::CipherError
|
|
cipher.auth_tag = auth_tag
|
|
|
|
# auth_data must be set after auth_tag has been set when decrypting See
|
|
# http://ruby-doc.org/stdlib-2.0.0/libdoc/openssl/rdoc/OpenSSL/Cipher.html#method-i-auth_data-3D
|
|
# we are not adding any authenticated data but OpenSSL docs say this should
|
|
# still be called.
|
|
cipher.auth_data = ''
|
|
|
|
# #update is (somewhat confusingly named) the method which actually
|
|
# performs the decryption on the given chunk of data. Our OTP secret is
|
|
# short so we only need to call it once.
|
|
#
|
|
# It is very important that we call #final because:
|
|
#
|
|
# 1. The authentication tag is checked during the call to #final
|
|
# 2. Block based cipher modes (e.g. CBC) work on fixed size chunks. We need
|
|
# to call #final to get it to process the last chunk properly. The output
|
|
# of #final should be appended to the decrypted value. This isn't
|
|
# required for streaming cipher modes but including it is a best practice
|
|
# so that your code will continue to function correctly even if you later
|
|
# change to a block cipher mode.
|
|
cipher.update(cipher_text) + cipher.final
|
|
end
|
|
end
|