我有一天遇到了同样的问题，发现生成的秘密是64字节长我的mac），但是Rails确保密钥是32字节长（来源）。

I have had the same problem the other day and figured out that the generated secret was 64 bytes long (on my mac), but Rails ensures that the key is 32 bytes long (source).

这对我有用：

require 'cgi'
require 'json'
require 'active_support'

def verify_and_decrypt_session_cookie(cookie, secret_key_base)



cookie = CGI::unescape(cookie)
  salt         = 'encrypted cookie'
  signed_salt  = 'signed encrypted cookie'
  key_generator = ActiveSupport::KeyGenerator.new(secret_key_base, iterations: 1000)
  secret = key_generator.generate_key(salt)[0, ActiveSupport::MessageEncryptor.key_len]
  sign_secret = key_generator.generate_key(signed_salt)
  encryptor = ActiveSupport::MessageEncryptor.new(secret, sign_secret, serializer: JSON)

  encryptor.decrypt_and_verify(cookie)
end

或没有 ActiveSupport ：

require 'openssl'
require 'base64'
require 'cgi'
require 'json'

def verify_and_decrypt_session_cookie cookie, secret_key_base
  cookie = CGI.unescape(cookie)

  #################
  # generate keys #
  #################
  encrypted_cookie_salt = 'encrypted cookie' # default: Rails.application.config.action_dispatch.encrypted_cookie_salt
  encrypted_signed_cookie_salt = 'signed encrypted cookie' # default: Rails.application.config.action_dispatch.encrypted_signed_cookie_salt
  iterations = 1000
  key_size = 64
  secret = OpenSSL::PKCS5.pbkdf2_hmac_sha1(secret_key_base, encrypted_cookie_salt, iterations, key_size)[0, OpenSSL::Cipher.new('aes-256-cbc').key_len]
  sign_secret = OpenSSL::PKCS5.pbkdf2_hmac_sha1(secret_key_base, encrypted_signed_cookie_salt, iterations, key_size)

  ##########
  # Verify #
  ##########
  data, digest = cookie.split('--')
  raise 'invalid message' unless digest == OpenSSL::HMAC.hexdigest(OpenSSL::Digest::SHA1.new, sign_secret, data)
  # you better use secure compare instead of `==` to prevent time based attact,
  # ref: ActiveSupport::SecurityUtils.secure_compare

  ###########
  # Decrypt #
  ###########
  encrypted_message = Base64.strict_decode64(data)
  encrypted_data, iv = encrypted_message.split('--').map{|v| Base64.strict_decode64(v) }
  cipher = OpenSSL::Cipher::Cipher.new('aes-256-cbc')
  cipher.decrypt
  cipher.key = secret
  cipher.iv  = iv
  decrypted_data = cipher.update(encrypted_data)
  decrypted_data << cipher.final

  JSON.load(decrypted_data)
end

请随时对要点发表评论： https://gist.github.com/mbyczkowski/34fb691b4d7a100c32148705f244d028

Feel free to comment on the gist: https://gist.github.com/mbyczkowski/34fb691b4d7a100c32148705f244d028