This cookie-based session store is the Rails default. Sessions typically contain at most a user_id and flash message; both fit within the 4K cookie size limit. Cookie-based sessions are dramatically faster than the alternatives.
If you have more than 4K of session data or don‘t want your data to be visible to the user, pick another session store.
CookieOverflow is raised if you attempt to store more than 4K of data.
A message digest is included with the cookie to ensure data integrity: a user cannot alter his user_id without knowing the secret key included in the hash. New apps are generated with a pregenerated secret in config/environment.rb. Set your own for old apps you‘re upgrading.
Session options:
- :secret: An application-wide key string or block returning a
string called per generated digest. The block is called with the
CGI::Session instance as an argument. It‘s important that the secret
is not vulnerable to a dictionary attack. Therefore, you should choose a
secret consisting of random numbers and letters and more than 30
characters. Examples:
:secret => '449fe2e7daee471bffae2fd8dc02313d' :secret => Proc.new { User.current_user.secret_key }
- :digest: The message digest algorithm used to verify session integrity defaults to ‘SHA1’ but may be any digest provided by OpenSSL, such as ‘MD5’, ‘RIPEMD160’, ‘SHA256’, etc.
To generate a secret key for an existing application, run "rake secret" and set the key in config/environment.rb.
Note that changing digest or secret invalidates all existing sessions!
MAX | = | 4096 |
Cookies can typically store 4096 bytes. | ||
SECRET_MIN_LENGTH | = | 30 |
DEFAULT_OPTIONS | = | { :key => '_session_id', :domain => nil, :path => "/", :expire_after => nil, :httponly => true |
ENV_SESSION_KEY | = | "rack.session".freeze |
ENV_SESSION_OPTIONS_KEY | = | "rack.session.options".freeze |
HTTP_SET_COOKIE | = | "Set-Cookie".freeze |
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# File actionpack/lib/action_controller/session/cookie_store.rb, line 58 58: def initialize(app, options = {}) 59: # Process legacy CGI options 60: options = options.symbolize_keys 61: if options.has_key?(:session_path) 62: ActiveSupport::Deprecation.warn "Giving :session_path to SessionStore is deprecated, " << 63: "please use :path instead", caller 64: options[:path] = options.delete(:session_path) 65: end 66: if options.has_key?(:session_key) 67: ActiveSupport::Deprecation.warn "Giving :session_key to SessionStore is deprecated, " << 68: "please use :key instead", caller 69: options[:key] = options.delete(:session_key) 70: end 71: if options.has_key?(:session_http_only) 72: ActiveSupport::Deprecation.warn "Giving :session_http_only to SessionStore is deprecated, " << 73: "please use :httponly instead", caller 74: options[:httponly] = options.delete(:session_http_only) 75: end 76: 77: @app = app 78: 79: # The session_key option is required. 80: ensure_session_key(options[:key]) 81: @key = options.delete(:key).freeze 82: 83: # The secret option is required. 84: ensure_secret_secure(options[:secret]) 85: @secret = options.delete(:secret).freeze 86: 87: @digest = options.delete(:digest) || 'SHA1' 88: @verifier = verifier_for(@secret, @digest) 89: 90: @default_options = DEFAULT_OPTIONS.merge(options).freeze 91: 92: freeze 93: end
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# File actionpack/lib/action_controller/session/cookie_store.rb, line 95 95: def call(env) 96: env[ENV_SESSION_KEY] = AbstractStore::SessionHash.new(self, env) 97: env[ENV_SESSION_OPTIONS_KEY] = @default_options.dup 98: 99: status, headers, body = @app.call(env) 100: 101: session_data = env[ENV_SESSION_KEY] 102: options = env[ENV_SESSION_OPTIONS_KEY] 103: 104: if !session_data.is_a?(AbstractStore::SessionHash) || session_data.send(:loaded?) || options[:expire_after] 105: session_data.send(:load!) if session_data.is_a?(AbstractStore::SessionHash) && !session_data.send(:loaded?) 106: session_data = marshal(session_data.to_hash) 107: 108: raise CookieOverflow if session_data.size > MAX 109: 110: cookie = Hash.new 111: cookie[:value] = session_data 112: unless options[:expire_after].nil? 113: cookie[:expires] = Time.now + options[:expire_after] 114: end 115: 116: cookie = build_cookie(@key, cookie.merge(options)) 117: unless headers[HTTP_SET_COOKIE].blank? 118: headers[HTTP_SET_COOKIE] << "\n#{cookie}" 119: else 120: headers[HTTP_SET_COOKIE] = cookie 121: end 122: end 123: 124: [status, headers, body] 125: end