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module ActionDispatch
module Session
# 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:
#
# * <tt>:secret</tt>: 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 }
#
# * <tt>:digest</tt>: 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!
class CookieStore
# Cookies can typically store 4096 bytes.
MAX = 4096
SECRET_MIN_LENGTH = 30 # characters
DEFAULT_OPTIONS = {
:key => '_session_id',
:domain => nil,
:path => "/",
:expire_after => nil,
:httponly => true
}.freeze
ENV_SESSION_KEY = "rack.session".freeze
ENV_SESSION_OPTIONS_KEY = "rack.session.options".freeze
HTTP_SET_COOKIE = "Set-Cookie".freeze
# Raised when storing more than 4K of session data.
class CookieOverflow < StandardError; end
def initialize(app, options = {})
# Process legacy CGI options
options = options.symbolize_keys
if options.has_key?(:session_path)
options[:path] = options.delete(:session_path)
end
if options.has_key?(:session_key)
options[:key] = options.delete(:session_key)
end
if options.has_key?(:session_http_only)
options[:httponly] = options.delete(:session_http_only)
end
@app = app
# The session_key option is required.
ensure_session_key(options[:key])
@key = options.delete(:key).freeze
# The secret option is required.
ensure_secret_secure(options[:secret])
@secret = options.delete(:secret).freeze
@digest = options.delete(:digest) || 'SHA1'
@verifier = verifier_for(@secret, @digest)
@default_options = DEFAULT_OPTIONS.merge(options).freeze
freeze
end
def call(env)
env[ENV_SESSION_KEY] = AbstractStore::SessionHash.new(self, env)
env[ENV_SESSION_OPTIONS_KEY] = @default_options.dup
status, headers, body = @app.call(env)
session_data = env[ENV_SESSION_KEY]
options = env[ENV_SESSION_OPTIONS_KEY]
if !session_data.is_a?(AbstractStore::SessionHash) || session_data.send(:loaded?) || options[:expire_after]
session_data.send(:load!) if session_data.is_a?(AbstractStore::SessionHash) && !session_data.send(:loaded?)
session_data = marshal(session_data.to_hash)
raise CookieOverflow if session_data.size > MAX
cookie = Hash.new
cookie[:value] = session_data
unless options[:expire_after].nil?
cookie[:expires] = Time.now + options[:expire_after]
end
cookie = build_cookie(@key, cookie.merge(options))
unless headers[HTTP_SET_COOKIE].blank?
headers[HTTP_SET_COOKIE] << "\n#{cookie}"
else
headers[HTTP_SET_COOKIE] = cookie
end
end
[status, headers, body]
end
private
# Should be in Rack::Utils soon
def build_cookie(key, value)
case value
when Hash
domain = "; domain=" + value[:domain] if value[:domain]
path = "; path=" + value[:path] if value[:path]
# According to RFC 2109, we need dashes here.
# N.B.: cgi.rb uses spaces...
expires = "; expires=" + value[:expires].clone.gmtime.
strftime("%a, %d-%b-%Y %H:%M:%S GMT") if value[:expires]
secure = "; secure" if value[:secure]
httponly = "; HttpOnly" if value[:httponly]
value = value[:value]
end
value = [value] unless Array === value
cookie = Rack::Utils.escape(key) + "=" +
value.map { |v| Rack::Utils.escape(v) }.join("&") +
"#{domain}#{path}#{expires}#{secure}#{httponly}"
end
def load_session(env)
request = Rack::Request.new(env)
session_data = request.cookies[@key]
data = unmarshal(session_data) || persistent_session_id!({})
[data[:session_id], data]
end
# Marshal a session hash into safe cookie data. Include an integrity hash.
def marshal(session)
@verifier.generate(persistent_session_id!(session))
end
# Unmarshal cookie data to a hash and verify its integrity.
def unmarshal(cookie)
persistent_session_id!(@verifier.verify(cookie)) if cookie
rescue ActiveSupport::MessageVerifier::InvalidSignature
nil
end
def ensure_session_key(key)
if key.blank?
raise ArgumentError, 'A key is required to write a ' +
'cookie containing the session data. Use ' +
'config.action_controller.session = { :key => ' +
'"_myapp_session", :secret => "some secret phrase" } in ' +
'config/environment.rb'
end
end
# To prevent users from using something insecure like "Password" we make sure that the
# secret they've provided is at least 30 characters in length.
def ensure_secret_secure(secret)
# There's no way we can do this check if they've provided a proc for the
# secret.
return true if secret.is_a?(Proc)
if secret.blank?
raise ArgumentError, "A secret is required to generate an " +
"integrity hash for cookie session data. Use " +
"config.action_controller.session = { :key => " +
"\"_myapp_session\", :secret => \"some secret phrase of at " +
"least #{SECRET_MIN_LENGTH} characters\" } " +
"in config/environment.rb"
end
if secret.length < SECRET_MIN_LENGTH
raise ArgumentError, "Secret should be something secure, " +
"like \"#{ActiveSupport::SecureRandom.hex(16)}\". The value you " +
"provided, \"#{secret}\", is shorter than the minimum length " +
"of #{SECRET_MIN_LENGTH} characters"
end
end
def verifier_for(secret, digest)
key = secret.respond_to?(:call) ? secret.call : secret
ActiveSupport::MessageVerifier.new(key, digest)
end
def generate_sid
ActiveSupport::SecureRandom.hex(16)
end
def persistent_session_id!(data)
(data ||= {}).merge!(inject_persistent_session_id(data))
end
def inject_persistent_session_id(data)
requires_session_id?(data) ? { :session_id => generate_sid } : {}
end
def requires_session_id?(data)
if data
data.respond_to?(:key?) && !data.key?(:session_id)
else
true
end
end
end
end
end
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