Merge branch 'advisory-fix-1'

* advisory-fix-1:
  Introduce a new base class to avoid breaking when upgrading
  Add a version prefix to the private id to make easier to migrate old values
  Fallback to the public id when reading the session in the pool adapter
  Also drop the session with the public id when destroying sessions
  Fallback to the legacy id when the new id is not found
  Add the private id
  revert conditionals to master
  remove NullSession
  remove || raise and get closer to master
  store hashed id, send public id
  use session id objects
  remove more nils
  try to ensure we always have some kind of object

4 files changed, 130 insertions, 12 deletions

diff --git a/lib/rack/session/abstract/id.rb b/lib/rack/session/abstract/id.rb
index b15ee3b8..633f2703 100644
--- a/lib/rack/session/abstract/id.rb
+++ b/lib/rack/session/abstract/id.rb
@@ -8,11 +8,38 @@ require 'time'
 require 'rack/request'
 require 'rack/response'
 require 'securerandom'
+require 'digest/sha2'
 
 module Rack
 
   module Session
 
+    class SessionId
+      ID_VERSION = 2
+
+      attr_reader :public_id
+
+      def initialize(public_id)
+        @public_id = public_id
+      end
+
+      def private_id
+        "#{ID_VERSION}::#{hash_sid(public_id)}"
+      end
+
+      alias :cookie_value :public_id
+
+      def empty?; false; end
+      def to_s; raise; end
+      def inspect; public_id.inspect; end
+
+      private
+
+      def hash_sid(sid)
+        Digest::SHA256.hexdigest(sid)
+      end
+    end
+
     module Abstract
       # SessionHash is responsible to lazily load the session from store.
 
@@ -375,7 +402,7 @@ module Rack
             req.get_header(RACK_ERRORS).puts("Deferring cookie for #{session_id}") if $VERBOSE
           else
             cookie = Hash.new
-            cookie[:value] = data
+            cookie[:value] = cookie_value(data)
             cookie[:expires] = Time.now + options[:expire_after] if options[:expire_after]
             cookie[:expires] = Time.now + options[:max_age] if options[:max_age]
             set_cookie(req, res, cookie.merge!(options))
@@ -383,6 +410,10 @@ module Rack
         end
         public :commit_session
 
+        def cookie_value(data)
+          data
+        end
+
         # Sets the cookie back to the client with session id. We skip the cookie
         # setting if the value didn't change (sid is the same) or expires was given.
 
@@ -424,6 +455,40 @@ module Rack
         end
       end
 
+      class PersistedSecure < Persisted
+        class SecureSessionHash < SessionHash
+          def [](key)
+            if key == "session_id"
+              load_for_read!
+              id.public_id
+            else
+              super
+            end
+          end
+        end
+
+        def generate_sid(*)
+          public_id = super
+
+          SessionId.new(public_id)
+        end
+
+        def extract_session_id(*)
+          public_id = super
+          public_id && SessionId.new(public_id)
+        end
+
+        private
+
+        def session_class
+          SecureSessionHash
+        end
+
+        def cookie_value(data)
+          data.cookie_value
+        end
+      end
+
       class ID < Persisted
         def self.inherited(klass)
           k = klass.ancestors.find { |kl| kl.respond_to?(:superclass) && kl.superclass == ID }
diff --git a/lib/rack/session/cookie.rb b/lib/rack/session/cookie.rb
index 70ddadd6..d78fa997 100644
--- a/lib/rack/session/cookie.rb
+++ b/lib/rack/session/cookie.rb
@@ -48,7 +48,7 @@ module Rack
     #   })
     #
 
-    class Cookie < Abstract::Persisted
+    class Cookie < Abstract::PersistedSecure
       # Encode session cookies as Base64
       class Base64
         def encode(str)
@@ -154,6 +154,15 @@ module Rack
         data
       end
 
+      class SessionId < DelegateClass(Session::SessionId)
+        attr_reader :cookie_value
+
+        def initialize(session_id, cookie_value)
+          super(session_id)
+          @cookie_value = cookie_value
+        end
+      end
+
       def write_session(req, session_id, session, options)
         session = session.merge("session_id" => session_id)
         session_data = coder.encode(session)
@@ -166,7 +175,7 @@ module Rack
           req.get_header(RACK_ERRORS).puts("Warning! Rack::Session::Cookie data size exceeds 4K.")
           nil
         else
-          session_data
+          SessionId.new(session_id, session_data)
         end
       end
 
diff --git a/lib/rack/session/pool.rb b/lib/rack/session/pool.rb
index 2e1f867f..f5b62650 100644
--- a/lib/rack/session/pool.rb
+++ b/lib/rack/session/pool.rb
@@ -26,7 +26,7 @@ module Rack
     #   )
     #   Rack::Handler::WEBrick.run sessioned
 
-    class Pool < Abstract::Persisted
+    class Pool < Abstract::PersistedSecure
       attr_reader :mutex, :pool
       DEFAULT_OPTIONS = Abstract::ID::DEFAULT_OPTIONS.merge drop: false
 
@@ -39,15 +39,15 @@ module Rack
       def generate_sid
         loop do
           sid = super
-          break sid unless @pool.key? sid
+          break sid unless @pool.key? sid.private_id
         end
       end
 
       def find_session(req, sid)
         with_lock(req) do
-          unless sid and session = @pool[sid]
+          unless sid and session = get_session_with_fallback(sid)
             sid, session = generate_sid, {}
-            @pool.store sid, session
+            @pool.store sid.private_id, session
           end
           [sid, session]
         end
@@ -55,14 +55,15 @@ module Rack
 
       def write_session(req, session_id, new_session, options)
         with_lock(req) do
-          @pool.store session_id, new_session
+          @pool.store session_id.private_id, new_session
           session_id
         end
       end
 
       def delete_session(req, session_id, options)
         with_lock(req) do
-          @pool.delete(session_id)
+          @pool.delete(session_id.public_id)
+          @pool.delete(session_id.private_id)
           generate_sid unless options[:drop]
         end
       end
@@ -73,6 +74,12 @@ module Rack
       ensure
         @mutex.unlock if @mutex.locked?
       end
+
+      private
+
+      def get_session_with_fallback(sid)
+        @pool[sid.private_id] || @pool[sid.public_id]
+      end
     end
   end
 end
diff --git a/test/spec_session_pool.rb b/test/spec_session_pool.rb
index fda5f56e..dd1b6573 100644
--- a/test/spec_session_pool.rb
+++ b/test/spec_session_pool.rb
@@ -8,7 +8,7 @@ require 'rack/session/pool'
 
 describe Rack::Session::Pool do
   session_key = Rack::Session::Pool::DEFAULT_OPTIONS[:key]
-  session_match = /#{session_key}=[0-9a-fA-F]+;/
+  session_match = /#{session_key}=([0-9a-fA-F]+);/
 
   incrementor = lambda do |env|
     env["rack.session"]["counter"] ||= 0
@@ -16,7 +16,7 @@ describe Rack::Session::Pool do
     Rack::Response.new(env["rack.session"].inspect).to_a
   end
 
-  session_id = Rack::Lint.new(lambda do |env|
+  get_session_id = Rack::Lint.new(lambda do |env|
     Rack::Response.new(env["rack.session"].inspect).to_a
   end)
 
@@ -145,6 +145,43 @@ describe Rack::Session::Pool do
     pool.pool.size.must_equal 1
   end
 
+  it "can read the session with the legacy id" do
+    pool = Rack::Session::Pool.new(incrementor)
+    req = Rack::MockRequest.new(pool)
+
+    res0 = req.get("/")
+    cookie = res0["Set-Cookie"]
+    session_id = Rack::Session::SessionId.new cookie[session_match, 1]
+    ses0 = pool.pool[session_id.private_id]
+    pool.pool[session_id.public_id] = ses0
+    pool.pool.delete(session_id.private_id)
+
+    res1 = req.get("/", "HTTP_COOKIE" => cookie)
+    res1["Set-Cookie"].must_be_nil
+    res1.body.must_equal '{"counter"=>2}'
+    pool.pool[session_id.private_id].wont_be_nil
+  end
+
+  it "drops the session in the legacy id as well" do
+    pool = Rack::Session::Pool.new(incrementor)
+    req = Rack::MockRequest.new(pool)
+    drop = Rack::Utils::Context.new(pool, drop_session)
+    dreq = Rack::MockRequest.new(drop)
+
+    res0 = req.get("/")
+    cookie = res0["Set-Cookie"]
+    session_id = Rack::Session::SessionId.new cookie[session_match, 1]
+    ses0 = pool.pool[session_id.private_id]
+    pool.pool[session_id.public_id] = ses0
+    pool.pool.delete(session_id.private_id)
+
+    res2 = dreq.get("/", "HTTP_COOKIE" => cookie)
+    res2["Set-Cookie"].must_be_nil
+    res2.body.must_equal '{"counter"=>2}'
+    pool.pool[session_id.private_id].must_be_nil
+    pool.pool[session_id.public_id].must_be_nil
+  end
+
   # anyone know how to do this better?
   it "should merge sessions when multithreaded" do
     unless $DEBUG
@@ -193,7 +230,7 @@ describe Rack::Session::Pool do
   end
 
   it "does not return a cookie if cookie was not written (only read)" do
-    app = Rack::Session::Pool.new(session_id)
+    app = Rack::Session::Pool.new(get_session_id)
     res = Rack::MockRequest.new(app).get("/")
     res["Set-Cookie"].must_be_nil
   end