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From 9fe57c0fc5561088a2df42e4438992591e9d917e Mon Sep 17 00:00:00 2001
From: Jonathan Hefner <jonathan@hefner.pro>
Date: Fri, 12 Feb 2021 12:59:54 -0600
Subject: [PATCH] Refactor CVE-2021-22881 fix
Follow-up to 83a6ac3fee8fd538ce7e0088913ff54f0f9bcb6f.
This allows `HTTP_HOST` to be omitted as before, and reduces the number
of object allocations per request.
Benchmark:
```ruby
# frozen_string_literal: true
require "benchmark/memory"
HOST = "example.com:80"
BEFORE_REGEXP = /\A(?<host>[a-z0-9.-]+|\[[a-f0-9]*:[a-f0-9.:]+\])(:\d+)?\z/
AFTER_REGEXP = /(?:\A|,[ ]?)([a-z0-9.-]+|\[[a-f0-9]*:[a-f0-9.:]+\])(?::\d+)?\z/i
Benchmark.memory do |x|
x.report("BEFORE (non-nil X-Forwarded-Host)") do
origin_host = BEFORE_REGEXP.match(HOST.to_s.downcase)[:host]
forwarded_host = BEFORE_REGEXP.match(HOST.to_s.split(/,\s?/).last)[:host]
end
x.report("BEFORE (nil X-Forwarded-Host)") do
origin_host = BEFORE_REGEXP.match(HOST.to_s.downcase)[:host]
forwarded_host = BEFORE_REGEXP.match(nil.to_s.split(/,\s?/).last)
end
x.report("AFTER (non-nil X-Forwarded-Host)") do
origin_host = HOST&.slice(AFTER_REGEXP, 1) || ""
forwarded_host = HOST&.slice(AFTER_REGEXP, 1) || ""
end
x.report("AFTER (nil X-Forwarded-Host)") do
origin_host = HOST&.slice(AFTER_REGEXP, 1) || ""
forwarded_host = nil&.slice(AFTER_REGEXP, 1) || ""
end
end
```
Results:
```
BEFORE (non-nil X-Forwarded-Host)
616.000 memsize ( 208.000 retained)
9.000 objects ( 2.000 retained)
2.000 strings ( 1.000 retained)
BEFORE (nil X-Forwarded-Host)
328.000 memsize ( 0.000 retained)
5.000 objects ( 0.000 retained)
2.000 strings ( 0.000 retained)
AFTER (non-nil X-Forwarded-Host)
248.000 memsize ( 168.000 retained)
3.000 objects ( 1.000 retained)
1.000 strings ( 0.000 retained)
AFTER (nil X-Forwarded-Host)
40.000 memsize ( 0.000 retained)
1.000 objects ( 0.000 retained)
1.000 strings ( 0.000 retained)
```
[CVE-2021-22942]
---
.../middleware/host_authorization.rb | 22 +++++++------------
.../test/dispatch/host_authorization_test.rb | 4 ++--
.../application/middleware/remote_ip_test.rb | 1 -
railties/test/isolation/abstract_unit.rb | 2 +-
4 files changed, 11 insertions(+), 18 deletions(-)
Index: rails-6.0.3.7+dfsg/actionpack/lib/action_dispatch/middleware/host_authorization.rb
===================================================================
--- rails-6.0.3.7+dfsg.orig/actionpack/lib/action_dispatch/middleware/host_authorization.rb
+++ rails-6.0.3.7+dfsg/actionpack/lib/action_dispatch/middleware/host_authorization.rb
@@ -86,21 +86,15 @@ module ActionDispatch
end
private
- def authorized?(request)
- valid_host = /
- \A
- (?<host>[a-z0-9.-]+|\[[a-f0-9]*:[a-f0-9.:]+\])
- (:\d+)?
- \z
- /x
+ HOSTNAME = /[a-z0-9.-]+|\[[a-f0-9]*:[a-f0-9.:]+\]/i
+ VALID_ORIGIN_HOST = /\A(#{HOSTNAME})(?::\d+)?\z/
+ VALID_FORWARDED_HOST = /(?:\A|,[ ]?)(#{HOSTNAME})(?::\d+)?\z/
- origin_host = valid_host.match(
- request.get_header("HTTP_HOST").to_s.downcase)
- forwarded_host = valid_host.match(
- request.x_forwarded_host.to_s.split(/,\s?/).last)
+ def authorized?(request)
+ origin_host = request.get_header("HTTP_HOST")&.slice(VALID_ORIGIN_HOST, 1) || ""
+ forwarded_host = request.x_forwarded_host&.slice(VALID_FORWARDED_HOST, 1) || ""
- origin_host && @permissions.allows?(origin_host[:host]) && (
- forwarded_host.nil? || @permissions.allows?(forwarded_host[:host]))
+ @permissions.allows?(origin_host) && (forwarded_host.blank? || @permissions.allows?(forwarded_host))
end
def mark_as_authorized(request)
Index: rails-6.0.3.7+dfsg/actionpack/test/dispatch/host_authorization_test.rb
===================================================================
--- rails-6.0.3.7+dfsg.orig/actionpack/test/dispatch/host_authorization_test.rb
+++ rails-6.0.3.7+dfsg/actionpack/test/dispatch/host_authorization_test.rb
@@ -163,10 +163,10 @@ class HostAuthorizationTest < ActionDisp
@app = ActionDispatch::HostAuthorization.new(App, ".example.com")
get "/", env: {
- "HOST" => "example.com#sub.example.com",
+ "HOST" => "attacker.com#x.example.com",
}
assert_response :forbidden
- assert_match "Blocked host: example.com#sub.example.com", response.body
+ assert_match "Blocked host: attacker.com#x.example.com", response.body
end
end
Index: rails-6.0.3.7+dfsg/railties/test/application/middleware/remote_ip_test.rb
===================================================================
--- rails-6.0.3.7+dfsg.orig/railties/test/application/middleware/remote_ip_test.rb
+++ rails-6.0.3.7+dfsg/railties/test/application/middleware/remote_ip_test.rb
@@ -11,7 +11,6 @@ module ApplicationTests
def remote_ip(env = {})
remote_ip = nil
env = Rack::MockRequest.env_for("/").merge(env).merge!(
- "HTTP_HOST" => "example.com",
"action_dispatch.show_exceptions" => false,
"action_dispatch.key_generator" => ActiveSupport::CachingKeyGenerator.new(
ActiveSupport::KeyGenerator.new("b3c631c314c0bbca50c1b2843150fe33", iterations: 1000)
Index: rails-6.0.3.7+dfsg/railties/test/isolation/abstract_unit.rb
===================================================================
--- rails-6.0.3.7+dfsg.orig/railties/test/isolation/abstract_unit.rb
+++ rails-6.0.3.7+dfsg/railties/test/isolation/abstract_unit.rb
@@ -77,7 +77,7 @@ module TestHelpers
end
def get(path)
- @app.call(::Rack::MockRequest.env_for(path, "HTTP_HOST" => "example.com"))
+ @app.call(::Rack::MockRequest.env_for(path))
end
def assert_welcome(resp)
|
