From 0de876c53fe9355f1e9a73e923519f2a2241f527 Mon Sep 17 00:00:00 2001

From: Aaron Patterson <aaron.patterson@gmail.com>

Date: Thu, 29 Oct 2015 10:42:44 -0700

Subject: [PATCH] use secure string comparisons for basic auth username /

 password

this will avoid timing attacks against applications that use basic auth.

Conflicts:

	activesupport/lib/active_support/security_utils.rb

CVE-2015-7576

---

 .../action_controller/metal/http_authentication.rb |  7 +++++-

 activesupport/lib/active_support/security_utils.rb | 27 ++++++++++++++++++++++

 2 files changed, 33 insertions(+), 1 deletion(-)

 create mode 100644 activesupport/lib/active_support/security_utils.rb

diff --git a/activesupport/lib/active_support/security_utils.rb b/activesupport/lib/active_support/security_utils.rb

new file mode 100644

index 0000000..bb22125

--- /dev/null

+++ b/activesupport/lib/active_support/security_utils.rb

@@ -0,0 +1,27 @@

+require 'digest'

+

+module ActiveSupport

+  module SecurityUtils

+    # Constant time string comparison.

+    #

+    # The values compared should be of fixed length, such as strings

+    # that have already been processed by HMAC. This should not be used

+    # on variable length plaintext strings because it could leak length info

+    # via timing attacks.

+    def secure_compare(a, b)

+      return false unless a.bytesize == b.bytesize

+

+      l = a.unpack "C#{a.bytesize}"

+

+      res = 0

+      b.each_byte { |byte| res |= byte ^ l.shift }

+      res == 0

+    end

+    module_function :secure_compare

+

+    def variable_size_secure_compare(a, b) # :nodoc:

+      secure_compare(::Digest::SHA256.hexdigest(a), ::Digest::SHA256.hexdigest(b))

+    end

+    module_function :variable_size_secure_compare

+  end

+end

-- 

2.2.1