Ruby: OpenSSL::X509::Name Equality Check Does Not Work, Patch included

When two OpenSSL::X509::Name objects are compared using ==, depending on the ordering, non-equal objects will return true. When the first argument is one character longer than the second, or the second argument contains a character that is one less than a character in the same position of the first argument, the result of == will be true. Example below:

irb(main):001:0> require ‘openssl’
=> true
irb(main):002:0> a = OpenSSL::X509::Name.new([[“CN”, “www.example.com”]])
=> #<OpenSSL::X509::Name:0x007fa127cdf3f0>
irb(main):003:0> b = OpenSSL::X509::Name.new([[“CN”, “www.example.co”]])
=> #<OpenSSL::X509::Name:0x007fa127cd0260>
irb(main):004:0> c = OpenSSL::X509::Name.new([[“CN”, “www.exbmple.com”]])
=> #<OpenSSL::X509::Name:0x007fa127cb68b0>
irb(main):005:0> a == b
=> true # Should NOT be true
irb(main):006:0> a == c
=> false
irb(main):007:0> c == a
=> true # Should NOT be true
irb(main):008:0> b == a
=> false

This appears to be from the ossl_x509name_cmp function and I was able to fix this with the following diff, with included tests that would fail without the change to ossl_x509name_cmp:

diff --git a/ext/openssl/ossl_x509name.c b/ext/openssl/ossl_x509name.c
index c900bcb…15e4bb0 100644
— a/ext/openssl/ossl_x509name.c
+++ b/ext/openssl/ossl_x509name.c
@@ -400,7 +400,7 @@ ossl_x509name_cmp(VALUE self, VALUE other)

 result = ossl_x509name_cmp0(self, other);
 if (result < 0) return INT2FIX(-1);

• if (result > 1) return INT2FIX(1);

• if (result > 0) return INT2FIX(1);

  return INT2FIX(0);
  }
  diff --git a/test/test_x509name.rb b/test/test_x509name.rb
  index 2d92e64…ae8a8fb 100644
  — a/test/test_x509name.rb
  +++ b/test/test_x509name.rb
  @@ -426,10 +426,24 @@ class OpenSSL::TestX509Name < OpenSSL::TestCase
  name0 = OpenSSL::X509::Name.new([[“DC”, “org”], [“DC”, “ruby-lang”], [“CN”, “bar.ruby-lang.org”]])
  name1 = OpenSSL::X509::Name.new([[“DC”, “org”], [“DC”, “ruby-lang”], [“CN”, “bar.ruby-lang.org”]])
  name2 = OpenSSL::X509::Name.new([[“DC”, “org”], [“DC”, “ruby-lang”], [“CN”, “baz.ruby-lang.org”]])

• name3 = OpenSSL::X509::Name.new([[“DC”, “org”], [“DC”, “ruby-lang”], [“CN”, “bar.ruby-langg.org”]])

• name4 = OpenSSL::X509::Name.new([[“DC”, “org”], [“DC”, “ruby-lang”], [“CN”, “bbz.ruby-lang.org”]])
  assert_equal true, name0 == name1
  assert_equal true, name0.eql?(name1)

• assert_equal true, name1 == name0

• assert_equal true, name1.eql?(name0)
  assert_equal false, name0 == name2
  assert_equal false, name0.eql?(name2)

• assert_equal false, name2 == name0

• assert_equal false, name2.eql?(name0)

• assert_equal false, name0 == name3

• assert_equal false, name0.eql?(name3)

• assert_equal false, name3 == name0

• assert_equal false, name3.eql?(name0)

• assert_equal false, name0 == name4

• assert_equal false, name0.eql?(name4)

• assert_equal false, name4 == name0

• assert_equal false, name4.eql?(name0)
  end

Impact

Whenever names are compared during certificate validation an attacker could use a certificate with a different name, but the comparison will return that they are equal. This would allow an attacker to create an illegitimate certificate that may be accepted as legitimate and then used in signing or encryption operations.