Bug #9644: ssl hostname verification security bug: verify_certificate_identity wildcard matching allows to much

• Status: Closed
• Assignee: MartinBosslet (Martin Bosslet)
• Target version: 2.2.0
• ruby -v: 1.9, 2.0, 2.1
• Backport: 1.9.3: REQUIRED, 2.0.0: DONE, 2.1: DONE

[noxxi (Steffen Ullrich)]

Hi,
I'm not a ruby developer but the maintainer of the IO::Socket::SSL module in Perl. While comparing the state of the SSL implementations in various languages I've noticed, that your validation of the hostname inside the certificate is wrong regarding wildcards.

According to the RFC2818 (http) or RFC6125 (includes http and others) only the leftmost part of the name specification might contain a wildcard, e.g *.foo.bar is allowed, but not www.*.foo.bar or even www.*.*.*. Unfortunatly the implementation of verify_certificate_identity in openssl/ssl.rb (or openssl/ssl-internal.rb in older versions) does a global substitution of * with [^.]+ and thus allows wildcards anywhere and also multiple wildcards. I've verified my assumption with a certificate for www.*.foo.*, which got successfully verified against www.bar.foo.org or www.foobar.foo.bar on ruby 1.9.1. And, from looking at the code the current ruby version has the same problem.

Also, from reading the code I understand that you use the same hostname verification for SMTP, IMAP and POP too. But the verification schemes for these protocols differ from http (see RFC2595 for SMTP, RFC4642 for IMAP and POP):

• while http allows something like www*.example.com the other protocols only allow *.example.com, e.g. the the wildcard must fully replace the leftmost part of the hostname.
• while with http one should not check the common name if subject alternative names exist (and you've implemented it this way), with the other protocols one check common name too.

Regards,
Steffen

[nobu (Nobuyoshi Nakada)]

• Description updated (diff)
• Category set to ext/openssl
• Status changed from Open to Assigned
• Assignee set to MartinBosslet (Martin Bosslet)
• Priority changed from Normal to 5
• Target version set to 2.2.0
• Backport changed from 2.0.0: UNKNOWN, 2.1: UNKNOWN to 1.9.3: REQUIRED, 2.0.0: REQUIRED, 2.1: REQUIRED

Seems no wildcard tests.

[hansdegraaff (Hans de Graaff)]

It looks like this is fixed with https://github.com/ruby/openssl/commit/e9a7bcb8bf2902f907c148a00bbcf21d3fa79596 which is related to https://bugzilla.redhat.com/show_bug.cgi?id=1209981

[nagachika (Tomoyuki Chikanaga)]

• Status changed from Assigned to Closed
• % Done changed from 0 to 100

Applied in changeset r50292.

---

• ext/openssl/lib/openssl/ssl.rb: stricter hostname verification
  following RFC 6125. with the patch provided by Tony Arcieri and
  Hiroshi Nakamura [ruby-core:61545] [Bug #9644]
• test/openssl/test_ssl.rb: add tests for above.

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 1.9.3: REQUIRED, 2.0.0: REQUIRED, 2.1: REQUIRED to 1.9.3: REQUIRED, 2.0.0: REQUIRED, 2.1: DONE

Backported into ruby_2_2 branch at r50293.

[usa (Usaku NAKAMURA)]

• Backport changed from 1.9.3: REQUIRED, 2.0.0: REQUIRED, 2.1: DONE to 1.9.3: REQUIRED, 2.0.0: DONE, 2.1: DONE

ruby_2_0_0 r50294 merged revision(s) 50292.

[terceiro (Antonio Terceiro)]

• File CVE-2015-1855.patch CVE-2015-1855.patch added

Hi,

I was able to backport the patch to Ruby 1.9.3, and it will be included in a Debian wheezy security update soon. I am attaching the patch here.