[arch-security] [ASA-201504-13] ruby: permissive certificate verification

[Levente Polyak]

Arch Linux Security Advisory ASA-201504-13
==========================================

Severity: Medium
Date    : 2015-04-14
CVE-ID  : CVE-2015-1855
Package : ruby
Type    : permissive certificate verification
Remote  : Yes
Link    : https://wiki.archlinux.org/index.php/CVE

Summary
=======

The package ruby before version 2.2.2-1 is vulnerable to permissive
certificate verification via matching of hostnames.

Resolution
==========

Upgrade to 2.2.2-1.

# pacman -Syu "ruby>=2.2.2-1"

The problem has been fixed upstream in version 2.2.2.

Workaround
==========

None.

Description
===========

After reviewing RFC 6125 and RFC 5280, multiple violations were found of
matching hostnames and particularly wildcard certificates.

Ruby’s OpenSSL extension will now provide a string-based matching
algorithm which follows more strict behavior, as recommended by these
RFCs. In particular, matching of more than one wildcard per subject/SAN
is no-longer allowed. As well, comparison of these values are now
case-insensitive.

This change will take affect Ruby’s
OpenSSL::SSL#verify_certificate_identity behavior.

Specifically:
- Only one wildcard character in the left-most part of the hostname is
  allowed.
- IDNA names can now only be matched by a simple wildcard (e.g.
  ‘*.domain’).
- Subject/SAN should be limited to ASCII characters only.

Impact
======

A remote attacker can make use of the overly permissive hostname
matching during certificate verifications to perform a man-in-the-middle
attack by spoofing SSL servers via a crafted certificate.

References
==========

https://www.ruby-lang.org/en/news/2015/04/13/ruby-openssl-hostname-matching-vulnerability/
https://access.redhat.com/security/cve/CVE-2015-1855
https://bugs.ruby-lang.org/issues/9644

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