Ruby’s SSL client implements hostname identity check but it does not properly handle hostnames in the certificate that contain null bytes.
OpenSSL::SSL.verifycertificateidentity implements RFC2818 Server Identity check for Ruby’s SSL client but it does not properly handle hostnames in the subjectAltName X509 extension that contain null bytes.
Existing code in lib/openssl/ssl.rb uses OpenSSL::X509::Extension#value for extracting identity from subjectAltName. Extension#value depends OpenSSL function X509V3EXTprint() and for dNSName of subjectAltName it utilizes sprintf() that is known as null byte unsafe. As the result Extension#value returns ‘www.ruby-lang.org’ if the subjectAltName is ‘www.ruby-lang.org\0.example.com’ and OpenSSL::SSL.verifycertificateidentity wrongly identifies the certificate is for ‘www.ruby-lang.org’.
When a CA a SSL client trusts allows to issue the server certificate that has null byte in subjectAltName, remote attackers can obtain the certificate for ‘www.ruby-lang.org\0.example.com’ from the CA to spoof ‘www.ruby-lang.org’ and do man-in-the-middle between Ruby’s SSL client and SSL servers.
External References:
http://www.ruby-lang.org/en/news/2013/06/27/hostname-check-bypassing-vulnerability-in-openssl-client-cve-2013-4073/
Originally, Common Vulnerabilities and Exposures assigned an identifier CVE-2011-1005 to the following vulnerability:
The safe-level feature in Ruby 1.8.6 through 1.8.6-420, 1.8.7 through 1.8.7-330, and 1.8.8dev allows context-dependent attackers to modify strings via the Exception#tos method, as demonstrated by changing an intended pathname.
Later it was reported: [1] http://www.openwall.com/lists/oss-security/2012/10/02/4
that the Ruby nameerrmesgtostr() method is vulnerable to the similar flaw.
Relevant upstream patch: [2] http://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=37068
The BigDecimal library in Ruby 1.8.6 before p369 and 1.8.7 before p173 allows context-dependent attackers to cause a denial of service (application crash) via a string argument that represents a large number, as demonstrated by an attempted conversion to the Float data type.
Originally, Common Vulnerabilities and Exposures assigned an identifier of CVE-2011-1005 to the following vulnerability:
The safe-level feature in Ruby 1.8.6 through 1.8.6-420, 1.8.7 through 1.8.7-330, and 1.8.8dev allows context-dependent attackers to modify strings via the Exception#tos method, as demonstrated by changing an intended pathname.
with the following upstream patch: [1] http://svn.ruby-lang.org/cgi-bin/viewvc.cgi?revision=30903&view=revision
Based on later upstream patch for different (CVE-2012-4464 and CVE-2012-4466) issues: [2] http://svn.ruby-lang.org/cgi-bin/viewvc.cgi?view=revision&revision=37068
it was found that original upstream 1.8.x ruby patch for CVE-2011-1005 issue was not complete, when the NameError#tos() method was used on / with Ruby objects (the test logic in 'testtostaintnesspropagation' test from [1] was actually reversed, so the test returned success also on still vulnerable instances).
Acknowledgements:
This issue was discovered by Vit Ondruch of Red Hat.