mirror of
https://github.com/avast/ioc
synced 2024-07-05 09:31:48 +00:00
94 lines
2.4 KiB
QBasic
94 lines
2.4 KiB
QBasic
Attribute VB_Name = "Module1"
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'this is a sample to test ripping a decoder with variant types from a malware to reuse it from C
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Public Declare Sub cb Lib "kernel32" (ByVal dwMilliseconds As Long)
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Public Declare Sub scb Lib "kernel32" (ByVal msg As String)
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Sub Main()
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Dim tmp As String
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tmp = rc4("AAAA", Chr(&H41), True)
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'InputBox "", , Hex(StrPtr(tmp)) 'this is how i extracted the encrypted value from memory...
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scb CStr(rc4(tmp, Chr(&H41), True)) 'replace this with a msgbox if testing in IDE
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End Sub
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Public Function rc4(ByteOrString As Variant, ByVal password As String, strret As Boolean)
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On Error Resume Next
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Dim RB(0 To 255) As Integer, X As Long, Y As Long, Z As Long, key() As Byte, temp As Byte
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Dim byteArray() As Byte
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Dim plen As Long
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Const LANG_US = &H409
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If TypeName(ByteOrString) = "Byte()" Then
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byteArray() = ByteOrString
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cb 1
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ElseIf TypeName(ByteOrString) = "String" Then
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byteArray() = StrConv(ByteOrString, vbFromUnicode, LANG_US)
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cb 2
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Else
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cb -1
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Exit Function
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End If
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If TypeName(password) = "Byte()" Then
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key() = password
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If UBound(key) > 255 Then ReDim Preserve key(255)
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cb 3
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Else
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If Len(password) = 0 Then
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cb -2
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Exit Function
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End If
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If Len(password) > 256 Then
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key() = StrConv(Left$(CStr(password), 256), vbFromUnicode, LANG_US)
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Else
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key() = StrConv(CStr(password), vbFromUnicode, LANG_US)
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End If
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cb 4
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End If
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plen = UBound(key) + 1
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cb 6
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'Debug.Print "key=" & HexDump(Key)
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'Debug.Print "data=" & HexDump(ByteArray)
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For X = 0 To 255
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RB(X) = X
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Next X
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X = 0
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Y = 0
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Z = 0
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For X = 0 To 255
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Y = (Y + RB(X) + key(X Mod plen)) Mod 256
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temp = RB(X)
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RB(X) = RB(Y)
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RB(Y) = temp
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Next X
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X = 0
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Y = 0
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Z = 0
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For X = 0 To UBound(byteArray)
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Y = (Y + 1) Mod 256
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Z = (Z + RB(Y)) Mod 256
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temp = RB(Y)
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RB(Y) = RB(Z)
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RB(Z) = temp
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byteArray(X) = byteArray(X) Xor (RB((RB(Y) + RB(Z)) Mod 256))
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Next X
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If strret Then
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cb 7
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rc4 = StrConv(byteArray, vbUnicode, LANG_US)
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Else
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cb 8
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rc4 = byteArray
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End If
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End Function
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