VBScript implementation of SHA1HMAC meeting Duo Security's specifications

duo_security_sha1hmac.vbs

Function ToString(rabyt,datatype)
  With CreateObject("MSXML2.DOMDocument")
    .LoadXML "<root />"
    .DocumentElement.DataType = datatype
    .DocumentElement.nodeTypedValue = rabyt
    ToString = Replace(.DocumentElement.text, vbLf, "")
  End With
End Function

Function ToSHA1HMAC(sTextToHash, sSharedSecretKey)
	Dim asc, enc, hex, bytes, TextToHash, SharedSecretKey
    Set asc = CreateObject("System.Text.UTF8Encoding")
    Set enc = CreateObject("System.Security.Cryptography.HMACSHA1")
    TextToHash = asc.Getbytes_4(sTextToHash)
    SharedSecretKey = asc.Getbytes_4(sSharedSecretKey)
    enc.Key = SharedSecretKey
    bytes = enc.ComputeHash_2((TextToHash))
	hex = ToString(bytes,"bin.Hex")
	hex = asc.Getbytes_4(hex)
	base64 = ToString(hex,"bin.base64")
	ToSHA1HMAC = base64
End Function

hashedvalue = ToSHA1HMAC("value","secretkey")
msgbox hashedvalue