Example: Parameterized sensors

Parameterized sensors prompt you to specify a value when asking a dynamic question. If it becomes a saved question, the value is saved and is specified when you reissue the saved question. Create parameterized sensors to query endpoints for specific values that are often variable, such as file names, process names, and registry key values.

Registry Value Data is a parameterized sensor that is in the Initial Content pack. When you use that sensor in a dynamic question, the Tanium Server prompts you to specify values for the Registry Key and Registry Value parameters.

Figure  1:  Question parser prompts for values to pass to the parameterized sensor

When you specify values and click Go, the Tanium Server issues the question. Then the Question Bar shows the substituted values and the Question Results grid shows the results.

Figure  2:  Results from a dynamic question with a parameterized sensor

When you save a question that has a parameterized sensor, the sensor definition, including the substituted values, is saved in an object called a temp sensor. On the endpoint, the Tanium™ Client runs the temp sensor when it computes answers to a saved question that calls it. A saved question that is reissued according to a schedule continues to use the temp sensor even if the sensor from which it was based is updated. Therefore, if a sensor is updated, and you want the saved question to use the updated code, you must re-create the saved question.

Script

When you develop the sensor script, enclose the input parameters with double vertical bars (||), like ||strKey|| and ||strValue|| in the following example.

Figure  3:  Sensor script

The Tanium Server percent encodes parameter data before passing it to the underlying script and the data must have UTF-8 decoding applied before use. The Registry Value Data sensor script in Figure  3 uses an @include to the i18n/UTF8Decode.vbs script. This script ensures that user input in the Tanium Console form is properly encoded when passed to the sensor script.

'- Begin file: i18n/UTF8Decode.vbs
'========================================
' UTF8Decode
'========================================
' Used to convert the UTF-8 style parameters passed from 
' the server to sensors in sensor parameters.
' This function should be used to safely pass non english input to sensors.
'-----
'-----
Function UTF8Decode(str)
    Dim arraylist(), strLen, i, sT, val, depth, sR
    Dim arraysize
    arraysize = 0
    strLen = Len(str)
    for i = 1 to strLen
        sT = mid(str, i, 1)
        if sT = "%" then
            if i + 2 <= strLen then
                Redim Preserve arraylist(arraysize + 1)
                arraylist(arraysize) = cbyte("&H" & mid(str, i + 1, 2))
                arraysize = arraysize + 1
                i = i + 2
            end if
        else
            Redim Preserve arraylist(arraysize + 1)
            arraylist(arraysize) = asc(sT)
            arraysize = arraysize + 1
        end if
    next
    depth = 0
    for i = 0 to arraysize - 1
		Dim mybyte
        mybyte = arraylist(i)
        if mybyte and &h80 then
            if (mybyte and &h40) = 0 then
                if depth = 0 then
                    Err.Raise 5
                end if
                val = val * 2 ^ 6 + (mybyte and &h3f)
                depth = depth - 1
                if depth = 0 then
                    sR = sR & chrw(val)
                    val = 0
                end if
            elseif (mybyte and &h20) = 0 then
                if depth > 0 then Err.Raise 5
                val = mybyte and &h1f
                depth = 1
            elseif (mybyte and &h10) = 0 then
                if depth > 0 then Err.Raise 5
                val = mybyte and &h0f
                depth = 2
            else
                Err.Raise 5
            end if
        else
            if depth > 0 then Err.Raise 5
            sR = sR & chrw(mybyte)
        end if
    next
    if depth > 0 then Err.Raise 5
    UTF8Decode = sR
End Function
'- End file: i18n/UTF8Decode.vbs

In shell scripts, you can use a function similar to the following to decode the parameter data:

#!/bin/sh

percent_decode() {
        local data=$(echo "$1" | sed 's/%/\\\x/g')
        /usr/bin/printf '%b' "$data"
}

myVariable=`percent_decode "||parameter_value||"`

The printf utility might not be available or might not work correctly on all Linux, macOS, and UNIX platforms. A more fool-proof but less elegant implementation is:

#!/bin/sh 

brute_force_percent_decode() {
        # decode everything between 0x20-0x7E except:
        #0 1 2 3 4 5 6 7 8 9 (0x30-0x39)
        #A B C D E F G H I J K L M N O P Q R S T U V W X Y Z (0x41-0x5A)
        #a b c d e f g h i j k l m n o p q r s t u v w x y z (0x61-0x7A)
        echo "$1" | sed -e 's/%20/ /g' \
        -e 's/%21/!/g' \
        -e 's/%22/"/g' \
        -e 's/%23/#/g' \
        -e 's/%24/$/g' \
        -e 's/%25/%/g' \
        -e 's/%26/\&/g' \
        -e "s/%27/'/g" \
        -e 's/%28/(/g' \
        -e 's/%29/)/g' \
        -e 's/%2[aA]/*/g' \
        -e 's/%2[bB]/+/g' \
        -e 's/%2[cC]/,/g' \
        -e 's/%2[dD]/-/g' \
        -e 's/%2[eE]/./g' \
        -e 's#%2[fF]#/#g' \
        -e 's/%3[aA]/:/g' \
        -e 's/%3[bB]/;/g' \
        -e 's/%3[cC]/</g' \
        -e 's/%3[dD]/=/g' \
        -e 's/%3[eE]/>/g' \
        -e 's/%3[fF]/?/g' \
        -e 's/%40/@/g' \
        -e 's/%5[bB]/[/g' \
        -e 's/%5[cC]/\\/g' \
        -e 's/%5[dD]/]/g' \
        -e 's/%5[eE]/^/g' \
        -e 's/%5[fF]/_/g' \
        -e 's/%60/`/g' \
        -e 's/%7[bB]/{/g' \
        -e 's/%7[cC]/|/g' \
        -e 's/%7[dD]/}/g' \
        -e 's/%7[eE]/-/g'
}

myVariable=`brute_force_percent_decode "||parameter_value||"`

Parameter input settings

Parameter input settings determine the user interface when users are prompted to specify parameter values. In the Key field, specify the parameter names used in the script. Do not enter the double vertical bars (||). The bars are included automatically when the configuration is added to the list of Parameter Inputs names that appear in the navigation menu of the left side of the form.

Figure  4:  Parameter inputs

The most common UI for user input is a text box, but you have choices. You can select from the following UI element options to format the user input control:

  • Checkbox: User enables a setting by checking a box. 0 or 1 is entered into the variable. Returns 1 if checked and 0 if not checked.
  • Date, Date Time, Date Time Range: User selects a date and time or a range. The date time format is epoch with milliseconds. For a range, the user specifies two date times separated by a pipe.
  • Drop Down List: User selects only one option from a list.
  • List: User selects one or more values. Multiple values are separated by a pipe.
  • Numeric: User enters a number. The input can be controlled with minimum and maximums. You can specify a Step Size to require that the input be divisible by the specified value. Snap Interval is the amount that a number is increased or decreased by pressing the up or down button respectively. The Step Size value should be a multiple of the Snap Interval value unless Snap Interval is 0. The user-selected number is entered into the variable.
  • Numeric Interval: User selects a number and an item from a list. The list item has a numeric value. The value entered into the variable is the result of the multiplication. For example, if a user selects 2 and selects High (with high having a value of 3), the value is 6 in the variable.
  • Plugin: Not intended for use by most users. Contact your TAM for additional information about its use.
  • Separator: A separator is a graphical way to separate sections in the user input form.
  • Text Area: User enters a large amount of text. The text is entered into the variable.
  • Text Input: User enters text input. Allowed entries can be controlled with regular expressions. The user input is entered into the variable.
  • Time: User selects a time from a drop-down list. The input can be subject to restrictions.