Archive for May 8th, 2008

Execute PowerShell Scripts from Your Smartphone

Suppose you are on vacation/commute/away from your desk and get an emergency IT request. Would not it be cool to just text the PowerShell commands from your phone to your desk, have PowerShell over there execute the script, and send you back the results? ;)

Turns out this is very easy to do. All you need is Outlook, a simple rule in it, a simple PowerShell script and Outlook macro.

Here’s how this all works:

  1. You set up an Outlook rule to check for incoming email with a specific keyword (e.g. $PowerShell$) in the subject and sent from your specific email address.
  2. You send the PowerShell script in the email body and put the keyword in the subject.
  3. The Outlook rule starts an Outlook script and a PowerShell script.
  4. The Outlook script saves the email as a text file and waits for the transcript.
  5. The PowerShell script executes the script exported by Outlook.
  6. Outlook sends the result back.

That is it!

No to the details on how to set this up!
1. Outlook script:
a. In Outlook (I am using 2007 but this should work on the previous ones just fine), click Tools/Macro/Visual Basic Editor.
b. Paste this script into the editor:

' (C) Dmitry Sotnikov
' http://dmitrysotnikov.wordpress.com
' Add this to your Outlook macros project
' Then associate SaveAsText with a rule procesing
' emails from your address with a keyword in subject

' This is to have a Sleep function in Outlook
Declare Sub Sleep Lib "kernel32" (ByVal dwMilliseconds As Long)

' The main function saving the script email as text
' and sending back the transcript
Sub SaveAsText(MyMail As MailItem)
    ' Export email (with PowerShell script in body) as a text file
    MyMail.SaveAs "c:\scripts\outlook.ps1", olTXT
    
    ' Create a response email
    Dim reMail As Outlook.MailItem
    Set reMail = MyMail.Reply
    
    ' wait till transcript is available
    Set fs = CreateObject("Scripting.FileSystemObject")
    While Not fs.FileExists("C:\Scripts\email_transcript.txt")
        Sleep 1000
    Wend
    
    ' attach the transcript and send it back
    reMail.Attachments.Add "C:\Scripts\email_transcript.txt"
    reMail.Send
End Sub

c. Close the Editor.

2. Create a PowerShell script which processes the script (removes the message header, executes, saves transcript). I called it execute_email.ps1 and saved to c:\scripts. Here’s the script:

# (C) Dmitry Sotnikov
# http://dmitrysotnikov.wordpress.com
# This is a PowerShell companion script for Outlook
# macro processing PowerShell commands from email

# Delete any previous transcripts and start a new one
Remove-Item "c:\Scripts\email_transcript.txt" -ErrorAction SilentlyContinue
Start-Transcript "c:\Scripts\email_transcript_temp.txt"

# wait till Outlook saves the script email
while ( -not (Test-Path "c:\Scripts\outlook.ps1")) {
    Start-Sleep -Seconds 1
}

# Read the script, skip the header lines, execute the rest
Get-Content "c:\Scripts\outlook.ps1" | Where { $i++ -gt 4 } > "c:\Scripts\justscript.ps1"
. "c:\Scripts\justscript.ps1"

# Remove the old script
Remove-Item "c:\Scripts\outlook.ps1" -ErrorAction SilentlyContinue
Remove-Item "c:\Scripts\justscript.ps1" -ErrorAction SilentlyContinue

# Stop transcript and make it available for Outlook to send back
Stop-Transcript
Rename-Item "c:\Scripts\email_transcript_temp.txt" -NewName "email_transcript.txt"

3. Create a cmd file which starts PowerShell and executes the script. I called it execute_email.cmd, saved to the same folder c:\scripts and it just have one single line:
powershell.exe "c:\scripts\execute_email.ps1"

4. In Outlook click Tools/Rules and Alerts and create the rule, which executes the Outlook macro and the cmd:

Outlook rule to export PowerShell script, execute it, and send back the transcript

You have just created a remote execution system working from any phone or internet kiosk!

Let’s test it. For example, let’s say I need to add someone to a group. I just send the script to my email address:

A sample email with a PowerShell script

Outlook at my desk gets the email, saves it as text, kicks PowerShell execution, and sends me back the transcript.

Just make sure you change the keyword for something no one can guess, take your smartphone with you and go home. There’s no need to be sitting by your desk anymore. ;)

Acknowledgments: this is based on a great Lifehacker forum post on shutting down a computer based on a message. They also have posts on using other email clients such as Thunderbird or Mac Mail.app.

For your convenience I am also attaching the script files:

[UPDATE] Important: Just to make it clear: return address does not guarantee security and can be easily faked. Make sure you keep the keyword in secret or implement other means of additional protection – see one of my comments below. (So weird that Outlook does not allow to execute rules only if the email signature is verified. This could be another additional way to protect the system.)

[UPDATE 2] There’s also now a commercial alternative solution – PowerGUI Pro MobileShell – which gives in-browser PowerShell prompt from any computer or mobile device to a server in your IT environment.

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© 2007-2014 Dmitry Sotnikov

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