HTTP to PowerShell Drvier Stub

Introduction

In order for Shifu to integrate with your driver. We have implemented a simple HTTP-to-PowerShell stub written in Go for developers to try out.

Design

This HTTP to PowerShell stub is designed the following way:

• The stub exposes an HTTP interface on the host machine
• The HTTP interface is used to forward requests from external to the Windows host machine
• The stub will proxy the result and execution status back to the requestor

Functionality

Proxy HTTP body to PowerShell shell and execute

The main function for this stub is to take whatever passed to it in the HTTP body and issue the command with a specified timeout.

Building:

To build the stub, use:

386:

GOOS=windows GOARCH=386 go build -a -o http2powershell.exe cmd/httpstub/powershellstub/powershellstub.go

amd64:

GOOS=windows GOARCH=amd64 go build -a -o http2powershell.exe cmd/httpstub/powershellstub/powershellstub.go

Usage:

The executable takes the following environmental variables:

• EDGEDEVICE_DRIVER_HTTP_PORT (Optional)
  • The HTTP server port of the driver container, default to 11112
• EDGEDEVICE_DRIVER_EXEC_TIMEOUT_SECOND (Optional)
  • The timeout of an execution, this is achieved by appending timeout <seconds> in front of the command

On Windows host:

To run the stub, double click http2powershell.exe, by default the stub listens to port 11112 on 0.0.0.0

On Shifu:

Use the sample deployment files provided in/examples/simple-powershell-stub

In shifu's root directory issue:

kubectl apply -f driver_util/http-to-powershell-stub/examples/simple-powershell-stub

Proxy the command:

Use curl to post request the Windows host:

root@nginx:/# curl "edgedevice-powershell/issue_cmd?flags_no_parameter=ls,C:"
    Directory: C:\
Mode                 LastWriteTime         Length Name                                                   
----                 -------------         ------ ----                                                   
d-----          6/5/2021   8:10 PM                PerfLogs                                               
d-r---          6/9/2022   2:48 PM                Program Files                                          
d-r---         4/29/2022   8:02 PM                Program Files (x86)                                    
d-r---         4/16/2022   1:46 AM                Users                                                  
d-----          6/9/2022   2:48 PM                Windows                                                
d-----         4/17/2022   5:23 PM                xampp                                                  

root@nginx:/# curl "edgedevice-powershell/issue_cmd?flags_no_parameter=ping,8.8.8.8"

Pinging 8.8.8.8 with 32 bytes of data:
Reply from 8.8.8.8: bytes=32 time=64ms TTL=114
Reply from 8.8.8.8: bytes=32 time=56ms TTL=114
Reply from 8.8.8.8: bytes=32 time=57ms TTL=114
Reply from 8.8.8.8: bytes=32 time=59ms TTL=114

Ping statistics for 8.8.8.8:
    Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
    Minimum = 56ms, Maximum = 64ms, Average = 59ms

For example:

When using curl to post a request to a given URL, the command looks like the following:

curl "example.com/issue_cmd?flags_no_parameter=ping,8.8.8.8

The request will then passes from the HTTP stub into the PowerShell of the Windows host:

> powershell.exe ping 8.8.8.8

Note that the default timeout EDGEDEVICE_DRIVER_EXEC_TIMEOUT_SECOND can be overwritten by the timeout flag in URL, for example:

• Without flag (command timeout, incomplete output):

  root@nginx:/# curl "example.com/issue_cmd?flags_no_parameter=ping,-n,6,8.8.8.8"   
  
  Pinging 8.8.8.8 with 32 bytes of data:
  Reply from 8.8.8.8: bytes=32 time=58ms TTL=114
  Reply from 8.8.8.8: bytes=32 time=51ms TTL=114
  Reply from 8.8.8.8: bytes=32 time=59ms TTL=114
  Reply from 8.8.8.8: bytes=32 time=45ms TTL=114
  Reply from 8.8.8.8: bytes=32 time=59ms TTL=114

• With flag (complete output):

  root@nginx:/# curl "example.com/issue_cmd?timeout=10&flags_no_parameter=ping,-n,6,8.8.8.8" 
  
  Pinging 8.8.8.8 with 32 bytes of data:
  Reply from 8.8.8.8: bytes=32 time=60ms TTL=114
  Reply from 8.8.8.8: bytes=32 time=60ms TTL=114
  Reply from 8.8.8.8: bytes=32 time=59ms TTL=114
  Reply from 8.8.8.8: bytes=32 time=59ms TTL=114
  Reply from 8.8.8.8: bytes=32 time=59ms TTL=114
  Reply from 8.8.8.8: bytes=32 time=60ms TTL=114
  
  Ping statistics for 8.8.8.8:
      Packets: Sent = 6, Received = 6, Lost = 0 (0% loss),
  Approximate round trip times in milli-seconds:
      Minimum = 59ms, Maximum = 60ms, Average = 59ms

We also added a parameter stub_toleration to handle latency issue between deviceShifu and the stub. By default it is set to 1 second. You can override this using the following:

root@nginx:/# curl "example.com/issue_cmd?timeout=10&flags_no_parameter=ping,-n,6,8.8.8.8&stub_toleration=0"