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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"