Support auth code flow in WSL Ubuntu 18.04

[jiasli]

It will be good for MSAL to support auth code flow in WSL Ubuntu 18.04.

webbrowser doesn't work in WSL Ubuntu 18.04 due to the lack of www-browser:

$ python3 -V
Python 3.6.9
$ python3 -c "import webbrowser; print(webbrowser.open('https://microsoft.com'))"
False
$ python3 -c "import webbrowser; print(webbrowser.get())"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/lib/python3.6/webbrowser.py", line 51, in get
    raise Error("could not locate runnable browser")
webbrowser.Error: could not locate runnable browser
$ which www-browser
$

WSL Ubuntu 20.04 already supports this:

$ python3 -V
Python 3.8.5
$ python3 -c "import webbrowser; print(webbrowser.get().name)"
www-browser
$ which www-browser
/usr/bin/www-browser

Azure CLI supports WSL Ubuntu 18.04 by

https://github.com/Azure/azure-cli/blob/3bff786b9e337aa35bb4cc64a09e5600a35663f8/src/azure-cli-core/azure/cli/core/util.py#L637-L648

def open_page_in_browser(url):
    import subprocess
    import webbrowser
    platform_name, _ = _get_platform_info()


    if is_wsl():   # windows 10 linux subsystem
        try:
            # https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.core/about/about_powershell_exe
            # Ampersand (&) should be quoted
            return subprocess.call(['powershell.exe', '-Command', 'Start-Process "{}"'.format(url)])
        except OSError:  # WSL might be too old  # FileNotFoundError introduced in Python 3
            pass

Without this functionality, Azure CLI will have a regression when using MSAL.

[jiasli]

Test script:

import msal

app = msal.PublicClientApplication('04b07795-8ddb-461a-bbee-02f9e1bf7b46', authority='https://login.microsoftonline.com/organizations')
app.acquire_token_interactive(['https://management.azure.com/.default'])

Error:

$ python test.py
Found no browser in current environment. If this program is being run inside a container which has access to host network (i.e. started by `docker run --net=host -it ...`), you can use browser on host to visit the following link. Otherwise, this auth attempt would either timeout (current timeout setting is None) or be aborted by CTRL+C. Auth URI: https://login.microsoftonline.com/organizations/oauth2/v2.0/authorize?...

[rayluo]

Jiashuo Li (@jiasli) , how reliable is that "...Start-Process url" approach? Also, isn't that is_wsl() also catch WSL2? On WSL2, is there any difference between the "... Start-Process url" approach and the Python native webbrowser approach?

[jiasli]

Thanks Ray Luo (@rayluo) for the rapid response.

how reliable is that "...Start-Process url" approach?

Start-Process url approach should be reliable because powershell.exe is available since Windows 7. WSL is available since Windows 10, so powershell.exe must exist on the system. At least, it has been proven to be very reliable with Azure CLI. 🤣

Also, isn't that is_wsl() also catch WSL2?

Yes, detecting WSL 2 with is_wsl() is added by Azure/azure-cli#16556.

On WSL2, is there any difference between the "... Start-Process url" approach and the Python native webbrowser approach?

The problem is not regarding WSL 1 or WSL 2, but whether the Ubuntu image has www-browser.

• Python native webbrowser approach internally calls www-browser.
• If www-browser doesn't exist on the system, we fall back to calling powershell.exe with Start-Process url.

[jiasli]

The help message of www-browser reveals more info:

$ www-browser --help
www-browser - Part of wslu, a collection of utilities for Windows 10 Windows Subsystem for Linux
Usage: wslview (--register|--unregister|--help|--version) [LINK]

For more help for www-browser, visit the following site: https://github.com/wslutilities/wslu/wiki/www-browser