Prefer Edge when running on Linux, by using BROWSER env var

Author: rayluo

msal/application.py

@@ -9,6 +9,7 @@
 import sys
 import warnings
 from threading import Lock
+import os
 
 import requests
 
@@ -27,6 +28,22 @@
 
 logger = logging.getLogger(__name__)
 
+if True:  # Prefer launching Edge when running on Linux to support device-based CA.
+    # This section only works when being run before webbrowser.open().
+    # We could theoretically put it inside acquire_token_interactive(),
+    # but that won't work for some of our major downstream applications
+    # because they happen to invoke webbrowser.open() before calling MSAL.
+    # So, we choose to add this logic at MSAL's module level.
+    if ("BROWSER" not in os.environ  # Customize it when end user has no preference
+            and sys.platform == "linux"):  # On Linux, only Edge will have CA support
+        os.environ["BROWSER"] = (  # This is the executable file name
+            # Hard-coding a well-known location can avoid unwittingly invoking
+            # a potentially malicious "microsoft-edge" in current working directory.
+            "/usr/bin/microsoft-edge")
+        # Unavailable browser will be silently ignored and fall back to the default
+        # More details at https://docs.python.org/3/library/webbrowser.html
+        logger.debug("Prefer %s as browser for sign-in.", os.environ.get("BROWSER"))
+
 
 def extract_certs(public_cert_content):
     # Parses raw public certificate file contents and returns a list of strings