browser addon: start an isolated browser attached to the proxy

A simple addon that starts an instance of Chrome attached to the current
proxy. The instance is isolated in its own user data directory, and addons are
turned off.

Future work:

- I wasn't able to test the Windows executable path - a Windows dev should
confirm this for us.
- In future it would be nice to support other browsers like Firefox.

4 files changed, 86 insertions, 1 deletions

diff --git a/mitmproxy/addons/__init__.py b/mitmproxy/addons/__init__.py
index 62135765..8f84c20d 100644
--- a/mitmproxy/addons/__init__.py
+++ b/mitmproxy/addons/__init__.py
@@ -1,6 +1,7 @@
 from mitmproxy.addons import allowremote
 from mitmproxy.addons import anticache
 from mitmproxy.addons import anticomp
+from mitmproxy.addons import browser
 from mitmproxy.addons import check_ca
 from mitmproxy.addons import clientplayback
 from mitmproxy.addons import core_option_validation
@@ -25,6 +26,7 @@ def default_addons():
     return [
         core.Core(),
         core_option_validation.CoreOptionValidation(),
+        browser.Browser(),
         allowremote.AllowRemote(),
         anticache.AntiCache(),
         anticomp.AntiComp(),
diff --git a/mitmproxy/addons/browser.py b/mitmproxy/addons/browser.py
new file mode 100644
index 00000000..6e8b2585
--- /dev/null
+++ b/mitmproxy/addons/browser.py
@@ -0,0 +1,62 @@
+import subprocess
+import sys
+import tempfile
+
+from mitmproxy import command
+from mitmproxy import ctx
+
+platformPaths = {
+    "linux": "google-chrome",
+    "win32": "chrome.exe",
+    "darwin": "/Applications/Google Chrome.app/Contents/MacOS/Google Chrome",
+}
+
+
+class Browser:
+    browser = None
+    tdir = None
+
+    @command.command("browser.start")
+    def start(self) -> None:
+        """
+            Start an isolated instance of Chrome that points to the currently
+            running proxy.
+        """
+        if self.browser:
+            if self.browser.poll() is None:
+                ctx.log.alert("Browser already running")
+                return
+            else:
+                self.done()
+
+        cmd = platformPaths.get(sys.platform)
+        if not cmd:  # pragma: no cover
+            ctx.log.alert("Your platform is not supported yet - please submit a patch.")
+            return
+
+        self.tdir = tempfile.TemporaryDirectory()
+        self.browser = subprocess.Popen(
+            [
+                cmd,
+                "--user-data-dir=%s" % str(self.tdir.name),
+                "--proxy-server=%s:%s" % (
+                    ctx.options.listen_host or "127.0.0.1",
+                    ctx.options.listen_port
+                ),
+                "--disable-fre",
+                "--no-default-browser-check",
+                "--no-first-run",
+                "--disable-extensions",
+
+                "about:blank",
+            ],
+            stdout = subprocess.DEVNULL,
+            stderr = subprocess.DEVNULL,
+        )
+
+    def done(self):
+        if self.browser:
+            self.browser.kill()
+            self.tdir.cleanup()
+        self.browser = None
+        self.tdir = None
\ No newline at end of file
diff --git a/mitmproxy/tools/console/defaultkeys.py b/mitmproxy/tools/console/defaultkeys.py
index 8139569e..8c28524a 100644
--- a/mitmproxy/tools/console/defaultkeys.py
+++ b/mitmproxy/tools/console/defaultkeys.py
@@ -2,7 +2,8 @@
 def map(km):
     km.add(":", "console.command ", ["global"], "Command prompt")
     km.add("?", "console.view.help", ["global"], "View help")
-    km.add("C", "console.view.commands", ["global"], "View commands")
+    km.add("B", "browser.start", ["global"], "View commands")
+    km.add("C", "console.view.commands", ["global"], "Start an attached browser")
     km.add("K", "console.view.keybindings", ["global"], "View key bindings")
     km.add("O", "console.view.options", ["global"], "View options")
     km.add("E", "console.view.eventlog", ["global"], "View event log")
diff --git a/test/mitmproxy/addons/test_browser.py b/test/mitmproxy/addons/test_browser.py
new file mode 100644
index 00000000..d1b32186
--- /dev/null
+++ b/test/mitmproxy/addons/test_browser.py
@@ -0,0 +1,20 @@
+from unittest import mock
+
+from mitmproxy.addons import browser
+from mitmproxy.test import taddons
+
+
+def test_browser():
+    with mock.patch("subprocess.Popen") as po:
+        b = browser.Browser()
+        with taddons.context() as tctx:
+            b.start()
+            assert po.called
+            b.start()
+
+            assert not tctx.master.has_log("already running")
+            b.browser.poll = lambda: None
+            b.start()
+            assert tctx.master.has_log("already running")
+            b.done()
+            assert not b.browser