HTTPS URLs are no valid HTTP(S) proxy addresses

[lenerd]

Hello,

I am trying to configure an HTTPS proxy such that syncthing's requests to https://{discovery,relays}.syncthing.net are proxied. On my computer, I achieve this by setting the https_proxy environment variable. When I try the same in the android app via Experimental -> HTTP(S) proxy, I get an error message, that the "Input violates proxy syntax".

In the corresponding code, the regex ^http://.*:\\d{1,5}$ only supports HTTP URLs. Is there a specific reason for this restriction? I would like to use a URL of the form https://user:[email protected]:1337 to connect to my proxy server.

syncthing-android/app/src/main/java/com/nutomic/syncthingandroid/activities/SettingsActivity.java

Lines 1174 to 1187 in 6b7eb72

	private boolean handleHttpProxyPreferenceChange(Preference preference, String newValue) {
	// Valid input is either a proxy address or an empty field to disable the proxy.
	if (newValue.equals("")) {
	preference.setSummary(getString(R.string.do_not_use_proxy) + " " + getString(R.string.generic_example) + ": " + getString(R.string.http_proxy_address_example));
	return true;
	} else if (newValue.matches("^http://.*:\\d{1,5}$")) {
	preference.setSummary(getString(R.string.use_proxy) + " " + newValue);
	return true;
	} else {
	Toast.makeText(getActivity(), R.string.toast_invalid_http_proxy_address, Toast.LENGTH_SHORT)
	.show();
	return false;
	}
	}

[Catfriend1]

Does Android Linux support:

https://user:[email protected]:1337

?

[lenerd]

Good question. I guess it depends what is meant by that. Take the following with a grain of salt, since I am not very familiar with Android internals.

When trying to configure a proxy in the Wi-Fi settings, GrapheneOS indeed only allows me to specify a hostname and a port. Apparently there are/were some versions of Android that also allow to specify credentials. In any way, it depends on the applications to support and honor this setting.

Regarding syncthing(-android): When the HTTP(S) Proxy setting is non-empty, syncthing-android sets the environment variables http_proxy and https_proxy accordingly, and then runs syncthing. Syncthing picks up these settings when it creates the HTTPS connections by calling http.ProxyFromEnvironment (cf. syncthing/syncthing/pull/2375). So it seems that the proxy handling happens withing the Go standard library. Assuming the syncthing code that is run on Android is the same that runs when installing syncthing on a normal Linux computer, I do not see why it should not work.

If I manage to compile syncthing-android myself, I could make the regex less restrictive and try to see if it works.

[Catfriend1]

I could do that for you, but then I'd need you standby for feedback to verify the change working correctly. Compiling using the batch / py scripts is relatively easy. Install Android studio , python, git tools, run setenv.cmd and build . :)

[lenerd]

I managed to build an APK with a patched regular expression (9a680a3). With the "HTTP(S) proxy" option in syncthing set to an HTTPS URL pointing to my server, I could observe successful connections from the app to the *.syncthing.net domains.

[Catfriend1]

Wew, congrats. So we have a verified change. Feel free to PR that line and get the credit of contributing 👍🤗