It is not possible without some workarounds.
I also needed the same feature and previous SO answer confirms, that is it either impossible or possible with high probability of failure.
One thing I learned about Protrator is not to try to make too complicated stuff with it, or I'll have a bad time.
As for the feature- I ended up making Protractor to initiate Node.js task, which use request to make the authentication and provide back the data.
Taken straight from request module:
request.get('http://some.server.com/').auth('username', 'password', false);
// or
request.get('http://some.server.com/', {
'auth': {
'user': 'username',
'pass': 'password',
'sendImmediately': false
}
});
// or
request.get('http://some.server.com/').auth(null, null, true, 'bearerToken');
// or
request.get('http://some.server.com/', {
'auth': {
'bearer': 'bearerToken'
}
});