Add support for auth-type=form

I'm using a gerrit installation that uses neither 'basic' nor 'digest'
authentication methods, but instead redirects users to a custom login
form which sets a cookie to provide authentication.

This commit adds a new auth-type 'form', that automates logging in
through that form.

Currently, the path to the form is hardcoded to '/login' and the names
of the username and password fields to 'username' and 'password'
respectively. If preferred, I can add configuration options for each of
those too.

Change-Id: I3fff38b1be3f17c753787c9eb62ede0ce60a3ece

examples/reference-gertty.yaml

@@ -23,9 +23,8 @@ servers:
 #    username: CHANGEME
 # Your password in Gerrit (Settings -> HTTP Password). [required]
 #    password: CHANGEME
-# Authentication type required by the Gerrit server. Can be 'basic' or
-# 'digest'. Defaults to 'digest' if not set or set to an unexpected
-# value.
+# Authentication type required by the Gerrit server. Can be 'basic', 'digest' or
+# 'form'. Defaults to 'digest' if not set or set to an unexpected value.
 #    auth-type: digest
 # A location where Gertty should store its git repositories.  These
 # can be the same git repositories where you do your own work --

gertty/auth.py

@@ -0,0 +1,68 @@
+# Copyright 2015 Christoph Gysin <christoph.gysin@gmail.com>
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+import logging
+import requests
+import urlparse
+
+
+class FormAuth(requests.auth.AuthBase):
+
+    def __init__(self, username, password):
+        self.username = username
+        self.password = password
+        self.log = logging.getLogger('gertty.auth')
+
+    def _retry_using_form_auth(self, response, args):
+        adapter = requests.adapters.HTTPAdapter()
+        request = _copy_request(response.request)
+
+        u = urlparse.urlparse(response.url)
+        url = urlparse.urlunparse([u.scheme, u.netloc, '/login',
+                                   None, None, None])
+        auth = {'username': self.username,
+                'password': self.password}
+        request2 = requests.Request('POST', url, data=auth).prepare()
+        response2 = adapter.send(request2, **args)
+
+        if response2.status_code == 401:
+            self.log.error('Login failed: Invalid username or password?')
+            return response
+
+        cookie = response2.headers.get('set-cookie')
+        if cookie is not None:
+            request.headers['Cookie'] = cookie
+
+        response3 = adapter.send(request, **args)
+        return response3
+
+    def _response_hook(self, response, **kwargs):
+        if response.status_code == 401:
+            return self._retry_using_form_auth(response, kwargs)
+        return response
+
+    def __call__(self, request):
+        request.headers["Connection"] = "Keep-Alive"
+        request.register_hook('response', self._response_hook)
+        return request
+
+
+def _copy_request(request):
+    new_request = requests.PreparedRequest()
+    new_request.method = request.method
+    new_request.url = request.url
+    new_request.body = request.body
+    new_request.hooks = request.hooks
+    new_request.headers = request.headers.copy()
+    return new_request

gertty/config.py

@@ -165,7 +165,7 @@ class Config(object):
                     "Permissions are: {}".format(self.path, oct(mode)))
                 exit(1)
         self.auth_type = server.get('auth-type', 'digest')
-        auth_types = ['digest', 'basic']
+        auth_types = ['digest', 'basic', 'form']
         if self.auth_type not in auth_types:
             self.auth_type = 'digest'
         self.verify_ssl = server.get('verify-ssl', True)

gertty/sync.py

@@ -37,6 +37,7 @@ from six.moves.urllib import parse as urlparse
 
 import gertty.version
 from gertty import gitrepo
+from gertty.auth import FormAuth
 
 HIGH_PRIORITY=0
 NORMAL_PRIORITY=1
@@ -1306,6 +1307,8 @@ class Sync(object):
         self.session = requests.Session()
         if self.app.config.auth_type == 'basic':
             authclass = requests.auth.HTTPBasicAuth
+        elif self.app.config.auth_type == 'form':
+            authclass = FormAuth
         else:
             authclass = requests.auth.HTTPDigestAuth
         self.auth = authclass(