authn: Adapt authentication plugins validator to allow legacy plugins.

- We use the prefix 'py:' for legacy plugins
- Users are now able to insert plugin ID's like 'py:rhodecode.mylegacyplugins.plugin_one'
- Validator tries does an import and checks if the plugin has a 'includeme' attribute.

rhodecode/model/validators.py

@@ -1,1077 +1,1120 b''
 # -*- coding: utf-8 -*-
 
 # Copyright (C) 2010-2016  RhodeCode GmbH
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU Affero General Public License, version 3
 # (only), as published by the Free Software Foundation.
 #
 # This program is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 # GNU General Public License for more details.
 #
 # You should have received a copy of the GNU Affero General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #
 # This program is dual-licensed. If you wish to learn more about the
 # RhodeCode Enterprise Edition, including its added features, Support services,
 # and proprietary license terms, please see https://rhodecode.com/licenses/
 
 """
 Set of generic validators
 """
 
 import logging
 import os
 import re
 from collections import defaultdict
 
 import formencode
 import ipaddress
 from formencode.validators import (
     UnicodeString, OneOf, Int, Number, Regex, Email, Bool, StringBoolean, Set,
     NotEmpty, IPAddress, CIDR, String, FancyValidator
 )
 from pylons.i18n.translation import _
 from sqlalchemy.sql.expression import true
 from sqlalchemy.util import OrderedSet
 from webhelpers.pylonslib.secure_form import authentication_token
 
-from rhodecode.authentication import legacy_plugin_prefix
+from rhodecode.authentication import (
+    legacy_plugin_prefix, _import_legacy_plugin)
+from rhodecode.authentication.base import loadplugin
 from rhodecode.config.routing import ADMIN_PREFIX
 from rhodecode.lib.auth import HasRepoGroupPermissionAny, HasPermissionAny
 from rhodecode.lib.utils import repo_name_slug, make_db_config
 from rhodecode.lib.utils2 import safe_int, str2bool, aslist, md5
 from rhodecode.lib.vcs.backends.git.repository import GitRepository
 from rhodecode.lib.vcs.backends.hg.repository import MercurialRepository
 from rhodecode.lib.vcs.backends.svn.repository import SubversionRepository
 from rhodecode.model.db import (
     RepoGroup, Repository, UserGroup, User, ChangesetStatus, Gist)
 from rhodecode.model.settings import VcsSettingsModel
 
 # silence warnings and pylint
 UnicodeString, OneOf, Int, Number, Regex, Email, Bool, StringBoolean, Set, \
     NotEmpty, IPAddress, CIDR, String, FancyValidator
 
 log = logging.getLogger(__name__)
 
 
 class _Missing(object):
     pass
 
 Missing = _Missing()
 
 
 class StateObj(object):
     """
     this is needed to translate the messages using _() in validators
     """
     _ = staticmethod(_)
 
 
 def M(self, key, state=None, **kwargs):
     """
     returns string from self.message based on given key,
     passed kw params are used to substitute %(named)s params inside
     translated strings
 
     :param msg:
     :param state:
     """
     if state is None:
         state = StateObj()
     else:
         state._ = staticmethod(_)
     # inject validator into state object
     return self.message(key, state, **kwargs)
 
 
 def UniqueList(convert=None):
     class _UniqueList(formencode.FancyValidator):
         """
         Unique List !
         """
         messages = {
             'empty': _(u'Value cannot be an empty list'),
             'missing_value': _(u'Value cannot be an empty list'),
         }
 
         def _to_python(self, value, state):
             ret_val = []
 
             def make_unique(value):
                 seen = []
                 return [c for c in value if not (c in seen or seen.append(c))]
 
             if isinstance(value, list):
                 ret_val = make_unique(value)
             elif isinstance(value, set):
                 ret_val = make_unique(list(value))
             elif isinstance(value, tuple):
                 ret_val = make_unique(list(value))
             elif value is None:
                 ret_val = []
             else:
                 ret_val = [value]
 
             if convert:
                 ret_val = map(convert, ret_val)
             return ret_val
 
         def empty_value(self, value):
             return []
 
     return _UniqueList
 
 
 def UniqueListFromString():
     class _UniqueListFromString(UniqueList()):
         def _to_python(self, value, state):
             if isinstance(value, basestring):
                 value = aslist(value, ',')
             return super(_UniqueListFromString, self)._to_python(value, state)
     return _UniqueListFromString
 
 
 def ValidSvnPattern(section, repo_name=None):
     class _validator(formencode.validators.FancyValidator):
         messages = {
             'pattern_exists': _(u'Pattern already exists'),
         }
 
         def validate_python(self, value, state):
             if not value:
                 return
             model = VcsSettingsModel(repo=repo_name)
             ui_settings = model.get_svn_patterns(section=section)
             for entry in ui_settings:
                 if value == entry.value:
                     msg = M(self, 'pattern_exists', state)
                     raise formencode.Invalid(msg, value, state)
     return _validator
 
 
 def ValidUsername(edit=False, old_data={}):
     class _validator(formencode.validators.FancyValidator):
         messages = {
             'username_exists': _(u'Username "%(username)s" already exists'),
             'system_invalid_username':
                 _(u'Username "%(username)s" is forbidden'),
             'invalid_username':
                 _(u'Username may only contain alphanumeric characters '
                     u'underscores, periods or dashes and must begin with '
                     u'alphanumeric character or underscore')
         }
 
         def validate_python(self, value, state):
             if value in ['default', 'new_user']:
                 msg = M(self, 'system_invalid_username', state, username=value)
                 raise formencode.Invalid(msg, value, state)
             # check if user is unique
             old_un = None
             if edit:
                 old_un = User.get(old_data.get('user_id')).username
 
             if old_un != value or not edit:
                 if User.get_by_username(value, case_insensitive=True):
                     msg = M(self, 'username_exists', state, username=value)
                     raise formencode.Invalid(msg, value, state)
 
             if (re.match(r'^[\w]{1}[\w\-\.]{0,254}$', value)
                     is None):
                 msg = M(self, 'invalid_username', state)
                 raise formencode.Invalid(msg, value, state)
     return _validator
 
 
 def ValidRegex(msg=None):
     class _validator(formencode.validators.Regex):
         messages = {'invalid': msg or _(u'The input is not valid')}
     return _validator
 
 
 def ValidRepoUser():
     class _validator(formencode.validators.FancyValidator):
         messages = {
             'invalid_username': _(u'Username %(username)s is not valid')
         }
 
         def validate_python(self, value, state):
             try:
                 User.query().filter(User.active == true())\
                     .filter(User.username == value).one()
             except Exception:
                 msg = M(self, 'invalid_username', state, username=value)
                 raise formencode.Invalid(
                     msg, value, state, error_dict={'username': msg}
                 )
 
     return _validator
 
 
 def ValidUserGroup(edit=False, old_data={}):
     class _validator(formencode.validators.FancyValidator):
         messages = {
             'invalid_group': _(u'Invalid user group name'),
             'group_exist': _(u'User group "%(usergroup)s" already exists'),
             'invalid_usergroup_name':
                 _(u'user group name may only contain alphanumeric '
                   u'characters underscores, periods or dashes and must begin '
                   u'with alphanumeric character')
         }
 
         def validate_python(self, value, state):
             if value in ['default']:
                 msg = M(self, 'invalid_group', state)
                 raise formencode.Invalid(
                     msg, value, state, error_dict={'users_group_name': msg}
                 )
             # check if group is unique
             old_ugname = None
             if edit:
                 old_id = old_data.get('users_group_id')
                 old_ugname = UserGroup.get(old_id).users_group_name
 
             if old_ugname != value or not edit:
                 is_existing_group = UserGroup.get_by_group_name(
                     value, case_insensitive=True)
                 if is_existing_group:
                     msg = M(self, 'group_exist', state, usergroup=value)
                     raise formencode.Invalid(
                         msg, value, state, error_dict={'users_group_name': msg}
                     )
 
             if re.match(r'^[a-zA-Z0-9]{1}[a-zA-Z0-9\-\_\.]+$', value) is None:
                 msg = M(self, 'invalid_usergroup_name', state)
                 raise formencode.Invalid(
                     msg, value, state, error_dict={'users_group_name': msg}
                 )
 
     return _validator
 
 
 def ValidRepoGroup(edit=False, old_data={}, can_create_in_root=False):
     class _validator(formencode.validators.FancyValidator):
         messages = {
             'group_parent_id': _(u'Cannot assign this group as parent'),
             'group_exists': _(u'Group "%(group_name)s" already exists'),
             'repo_exists': _(u'Repository with name "%(group_name)s" '
                              u'already exists'),
             'permission_denied': _(u"no permission to store repository group"
                                    u"in this location"),
             'permission_denied_root': _(
                 u"no permission to store repository group "
                 u"in root location")
         }
 
         def _to_python(self, value, state):
             group_name = repo_name_slug(value.get('group_name', ''))
             group_parent_id = safe_int(value.get('group_parent_id'))
             gr = RepoGroup.get(group_parent_id)
             if gr:
                 parent_group_path = gr.full_path
                 # value needs to be aware of group name in order to check
                 # db key This is an actual just the name to store in the
                 # database
                 group_name_full = (
                     parent_group_path + RepoGroup.url_sep() + group_name)
             else:
                 group_name_full = group_name
 
             value['group_name'] = group_name
             value['group_name_full'] = group_name_full
             value['group_parent_id'] = group_parent_id
             return value
 
         def validate_python(self, value, state):
 
             old_group_name = None
             group_name = value.get('group_name')
             group_name_full = value.get('group_name_full')
             group_parent_id = safe_int(value.get('group_parent_id'))
             if group_parent_id == -1:
                 group_parent_id = None
 
             group_obj = RepoGroup.get(old_data.get('group_id'))
             parent_group_changed = False
             if edit:
                 old_group_name = group_obj.group_name
                 old_group_parent_id = group_obj.group_parent_id
 
                 if group_parent_id != old_group_parent_id:
                     parent_group_changed = True
 
                 # TODO: mikhail: the following if statement is not reached
                 # since group_parent_id's OneOf validation fails before.
                 # Can be removed.
 
                 # check against setting a parent of self
                 parent_of_self = (
                     old_data['group_id'] == group_parent_id
                     if group_parent_id else False
                 )
                 if parent_of_self:
                     msg = M(self, 'group_parent_id', state)
                     raise formencode.Invalid(
                         msg, value, state, error_dict={'group_parent_id': msg}
                     )
 
             # group we're moving current group inside
             child_group = None
             if group_parent_id:
                 child_group = RepoGroup.query().filter(
                     RepoGroup.group_id == group_parent_id).scalar()
 
             # do a special check that we cannot move a group to one of
             # it's children
             if edit and child_group:
                 parents = [x.group_id for x in child_group.parents]
                 move_to_children = old_data['group_id'] in parents
                 if move_to_children:
                     msg = M(self, 'group_parent_id', state)
                     raise formencode.Invalid(
                         msg, value, state, error_dict={'group_parent_id': msg})
 
             # Check if we have permission to store in the parent.
             # Only check if the parent group changed.
             if parent_group_changed:
                 if child_group is None:
                     if not can_create_in_root:
                         msg = M(self, 'permission_denied_root', state)
                         raise formencode.Invalid(
                             msg, value, state,
                             error_dict={'group_parent_id': msg})
                 else:
                     valid = HasRepoGroupPermissionAny('group.admin')
                     forbidden = not valid(
                         child_group.group_name, 'can create group validator')
                     if forbidden:
                         msg = M(self, 'permission_denied', state)
                         raise formencode.Invalid(
                             msg, value, state,
                             error_dict={'group_parent_id': msg})
 
             # if we change the name or it's new group, check for existing names
             # or repositories with the same name
             if old_group_name != group_name_full or not edit:
                 # check group
                 gr = RepoGroup.get_by_group_name(group_name_full)
                 if gr:
                     msg = M(self, 'group_exists', state, group_name=group_name)
                     raise formencode.Invalid(
                         msg, value, state, error_dict={'group_name': msg})
 
                 # check for same repo
                 repo = Repository.get_by_repo_name(group_name_full)
                 if repo:
                     msg = M(self, 'repo_exists', state, group_name=group_name)
                     raise formencode.Invalid(
                         msg, value, state, error_dict={'group_name': msg})
 
     return _validator
 
 
 def ValidPassword():
     class _validator(formencode.validators.FancyValidator):
         messages = {
             'invalid_password':
                 _(u'Invalid characters (non-ascii) in password')
         }
 
         def validate_python(self, value, state):
             try:
                 (value or '').decode('ascii')
             except UnicodeError:
                 msg = M(self, 'invalid_password', state)
                 raise formencode.Invalid(msg, value, state,)
     return _validator
 
 
 def ValidOldPassword(username):
     class _validator(formencode.validators.FancyValidator):
         messages = {
             'invalid_password': _(u'Invalid old password')
         }
 
         def validate_python(self, value, state):
             from rhodecode.authentication.base import authenticate, HTTP_TYPE
             if not authenticate(username, value, '', HTTP_TYPE):
                 msg = M(self, 'invalid_password', state)
                 raise formencode.Invalid(
                     msg, value, state, error_dict={'current_password': msg}
                 )
     return _validator
 
 
 def ValidPasswordsMatch(
         passwd='new_password', passwd_confirmation='password_confirmation'):
     class _validator(formencode.validators.FancyValidator):
         messages = {
             'password_mismatch': _(u'Passwords do not match'),
         }
 
         def validate_python(self, value, state):
 
             pass_val = value.get('password') or value.get(passwd)
             if pass_val != value[passwd_confirmation]:
                 msg = M(self, 'password_mismatch', state)
                 raise formencode.Invalid(
                     msg, value, state,
                     error_dict={passwd: msg, passwd_confirmation: msg}
                 )
     return _validator
 
 
 def ValidAuth():
     class _validator(formencode.validators.FancyValidator):
         messages = {
             'invalid_password': _(u'invalid password'),
             'invalid_username': _(u'invalid user name'),
             'disabled_account': _(u'Your account is disabled')
         }
 
         def validate_python(self, value, state):
             from rhodecode.authentication.base import authenticate, HTTP_TYPE
 
             password = value['password']
             username = value['username']
 
             if not authenticate(username, password, '', HTTP_TYPE,
                                 skip_missing=True):
                 user = User.get_by_username(username)
                 if user and not user.active:
                     log.warning('user %s is disabled', username)
                     msg = M(self, 'disabled_account', state)
                     raise formencode.Invalid(
                         msg, value, state, error_dict={'username': msg}
                     )
                 else:
                     log.warning('user `%s` failed to authenticate', username)
                     msg = M(self, 'invalid_username', state)
                     msg2 = M(self, 'invalid_password', state)
                     raise formencode.Invalid(
                         msg, value, state,
                         error_dict={'username': msg, 'password': msg2}
                     )
     return _validator
 
 
 def ValidAuthToken():
     class _validator(formencode.validators.FancyValidator):
         messages = {
             'invalid_token': _(u'Token mismatch')
         }
 
         def validate_python(self, value, state):
             if value != authentication_token():
                 msg = M(self, 'invalid_token', state)
                 raise formencode.Invalid(msg, value, state)
     return _validator
 
 
 def ValidRepoName(edit=False, old_data={}):
     class _validator(formencode.validators.FancyValidator):
         messages = {
             'invalid_repo_name':
                 _(u'Repository name %(repo)s is disallowed'),
             # top level
             'repository_exists': _(u'Repository with name %(repo)s '
                                    u'already exists'),
             'group_exists': _(u'Repository group with name "%(repo)s" '
                               u'already exists'),
             # inside a group
             'repository_in_group_exists': _(u'Repository with name %(repo)s '
                                             u'exists in group "%(group)s"'),
             'group_in_group_exists': _(
                 u'Repository group with name "%(repo)s" '
                 u'exists in group "%(group)s"'),
         }
 
         def _to_python(self, value, state):
             repo_name = repo_name_slug(value.get('repo_name', ''))
             repo_group = value.get('repo_group')
             if repo_group:
                 gr = RepoGroup.get(repo_group)
                 group_path = gr.full_path
                 group_name = gr.group_name
                 # value needs to be aware of group name in order to check
                 # db key This is an actual just the name to store in the
                 # database
                 repo_name_full = group_path + RepoGroup.url_sep() + repo_name
             else:
                 group_name = group_path = ''
                 repo_name_full = repo_name
 
             value['repo_name'] = repo_name
             value['repo_name_full'] = repo_name_full
             value['group_path'] = group_path
             value['group_name'] = group_name
             return value
 
         def validate_python(self, value, state):
 
             repo_name = value.get('repo_name')
             repo_name_full = value.get('repo_name_full')
             group_path = value.get('group_path')
             group_name = value.get('group_name')
 
             if repo_name in [ADMIN_PREFIX, '']:
                 msg = M(self, 'invalid_repo_name', state, repo=repo_name)
                 raise formencode.Invalid(
                     msg, value, state, error_dict={'repo_name': msg})
 
             rename = old_data.get('repo_name') != repo_name_full
             create = not edit
             if rename or create:
 
                 if group_path:
                     if Repository.get_by_repo_name(repo_name_full):
                         msg = M(self, 'repository_in_group_exists', state,
                                 repo=repo_name, group=group_name)
                         raise formencode.Invalid(
                             msg, value, state, error_dict={'repo_name': msg})
                     if RepoGroup.get_by_group_name(repo_name_full):
                         msg = M(self, 'group_in_group_exists', state,
                                 repo=repo_name, group=group_name)
                         raise formencode.Invalid(
                             msg, value, state, error_dict={'repo_name': msg})
                 else:
                     if RepoGroup.get_by_group_name(repo_name_full):
                         msg = M(self, 'group_exists', state, repo=repo_name)
                         raise formencode.Invalid(
                             msg, value, state, error_dict={'repo_name': msg})
 
                     if Repository.get_by_repo_name(repo_name_full):
                         msg = M(
                             self, 'repository_exists', state, repo=repo_name)
                         raise formencode.Invalid(
                             msg, value, state, error_dict={'repo_name': msg})
             return value
     return _validator
 
 
 def ValidForkName(*args, **kwargs):
     return ValidRepoName(*args, **kwargs)
 
 
 def SlugifyName():
     class _validator(formencode.validators.FancyValidator):
 
         def _to_python(self, value, state):
             return repo_name_slug(value)
 
         def validate_python(self, value, state):
             pass
 
     return _validator
 
 
 def ValidCloneUri():
     class InvalidCloneUrl(Exception):
         allowed_prefixes = ()
 
     def url_handler(repo_type, url):
         config = make_db_config(clear_session=False)
         if repo_type == 'hg':
             allowed_prefixes = ('http', 'svn+http', 'git+http')
 
             if 'http' in url[:4]:
                 # initially check if it's at least the proper URL
                 # or does it pass basic auth
                 MercurialRepository.check_url(url, config)
             elif 'svn+http' in url[:8]:  # svn->hg import
                 SubversionRepository.check_url(url, config)
             elif 'git+http' in url[:8]:  # git->hg import
                 raise NotImplementedError()
             else:
                 exc = InvalidCloneUrl('Clone from URI %s not allowed. '
                                       'Allowed url must start with one of %s'
                                       % (url, ','.join(allowed_prefixes)))
                 exc.allowed_prefixes = allowed_prefixes
                 raise exc
 
         elif repo_type == 'git':
             allowed_prefixes = ('http', 'svn+http', 'hg+http')
             if 'http' in url[:4]:
                 # initially check if it's at least the proper URL
                 # or does it pass basic auth
                 GitRepository.check_url(url, config)
             elif 'svn+http' in url[:8]:  # svn->git import
                 raise NotImplementedError()
             elif 'hg+http' in url[:8]:  # hg->git import
                 raise NotImplementedError()
             else:
                 exc = InvalidCloneUrl('Clone from URI %s not allowed. '
                                       'Allowed url must start with one of %s'
                                       % (url, ','.join(allowed_prefixes)))
                 exc.allowed_prefixes = allowed_prefixes
                 raise exc
 
     class _validator(formencode.validators.FancyValidator):
         messages = {
             'clone_uri': _(u'invalid clone url for %(rtype)s repository'),
             'invalid_clone_uri': _(
                 u'Invalid clone url, provide a valid clone '
                 u'url starting with one of %(allowed_prefixes)s')
         }
 
         def validate_python(self, value, state):
             repo_type = value.get('repo_type')
             url = value.get('clone_uri')
 
             if url:
                 try:
                     url_handler(repo_type, url)
                 except InvalidCloneUrl as e:
                     log.warning(e)
                     msg = M(self, 'invalid_clone_uri', rtype=repo_type,
                             allowed_prefixes=','.join(e.allowed_prefixes))
                     raise formencode.Invalid(msg, value, state,
                                              error_dict={'clone_uri': msg})
                 except Exception:
                     log.exception('Url validation failed')
                     msg = M(self, 'clone_uri', rtype=repo_type)
                     raise formencode.Invalid(msg, value, state,
                                              error_dict={'clone_uri': msg})
     return _validator
 
 
 def ValidForkType(old_data={}):
     class _validator(formencode.validators.FancyValidator):
         messages = {
             'invalid_fork_type': _(u'Fork have to be the same type as parent')
         }
 
         def validate_python(self, value, state):
             if old_data['repo_type'] != value:
                 msg = M(self, 'invalid_fork_type', state)
                 raise formencode.Invalid(
                     msg, value, state, error_dict={'repo_type': msg}
                 )
     return _validator
 
 
 def CanWriteGroup(old_data=None):
     class _validator(formencode.validators.FancyValidator):
         messages = {
             'permission_denied': _(
                 u"You do not have the permission "
                 u"to create repositories in this group."),
             'permission_denied_root': _(
                 u"You do not have the permission to store repositories in "
                 u"the root location.")
         }
 
         def _to_python(self, value, state):
             # root location
             if value in [-1, "-1"]:
                 return None
             return value
 
         def validate_python(self, value, state):
             gr = RepoGroup.get(value)
             gr_name = gr.group_name if gr else None  # None means ROOT location
             # create repositories with write permission on group is set to true
             create_on_write = HasPermissionAny(
                 'hg.create.write_on_repogroup.true')()
             group_admin = HasRepoGroupPermissionAny('group.admin')(
                 gr_name, 'can write into group validator')
             group_write = HasRepoGroupPermissionAny('group.write')(
                 gr_name, 'can write into group validator')
             forbidden = not (group_admin or (group_write and create_on_write))
             can_create_repos = HasPermissionAny(
                 'hg.admin', 'hg.create.repository')
             gid = (old_data['repo_group'].get('group_id')
                    if (old_data and 'repo_group' in old_data) else None)
             value_changed = gid != safe_int(value)
             new = not old_data
             # do check if we changed the value, there's a case that someone got
             # revoked write permissions to a repository, he still created, we
             # don't need to check permission if he didn't change the value of
             # groups in form box
             if value_changed or new:
                 # parent group need to be existing
                 if gr and forbidden:
                     msg = M(self, 'permission_denied', state)
                     raise formencode.Invalid(
                         msg, value, state, error_dict={'repo_type': msg}
                     )
                 # check if we can write to root location !
                 elif gr is None and not can_create_repos():
                     msg = M(self, 'permission_denied_root', state)
                     raise formencode.Invalid(
                         msg, value, state, error_dict={'repo_type': msg}
                     )
 
     return _validator
 
 
 def ValidPerms(type_='repo'):
     if type_ == 'repo_group':
         EMPTY_PERM = 'group.none'
     elif type_ == 'repo':
         EMPTY_PERM = 'repository.none'
     elif type_ == 'user_group':
         EMPTY_PERM = 'usergroup.none'
 
     class _validator(formencode.validators.FancyValidator):
         messages = {
             'perm_new_member_name':
                 _(u'This username or user group name is not valid')
         }
 
         def _to_python(self, value, state):
             perm_updates = OrderedSet()
             perm_additions = OrderedSet()
             perm_deletions = OrderedSet()
             # build a list of permission to update/delete and new permission
 
             # Read the perm_new_member/perm_del_member attributes and group
             # them by they IDs
             new_perms_group = defaultdict(dict)
             del_perms_group = defaultdict(dict)
             for k, v in value.copy().iteritems():
                 if k.startswith('perm_del_member'):
                     # delete from org storage so we don't process that later
                     del value[k]
                     # part is `id`, `type`
                     _type, part = k.split('perm_del_member_')
                     args = part.split('_')
                     if len(args) == 2:
                         _key, pos = args
                         del_perms_group[pos][_key] = v
                 if k.startswith('perm_new_member'):
                     # delete from org storage so we don't process that later
                     del value[k]
                     # part is `id`, `type`, `perm`
                     _type, part = k.split('perm_new_member_')
                     args = part.split('_')
                     if len(args) == 2:
                         _key, pos = args
                         new_perms_group[pos][_key] = v
 
             # store the deletes
             for k in sorted(del_perms_group.keys()):
                 perm_dict = del_perms_group[k]
                 del_member = perm_dict.get('id')
                 del_type = perm_dict.get('type')
                 if del_member and del_type:
                     perm_deletions.add((del_member, None, del_type))
 
             # store additions in order of how they were added in web form
             for k in sorted(new_perms_group.keys()):
                 perm_dict = new_perms_group[k]
                 new_member = perm_dict.get('id')
                 new_type = perm_dict.get('type')
                 new_perm = perm_dict.get('perm')
                 if new_member and new_perm and new_type:
                     perm_additions.add((new_member, new_perm, new_type))
 
             # get updates of permissions
             # (read the existing radio button states)
             for k, update_value in value.iteritems():
                 if k.startswith('u_perm_') or k.startswith('g_perm_'):
                     member = k[7:]
                     update_type = {'u': 'user',
                                    'g': 'users_group'}[k[0]]
                     if member == User.DEFAULT_USER:
                         if str2bool(value.get('repo_private')):
                             # set none for default when updating to
                             # private repo protects agains form manipulation
                             update_value = EMPTY_PERM
                     perm_updates.add((member, update_value, update_type))
             # check the deletes
 
             value['perm_additions'] = list(perm_additions)
             value['perm_updates'] = list(perm_updates)
             value['perm_deletions'] = list(perm_deletions)
 
             # validate users they exist and they are active !
             for member_id, _perm, member_type in perm_additions:
                 try:
                     if member_type == 'user':
                         self.user_db = User.query()\
                             .filter(User.active == true())\
                             .filter(User.user_id == member_id).one()
                     if member_type == 'users_group':
                         self.user_db = UserGroup.query()\
                             .filter(UserGroup.users_group_active == true())\
                             .filter(UserGroup.users_group_id == member_id)\
                             .one()
 
                 except Exception:
                     log.exception('Updated permission failed: org_exc:')
                     msg = M(self, 'perm_new_member_type', state)
                     raise formencode.Invalid(
                         msg, value, state, error_dict={
                             'perm_new_member_name': msg}
                     )
             return value
     return _validator
 
 
 def ValidSettings():
     class _validator(formencode.validators.FancyValidator):
         def _to_python(self, value, state):
             # settings  form for users that are not admin
             # can't edit certain parameters, it's extra backup if they mangle
             # with forms
 
             forbidden_params = [
                 'user', 'repo_type', 'repo_enable_locking',
                 'repo_enable_downloads', 'repo_enable_statistics'
             ]
 
             for param in forbidden_params:
                 if param in value:
                     del value[param]
             return value
 
         def validate_python(self, value, state):
             pass
     return _validator
 
 
 def ValidPath():
     class _validator(formencode.validators.FancyValidator):
         messages = {
             'invalid_path': _(u'This is not a valid path')
         }
 
         def validate_python(self, value, state):
             if not os.path.isdir(value):
                 msg = M(self, 'invalid_path', state)
                 raise formencode.Invalid(
                     msg, value, state, error_dict={'paths_root_path': msg}
                 )
     return _validator
 
 
 def UniqSystemEmail(old_data={}):
     class _validator(formencode.validators.FancyValidator):
         messages = {
             'email_taken': _(u'This e-mail address is already taken')
         }
 
         def _to_python(self, value, state):
             return value.lower()
 
         def validate_python(self, value, state):
             if (old_data.get('email') or '').lower() != value:
                 user = User.get_by_email(value, case_insensitive=True)
                 if user:
                     msg = M(self, 'email_taken', state)
                     raise formencode.Invalid(
                         msg, value, state, error_dict={'email': msg}
                     )
     return _validator
 
 
 def ValidSystemEmail():
     class _validator(formencode.validators.FancyValidator):
         messages = {
             'non_existing_email': _(u'e-mail "%(email)s" does not exist.')
         }
 
         def _to_python(self, value, state):
             return value.lower()
 
         def validate_python(self, value, state):
             user = User.get_by_email(value, case_insensitive=True)
             if user is None:
                 msg = M(self, 'non_existing_email', state, email=value)
                 raise formencode.Invalid(
                     msg, value, state, error_dict={'email': msg}
                 )
 
     return _validator
 
 
 def NotReviewedRevisions(repo_id):
     class _validator(formencode.validators.FancyValidator):
         messages = {
             'rev_already_reviewed':
                 _(u'Revisions %(revs)s are already part of pull request '
                   u'or have set status'),
         }
 
         def validate_python(self, value, state):
             # check revisions if they are not reviewed, or a part of another
             # pull request
             statuses = ChangesetStatus.query()\
                 .filter(ChangesetStatus.revision.in_(value))\
                 .filter(ChangesetStatus.repo_id == repo_id)\
                 .all()
 
             errors = []
             for status in statuses:
                 if status.pull_request_id:
                     errors.append(['pull_req', status.revision[:12]])
                 elif status.status:
                     errors.append(['status', status.revision[:12]])
 
             if errors:
                 revs = ','.join([x[1] for x in errors])
                 msg = M(self, 'rev_already_reviewed', state, revs=revs)
                 raise formencode.Invalid(
                     msg, value, state, error_dict={'revisions': revs})
 
     return _validator
 
 
 def ValidIp():
     class _validator(CIDR):
         messages = {
             'badFormat': _(u'Please enter a valid IPv4 or IpV6 address'),
             'illegalBits': _(
                 u'The network size (bits) must be within the range '
                 u'of 0-32 (not %(bits)r)'),
         }
 
         # we ovveride the default to_python() call
         def to_python(self, value, state):
             v = super(_validator, self).to_python(value, state)
             v = v.strip()
             net = ipaddress.ip_network(address=v, strict=False)
             return str(net)
 
         def validate_python(self, value, state):
             try:
                 addr = value.strip()
                 # this raises an ValueError if address is not IpV4 or IpV6
                 ipaddress.ip_network(addr, strict=False)
             except ValueError:
                 raise formencode.Invalid(self.message('badFormat', state),
                                          value, state)
 
     return _validator
 
 
 def FieldKey():
     class _validator(formencode.validators.FancyValidator):
         messages = {
             'badFormat': _(
                 u'Key name can only consist of letters, '
                 u'underscore, dash or numbers'),
         }
 
         def validate_python(self, value, state):
             if not re.match('[a-zA-Z0-9_-]+$', value):
                 raise formencode.Invalid(self.message('badFormat', state),
                                          value, state)
     return _validator
 
 
 def BasePath():
     class _validator(formencode.validators.FancyValidator):
         messages = {
             'badPath': _(u'Filename cannot be inside a directory'),
         }
 
         def _to_python(self, value, state):
             return value
 
         def validate_python(self, value, state):
             if value != os.path.basename(value):
                 raise formencode.Invalid(self.message('badPath', state),
                                          value, state)
     return _validator
 
 
 def ValidAuthPlugins():
     class _validator(formencode.validators.FancyValidator):
         messages = {
             'import_duplicate': _(
                 u'Plugins %(loaded)s and %(next_to_load)s '
                 u'both export the same name'),
+            'missing_includeme': _(
+                u'The plugin "%(plugin_id)s" is missing an includeme '
+                u'function.'),
+            'import_error': _(
+                u'Can not load plugin "%(plugin_id)s"'),
+            'no_plugin': _(
+                u'No plugin available with ID "%(plugin_id)s"'),
         }
 
         def _to_python(self, value, state):
             # filter empty values
             return filter(lambda s: s not in [None, ''], value)
 
-        def validate_python(self, value, state):
-            from rhodecode.authentication.base import loadplugin
-            module_list = value
-            unique_names = {}
+        def _validate_legacy_plugin_id(self, plugin_id, value, state):
+            """
+            Validates that the plugin import works. It also checks that the
+            plugin has an includeme attribute.
+            """
             try:
-                for module in module_list:
-                    if module.startswith(legacy_plugin_prefix):
-                        continue
-                    plugin = loadplugin(module)
-                    plugin_name = plugin.name
-                    if plugin_name in unique_names:
-                        msg = M(self, 'import_duplicate', state,
-                                loaded=unique_names[plugin_name],
-                                next_to_load=plugin_name)
-                        raise formencode.Invalid(msg, value, state)
-                    unique_names[plugin_name] = plugin
-            except (KeyError, AttributeError, TypeError) as e:
-                raise formencode.Invalid(str(e), value, state)
+                plugin = _import_legacy_plugin(plugin_id)
+            except Exception as e:
+                log.exception(
+                    'Exception during import of auth legacy plugin "{}"'
+                    .format(plugin_id))
+                msg = M(self, 'import_error', plugin_id=plugin_id)
+                raise formencode.Invalid(msg, value, state)
+
+            if not hasattr(plugin, 'includeme'):
+                msg = M(self, 'missing_includeme', plugin_id=plugin_id)
+                raise formencode.Invalid(msg, value, state)
+
+            return plugin
+
+        def _validate_plugin_id(self, plugin_id, value, state):
+            """
+            Plugins are already imported during app start up. Therefore this
+            validation only retrieves the plugin from the plugin registry and
+            if it returns something not None everything is OK.
+            """
+            plugin = loadplugin(plugin_id)
+
+            if plugin is None:
+                msg = M(self, 'no_plugin', plugin_id=plugin_id)
+                raise formencode.Invalid(msg, value, state)
+
+            return plugin
+
+        def validate_python(self, value, state):
+            unique_names = {}
+            for plugin_id in value:
+
+                # Validate legacy or normal plugin.
+                if plugin_id.startswith(legacy_plugin_prefix):
+                    plugin = self._validate_legacy_plugin_id(
+                        plugin_id, value, state)
+                else:
+                    plugin = self._validate_plugin_id(plugin_id, value, state)
+
+                # Only allow unique plugin names.
+                if plugin.name in unique_names:
+                    msg = M(self, 'import_duplicate', state,
+                            loaded=unique_names[plugin.name],
+                            next_to_load=plugin)
+                    raise formencode.Invalid(msg, value, state)
+                unique_names[plugin.name] = plugin
 
     return _validator
 
 
 def UniqGistId():
     class _validator(formencode.validators.FancyValidator):
         messages = {
             'gistid_taken': _(u'This gistid is already in use')
         }
 
         def _to_python(self, value, state):
             return repo_name_slug(value.lower())
 
         def validate_python(self, value, state):
             existing = Gist.get_by_access_id(value)
             if existing:
                 msg = M(self, 'gistid_taken', state)
                 raise formencode.Invalid(
                     msg, value, state, error_dict={'gistid': msg}
                 )
 
     return _validator
 
 
 def ValidPattern():
 
     class _Validator(formencode.validators.FancyValidator):
 
         def _to_python(self, value, state):
             patterns = []
 
             prefix = 'new_pattern'
             for name, v in value.iteritems():
                 pattern_name = '_'.join((prefix, 'pattern'))
                 if name.startswith(pattern_name):
                     new_item_id = name[len(pattern_name)+1:]
 
                     def _field(name):
                         return '%s_%s_%s' % (prefix, name, new_item_id)
 
                     values = {
                         'issuetracker_pat': value.get(_field('pattern')),
                         'issuetracker_pat': value.get(_field('pattern')),
                         'issuetracker_url': value.get(_field('url')),
                         'issuetracker_pref': value.get(_field('prefix')),
                         'issuetracker_desc': value.get(_field('description'))
                     }
                     new_uid = md5(values['issuetracker_pat'])
 
                     has_required_fields = (
                         values['issuetracker_pat']
                         and values['issuetracker_url'])
 
                     if has_required_fields:
                         settings = [
                             ('_'.join((key, new_uid)), values[key], 'unicode')
                             for key in values]
                         patterns.append(settings)
 
             value['patterns'] = patterns
             delete_patterns = value.get('uid') or []
             if not isinstance(delete_patterns, (list, tuple)):
                 delete_patterns = [delete_patterns]
             value['delete_patterns'] = delete_patterns
             return value
     return _Validator