diff --git a/api/auth/authproviders.py b/api/auth/authproviders.py
index 61a4e1789..e96f258dc 100644
--- a/api/auth/authproviders.py
+++ b/api/auth/authproviders.py
@@ -4,6 +4,8 @@
 import urllib
 import urlparse
 
+from xml.etree import ElementTree
+
 from . import APIAuthProviderException, APIUnknownUserException, APIRefreshTokenException
 from .. import config, util
 from ..dao import dbutil
@@ -189,6 +191,7 @@ def set_user_avatar(self, uid, identity):
         # If the user has no avatar set, mark their provider_avatar as their chosen avatar.
         config.db.users.update_one({'_id': uid, 'avatar': {'$exists': False}}, {'$set':{'avatar': provider_avatar, 'modified': timestamp}})
 
+
 class WechatOAuthProvider(AuthProvider):
 
     def __init__(self):
@@ -278,6 +281,58 @@ def set_user_avatar(self, uid, identity): # pragma: no cover
         pass
 
 
+class CASAuthProvider(AuthProvider):
+
+    def __init__(self):
+        super(CASAuthProvider, self).__init__('cas')
+
+    def validate_code(self, code, **kwargs):
+        uid = self.validate_user(code)
+        return {
+            'access_token': code,
+            'uid': uid,
+            'auth_type': self.auth_type,
+            'expires': datetime.datetime.utcnow() + datetime.timedelta(days=14)
+        }
+
+    def validate_user(self, token):
+        service_url = config.get_item('site', 'redirect_url') + self.config['service_url_state']
+        r = requests.get(self.config['verify_endpoint'], params={'ticket': token, 'service': service_url})
+        if not r.ok:
+            raise APIAuthProviderException('User token not valid')
+
+        username = self._parse_xml_response(r.content)
+        uid = username+'@'+self.config['namespace']
+
+        self.ensure_user_exists(uid)
+        self.set_user_gravatar(uid, uid)
+
+        return uid
+
+    def _parse_xml_response(self, response):
+
+        # parse xml
+        tree = ElementTree.fromstring(response)
+
+        # check to see if xml response labeled request as success
+        # see also: xml parsing in https://github.com/python-cas/python-cas
+        if tree[0].tag.endswith('authenticationSuccess'):
+
+            try:
+                # get username from response
+                namespace = tree.tag[0:tree.tag.index('}')+1]
+                username = tree[0].find('.//' + namespace + 'user').text
+            except Exception as e: # pylint: disable=broad-except
+                config.log.warning(e)
+                raise APIAuthProviderException('Unable to parse response from CAS provider.')
+
+        else:
+            raise APIAuthProviderException('Ticket verification unsuccessful.')
+
+        return username
+
+
+
 class APIKeyAuthProvider(AuthProvider):
     """
     Uses an API key for authentication.
@@ -339,5 +394,6 @@ def validate_user_api_key(key):
     'google'    : GoogleOAuthProvider,
     'ldap'      : JWTAuthProvider,
     'wechat'    : WechatOAuthProvider,
-    'api-key'   : APIKeyAuthProvider
+    'api-key'   : APIKeyAuthProvider,
+    'cas'       : CASAuthProvider
 }
diff --git a/api/config.py b/api/config.py
index a04e08ee4..7bcfc5b6b 100644
--- a/api/config.py
+++ b/api/config.py
@@ -38,7 +38,8 @@
         'redirect_url': 'https://localhost',
         'central_url': 'https://sdmc.scitran.io/api',
         'registered': False,
-        'ssl_cert': None
+        'ssl_cert': None,
+        'inactivity_timeout': None
     },
     'queue': {
         'max_retries': 3,
diff --git a/api/web/base.py b/api/web/base.py
index f2fbb144c..00b282130 100644
--- a/api/web/base.py
+++ b/api/web/base.py
@@ -127,6 +127,27 @@ def authenticate_user_token(self, session_token):
         if cached_token:
             self.request.logger.debug('looked up cached token in %dms', ((datetime.datetime.utcnow() - timestamp).total_seconds() * 1000.))
 
+            # Check if site has inactivity timeout
+            try:
+                inactivity_timeout = config.get_item('site', 'inactivity_timeout')
+            except KeyError:
+                inactivity_timeout = None
+
+            if inactivity_timeout:
+                last_seen = cached_token.get('last_seen')
+
+                # If now - last_seen is greater than inactivity timeout, clear out session
+                if last_seen and (timestamp - last_seen).total_seconds() > inactivity_timeout:
+
+                    # Token expired and no refresh token, remove and deny request
+                    config.db.authtokens.delete_one({'_id': cached_token['_id']})
+                    config.db.refreshtokens.delete({'uid': cached_token['uid'], 'auth_type': cached_token['auth_type']})
+                    self.abort(401, 'Inactivity timeout')
+
+                # set last_seen to now
+                config.db.authtokens.update_one({'_id': cached_token['_id']}, {'$set': {'last_seen': timestamp}})
+
+
             # Check if token is expired
             if cached_token.get('expires') and timestamp > cached_token['expires']:
 
diff --git a/sample.config b/sample.config
index 7ff5f1f69..66bd574cc 100644
--- a/sample.config
+++ b/sample.config
@@ -15,6 +15,7 @@
 #SCITRAN_CORE_DRONE_SECRET=""
 
 #SCITRAN_SITE_ID=""
+#SCITRAN_SITE_INACTIVITY_TIMEOUT=3600
 #SCITRAN_SITE_NAME=""
 #SCITRAN_SITE_URL=""
 #SCITRAN_SITE_API_URL=""
diff --git a/test/unit_tests/python/test_auth.py b/test/unit_tests/python/test_auth.py
index b4081b218..e2a09e9f6 100644
--- a/test/unit_tests/python/test_auth.py
+++ b/test/unit_tests/python/test_auth.py
@@ -61,6 +61,95 @@ def test_jwt_auth(config, as_drone, as_public, api_db):
         api_db.users.delete_one({'_id': uid})
 
 
+def test_cas_auth(config, as_drone, as_public, api_db):
+    # try to login w/ unconfigured auth provider
+    r = as_public.post('/login', json={'auth_type': 'cas', 'code': 'test'})
+    assert r.status_code == 400
+
+    # inject cas auth config
+    config['auth']['cas'] = dict(
+        service_url_state='?state=cas',
+        auth_endpoint='http://cas.test/cas/login',
+        verify_endpoint='http://cas.test/cas/serviceValidate',
+        namespace='cas.test',
+        display_string='CAS Auth')
+
+    username = 'cas'
+    uid = username+'@'+config.auth.cas.namespace
+
+    with requests_mock.Mocker() as m:
+        # try to log in w/ cas and invalid token (=code)
+        m.get(config.auth.cas.verify_endpoint, status_code=400)
+        r = as_public.post('/login', json={'auth_type': 'cas', 'code': 'test'})
+        assert r.status_code == 401
+
+        xml_response_unsuccessful = """
+        <cas:serviceResponse xmlns:cas='http://www.yale.edu/tp/cas'>
+            <cas:authenticationFailure>
+            </cas:authenticationFailure>
+        </cas:serviceResponse>
+        """
+
+        # try to log in w/ cas - pretend provider doesn't return with success
+        m.get(config.auth.cas.verify_endpoint, content=xml_response_unsuccessful)
+        r = as_public.post('/login', json={'auth_type': 'cas', 'code': 'test'})
+        assert r.status_code == 401
+
+        xml_response_malformed = """
+        <cas:serviceResponse xmlns:cas='http://www.yale.edu/tp/cas'>
+            <cas:authenticationSuccess>
+                <cas:bad_key>cas</cas:bad_key>
+            </cas:authenticationSuccess>
+        </cas:serviceResponse>
+        """
+
+        # try to log in w/ cas - pretend provider doesn't return valid username response
+        m.get(config.auth.cas.verify_endpoint, content=xml_response_malformed)
+        r = as_public.post('/login', json={'auth_type': 'cas', 'code': 'test'})
+        assert r.status_code == 401
+
+        xml_response_successful = """
+        <cas:serviceResponse xmlns:cas='http://www.yale.edu/tp/cas'>
+            <cas:authenticationSuccess>
+                <cas:user>cas</cas:user>
+            </cas:authenticationSuccess>
+        </cas:serviceResponse>
+        """
+
+        # try to log in w/ cas - user not in db (yet)
+        m.get(config.auth.cas.verify_endpoint, content=xml_response_successful)
+        r = as_public.post('/login', json={'auth_type': 'cas', 'code': 'test'})
+        assert r.status_code == 402
+
+        # try to log in w/ cas - user added but disabled
+        assert as_drone.post('/users', json={
+            '_id': uid, 'disabled': True, 'firstname': 'test', 'lastname': 'test'}).ok
+        r = as_public.post('/login', json={'auth_type': 'cas', 'code': 'test'})
+        assert r.status_code == 402
+
+        # log in w/ cas (also mock gravatar 404)
+        m.head(re.compile('https://gravatar.com/avatar'), status_code=404)
+        as_drone.put('/users/' + uid, json={'disabled': False})
+        r = as_public.post('/login', json={'auth_type': 'cas', 'code': 'test'})
+        assert r.ok
+        assert 'gravatar' not in api_db.users.find_one({'_id': uid})['avatars']
+        token = r.json['token']
+
+        # access api w/ valid token
+        r = as_public.get('', headers={'Authorization': token})
+        assert r.ok
+
+        # log in w/ cas (now w/ existing gravatar)
+        m.head(re.compile('https://gravatar.com/avatar'))
+        r = as_public.post('/login', json={'auth_type': 'cas', 'code': 'test'})
+        assert r.ok
+        assert 'gravatar' in api_db.users.find_one({'_id': uid})['avatars']
+
+        # clean up
+        api_db.authtokens.delete_one({'_id': token})
+        api_db.users.delete_one({'_id': uid})
+
+
 def test_google_auth(config, as_drone, as_public, api_db):
     # inject google auth client_secret into config
     config['auth']['google']['client_secret'] = 'test'