Return the ResponseLocation before falling back to Locationfeature-logout-response-location

ResponseLocation [Optional]

    Optionally specifies a different location to which response messages sent as part of
    the protocol or profile should be sent. The allowable syntax of this URI depends on
    the protocol binding.

The ResponseLocation attribute is used to enable different endpoints to be specified for
receiving request and response messages associated with a protocol or profile, not as a
means of load-balancing or redundancy (multiple elements of this type can be included
for this purpose). When a role contains an element of this type pertaining to a protocol
or profile for which only a single type of message (request or response) is applicable,
then the ResponseLocation attribute is unused. [E41]If the ResponseLocation attribute is
omitted, any response messages associated with a protocol or profile may be assumed to
be handled at the URI indicated by the Location attribute.

ArtifactResolutionService, SingleSignOnService and NameIDMappingService MUST omit the
ResponseLocation attribute. This is enforced here, but metadata with such service
declarations and such attributes should not have been part of the metadata store in the
first place.

Signed-off-by: Ivan Kanakarakis <ivan.kanak@gmail.com>

4 files changed, 74 insertions, 33 deletions

diff --git a/src/saml2/client.py b/src/saml2/client.py
index e283420a..60b108ef 100644
--- a/src/saml2/client.py
+++ b/src/saml2/client.py
@@ -29,7 +29,7 @@ from saml2.client_base import Base
 from saml2.client_base import SignOnError
 from saml2.client_base import LogoutError
 from saml2.client_base import NoServiceDefined
-from saml2.mdstore import destinations
+from saml2.mdstore import locations
 
 import logging
 
@@ -209,7 +209,7 @@ class Saml2Client(Base):
                     logger.debug("No SLO '%s' service", binding)
                     continue
 
-                destination = destinations(srvs)[0]
+                destination = next(locations(srvs), None)
                 logger.info("destination to provider: %s", destination)
                 try:
                     session_info = self.users.get_info_from(name_id,
@@ -374,7 +374,7 @@ class Saml2Client(Base):
                                 name_qualifier=name_qualifier))
 
         srvs = self.metadata.authz_service(entity_id, BINDING_SOAP)
-        for dest in destinations(srvs):
+        for dest in locations(srvs):
             resp = self._use_soap(dest, "authz_decision_query",
                                   action=action, evidence=evidence,
                                   resource=resource, subject=subject)
@@ -397,7 +397,7 @@ class Saml2Client(Base):
 
         _id_refs = [AssertionIDRef(_id) for _id in assertion_ids]
 
-        for destination in destinations(srvs):
+        for destination in locations(srvs):
             res = self._use_soap(destination, "assertion_id_request",
                                  assertion_id_refs=_id_refs, consent=consent,
                                  extensions=extensions, sign=sign)
@@ -411,7 +411,7 @@ class Saml2Client(Base):
 
         srvs = self.metadata.authn_request_service(entity_id, BINDING_SOAP)
 
-        for destination in destinations(srvs):
+        for destination in locations(srvs):
             resp = self._use_soap(destination, "authn_query", consent=consent,
                                   extensions=extensions, sign=sign)
             if resp:
@@ -461,7 +461,7 @@ class Saml2Client(Base):
             if srvs is []:
                 raise SAMLError("No attribute service support at entity")
 
-            destination = destinations(srvs)[0]
+            destination = next(locations(srvs), None)
 
         if binding == BINDING_SOAP:
             return self._use_soap(destination, "attribute_query",
diff --git a/src/saml2/client_base.py b/src/saml2/client_base.py
index 871f3f2c..51a3a574 100644
--- a/src/saml2/client_base.py
+++ b/src/saml2/client_base.py
@@ -12,7 +12,7 @@ import logging
 
 from saml2.entity import Entity
 
-from saml2.mdstore import destinations
+from saml2.mdstore import locations
 from saml2.profile import paos, ecp
 from saml2.saml import NAMEID_FORMAT_PERSISTENT
 from saml2.saml import NAMEID_FORMAT_TRANSIENT
@@ -212,7 +212,7 @@ class Base(Entity):
             # verify that it's in the metadata
             srvs = self.metadata.single_sign_on_service(entityid, binding)
             if srvs:
-                return destinations(srvs)[0]
+                return next(locations(srvs), None)
             else:
                 logger.info("_sso_location: %s, %s", entityid, binding)
                 raise IdpUnspecified("No IdP to send to given the premises")
@@ -224,9 +224,8 @@ class Base(Entity):
             raise IdpUnspecified("Too many IdPs to choose from: %s" % eids)
 
         try:
-            srvs = self.metadata.single_sign_on_service(list(eids.keys())[0],
-                                                        binding)
-            return destinations(srvs)[0]
+            srvs = self.metadata.single_sign_on_service(list(eids.keys())[0], binding)
+            return next(locations(srvs), None)
         except IndexError:
             raise IdpUnspecified("No IdP to send to given the premises")
 
diff --git a/src/saml2/entity.py b/src/saml2/entity.py
index fad9326a..c9572aef 100644
--- a/src/saml2/entity.py
+++ b/src/saml2/entity.py
@@ -53,7 +53,7 @@ from saml2.samlp import ArtifactResponse
 from saml2.samlp import Artifact
 from saml2.samlp import LogoutRequest
 from saml2.samlp import AttributeQuery
-from saml2.mdstore import destinations, response_destinations
+from saml2.mdstore import all_locations
 from saml2 import BINDING_HTTP_POST
 from saml2 import BINDING_HTTP_REDIRECT
 from saml2 import BINDING_SOAP
@@ -249,8 +249,9 @@ class Entity(HTTPBase):
 
         return info
 
-    def pick_binding(self, service, bindings=None, descr_type="", request=None,
-                     entity_id="", response=False):
+    def pick_binding(
+        self, service, bindings=None, descr_type="", request=None, entity_id=""
+    ):
         if request and not entity_id:
             entity_id = request.issuer.text.strip()
 
@@ -284,10 +285,8 @@ class Entity(HTTPBase):
                             if srv["index"] == _index:
                                 return binding, srv["location"]
                     else:
-                        if response:
-                            return binding, response_destinations(srvs)[0]
-                        else:
-                            return binding, destinations(srvs)[0]
+                        destination = next(all_locations(srvs), None)
+                        return binding, destination
             except UnsupportedBinding:
                 pass
 
@@ -352,10 +351,9 @@ class Entity(HTTPBase):
                 else:
                     descr_type = "spsso"
 
-            binding, destination = self.pick_binding(rsrv, bindings,
-                                                     descr_type=descr_type,
-                                                     request=message,
-                                                     response=True)
+            binding, destination = self.pick_binding(
+                rsrv, bindings, descr_type=descr_type, request=message
+            )
             info["binding"] = binding
             info["destination"] = destination
 
diff --git a/src/saml2/mdstore.py b/src/saml2/mdstore.py
index 41e521ec..3dfd0e5a 100644
--- a/src/saml2/mdstore.py
+++ b/src/saml2/mdstore.py
@@ -5,6 +5,8 @@ import json
 import logging
 import os
 import sys
+from itertools import chain
+from warnings import warn as _warn
 
 from hashlib import sha1
 from os.path import isfile
@@ -26,7 +28,11 @@ from saml2 import BINDING_SOAP
 from saml2.httpbase import HTTPBase
 from saml2.extension.idpdisc import BINDING_DISCO
 from saml2.extension.idpdisc import DiscoveryResponse
+from saml2.md import NAMESPACE as NS_MD
 from saml2.md import EntitiesDescriptor
+from saml2.md import ArtifactResolutionService
+from saml2.md import NameIDMappingService
+from saml2.md import SingleSignOnService
 from saml2.mdie import to_dict
 from saml2.s_utils import UnsupportedBinding
 from saml2.s_utils import UnknownSystemEntity
@@ -70,6 +76,9 @@ classnames = {
         ns=NS_MDUI, tag=PrivacyStatementURL.c_tag
     ),
     "mdui_uiinfo_logo": "{ns}&{tag}".format(ns=NS_MDUI, tag=Logo.c_tag),
+    "service_artifact_resolution": "{ns}&{tag}".format(ns=NS_MD, tag=ArtifactResolutionService.c_tag),
+    "service_single_sign_on": "{ns}&{tag}".format(ns=NS_MD, tag=SingleSignOnService.c_tag),
+    "service_nameid_mapping": "{ns}&{tag}".format(ns=NS_MD, tag=NameIDMappingService.c_tag),
 }
 
 ENTITY_CATEGORY = "http://macedir.org/entity-category"
@@ -79,8 +88,6 @@ ASSURANCE_CERTIFICATION = "urn:oasis:names:tc:SAML:attribute:assurance-certifica
 SAML_METADATA_CONTENT_TYPE = "application/samlmetadata+xml"
 DEFAULT_FRESHNESS_PERIOD = "P0Y0M0DT12H0M0S"
 
-
-
 REQ2SRV = {
     # IDP
     "authn_request": "single_sign_on_service",
@@ -149,17 +156,54 @@ def metadata_modules():
     return _res
 
 
-def response_destinations(srvs):
-    _res = []
-    for s in srvs:
-        if "response_location" in s:
-            _res.append(s["response_location"])
-        else:
-            _res.append(s["location"])
-    return _res
+def response_locations(srvs):
+    """
+    Return the ResponseLocation attributes mapped to the services.
+
+    ArtifactResolutionService, SingleSignOnService and NameIDMappingService MUST omit
+    the ResponseLocation attribute. This is enforced here, but metadata with such
+    service declarations and such attributes should not have been part of the metadata
+    store in the first place.
+    """
+    values = (
+        s["response_location"]
+        for s in srvs
+        if "response_location" in s
+        if s["__class__"] not in [
+            classnames["service_artifact_resolution"],
+            classnames["service_single_sign_on"],
+            classnames["service_nameid_mapping"],
+        ]
+    )
+    return values
+
+
+def locations(srvs):
+    values = (
+        s["location"]
+        for s in srvs
+        if "location" in s
+    )
+    return values
+
 
 def destinations(srvs):
-    return [s["location"] for s in srvs]
+    warn_msg = (
+        "`saml2.mdstore.destinations` function is deprecated; "
+        "instead, use `saml2.mdstore.locations` or `saml2.mdstore.all_locations`."
+    )
+    logger.warning(warn_msg)
+    _warn(warn_msg)
+    values = list(locations(srvs))
+    return values
+
+
+def all_locations(srvs):
+    values = chain(
+        response_locations(srvs),
+        locations(srvs),
+    )
+    return values
 
 
 def attribute_requirement(entity, index=None):