move ows proxy send_request function under corresponding adapter method

.github/workflows/tests.yml

@@ -42,7 +42,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        python-version: ["3.6", "3.7", "3.8"]
+        python-version: ["3.7", "3.8"]
         allow-failure: [false]
         test-case: [test-local]
         include:
@@ -61,6 +61,11 @@ jobs:
             python-version: None  # doesn't matter which one (in docker), but match default of repo
             allow-failure: false
             test-case: docker-test
+          # deprecated versions
+          - os: ubuntu-20.04
+            python-version: 3.6
+            allow-failure: false
+            test-case: test-local
     steps:
       - uses: actions/checkout@v2
         with:

CHANGES.rst

@@ -4,6 +4,25 @@ Changes
 Unreleased
 ==========
 
+Changes:
+
+* Add ``/ows/verify/{service_name}[/{extra_path}]`` endpoint analoguous to ``/ows/proxy/{service_name}[/{extra_path}]``
+  to only verify if access is granted to this service, for that specific resource path, and for the authenticated user,
+  without performing the proxied request. This can be employed by servers and external entities to validate that
+  authorization will be granted for the user without executing potentially heavy computation or large data transfers
+  from the targeted resource that would otherwise be performed by requesting the ``/ows/proxy`` equivalent location.
+  One usage example of this feature is using |nginx-auth|_ to verify an alternate resource prior to proxying a service
+  request that needs authenticated access to the first resource.
+* Add the OWS proxy ``send_request`` operation under the ``twitcher.adapter`` interface to allow it applying relevant
+  proxying adjustments when using derived implementation. The ``DefaultAdapater`` simply calls the original function
+  that was previously called directly instead of using the adapter's method.
+* Removed the ``extra_path`` and ``request_params`` arguments from OWS proxy ``send_request`` to better align them with
+  arguments from other adapter methods. These parameters are directly retrieved from the ``request`` argument, which was
+  also provided as input to ``send_request``.
+
+.. _nginx-auth: https://docs.nginx.com/nginx/admin-guide/security-controls/configuring-subrequest-authentication/
+.. |nginx-auth| replace:: NGINX Authentication Based on Subrequest Result
+
 0.7.0 (2022-05-11)
 ==================
 

twitcher/adapter/base.py

@@ -85,3 +85,16 @@ def response_hook(self, response, service):
         This method can modify the response to adapt it for specific service logic.
         """
         raise NotImplementedError
+
+    def send_request(self, request, service):
+        # type: (Request, ServiceConfig) -> Response
+        """
+        Performs the provided request in order to obtain a proxied response.
+
+        .. versionadded:: 0.8.0
+
+        The operation should consider the service definition to resolve where the
+        request redirection should be proxied to, and handle any relevant response
+        errors, such as an unauthorized access or an unreachable service.
+        """
+        raise NotImplementedError

twitcher/adapter/default.py

@@ -3,12 +3,20 @@
 """
 
 from twitcher.adapter.base import AdapterInterface
+from twitcher.owsproxy import send_request
 from twitcher.owssecurity import OWSSecurity
 from twitcher.owsregistry import OWSRegistry
 from twitcher.store import ServiceStore
 from twitcher.utils import get_settings
 from pyramid.config import Configurator
 
+from typing import TYPE_CHECKING
+if TYPE_CHECKING:
+    from pyramid.request import Request
+    from pyramid.response import Response
+
+    from twitcher.models.service import ServiceConfig
+
 TWITCHER_ADAPTER_DEFAULT = 'default'
 
 
@@ -43,3 +51,7 @@ def request_hook(self, request, service):
 
     def response_hook(self, response, service):
         return response
+
+    def send_request(self, request, service):
+        # type: (Request, ServiceConfig) -> Response
+        return send_request(request, service)

twitcher/owsproxy.py

@@ -18,7 +18,7 @@
 LOGGER = logging.getLogger('TWITCHER')
 
 if TYPE_CHECKING:
-    from typing import Iterator, Optional
+    from typing import Iterator
 
     from pyramid.config import Configurator
     from pyramid.request import Request
@@ -67,8 +67,14 @@ def __iter__(self):
         return self.resp.iter_content(64 * 1024)
 
 
-def _send_request(request, service, extra_path=None, request_params=None):
-    # type: (Request, ServiceConfig, Optional[str], Optional[str]) -> Response
+def send_request(request, service):
+    # type: (Request, ServiceConfig) -> Response
+    """
+    Send the request to the proxied service and handle its response.
+    """
+
+    extra_path = request.matchdict.get('extra_path')
+    request_params = request.query_string
 
     # TODO: fix way to build url
     url = service['url']
@@ -162,7 +168,6 @@ def owsproxy_view(request):
     # type: (Request) -> Response
     service_name = request.matchdict.get('service_name')
     try:
-        extra_path = request.matchdict.get('extra_path')
         service = request.owsregistry.get_service_by_name(service_name)
         if not service:
             LOGGER.debug("No error raised but service was not found: %s", service_name)
@@ -177,7 +182,7 @@ def owsproxy_view(request):
         # in order to ensure both request/response operations are handled by the same logic
         adapter = request.adapter
         request = adapter.request_hook(request, service)
-        response = _send_request(request, service, extra_path, request_params=request.query_string)
+        response = adapter.send_request(request, service)
         response = adapter.response_hook(response, service)
         return response
     except OWSException as exc:
@@ -188,6 +193,27 @@ def owsproxy_view(request):
         raise OWSNoApplicableCode("Unhandled error: {!s}".format(exc))
 
 
+def owsverify_view(request):
+    # type: (Request) -> Response
+    """
+    Verifies if request access is allowed, but without performing the proxied request and response handling.
+    """
+    message, status, access = "forbidden", 403, False
+    try:
+        service_name = request.matchdict.get('service_name')
+        service = request.owsregistry.get_service_by_name(service_name)
+        if service and request.is_verified:
+            message, status, access = "allowed", 200, True
+    except Exception as exc:
+        LOGGER.exception("Security check failed due to unhandled error.", exc_info=exc)
+        pass
+    return Response(
+        json={"description": "Access to service is {!s}.".format(message), "access": access},
+        status=status,
+        request=request,
+    )
+
+
 def owsproxy_defaultconfig(config):
     # type: (Configurator) -> None
     settings = get_settings(config)
@@ -199,8 +225,12 @@ def owsproxy_defaultconfig(config):
         config.include('twitcher.owssecurity')
         config.add_route('owsproxy', protected_path + '/proxy/{service_name}')
         config.add_route('owsproxy_extra', protected_path + '/proxy/{service_name}/{extra_path:.*}')
+        config.add_route('owsverify', protected_path + '/verify/{service_name}')
+        config.add_route('owsverify_extra', protected_path + '/verify/{service_name}/{extra_path:.*}')
         config.add_view(owsproxy_view, route_name='owsproxy')
         config.add_view(owsproxy_view, route_name='owsproxy_extra')
+        config.add_view(owsverify_view, route_name='owsverify')
+        config.add_view(owsverify_view, route_name='owsverify_extra')
 
 
 def includeme(config):

twitcher/utils.py

@@ -66,12 +66,15 @@ def is_json_serializable(item):
 
 
 def parse_service_name(url, protected_path):
+    # type: (str, str) -> Optional[str]
     parsed_url = urlparse.urlparse(url)
     service_name = None
     if parsed_url.path.startswith(protected_path):
         parts_without_protected_path = parsed_url.path[len(protected_path)::].strip('/').split('/')
-        if 'proxy' in parts_without_protected_path:
-            parts_without_protected_path.remove('proxy')
+        # use ranges to avoid index error in case the path parts list is empty
+        # the expected part must be exactly the first one after the protected path, then followed by the service name
+        if any(part in parts_without_protected_path[:1] for part in ['proxy', 'verify']):
+            parts_without_protected_path = parts_without_protected_path[1:]
         if len(parts_without_protected_path) > 0:
             service_name = parts_without_protected_path[0]
     if not service_name: