Authentication is the process of mapping a request to a user. There are different ways to do this, from simple HTTP Basic Authentication to cookies or token based systems.
Authorization is the process that defines what an authenticated user is allowed to do. A datastore is required to store this authorization information for everything but trivial systems. These datastores can range from really simple text files (all users in this text file are allowed to do everything) to complex schemas with relational databases (user A is allowed to do B but not C, etc.).
As you can see, the options to choose when implementing a system for authentication and authorization are diverse. Developers (of SDIs, not the software itself) often have specific constraints, like existing user data in a database or an existing login page on a website for a Web-GIS. So it is hard to offer a one-size-fits-all solution.
Therefore, MapProxy does not come with any embedded authentication or authorization. But it comes with a flexible authorization interface that allows you (the SDI developer) to implement custom tailored systems.
Luckily, there are lots of existing toolkits that can be used to build systems that match your requirements. For authentication there is the repoze.who package with plugins for HTTP Basic Authentication, HTTP cookies, etc. For authorization there is the repoze.what package with plugins for SQL datastores, etc.
Note
Developing custom authentication and authorization system requires a bit Python programming and knowledge of WSGI and WSGI middleware.
Your auth system should be implemented as a WSGI middleware. The middleware sits between your web server and the MapProxy.
A simple middleware that authorizes random requests might look like:
class RandomAuthFilter(object):
def __init__(self, app, global_conf):
self.app = app
def __call__(self, environ, start_reponse):
if random.randint(0, 1) == 1:
return self.app(environ, start_reponse)
else:
start_reponse('403 Forbidden',
[('content-type', 'text/plain')])
return ['no luck today']
You need to wrap the MapProxy application with your custom auth middleware. For deployment scripts it might look like:
application = make_wsgi_app('./mapproxy.yaml')
application = RandomAuthFilter(application)
For PasteDeploy you can use the filter-with option. The config.ini looks like:
[app:mapproxy]
use = egg:MapProxy#app
mapproxy_conf = %(here)s/mapproxy.yaml
filter-with = auth
[filter:auth]
paste.filter_app_factory = myauthmodule:RandomAuthFilter
[server:main]
...
You can implement simple authentication systems with that method, but you should look at repoze.who before reinventing the wheel.
Authorization is a bit more complex, because your middleware would need to interpret the request to get information required for the authorization (e.g. layer names for WMS GetMap requests). Limiting the GetCapabilities response to certain layers would even require the middleware to manipulate the XML document. So it’s obvious that some parts of the authorization should be handled by MapProxy.
MapProxy can call the middleware back for authorization as soon as it knows what to ask for (e.g. the layer names of a WMS GetMap request). You have to pass a callback function to the environment so that MapProxy knows what to call.
Here is a more elaborate example that denies requests to all layers that start with a specific prefix. These layers are also hidden from capability documents.
class SimpleAuthFilter(object):
"""
Simple MapProxy authorization middleware.
It authorizes WMS requests for layers where the name does
not start with `prefix`.
"""
def __init__(self, app, prefix='secure'):
self.app = app
self.prefix = prefix
def __call__(self, environ, start_reponse):
# put authorize callback function into environment
environ['mapproxy.authorize'] = self.authorize
return self.app(environ, start_reponse)
def authorize(self, service, layers=[], environ=None, **kw):
allowed = denied = False
if service.startswith('wms.'):
auth_layers = {}
for layer in layers:
if layer.startswith(self.prefix):
auth_layers[layer] = {}
denied = True
else:
auth_layers[layer] = {
'map': True,
'featureinfo': True,
'legendgraphic': True,
}
allowed = True
else: # other services are denied
return {'authorized': 'none'}
if allowed and not denied:
return {'authorized': 'full'}
if denied and not allowed:
return {'authorized': 'none'}
return {'authorized': 'partial', 'layers': auth_layers}
And here is the part of the config.py where we define the filter and pass custom options:
application = make_wsgi_app('./mapproxy.yaml')
application = SimpleAuthFilter(application, prefix='secure')
MapProxy looks in the request environment for a mapproxy.authorize entry. This entry should contain a callable (function or method). If it does not find any callable, then MapProxy assumes that authorization is not enabled and that all requests are allowed.
The signature of the authorization function:
| Parameters: |
|
|---|---|
| Return type: | dictionary with authorization information |
The arguments might get extended in future versions of MapProxy. Therefore you should collect further arguments in a catch-all keyword argument (i.e. **kw).
Note
The actual name of the callable is insignificant, only the environment key mapproxy.authorize is important.
The service parameter is a string and the content depends on the service that calls the authorize function. Generally, it is the lower-case name of the service (e.g. tms for TMS service), but it can be different to further control the service (e.g. wms.map).
The function should return a dictionary with the authorization information. The expected content of that dictionary can vary with each service. Only the authorized key is consistent with all services.
The authorized entry can have four values.
fullpartialnoneunauthenticatedrepoze.who‘s PluggableAuthenticationMiddleware will do this for example.New in version 1.1.0: The environment parameter and support for authorized: unauthenticated results.
limited_to¶You can restrict the geographical area for each request. MapProxy will clip each request to the provided geometry – areas outside of the permitted area become transparent.
Depending on the service, MapProxy supports this clipping for the whole request or for each layer. You need to provide a dictionary with bbox or geometry and the srs of the geometry. The following geometry values are supported:
Here is an example callback result for a WMS GetMap request with all three geometry types. See below for examples for other services:
{
'authorized': 'partial',
'layers': {
'layer1': {
'map': True,
'limited_to': {
'geometry': [-10, 0, 30, 50],
'srs': 'EPSG:4326',
},
},
'layer2': {
'map': True,
'limited_to': {
'geometry': 'POLYGON((...))',
'srs': 'EPSG:4326',
},
},
'layer3': {
'map': True,
'limited_to': {
'geometry': shapely.geometry.Polygon(
[(-10, 0), (30, -5), (30, 50), (20, 50)]),
'srs': 'EPSG:4326',
}
}
}
}
The clipping is quite fast, but if you notice that the overhead is to large, you should reduce the complexity of the geometries returned by your authorization callback. You can improve the performance by returning the geometry in the projection from query_extent, by limiting it to the query_extent and by simplifing the geometry. Refer to the ST_Transform, ST_Intersection and ST_SimplifyPreserveTopology functions when you query the geometries from PostGIS.
The WMS service expects a layers entry in the authorization dictionary for partial results. layers itself should be a dictionary with all layers. All missing layers are interpreted as denied layers.
Each layer contains the information about the permitted features. A missing feature is interpreted as a denied feature.
Here is an example result of a call to the authorize function:
{
'authorized': 'partial',
'layers': {
'layer1': {
'map': True,
'featureinfo': False,
},
'layer2': {
'map': True,
'featureinfo': True,
}
}
}
limited_to¶New in version 1.4.0.
The WMS service supports limited_to for GetCapabilities, GetMap and GetFeatureInfo requests. MapProxy will modify the bounding box of each restricted layer for GetCapabilities requests. GetFeatureInfo requests will only return data if the info coordinate is inside the permitted area. For GetMap requests, MapProxy will clip each layer to the provided geometry – areas outside of the permitted area become transparent or colored in the bgcolor of the WMS request.
You can provide the geometry for each layer or for the whole request.
See limited_to for more details.
Here is an example callback result with two limited layers and one unlimited layer:
{
'authorized': 'partial',
'layers': {
'layer1': {
'map': True,
'limited_to': {
'geometry': [-10, 0, 30, 50],
'srs': 'EPSG:4326',
},
},
'layer2': {
'map': True,
'limited_to': {
'geometry': 'POLYGON((...))',
'srs': 'EPSG:4326',
},
},
'layer3': {
'map': True,
}
}
}
Here is an example callback result where the complete request is limited:
{
'authorized': 'partial',
'limited_to': {
'geometry': shapely.geometry.Polygon(
[(-10, 0), (30, -5), (30, 50), (20, 50)]),
'srs': 'EPSG:4326',
},
'layers': {
'layer1': {
'map': True,
},
}
}
The WMS service uses the following service strings:
wms.map¶This is called for WMS GetMap requests. layers is a list with the actual layers to render, that means that group layers are resolved.
The map feature needs to be set to True for each permitted layer.
The whole request is rejected if any requested layer is not permitted. Resolved layers (i.e. sub layers of a requested group layer) are filtered out if they are not permitted.
New in version 1.1.0: The authorize function gets called with an additional query_extent argument:
authorize(service, environ, layers, query_extent, **kw)| Parameters: | query_extent – a tuple of the SRS (e.g. EPSG:4326) and the BBOX
of the request to authorize. |
|---|
With a layer tree like:
- name: layer1
layers:
- name: layer1a
sources: [l1a]
- name: layer1b
sources: [l1b]
An authorize result of:
{
'authorized': 'partial',
'layers': {
'layer1': {'map': True},
'layer1a': {'map': True}
}
}
Results in the following:
layer1 renders layer1a, layer1b gets filtered out.layer1a renders layer1a.layer1b is rejected.layer1a and layer1b is rejected.wms.featureinfo¶This is called for WMS GetFeatureInfo requests and the behavior is similar to wms.map.
wms.capabilities¶This is called for WMS GetCapabilities requests. layers is a list with all named layers of the WMS service.
Only layers with the map feature set to True are included in the capabilities document. Missing layers are not included.
Sub layers are only included when the parent layer is included, since authorization interface is not able to reorder the layer tree. Note, that you are still able to request these sub layers (see wms.map above).
Layers that are queryable and only marked so in the capabilities if the featureinfo feature set to True.
With a layer tree like:
- name: layer1
layers:
- name: layer1a
sources: [l1a]
- name: layer1b
sources: [l1b]
- name: layer1c
sources: [l1c]
An authorize result of:
{
'authorized': 'partial',
'layers': {
'layer1': {'map': True, 'feature': True},
'layer1a': {'map': True, 'feature': True},
'layer1b': {'map': True},
'layer1c': {'map': True},
}
}
Results in the following abbreviated capabilities:
<Layer queryable="1">
<Name>layer1</Name>
<Layer queryable="1"><Name>layer1a</Name></Layer>
<Layer><Name>layer1b</Name></Layer>
</Layer>
The TMS service expects a layers entry in the authorization dictionary for partial results. layers itself should be a dictionary with all layers. All missing layers are interpreted as denied layers.
Each layer contains the information about the permitted features. The TMS service only supports the tile feature. A missing feature is interpreted as a denied feature.
Here is an example result of a call to the authorize function:
{
'authorized': 'partial',
'layers': {
'layer1': {'tile': True},
'layer2': {'tile': False},
}
}
The TMS service uses tms as the service string for all authorization requests.
Only layers with the tile feature set to True are included in the TMS capabilities document (/tms/1.0.0). Missing layers are not included.
The authorize function gets called with an additional query_extent argument for all tile requests:
authorize(service, environ, layers, query_extent=None, **kw)| Parameters: | query_extent – a tuple of the SRS (e.g. EPSG:4326) and the BBOX
of the request to authorize, or None for capabilities requests. |
|---|
limited_to¶New in version 1.5.0.
MapProxy will clip each tile to the provided geometry – areas outside of the permitted area become transparent. MapProxy will return PNG images in this case.
Here is an example callback result where the tile request is limited:
{
'authorized': 'partial',
'limited_to': {
'geometry': shapely.geometry.Polygon(
[(-10, 0), (30, -5), (30, 50), (20, 50)]),
'srs': 'EPSG:4326',
},
'layers': {
'layer1': {
'tile': True,
},
}
}
New in version 1.5.1.
You can also add the limit to the layer and mix it with properties used for the other services:
{
'authorized': 'partial',
'layers': {
'layer1': {
'tile': True,
'map': True,
'limited_to': {
'geometry': shapely.geometry.Polygon(
[(-10, 0), (30, -5), (30, 50), (20, 50)]),
'srs': 'EPSG:4326',
},
'layer2': {
'tile': True,
'map': False,
'featureinfo': True,
'limited_to': {
'geometry': shapely.geometry.Polygon(
[(0, 0), (20, -5), (30, 50), (20, 50)]),
'srs': 'EPSG:4326',
},
},
}
}
See limited_to for more details.
The KML authorization is similar to the TMS authorization, including the limited_to option.
The KML service uses kml as the service string for all authorization requests.
The WMTS authorization is similar to the TMS authorization, including the limited_to option.
The WMTS service uses wmts as the service string for all authorization requests.
The demo service only supports full or none authorization. layers is always an empty list. The demo service does not authorize the services and layers that are listed in the overview page. If you permit a user to access the demo service, then he can see all services and layers names. However, access to these services is still restricted to the according authorization.
The service string is demo.
The MultiMapProxy application stores the instance name in the environment as mapproxy.instance_name. This information in not available when your middleware gets called, but you can use it in your authorization function.
Example that rejects MapProxy instances where the name starts with secure.
class MultiMapProxyAuthFilter(object):
def __init__(self, app, global_conf):
self.app = app
def __call__(self, environ, start_reponse):
environ['mapproxy.authorize'] = self.authorize
return self.app(environ, start_reponse)
def authorize(self, service, layers=[]):
instance_name = environ.get('mapproxy.instance_name', '')
if instance_name.startswith('secure'):
return {'authorized': 'none'}
else:
return {'authorized': 'full'}