14. Authentication infrastructure

Rada

The code snippets on this page need the following imports if you’re outside the pyqgis console:

from qgis.core import (
  QgsApplication,
  QgsRasterLayer,
  QgsAuthMethodConfig,
  QgsDataSourceUri,
  QgsPkiBundle,
  QgsMessageLog,
)

from qgis.gui import (
    QgsAuthAuthoritiesEditor,
    QgsAuthConfigEditor,
    QgsAuthConfigSelect,
    QgsAuthSettingsWidget,
)

from qgis.PyQt.QtWidgets import (
    QWidget,
    QTabWidget,
)

from qgis.PyQt.QtNetwork import QSslCertificate

14.1. Úvod 

User reference of the Authentication infrastructure can be read in the User Manual in the Authentication System Overview paragraph.

This chapter describes the best practices to use the Authentication system from a developer perspective.

The authentication system is widely used in QGIS Desktop by data providers whenever credentials are required to access a particular resource, for example when a layer establishes a connection to a Postgres database.

There are also a few widgets in the QGIS gui library that plugin developers can use to easily integrate the authentication infrastructure into their code:

A good code reference can be read from the authentication infrastructure tests code.

Varování

Due to the security constraints that were taken into account during the authentication infrastructure design, only a selected subset of the internal methods are exposed to Python.

14.2. Glossary 

Here are some definition of the most common objects treated in this chapter.

Master Password: Password to allow access and decrypt credential stored in the QGIS Authentication DB
Authentication Database: A Master Password crypted sqlite db qgis-auth.db where Authentication Configuration are stored. e.g user/password, personal certificates and keys, Certificate Authorities
Authentication DB: Authentication Database
Authentication Configuration: A set of authentication data depending on Authentication Method. e.g Basic authentication method stores the couple of user/password.
Authentication Config: Authentication Configuration
Authentication Method: A specific method used to get authenticated. Each method has its own protocol used to gain the authenticated level. Each method is implemented as shared library loaded dynamically during QGIS authentication infrastructure init.

14.3. QgsAuthManager the entry point 

The QgsAuthManager singleton is the entry point to use the credentials stored in the QGIS encrypted Authentication DB, i.e. the qgis-auth.db file under the active user profile folder.

This class takes care of the user interaction: by asking to set a master password or by transparently using it to access encrypted stored information.

14.3.1. Init the manager and set the master password 

The following snippet gives an example to set master password to open the access to the authentication settings. Code comments are important to understand the snippet.

authMgr = QgsApplication.authManager()

# check if QgsAuthManager has already been initialized... a side effect
# of the QgsAuthManager.init() is that AuthDbPath is set.
# QgsAuthManager.init() is executed during QGIS application init and hence
# you do not normally need to call it directly.
if authMgr.authenticationDatabasePath():
    # already initialized => we are inside a QGIS app.
    if authMgr.masterPasswordIsSet():
        msg = 'Authentication master password not recognized'
        assert authMgr.masterPasswordSame("your master password"), msg
    else:
        msg = 'Master password could not be set'
        # The verify parameter checks if the hash of the password was
        # already saved in the authentication db
        assert authMgr.setMasterPassword("your master password",
                                          verify=True), msg
else:
    # outside qgis, e.g. in a testing environment => setup env var before
    # db init
    os.environ['QGIS_AUTH_DB_DIR_PATH'] = "/path/where/located/qgis-auth.db"
    msg = 'Master password could not be set'
    assert authMgr.setMasterPassword("your master password", True), msg
    authMgr.init("/path/where/located/qgis-auth.db")

14.3.2. Populate authdb with a new Authentication Configuration entry 

Any stored credential is a Authentication Configuration instance of the QgsAuthMethodConfig class accessed using a unique string like the following one:

authcfg = 'fm1s770'

that string is generated automatically when creating an entry using the QGIS API or GUI, but it might be useful to manually set it to a known value in case the configuration must be shared (with different credentials) between multiple users within an organization.

QgsAuthMethodConfig is the base class for any Authentication Method. Any Authentication Method sets a configuration hash map where authentication information will be stored. Hereafter a useful snippet to store PKI-path credentials for a hypothetical alice user:

authMgr = QgsApplication.authManager()
# set alice PKI data
config = QgsAuthMethodConfig()
config.setName("alice")
config.setMethod("PKI-Paths")
config.setUri("https://example.com")
config.setConfig("certpath", "path/to/alice-cert.pem" )
config.setConfig("keypath", "path/to/alice-key.pem" )
# check if method parameters are correctly set
assert config.isValid()

# register alice data in authdb returning the ``authcfg`` of the stored
# configuration
authMgr.storeAuthenticationConfig(config)
newAuthCfgId = config.id()
assert newAuthCfgId

14.3.2.1. Available Authentication methods 

Authentication Method libraries are loaded dynamically during authentication manager init. Available authentication methods are:

Basic User and password authentication
EsriToken ESRI token based authentication
Identity-Cert Identity certificate authentication
OAuth2 OAuth2 authentication
PKI-Paths PKI paths authentication
PKI-PKCS#12 PKI PKCS#12 authentication

14.3.2.2. Populate Authorities 

authMgr = QgsApplication.authManager()
# add authorities
cacerts = QSslCertificate.fromPath( "/path/to/ca_chains.pem" )
assert cacerts is not None
# store CA
authMgr.storeCertAuthorities(cacerts)
# and rebuild CA caches
authMgr.rebuildCaCertsCache()
authMgr.rebuildTrustedCaCertsCache()

14.3.2.3. Manage PKI bundles with QgsPkiBundle 

A convenience class to pack PKI bundles composed on SslCert, SslKey and CA chain is the QgsPkiBundle class. Hereafter a snippet to get password protected:

# add alice cert in case of key with pwd
caBundlesList = []  # List of CA bundles
bundle = QgsPkiBundle.fromPemPaths( "/path/to/alice-cert.pem",
                                     "/path/to/alice-key_w-pass.pem",
                                     "unlock_pwd",
                                     caBundlesList )
assert bundle is not None
# You can check bundle validity by calling:
# bundle.isValid()

Refer to QgsPkiBundle class documentation to extract cert/key/CAs from the bundle.

14.3.3. Remove an entry from authdb 

We can remove an entry from Authentication Database using it’s authcfg identifier with the following snippet:

authMgr = QgsApplication.authManager()
authMgr.removeAuthenticationConfig( "authCfg_Id_to_remove" )

14.3.4. Leave authcfg expansion to QgsAuthManager 

The best way to use an Authentication Config stored in the Authentication DB is referring it with the unique identifier authcfg. Expanding, means convert it from an identifier to a complete set of credentials. The best practice to use stored Authentication Configs, is to leave it managed automatically by the Authentication manager. The common use of a stored configuration is to connect to an authentication enabled service like a WMS or WFS or to a DB connection.

Poznámka

Take into account that not all QGIS data providers are integrated with the Authentication infrastructure. Each authentication method, derived from the base class QgsAuthMethod and support a different set of Providers. For example the certIdentity() method supports the following list of providers:

authM = QgsApplication.authManager()
print(authM.authMethod("Identity-Cert").supportedDataProviders())

Sample output:

['ows', 'wfs', 'wcs', 'wms', 'postgres']

For example, to access a WMS service using stored credentials identified with authcfg = 'fm1s770', we just have to use the authcfg in the data source URL like in the following snippet:

authCfg = 'fm1s770'
quri = QgsDataSourceUri()
quri.setParam("layers", 'usa:states')
quri.setParam("styles", '')
quri.setParam("format", 'image/png')
quri.setParam("crs", 'EPSG:4326')
quri.setParam("dpiMode", '7')
quri.setParam("featureCount", '10')
quri.setParam("authcfg", authCfg)   # <---- here my authCfg url parameter
quri.setParam("contextualWMSLegend", '0')
quri.setParam("url", 'https://my_auth_enabled_server_ip/wms')
rlayer = QgsRasterLayer(str(quri.encodedUri(), "utf-8"), 'states', 'wms')

In the upper case, the wms provider will take care to expand authcfg URI parameter with credential just before setting the HTTP connection.

Varování

The developer would have to leave authcfg expansion to the QgsAuthManager, in this way he will be sure that expansion is not done too early.

Usually an URI string, built using the QgsDataSourceURI class, is used to set a data source in the following way:

authCfg = 'fm1s770'
quri = QgsDataSourceUri("my WMS uri here")
quri.setParam("authcfg", authCfg)
rlayer = QgsRasterLayer( quri.uri(False), 'states', 'wms')

Poznámka

The False parameter is important to avoid URI complete expansion of the authcfg id present in the URI.

14.3.4.1. PKI examples with other data providers 

Other example can be read directly in the QGIS tests upstream as in test_authmanager_pki_ows or test_authmanager_pki_postgres.

14.4. Adapt plugins to use Authentication infrastructure 

Many third party plugins are using httplib2 or other Python networking libraries to manage HTTP connections instead of integrating with QgsNetworkAccessManager and its related Authentication Infrastructure integration.

To facilitate this integration a helper Python function has been created called NetworkAccessManager. Its code can be found here.

This helper class can be used as in the following snippet:

http = NetworkAccessManager(authid="my_authCfg", exception_class=My_FailedRequestError)
try:
  response, content = http.request( "my_rest_url" )
except My_FailedRequestError, e:
  # Handle exception
  pass

14.5. Authentication GUIs 

In this paragraph are listed the available GUIs useful to integrate authentication infrastructure in custom interfaces.

14.5.1. GUI to select credentials 

If it’s necessary to select a Authentication Configuration from the set stored in the Authentication DB it is available in the GUI class QgsAuthConfigSelect.

and can be used as in the following snippet:

# create the instance of the QgsAuthConfigSelect GUI hierarchically linked to
# the widget referred with `parent`
parent = QWidget()  # Your GUI parent widget
gui = QgsAuthConfigSelect( parent, "postgres" )
# add the above created gui in a new tab of the interface where the
# GUI has to be integrated
tabGui = QTabWidget()
tabGui.insertTab( 1, gui, "Configurations" )

The above example is taken from the QGIS source code. The second parameter of the GUI constructor refers to data provider type. The parameter is used to restrict the compatible Authentication Methods with the specified provider.

14.5.2. Authentication Editor GUI 

The complete GUI used to manage credentials, authorities and to access to Authentication utilities is managed by the QgsAuthEditorWidgets class.

and can be used as in the following snippet:

# create the instance of the QgsAuthEditorWidgets GUI hierarchically linked to
# the widget referred with `parent`
parent = QWidget()  # Your GUI parent widget
gui = QgsAuthConfigSelect( parent )
gui.show()

An integrated example can be found in the related test.

14.5.3. Authorities Editor GUI 

A GUI used to manage only authorities is managed by the QgsAuthAuthoritiesEditor class.

../../_images/QgsAuthAuthoritiesEditor.png

and can be used as in the following snippet:

# create the instance of the QgsAuthAuthoritiesEditor GUI hierarchically
#  linked to the widget referred with `parent`
parent = QWidget()  # Your GUI parent widget
gui = QgsAuthAuthoritiesEditor( parent )
gui.show()