Add utility function for creating SNMP sessions

This new function aids in creating nav.Snmp sessions based on
ManagementProfile instances.

python/nav/Snmp/profile.py

@@ -0,0 +1,59 @@
+#
+# Copyright (C) 2023 Sikt
+#
+# This file is part of Network Administration Visualized (NAV).
+#
+# NAV is free software: you can redistribute it and/or modify it under
+# the terms of the GNU General Public License version 3 as published by
+# the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+# FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+# more details.  You should have received a copy of the GNU General Public
+# License along with NAV. If not, see <http://www.gnu.org/licenses/>.
+#
+"""Helper functions to build SNMP sessions from NAV ManagementProfile instances"""
+from functools import partial
+from typing import Callable
+
+from nav.models.manage import Netbox, ManagementProfile
+from nav.Snmp import Snmp
+
+
+def get_snmp_session_for_profile(profile: ManagementProfile) -> Callable:
+    """Returns a nav.Snmp.Snmp constructor partially pre-configured with SNMP options
+    from an SNMP management profile.
+
+    Example usage:
+    >>> netbox = Netbox.objects.get(id=1)
+    >>> snmp = get_snmp_session_for_profile(
+    ...   netbox.get_preferred_snmp_management_profile())
+    >>> session = snmp(netbox.ip)
+    >>> session.get()
+    b'Linux 16e2ac5c6456 6.1.60 #1-NixOS SMP PREEMPT_DYNAMIC Wed Oct 25 10:03:17 UTC 2023 x86_64'
+    >>>
+    """
+    if not profile.is_snmp:
+        raise ValueError("Cannot create SNMP session from non-SNMP management profile")
+
+    if profile.snmp_version < 3:
+        kwargs = {
+            "version": profile.configuration.get("version"),
+            "community": profile.configuration.get("community"),
+        }
+    else:
+        kwargs = {
+            opt: profile.configuration.get(opt) or None
+            for opt in (
+                "sec_level",
+                "auth_protocol",
+                "sec_name",
+                "auth_password",
+                "priv_protocol",
+                "priv_password",
+            )
+        }
+        kwargs["version"] = 3
+
+    return partial(Snmp, **kwargs)

tests/unittests/Snmp/profile_test.py

@@ -0,0 +1,74 @@
+#
+# Copyright (C) 2023 Sikt
+#
+# This file is part of Network Administration Visualized (NAV).
+#
+# NAV is free software: you can redistribute it and/or modify it under
+# the terms of the GNU General Public License version 3 as published by
+# the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+# FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+# more details.  You should have received a copy of the GNU General Public
+# License along with NAV. If not, see <http://www.gnu.org/licenses/>.
+#
+from unittest.mock import Mock
+
+import pytest
+
+from nav.Snmp import Snmp
+from nav.Snmp.profile import get_snmp_session_for_profile
+
+
+class TestGetSnmpSessionForProfile:
+    def test_when_valid_snmpv2_profile_is_given_it_should_return_a_valid_snmp_partial(
+        self, mock_snmpv2_profile
+    ):
+        snmp = get_snmp_session_for_profile(mock_snmpv2_profile)
+        assert callable(snmp)
+        session = snmp("127.0.0.1")
+        assert isinstance(session, Snmp)
+
+    def test_when_valid_snmpv3_profile_is_given_it_should_return_a_valid_snmp_partial(
+        self, mock_snmpv3_profile
+    ):
+        snmp = get_snmp_session_for_profile(mock_snmpv3_profile)
+        assert callable(snmp)
+        session = snmp("127.0.0.1")
+        assert isinstance(session, Snmp)
+
+        conf = mock_snmpv3_profile.configuration
+        assert session.sec_level.value == conf["sec_level"]
+        assert session.auth_protocol.value == conf["auth_protocol"]
+        assert session.sec_name == conf["sec_name"]
+        assert session.auth_password == conf["auth_password"]
+
+    def test_when_non_snmp_profile_is_given_it_should_raise_valueerror(self):
+        profile = Mock(is_snmp=False)
+        with pytest.raises(ValueError):
+            get_snmp_session_for_profile(profile)
+
+
+@pytest.fixture
+def mock_snmpv2_profile():
+    profile = Mock(is_snmp=True, snmp_version=2)
+    profile.configuration = {
+        "version": "2c",
+        "write": False,
+        "community": "public",
+    }
+    return profile
+
+
+@pytest.fixture
+def mock_snmpv3_profile():
+    profile = Mock(is_snmp=True, snmp_version=3)
+    profile.configuration = {
+        "version": "3",
+        "sec_level": "authNoPriv",
+        "auth_protocol": "SHA",
+        "sec_name": "foobar",
+        "auth_password": "zaphodbeeblebrox",
+    }
+    return profile