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#
# This file is part of pysnmp software.
#
# Copyright (c) 2005-2019, Ilya Etingof <etingof@gmail.com>
# License: http://snmplabs.com/pysnmp/license.html
#
from pysnmp import debug
from pysnmp.proto import errind
from pysnmp.proto import error
from pysnmp.smi.error import NoSuchInstanceError
# 3.2
class Vacm(object):
"""View-based Access Control Model"""
ACCESS_MODEL_ID = 3
_powOfTwoSeq = (128, 64, 32, 16, 8, 4, 2, 1)
def __init__(self):
self._contextBranchId = -1
self._groupNameBranchId = -1
self._accessBranchId = -1
self._viewTreeBranchId = -1
self._contextMap = {}
self._groupNameMap = {}
self._accessMap = {}
self._viewTreeMap = {}
def _addAccessEntry(self, groupName, contextPrefix, securityModel,
securityLevel, prefixMatch, readView, writeView,
notifyView):
if not groupName:
return
groups = self._accessMap
try:
views = groups[groupName]
except KeyError:
views = groups[groupName] = {}
for viewType, viewName in (
('read', readView), ('write', writeView),
('notify', notifyView)):
try:
matches = views[viewType]
except KeyError:
matches = views[viewType] = {}
try:
contexts = matches[prefixMatch]
except KeyError:
contexts = matches[prefixMatch] = {}
try:
models = contexts[contextPrefix]
except KeyError:
models = contexts[contextPrefix] = {}
try:
levels = models[securityModel]
except KeyError:
levels = models[securityModel] = {}
levels[securityLevel] = viewName
def _getFamilyViewName(self, groupName, contextName, securityModel, securityLevel, viewType):
groups = self._accessMap
try:
views = groups[groupName]
except KeyError:
raise error.StatusInformation(errorIndication=errind.noGroupName)
try:
matches = views[viewType]
except KeyError:
raise error.StatusInformation(errorIndication=errind.noAccessEntry)
try:
# vacmAccessTable #2: exact match shortcut
return matches[1][contextName][securityModel][securityLevel]
except KeyError:
pass
# vacmAccessTable #2: fuzzy look-up
candidates = []
for match, names in matches.items():
for context, models in names.items():
if match == 1 and contextName != context:
continue
if match == 2 and contextName[:len(context)] != context:
continue
for model, levels in models.items():
for level, viewName in levels.items():
# priorities:
# - matching securityModel
# - exact context name match
# - longer partial match
# - highest securityLevel
rating = securityModel == model, match == 1, len(context), level
candidates.append((rating, viewName))
if not candidates:
raise error.StatusInformation(errorIndication=errind.notInView)
candidates.sort()
rating, viewName = candidates[0]
return viewName
def isAccessAllowed(self,
snmpEngine,
securityModel,
securityName,
securityLevel,
viewType,
contextName,
variableName):
mibInstrumController = snmpEngine.msgAndPduDsp.mibInstrumController
mibBuilder = mibInstrumController.mibBuilder
debug.logger & debug.flagACL and debug.logger(
'isAccessAllowed: securityModel %s, securityName %s, '
'securityLevel %s, viewType %s, contextName %s for '
'variableName %s' % (securityModel, securityName,
securityLevel, viewType, contextName,
variableName))
# Rebuild contextName map if changed
vacmContextName, = mibInstrumController.mibBuilder.importSymbols(
'SNMP-VIEW-BASED-ACM-MIB', 'vacmContextName')
if self._contextBranchId != vacmContextName.branchVersionId:
self._contextMap.clear()
nextMibNode = vacmContextName
while True:
try:
nextMibNode = vacmContextName.getNextNode(nextMibNode.name)
except NoSuchInstanceError:
break
self._contextMap[nextMibNode.syntax] = True
self._contextBranchId = vacmContextName.branchVersionId
# 3.2.1
if contextName not in self._contextMap:
raise error.StatusInformation(errorIndication=errind.noSuchContext)
# Rebuild groupName map if changed
vacmGroupName, = mibInstrumController.mibBuilder.importSymbols(
'SNMP-VIEW-BASED-ACM-MIB', 'vacmGroupName')
if self._groupNameBranchId != vacmGroupName.branchVersionId:
vacmSecurityToGroupEntry, = mibInstrumController.mibBuilder.importSymbols(
'SNMP-VIEW-BASED-ACM-MIB', 'vacmSecurityToGroupEntry')
self._groupNameMap.clear()
nextMibNode = vacmGroupName
while True:
try:
nextMibNode = vacmGroupName.getNextNode(nextMibNode.name)
except NoSuchInstanceError:
break
instId = nextMibNode.name[len(vacmGroupName.name):]
indices = vacmSecurityToGroupEntry.getIndicesFromInstId(instId)
self._groupNameMap[indices] = nextMibNode.syntax
self._groupNameBranchId = vacmGroupName.branchVersionId
# 3.2.2
indices = securityModel, securityName
try:
groupName = self._groupNameMap[indices]
except KeyError:
raise error.StatusInformation(errorIndication=errind.noGroupName)
# Rebuild access map if changed
vacmAccessStatus, = mibInstrumController.mibBuilder.importSymbols(
'SNMP-VIEW-BASED-ACM-MIB', 'vacmAccessStatus')
if self._accessBranchId != vacmAccessStatus.branchVersionId:
(vacmAccessEntry,
vacmAccessContextPrefix,
vacmAccessSecurityModel,
vacmAccessSecurityLevel,
vacmAccessContextMatch,
vacmAccessReadViewName,
vacmAccessWriteViewName,
vacmAccessNotifyViewName) = mibInstrumController.mibBuilder.importSymbols(
'SNMP-VIEW-BASED-ACM-MIB',
'vacmAccessEntry',
'vacmAccessContextPrefix',
'vacmAccessSecurityModel',
'vacmAccessSecurityLevel',
'vacmAccessContextMatch',
'vacmAccessReadViewName',
'vacmAccessWriteViewName',
'vacmAccessNotifyViewName')
self._accessMap.clear()
nextMibNode = vacmAccessStatus
while True:
try:
nextMibNode = vacmAccessStatus.getNextNode(nextMibNode.name)
except NoSuchInstanceError:
break
if nextMibNode.syntax != 1: # active row
continue
instId = nextMibNode.name[len(vacmAccessStatus.name):]
indices = vacmAccessEntry.getIndicesFromInstId(instId)
vacmGroupName = indices[0]
self._addAccessEntry(
vacmGroupName,
vacmAccessContextPrefix.getNode(
vacmAccessContextPrefix.name + instId).syntax,
vacmAccessSecurityModel.getNode(
vacmAccessSecurityModel.name + instId).syntax,
vacmAccessSecurityLevel.getNode(
vacmAccessSecurityLevel.name + instId).syntax,
vacmAccessContextMatch.getNode(
vacmAccessContextMatch.name + instId).syntax,
vacmAccessReadViewName.getNode(
vacmAccessReadViewName.name + instId).syntax,
vacmAccessWriteViewName.getNode(
vacmAccessWriteViewName.name + instId).syntax,
vacmAccessNotifyViewName.getNode(
vacmAccessNotifyViewName.name + instId).syntax
)
self._accessBranchId = vacmAccessStatus.branchVersionId
viewName = self._getFamilyViewName(
groupName, contextName, securityModel, securityLevel, viewType)
# Rebuild family subtree map if changed
vacmViewTreeFamilyViewName, = mibInstrumController.mibBuilder.importSymbols(
'SNMP-VIEW-BASED-ACM-MIB', 'vacmViewTreeFamilyViewName')
if self._viewTreeBranchId != vacmViewTreeFamilyViewName.branchVersionId:
(vacmViewTreeFamilySubtree,
vacmViewTreeFamilyMask,
vacmViewTreeFamilyType) = mibInstrumController.mibBuilder.importSymbols(
'SNMP-VIEW-BASED-ACM-MIB',
'vacmViewTreeFamilySubtree',
'vacmViewTreeFamilyMask',
'vacmViewTreeFamilyType')
self._viewTreeMap.clear()
powerOfTwo = [2 ** exp for exp in range(7, -1, -1)]
nextMibNode = vacmViewTreeFamilyViewName
while True:
try:
nextMibNode = vacmViewTreeFamilyViewName.getNextNode(
nextMibNode.name)
except NoSuchInstanceError:
break
if nextMibNode.syntax not in self._viewTreeMap:
self._viewTreeMap[nextMibNode.syntax] = []
instId = nextMibNode.name[len(vacmViewTreeFamilyViewName.name):]
subtree = vacmViewTreeFamilySubtree.getNode(
vacmViewTreeFamilySubtree.name + instId).syntax
mask = vacmViewTreeFamilyMask.getNode(
vacmViewTreeFamilyMask.name + instId).syntax
mode = vacmViewTreeFamilyType.getNode(
vacmViewTreeFamilyType.name + instId).syntax
mask = mask.asNumbers()
maskLength = min(len(mask) * 8, len(subtree))
ignoredSubOids = [
i * 8 + j for i, octet in enumerate(mask)
for j, bit in enumerate(powerOfTwo)
if not (bit & octet) and i * 8 + j < maskLength
]
if ignoredSubOids:
pattern = list(subtree)
for ignoredSubOid in ignoredSubOids:
pattern[ignoredSubOid] = 0
subtree = subtree.clone(pattern)
entry = subtree, ignoredSubOids, mode == 1
self._viewTreeMap[nextMibNode.syntax].append(entry)
for entries in self._viewTreeMap.values():
entries.sort(key=lambda x: (len(x[0]), x[0]))
self._viewTreeBranchId = vacmViewTreeFamilyViewName.branchVersionId
# 3.2.5a
indices = viewName
try:
entries = self._viewTreeMap[indices]
except KeyError:
return error.StatusInformation(errorIndication=errind.notInView)
accessAllowed = False
for entry in entries:
subtree, ignoredSubOids, included = entry
if ignoredSubOids:
subOids = list(variableName)
for ignoredSubOid in ignoredSubOids:
subOids[ignoredSubOid] = 0
normalizedVariableName = subtree.clone(subOids)
else:
normalizedVariableName = variableName
if subtree.isPrefixOf(normalizedVariableName):
accessAllowed = included
# 3.2.5c
if not accessAllowed:
raise error.StatusInformation(errorIndication=errind.notInView)
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