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#
# This file is part of pysnmp software.
#
# Copyright (c) 2005-2018, Ilya Etingof <etingof@gmail.com>
# License: http://snmplabs.com/pysnmp/license.html
#
from pysnmp.smi.error import NoSuchInstanceError
from pysnmp.proto import errind, error
from pysnmp import debug
__powOfTwoSeq = [128, 64, 32, 16, 8, 4, 2, 1]
# 3.2
class Vacm(object):
"""View-based Access Control Model"""
accessModelID = 3
def isAccessAllowed(self,
snmpEngine,
securityModel,
securityName,
securityLevel,
viewType,
contextName,
variableName):
mibInstrumController = snmpEngine.msgAndPduDsp.mibInstrumController
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))
# 3.2.1
vacmContextEntry, = mibInstrumController.mibBuilder.importSymbols('SNMP-VIEW-BASED-ACM-MIB', 'vacmContextEntry')
tblIdx = vacmContextEntry.getInstIdFromIndices(contextName)
try:
vacmContextName = vacmContextEntry.getNode(
vacmContextEntry.name + (1,) + tblIdx
).syntax
except NoSuchInstanceError:
raise error.StatusInformation(errorIndication=errind.noSuchContext)
# 3.2.2
vacmSecurityToGroupEntry, = mibInstrumController.mibBuilder.importSymbols('SNMP-VIEW-BASED-ACM-MIB',
'vacmSecurityToGroupEntry')
tblIdx = vacmSecurityToGroupEntry.getInstIdFromIndices(
securityModel, securityName
)
try:
vacmGroupName = vacmSecurityToGroupEntry.getNode(
vacmSecurityToGroupEntry.name + (3,) + tblIdx
).syntax
except NoSuchInstanceError:
raise error.StatusInformation(errorIndication=errind.noGroupName)
# 3.2.3
vacmAccessEntry, = mibInstrumController.mibBuilder.importSymbols(
'SNMP-VIEW-BASED-ACM-MIB', 'vacmAccessEntry'
)
# XXX partial context name match
tblIdx = vacmAccessEntry.getInstIdFromIndices(
vacmGroupName, contextName, securityModel, securityLevel
)
# 3.2.4
if viewType == 'read':
entryIdx = vacmAccessEntry.name + (5,) + tblIdx
elif viewType == 'write':
entryIdx = vacmAccessEntry.name + (6,) + tblIdx
elif viewType == 'notify':
entryIdx = vacmAccessEntry.name + (7,) + tblIdx
else:
raise error.ProtocolError('Unknown view type %s' % viewType)
try:
viewName = vacmAccessEntry.getNode(entryIdx).syntax
except NoSuchInstanceError:
raise error.StatusInformation(errorIndication=errind.noAccessEntry)
if not len(viewName):
raise error.StatusInformation(errorIndication=errind.noSuchView)
# XXX split onto object & instance ?
# 3.2.5a
vacmViewTreeFamilyEntry, = mibInstrumController.mibBuilder.importSymbols('SNMP-VIEW-BASED-ACM-MIB',
'vacmViewTreeFamilyEntry')
tblIdx = vacmViewTreeFamilyEntry.getInstIdFromIndices(viewName)
# Walk over entries
initialTreeName = treeName = vacmViewTreeFamilyEntry.name + (2,) + tblIdx
maskName = vacmViewTreeFamilyEntry.name + (3,) + tblIdx
while 1:
vacmViewTreeFamilySubtree = vacmViewTreeFamilyEntry.getNextNode(
treeName
)
vacmViewTreeFamilyMask = vacmViewTreeFamilyEntry.getNextNode(
maskName
)
treeName = vacmViewTreeFamilySubtree.name
maskName = vacmViewTreeFamilyMask.name
if initialTreeName != treeName[:len(initialTreeName)]:
# 3.2.5b
raise error.StatusInformation(errorIndication=errind.notInView)
l = len(vacmViewTreeFamilySubtree.syntax)
if l > len(variableName):
continue
if vacmViewTreeFamilyMask.syntax:
mask = []
for c in vacmViewTreeFamilyMask.syntax.asNumbers():
mask = mask + [b & c for b in __powOfTwoSeq]
m = len(mask) - 1
idx = l - 1
while idx:
if idx > m or mask[idx] and \
vacmViewTreeFamilySubtree.syntax[idx] != variableName[idx]:
break
idx -= 1
if idx:
continue # no match
else: # no mask
if vacmViewTreeFamilySubtree.syntax != variableName[:l]:
continue # no match
# 3.2.5c
return error.StatusInformation(errorIndication=errind.accessAllowed)
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