Fix: UpdateDiscoveryValues overwrites user-configured ContextName from Report PDUs#28
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missaak wants to merge 1 commit into
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Fix: UpdateDiscoveryValues overwrites user-configured ContextName from Report PDUs#28missaak wants to merge 1 commit into
missaak wants to merge 1 commit into
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…teDiscoveryValues UpdateDiscoveryValues() unconditionally overwrites _contextName and _contextEngineId with values from the incoming packet's ScopedPdu. When processing SNMPv3 Report PDUs (e.g. usmStatsNotInTimeWindows), these fields in the Report are typically empty, which destroys any user-configured context values. This causes SNMPv3 communication to fail with snmpUnavailableContexts on devices that require a non-empty context name for VACM access control. Per RFC 3414 (USM) Section 3.2 and RFC 3412 Section 7.2, the contextName is a locally-configured value that identifies the MIB view for the request. Report PDUs are administrative responses for engine synchronization and should not alter the manager's context configuration. The fix preserves user-set ContextName and ContextEngineId by only updating them from the packet when they have not been explicitly configured (length == 0).
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Problem
UpdateDiscoveryValues()inSecureAgentParametersandUTargetunconditionally sets
_contextNameand_contextEngineIdfrom everyincoming SNMPv3 packet's ScopedPdu (lines 540-541, 320-321).
When processing Report PDUs (e.g.
usmStatsNotInTimeWindowsfor timesynchronization), these ScopedPdu fields are typically empty. This
overwrites any user-configured context name, causing subsequent
requests to fail with
snmpUnavailableContexts.Steps to reproduce
SecureAgentParameterswith a non-emptyContextNamea
usmStatsNotInTimeWindowsReportContextNameis now empty afterUpdateDiscoveryValuessnmpUnavailableContextsFix
Only update
_contextNameand_contextEngineIdfrom the packet whenthey have not been explicitly set by the user (i.e.
Length == 0).This is consistent with RFC 3414 (USM for SNMPv3) Section 3.2 and
RFC 3412 Section 7.2: the contextName is a locally-administered value
identifying the MIB view. Report PDUs are administrative engine-sync
responses and should not override the manager's context configuration.