COM settings in OPC Classic client components: Difference between revisions

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== CoInitializeSecurity parameters ==
== CoInitializeSecurity parameters ==
In many cases, the COM security will be initialized before we get a chance to call CoInitializeSecurity. In such cases, the call to CoInitializeSecurity will fail silently.


'''pSecDesc = NULL.'''
'''pSecDesc = NULL.'''

Revision as of 21:27, 27 January 2022

This article describes the internal effects of the various COM security settings. For easier orientation, the behavior with the default settings is in bold.

QuickOPC version 2022.1 and later

Parameters from EasyXXClient.SharedParameters.EngineParameters.ComSecurityParameters are used for COM security initialization. Parameters from EasyXXClient.SharedParameters.MachineParameters.ComInstantiationParameters are used for operations on OPCEnum. Parameters from EasyXXClient.SharedParameters.ClientParameters.ComInstantiationParameters are used for operations on target OPC servers.

COM and proxy initialization

  • Without UseCustomSecurity: CoInitializeSecurity is not called. IClientSecurity::SetBlanket (or CoSetProxyBlanket) is not called.
  • With UseCustomSecurity (the default): CoInitializeSecurity is called. IClientSecurity::SetBlanket (or CoSetProxyBlanket) is called (only in NativeClient).

CoInitializeSecurity parameters

In many cases, the COM security will be initialized before we get a chance to call CoInitializeSecurity. In such cases, the call to CoInitializeSecurity will fail silently.

pSecDesc = NULL.

  • Without AllowImpersonateClient (the default): dwImpLevel = RPC_C_IMP_LEVEL_IDENTIFY (2).
  • With AllowImpersonateClient: dwImpLevel = RPC_C_IMP_LEVEL_IMPERSONATE (3).
  • Without TurnOffCallSecurity (the default): dwAuthnLevel = common authentication level (see below).
  • With TurnOffCallSecurity: dwAuthnLevel = RPC_C_AUTHN_LEVEL_NONE (1).[1]

AccessFromThreadToken is ignored.

IClientSecurity::SetBlanket (or CoSetProxyBlanket) parameters

dwAuthnLevel and dwImpLevel are the same as those used with CoInitializeSecurity.

COAUTHINFO* pAuthInfo in COSERVERINFO* passed to CoCreateInstanceEx (when machine name is not empty)

  • Without OverrideDefaultSecurity: NULL.
  • With OverrideDefaultSecurity (the default):
    • Without TurnOffActivationSecurity (the default): dwAuthnSvc = RPC_C_AUTHN_WINNT; dwAuthzSvc = RPC_C_AUTHZ_NONE; pwszServerPrincName = NULL; dwAuthnLevel = common authentication level (see below); dwImpersonationLevel = RPC_C_IMP_LEVEL_IMPERSONATE; pAuthIdentityData = NULL; dwCapabilities = EOAC_NONE.
    • With TurnOffActivationSecurity: dwAuthnSvc = RPC_C_AUTHN_NONE; dwAuthzSvc = RPC_C_AUTHZ_NONE; pwszServerPrincName = NULL; dwAuthnLevel = RPC_C_AUTHN_LEVEL_NONE; dwImpersonationLevel = RPC_C_IMP_LEVEL_IMPERSONATE; pAuthIdentityData = NULL; dwCapabilities = EOAC_NONE.[2]

Common authentication level

  • Without EnsureDataIntegrity (the default): RPC_C_AUTHN_LEVEL_CONNECT (2).
  • With EnsureDataIntegrity: RPC_C_AUTHN_LEVEL_PKT_INTEGRITY (5).[3]

QuickOPC versions up to 2021.3

The information only applies to NativeClient implementation. The NetApiClient implementation uses different settings, and they cannot be changed by the parameters described here.

For operations on OPCEnum, parameters from EasyXXClient.SharedParameters.MachineParameters are used. For operations on target OPC servers, parameters from EasyXXClient.SharedParameters.ClientParameters are used.

COM and proxy initialization

CoInitializeSecurity is not called.

  • Without UseCustomSecurity: IClientSecurity::SetBlanket (or CoSetProxyBlanket) is not called.
  • With UseCustomSecurity (the default): IClientSecurity::SetBlanket (or CoSetProxyBlanket) is called.

IClientSecurity::SetBlanket (or CoSetProxyBlanket) parameters

  • Without TurnOffCallSecurity (the default): dwAuthnLevel = Always RPC_C_AUTHN_LEVEL_CONNECT (2); dwImpLevel = RPC_C_IMP_LEVEL_IMPERSONATE (3).
  • With TurnOffCallSecurity: dwAuthnLevel = RPC_C_AUTHN_LEVEL_NONE (1); dwImpLevel = RPC_C_IMP_LEVEL_IMPERSONATE (3).[1]

COAUTHINFO* pAuthInfo in COSERVERINFO* passed to CoCreateInstanceEx (when machine name is not empty)

  • Without TurnOffActivationSecurity (the default): NULL.
  • With TurnOffActivationSecurity: dwAuthnSvc = RPC_C_AUTHN_NONE; dwAuthzSvc = RPC_C_AUTHZ_NONE; pwszServerPrincName = NULL; dwAuthnLevel = RPC_C_AUTHN_LEVEL_NONE; dwImpersonationLevel = RPC_C_IMP_LEVEL_IMPERSONATE; pAuthIdentityData = NULL; dwCapabilities = EOAC_NONE.[2].


  1. ↑ 1.0 1.1 See Turning Off Call Security. For this to work, the server must also specify None for its authentication level.
  2. ↑ 2.0 2.1 See Turning Off Activation Security. For this to work, the server must specify Everyone for Default Launch Permissions.
  3. ↑ For KB5004442—Manage changes for Windows DCOM Server Security Feature Bypass (CVE-2021-26414).
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