COM settings in OPC Classic client components

This article describes the internal effects of the various COM security settings.

QuickOPC version 2022.1 and later

Parameters from EasyXXClient.SharedParameters.EngineParameters.ComInstantiationParameters and ComSecurityParameters are used for operations on OPCEnum, and also for operations on target OPC servers.

COM and proxy initialization:

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

CoInitializeSecurity parameters:

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) (see Turning Off Call Security).

AccessFromThreadToken is ignored.

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 TurnOffActivationSecurity (the default): 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.
• With TurnOffActivationSecurity: NULL (see Turning Off Activation Security).

Common authentication level:

• Without EnsureDataIntegrity (the default): RPC_C_AUTHN_LEVEL_CONNECT (2).
• With EnsureDataIntegrity: RPC_C_AUTHN_LEVEL_PKT_INTEGRITY (5). For KB5004442—Manage changes for Windows DCOM Server Security Feature Bypass (CVE-2021-26414).

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: CoSetProxyBlanket is not called.
• With UseCustomSecurity (the default): CoSetProxyBlanket is called.

CoInitializeSecurity parameters:

• Without TurnOffCallSecurity (the default): dwAuthnLevel = Always RPC_C_AUTHN_LEVEL_CONNECT (2); dwImpLevel = RPC_C_IMP_LEVEL_IMPERSONATE (3); pSecDesc = CSecurityDescriptor::InitializeFromThreadToken()>
• With TurnOffCallSecurity: dwAuthnLevel = RPC_C_AUTHN_LEVEL_NONE (1); dwImpLevel = RPC_C_IMP_LEVEL_IMPERSONATE (3); pSecDesc = NULL

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 TurnOffActivationSecurity (the default): 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;
• With TurnOffActivationSecurity: NULL

(see https://docs.microsoft.com/en-us/windows/win32/com/turning-off-activation-security?redirectedfrom=MSDN)