COM settings in OPC Classic client components

This article describes the internal effects of the UseCustomSecurity, TurnOffCallSecurity, TurnOffActivationSecurity and EnsureDataIntegrity settings.

Note: For QuickOPC versions up to 2021.3, the information in this article only applies to NativeClient implementation. In QuickOPC versions up to 2021.3, the NetApiClient implementation uses settings, and they cannot be changed by the parameters described here. In QuickOPC versions 2022.1 and later, the behavior of NativeClient and NetApiClient implementation is mostly aligned; we provide a note here where they differ.

COM and proxy initialization:

• Without UseCustomSecurity: CoInitializeSecurity is not called, CoSetProxyBlanket is not called
• With UseCustomSecurity (the default): CoInitializeSecurity is called, CoSetProxyBlanket is called

CoInitializeSecurity parameters:

• Without TurnOffCallSecurity (the default): dwAuthnLevel = Common authentication level (see below); 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)

Common authentication level: In QuickOPC versions up to 2021.3: Always RPC_C_AUTHN_LEVEL_CONNECT (2). In QuickOPC versions 2022.1 and later:

• 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).