AuthzInitializeContextFromSid function (authz.h)

The AuthzInitializeContextFromSid function creates a user-mode client context from a user security identifier (SID). Domain SIDs retrieve token group attributes from the Active Directory.

Note  If possible, call the AuthzInitializeContextFromToken function instead of AuthzInitializeContextFromSid. For more information, see Remarks.



AUTHZAPI BOOL AuthzInitializeContextFromSid(
  [in]           DWORD                         Flags,
  [in]           PSID                          UserSid,
  [in, optional] AUTHZ_RESOURCE_MANAGER_HANDLE hAuthzResourceManager,
  [in]           PLARGE_INTEGER                pExpirationTime,
  [in]           LUID                          Identifier,
  [in, optional] PVOID                         DynamicGroupArgs,
  [out]          PAUTHZ_CLIENT_CONTEXT_HANDLE  phAuthzClientContext


[in] Flags

The following flags are defined.

Starting with Windows 8 and Windows Server 2012, when you call this function on a remote context handle, the upper 16 bits must be zero.

Value Meaning
0 (0x0)
Default value.

AuthzInitializeContextFromSid attempts to retrieve the user's token group information by performing an S4U logon.

If S4U logon is not supported by the user's domain or the calling computer, AuthzInitializeContextFromSid queries the user's account object for group information. When an account is queried directly, some groups that represent logon characteristics, such as Network, Interactive, Anonymous, Network Service, or Local Service, are omitted. Applications can explicitly add such group SIDs by implementing the AuthzComputeGroupsCallback function or calling the AuthzAddSidsToContext function.

2 (0x2)
Causes AuthzInitializeContextFromSid to skip all group evaluations. When this flag is used, the context returned contains only the SID specified by the UserSid parameter. The specified SID can be an arbitrary or application-specific SID. Other SIDs can be added to this context by implementing the AuthzComputeGroupsCallback function or by calling the AuthzAddSidsToContext function.
4 (0x4)
Causes AuthzInitializeContextFromSid to fail if Windows Services For User is not available to retrieve token group information.

Windows XP:  This flag is not supported.

8 (0x8)
Causes AuthzInitializeContextFromSid to retrieve privileges for the new context. If this function performs an S4U logon, it retrieves privileges from the token. Otherwise, the function retrieves privileges from all SIDs in the context.

[in] UserSid

The SID of the user for whom a client context will be created. This must be a valid user or computer account unless the AUTHZ_SKIP_TOKEN_GROUPS flag is used.

[in, optional] hAuthzResourceManager

A handle to the resource manager creating this client context. This handle is stored in the client context structure.

Starting with Windows 8 and Windows Server 2012, the resource manager can be local or remote and is obtained by calling the AuthzInitializeRemoteResourceManager function.

[in] pExpirationTime

Expiration date and time of the token. If no value is passed, the token never expires. Expiration time is not currently enforced.

[in] Identifier

Specific identifier of the resource manager. This parameter is not currently used.

[in, optional] DynamicGroupArgs

A pointer to parameters to be passed to the callback function that computes dynamic groups. This parameter can be NULL if no dynamic parameters are passed to the callback function.

Starting with Windows 8 and Windows Server 2012, this parameter must be NULL if the resource manager is remote. Otherwise, ERROR_NOT_SUPPORTED will be set.

[out] phAuthzClientContext

A pointer to the handle to the client context that the AuthzInitializeContextFromSid function creates. When you have finished using the handle, free it by calling the AuthzFreeContext function.

Return value

If the function succeeds, the function returns nonzero.

If the function fails, it returns zero. To get extended error information, call GetLastError.


If possible, call the AuthzInitializeContextFromToken function instead of AuthzInitializeContextFromSid. AuthzInitializeContextFromSid attempts to retrieve the information available in a logon token had the client actually logged on. An actual logon token provides more information, such as logon type and logon properties, and reflects the behavior of the authentication package used for the logon. The client context created by AuthzInitializeContextFromToken uses a logon token, and the resulting client context is more complete and accurate than a client context created by AuthzInitializeContextFromSid.

This function resolves valid user SIDs only.

Windows XP:  This function resolves group memberships for valid user and group SIDs (unless the AUTHZ_SKIP_TOKEN_GROUPS flag is used). Support for resolving memberships of group SIDs may be altered or unavailable in subsequent versions.

This function calls the AuthzComputeGroupsCallback callback function to add SIDs to the newly created context.

Important  Applications should not assume that the calling context has permission to use this function. The AuthzInitializeContextFromSid function reads the tokenGroupsGlobalAndUniversal attribute of the SID specified in the call to determine the current user's group memberships. If the user's object is in Active Directory, the calling context must have read access to the tokenGroupsGlobalAndUniversal attribute on the user object. When a new domain is created, the default access compatibility selection is Permissions compatible with Windows 2000 and Windows Server 2003 operating systems. When this option is set, the Pre-Windows 2000 Compatible Access group includes only the Authenticated Users built-in security identifiers. Therefore, applications may not have access to the tokenGroupsGlobalAndUniversal attribute; in this case, the AuthzInitializeContextFromSid function fails with ACCESS_DENIED. Applications that use this function should correctly handle this error and provide supporting documentation. To simplify granting accounts permission to query a user's group information, add accounts that need the ability to look up group information to the Windows Authorization Access Group.


Minimum supported client Windows XP [desktop apps only]
Minimum supported server Windows Server 2003 [desktop apps only]
Target Platform Windows
Header authz.h
Library Authz.lib
DLL Authz.dll
Redistributable Windows Server 2003 Administration Tools Pack on Windows XP

See also

Allowing Anonymous Access


Basic Access Control Functions