AcquireCredentialsHandleA function (sspi.h)

Article
02/09/2023

The AcquireCredentialsHandle (CredSSP) function acquires a handle to preexisting credentials of a security principal. This handle is required by the InitializeSecurityContext (CredSSP) and AcceptSecurityContext (CredSSP) functions. These can be either preexisting credentials, which are established through a system logon that is not described here, or the caller can provide alternative credentials.

Note This is not a "log on to the network" and does not imply gathering of credentials.

Syntax

SECURITY_STATUS SEC_ENTRY AcquireCredentialsHandleA(
  [in, optional]  LPSTR          pszPrincipal,
  [in]            LPSTR          pszPackage,
  [in]            unsigned long  fCredentialUse,
  [in, optional]  void           *pvLogonId,
  [in, optional]  void           *pAuthData,
  [in, optional]  SEC_GET_KEY_FN pGetKeyFn,
  [in, optional]  void           *pvGetKeyArgument,
  [out]           PCredHandle    phCredential,
  [out, optional] PTimeStamp     ptsExpiry
);

Parameters

[in, optional] pszPrincipal

A pointer to a null-terminated string that specifies the name of the principal whose credentials the handle will reference.

Note If the process that requests the handle does not have access to the credentials, the function returns an error. A null string indicates that the process requires a handle to the credentials of the user under whose security context it is executing.

[in] pszPackage

A pointer to a null-terminated string that specifies the name of the security package with which these credentials will be used. This is a security package name returned in the Name member of a SecPkgInfo structure returned by the EnumerateSecurityPackages function. After a context is established, QueryContextAttributes (CredSSP) can be called with ulAttribute set to SECPKG_ATTR_PACKAGE_INFO to return information on the security package in use.

[in] fCredentialUse

A flag that indicates how these credentials will be used. This parameter can be one of the following values.

Value	Meaning
SECPKG_CRED_INBOUND 0x1	Validate an incoming server credential. Inbound credentials might be validated by using an authenticating authority when InitializeSecurityContext (CredSSP) or AcceptSecurityContext (CredSSP) is called. If such an authority is not available, the function will fail and return SEC_E_NO_AUTHENTICATING_AUTHORITY. Validation is package specific.
SECPKG_CRED_OUTBOUND 0x2	Allow a local client credential to prepare an outgoing token.

[in, optional] pvLogonId

A pointer to a locally unique identifier (LUID) that identifies the user. This parameter is provided for file-system processes such as network redirectors. This parameter can be NULL.

[in, optional] pAuthData

A pointer to a CREDSSP_CRED structure that specifies authentication data for both Schannel and Negotiate packages.

[in, optional] pGetKeyFn

Reserved. This parameter is not used and should be set to NULL.

[in, optional] pvGetKeyArgument

Reserved. This parameter must be set to NULL.

[out] phCredential

A pointer to the CredHandle structure that will receive the credential handle.

[out, optional] ptsExpiry

A pointer to a TimeStamp structure that receives the time at which the returned credentials expire. The structure value received depends on the security package, which must specify the value in local time.

Return value

If the function succeeds, it returns SEC_E_OK.

If the function fails, it returns one of the following error codes.

Return code	Description
SEC_E_INSUFFICIENT_MEMORY	There is insufficient memory available to complete the requested action.
SEC_E_INTERNAL_ERROR	An error occurred that did not map to an SSPI error code.
SEC_E_NO_CREDENTIALS	No credentials are available in the security package.
SEC_E_NOT_OWNER	The caller of the function does not have the necessary credentials.
SEC_E_SECPKG_NOT_FOUND	The requested security package does not exist.
SEC_E_UNKNOWN_CREDENTIALS	The credentials supplied to the package were not recognized.

Remarks

The AcquireCredentialsHandle (CredSSP) function returns a handle to the credentials of a principal, such as a user or client, as used by a specific security package. The function can return the handle to either preexisting credentials or newly created credentials and return it. This handle can be used in subsequent calls to the AcceptSecurityContext (CredSSP) and InitializeSecurityContext (CredSSP) functions.

In general, AcquireCredentialsHandle (CredSSP) does not provide the credentials of other users logged on to the same computer. However, a caller with SE_TCB_NAME privilege can obtain the credentials of an existing logon session by specifying the logon identifier (LUID) of that session. Typically, this is used by kernel-mode modules that must act on behalf of a logged-on user.

A package might call the function in pGetKeyFn provided by the RPC run-time transport. If the transport does not support the notion of callback to retrieve credentials, this parameter must be NULL.

For kernel mode callers, the following differences must be noted:

The two string parameters must be Unicode strings.
The buffer values must be allocated in process virtual memory, not from the pool.

When you have finished using the returned credentials, free the memory used by the credentials by calling the FreeCredentialsHandle function.

Note

The sspi.h header defines AcquireCredentialsHandle as an alias which automatically selects the ANSI or Unicode version of this function based on the definition of the UNICODE preprocessor constant. Mixing usage of the encoding-neutral alias with code that not encoding-neutral can lead to mismatches that result in compilation or runtime errors. For more information, see Conventions for Function Prototypes.

Requirements

Requirement	Value
Minimum supported client	Windows Vista [desktop apps only]
Minimum supported server	Windows Server 2008 [desktop apps only]
Target Platform	Windows
Header	sspi.h (include Security.h)
Library	Secur32.lib
DLL	Secur32.dll