SetContextAttributesW function (sspi.h)

Article
02/09/2023

Enables a transport application to set attributes of a security context for a security package. This function is supported only by the Schannel security package.

Syntax

SECURITY_STATUS SEC_ENTRY SetContextAttributesW(
  [in] PCtxtHandle   phContext,
  [in] unsigned long ulAttribute,
  [in] void          *pBuffer,
  [in] unsigned long cbBuffer
);

Parameters

[in] phContext

A handle to the security context to be set.

[in] ulAttribute

The attribute of the context to be set. This parameter can be one of the following values.

Value	Meaning
SECPKG_ATTR_APP_DATA 94	The pBuffer parameter contains a pointer to a SecPkgContext_SessionAppData structure. Sets application data for the session. This attribute is supported only by the Schannel security package.
SECPKG_ATTR_EAP_PRF_INFO 101	The pBuffer parameter contains a pointer to a SecPkgContext_EapPrfInfo structure. Sets the pseudo-random function (PRF) used by the Extensible Authentication Protocol (EAP). This is the value that is returned by a call to the QueryContextAttributes (Schannel) function when SECPKG_ATTR_EAP_KEY_BLOCK is passed as the value of the ulAttribute parameter. This attribute is supported only by the Schannel security package.
SECPKG_ATTR_EARLY_START 105	The pBuffer parameter contains a pointer to a SecPkgContext_EarlyStart structure. Sets the False Start feature. See the Building a faster and more secure web blog post for information on this feature.
SECPKG_ATTR_DTLS_MTU 34	Sets and retrieves the MTU (maximum transmission unit) value for use with DTLS. If DTLS is not enabled in a security context, this attribute is not supported. Valid values are between 200 bytes and 64 kilobytes. The default DTLS MTU value in Schannel is 1096 bytes.
SECPKG_ATTR_KEYING_MATERIAL_INFO 106	The pBuffer parameter contains a pointer to a SecPkgContext_KeyingMaterialInfo structure. The keying material export feature follows the RFC 5705 standard. This attribute is supported only by the Schannel security package in Windows 10 and Windows Server 2016 or later versions.

[in] pBuffer

A pointer to a structure that contains values to set the attributes to. The type of structure pointed to depends on the value specified in the ulAttribute parameter.

[in] cbBuffer

The size, in bytes, of the pBuffer parameter.

Return value

If the function succeeds, the function returns SEC_E_OK.

If the function fails, it returns a nonzero error code. The following error code is one of the possible error codes.

Return code	Description
SEC_E_UNSUPPORTED_FUNCTION	This value is returned by Schannel kernel mode to indicate that this function is not supported.

Remarks

Note

The sspi.h header defines SetContextAttributes 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 XP [desktop apps only]
Minimum supported server	Windows Server 2003 [desktop apps only]
Target Platform	Windows
Header	sspi.h (include Security.h)
Library	Secur32.lib
DLL	Secur32.dll

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