Trusted Execution Environment endpoints

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Methods of KasperskyOS core endpoints

Trusted Execution Environment endpoints

August 2, 2023

ID kernel_methods_tee

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These endpoints are intended for transferring data between a Trusted Execution Environment (TEE) and a Rich Execution Environment (REE), and for obtaining access to the physical memory of the REE from the TEE.

Information about methods of endpoints is provided in the tables below.

Methods of the tee.TEE endpoint (kl.core.TEE interface)

Method	Method purpose and parameters	Potential danger of the method
`Dispatch`	Purpose Sends and receives messages transferred between a TEE and a REE. This method is used in the TEE and in the REE. Parameters [in] `msgIn` – structure containing a request for the TEE (when the method is called in the REE) or a response for the REE (when the method is called in the TEE). [out] `msgOut` – structure containing a response from the TEE (when the method is called in the REE) or a request from the REE (when the method is called in the TEE). [out] `rc` – return code.	Allows a process in a REE to receive a response from a TEE regarding a request from another process in the REE.
`FreeToken`	Purpose Frees the values of unique IDs of messages transferred between a TEE and a REE. (These values must be freed so that they can become available for re-use.) This method is used in REE. Parameters [in] `token` – value of the unique ID of a message. [out] `rc` – return code.	Lets you free the values used by other processes in a REE as unique IDs of messages transferred between a TEE and a REE.

Method

Method purpose and parameters

Potential danger of the method

Dispatch

Purpose

Sends and receives messages transferred between a TEE and a REE.

This method is used in the TEE and in the REE.

Parameters

[in] msgIn – structure containing a request for the TEE (when the method is called in the REE) or a response for the REE (when the method is called in the TEE).
[out] msgOut – structure containing a response from the TEE (when the method is called in the REE) or a request from the REE (when the method is called in the TEE).
[out] rc – return code.

Allows a process in a REE to receive a response from a TEE regarding a request from another process in the REE.

FreeToken

Purpose

Frees the values of unique IDs of messages transferred between a TEE and a REE. (These values must be freed so that they can become available for re-use.)

This method is used in REE.

Parameters

[in] token – value of the unique ID of a message.
[out] rc – return code.

Lets you free the values used by other processes in a REE as unique IDs of messages transferred between a TEE and a REE.

Methods of the tee.TEEVMM endpoint (kl.core.TEEVMM interface)

Method	Method purpose and parameters	Potential danger of the method
`MdlAllocate`	Purpose Creates a blank MDL buffer so that physical memory from an REE can be subsequently added to it. This method is used in TEE. Parameters [in] `size` – size of the MDL buffer in bytes. [in] `prot` – flags defining the access rights to the MDL buffer. [out] `handle` – value whose binary representation consists of multiple fields, including a handle field and a handle permissions mask field. The handle identifies the MDL buffer. [out] `rc` – return code.	Allows the kernel memory to be used up by creating a multitude of objects within it.
`MdlAddFrame`	Purpose Adds a REE physical memory region to the blank MDL buffer created by the `MdlAllocate` method. This method is used in TEE. Parameters [in] `handle` – value whose binary representation consists of multiple fields, including a handle field and a handle permissions mask field. The handle identifies the MDL buffer. [in] `pa` – base address of the physical memory region. [in] `pages` – size of the physical memory region, in memory pages. [out] `rc` – return code.	Allows access to an arbitrary region of the physical memory of a REE from a TEE.

Method

Method purpose and parameters

Potential danger of the method

MdlAllocate

Purpose

Creates a blank MDL buffer so that physical memory from an REE can be subsequently added to it.

This method is used in TEE.

Parameters

[in] size – size of the MDL buffer in bytes.
[in] prot – flags defining the access rights to the MDL buffer.
[out] handle – value whose binary representation consists of multiple fields, including a handle field and a handle permissions mask field. The handle identifies the MDL buffer.
[out] rc – return code.

Allows the kernel memory to be used up by creating a multitude of objects within it.

MdlAddFrame

Purpose

Adds a REE physical memory region to the blank MDL buffer created by the MdlAllocate method.

This method is used in TEE.

Parameters

[in] handle – value whose binary representation consists of multiple fields, including a handle field and a handle permissions mask field. The handle identifies the MDL buffer.
[in] pa – base address of the physical memory region.
[in] pages – size of the physical memory region, in memory pages.
[out] rc – return code.

Allows access to an arbitrary region of the physical memory of a REE from a TEE.

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