stefanberger / libtpms / #2036

// SPDX-License-Identifier: BSD-2-Clause

//** Introduction

//

// This file contains the entry function ExecuteCommand() which provides the main

// control flow for TPM command execution.

//** Includes

#include "Tpm.h"

#include "Marshal.h"

// TODO_RENAME_INC_FOLDER:platform_interface refers to the TPM_CoreLib platform interface

#include "ExecCommand_fp.h"        // libtpms changed

// Uncomment this next #include if doing static command/response buffer sizing

// #include "CommandResponseSizes_fp.h"

#define TPM_HAVE_TPM2_DECLARATIONS

#include "tpm_library_intern.h"  // libtpms added

//** ExecuteCommand()

//

// The function performs the following steps.

//

//  a)  Parses the command header from input buffer.

//  b)  Calls ParseHandleBuffer() to parse the handle area of the command.

//  c)  Validates that each of the handles references a loaded entity.

//  d)  Calls ParseSessionBuffer () to:

//      1)  unmarshal and parse the session area;

//      2)  check the authorizations; and

//      3)  when necessary, decrypt a parameter.

//  e)  Calls CommandDispatcher() to:

//      1)  unmarshal the command parameters from the command buffer;

//      2)  call the routine that performs the command actions; and

//      3)  marshal the responses into the response buffer.

//  f)  If any error occurs in any of the steps above create the error response

//      and return.

//  g)  Calls BuildResponseSession() to:

//      1)  when necessary, encrypt a parameter

//      2)  build the response authorization sessions

//      3)  update the audit sessions and nonces

//  h)  Calls BuildResponseHeader() to complete the construction of the response.

//

// 'responseSize' is set by the caller to the maximum number of bytes available in

// the output buffer. ExecuteCommand will adjust the value and return the number

// of bytes placed in the buffer.

//

// 'response' is also set by the caller to indicate the buffer into which

//  ExecuteCommand is to place the response.

//

//  'request' and 'response' may point to the same buffer

//

// Note: The failure processing has been moved to the

// platform-specific code. When the TPM code encounters an unrecoverable failure, it

// will call _plat__Fail() and call _plat__InFailureMode() to query failure mode.

    uint32_t        requestSize,   // IN: command buffer size

    unsigned char*  request,       // IN: command buffer

    uint32_t*       responseSize,  // IN/OUT: response buffer size

    unsigned char** response       // IN/OUT: response buffer

)

{

    // Command local variables

    // Response local variables

    /* check for an unreasonably large command size, since it's cast to a signed integer later */

    }

    // This next function call is used in development to size the command and response

    // buffers. The values printed are the sizes of the internal structures and

    // not the sizes of the canonical forms of the command response structures. Also,

    // the sizes do not include the tag, command.code, requestSize, or the authorization

    // fields.

    //CommandResponseSizes();

    // Set flags for NV access state. This should happen before any other

    // operation that may require a NV write. Note, that this needs to be done

    // even when in failure mode. Otherwise, g_updateNV would stay SET while in

    // Failure mode and the NV would be written on each call.

    {

        // no return because failure will happen immediately below. this is

        // treated as fatal because it is a system level failure for there to be

        // no TPM_INIT indication.  Since init is an out-of-band indication from

        // Execute command, we don't return TPM_RC_INITIALIZE which refers to

        // the TPM2_Startup command

    }

    {

        // Do failure mode processing

    }

    // Query platform to get the NV state.  The result state is saved internally

    // and will be reported by NvIsAvailable(). The reference code requires that

    // accessibility of NV does not change during the execution of a command.

    // Specifically, if NV is available when the command execution starts and then

    // is not available later when it is necessary to write to NV, then the TPM

    // will go into failure mode.

    // Due to the limitations of the simulation, TPM clock must be explicitly

    // synchronized with the system clock whenever a command is received.

    // This function call is not necessary in a hardware TPM. However, taking

    // a snapshot of the hardware timer at the beginning of the command allows

    // the time value to be consistent for the duration of the command execution.

    // Any command through this function will unceremoniously end the

    // _TPM_Hash_Data/_TPM_Hash_End sequence.

    // Get command buffer size and command buffer.

    // Parse command header: tag, commandSize and command.code.

    // First parse the tag. The unmarshaling routine will validate

    // that it is either TPM_ST_SESSIONS or TPM_ST_NO_SESSIONS.

        &command.tag, &command.parameterBuffer, &command.parameterSize);

    // Unmarshal the commandSize indicator.

        &commandSize, &command.parameterBuffer, &command.parameterSize);

    // On a TPM that receives bytes on a port, the number of bytes that were

    // received on that port is requestSize it must be identical to commandSize.

    // In addition, commandSize must not be larger than MAX_COMMAND_SIZE allowed

    // by the implementation. The check against MAX_COMMAND_SIZE may be redundant

    // as the input processing (the function that receives the command bytes and

    // places them in the input buffer) would likely have the input truncated when

    // it reaches MAX_COMMAND_SIZE, and requestSize would not equal commandSize.

    {

    }

    // Unmarshal the command code.

        &command.code, &command.parameterBuffer, &command.parameterSize);

    // Check to see if the command is implemented.

    {

    }

#if CC_ReadOnlyControl

    // Check if the TPM is operating in Read-Only mode. If so, reject commands

    // that are disallowed in this mode before performing any further auth checks.

    // The execution of some commands may still be disallowed under certain conditions,

    // but those will be evaluated in the corresponding command implementation.

    if(gc.readOnly && IsDisallowedInReadOnlyMode(command.index))

    {

        result = TPM_RC_READ_ONLY;

        goto Cleanup;

    }

#endif

#if FIELD_UPGRADE_IMPLEMENTED == YES

    // If the TPM is in FUM, then the only allowed command is

    // TPM_CC_FieldUpgradeData.

    if(IsFieldUgradeMode() && (command.code != TPM_CC_FieldUpgradeData))

    {

        result = TPM_RC_UPGRADE;

        goto Cleanup;

    }

    else

#endif

        // Excepting FUM, the TPM only accepts TPM2_Startup() after

        // _TPM_Init. After getting a TPM2_Startup(), TPM2_Startup()

        // is no longer allowed.

        {

        }

    // Start regular command process.

    // Parse Handle buffer.

    // All handles in the handle area are required to reference TPM-resident

    // entities.

    // Authorization session handling for the command.

    {

        // Find out session buffer size.

                                  &command.parameterBuffer,

                                  &command.parameterSize);

        // Perform sanity check on the unmarshaled value. If it is smaller than

        // the smallest possible session or larger than the remaining size of

        // the command, then it is an error. NOTE: This check could pass but the

        // session size could still be wrong. That will be determined after the

        // sessions are unmarshaled.

        {

        }

        // The actions of ParseSessionBuffer() are described in the introduction.

        // As the sessions are parsed command.parameterBuffer is advanced so, on a

        // successful return, command.parameterBuffer should be pointing at the

        // first byte of the parameters.

    }

    else

    {

        // The command has no authorization sessions.

        // If the command requires authorizations, then CheckAuthNoSession() will

        // return an error.

    }

    // Set up the response buffer pointers. CommandDispatch will marshal the

    // response parameters starting at the address in command.responseBuffer.

    //*response = MemoryGetResponseBuffer(command.index);

    // leave space for the command header

    // leave space for the parameter size field if needed

    // CommandDispatcher returns a response handle buffer and a response parameter

    // buffer if it succeeds. It will also set the parameterSize field in the

    // buffer if the tag is TPM_RC_SESSIONS.

    // Build the session area at the end of the parameter area.

    {

        goto Cleanup;

    }

    {

        {

#if USE_DA_USED

#else

            gp.orderlyState = SU_NONE_VALUE;

#endif

        }

        // This implementation loads an "evict" object to a transient object slot in

        // RAM whenever an "evict" object handle is used in a command so that the

        // access to any object is the same. These temporary objects need to be

        // cleared from RAM whether the command succeeds or fails.

        // The parameters and sessions have been marshaled. Now tack on the header and

        // set the sizes.  This sets command.parameterSize to the size of the entire

        // response.

        // Try to commit all the writes to NV if any NV write happened during this

        // command execution. This check should be made for both succeeded and failed

        // commands, because a failed one may trigger a NV write in DA logic as well.

        // This is the only place in the command execution path that may call the NV

        // commit. If the NV commit fails, the TPM should be put in failure mode.

        // Don't write in failure mode because we can't trust what we are

        // writing.

        {

            {

            }

            {

            }

        }

        // Clear unused bits in response buffer.

        // as a final act, and not before, update the response size.

    }

    {

        // something in the command triggered failure mode - handle command as a failure instead

    }

}