path: root/src/VBox/Devices/Security/DrvTpmEmu.cpp

/* $Id: DrvTpmEmu.cpp $ */
/** @file
 * TPM emulator using a TCP/socket interface to talk to swtpm (https://github.com/stefanberger/swtpm).
 */

/*
 * Copyright (C) 2021-2023 Oracle and/or its affiliates.
 *
 * This file is part of VirtualBox base platform packages, as
 * available from https://www.virtualbox.org.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation, in version 3 of the
 * License.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see <https://www.gnu.org/licenses>.
 *
 * SPDX-License-Identifier: GPL-3.0-only
 */


/*********************************************************************************************************************************
*   Header Files                                                                                                                 *
*********************************************************************************************************************************/
#define LOG_GROUP LOG_GROUP_DRV_TPM_EMU
#include <VBox/vmm/pdmdrv.h>
#include <VBox/vmm/pdmtpmifs.h>
#include <iprt/assert.h>
#include <iprt/file.h>
#include <iprt/stream.h>
#include <iprt/alloc.h>
#include <iprt/pipe.h>
#include <iprt/poll.h>
#include <iprt/string.h>
#include <iprt/semaphore.h>
#include <iprt/socket.h>
#include <iprt/tcp.h>
#include <iprt/uuid.h>
#include <iprt/json.h>

#include <iprt/formats/tpm.h>

#include "VBoxDD.h"


/*********************************************************************************************************************************
*   Defined Constants And Macros                                                                                                 *
*********************************************************************************************************************************/


/*********************************************************************************************************************************
*   Structures and Typedefs                                                                                                      *
*********************************************************************************************************************************/

/** @name Protocol definitions to communicate with swtpm, taken from https://github.com/stefanberger/swtpm/blob/master/include/swtpm/tpm_ioctl.h
 * @{ */
/**
 * Commands going over the control channel (big endian).
 */
typedef enum SWTPMCMD
{
    /** Not used. */
    SWTPMCMD_INVALID = 0,
    SWTPMCMD_GET_CAPABILITY,
    SWTPMCMD_INIT,
    SWTPMCMD_SHUTDOWN,
    SWTPMCMD_GET_TPMESTABLISHED,
    SWTPMCMD_SET_LOCALITY,
    SWTPMCMD_HASH_START,
    SWTPMCMD_HASH_DATA,
    SWTPMCMD_HASH_END,
    SWTPMCMD_CANCEL_TPM_CMD,
    SWTPMCMD_STORE_VOLATILE,
    SWTPMCMD_RESET_TPMESTABLISHED,
    SWTPMCMD_GET_STATEBLOB,
    SWTPMCMD_SET_STATEBLOB,
    SWTPMCMD_STOP,
    SWTPMCMD_GET_CONFIG,
    SWTPMCMD_SET_DATAFD,
    SWTPMCMD_SET_BUFFERSIZE,
    SWTPMCMD_GET_INFO,
    /** Blow the enum up to a 32bit size. */
    SWTPMCMD_32BIT_HACK = 0x7fffffff
} SWTPMCMD;


/**
 * Command/Response header.
 */
typedef union SWTPMHDR
{
    /** The command opcode. */
    SWTPMCMD                    enmCmd;
    /** The response result. */
    uint32_t                    u32Resp;
} SWTPMHDR;
AssertCompileSize(SWTPMHDR, sizeof(uint32_t));
/** Pointer to a command/response header. */
typedef SWTPMHDR *PSWTPMHDR;
/** Pointer to a const command/response header. */
typedef const SWTPMHDR *PCSWTPMHDR;


/**
 * Additional command data for SWTPMCMD_INIT.
 */
typedef struct SWTPMCMDTPMINIT
{
    /** Additional flags */
    uint32_t                    u32Flags;
} SWTPMCMDTPMINIT;
/** Pointer to a command data struct for SWTPMCMD_INIT. */
typedef SWTPMCMDTPMINIT *PSWTPMCMDTPMINIT;
/** Pointer to a const command data struct for SWTPMCMD_INIT. */
typedef const SWTPMCMDTPMINIT *PCSWTPMCMDTPMINIT;


/** @name Capabilities as returned by SWTPMCMD_INIT.
 * @{ */
#define SWTPMCMD_INIT_F_DELETE_VOLATILE RT_BIT_32(0);
/** @} */


/**
 * Response data for a SWTPMCMD_GET_CAPABILITY command.
 */
typedef struct SWTPMRESPGETCAPABILITY
{
    /** The capabilities supported. */
    uint32_t                    u32Caps;
} SWTPMRESPGETCAPABILITY;
/** Pointer to a response data struct for SWTPMCMD_GET_CAPABILITY. */
typedef SWTPMRESPGETCAPABILITY *PSWTPMRESPGETCAPABILITY;
/** Pointer to a const response data struct for SWTPMCMD_GET_CAPABILITY. */
typedef const SWTPMRESPGETCAPABILITY *PCSWTPMRESPGETCAPABILITY;


/** @name Capabilities as returned by SWTPMCMD_GET_CAPABILITY.
 * @{ */
#define SWTPM_CAP_INIT                  RT_BIT_32(0)
#define SWTPM_CAP_SHUTDOWN              RT_BIT_32(1)
#define SWTPM_CAP_GET_TPMESTABLISHED    RT_BIT_32(2)
#define SWTPM_CAP_SET_LOCALITY          RT_BIT_32(3)
#define SWTPM_CAP_HASHING               RT_BIT_32(4)
#define SWTPM_CAP_CANCEL_TPM_CMD        RT_BIT_32(5)
#define SWTPM_CAP_STORE_VOLATILE        RT_BIT_32(6)
#define SWTPM_CAP_RESET_TPMESTABLISHED  RT_BIT_32(7)
#define SWTPM_CAP_GET_STATEBLOB         RT_BIT_32(8)
#define SWTPM_CAP_SET_STATEBLOB         RT_BIT_32(9)
#define SWTPM_CAP_STOP                  RT_BIT_32(10)
#define SWTPM_CAP_GET_CONFIG            RT_BIT_32(11)
#define SWTPM_CAP_SET_DATAFD            RT_BIT_32(12)
#define SWTPM_CAP_SET_BUFFERSIZE        RT_BIT_32(13)
#define SWTPM_CAP_GET_INFO              RT_BIT_32(14)
#define SWTPM_CAP_SEND_COMMAND_HEADER   RT_BIT_32(15)
/** @} */


/**
 * Additional command data for SWTPMCMD_SET_LOCALITY.
 */
typedef struct SWTPMCMDSETLOCALITY
{
    /** The locality to set */
    uint8_t                     bLoc;
} SWTPMCMDSETLOCALITY;
/** Pointer to a command data struct for SWTPMCMD_SET_LOCALITY. */
typedef SWTPMCMDSETLOCALITY *PSWTPMCMDSETLOCALITY;
/** Pointer to a const command data struct for SWTPMCMD_SET_LOCALITY. */
typedef const SWTPMCMDSETLOCALITY *PCSWTPMCMDSETLOCALITY;


/**
 * Additional command data for SWTPMCMD_GET_CONFIG.
 */
typedef struct SWTPMCMDGETCONFIG
{
    /** Combination of SWTPM_GET_CONFIG_F_XXX. */
    uint64_t                    u64Flags;
    /** The offset where to start reading from. */
    uint32_t                    u32Offset;
    /** Some padding to a 8 byte alignment. */
    uint32_t                    u32Padding;
} SWTPMCMDGETCONFIG;
/** Pointer to a response data struct for SWTPMCMD_GET_CONFIG. */
typedef SWTPMCMDGETCONFIG *PSWTPMCMDGETCONFIG;
/** Pointer to a const response data struct for SWTPMCMD_GET_CONFIG. */
typedef const SWTPMCMDGETCONFIG *PCSWTPMCMDGETCONFIG;


/** @name Flags for SWTPMCMDGETCONFIG::u64Flags.
 * @{ */
/** Return the TPM specification JSON object. */
#define SWTPM_GET_CONFIG_F_TPM_SPECIFICATION    RT_BIT_64(0)
/** Return the TPM attributes JSON object. */
#define SWTPM_GET_CONFIG_F_TPM_ATTRIBUTES       RT_BIT_64(1)
/** @} */


/**
 * Response data for a SWTPMCMD_GET_CONFIG command.
 */
typedef struct SWTPMRESPGETCONFIG
{
    /** Total size of the object in bytes. */
    uint32_t                    cbTotal;
    /** Size of the chunk returned in this response. */
    uint32_t                    cbThis;
} SWTPMRESPGETCONFIG;
/** Pointer to a response data struct for SWTPMCMD_GET_CONFIG. */
typedef SWTPMRESPGETCONFIG *PSWTPMRESPGETCONFIG;
/** Pointer to a const response data struct for SWTPMCMD_GET_CONFIG. */
typedef const SWTPMRESPGETCONFIG *PCSWTPMRESPGETCONFIG;


/**
 * Response data for a SWTPMCMD_GET_TPMESTABLISHED command.
 */
typedef struct SWTPMRESPGETTPMEST
{
    /** Flag whether the TPM established bit is set for the TPM. */
    uint8_t                     fEst;
} SWTPMRESPGETTPMEST;
/** Pointer to a response data struct for SWTPMCMD_GET_TPMESTABLISHED. */
typedef SWTPMRESPGETTPMEST *PSWTPMRESPGETTPMEST;
/** Pointer to a const response data struct for SWTPMCMD_GET_TPMESTABLISHED. */
typedef const SWTPMRESPGETTPMEST *PCSWTPMRESPGETTPMEST;


/**
 * Additional command data for SWTPMCMD_RESET_TPMESTABLISHED.
 */
typedef struct SWTPMCMDRSTEST
{
    /** The locality resetting trying to reset the established bit. */
    uint8_t                     bLoc;
} SWTPMCMDRSTEST;
/** Pointer to a response data struct for SWTPMCMD_GET_TPMESTABLISHED. */
typedef SWTPMCMDRSTEST *PSWTPMCMDRSTEST;
/** Pointer to a const response data struct for SWTPMCMD_GET_TPMESTABLISHED. */
typedef const SWTPMCMDRSTEST *PCSWTPMCMDRSTEST;


/**
 * Additional command data for SWTPMCMD_SET_BUFFERSIZE.
 */
typedef struct SWTPMCMDSETBUFSZ
{
    /** The buffer size to set, 0 to query for the currently used buffer size. */
    uint32_t                    cbBuffer;
} SWTPMCMDSETBUFSZ;
/** Pointer to a command data struct for SWTPMCMD_SET_BUFFERSIZE. */
typedef SWTPMCMDSETBUFSZ *PSWTPMCMDSETBUFSZ;
/** Pointer to a const command data struct for SWTPMCMD_SET_BUFFERSIZE. */
typedef const SWTPMCMDSETBUFSZ *PCSWTPMCMDSETBUFSZ;


/**
 * Response data for a SWTPMCMD_SET_BUFFERSIZE command.
 */
typedef struct SWTPMRESPSETBUFSZ
{
    /** Buffer size in use. */
    uint32_t                    cbBuffer;
    /** Minimum supported buffer size. */
    uint32_t                    cbBufferMin;
    /** Maximum supported buffer size. */
    uint32_t                    cbBufferMax;
} SWTPMRESPSETBUFSZ;
/** Pointer to a response data struct for SWTPMCMD_SET_BUFFERSIZE. */
typedef SWTPMRESPSETBUFSZ *PSWTPMRESPSETBUFSZ;
/** Pointer to a const response data struct for SWTPMCMD_SET_BUFFERSIZE. */
typedef const SWTPMRESPSETBUFSZ *PCSWTPMRESPSETBUFSZ;


/**
 * TPM emulator driver instance data.
 *
 * @implements PDMITPMCONNECTOR
 */
typedef struct DRVTPMEMU
{
    /** The stream interface. */
    PDMITPMCONNECTOR    ITpmConnector;
    /** Pointer to the driver instance. */
    PPDMDRVINS          pDrvIns;

    /** Socket handle for the control connection. */
    RTSOCKET            hSockCtrl;
    /** Socket handle for the data connection. */
    RTSOCKET            hSockData;

    /** Currently set locality. */
    uint8_t             bLoc;

    /** TPM version offered by the emulator. */
    TPMVERSION          enmTpmVers;
    /** Capabilities offered by the TPM emulator. */
    uint32_t            fCaps;
    /** Buffer size for the emulated TPM. */
    uint32_t            cbBuffer;
} DRVTPMEMU;
/** Pointer to the TPM emulator instance data. */
typedef DRVTPMEMU *PDRVTPMEMU;

/** The special no current locality selected value. */
#define TPM_NO_LOCALITY_SELECTED    0xff


/*********************************************************************************************************************************
*   Internal Functions                                                                                                           *
*********************************************************************************************************************************/

/**
 * Executes the given command over the control connection to the TPM emulator.
 *
 * @returns VBox status code.
 * @param   pThis               Pointer to the TPM emulator driver instance data.
 * @param   enmCmd              The command to execute.
 * @param   pvCmd               Additional command data to send.
 * @param   cbCmd               Size of the additional command data in bytes.
 * @param   pu32Resp            Where to store the response code from the reply.
 * @param   pvResp              Where to store additional resposne data.
 * @param   cbResp              Size of the Response data in bytes (excluding the response status code which is implicit).
 * @param   cMillies            Number of milliseconds to wait before aborting the command with a timeout error.
 *
 * @note This method can return success even though the request at such failed, check the content of pu32Resp!
 */
static int drvTpmEmuExecCtrlCmdEx(PDRVTPMEMU pThis, SWTPMCMD enmCmd, const void *pvCmd, size_t cbCmd, uint32_t *pu32Resp,
                                  void *pvResp, size_t cbResp, RTMSINTERVAL cMillies)
{
    SWTPMHDR Hdr;
    RTSGBUF SgBuf;
    RTSGSEG aSegs[2];
    uint32_t cSegs = 1;

    Hdr.enmCmd = (SWTPMCMD)RT_H2BE_U32(enmCmd);
    aSegs[0].pvSeg = &Hdr;
    aSegs[0].cbSeg = sizeof(Hdr);
    if (cbCmd)
    {
        cSegs++;
        aSegs[1].pvSeg = (void *)pvCmd;
        aSegs[1].cbSeg = cbCmd;
    }

    RTSgBufInit(&SgBuf, &aSegs[0], cSegs);
    int rc = RTSocketSgWrite(pThis->hSockCtrl, &SgBuf);
    if (RT_SUCCESS(rc))
    {
        rc = RTSocketSelectOne(pThis->hSockCtrl, cMillies);
        if (RT_SUCCESS(rc))
        {
            uint32_t u32Resp = 0;
            rc = RTSocketRead(pThis->hSockCtrl, &u32Resp, sizeof(u32Resp), NULL /*pcbRead*/);
            if (RT_SUCCESS(rc))
            {
                *pu32Resp = RT_BE2H_U32(u32Resp);
                if (*pu32Resp == 0)
                {
                    if (cbResp)
                        rc = RTSocketRead(pThis->hSockCtrl, pvResp, cbResp, NULL /*pcbRead*/);
                }
                else
                    rc = VERR_NET_IO_ERROR;
            }
        }
    }

    return rc;
}


/**
 * Continue receiving a response from a previous call of drvTpmEmuExecCtrlCmdEx() or
 * drvTpmEmuExecCtrlCmdNoPayload().
 *
 * @param   pThis               Pointer to the TPM emulator driver instance data.
 * @param   enmCmd              The command to execute.
 * @param   pvResp              Where to store additional resposne data.
 * @param   cbResp              Size of the additional response data in bytes.
 * @param   cMillies            Number of milliseconds to wait before aborting the receive with a timeout error.
 */
static int drvTpmEmuExecCtrlCmdRespCont(PDRVTPMEMU pThis, void *pvResp, size_t cbResp, RTMSINTERVAL cMillies)
{
    int rc = RTSocketSelectOne(pThis->hSockCtrl, cMillies);
    if (RT_SUCCESS(rc))
        rc = RTSocketRead(pThis->hSockCtrl, pvResp, cbResp, NULL /*pcbRead*/);

    return rc;
}


/**
 * Executes the given command over the control connection to the TPM emulator - variant with no command payload.
 *
 * @returns VBox status code.
 * @retval  VERR_NET_IO_ERROR if the executed command returned an error in the response status field.
 * @param   pThis               Pointer to the TPM emulator driver instance data.
 * @param   enmCmd              The command to execute.
 * @param   pvResp              Where to store additional resposne data.
 * @param   cbResp              Size of the Response data in bytes (excluding the response status code which is implicit).
 * @param   cMillies            Number of milliseconds to wait before aborting the command with a timeout error.
 */
static int drvTpmEmuExecCtrlCmdNoPayload(PDRVTPMEMU pThis, SWTPMCMD enmCmd, void *pvResp, size_t cbResp, RTMSINTERVAL cMillies)
{
    uint32_t u32Resp = 0;
    int rc = drvTpmEmuExecCtrlCmdEx(pThis, enmCmd, NULL /*pvCmd*/, 0 /*cbCmd*/, &u32Resp,
                                    pvResp, cbResp, cMillies);
    if (RT_SUCCESS(rc))
    {
        if (u32Resp != 0)
            rc = VERR_NET_IO_ERROR;
    }

    return rc;
}


/**
 * Executes the given command over the control connection to the TPM emulator - variant with no response payload other than the result.
 *
 * @returns VBox status code.
 * @retval  VERR_NET_IO_ERROR if the executed command returned an error in the response status field.
 * @param   pThis               Pointer to the TPM emulator driver instance data.
 * @param   enmCmd              The command to execute.
 * @param   pvCmd               Additional command data to send.
 * @param   cbCmd               Size of the additional command data in bytes.
 * @param   pu32Resp            Where to store the response code from the reply.
 * @param   cMillies            Number of milliseconds to wait before aborting the command with a timeout error.
 */
static int drvTpmEmuExecCtrlCmdNoResp(PDRVTPMEMU pThis, SWTPMCMD enmCmd, const void *pvCmd, size_t cbCmd, uint32_t *pu32Resp,
                                      RTMSINTERVAL cMillies)
{
    return drvTpmEmuExecCtrlCmdEx(pThis, enmCmd, pvCmd, cbCmd, pu32Resp,
                                  NULL /*pvResp*/, 0 /*cbResp*/, cMillies);
}


/**
 * Executes the given command over the control connection to the TPM emulator - variant with no command and response payload.
 *
 * @returns VBox status code.
 * @retval  VERR_NET_IO_ERROR if the executed command returned an error in the response status field.
 * @param   pThis               Pointer to the TPM emulator driver instance data.
 * @param   enmCmd              The command to execute.
 * @param   cMillies            Number of milliseconds to wait before aborting the command with a timeout error.
 */
static int drvTpmEmuExecCtrlCmdNoPayloadAndResp(PDRVTPMEMU pThis, SWTPMCMD enmCmd, RTMSINTERVAL cMillies)
{
    uint32_t u32Resp = 0;
    int rc = drvTpmEmuExecCtrlCmdEx(pThis, enmCmd, NULL /*pvCmd*/, 0 /*cbCmd*/, &u32Resp,
                                    NULL /*pvResp*/, 0 /*cbResp*/, cMillies);
    if (RT_SUCCESS(rc))
    {
        if (u32Resp != 0)
            rc = VERR_NET_IO_ERROR;
    }

    return rc;
}


/**
 * Queries the version of the TPM offered by the remote emulator.
 *
 * @returns VBox status code.
 * @param   pThis               Pointer to the TPM emulator driver instance data.
 */
static int drvTpmEmuQueryTpmVersion(PDRVTPMEMU pThis)
{
    SWTPMCMDGETCONFIG Cmd;
    SWTPMRESPGETCONFIG Resp;
    uint8_t abData[_4K];
    uint32_t u32Resp = 0;

    RT_ZERO(Cmd); RT_ZERO(Resp);
    Cmd.u64Flags = RT_H2BE_U64(SWTPM_GET_CONFIG_F_TPM_SPECIFICATION);
    Cmd.u32Offset = 0;
    int rc = drvTpmEmuExecCtrlCmdEx(pThis, SWTPMCMD_GET_INFO, &Cmd, sizeof(Cmd), &u32Resp,
                                    &Resp, sizeof(Resp), RT_MS_10SEC);
    if (RT_SUCCESS(rc))
    {
        /*
         * Currently it is not necessary to get the information in chunks, a single
         * transaction is enough. To fend off future versions of swtpm requiring this
         * we return an error here if the total length is not equal to the length of the chunk.
         */
        if (RT_BE2H_U32(Resp.cbTotal) == RT_BE2H_U32(Resp.cbThis))
        {
            /* Fetch the response body. */
            rc = drvTpmEmuExecCtrlCmdRespCont(pThis, &abData[0], RT_BE2H_U32(Resp.cbThis), RT_MS_10SEC);
            if (RT_SUCCESS(rc))
            {
                RTJSONVAL hJsonVal = NIL_RTJSONVAL;
                rc = RTJsonParseFromBuf(&hJsonVal, &abData[0], RT_BE2H_U32(Resp.cbThis), NULL /*pErrInfo*/);
                if (RT_SUCCESS(rc))
                {
                    RTJSONVAL hJsonTpmSpec = NIL_RTJSONVAL;
                    rc = RTJsonValueQueryByName(hJsonVal, "TPMSpecification", &hJsonTpmSpec);
                    if (RT_SUCCESS(rc))
                    {
                        RTJSONVAL hJsonTpmFam = NIL_RTJSONVAL;
                        rc = RTJsonValueQueryByName(hJsonTpmSpec, "family", &hJsonTpmFam);
                        if (RT_SUCCESS(rc))
                        {
                            const char *pszFam = NULL;
                            rc = RTJsonValueQueryString(hJsonTpmFam, &pszFam);
                            if (RT_SUCCESS(rc))
                            {
                                if (!RTStrCmp(pszFam, "1.2"))
                                    pThis->enmTpmVers = TPMVERSION_1_2;
                                else if (!RTStrCmp(pszFam, "2.0"))
                                    pThis->enmTpmVers = TPMVERSION_2_0;
                                else
                                    pThis->enmTpmVers = TPMVERSION_UNKNOWN;
                            }

                            RTJsonValueRelease(hJsonTpmFam);
                        }

                        RTJsonValueRelease(hJsonTpmSpec);
                    }

                    RTJsonValueRelease(hJsonVal);
                }
            }
        }
        else
            rc = VERR_NOT_SUPPORTED;
    }

    return rc;
}


/**
 * Queries the capabilities of the remote TPM emulator and verifies that
 * it offers everything we require for operation.
 *
 * @returns VBox status code.
 * @param   pThis               Pointer to the TPM emulator driver instance data.
 */
static int drvTpmEmuQueryCaps(PDRVTPMEMU pThis)
{
    SWTPMRESPGETCAPABILITY Resp;
    int rc = drvTpmEmuExecCtrlCmdNoPayload(pThis, SWTPMCMD_GET_CAPABILITY, &Resp, sizeof(Resp), RT_MS_10SEC);
    if (RT_SUCCESS(rc))
        pThis->fCaps = RT_BE2H_U32(Resp.u32Caps);

    return rc;
}


/**
 * Queries the maximum supported buffer size by the emulation.
 *
 * @returns VBox status code.
 * @param   pThis               Pointer to the TPM emulator driver instance data.
 * @param   pcbBufferMax        Where to store the maximum supported buffer size on success.
 */
static int drvTpmEmuQueryBufferSzMax(PDRVTPMEMU pThis, uint32_t *pcbBufferMax)
{
    SWTPMCMDSETBUFSZ Cmd;
    SWTPMRESPSETBUFSZ Resp;
    uint32_t u32Resp = 0;

    RT_ZERO(Cmd); RT_ZERO(Resp);
    Cmd.cbBuffer = RT_H2BE_U32(0);
    int rc = drvTpmEmuExecCtrlCmdEx(pThis, SWTPMCMD_SET_BUFFERSIZE, &Cmd, sizeof(Cmd), &u32Resp,
                                    &Resp, sizeof(Resp), RT_MS_10SEC);
    if (RT_SUCCESS(rc))
    {
        if (u32Resp == 0)
            *pcbBufferMax = RT_BE2H_U32(Resp.cbBufferMax);
        else
            rc = VERR_NET_IO_ERROR;
    }

    return rc;
}


/**
 * Queries the maximum supported buffer size by the emulation.
 *
 * @returns VBox status code.
 * @param   pThis               Pointer to the TPM emulator driver instance data.
 * @param   cbBuffer            The buffer size to set.
 */
static int drvTpmEmuSetBufferSz(PDRVTPMEMU pThis, uint32_t cbBuffer)
{
    SWTPMCMDSETBUFSZ Cmd;
    SWTPMRESPSETBUFSZ Resp;
    uint32_t u32Resp = 0;

    RT_ZERO(Cmd); RT_ZERO(Resp);
    Cmd.cbBuffer = RT_H2BE_U32(cbBuffer);
    int rc = drvTpmEmuExecCtrlCmdEx(pThis, SWTPMCMD_SET_BUFFERSIZE, &Cmd, sizeof(Cmd), &u32Resp,
                                    &Resp, sizeof(Resp), RT_MS_10SEC);
    if (   RT_SUCCESS(rc)
        && u32Resp != 0)
        rc = VERR_NET_IO_ERROR;

    return rc;
}


/**
 * Sets the given locality for the emulated TPM.
 *
 * @returns VBox status code.
 * @param   pThis               Pointer to the TPM emulator driver instance data.
 * @param   bLoc                The locality to set.
 */
static int drvTpmEmuSetLocality(PDRVTPMEMU pThis, uint8_t bLoc)
{
    SWTPMCMDSETLOCALITY Cmd;
    uint32_t u32Resp = 0;

    Cmd.bLoc = bLoc;
    int rc = drvTpmEmuExecCtrlCmdNoResp(pThis, SWTPMCMD_SET_LOCALITY, &Cmd, sizeof(Cmd), &u32Resp, RT_MS_10SEC);
    if (   RT_SUCCESS(rc)
        && u32Resp != 0)
        rc = VERR_NET_IO_ERROR;

    if (RT_SUCCESS(rc))
        pThis->bLoc = bLoc;

    return rc;
}


/** @interface_method_impl{PDMITPMCONNECTOR,pfnGetVersion} */
static DECLCALLBACK(TPMVERSION) drvTpmEmuGetVersion(PPDMITPMCONNECTOR pInterface)
{
    PDRVTPMEMU pThis = RT_FROM_MEMBER(pInterface, DRVTPMEMU, ITpmConnector);
    return pThis->enmTpmVers;
}


/** @interface_method_impl{PDMITPMCONNECTOR,pfnGetLocalityMax} */
static DECLCALLBACK(uint32_t) drvTpmEmuGetLocalityMax(PPDMITPMCONNECTOR pInterface)
{
    RT_NOREF(pInterface);
    return 4;
}


/** @interface_method_impl{PDMITPMCONNECTOR,pfnGetBufferSize} */
static DECLCALLBACK(uint32_t) drvTpmEmuGetBufferSize(PPDMITPMCONNECTOR pInterface)
{
    PDRVTPMEMU pThis = RT_FROM_MEMBER(pInterface, DRVTPMEMU, ITpmConnector);
    return pThis->cbBuffer;
}


/** @interface_method_impl{PDMITPMCONNECTOR,pfnGetEstablishedFlag} */
static DECLCALLBACK(bool) drvTpmEmuGetEstablishedFlag(PPDMITPMCONNECTOR pInterface)
{
    PDRVTPMEMU pThis = RT_FROM_MEMBER(pInterface, DRVTPMEMU, ITpmConnector);

    SWTPMRESPGETTPMEST Resp;
    int rc = drvTpmEmuExecCtrlCmdNoPayload(pThis, SWTPMCMD_GET_TPMESTABLISHED, &Resp, sizeof(Resp), RT_MS_10SEC);
    if (RT_SUCCESS(rc)
        && Resp.fEst != 0)
        return true;

    return false;
}


/** @interface_method_impl{PDMITPMCONNECTOR,pfnResetEstablishedFlag} */
static DECLCALLBACK(int) drvTpmEmuResetEstablishedFlag(PPDMITPMCONNECTOR pInterface, uint8_t bLoc)
{
    PDRVTPMEMU pThis = RT_FROM_MEMBER(pInterface, DRVTPMEMU, ITpmConnector);

    SWTPMCMDRSTEST Cmd;
    uint32_t u32Resp = 0;

    Cmd.bLoc = bLoc;
    int rc = drvTpmEmuExecCtrlCmdNoResp(pThis, SWTPMCMD_RESET_TPMESTABLISHED, &Cmd, sizeof(Cmd), &u32Resp, RT_MS_10SEC);
    if (   RT_SUCCESS(rc)
        && u32Resp != 0)
        rc = VERR_NET_IO_ERROR;

    return rc;
}


/** @interface_method_impl{PDMITPMCONNECTOR,pfnCmdExec} */
static DECLCALLBACK(int) drvTpmEmuCmdExec(PPDMITPMCONNECTOR pInterface, uint8_t bLoc, const void *pvCmd, size_t cbCmd, void *pvResp, size_t cbResp)
{
    PDRVTPMEMU pThis = RT_FROM_MEMBER(pInterface, DRVTPMEMU, ITpmConnector);

    int rc = VINF_SUCCESS;
    if (pThis->bLoc != bLoc)
        rc = drvTpmEmuSetLocality(pThis, bLoc);

    if (RT_SUCCESS(rc))
    {
        rc = RTSocketWrite(pThis->hSockData, pvCmd, cbCmd);
        if (RT_SUCCESS(rc))
        {
            rc = RTSocketSelectOne(pThis->hSockData, RT_MS_10SEC);
            if (RT_SUCCESS(rc))
            {
                /* Read the response header in first. */
                TPMRESPHDR RespHdr;
                rc = RTSocketRead(pThis->hSockData, &RespHdr, sizeof(RespHdr), NULL /*pcbRead*/);
                if (RT_SUCCESS(rc))
                {
                    size_t cbHdrResp = RTTpmRespGetSz(&RespHdr);
                    if (cbHdrResp <= cbResp - sizeof(RespHdr))
                    {
                        memcpy(pvResp, &RespHdr, sizeof(RespHdr));

                        if (cbHdrResp > sizeof(RespHdr))
                            rc = RTSocketRead(pThis->hSockData, (uint8_t *)pvResp + sizeof(RespHdr), cbHdrResp - sizeof(RespHdr),
                                              NULL /*pcbRead*/);
                    }
                    else
                        rc = VERR_BUFFER_OVERFLOW;
                }
            }
        }
    }

    return rc;
}


/** @interface_method_impl{PDMITPMCONNECTOR,pfnCmdCancel} */
static DECLCALLBACK(int) drvTpmEmuCmdCancel(PPDMITPMCONNECTOR pInterface)
{
    PDRVTPMEMU pThis = RT_FROM_MEMBER(pInterface, DRVTPMEMU, ITpmConnector);

    return drvTpmEmuExecCtrlCmdNoPayloadAndResp(pThis, SWTPMCMD_CANCEL_TPM_CMD, RT_MS_10SEC);
}


/** @interface_method_impl{PDMIBASE,pfnQueryInterface} */
static DECLCALLBACK(void *) drvTpmEmuQueryInterface(PPDMIBASE pInterface, const char *pszIID)
{
    PPDMDRVINS      pDrvIns = PDMIBASE_2_PDMDRV(pInterface);
    PDRVTPMEMU      pThis   = PDMINS_2_DATA(pDrvIns, PDRVTPMEMU);
    PDMIBASE_RETURN_INTERFACE(pszIID, PDMIBASE, &pDrvIns->IBase);
    PDMIBASE_RETURN_INTERFACE(pszIID, PDMITPMCONNECTOR, &pThis->ITpmConnector);
    return NULL;
}


/* -=-=-=-=- PDMDRVREG -=-=-=-=- */

/**
 * @interface_method_impl{PDMDRVREG,pfnPowerOn}
 */
static DECLCALLBACK(void) drvTpmEmuPowerOn(PPDMDRVINS pDrvIns)
{
    PDMDRV_CHECK_VERSIONS_RETURN_VOID(pDrvIns);
    PDRVTPMEMU pThis = PDMINS_2_DATA(pDrvIns, PDRVTPMEMU);

    SWTPMCMDTPMINIT Cmd;
    uint32_t u32Resp = 0;

    RT_ZERO(Cmd);
    Cmd.u32Flags = 0;
    int rc = drvTpmEmuExecCtrlCmdEx(pThis, SWTPMCMD_INIT, &Cmd, sizeof(Cmd), &u32Resp,
                                    NULL, 0, RT_MS_10SEC);
    if (RT_FAILURE(rc))
        PDMDrvHlpVMSetError(pDrvIns, rc, RT_SRC_POS, "Failed to startup the TPM with %Rrc", rc);
}


/**
 * @interface_method_impl{PDMDRVREG,pfnPowerOff}
 */
static DECLCALLBACK(void) drvTpmEmuPowerOff(PPDMDRVINS pDrvIns)
{
    PDMDRV_CHECK_VERSIONS_RETURN_VOID(pDrvIns);
    PDRVTPMEMU pThis = PDMINS_2_DATA(pDrvIns, PDRVTPMEMU);

    int rc = drvTpmEmuExecCtrlCmdNoPayload(pThis, SWTPMCMD_SHUTDOWN, NULL, 0, RT_MS_10SEC);
    if (RT_FAILURE(rc))
        PDMDrvHlpVMSetError(pDrvIns, rc, RT_SRC_POS, "Failed to shutdown the TPM with %Rrc", rc);
}


/** @copydoc FNPDMDRVDESTRUCT */
static DECLCALLBACK(void) drvTpmEmuDestruct(PPDMDRVINS pDrvIns)
{
    PDRVTPMEMU pThis = PDMINS_2_DATA(pDrvIns, PDRVTPMEMU);
    LogFlow(("%s\n", __FUNCTION__));
    PDMDRV_CHECK_VERSIONS_RETURN_VOID(pDrvIns);

    if (pThis->hSockCtrl != NIL_RTSOCKET)
    {
        int rc = RTSocketShutdown(pThis->hSockCtrl, true /* fRead */, true /* fWrite */);
        AssertRC(rc);

        rc = RTSocketClose(pThis->hSockCtrl);
        AssertRC(rc); RT_NOREF(rc);

        pThis->hSockCtrl = NIL_RTSOCKET;
    }

    if (pThis->hSockData != NIL_RTSOCKET)
    {
        int rc = RTSocketShutdown(pThis->hSockData, true /* fRead */, true /* fWrite */);
        AssertRC(rc);

        rc = RTSocketClose(pThis->hSockData);
        AssertRC(rc); RT_NOREF(rc);

        pThis->hSockCtrl = NIL_RTSOCKET;
    }
}


/** @copydoc FNPDMDRVCONSTRUCT */
static DECLCALLBACK(int) drvTpmEmuConstruct(PPDMDRVINS pDrvIns, PCFGMNODE pCfg, uint32_t fFlags)
{
    RT_NOREF(fFlags);
    PDMDRV_CHECK_VERSIONS_RETURN(pDrvIns);
    PDRVTPMEMU      pThis = PDMINS_2_DATA(pDrvIns, PDRVTPMEMU);
    PCPDMDRVHLPR3   pHlp  = pDrvIns->pHlpR3;

    /*
     * Init the static parts.
     */
    pThis->pDrvIns                                  = pDrvIns;
    pThis->hSockCtrl                                = NIL_RTSOCKET;
    pThis->hSockData                                = NIL_RTSOCKET;
    pThis->enmTpmVers                               = TPMVERSION_UNKNOWN;
    pThis->bLoc                                     = TPM_NO_LOCALITY_SELECTED;

    /* IBase */
    pDrvIns->IBase.pfnQueryInterface                = drvTpmEmuQueryInterface;
    /* ITpmConnector */
    pThis->ITpmConnector.pfnGetVersion              = drvTpmEmuGetVersion;
    pThis->ITpmConnector.pfnGetLocalityMax          = drvTpmEmuGetLocalityMax;
    pThis->ITpmConnector.pfnGetBufferSize           = drvTpmEmuGetBufferSize;
    pThis->ITpmConnector.pfnGetEstablishedFlag      = drvTpmEmuGetEstablishedFlag;
    pThis->ITpmConnector.pfnResetEstablishedFlag    = drvTpmEmuResetEstablishedFlag;
    pThis->ITpmConnector.pfnCmdExec                 = drvTpmEmuCmdExec;
    pThis->ITpmConnector.pfnCmdCancel               = drvTpmEmuCmdCancel;

    /*
     * Validate and read the configuration.
     */
    PDMDRV_VALIDATE_CONFIG_RETURN(pDrvIns, "Location|BufferSize", "");

    char szLocation[_1K];
    int rc = pHlp->pfnCFGMQueryString(pCfg, "Location", &szLocation[0], sizeof(szLocation));
    if (RT_FAILURE(rc))
        return PDMDrvHlpVMSetError(pDrvIns, rc, RT_SRC_POS,
                                   N_("Configuration error: querying \"Location\" resulted in %Rrc"), rc);

    /*
     * Create/Open the socket.
     */
    char *pszPort = strchr(szLocation, ':');
    if (!pszPort)
        return PDMDrvHlpVMSetError(pDrvIns, VERR_NOT_FOUND, RT_SRC_POS,
                                   N_("DrvTpmEmu#%d: The location misses the port to connect to"),
                                   pDrvIns->iInstance);

    *pszPort = '\0'; /* Overwrite temporarily to avoid copying the hostname into a temporary buffer. */
    uint32_t uPort = 0;
    rc = RTStrToUInt32Ex(pszPort + 1, NULL, 10, &uPort);
    if (RT_FAILURE(rc))
        return PDMDrvHlpVMSetError(pDrvIns, rc, RT_SRC_POS,
                                   N_("DrvTpmEmu#%d: The port part of the location is not a numerical value"),
                                   pDrvIns->iInstance);

    rc = RTTcpClientConnect(szLocation, uPort, &pThis->hSockCtrl);
    *pszPort = ':'; /* Restore delimiter before checking the status. */
    if (RT_FAILURE(rc))
        return PDMDrvHlpVMSetError(pDrvIns, rc, RT_SRC_POS,
                                   N_("DrvTpmEmu#%d failed to connect to control socket %s"),
                                   pDrvIns->iInstance, szLocation);

    rc = drvTpmEmuQueryCaps(pThis);
    if (RT_FAILURE(rc))
        return PDMDrvHlpVMSetError(pDrvIns, rc, RT_SRC_POS,
                                   N_("DrvTpmEmu#%d failed to query capabilities offered by %s"),
                                   pDrvIns->iInstance, szLocation);

    if (!(pThis->fCaps & SWTPM_CAP_GET_CONFIG))
        return PDMDrvHlpVMSetError(pDrvIns, VERR_NOT_SUPPORTED, RT_SRC_POS,
                                   N_("DrvTpmEmu#%d Emulated TPM at '%s' misses the GET_CONFIG capability"),
                                   pDrvIns->iInstance, szLocation);

    rc = drvTpmEmuQueryTpmVersion(pThis);
    if (RT_FAILURE(rc))
        return PDMDrvHlpVMSetError(pDrvIns, rc, RT_SRC_POS,
                                   N_("DrvTpmEmu#%d failed to query TPM version from %s"),
                                   pDrvIns->iInstance, szLocation);

    if (pThis->enmTpmVers == TPMVERSION_UNKNOWN)
        return PDMDrvHlpVMSetError(pDrvIns, VERR_NOT_SUPPORTED, RT_SRC_POS,
                                   N_("DrvTpmEmu#%d Emulated TPM version of %s is not supported"),
                                   pDrvIns->iInstance, szLocation);

    const char *pszTpmVers = NULL;
    uint32_t fCapsReq =   SWTPM_CAP_INIT | SWTPM_CAP_SHUTDOWN | SWTPM_CAP_GET_TPMESTABLISHED
                        | SWTPM_CAP_SET_LOCALITY | SWTPM_CAP_CANCEL_TPM_CMD | SWTPM_CAP_GET_STATEBLOB
                        | SWTPM_CAP_SET_STATEBLOB | SWTPM_CAP_STOP | SWTPM_CAP_SET_BUFFERSIZE;
    switch (pThis->enmTpmVers)
    {
        case TPMVERSION_1_2:
            /* No additional capabilities needed. */
            pszTpmVers = "1.2";
            break;
        case TPMVERSION_2_0:
            fCapsReq |= SWTPM_CAP_RESET_TPMESTABLISHED;
            pszTpmVers = "2.0";
            break;
        default:
            AssertMsgFailedReturn(("DrvTpmEmu#%d Emulated TPM version %d is not correctly handled", pDrvIns->iInstance, pThis->enmTpmVers),
                                  VERR_INVALID_STATE);
    }

    if ((pThis->fCaps & fCapsReq) != fCapsReq)
        return PDMDrvHlpVMSetError(pDrvIns, VERR_NOT_SUPPORTED, RT_SRC_POS,
                                   N_("DrvTpmEmu#%d Emulated TPM version of %s does not offer required set of capabilities (%#x requested vs. %#x offered)"),
                                   pDrvIns->iInstance, szLocation, fCapsReq, pThis->fCaps);

    uint32_t cbBufferMax = 0;
    rc = drvTpmEmuQueryBufferSzMax(pThis, &cbBufferMax);
    if (RT_FAILURE(rc))
        return PDMDrvHlpVMSetError(pDrvIns, rc, RT_SRC_POS,
                                   N_("DrvTpmEmu#%d failed to query maximum buffer size from %s"),
                                   pDrvIns->iInstance, szLocation);

    /* Configure the buffer size. */
    rc = pHlp->pfnCFGMQueryU32Def(pCfg, "BufferSize", &pThis->cbBuffer, cbBufferMax);
    if (RT_FAILURE(rc))
        return PDMDrvHlpVMSetError(pDrvIns, rc, RT_SRC_POS,
                                   N_("Configuration error: querying \"BufferSize\" resulted in %Rrc"), rc);

    /* Set the buffer size. */
    rc = drvTpmEmuSetBufferSz(pThis, pThis->cbBuffer);
    if (RT_FAILURE(rc))
        return PDMDrvHlpVMSetError(pDrvIns, rc, RT_SRC_POS,
                                   N_("DrvTpmEmu#%d failed to set buffer size to %u for %s"),
                                   pDrvIns->iInstance, pThis->cbBuffer, szLocation);

    /* Connect the data channel now. */
    /** @todo Allow configuring a different port. */
    *pszPort = '\0'; /* Overwrite temporarily to avoid copying the hostname into a temporary buffer. */
    rc = RTTcpClientConnect(szLocation, uPort + 1, &pThis->hSockData);
    *pszPort = ':'; /* Restore delimiter before checking the status. */
    if (RT_FAILURE(rc))
        return PDMDrvHlpVMSetError(pDrvIns, rc, RT_SRC_POS,
                                   N_("DrvTpmEmu#%d failed to connect to data socket %s"),
                                   pDrvIns->iInstance, szLocation);

    LogRel(("DrvTpmEmu#%d: Connected to %s, emulating TPM version %s\n", pDrvIns->iInstance, szLocation, pszTpmVers));
    return VINF_SUCCESS;
}


/**
 * TPM emulator driver registration record.
 */
const PDMDRVREG g_DrvTpmEmu =
{
    /* u32Version */
    PDM_DRVREG_VERSION,
    /* szName */
    "TpmEmu",
    /* szRCMod */
    "",
    /* szR0Mod */
    "",
    /* pszDescription */
    "TPM emulator driver.",
    /* fFlags */
    PDM_DRVREG_FLAGS_HOST_BITS_DEFAULT,
    /* fClass. */
    PDM_DRVREG_CLASS_STREAM,
    /* cMaxInstances */
    ~0U,
    /* cbInstance */
    sizeof(DRVTPMEMU),
    /* pfnConstruct */
    drvTpmEmuConstruct,
    /* pfnDestruct */
    drvTpmEmuDestruct,
    /* pfnRelocate */
    NULL,
    /* pfnIOCtl */
    NULL,
    /* pfnPowerOn */
    drvTpmEmuPowerOn,
    /* pfnReset */
    NULL,
    /* pfnSuspend */
    NULL,
    /* pfnResume */
    NULL,
    /* pfnAttach */
    NULL,
    /* pfnDetach */
    NULL,
    /* pfnPowerOff */
    drvTpmEmuPowerOff,
    /* pfnSoftReset */
    NULL,
    /* u32EndVersion */
    PDM_DRVREG_VERSION
};