[PATCH v4 1/2] fTPM: firmware TPM running in TEE

Sasha Levin
2019-05-30T15:28:07Z

This patch adds support for a software-only implementation of a TPM
running in TEE.

There is extensive documentation of the design here:
https://www.microsoft.com/en-us/research/publication/ftpm-software-implementation-tpm-chip/ .

As well as reference code for the firmware available here:
https://github.com/Microsoft/ms-tpm-20-ref/tree/master/Samples/ARM32-FirmwareTPM

Signed-off-by: Thirupathaiah Annapureddy <thiruan@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/char/tpm/Kconfig | 5 +
drivers/char/tpm/Makefile | 1 +
drivers/char/tpm/tpm_ftpm_tee.c | 380 ++++++++++++++++++++++++++++++++
drivers/char/tpm/tpm_ftpm_tee.h | 40 ++++
4 files changed, 426 insertions(+)
create mode 100644 drivers/char/tpm/tpm_ftpm_tee.c
create mode 100644 drivers/char/tpm/tpm_ftpm_tee.h

diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
index f3e4bc490cf05..8bc9a56cade14 100644
--- a/drivers/char/tpm/Kconfig
+++ b/drivers/char/tpm/Kconfig
@@ -163,6 +163,11 @@ config TCG_VTPM_PROXY
/dev/vtpmX and a server-side file descriptor on which the vTPM
can receive commands.

+config TCG_FTPM_TEE
+ tristate "TEE based fTPM Interface"
+ depends on TEE && OPTEE
+ ---help---
+ This driver proxies for fTPM running in TEE

source "drivers/char/tpm/st33zp24/Kconfig"
endif # TCG_TPM
diff --git a/drivers/char/tpm/Makefile b/drivers/char/tpm/Makefile
index a01c4cab902a6..c354cdff9c625 100644
--- a/drivers/char/tpm/Makefile
+++ b/drivers/char/tpm/Makefile
@@ -33,3 +33,4 @@ obj-$(CONFIG_TCG_TIS_ST33ZP24) += st33zp24/
obj-$(CONFIG_TCG_XEN) += xen-tpmfront.o
obj-$(CONFIG_TCG_CRB) += tpm_crb.o
obj-$(CONFIG_TCG_VTPM_PROXY) += tpm_vtpm_proxy.o
+obj-$(CONFIG_TCG_FTPM_TEE) += tpm_ftpm_tee.o
diff --git a/drivers/char/tpm/tpm_ftpm_tee.c b/drivers/char/tpm/tpm_ftpm_tee.c
new file mode 100644
index 0000000000000..f926b1287988b
--- /dev/null
+++ b/drivers/char/tpm/tpm_ftpm_tee.c
@@ -0,0 +1,380 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) Microsoft Corporation
+ *
+ * Implements a firmware TPM as described here:
+ * https://www.microsoft.com/en-us/research/publication/ftpm-software-implementation-tpm-chip/
+ *
+ * A reference implementation is available here:
+ * https://github.com/microsoft/ms-tpm-20-ref/tree/master/Samples/ARM32-FirmwareTPM/optee_ta/fTPM
+ */
+
+#include <linux/acpi.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/tee_drv.h>
+#include <linux/tpm.h>
+#include <linux/uuid.h>
+
+#include "tpm.h"
+#include "tpm_ftpm_tee.h"
+
+#define DRIVER_NAME "ftpm-tee"
+
+/*
+ * TA_FTPM_UUID: BC50D971-D4C9-42C4-82CB-343FB7F37896
+ *
+ * Randomly generated, and must correspond to the GUID on the TA side.
+ * Defined here in the reference implementation:
+ * https://github.com/microsoft/ms-tpm-20-ref/blob/master/Samples/ARM32-FirmwareTPM/optee_ta/fTPM/include/fTPM.h#L42
+ */
+
+static const uuid_t ftpm_ta_uuid =
+ UUID_INIT(0xBC50D971, 0xD4C9, 0x42C4,
+ 0x82, 0xCB, 0x34, 0x3F, 0xB7, 0xF3, 0x78, 0x96);
+
+/**
+ * ftpm_tee_tpm_op_recv - retrieve fTPM response.
+ *
+ * @chip: the tpm_chip description as specified in driver/char/tpm/tpm.h.
+ * @buf: the buffer to store data.
+ * @count: the number of bytes to read.
+ *
+ * Return:
+ * In case of success the number of bytes received.
+ * On failure, -errno.
+ */
+static int ftpm_tee_tpm_op_recv(struct tpm_chip *chip, u8 *buf, size_t count)
+{
+ struct ftpm_tee_private *pvt_data = dev_get_drvdata(chip->dev.parent);
+ size_t len;
+
+ len = pvt_data->resp_len;
+ if (count < len) {
+ dev_err(&chip->dev,
+ "%s:Invalid size in recv: count=%zd, resp_len=%zd\n",
+ __func__, count, len);
+ return -EIO;
+ }
+
+ memcpy(buf, pvt_data->resp_buf, len);
+ pvt_data->resp_len = 0;
+
+ return len;
+}
+
+/**
+ * ftpm_tee_tpm_op_send - send TPM commands through the TEE shared memory.
+ *
+ * @chip: the tpm_chip description as specified in driver/char/tpm/tpm.h
+ * @buf: the buffer to send.
+ * @len: the number of bytes to send.
+ *
+ * Return:
+ * In case of success, returns 0.
+ * On failure, -errno
+ */
+static int ftpm_tee_tpm_op_send(struct tpm_chip *chip, u8 *buf, size_t len)
+{
+ struct ftpm_tee_private *pvt_data = dev_get_drvdata(chip->dev.parent);
+ size_t resp_len;
+ int rc;
+ u8 *temp_buf;
+ struct tpm_header *resp_header;
+ struct tee_ioctl_invoke_arg transceive_args;
+ struct tee_param command_params[4];
+ struct tee_shm *shm = pvt_data->shm;
+
+ if (len > MAX_COMMAND_SIZE) {
+ dev_err(&chip->dev,
+ "%s:len=%zd exceeds MAX_COMMAND_SIZE supported by fTPM TA\n",
+ __func__, len);
+ return -EIO;
+ }
+
+ memset(&transceive_args, 0, sizeof(transceive_args));
+ memset(command_params, 0, sizeof(command_params));
+ pvt_data->resp_len = 0;
+
+ /* Invoke FTPM_OPTEE_TA_SUBMIT_COMMAND function of fTPM TA */
+ transceive_args = (struct tee_ioctl_invoke_arg) {
+ .func = FTPM_OPTEE_TA_SUBMIT_COMMAND,
+ .session = pvt_data->session,
+ .num_params = 4,
+ };
+
+ /* Fill FTPM_OPTEE_TA_SUBMIT_COMMAND parameters */
+ command_params[0] = (struct tee_param) {
+ .attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_INPUT,
+ .u.memref = {
+ .shm = shm,
+ .size = len,
+ .shm_offs = 0,
+ },
+ };
+
+ temp_buf = tee_shm_get_va(shm, 0);
+ if (IS_ERR(temp_buf)) {
+ dev_err(&chip->dev, "%s:tee_shm_get_va failed for transmit\n",
+ __func__);
+ return PTR_ERR(temp_buf);
+ }
+ memset(temp_buf, 0, (MAX_COMMAND_SIZE + MAX_RESPONSE_SIZE));
+
+ memcpy(temp_buf, buf, len);
+
+ command_params[1] = (struct tee_param) {
+ .attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_INOUT,
+ .u.memref = {
+ .shm = shm,
+ .size = MAX_RESPONSE_SIZE,
+ .shm_offs = MAX_COMMAND_SIZE,
+ },
+ };
+
+ rc = tee_client_invoke_func(pvt_data->ctx, &transceive_args,
+ command_params);
+ if ((rc < 0) || (transceive_args.ret != 0)) {
+ dev_err(&chip->dev, "%s:SUBMIT_COMMAND invoke error: 0x%x\n",
+ __func__, transceive_args.ret);
+ return (rc < 0) ? rc : transceive_args.ret;
+ }
+
+ temp_buf = tee_shm_get_va(shm, command_params[1].u.memref.shm_offs);
+ if (IS_ERR(temp_buf)) {
+ dev_err(&chip->dev, "%s:tee_shm_get_va failed for receive\n",
+ __func__);
+ return PTR_ERR(temp_buf);
+ }
+
+ resp_header = (struct tpm_header *)temp_buf;
+ resp_len = be32_to_cpu(resp_header->length);
+
+ /* sanity check resp_len */
+ if (resp_len < TPM_HEADER_SIZE) {
+ dev_err(&chip->dev, "%s:tpm response header too small\n",
+ __func__);
+ return -EIO;
+ }
+ if (resp_len > MAX_RESPONSE_SIZE) {
+ dev_err(&chip->dev,
+ "%s:resp_len=%zd exceeds MAX_RESPONSE_SIZE\n",
+ __func__, resp_len);
+ return -EIO;
+ }
+
+ /* sanity checks look good, cache the response */
+ memcpy(pvt_data->resp_buf, temp_buf, resp_len);
+ pvt_data->resp_len = resp_len;
+
+ return 0;
+}
+
+static void ftpm_tee_tpm_op_cancel(struct tpm_chip *chip)
+{
+ /* not supported */
+}
+
+static u8 ftpm_tee_tpm_op_status(struct tpm_chip *chip)
+{
+ return 0;
+}
+
+static bool ftpm_tee_tpm_req_canceled(struct tpm_chip *chip, u8 status)
+{
+ return 0;
+}
+
+static const struct tpm_class_ops ftpm_tee_tpm_ops = {
+ .flags = TPM_OPS_AUTO_STARTUP,
+ .recv = ftpm_tee_tpm_op_recv,
+ .send = ftpm_tee_tpm_op_send,
+ .cancel = ftpm_tee_tpm_op_cancel,
+ .status = ftpm_tee_tpm_op_status,
+ .req_complete_mask = 0,
+ .req_complete_val = 0,
+ .req_canceled = ftpm_tee_tpm_req_canceled,
+};
+
+/*
+ * Check whether this driver supports the fTPM TA in the TEE instance
+ * represented by the params (ver/data) to this function.
+ */
+static int ftpm_tee_match(struct tee_ioctl_version_data *ver, const void *data)
+{
+ /*
+ * Currently this driver only support GP Complaint OPTEE based fTPM TA
+ */
+ if ((ver->impl_id == TEE_IMPL_ID_OPTEE) &&
+ (ver->gen_caps & TEE_GEN_CAP_GP))
+ return 1;
+ else
+ return 0;
+}
+
+/*
+ * Undo what has been done in ftpm_tee_probe
+ */
+static void ftpm_tee_deinit(struct ftpm_tee_private *pvt_data)
+{
+ /* Release the chip */
+ tpm_chip_unregister(pvt_data->chip);
+
+ /* frees chip */
+ if (pvt_data->chip)
+ put_device(&pvt_data->chip->dev);
+
+ if (pvt_data->ctx) {
+ /* Free the shared memory pool */
+ tee_shm_free(pvt_data->shm);
+
+ /* close the existing session with fTPM TA*/
+ tee_client_close_session(pvt_data->ctx, pvt_data->session);
+
+ /* close the context with TEE driver */
+ tee_client_close_context(pvt_data->ctx);
+ }
+
+ /* memory allocated with devm_kzalloc() is freed automatically */
+}
+
+/**
+ * ftpm_tee_probe - initialize the fTPM
+ * @pdev: the platform_device description.
+ *
+ * Return:
+ * On success, 0. On failure, -errno.
+ */
+static int ftpm_tee_probe(struct platform_device *pdev)
+{
+ int rc;
+ struct tpm_chip *chip;
+ struct device *dev = &pdev->dev;
+ struct ftpm_tee_private *pvt_data = NULL;
+ struct tee_ioctl_open_session_arg sess_arg;
+
+ pvt_data = devm_kzalloc(dev, sizeof(struct ftpm_tee_private),
+ GFP_KERNEL);
+ if (!pvt_data)
+ return -ENOMEM;
+
+ dev_set_drvdata(dev, pvt_data);
+
+ /* Open context with TEE driver */
+ pvt_data->ctx = tee_client_open_context(NULL, ftpm_tee_match, NULL,
+ NULL);
+ if (IS_ERR(pvt_data->ctx)) {
+ dev_err(dev, "%s:tee_client_open_context failed\n", __func__);
+ return -EPROBE_DEFER;
+ }
+
+ /* Open a session with fTPM TA */
+ memset(&sess_arg, 0, sizeof(sess_arg));
+ memcpy(sess_arg.uuid, ftpm_ta_uuid.b, TEE_IOCTL_UUID_LEN);
+ sess_arg.clnt_login = TEE_IOCTL_LOGIN_PUBLIC;
+ sess_arg.num_params = 0;
+
+ rc = tee_client_open_session(pvt_data->ctx, &sess_arg, NULL);
+ if ((rc < 0) || (sess_arg.ret != 0)) {
+ dev_err(dev, "%s:tee_client_open_session failed, err=%x\n",
+ __func__, sess_arg.ret);
+ rc = -EINVAL;
+ goto out_tee_session;
+ }
+ pvt_data->session = sess_arg.session;
+
+ /* Allocate dynamic shared memory with fTPM TA */
+ pvt_data->shm = tee_shm_alloc(pvt_data->ctx,
+ (MAX_COMMAND_SIZE + MAX_RESPONSE_SIZE),
+ TEE_SHM_MAPPED | TEE_SHM_DMA_BUF);
+ if (IS_ERR(pvt_data->shm)) {
+ dev_err(dev, "%s:tee_shm_alloc failed\n", __func__);
+ rc = -ENOMEM;
+ goto out_shm_alloc;
+ }
+
+ /* Allocate new struct tpm_chip instance */
+ chip = tpm_chip_alloc(dev, &ftpm_tee_tpm_ops);
+ if (IS_ERR(chip)) {
+ dev_err(dev, "%s:tpm_chip_alloc failed\n", __func__);
+ rc = PTR_ERR(chip);
+ goto out_chip_alloc;
+ }
+
+ pvt_data->chip = chip;
+ pvt_data->chip->flags |= TPM_CHIP_FLAG_TPM2;
+
+ /* Create a character device for the fTPM */
+ rc = tpm_chip_register(pvt_data->chip);
+ if (rc) {
+ dev_err(dev, "%s:tpm_chip_register failed with rc=%d\n",
+ __func__, rc);
+ goto out_chip;
+ }
+
+ return 0;
+
+out_chip:
+ put_device(&pvt_data->chip->dev);
+out_chip_alloc:
+ tee_shm_free(pvt_data->shm);
+out_shm_alloc:
+ tee_client_close_session(pvt_data->ctx, pvt_data->session);
+out_tee_session:
+ tee_client_close_context(pvt_data->ctx);
+
+ return rc;
+}
+
+/**
+ * ftpm_tee_remove - remove the TPM device
+ * @pdev: the platform_device description.
+ *
+ * Return:
+ * 0 in case of success.
+ */
+static int ftpm_tee_remove(struct platform_device *pdev)
+{
+ struct ftpm_tee_private *pvt_data = dev_get_drvdata(&pdev->dev);
+
+ /* Release the chip */
+ tpm_chip_unregister(pvt_data->chip);
+
+ /* frees chip */
+ put_device(&pvt_data->chip->dev);
+
+ /* Free the shared memory pool */
+ tee_shm_free(pvt_data->shm);
+
+ /* close the existing session with fTPM TA*/
+ tee_client_close_session(pvt_data->ctx, pvt_data->session);
+
+ /* close the context with TEE driver */
+ tee_client_close_context(pvt_data->ctx);
+
+ /* memory allocated with devm_kzalloc() is freed automatically */
+
+ return 0;
+}
+
+static const struct of_device_id of_ftpm_tee_ids[] = {
+ { .compatible = "microsoft,ftpm" },
+ { }
+};
+MODULE_DEVICE_TABLE(of, of_ftpm_tee_ids);
+
+static struct platform_driver ftpm_tee_driver = {
+ .driver = {
+ .name = DRIVER_NAME,
+ .of_match_table = of_match_ptr(of_ftpm_tee_ids),
+ },
+ .probe = ftpm_tee_probe,
+ .remove = ftpm_tee_remove,
+};
+
+module_platform_driver(ftpm_tee_driver);
+
+MODULE_AUTHOR("Thirupathaiah Annapureddy <thiruan@microsoft.com>");
+MODULE_DESCRIPTION("TPM Driver for fTPM TA in TEE");
+MODULE_LICENSE("GPL v2");
diff --git a/drivers/char/tpm/tpm_ftpm_tee.h b/drivers/char/tpm/tpm_ftpm_tee.h
new file mode 100644
index 0000000000000..b09ee7be45459
--- /dev/null
+++ b/drivers/char/tpm/tpm_ftpm_tee.h
@@ -0,0 +1,40 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) Microsoft Corporation
+ */
+
+#ifndef __TPM_FTPM_TEE_H__
+#define __TPM_FTPM_TEE_H__
+
+#include <linux/tee_drv.h>
+#include <linux/tpm.h>
+#include <linux/uuid.h>
+
+/* The TAFs ID implemented in this TA */
+#define FTPM_OPTEE_TA_SUBMIT_COMMAND (0)
+#define FTPM_OPTEE_TA_EMULATE_PPI (1)
+
+/* max. buffer size supported by fTPM */
+#define MAX_COMMAND_SIZE 4096
+#define MAX_RESPONSE_SIZE 4096
+
+/**
+ * struct ftpm_tee_private - fTPM's private data
+ * @chip: struct tpm_chip instance registered with tpm framework.
+ * @state: internal state
+ * @session: fTPM TA session identifier.
+ * @resp_len: cached response buffer length.
+ * @resp_buf: cached response buffer.
+ * @ctx: TEE context handler.
+ * @shm: Memory pool shared with fTPM TA in TEE.
+ */
+struct ftpm_tee_private {
+ struct tpm_chip *chip;
+ u32 session;
+ size_t resp_len;
+ u8 resp_buf[MAX_RESPONSE_SIZE];
+ struct tee_context *ctx;
+ struct tee_shm *shm;
+};
+
+#endif /* __TPM_FTPM_TEE_H__ */
--
2.20.1