[PATCH 2/5] drivers: security: Add TPM2 implementation of security devices
Simon Glass
sjg at chromium.org
Thu Aug 17 15:41:43 CEST 2023
Hi Sean,
On Fri, 11 Aug 2023 at 18:28, <seanedmond at linux.microsoft.com> wrote:
>
> From: Stephen Carlson <stcarlso at linux.microsoft.com>
>
> This implementation of the security uclass driver allows existing TPM2
> devices declared in the device tree to be referenced for storing the OS
> anti-rollback counter, using the TPM2 non-volatile storage API.
>
> Signed-off-by: Stephen Carlson <stcarlso at linux.microsoft.com>
> ---
> MAINTAINERS | 1 +
> drivers/security/Makefile | 1 +
> drivers/security/security-tpm.c | 173 ++++++++++++++++++++++++++++++++
> include/tpm-v2.h | 1 +
> 4 files changed, 176 insertions(+)
> create mode 100644 drivers/security/security-tpm.c
This is a bit wonky w.r.t driver model. The TPM itself should
implement this API, perhaps ina separate file shared with all v2 TPMs.
You should not be opening the device, etc. in here.
I hope that makes sense...you effectively need to turn the TPM into a
multi-function device within driver model. Of course TPMs are
multi-function devices anyway, but here you are making their functions
available more explicitly with a nicer API.
Then you can call the TPM API to do what you want, but at least you
know that the TPM has been probed before you start.
Regards,
Simon
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 73b6943e03..257660a847 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -1444,6 +1444,7 @@ S: Maintained
> F: drivers/security/Kconfig
> F: drivers/security/Makefile
> F: drivers/security/sandbox_security.c
> +F: drivers/security/security-tpm.c
> F: drivers/security/security-uclass.c
>
> SEMIHOSTING
> diff --git a/drivers/security/Makefile b/drivers/security/Makefile
> index ed10c3f234..e81966bb4a 100644
> --- a/drivers/security/Makefile
> +++ b/drivers/security/Makefile
> @@ -4,3 +4,4 @@
>
> obj-$(CONFIG_DM_SECURITY) += security-uclass.o
> obj-$(CONFIG_SECURITY_SANDBOX) += sandbox_security.o
> +obj-$(CONFIG_SECURITY_TPM) += security-tpm.o
> diff --git a/drivers/security/security-tpm.c b/drivers/security/security-tpm.c
> new file mode 100644
> index 0000000000..9070dd49ac
> --- /dev/null
> +++ b/drivers/security/security-tpm.c
> @@ -0,0 +1,173 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Copyright (c) 2021 Microsoft, Inc
> + * Written by Stephen Carlson <stcarlso at microsoft.com>
> + */
> +
> +#include <common.h>
> +#include <dm.h>
> +#include <fdtdec.h>
> +#include <dm-security.h>
> +#include <tpm-v2.h>
> +
> +struct security_state {
> + u32 index_arbvn;
> + struct udevice *tpm_dev;
> +};
> +
> +static int tpm_security_init(struct udevice *tpm_dev)
> +{
> + int res;
> +
> + /* Initialize TPM but allow reuse of existing session */
> + res = tpm_open(tpm_dev);
> + if (res == -EBUSY) {
> + log(UCLASS_SECURITY, LOGL_DEBUG,
> + "Existing TPM session found, reusing\n");
> + } else {
> + if (res) {
> + log(UCLASS_SECURITY, LOGL_ERR,
> + "TPM initialization failed (ret=%d)\n", res);
> + return res;
> + }
> +
> + res = tpm2_startup(tpm_dev, TPM2_SU_CLEAR);
> + if (res) {
> + log(UCLASS_SECURITY, LOGL_ERR,
> + "TPM startup failed (ret=%d)\n", res);
> + return res;
> + }
> + }
> +
> + return 0;
> +}
> +
> +static int tpm_security_arbvn_get(struct udevice *dev, u64 *arbvn)
> +{
> + struct security_state *priv = dev_get_priv(dev);
> + int ret;
> +
> + if (!arbvn)
> + return -EINVAL;
> +
> + ret = tpm2_nv_read_value(priv->tpm_dev, priv->index_arbvn, arbvn,
> + sizeof(u64));
> + if (ret == TPM2_RC_NV_UNINITIALIZED) {
> + /* Expected if no OS image has been loaded before */
> + log(UCLASS_SECURITY, LOGL_INFO,
> + "No previous OS image, defaulting ARBVN to 0\n");
> + *arbvn = 0ULL;
> + } else if (ret) {
> + log(UCLASS_SECURITY, LOGL_ERR,
> + "Unable to read ARBVN from TPM (ret=%d)\n", ret);
> + return ret;
> + }
> +
> + return 0;
> +}
> +
> +static int tpm_security_arbvn_set(struct udevice *dev, u64 arbvn)
> +{
> + struct security_state *priv = dev_get_priv(dev);
> + struct udevice *tpm_dev = priv->tpm_dev;
> + u64 old_arbvn;
> + int ret;
> +
> + ret = tpm_security_arbvn_get(dev, &old_arbvn);
> + if (ret)
> + return ret;
> +
> + if (arbvn < old_arbvn)
> + return -EPERM;
> +
> + if (arbvn > old_arbvn) {
> + ret = tpm2_nv_write_value(tpm_dev, priv->index_arbvn, &arbvn,
> + sizeof(u64));
> + if (ret) {
> + log(UCLASS_SECURITY, LOGL_ERR,
> + "Unable to write ARBVN to TPM (ret=%d)\n", ret);
> + return ret;
> + }
> + }
> +
> + return 0;
> +}
> +
> +static const struct dm_security_ops tpm_security_ops = {
> + .arbvn_get = tpm_security_arbvn_get,
> + .arbvn_set = tpm_security_arbvn_set,
> +};
> +
> +static int tpm_security_probe(struct udevice *dev)
> +{
> + struct security_state *priv = dev_get_priv(dev);
> + struct udevice *tpm_dev = priv->tpm_dev;
> + u32 index = priv->index_arbvn;
> + int ret;
> +
> + if (!tpm_dev) {
> + log(UCLASS_SECURITY, LOGL_ERR,
> + "TPM device not defined in DTS\n");
> + return -EINVAL;
> + }
> +
> + ret = tpm_security_init(tpm_dev);
> + if (ret)
> + return ret;
> +
> + ret = tpm2_nv_define_space(tpm_dev, index, sizeof(u64), TPMA_NV_PPREAD |
> + TPMA_NV_PPWRITE | TPMA_NV_PLATFORMCREATE,
> + NULL, 0);
> + /* NV_DEFINED is an expected error if ARBVN already initialized */
> + if (ret == TPM2_RC_NV_DEFINED)
> + log(UCLASS_SECURITY, LOGL_DEBUG,
> + "ARBVN index %u already defined\n", index);
> + else if (ret) {
> + log(UCLASS_SECURITY, LOGL_ERR,
> + "Unable to create ARBVN NV index (ret=%d)\n", ret);
> + return ret;
> + }
> +
> + return 0;
> +}
> +
> +static int tpm_security_remove(struct udevice *dev)
> +{
> + struct security_state *priv = dev_get_priv(dev);
> +
> + return tpm_close(priv->tpm_dev);
> +}
> +
> +static int tpm_security_ofdata_to_platdata(struct udevice *dev)
> +{
> + const u32 phandle = (u32)dev_read_u32_default(dev, "tpm", 0);
> + struct security_state *priv = dev_get_priv(dev);
> + struct udevice *tpm_dev;
> + int ret;
> +
> + ret = uclass_get_device_by_phandle_id(UCLASS_TPM, phandle, &tpm_dev);
> + if (ret) {
> + log(UCLASS_SECURITY, LOGL_ERR, "TPM node in DTS is invalid\n");
> + return ret;
> + }
> +
> + priv->index_arbvn = (u32)dev_read_u32_default(dev, "arbvn-nv-index", 0);
> + priv->tpm_dev = tpm_dev;
> + return 0;
> +}
> +
> +static const struct udevice_id tpm_security_ids[] = {
> + { .compatible = "tpm,security" },
> + { }
> +};
> +
> +U_BOOT_DRIVER(security_tpm) = {
> + .name = "security_tpm",
> + .id = UCLASS_SECURITY,
> + .priv_auto = sizeof(struct security_state),
> + .of_match = tpm_security_ids,
> + .of_to_plat = tpm_security_ofdata_to_platdata,
> + .probe = tpm_security_probe,
> + .remove = tpm_security_remove,
> + .ops = &tpm_security_ops,
> +};
> diff --git a/include/tpm-v2.h b/include/tpm-v2.h
> index 2b6980e441..49bf0f0ba4 100644
> --- a/include/tpm-v2.h
> +++ b/include/tpm-v2.h
> @@ -321,6 +321,7 @@ enum tpm2_return_codes {
> TPM2_RC_COMMAND_CODE = TPM2_RC_VER1 + 0x0043,
> TPM2_RC_AUTHSIZE = TPM2_RC_VER1 + 0x0044,
> TPM2_RC_AUTH_CONTEXT = TPM2_RC_VER1 + 0x0045,
> + TPM2_RC_NV_UNINITIALIZED = TPM2_RC_VER1 + 0x04a,
> TPM2_RC_NV_DEFINED = TPM2_RC_VER1 + 0x004c,
> TPM2_RC_NEEDS_TEST = TPM2_RC_VER1 + 0x0053,
> TPM2_RC_WARN = 0x0900,
> --
> 2.40.0
>
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