[PATCH 2/5] drivers: security: Add TPM2 implementation of security devices

[seanedmond@linux.microsoft.com]

From: Stephen Carlson <stcarlso@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@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

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@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