[RFC 4/7] KEYS: trusted: Introduce TEE based Trusted Keys

[Sumit Garg]

Add support for TEE based trusted keys where TEE provides the functionality
to seal and unseal trusted keys using hardware unique key.

Refer to Documentation/tee.txt for detailed information about TEE.

Approach taken in this patch acts as an alternative to a TPM device in case
platform doesn't possess one.

Signed-off-by: Sumit Garg <sumit.garg@xxxxxxxxxx>
---
 include/keys/tee_trusted.h  |  84 ++++++++
 include/keys/trusted-type.h |   1 +
 security/keys/Kconfig       |   3 +
 security/keys/Makefile      |   3 +
 security/keys/tee_trusted.c | 506 ++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 597 insertions(+)
 create mode 100644 include/keys/tee_trusted.h
 create mode 100644 security/keys/tee_trusted.c

diff --git a/include/keys/tee_trusted.h b/include/keys/tee_trusted.h
new file mode 100644
index 0000000..e5c0042
--- /dev/null
+++ b/include/keys/tee_trusted.h
@@ -0,0 +1,84 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2019 Linaro Ltd.
+ *
+ * Author:
+ * Sumit Garg <sumit.garg@xxxxxxxxxx>
+ */
+
+#ifndef __TEE_TRUSTED_KEY_H
+#define __TEE_TRUSTED_KEY_H
+
+#include <linux/tee_drv.h>
+
+#define DRIVER_NAME "tee-trusted-key"
+
+/*
+ * Get random data for symmetric key
+ *
+ * [out]     memref[0]        Random data
+ *
+ * Result:
+ * TEE_SUCCESS - Invoke command success
+ * TEE_ERROR_BAD_PARAMETERS - Incorrect input param
+ */
+#define TA_CMD_GET_RANDOM	0x0
+
+/*
+ * Seal trusted key using hardware unique key
+ *
+ * [in]      memref[0]        Plain key
+ * [out]     memref[1]        Sealed key datablob
+ *
+ * Result:
+ * TEE_SUCCESS - Invoke command success
+ * TEE_ERROR_BAD_PARAMETERS - Incorrect input param
+ */
+#define TA_CMD_SEAL		0x1
+
+/*
+ * Unseal trusted key using hardware unique key
+ *
+ * [in]      memref[0]        Sealed key datablob
+ * [out]     memref[1]        Plain key
+ *
+ * Result:
+ * TEE_SUCCESS - Invoke command success
+ * TEE_ERROR_BAD_PARAMETERS - Incorrect input param
+ */
+#define TA_CMD_UNSEAL		0x2
+
+/**
+ * struct trusted_key_private - TEE Trusted key private data
+ * @dev:		TEE based Trusted key device.
+ * @ctx:		TEE context handler.
+ * @session_id:		Trusted key TA session identifier.
+ * @shm_pool:		Memory pool shared with TEE device.
+ */
+struct trusted_key_private {
+	struct device *dev;
+	struct tee_context *ctx;
+	u32 session_id;
+	u32 data_rate;
+	struct tee_shm *shm_pool;
+};
+
+#define TEE_KEY_DEBUG 0
+
+#if TEE_KEY_DEBUG
+static inline void dump_tee_payload(struct trusted_key_payload *p)
+{
+	pr_info("trusted_key: key_len %d\n", p->key_len);
+	print_hex_dump(KERN_INFO, "key ", DUMP_PREFIX_NONE,
+		       16, 1, p->key, p->key_len, 0);
+	pr_info("trusted_key: bloblen %d\n", p->blob_len);
+	print_hex_dump(KERN_INFO, "blob ", DUMP_PREFIX_NONE,
+		       16, 1, p->blob, p->blob_len, 0);
+}
+#else
+static inline void dump_tee_payload(struct trusted_key_payload *p)
+{
+}
+#endif
+
+#endif
diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h
index a94c03a..363ec83 100644
--- a/include/keys/trusted-type.h
+++ b/include/keys/trusted-type.h
@@ -41,5 +41,6 @@ struct trusted_key_options {
 };
 
 extern struct key_type key_type_trusted;
+extern struct key_type key_type_tee_trusted;
 
 #endif /* _KEYS_TRUSTED_TYPE_H */
diff --git a/security/keys/Kconfig b/security/keys/Kconfig
index ee502e4..b206a20 100644
--- a/security/keys/Kconfig
+++ b/security/keys/Kconfig
@@ -70,6 +70,9 @@ config TRUSTED_KEYS
 	  if the boot PCRs and other criteria match.  Userspace will only ever
 	  see encrypted blobs.
 
+	  It also provides support for alternative TEE based Trusted keys
+	  generation and sealing in case TPM isn't present.
+
 	  If you are unsure as to whether this is required, answer N.
 
 config ENCRYPTED_KEYS
diff --git a/security/keys/Makefile b/security/keys/Makefile
index 9cef540..07ad3e2 100644
--- a/security/keys/Makefile
+++ b/security/keys/Makefile
@@ -30,3 +30,6 @@ obj-$(CONFIG_ASYMMETRIC_KEY_TYPE) += keyctl_pkey.o
 obj-$(CONFIG_BIG_KEYS) += big_key.o
 obj-$(CONFIG_TRUSTED_KEYS) += trusted.o
 obj-$(CONFIG_ENCRYPTED_KEYS) += encrypted-keys/
+ifdef CONFIG_TEE
+obj-$(CONFIG_TRUSTED_KEYS) += tee_trusted.o
+endif
diff --git a/security/keys/tee_trusted.c b/security/keys/tee_trusted.c
new file mode 100644
index 0000000..081e45e
--- /dev/null
+++ b/security/keys/tee_trusted.c
@@ -0,0 +1,506 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 Linaro Ltd.
+ *
+ * Author:
+ * Sumit Garg <sumit.garg@xxxxxxxxxx>
+ */
+
+#include <linux/err.h>
+#include <linux/key-type.h>
+#include <linux/module.h>
+#include <linux/parser.h>
+#include <linux/rcupdate.h>
+#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/tpm.h>
+#include <linux/uaccess.h>
+#include <linux/uuid.h>
+
+#include <keys/trusted-type.h>
+#include <keys/user-type.h>
+#include <keys/tee_trusted.h>
+
+static struct trusted_key_private pvt_data;
+
+/*
+ * Have the TEE seal(encrypt) the symmetric key
+ */
+static int tee_key_seal(struct trusted_key_payload *p)
+{
+	int ret = 0;
+	struct tee_ioctl_invoke_arg inv_arg;
+	struct tee_param param[4];
+	struct tee_shm *reg_shm_in = NULL, *reg_shm_out = NULL;
+
+	memset(&inv_arg, 0, sizeof(inv_arg));
+	memset(&param, 0, sizeof(param));
+
+	reg_shm_in = tee_shm_register(pvt_data.ctx, (unsigned long)p->key,
+				      p->key_len, TEE_SHM_DMA_BUF |
+				      TEE_SHM_KERNEL_MAPPED);
+	if (IS_ERR(reg_shm_in)) {
+		dev_err(pvt_data.dev, "key shm register failed\n");
+		return PTR_ERR(reg_shm_in);
+	}
+
+	reg_shm_out = tee_shm_register(pvt_data.ctx, (unsigned long)p->blob,
+				       sizeof(p->blob), TEE_SHM_DMA_BUF |
+				       TEE_SHM_KERNEL_MAPPED);
+	if (IS_ERR(reg_shm_out)) {
+		dev_err(pvt_data.dev, "blob shm register failed\n");
+		ret = PTR_ERR(reg_shm_out);
+		goto out;
+	}
+
+	inv_arg.func = TA_CMD_SEAL;
+	inv_arg.session = pvt_data.session_id;
+	inv_arg.num_params = 4;
+
+	param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_INPUT;
+	param[0].u.memref.shm = reg_shm_in;
+	param[0].u.memref.size = p->key_len;
+	param[0].u.memref.shm_offs = 0;
+	param[1].attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_OUTPUT;
+	param[1].u.memref.shm = reg_shm_out;
+	param[1].u.memref.size = sizeof(p->blob);
+	param[1].u.memref.shm_offs = 0;
+
+	ret = tee_client_invoke_func(pvt_data.ctx, &inv_arg, param);
+	if ((ret < 0) || (inv_arg.ret != 0)) {
+		dev_err(pvt_data.dev, "TA_CMD_SEAL invoke err: %x\n",
+			inv_arg.ret);
+		ret = -EFAULT;
+	} else {
+		p->blob_len = param[1].u.memref.size;
+	}
+
+out:
+	if (reg_shm_out)
+		tee_shm_free(reg_shm_out);
+	if (reg_shm_in)
+		tee_shm_free(reg_shm_in);
+
+	return ret;
+}
+
+/*
+ * Have the TEE unseal(decrypt) the symmetric key
+ */
+static int tee_key_unseal(struct trusted_key_payload *p)
+{
+	int ret = 0;
+	struct tee_ioctl_invoke_arg inv_arg;
+	struct tee_param param[4];
+	struct tee_shm *reg_shm_in = NULL, *reg_shm_out = NULL;
+
+	memset(&inv_arg, 0, sizeof(inv_arg));
+	memset(&param, 0, sizeof(param));
+
+	reg_shm_in = tee_shm_register(pvt_data.ctx, (unsigned long)p->blob,
+				      p->blob_len, TEE_SHM_DMA_BUF |
+				      TEE_SHM_KERNEL_MAPPED);
+	if (IS_ERR(reg_shm_in)) {
+		dev_err(pvt_data.dev, "blob shm register failed\n");
+		return PTR_ERR(reg_shm_in);
+	}
+
+	reg_shm_out = tee_shm_register(pvt_data.ctx, (unsigned long)p->key,
+				       sizeof(p->key), TEE_SHM_DMA_BUF |
+				       TEE_SHM_KERNEL_MAPPED);
+	if (IS_ERR(reg_shm_out)) {
+		dev_err(pvt_data.dev, "key shm register failed\n");
+		ret = PTR_ERR(reg_shm_out);
+		goto out;
+	}
+
+	inv_arg.func = TA_CMD_UNSEAL;
+	inv_arg.session = pvt_data.session_id;
+	inv_arg.num_params = 4;
+
+	param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_INPUT;
+	param[0].u.memref.shm = reg_shm_in;
+	param[0].u.memref.size = p->blob_len;
+	param[0].u.memref.shm_offs = 0;
+	param[1].attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_OUTPUT;
+	param[1].u.memref.shm = reg_shm_out;
+	param[1].u.memref.size = sizeof(p->key);
+	param[1].u.memref.shm_offs = 0;
+
+	ret = tee_client_invoke_func(pvt_data.ctx, &inv_arg, param);
+	if ((ret < 0) || (inv_arg.ret != 0)) {
+		dev_err(pvt_data.dev, "TA_CMD_UNSEAL invoke err: %x\n",
+			inv_arg.ret);
+		ret = -EFAULT;
+	} else {
+		p->key_len = param[1].u.memref.size;
+	}
+
+out:
+	if (reg_shm_out)
+		tee_shm_free(reg_shm_out);
+	if (reg_shm_in)
+		tee_shm_free(reg_shm_in);
+
+	return ret;
+}
+
+/*
+ * Have the TEE generate random symmetric key
+ */
+static int tee_get_random(unsigned char *key, unsigned int key_len)
+{
+	int ret = 0;
+	struct tee_ioctl_invoke_arg inv_arg;
+	struct tee_param param[4];
+	struct tee_shm *reg_shm = NULL;
+
+	memset(&inv_arg, 0, sizeof(inv_arg));
+	memset(&param, 0, sizeof(param));
+
+	reg_shm = tee_shm_register(pvt_data.ctx, (unsigned long)key, key_len,
+				   TEE_SHM_DMA_BUF | TEE_SHM_KERNEL_MAPPED);
+	if (IS_ERR(reg_shm)) {
+		dev_err(pvt_data.dev, "random key shm register failed\n");
+		return PTR_ERR(reg_shm);
+	}
+
+	inv_arg.func = TA_CMD_GET_RANDOM;
+	inv_arg.session = pvt_data.session_id;
+	inv_arg.num_params = 4;
+
+	param[0].attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_OUTPUT;
+	param[0].u.memref.shm = reg_shm;
+	param[0].u.memref.size = key_len;
+	param[0].u.memref.shm_offs = 0;
+
+	ret = tee_client_invoke_func(pvt_data.ctx, &inv_arg, param);
+	if ((ret < 0) || (inv_arg.ret != 0)) {
+		dev_err(pvt_data.dev, "TA_CMD_GET_RANDOM invoke err: %x\n",
+			inv_arg.ret);
+		ret = -EFAULT;
+	} else {
+		ret = param[0].u.memref.size;
+	}
+
+	tee_shm_free(reg_shm);
+
+	return ret;
+}
+
+enum {
+	Opt_err,
+	Opt_new, Opt_load
+};
+
+static const match_table_t key_tokens = {
+	{Opt_new, "new"},
+	{Opt_load, "load"},
+	{Opt_err, NULL}
+};
+
+/*
+ * datablob_parse - parse the keyctl data and fill in the
+ *		    payload structure
+ *
+ * On success returns 0, otherwise -EINVAL.
+ */
+static int datablob_parse(char *datablob, struct trusted_key_payload *p)
+{
+	substring_t args[MAX_OPT_ARGS];
+	long keylen;
+	int ret = -EINVAL;
+	int key_cmd;
+	char *c;
+
+	/* main command */
+	c = strsep(&datablob, " \t");
+	if (!c)
+		return -EINVAL;
+
+	key_cmd = match_token(c, key_tokens, args);
+	switch (key_cmd) {
+	case Opt_new:
+		/* first argument is key size */
+		c = strsep(&datablob, " \t");
+		if (!c)
+			return -EINVAL;
+		ret = kstrtol(c, 10, &keylen);
+		if (ret < 0 || keylen < MIN_KEY_SIZE || keylen > MAX_KEY_SIZE)
+			return -EINVAL;
+		p->key_len = keylen;
+		ret = Opt_new;
+		break;
+	case Opt_load:
+		/* first argument is sealed blob */
+		c = strsep(&datablob, " \t");
+		if (!c)
+			return -EINVAL;
+		p->blob_len = strlen(c) / 2;
+		if (p->blob_len > MAX_BLOB_SIZE)
+			return -EINVAL;
+		ret = hex2bin(p->blob, c, p->blob_len);
+		if (ret < 0)
+			return -EINVAL;
+		ret = Opt_load;
+		break;
+	case Opt_err:
+		return -EINVAL;
+	}
+
+	return ret;
+}
+
+static struct trusted_key_payload *trusted_payload_alloc(struct key *key)
+{
+	struct trusted_key_payload *p = NULL;
+	int ret;
+
+	ret = key_payload_reserve(key, sizeof(*p));
+	if (ret < 0)
+		return p;
+
+	p = kzalloc(sizeof(*p), GFP_KERNEL);
+
+	return p;
+}
+
+/*
+ * trusted_instantiate - create a new trusted key
+ *
+ * Unseal an existing trusted blob or, for a new key, get a
+ * random key, then seal and create a trusted key-type key,
+ * adding it to the specified keyring.
+ *
+ * On success, return 0. Otherwise return errno.
+ */
+static int trusted_instantiate(struct key *key,
+			       struct key_preparsed_payload *prep)
+{
+	struct trusted_key_payload *payload = NULL;
+	size_t datalen = prep->datalen;
+	char *datablob;
+	int ret = 0;
+	int key_cmd;
+	size_t key_len;
+
+	if (datalen <= 0 || datalen > 32767 || !prep->data)
+		return -EINVAL;
+
+	datablob = kmalloc(datalen + 1, GFP_KERNEL);
+	if (!datablob)
+		return -ENOMEM;
+	memcpy(datablob, prep->data, datalen);
+	datablob[datalen] = '\0';
+
+	payload = trusted_payload_alloc(key);
+	if (!payload) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	key_cmd = datablob_parse(datablob, payload);
+	if (key_cmd < 0) {
+		ret = key_cmd;
+		goto out;
+	}
+
+	dump_tee_payload(payload);
+
+	switch (key_cmd) {
+	case Opt_load:
+		ret = tee_key_unseal(payload);
+		dump_tee_payload(payload);
+		if (ret < 0)
+			dev_err(pvt_data.dev, "key_unseal failed (%d)\n", ret);
+		break;
+	case Opt_new:
+		key_len = payload->key_len;
+		ret = tee_get_random(payload->key, key_len);
+		if (ret != key_len) {
+			dev_err(pvt_data.dev, "key_create failed (%d)\n", ret);
+			goto out;
+		}
+
+		ret = tee_key_seal(payload);
+		if (ret < 0)
+			dev_err(pvt_data.dev, "key_seal failed (%d)\n", ret);
+		dump_tee_payload(payload);
+		break;
+	default:
+		ret = -EINVAL;
+		goto out;
+	}
+out:
+	kzfree(datablob);
+	if (!ret)
+		rcu_assign_keypointer(key, payload);
+	else
+		kzfree(payload);
+	return ret;
+}
+
+static int trusted_update(struct key *key, struct key_preparsed_payload *prep)
+{
+	dev_info(pvt_data.dev, "trusted key update method not supported\n");
+
+	return -EINVAL;
+}
+
+/*
+ * trusted_read - copy the sealed blob data to userspace in hex.
+ * On success, return to userspace the trusted key datablob size.
+ */
+static long trusted_read(const struct key *key, char __user *buffer,
+			 size_t buflen)
+{
+	const struct trusted_key_payload *p;
+	char *ascii_buf;
+	char *bufp;
+	int i;
+
+	p = dereference_key_locked(key);
+	if (!p)
+		return -EINVAL;
+
+	if (buffer && buflen >= 2 * p->blob_len) {
+		ascii_buf = kmalloc_array(2, p->blob_len, GFP_KERNEL);
+		if (!ascii_buf)
+			return -ENOMEM;
+
+		bufp = ascii_buf;
+		for (i = 0; i < p->blob_len; i++)
+			bufp = hex_byte_pack(bufp, p->blob[i]);
+		if (copy_to_user(buffer, ascii_buf, 2 * p->blob_len) != 0) {
+			kzfree(ascii_buf);
+			return -EFAULT;
+		}
+		kzfree(ascii_buf);
+	}
+	return 2 * p->blob_len;
+}
+
+/*
+ * trusted_destroy - clear and free the key's payload
+ */
+static void trusted_destroy(struct key *key)
+{
+	kzfree(key->payload.data[0]);
+}
+
+struct key_type key_type_tee_trusted = {
+	.name = "trusted",
+	.instantiate = trusted_instantiate,
+	.update = trusted_update,
+	.destroy = trusted_destroy,
+	.describe = user_describe,
+	.read = trusted_read,
+};
+EXPORT_SYMBOL_GPL(key_type_tee_trusted);
+
+static int optee_ctx_match(struct tee_ioctl_version_data *ver, const void *data)
+{
+	if (ver->impl_id == TEE_IMPL_ID_OPTEE)
+		return 1;
+	else
+		return 0;
+}
+
+static int trusted_key_probe(struct device *dev)
+{
+	struct tee_client_device *rng_device = to_tee_client_device(dev);
+	int ret = 0, err = -ENODEV;
+	struct tee_ioctl_open_session_arg sess_arg;
+
+	memset(&sess_arg, 0, sizeof(sess_arg));
+
+	/* Open context with TEE driver */
+	pvt_data.ctx = tee_client_open_context(NULL, optee_ctx_match, NULL,
+					       NULL);
+	if (IS_ERR(pvt_data.ctx))
+		return -ENODEV;
+
+	/* Open session with hwrng Trusted App */
+	memcpy(sess_arg.uuid, rng_device->id.uuid.b, TEE_IOCTL_UUID_LEN);
+	sess_arg.clnt_login = TEE_IOCTL_LOGIN_REE_KERNEL;
+	sess_arg.num_params = 0;
+
+	ret = tee_client_open_session(pvt_data.ctx, &sess_arg, NULL);
+	if ((ret < 0) || (sess_arg.ret != 0)) {
+		dev_err(dev, "tee_client_open_session failed, err: %x\n",
+			sess_arg.ret);
+		err = -EINVAL;
+		goto out_ctx;
+	}
+	pvt_data.session_id = sess_arg.session;
+
+	ret = register_key_type(&key_type_tee_trusted);
+	if (ret < 0)
+		goto out_sess;
+
+	pvt_data.dev = dev;
+
+	return 0;
+
+out_sess:
+	tee_client_close_session(pvt_data.ctx, pvt_data.session_id);
+out_ctx:
+	tee_client_close_context(pvt_data.ctx);
+
+	return err;
+}
+
+static int trusted_key_remove(struct device *dev)
+{
+	unregister_key_type(&key_type_tee_trusted);
+	tee_client_close_session(pvt_data.ctx, pvt_data.session_id);
+	tee_client_close_context(pvt_data.ctx);
+
+	return 0;
+}
+
+static const struct tee_client_device_id trusted_key_id_table[] = {
+	{UUID_INIT(0xf04a0fe7, 0x1f5d, 0x4b9b,
+		   0xab, 0xf7, 0x61, 0x9b, 0x85, 0xb4, 0xce, 0x8c)},
+	{}
+};
+
+MODULE_DEVICE_TABLE(tee, trusted_key_id_table);
+
+static struct tee_client_driver trusted_key_driver = {
+	.id_table	= trusted_key_id_table,
+	.driver		= {
+		.name		= DRIVER_NAME,
+		.bus		= &tee_bus_type,
+		.probe		= trusted_key_probe,
+		.remove		= trusted_key_remove,
+	},
+};
+
+static int __init init_tee_trusted(void)
+{
+	struct tpm_chip *chip;
+
+	/*
+	 * Check for TPM availability as that is default source for trusted
+	 * keys. If not present, then register driver for TEE based device
+	 * providing support for trusted keys.
+	 */
+	chip = tpm_default_chip();
+	if (chip)
+		return 0;
+
+	return driver_register(&trusted_key_driver.driver);
+}
+
+static void __exit cleanup_tee_trusted(void)
+{
+	driver_unregister(&trusted_key_driver.driver);
+}
+
+late_initcall(init_tee_trusted);
+module_exit(cleanup_tee_trusted);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Sumit Garg <sumit.garg@xxxxxxxxxx>");
+MODULE_DESCRIPTION("TEE based trusted keys");
-- 
2.7.4