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.g...@linaro.org>
---
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.g...@linaro.org>
+ */
+
+#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.g...@linaro.org>
+ */
+
+#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(¶m, 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(¶m, 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(¶m, 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.g...@linaro.org>");
+MODULE_DESCRIPTION("TEE based trusted keys");
--
2.7.4
