Add support for TEE based trusted keys where TEE provides the functionality to seal and unseal trusted keys using hardware unique key. Also, this is an alternative in case platform doesn't possess a TPM device.
This patch-set has been tested with OP-TEE based early TA which is already merged in upstream [1].
[1] https://github.com/OP-TEE/optee_os/commit/f86ab8e7e0de869dfa25ca05a37ee070d7...
Changes in v6: 1. Revert back to dynamic detection of trust source. 2. Drop author mention from trusted_core.c and trusted_tpm1.c files. 3. Rebased to latest tpmdd/master.
Changes in v5: 1. Drop dynamic detection of trust source and use compile time flags instead. 2. Rename trusted_common.c -> trusted_core.c. 3. Rename callback: cleanup() -> exit(). 4. Drop "tk" acronym. 5. Other misc. comments. 6. Added review tags for patch #3 and #4.
Changes in v4: 1. Pushed independent TEE features separately: - Part of recent TEE PR: https://lkml.org/lkml/2020/5/4/1062 2. Updated trusted-encrypted doc with TEE as a new trust source. 3. Rebased onto latest tpmdd/master.
Changes in v3: 1. Update patch #2 to support registration of multiple kernel pages. 2. Incoporate dependency patch #4 in this patch-set: https://patchwork.kernel.org/patch/11091435/
Changes in v2: 1. Add reviewed-by tags for patch #1 and #2. 2. Incorporate comments from Jens for patch #3. 3. Switch to use generic trusted keys framework.
Sumit Garg (4): KEYS: trusted: Add generic trusted keys framework KEYS: trusted: Introduce TEE based Trusted Keys doc: trusted-encrypted: updates with TEE as a new trust source MAINTAINERS: Add entry for TEE based Trusted Keys
Documentation/security/keys/trusted-encrypted.rst | 203 ++++++++++--- MAINTAINERS | 8 + include/keys/trusted-type.h | 42 +++ include/keys/trusted_tee.h | 55 ++++ include/keys/trusted_tpm.h | 17 +- security/keys/trusted-keys/Makefile | 2 + security/keys/trusted-keys/trusted_core.c | 325 +++++++++++++++++++++ security/keys/trusted-keys/trusted_tee.c | 278 ++++++++++++++++++ security/keys/trusted-keys/trusted_tpm1.c | 336 ++++------------------ 9 files changed, 939 insertions(+), 327 deletions(-) create mode 100644 include/keys/trusted_tee.h create mode 100644 security/keys/trusted-keys/trusted_core.c create mode 100644 security/keys/trusted-keys/trusted_tee.c
Current trusted keys framework is tightly coupled to use TPM device as an underlying implementation which makes it difficult for implementations like Trusted Execution Environment (TEE) etc. to provide trusted keys support in case platform doesn't posses a TPM device.
So this patch tries to add generic trusted keys framework where underlying implementations like TPM, TEE etc. could be easily plugged-in.
Suggested-by: Jarkko Sakkinen jarkko.sakkinen@linux.intel.com Signed-off-by: Sumit Garg sumit.garg@linaro.org --- include/keys/trusted-type.h | 42 ++++ include/keys/trusted_tpm.h | 17 +- security/keys/trusted-keys/Makefile | 1 + security/keys/trusted-keys/trusted_core.c | 321 ++++++++++++++++++++++++++++ security/keys/trusted-keys/trusted_tpm1.c | 336 +++++------------------------- 5 files changed, 422 insertions(+), 295 deletions(-) create mode 100644 security/keys/trusted-keys/trusted_core.c
diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h index a94c03a..edd635a 100644 --- a/include/keys/trusted-type.h +++ b/include/keys/trusted-type.h @@ -40,6 +40,48 @@ struct trusted_key_options { uint32_t policyhandle; };
+struct trusted_key_ops { + /* + * flag to indicate if trusted key implementation supports migration + * or not. + */ + unsigned char migratable; + + /* Initialize key interface. */ + int (*init)(void); + + /* Seal a key. */ + int (*seal)(struct trusted_key_payload *p, char *datablob); + + /* Unseal a key. */ + int (*unseal)(struct trusted_key_payload *p, char *datablob); + + /* Get a randomized key. */ + int (*get_random)(unsigned char *key, size_t key_len); + + /* Exit key interface. */ + void (*exit)(void); +}; + extern struct key_type key_type_trusted;
+#define TRUSTED_DEBUG 0 + +#if TRUSTED_DEBUG +static inline void dump_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); + pr_info("trusted_key: migratable %d\n", p->migratable); +} +#else +static inline void dump_payload(struct trusted_key_payload *p) +{ +} +#endif + #endif /* _KEYS_TRUSTED_TYPE_H */ diff --git a/include/keys/trusted_tpm.h b/include/keys/trusted_tpm.h index a56d8e1..fb3280a 100644 --- a/include/keys/trusted_tpm.h +++ b/include/keys/trusted_tpm.h @@ -16,6 +16,8 @@ #define LOAD32N(buffer, offset) (*(uint32_t *)&buffer[offset]) #define LOAD16(buffer, offset) (ntohs(*(uint16_t *)&buffer[offset]))
+extern struct trusted_key_ops tpm_trusted_key_ops; + struct osapsess { uint32_t handle; unsigned char secret[SHA1_DIGEST_SIZE]; @@ -60,17 +62,6 @@ static inline void dump_options(struct trusted_key_options *o) 16, 1, o->pcrinfo, o->pcrinfo_len, 0); }
-static inline void dump_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); - pr_info("trusted_key: migratable %d\n", p->migratable); -} - static inline void dump_sess(struct osapsess *s) { print_hex_dump(KERN_INFO, "trusted-key: handle ", DUMP_PREFIX_NONE, @@ -96,10 +87,6 @@ static inline void dump_options(struct trusted_key_options *o) { }
-static inline void dump_payload(struct trusted_key_payload *p) -{ -} - static inline void dump_sess(struct osapsess *s) { } diff --git a/security/keys/trusted-keys/Makefile b/security/keys/trusted-keys/Makefile index 7b73ceb..49e3bcf 100644 --- a/security/keys/trusted-keys/Makefile +++ b/security/keys/trusted-keys/Makefile @@ -4,5 +4,6 @@ #
obj-$(CONFIG_TRUSTED_KEYS) += trusted.o +trusted-y += trusted_core.o trusted-y += trusted_tpm1.o trusted-y += trusted_tpm2.o diff --git a/security/keys/trusted-keys/trusted_core.c b/security/keys/trusted-keys/trusted_core.c new file mode 100644 index 0000000..4ae3fb4 --- /dev/null +++ b/security/keys/trusted-keys/trusted_core.c @@ -0,0 +1,321 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2010 IBM Corporation + * Copyright (c) 2019-2020, Linaro Limited + * + * See Documentation/security/keys/trusted-encrypted.rst + */ + +#include <keys/user-type.h> +#include <keys/trusted-type.h> +#include <keys/trusted_tpm.h> +#include <linux/capability.h> +#include <linux/err.h> +#include <linux/init.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/uaccess.h> + +static struct trusted_key_ops *available_trusted_key_ops[] = { +#if defined(CONFIG_TCG_TPM) + &tpm_trusted_key_ops, +#endif +}; +static struct trusted_key_ops *trusted_key_ops; + +enum { + Opt_err, + Opt_new, Opt_load, Opt_update, +}; + +static const match_table_t key_tokens = { + {Opt_new, "new"}, + {Opt_load, "load"}, + {Opt_update, "update"}, + {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_update: + ret = Opt_update; + 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); + + p->migratable = trusted_key_ops->migratable; + + 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_payload(payload); + + switch (key_cmd) { + case Opt_load: + ret = trusted_key_ops->unseal(payload, datablob); + dump_payload(payload); + if (ret < 0) + pr_info("trusted_key: key_unseal failed (%d)\n", ret); + break; + case Opt_new: + key_len = payload->key_len; + ret = trusted_key_ops->get_random(payload->key, key_len); + if (ret != key_len) { + pr_info("trusted_key: key_create failed (%d)\n", ret); + goto out; + } + + ret = trusted_key_ops->seal(payload, datablob); + if (ret < 0) + pr_info("trusted_key: key_seal failed (%d)\n", ret); + break; + default: + ret = -EINVAL; + } +out: + kfree_sensitive(datablob); + if (!ret) + rcu_assign_keypointer(key, payload); + else + kfree_sensitive(payload); + return ret; +} + +static void trusted_rcu_free(struct rcu_head *rcu) +{ + struct trusted_key_payload *p; + + p = container_of(rcu, struct trusted_key_payload, rcu); + kfree_sensitive(p); +} + +/* + * trusted_update - reseal an existing key with new PCR values + */ +static int trusted_update(struct key *key, struct key_preparsed_payload *prep) +{ + struct trusted_key_payload *p; + struct trusted_key_payload *new_p; + size_t datalen = prep->datalen; + char *datablob; + int ret = 0; + + if (key_is_negative(key)) + return -ENOKEY; + p = key->payload.data[0]; + if (!p->migratable) + return -EPERM; + if (datalen <= 0 || datalen > 32767 || !prep->data) + return -EINVAL; + + datablob = kmalloc(datalen + 1, GFP_KERNEL); + if (!datablob) + return -ENOMEM; + + new_p = trusted_payload_alloc(key); + if (!new_p) { + ret = -ENOMEM; + goto out; + } + + memcpy(datablob, prep->data, datalen); + datablob[datalen] = '\0'; + ret = datablob_parse(datablob, new_p); + if (ret != Opt_update) { + ret = -EINVAL; + kfree_sensitive(new_p); + goto out; + } + + /* copy old key values, and reseal with new pcrs */ + new_p->migratable = p->migratable; + new_p->key_len = p->key_len; + memcpy(new_p->key, p->key, p->key_len); + dump_payload(p); + dump_payload(new_p); + + ret = trusted_key_ops->seal(new_p, datablob); + if (ret < 0) { + pr_info("trusted_key: key_seal failed (%d)\n", ret); + kfree_sensitive(new_p); + goto out; + } + + rcu_assign_keypointer(key, new_p); + call_rcu(&p->rcu, trusted_rcu_free); +out: + kfree_sensitive(datablob); + return ret; +} + +/* + * 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 *buffer, + size_t buflen) +{ + const struct trusted_key_payload *p; + char *bufp; + int i; + + p = dereference_key_locked(key); + if (!p) + return -EINVAL; + + if (buffer && buflen >= 2 * p->blob_len) { + bufp = buffer; + for (i = 0; i < p->blob_len; i++) + bufp = hex_byte_pack(bufp, p->blob[i]); + } + return 2 * p->blob_len; +} + +/* + * trusted_destroy - clear and free the key's payload + */ +static void trusted_destroy(struct key *key) +{ + kfree_sensitive(key->payload.data[0]); +} + +struct key_type key_type_trusted = { + .name = "trusted", + .instantiate = trusted_instantiate, + .update = trusted_update, + .destroy = trusted_destroy, + .describe = user_describe, + .read = trusted_read, +}; +EXPORT_SYMBOL_GPL(key_type_trusted); + +static int __init init_trusted(void) +{ + int i, ret = 0; + + for (i = 0; i < sizeof(available_trusted_key_ops); i++) { + trusted_key_ops = available_trusted_key_ops[i]; + + ret = trusted_key_ops->init(); + if (!ret) + break; + } + + /* + * encrypted_keys.ko depends on successful load of this module even if + * trusted key implementation is not found. + */ + if (ret == -ENODEV) + return 0; + + return ret; +} + +static void __exit cleanup_trusted(void) +{ + trusted_key_ops->exit(); +} + +late_initcall(init_trusted); +module_exit(cleanup_trusted); + +MODULE_LICENSE("GPL"); diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c index b9fe02e..1c5df77 100644 --- a/security/keys/trusted-keys/trusted_tpm1.c +++ b/security/keys/trusted-keys/trusted_tpm1.c @@ -1,29 +1,22 @@ // SPDX-License-Identifier: GPL-2.0-only /* * Copyright (C) 2010 IBM Corporation - * - * Author: - * David Safford safford@us.ibm.com + * Copyright (c) 2019-2020, Linaro Limited * * See Documentation/security/keys/trusted-encrypted.rst */
#include <crypto/hash_info.h> -#include <linux/uaccess.h> -#include <linux/module.h> #include <linux/init.h> #include <linux/slab.h> #include <linux/parser.h> #include <linux/string.h> #include <linux/err.h> -#include <keys/user-type.h> #include <keys/trusted-type.h> #include <linux/key-type.h> -#include <linux/rcupdate.h> #include <linux/crypto.h> #include <crypto/hash.h> #include <crypto/sha.h> -#include <linux/capability.h> #include <linux/tpm.h> #include <linux/tpm_command.h>
@@ -703,7 +696,6 @@ static int key_unseal(struct trusted_key_payload *p,
enum { Opt_err, - Opt_new, Opt_load, Opt_update, Opt_keyhandle, Opt_keyauth, Opt_blobauth, Opt_pcrinfo, Opt_pcrlock, Opt_migratable, Opt_hash, @@ -712,9 +704,6 @@ enum { };
static const match_table_t key_tokens = { - {Opt_new, "new"}, - {Opt_load, "load"}, - {Opt_update, "update"}, {Opt_keyhandle, "keyhandle=%s"}, {Opt_keyauth, "keyauth=%s"}, {Opt_blobauth, "blobauth=%s"}, @@ -841,71 +830,6 @@ static int getoptions(char *c, struct trusted_key_payload *pay, return 0; }
-/* - * datablob_parse - parse the keyctl data and fill in the - * payload and options structures - * - * On success returns 0, otherwise -EINVAL. - */ -static int datablob_parse(char *datablob, struct trusted_key_payload *p, - struct trusted_key_options *o) -{ - 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 = getoptions(datablob, p, o); - if (ret < 0) - return ret; - 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 = getoptions(datablob, p, o); - if (ret < 0) - return ret; - ret = Opt_load; - break; - case Opt_update: - /* all arguments are options */ - ret = getoptions(datablob, p, o); - if (ret < 0) - return ret; - ret = Opt_update; - break; - case Opt_err: - return -EINVAL; - break; - } - return ret; -} - static struct trusted_key_options *trusted_options_alloc(void) { struct trusted_key_options *options; @@ -926,248 +850,99 @@ static struct trusted_key_options *trusted_options_alloc(void) return options; }
-static struct trusted_key_payload *trusted_payload_alloc(struct key *key) +static int tpm_trusted_seal(struct trusted_key_payload *p, char *datablob) { - 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); - if (p) - p->migratable = 1; /* migratable by default */ - 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; struct trusted_key_options *options = NULL; - size_t datalen = prep->datalen; - char *datablob; int ret = 0; - int key_cmd; - size_t key_len; int tpm2;
tpm2 = tpm_is_tpm2(chip); if (tpm2 < 0) return tpm2;
- 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'; - options = trusted_options_alloc(); - if (!options) { - ret = -ENOMEM; - goto out; - } - payload = trusted_payload_alloc(key); - if (!payload) { - ret = -ENOMEM; - goto out; - } + if (!options) + return -ENOMEM;
- key_cmd = datablob_parse(datablob, payload, options); - if (key_cmd < 0) { - ret = key_cmd; + ret = getoptions(datablob, p, options); + if (ret < 0) goto out; - } + dump_options(options);
if (!options->keyhandle) { ret = -EINVAL; goto out; }
- dump_payload(payload); - dump_options(options); + if (tpm2) + ret = tpm2_seal_trusted(chip, p, options); + else + ret = key_seal(p, options); + if (ret < 0) { + pr_info("tpm_trusted_key: key_seal failed (%d)\n", ret); + goto out; + }
- switch (key_cmd) { - case Opt_load: - if (tpm2) - ret = tpm2_unseal_trusted(chip, payload, options); - else - ret = key_unseal(payload, options); - dump_payload(payload); - dump_options(options); - if (ret < 0) - pr_info("trusted_key: key_unseal failed (%d)\n", ret); - break; - case Opt_new: - key_len = payload->key_len; - ret = tpm_get_random(chip, payload->key, key_len); - if (ret != key_len) { - pr_info("trusted_key: key_create failed (%d)\n", ret); + if (options->pcrlock) { + ret = pcrlock(options->pcrlock); + if (ret < 0) { + pr_info("tpm_trusted_key: pcrlock failed (%d)\n", ret); goto out; } - if (tpm2) - ret = tpm2_seal_trusted(chip, payload, options); - else - ret = key_seal(payload, options); - if (ret < 0) - pr_info("trusted_key: key_seal failed (%d)\n", ret); - break; - default: - ret = -EINVAL; - goto out; } - if (!ret && options->pcrlock) - ret = pcrlock(options->pcrlock); out: - kfree_sensitive(datablob); kfree_sensitive(options); - if (!ret) - rcu_assign_keypointer(key, payload); - else - kfree_sensitive(payload); return ret; }
-static void trusted_rcu_free(struct rcu_head *rcu) -{ - struct trusted_key_payload *p; - - p = container_of(rcu, struct trusted_key_payload, rcu); - kfree_sensitive(p); -} - -/* - * trusted_update - reseal an existing key with new PCR values - */ -static int trusted_update(struct key *key, struct key_preparsed_payload *prep) +static int tpm_trusted_unseal(struct trusted_key_payload *p, char *datablob) { - struct trusted_key_payload *p; - struct trusted_key_payload *new_p; - struct trusted_key_options *new_o; - size_t datalen = prep->datalen; - char *datablob; + struct trusted_key_options *options = NULL; int ret = 0; + int tpm2;
- if (key_is_negative(key)) - return -ENOKEY; - p = key->payload.data[0]; - if (!p->migratable) - return -EPERM; - if (datalen <= 0 || datalen > 32767 || !prep->data) - return -EINVAL; + tpm2 = tpm_is_tpm2(chip); + if (tpm2 < 0) + return tpm2;
- datablob = kmalloc(datalen + 1, GFP_KERNEL); - if (!datablob) + options = trusted_options_alloc(); + if (!options) return -ENOMEM; - new_o = trusted_options_alloc(); - if (!new_o) { - ret = -ENOMEM; - goto out; - } - new_p = trusted_payload_alloc(key); - if (!new_p) { - ret = -ENOMEM; - goto out; - }
- memcpy(datablob, prep->data, datalen); - datablob[datalen] = '\0'; - ret = datablob_parse(datablob, new_p, new_o); - if (ret != Opt_update) { - ret = -EINVAL; - kfree_sensitive(new_p); + ret = getoptions(datablob, p, options); + if (ret < 0) goto out; - } + dump_options(options);
- if (!new_o->keyhandle) { + if (!options->keyhandle) { ret = -EINVAL; - kfree_sensitive(new_p); goto out; }
- /* copy old key values, and reseal with new pcrs */ - new_p->migratable = p->migratable; - new_p->key_len = p->key_len; - memcpy(new_p->key, p->key, p->key_len); - dump_payload(p); - dump_payload(new_p); + if (tpm2) + ret = tpm2_unseal_trusted(chip, p, options); + else + ret = key_unseal(p, options); + if (ret < 0) + pr_info("tpm_trusted_key: key_unseal failed (%d)\n", ret);
- ret = key_seal(new_p, new_o); - if (ret < 0) { - pr_info("trusted_key: key_seal failed (%d)\n", ret); - kfree_sensitive(new_p); - goto out; - } - if (new_o->pcrlock) { - ret = pcrlock(new_o->pcrlock); + if (options->pcrlock) { + ret = pcrlock(options->pcrlock); if (ret < 0) { - pr_info("trusted_key: pcrlock failed (%d)\n", ret); - kfree_sensitive(new_p); + pr_info("tpm_trusted_key: pcrlock failed (%d)\n", ret); goto out; } } - rcu_assign_keypointer(key, new_p); - call_rcu(&p->rcu, trusted_rcu_free); out: - kfree_sensitive(datablob); - kfree_sensitive(new_o); + kfree_sensitive(options); return ret; }
-/* - * 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 *buffer, - size_t buflen) -{ - const struct trusted_key_payload *p; - char *bufp; - int i; - - p = dereference_key_locked(key); - if (!p) - return -EINVAL; - - if (buffer && buflen >= 2 * p->blob_len) { - bufp = buffer; - for (i = 0; i < p->blob_len; i++) - bufp = hex_byte_pack(bufp, p->blob[i]); - } - return 2 * p->blob_len; -} - -/* - * trusted_destroy - clear and free the key's payload - */ -static void trusted_destroy(struct key *key) +static int tpm_trusted_get_random(unsigned char *key, size_t key_len) { - kfree_sensitive(key->payload.data[0]); + return tpm_get_random(chip, key, key_len); }
-struct key_type key_type_trusted = { - .name = "trusted", - .instantiate = trusted_instantiate, - .update = trusted_update, - .destroy = trusted_destroy, - .describe = user_describe, - .read = trusted_read, -}; - -EXPORT_SYMBOL_GPL(key_type_trusted); - static void trusted_shash_release(void) { if (hashalg) @@ -1182,14 +957,14 @@ static int __init trusted_shash_alloc(void)
hmacalg = crypto_alloc_shash(hmac_alg, 0, 0); if (IS_ERR(hmacalg)) { - pr_info("trusted_key: could not allocate crypto %s\n", + pr_info("tpm_trusted_key: could not allocate crypto %s\n", hmac_alg); return PTR_ERR(hmacalg); }
hashalg = crypto_alloc_shash(hash_alg, 0, 0); if (IS_ERR(hashalg)) { - pr_info("trusted_key: could not allocate crypto %s\n", + pr_info("tpm_trusted_key: could not allocate crypto %s\n", hash_alg); ret = PTR_ERR(hashalg); goto hashalg_fail; @@ -1217,16 +992,13 @@ static int __init init_digests(void) return 0; }
-static int __init init_trusted(void) +static int __init init_tpm_trusted(void) { int ret;
- /* encrypted_keys.ko depends on successful load of this module even if - * TPM is not used. - */ chip = tpm_default_chip(); if (!chip) - return 0; + return -ENODEV;
ret = init_digests(); if (ret < 0) @@ -1247,7 +1019,7 @@ static int __init init_trusted(void) return ret; }
-static void __exit cleanup_trusted(void) +static void __exit exit_tpm_trusted(void) { if (chip) { put_device(&chip->dev); @@ -1257,7 +1029,11 @@ static void __exit cleanup_trusted(void) } }
-late_initcall(init_trusted); -module_exit(cleanup_trusted); - -MODULE_LICENSE("GPL"); +struct trusted_key_ops tpm_trusted_key_ops = { + .migratable = 1, /* migratable by default */ + .init = init_tpm_trusted, + .seal = tpm_trusted_seal, + .unseal = tpm_trusted_unseal, + .get_random = tpm_trusted_get_random, + .exit = exit_tpm_trusted, +};
On Thu, Sep 17, 2020 at 07:16:35PM +0530, Sumit Garg wrote:
Current trusted keys framework is tightly coupled to use TPM device as an underlying implementation which makes it difficult for implementations like Trusted Execution Environment (TEE) etc. to provide trusted keys support in case platform doesn't posses a TPM device.
So this patch tries to add generic trusted keys framework where underlying implementations like TPM, TEE etc. could be easily plugged-in.
I would rephrase this a bit:
"Add a generic trusted keys framework where underlying implementations can be easily plugged in. Create struct trusted_key_ops to achieve this, which contains necessary functions of a backend."
I remember asking about this approach that what if there was just a header for trusted key functions and a compile time decision, which C file to include instead of ops struct. I don't remember if these was a conclusion on this or not.
E.g. lets say you have a device with TEE and TPM, should you be able to be use both at run-time? I might play along how this works now but somehow, in the commit message preferably, it should be conclude why one alternative is chosen over another.
/Jarkko
On Thu, Sep 17, 2020 at 07:21:49PM +0300, Jarkko Sakkinen wrote:
On Thu, Sep 17, 2020 at 07:16:35PM +0530, Sumit Garg wrote:
Current trusted keys framework is tightly coupled to use TPM device as an underlying implementation which makes it difficult for implementations like Trusted Execution Environment (TEE) etc. to provide trusted keys support in case platform doesn't posses a TPM device.
So this patch tries to add generic trusted keys framework where underlying implementations like TPM, TEE etc. could be easily plugged-in.
I would rephrase this a bit:
"Add a generic trusted keys framework where underlying implementations can be easily plugged in. Create struct trusted_key_ops to achieve this, which contains necessary functions of a backend."
I remember asking about this approach that what if there was just a header for trusted key functions and a compile time decision, which C file to include instead of ops struct. I don't remember if these was a conclusion on this or not.
E.g. lets say you have a device with TEE and TPM, should you be able to be use both at run-time? I might play along how this works now but somehow, in the commit message preferably, it should be conclude why one alternative is chosen over another.
We must somehow seal this discussion because the other changes are based on this decision.
I don't think tail of this patch set takes a long time spin. This is the main architectural decision.
/Jarkko
On Thu, 17 Sep 2020 at 21:55, Jarkko Sakkinen jarkko.sakkinen@linux.intel.com wrote:
On Thu, Sep 17, 2020 at 07:21:49PM +0300, Jarkko Sakkinen wrote:
On Thu, Sep 17, 2020 at 07:16:35PM +0530, Sumit Garg wrote:
Current trusted keys framework is tightly coupled to use TPM device as an underlying implementation which makes it difficult for implementations like Trusted Execution Environment (TEE) etc. to provide trusted keys support in case platform doesn't posses a TPM device.
So this patch tries to add generic trusted keys framework where underlying implementations like TPM, TEE etc. could be easily plugged-in.
I would rephrase this a bit:
"Add a generic trusted keys framework where underlying implementations can be easily plugged in. Create struct trusted_key_ops to achieve this, which contains necessary functions of a backend."
Okay, will use it instead.
I remember asking about this approach that what if there was just a header for trusted key functions and a compile time decision, which C file to include instead of ops struct. I don't remember if these was a conclusion on this or not.
This approach was implemented as part of v5 and we concluded here [1] to revert back to the dynamic approach as distro vendors won't like to make opinionated selection at compile time which could rather be achieved dynamically based on platform capability.
[1] https://www.spinics.net/lists/keyrings/msg08161.html
E.g. lets say you have a device with TEE and TPM, should you be able to be use both at run-time? I might play along how this works now but somehow, in the commit message preferably, it should be conclude why one alternative is chosen over another.
Okay, so how about adding a kernel module parameter which can enforce the user's preference about which trust source to use at runtime? And we should only check availability for that trust source if preference is provided otherwise by default we can traverse the trust sources list.
See following change, if this approach looks sane, I can include it in next version:
diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h index edd635a..a566451 100644 --- a/include/keys/trusted-type.h +++ b/include/keys/trusted-type.h @@ -63,6 +63,11 @@ struct trusted_key_ops { void (*exit)(void); };
+struct trusted_key_source { + char *name; + struct trusted_key_ops *ops; +}; + extern struct key_type key_type_trusted;
#define TRUSTED_DEBUG 0 diff --git a/security/keys/trusted-keys/trusted_core.c b/security/keys/trusted-keys/trusted_core.c index 83a6a15..74a3d80 100644 --- a/security/keys/trusted-keys/trusted_core.c +++ b/security/keys/trusted-keys/trusted_core.c @@ -21,12 +21,16 @@ #include <linux/string.h> #include <linux/uaccess.h>
-static struct trusted_key_ops *available_trusted_key_ops[] = { +static char *trusted_key_source; +module_param_named(source, trusted_key_source, charp, 0); +MODULE_PARM_DESC(source, "Select trusted keys source (tpm or tee)"); + +static struct trusted_key_source trusted_key_sources[] = { #if defined(CONFIG_TCG_TPM) - &tpm_trusted_key_ops, + { "tpm", &tpm_trusted_key_ops }, #endif #if defined(CONFIG_TEE) - &tee_trusted_key_ops, + { "tee", &tee_trusted_key_ops }, #endif }; static struct trusted_key_ops *trusted_key_ops; @@ -296,8 +300,13 @@ static int __init init_trusted(void) { int i, ret = 0;
- for (i = 0; i < sizeof(available_trusted_key_ops); i++) { - trusted_key_ops = available_trusted_key_ops[i]; + for (i = 0; i < ARRAY_SIZE(trusted_key_sources); i++) { + if (trusted_key_source && + strncmp(trusted_key_source, trusted_key_sources[i].name, + strlen(trusted_key_sources[i].name))) + continue; + + trusted_key_ops = trusted_key_sources[i].ops;
ret = trusted_key_ops->init(); if (!ret)
We must somehow seal this discussion because the other changes are based on this decision.
I don't think tail of this patch set takes a long time spin. This is the main architectural decision.
Agree.
-Sumit
/Jarkko
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.
Signed-off-by: Sumit Garg sumit.garg@linaro.org --- include/keys/trusted_tee.h | 55 ++++++ security/keys/trusted-keys/Makefile | 1 + security/keys/trusted-keys/trusted_core.c | 4 + security/keys/trusted-keys/trusted_tee.c | 278 ++++++++++++++++++++++++++++++ 4 files changed, 338 insertions(+) create mode 100644 include/keys/trusted_tee.h create mode 100644 security/keys/trusted-keys/trusted_tee.c
diff --git a/include/keys/trusted_tee.h b/include/keys/trusted_tee.h new file mode 100644 index 0000000..2e2bb15 --- /dev/null +++ b/include/keys/trusted_tee.h @@ -0,0 +1,55 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (C) 2019-2020 Linaro Ltd. + * + * Author: + * Sumit Garg sumit.garg@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 + */ +#define TA_CMD_GET_RANDOM 0x0 + +/* + * Seal trusted key using hardware unique key + * + * [in] memref[0] Plain key + * [out] memref[1] Sealed key datablob + */ +#define TA_CMD_SEAL 0x1 + +/* + * Unseal trusted key using hardware unique key + * + * [in] memref[0] Sealed key datablob + * [out] memref[1] Plain key + */ +#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; + struct tee_shm *shm_pool; +}; + +extern struct trusted_key_ops tee_trusted_key_ops; + +#endif diff --git a/security/keys/trusted-keys/Makefile b/security/keys/trusted-keys/Makefile index 49e3bcf..012dd78 100644 --- a/security/keys/trusted-keys/Makefile +++ b/security/keys/trusted-keys/Makefile @@ -7,3 +7,4 @@ obj-$(CONFIG_TRUSTED_KEYS) += trusted.o trusted-y += trusted_core.o trusted-y += trusted_tpm1.o trusted-y += trusted_tpm2.o +trusted-y += trusted_tee.o diff --git a/security/keys/trusted-keys/trusted_core.c b/security/keys/trusted-keys/trusted_core.c index 4ae3fb4..83a6a15 100644 --- a/security/keys/trusted-keys/trusted_core.c +++ b/security/keys/trusted-keys/trusted_core.c @@ -8,6 +8,7 @@
#include <keys/user-type.h> #include <keys/trusted-type.h> +#include <keys/trusted_tee.h> #include <keys/trusted_tpm.h> #include <linux/capability.h> #include <linux/err.h> @@ -24,6 +25,9 @@ static struct trusted_key_ops *available_trusted_key_ops[] = { #if defined(CONFIG_TCG_TPM) &tpm_trusted_key_ops, #endif +#if defined(CONFIG_TEE) + &tee_trusted_key_ops, +#endif }; static struct trusted_key_ops *trusted_key_ops;
diff --git a/security/keys/trusted-keys/trusted_tee.c b/security/keys/trusted-keys/trusted_tee.c new file mode 100644 index 0000000..b414d52 --- /dev/null +++ b/security/keys/trusted-keys/trusted_tee.c @@ -0,0 +1,278 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2019-2020 Linaro Ltd. + * + * Author: + * Sumit Garg sumit.garg@linaro.org + */ + +#include <linux/err.h> +#include <linux/key-type.h> +#include <linux/slab.h> +#include <linux/string.h> +#include <linux/uuid.h> + +#include <keys/trusted-type.h> +#include <keys/trusted_tee.h> + +static struct trusted_key_private pvt_data; + +/* + * Have the TEE seal(encrypt) the symmetric key + */ +static int tee_trusted_seal(struct trusted_key_payload *p, char *datablob) +{ + 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_trusted_unseal(struct trusted_key_payload *p, char *datablob) +{ + 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_trusted_get_random(unsigned char *key, size_t 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, "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; +} + +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)); + + pvt_data.ctx = tee_client_open_context(NULL, optee_ctx_match, NULL, + NULL); + if (IS_ERR(pvt_data.ctx)) + return -ENODEV; + + 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_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_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) +{ + return driver_register(&trusted_key_driver.driver); +} + +static void __exit exit_tee_trusted(void) +{ + driver_unregister(&trusted_key_driver.driver); +} + +struct trusted_key_ops tee_trusted_key_ops = { + .migratable = 0, /* non-migratable */ + .init = init_tee_trusted, + .seal = tee_trusted_seal, + .unseal = tee_trusted_unseal, + .get_random = tee_trusted_get_random, + .exit = exit_tee_trusted, +};
Update documentation for Trusted and Encrypted Keys with TEE as a new trust source. Following is brief description of updates:
- Add a section to demostrate a list of supported devices along with their security properties/guarantees. - Add a key generation section. - Updates for usage section including differences specific to a trust source.
Signed-off-by: Sumit Garg sumit.garg@linaro.org Reviewed-by: Jarkko Sakkinen jarkko.sakkinen@linux.intel.com --- Documentation/security/keys/trusted-encrypted.rst | 203 ++++++++++++++++++---- 1 file changed, 171 insertions(+), 32 deletions(-)
diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst index 9483a74..a355045 100644 --- a/Documentation/security/keys/trusted-encrypted.rst +++ b/Documentation/security/keys/trusted-encrypted.rst @@ -6,30 +6,161 @@ Trusted and Encrypted Keys are two new key types added to the existing kernel key ring service. Both of these new types are variable length symmetric keys, and in both cases all keys are created in the kernel, and user space sees, stores, and loads only encrypted blobs. Trusted Keys require the availability -of a Trusted Platform Module (TPM) chip for greater security, while Encrypted -Keys can be used on any system. All user level blobs, are displayed and loaded -in hex ascii for convenience, and are integrity verified. +of a Trust Source for greater security, while Encrypted Keys can be used on any +system. All user level blobs, are displayed and loaded in hex ascii for +convenience, and are integrity verified.
-Trusted Keys use a TPM both to generate and to seal the keys. Keys are sealed -under a 2048 bit RSA key in the TPM, and optionally sealed to specified PCR -(integrity measurement) values, and only unsealed by the TPM, if PCRs and blob -integrity verifications match. A loaded Trusted Key can be updated with new -(future) PCR values, so keys are easily migrated to new pcr values, such as -when the kernel and initramfs are updated. The same key can have many saved -blobs under different PCR values, so multiple boots are easily supported.
-TPM 1.2 -------- +Trust Source +============
-By default, trusted keys are sealed under the SRK, which has the default -authorization value (20 zeros). This can be set at takeownership time with the -trouser's utility: "tpm_takeownership -u -z". +Trust Source provides the source of security for the Trusted Keys, on which +basis Trusted Keys establishes a Trust model with its user. A Trust Source could +differ from one system to another depending on its security requirements. It +could be either an off-chip device or an on-chip device. Following section +demostrates a list of supported devices along with their security properties/ +guarantees:
-TPM 2.0 -------- + * Root of trust for storage
-The user must first create a storage key and make it persistent, so the key is -available after reboot. This can be done using the following commands. + (1) TPM (Trusted Platform Module: hardware device) + + Rooted to Storage Root Key (SRK) which never leaves the TPM that + provides crypto operation to establish root of trust for storage. + + (2) TEE (Trusted Execution Environment: OP-TEE based on Arm TrustZone) + + Rooted to Hardware Unique Key (HUK) which is generally burnt in on-chip + fuses and is accessible to TEE only. + + * Execution isolation + + (1) TPM + + Fixed set of operations running in isolated execution environment. + + (2) TEE + + Customizable set of operations running in isolated execution + environment verified via Secure/Trusted boot process. + + * Optional binding to platform integrity state + + (1) TPM + + Keys can be optionally sealed to specified PCR (integrity measurement) + values, and only unsealed by the TPM, if PCRs and blob integrity + verifications match. A loaded Trusted Key can be updated with new + (future) PCR values, so keys are easily migrated to new PCR values, + such as when the kernel and initramfs are updated. The same key can + have many saved blobs under different PCR values, so multiple boots are + easily supported. + + (2) TEE + + Relies on Secure/Trusted boot process for platform integrity. It can + be extended with TEE based measured boot process. + + * On-chip versus off-chip + + (1) TPM + + Off-chip device connected via serial bus (like I2C, SPI etc.) exposing + physical access which represents an attack surface that can be + mitigated via tamper detection. + + (2) TEE + + On-chip functionality, immune to this attack surface. + + * Memory attacks (DRAM based like attaching a bus monitor etc.) + + (1) TPM + + Immune to these attacks as it doesn’t make use of system DRAM. + + (2) TEE + + An implementation based on TrustZone protected DRAM is susceptible to + such attacks. In order to mitigate these attacks one needs to rely on + on-chip secure RAM to store secrets or have the entire TEE + implementation based on on-chip secure RAM. An alternative mitigation + would be to use encrypted DRAM. + + * Side-channel attacks (cache, memory, CPU or time based) + + (1) TPM + + Immune to side-channel attacks as its resources are isolated from the + main OS. + + (2) TEE + + A careful implementation is required to mitigate against these attacks + for resources which are shared (eg. shared memory) with the main OS. + Cache and CPU based side-channel attacks can be mitigated via + invalidating caches and CPU registers during context switch to and from + the secure world. + To mitigate against time based attacks, one needs to have time + invariant implementations (like crypto algorithms etc.). + + * Resistance to physical attacks (power analysis, electromagnetic emanation, + probes etc.) + + (1) TPM + + Provides limited protection utilizing tamper resistance. + + (2) TEE + + Provides no protection by itself, relies on the underlying platform for + features such as tamper resistance. + + +Key Generation +============== + +Trusted Keys +------------ + +New keys are created from trust source generated random numbers, and are +encrypted/decrypted using trust source storage root key. + + * TPM (hardware device) based RNG + + Strength of random numbers may vary from one device manufacturer to + another. + + * TEE (OP-TEE based on Arm TrustZone) based RNG + + RNG is customizable as per platform needs. It can either be direct output + from platform specific hardware RNG or a software based Fortuna CSPRNG + which can be seeded via multiple entropy sources. + +Encrypted Keys +-------------- + +Encrypted keys do not depend on a trust source, and are faster, as they use AES +for encryption/decryption. New keys are created from kernel generated random +numbers, and are encrypted/decrypted using a specified ‘master’ key. The +‘master’ key can either be a trusted-key or user-key type. The main disadvantage +of encrypted keys is that if they are not rooted in a trusted key, they are only +as secure as the user key encrypting them. The master user key should therefore +be loaded in as secure a way as possible, preferably early in boot. + + +Usage +===== + +Trusted Keys usage: TPM +----------------------- + +TPM 1.2: By default, trusted keys are sealed under the SRK, which has the +default authorization value (20 zeros). This can be set at takeownership time +with the TrouSerS utility: "tpm_takeownership -u -z". + +TPM 2.0: The user must first create a storage key and make it persistent, so the +key is available after reboot. This can be done using the following commands.
With the IBM TSS 2 stack::
@@ -79,14 +210,21 @@ TPM_STORED_DATA format. The key length for new keys are always in bytes. Trusted Keys can be 32 - 128 bytes (256 - 1024 bits), the upper limit is to fit within the 2048 bit SRK (RSA) keylength, with all necessary structure/padding.
-Encrypted keys do not depend on a TPM, and are faster, as they use AES for -encryption/decryption. New keys are created from kernel generated random -numbers, and are encrypted/decrypted using a specified 'master' key. The -'master' key can either be a trusted-key or user-key type. The main -disadvantage of encrypted keys is that if they are not rooted in a trusted key, -they are only as secure as the user key encrypting them. The master user key -should therefore be loaded in as secure a way as possible, preferably early in -boot. +Trusted Keys usage: TEE +----------------------- + +Usage:: + + keyctl add trusted name "new keylen" ring + keyctl add trusted name "load hex_blob" ring + keyctl print keyid + +"keyctl print" returns an ascii hex copy of the sealed key, which is in format +specific to TEE device implementation. The key length for new keys are always +in bytes. Trusted Keys can be 32 - 128 bytes (256 - 1024 bits). + +Encrypted Keys usage +--------------------
The decrypted portion of encrypted keys can contain either a simple symmetric key or a more complex structure. The format of the more complex structure is @@ -104,8 +242,8 @@ Where:: format:= 'default | ecryptfs | enc32' key-type:= 'trusted' | 'user'
- Examples of trusted and encrypted key usage: +--------------------------------------------
Create and save a trusted key named "kmk" of length 32 bytes.
@@ -151,7 +289,7 @@ Load a trusted key from the saved blob:: f1f8fff03ad0acb083725535636addb08d73dedb9832da198081e5deae84bfaf0409c22b e4a8aea2b607ec96931e6f4d4fe563ba
-Reseal a trusted key under new pcr values:: +Reseal (TPM specific) a trusted key under new PCR values::
$ keyctl update 268728824 "update pcrinfo=`cat pcr.blob`" $ keyctl print 268728824 @@ -165,11 +303,12 @@ Reseal a trusted key under new pcr values:: 7ef6a24defe4846104209bf0c3eced7fa1a672ed5b125fc9d8cd88b476a658a4434644ef df8ae9a178e9f83ba9f08d10fa47e4226b98b0702f06b3b8
+ The initial consumer of trusted keys is EVM, which at boot time needs a high -quality symmetric key for HMAC protection of file metadata. The use of a +quality symmetric key for HMAC protection of file metadata. The use of a trusted key provides strong guarantees that the EVM key has not been -compromised by a user level problem, and when sealed to specific boot PCR -values, protects against boot and offline attacks. Create and save an +compromised by a user level problem, and when sealed to a platform integrity +state, protects against boot and offline attacks. Create and save an encrypted key "evm" using the above trusted key "kmk":
option 1: omitting 'format'::
Add MAINTAINERS entry for TEE based Trusted Keys framework.
Signed-off-by: Sumit Garg sumit.garg@linaro.org Acked-by: Jarkko Sakkinen jarkko.sakkinen@linux.intel.com --- MAINTAINERS | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/MAINTAINERS b/MAINTAINERS index 0d0862b..0a913ba 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -9668,6 +9668,14 @@ F: include/keys/trusted-type.h F: include/keys/trusted_tpm.h F: security/keys/trusted-keys/
+KEYS-TRUSTED-TEE +M: Sumit Garg sumit.garg@linaro.org +L: linux-integrity@vger.kernel.org +L: keyrings@vger.kernel.org +S: Supported +F: include/keys/trusted_tee.h +F: security/keys/trusted-keys/trusted_tee.c + KEYS/KEYRINGS M: David Howells dhowells@redhat.com M: Jarkko Sakkinen jarkko.sakkinen@linux.intel.com
op-tee@lists.trustedfirmware.org
-
Jarkko Sakkinen -
Sumit Garg