Re: [op-tee] [PATCH v4 1/4] KEYS: trusted: Add generic trusted keys framework

On Mon, 1 Jun 2020 at 07:41, Jarkko Sakkinen jarkko.sakkinen@linux.intel.com wrote:

On Wed, May 06, 2020 at 03:10:14PM +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 trusked keys support in case platform doesn't posses a TPM device.

So this patch tries to add generic trusted keys framework where underlying implemtations 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 | 45 ++++ include/keys/trusted_tpm.h | 15 -- security/keys/trusted-keys/Makefile | 1 + security/keys/trusted-keys/trusted_common.c | 333 +++++++++++++++++++++++++++ security/keys/trusted-keys/trusted_tpm1.c | 335 +++++----------------------- 5 files changed, 437 insertions(+), 292 deletions(-) create mode 100644 security/keys/trusted-keys/trusted_common.c

diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h index a94c03a..5559010 100644 --- a/include/keys/trusted-type.h +++ b/include/keys/trusted-type.h @@ -40,6 +40,51 @@ 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;
  

• /* trusted key init */
  

• int (*init)(void);
  

• /* seal a trusted key */
  

• int (*seal)(struct trusted_key_payload *p, char *datablob);
  

• /* unseal a trusted key */
  

• int (*unseal)(struct trusted_key_payload *p, char *datablob);
  

• /* get random trusted key */
  

• int (*get_random)(unsigned char *key, size_t key_len);
  

• /* trusted key cleanup */
  

• void (*cleanup)(void);
  

+};

extern struct key_type key_type_trusted; +#if defined(CONFIG_TCG_TPM) +extern struct trusted_key_ops tpm_trusted_key_ops; +#endif

+#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..5753231 100644 --- a/include/keys/trusted_tpm.h +++ b/include/keys/trusted_tpm.h @@ -60,17 +60,6 @@ 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 +85,6 @@ 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..2b1085b 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_common.o trusted-y += trusted_tpm1.o trusted-y += trusted_tpm2.o diff --git a/security/keys/trusted-keys/trusted_common.c b/security/keys/trusted-keys/trusted_common.c new file mode 100644 index 0000000..9bfd081 --- /dev/null +++ b/security/keys/trusted-keys/trusted_common.c @@ -0,0 +1,333 @@ +// SPDX-License-Identifier: GPL-2.0-only +/*

• • Copyright (C) 2010 IBM Corporation
• • Copyright (c) 2019, Linaro Limited
• • Author:
• • David Safford safford@us.ibm.com
• • Added generic trusted key framework: Sumit Garg sumit.garg@linaro.org
• • See Documentation/security/keys/trusted-encrypted.rst
• */

+#include <keys/user-type.h> +#include <keys/trusted-type.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_tk_ops[] = { +#if defined(CONFIG_TCG_TPM)

• &tpm_trusted_key_ops,
  

+#endif +};

This, I think is wrong. You should have a compile time flag for TPM e.g. CONFIG_TRUSTED_TPM, not this dynamic mess.

The whole idea to have it dynamic was to have a common trusted keys module which could support both TPM and TEE implementation depending on hardware. I guess it may be useful in scenarios where a particular hardware supports a TPM chip while other doesn't but both need to run a common kernel image.

Please make the whole choice compile time, not run-time.

...

+static struct trusted_key_ops *tk_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 = tk_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 = tk_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 = tk_ops->get_random(payload->key, key_len);
  

•         if (ret != key_len) {
  

•                 pr_info("trusted_key: key_create failed (%d)\n", ret);
  

•                 goto out;
  

•         }
  

•         ret = tk_ops->seal(payload, datablob);
  

•         if (ret < 0)
  

•                 pr_info("trusted_key: key_seal failed (%d)\n", ret);
  

•         break;
  

• default:
  

•         ret = -EINVAL;
  

• }
  

+out:

• kzfree(datablob);
  

• if (!ret)
  

•         rcu_assign_keypointer(key, payload);
  

• else
  

•         kzfree(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);
  

• kzfree(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;
  

•         kzfree(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 = tk_ops->seal(new_p, datablob);
  

• if (ret < 0) {
  

•         pr_info("trusted_key: key_seal failed (%d)\n", ret);
  

•         kzfree(new_p);
  

•         goto out;
  

• }
  

• rcu_assign_keypointer(key, new_p);
  

• call_rcu(&p->rcu, trusted_rcu_free);
  

+out:

• kzfree(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) +{

• kzfree(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_tk_ops); i++) {
  

•         tk_ops = available_tk_ops[i];
  

•         if (!(tk_ops && tk_ops->init && tk_ops->seal &&
  

•               tk_ops->unseal && tk_ops->get_random))
  

•                 continue;
  

This check should not exist as there is no legit case for any of these callbacks missing. Please remove it.

Okay.

...

•         ret = tk_ops->init();
  

•         if (ret) {
  

•                 if (tk_ops->cleanup)
  

•                         tk_ops->cleanup();
  

Why is clean up called? What is "clean up"? Init should take care clean up its dirt if it fails. Please remove the calll to clean up from here.

Makes sense, will remove it.

-Sumit

/Jarkko