linux/security/keys/trusted-keys/trusted_core.c
Ahmad Fatoum e9c5048c2d KEYS: trusted: Introduce support for NXP CAAM-based trusted keys
The Cryptographic Acceleration and Assurance Module (CAAM) is an IP core
built into many newer i.MX and QorIQ SoCs by NXP.

The CAAM does crypto acceleration, hardware number generation and
has a blob mechanism for encapsulation/decapsulation of sensitive material.

This blob mechanism depends on a device specific random 256-bit One Time
Programmable Master Key that is fused in each SoC at manufacturing
time. This key is unreadable and can only be used by the CAAM for AES
encryption/decryption of user data.

This makes it a suitable backend (source) for kernel trusted keys.

Previous commits generalized trusted keys to support multiple backends
and added an API to access the CAAM blob mechanism. Based on these,
provide the necessary glue to use the CAAM for trusted keys.

Reviewed-by: David Gstir <david@sigma-star.at>
Reviewed-by: Pankaj Gupta <pankaj.gupta@nxp.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Tested-by: Tim Harvey <tharvey@gateworks.com>
Tested-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com>
Tested-by: Pankaj Gupta <pankaj.gupta@nxp.com>
Tested-by: Michael Walle <michael@walle.cc> # on ls1028a (non-E and E)
Tested-by: John Ernberg <john.ernberg@actia.se> # iMX8QXP
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
2022-05-23 18:47:50 +03:00

398 lines
9.2 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2010 IBM Corporation
* Copyright (c) 2019-2021, Linaro Limited
*
* See Documentation/security/keys/trusted-encrypted.rst
*/
#include <keys/user-type.h>
#include <keys/trusted-type.h>
#include <keys/trusted_tee.h>
#include <keys/trusted_caam.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/random.h>
#include <linux/rcupdate.h>
#include <linux/slab.h>
#include <linux/static_call.h>
#include <linux/string.h>
#include <linux/uaccess.h>
static char *trusted_rng = "default";
module_param_named(rng, trusted_rng, charp, 0);
MODULE_PARM_DESC(rng, "Select trusted key RNG");
static char *trusted_key_source;
module_param_named(source, trusted_key_source, charp, 0);
MODULE_PARM_DESC(source, "Select trusted keys source (tpm, tee or caam)");
static const struct trusted_key_source trusted_key_sources[] = {
#if defined(CONFIG_TRUSTED_KEYS_TPM)
{ "tpm", &trusted_key_tpm_ops },
#endif
#if defined(CONFIG_TRUSTED_KEYS_TEE)
{ "tee", &trusted_key_tee_ops },
#endif
#if defined(CONFIG_TRUSTED_KEYS_CAAM)
{ "caam", &trusted_key_caam_ops },
#endif
};
DEFINE_STATIC_CALL_NULL(trusted_key_init, *trusted_key_sources[0].ops->init);
DEFINE_STATIC_CALL_NULL(trusted_key_seal, *trusted_key_sources[0].ops->seal);
DEFINE_STATIC_CALL_NULL(trusted_key_unseal,
*trusted_key_sources[0].ops->unseal);
DEFINE_STATIC_CALL_NULL(trusted_key_get_random,
*trusted_key_sources[0].ops->get_random);
DEFINE_STATIC_CALL_NULL(trusted_key_exit, *trusted_key_sources[0].ops->exit);
static unsigned char migratable;
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)
goto err;
p = kzalloc(sizeof(*p), GFP_KERNEL);
if (!p)
goto err;
p->migratable = migratable;
err:
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, *orig_datablob;
int ret = 0;
int key_cmd;
size_t key_len;
if (datalen <= 0 || datalen > 32767 || !prep->data)
return -EINVAL;
orig_datablob = 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 = static_call(trusted_key_unseal)(payload, datablob);
dump_payload(payload);
if (ret < 0)
pr_info("key_unseal failed (%d)\n", ret);
break;
case Opt_new:
key_len = payload->key_len;
ret = static_call(trusted_key_get_random)(payload->key,
key_len);
if (ret < 0)
goto out;
if (ret != key_len) {
pr_info("key_create failed (%d)\n", ret);
ret = -EIO;
goto out;
}
ret = static_call(trusted_key_seal)(payload, datablob);
if (ret < 0)
pr_info("key_seal failed (%d)\n", ret);
break;
default:
ret = -EINVAL;
}
out:
kfree_sensitive(orig_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, *orig_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;
orig_datablob = 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 = static_call(trusted_key_seal)(new_p, datablob);
if (ret < 0) {
pr_info("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(orig_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 kernel_get_random(unsigned char *key, size_t key_len)
{
return get_random_bytes_wait(key, key_len) ?: key_len;
}
static int __init init_trusted(void)
{
int (*get_random)(unsigned char *key, size_t key_len);
int i, ret = 0;
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;
/*
* We always support trusted.rng="kernel" and "default" as
* well as trusted.rng=$trusted.source if the trust source
* defines its own get_random callback.
*/
get_random = trusted_key_sources[i].ops->get_random;
if (trusted_rng && strcmp(trusted_rng, "default")) {
if (!strcmp(trusted_rng, "kernel")) {
get_random = kernel_get_random;
} else if (strcmp(trusted_rng, trusted_key_sources[i].name) ||
!get_random) {
pr_warn("Unsupported RNG. Supported: kernel");
if (get_random)
pr_cont(", %s", trusted_key_sources[i].name);
pr_cont(", default\n");
return -EINVAL;
}
}
if (!get_random)
get_random = kernel_get_random;
static_call_update(trusted_key_init,
trusted_key_sources[i].ops->init);
static_call_update(trusted_key_seal,
trusted_key_sources[i].ops->seal);
static_call_update(trusted_key_unseal,
trusted_key_sources[i].ops->unseal);
static_call_update(trusted_key_get_random,
get_random);
static_call_update(trusted_key_exit,
trusted_key_sources[i].ops->exit);
migratable = trusted_key_sources[i].ops->migratable;
ret = static_call(trusted_key_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)
{
static_call_cond(trusted_key_exit)();
}
late_initcall(init_trusted);
module_exit(cleanup_trusted);
MODULE_LICENSE("GPL");