@@ -5880,6 +5880,16 @@
first trust source as a backend which is initialized
successfully during iteration.
+ trusted.rng= [KEYS]
+ Format: <string>
+ The RNG used to generate key material for trusted keys.
+ Can be one of:
+ - "kernel"
+ - the same value as trusted.source: "tpm" or "tee"
+ - "default"
+ If not specified, "default" is used. In this case,
+ the RNG's choice is left to each individual trust source.
+
tsc= Disable clocksource stability checks for TSC.
Format: <string>
[x86] reliable: mark tsc clocksource as reliable, this
@@ -87,22 +87,26 @@ Key Generation
Trusted Keys
------------
-New keys are created from random numbers generated in the trust source. They
-are encrypted/decrypted using a child key in the storage key hierarchy.
-Encryption and decryption of the child key must be protected by a strong
-access control policy within the trust source.
+New keys are created from random numbers. They are encrypted/decrypted using
+a child key in the storage key hierarchy. Encryption and decryption of the
+child key must be protected by a strong access control policy within the
+trust source. The random number generator in use differs according to the
+selected trust source:
- * TPM (hardware device) based RNG
+ * TPM: hardware device based RNG
- Strength of random numbers may vary from one device manufacturer to
- another.
+ Keys are generated within the TPM. Strength of random numbers may vary
+ from one device manufacturer to another.
- * TEE (OP-TEE based on Arm TrustZone) based RNG
+ * 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.
+Users may override this by specifying ``trusted.rng=kernel`` on the kernel
+command-line to override the used RNG with the kernel's random number pool.
+
Encrypted Keys
--------------
@@ -16,12 +16,17 @@
#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 or tee)");
@@ -312,8 +317,14 @@ struct key_type key_type_trusted = {
};
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++) {
@@ -322,6 +333,28 @@ static int __init init_trusted(void)
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,
@@ -329,7 +362,7 @@ static int __init init_trusted(void)
static_call_update(trusted_key_unseal,
trusted_key_sources[i].ops->unseal);
static_call_update(trusted_key_get_random,
- trusted_key_sources[i].ops->get_random);
+ get_random);
static_call_update(trusted_key_exit,
trusted_key_sources[i].ops->exit);
migratable = trusted_key_sources[i].ops->migratable;