Series applies on top of current linux-tpmdd/master
v5 was here:
https://lore.kernel.org/linux-integrity/[email protected]/
Changelog was moved beneath each individual patch.
The Cryptographic Acceleration and Assurance Module (CAAM) is an IP core
built into many newer i.MX and QorIQ SoCs by NXP.
Its blob mechanism can AES encrypt/decrypt user data using a unique
never-disclosed device-specific key.
There has been multiple discussions on how to represent this within the kernel:
The Cryptographic Acceleration and Assurance Module (CAAM) is an IP core
built into many newer i.MX and QorIQ SoCs by NXP.
Its blob mechanism can AES encrypt/decrypt user data using a unique
never-disclosed device-specific key. There has been multiple
discussions on how to represent this within the kernel:
- [RFC] crypto: caam - add red blobifier
Steffen implemented[1] a PoC sysfs driver to start a discussion on how to
best integrate the blob mechanism.
Mimi suggested that it could be used to implement trusted keys.
Trusted keys back then were a TPM-only feature.
- security/keys/secure_key: Adds the secure key support based on CAAM.
Udit Agarwal added[2] a new "secure" key type with the CAAM as backend.
The key material stays within the kernel only.
Mimi and James agreed that this needs a generic interface, not specific
to CAAM. Mimi suggested trusted keys. Jan noted that this could serve as
basis for TEE-backed keys.
- [RFC] drivers: crypto: caam: key: Add caam_tk key type
Franck added[3] a new "caam_tk" key type based on Udit's work. This time
it uses CAAM "black blobs" instead of "red blobs", so key material stays
within the CAAM and isn't exposed to kernel in plaintext.
James voiced the opinion that there should be just one user-facing generic
wrap/unwrap key type with multiple possible handlers.
David suggested trusted keys.
- Introduce TEE based Trusted Keys support
Sumit reworked[4] trusted keys to support multiple possible backends with
one chosen at boot time and added a new TEE backend along with TPM.
This now sits in Jarkko's master branch to be sent out for v5.13
This patch series builds on top of Sumit's rework to have the CAAM as yet another
trusted key backend.
The CAAM bits are based on Steffen's initial patch from 2015. His work had been
used in the field for some years now, so I preferred not to deviate too much from it.
This series has been tested with dmcrypt[5] on an i.MX6Q/DL and an i.MX8M[6].
Looking forward to your feedback.
Cheers,
Ahmad
[1]: https://lore.kernel.org/linux-crypto/[email protected]/
[2]: https://lore.kernel.org/linux-integrity/[email protected]/
[3]: https://lore.kernel.org/lkml/[email protected]/
[4]: https://lore.kernel.org/lkml/[email protected]/
[5]: https://lore.kernel.org/linux-integrity/[email protected]/
[6]: https://lore.kernel.org/linux-integrity/DU2PR04MB8630D83FE9BBC0D782C4FAF595089@DU2PR04MB8630.eurprd04.prod.outlook.com/
---
To: Jarkko Sakkinen <[email protected]>
To: "Horia Geantă" <[email protected]>
To: Mimi Zohar <[email protected]>
To: Pankaj Gupta <[email protected]>
To: Herbert Xu <[email protected]>
To: "David S. Miller" <[email protected]>
To: James Bottomley <[email protected]>
Cc: David Howells <[email protected]>
Cc: James Morris <[email protected]>
Cc: "Serge E. Hallyn" <[email protected]>
Cc: Steffen Trumtrar <[email protected]>
Cc: Jan Luebbe <[email protected]>
Cc: David Gstir <[email protected]>
Cc: Eric Biggers <[email protected]>
Cc: Richard Weinberger <[email protected]>
Cc: Franck LENORMAND <[email protected]>
Cc: Sumit Garg <[email protected]>
Cc: Andreas Rammhold <[email protected]>
Cc: Tim Harvey <[email protected]>
Cc: Matthias Schiffer <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Ahmad Fatoum (4):
KEYS: trusted: allow use of TEE as backend without TCG_TPM support
KEYS: trusted: allow use of kernel RNG for key material
crypto: caam - add in-kernel interface for blob generator
KEYS: trusted: Introduce support for NXP CAAM-based trusted keys
.../admin-guide/kernel-parameters.txt | 11 ++
.../security/keys/trusted-encrypted.rst | 60 ++++++-
MAINTAINERS | 9 +
drivers/crypto/caam/Kconfig | 3 +
drivers/crypto/caam/Makefile | 1 +
drivers/crypto/caam/blob_gen.c | 160 ++++++++++++++++++
include/keys/trusted-type.h | 2 +-
include/keys/trusted_caam.h | 11 ++
include/soc/fsl/caam-blob.h | 79 +++++++++
security/keys/Kconfig | 18 +-
security/keys/trusted-keys/Kconfig | 38 +++++
security/keys/trusted-keys/Makefile | 10 +-
security/keys/trusted-keys/trusted_caam.c | 74 ++++++++
security/keys/trusted-keys/trusted_core.c | 45 ++++-
14 files changed, 492 insertions(+), 29 deletions(-)
create mode 100644 drivers/crypto/caam/blob_gen.c
create mode 100644 include/keys/trusted_caam.h
create mode 100644 include/soc/fsl/caam-blob.h
create mode 100644 security/keys/trusted-keys/Kconfig
create mode 100644 security/keys/trusted-keys/trusted_caam.c
--
2.30.2
The two existing trusted key sources don't make use of the kernel RNG,
but instead let the hardware doing the sealing/unsealing also
generate the random key material. However, both users and future
backends may want to place less trust into the quality of the trust
source's random number generator and instead reuse the kernel entropy
pool, which can be seeded from multiple entropy sources.
Make this possible by adding a new trusted.rng parameter,
that will force use of the kernel RNG. In its absence, it's up
to the trust source to decide, which random numbers to use,
maintaining the existing behavior.
Suggested-by: Jarkko Sakkinen <[email protected]>
Acked-by: Sumit Garg <[email protected]>
Acked-by: Pankaj Gupta <[email protected]>
Reviewed-by: David Gstir <[email protected]>
Reviewed-by: Pankaj Gupta <[email protected]>
Reviewed-by: Jarkko Sakkinen <[email protected]>
Signed-off-by: Ahmad Fatoum <[email protected]>
---
v5 -> v6:
- Squash with follow-up patch enabling trust sources to use
kernel RNG if they don't define their own .get_random
- Collected Jarkko's Reviewed-by
v4 -> v5:
- Changed trusted.kernel_rng bool option into a string trusted.rng option
(Jarkko)
- Typo fix in commit message (Jarkko)
v3 -> v4:
- Collected Acked-by's, Reviewed-by's and Tested-by
v2 -> v3:
- No change
v1 -> v2:
- Allow users to force use of kernel RNG (Jarkko)
To: James Bottomley <[email protected]>
To: Jarkko Sakkinen <[email protected]>
To: Mimi Zohar <[email protected]>
To: David Howells <[email protected]>
Cc: James Morris <[email protected]>
Cc: "Serge E. Hallyn" <[email protected]>
Cc: "Horia Geantă" <[email protected]>
Cc: Pankaj Gupta <[email protected]>
Cc: Herbert Xu <[email protected]>
Cc: "David S. Miller" <[email protected]>
Cc: Jan Luebbe <[email protected]>
Cc: Eric Biggers <[email protected]>
Cc: David Gstir <[email protected]>
Cc: Richard Weinberger <[email protected]>
Cc: Franck LENORMAND <[email protected]>
Cc: Sumit Garg <[email protected]>
Cc: Matthias Schiffer <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
---
.../admin-guide/kernel-parameters.txt | 10 ++++++
.../security/keys/trusted-encrypted.rst | 20 ++++++-----
include/keys/trusted-type.h | 2 +-
security/keys/trusted-keys/trusted_core.c | 35 ++++++++++++++++++-
4 files changed, 57 insertions(+), 10 deletions(-)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index f5a27f067db9..844c883ca9d8 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -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
diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst
index 80d5a5af62a1..99cf34d7c025 100644
--- a/Documentation/security/keys/trusted-encrypted.rst
+++ b/Documentation/security/keys/trusted-encrypted.rst
@@ -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
--------------
diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h
index d89fa2579ac0..4eb64548a74f 100644
--- a/include/keys/trusted-type.h
+++ b/include/keys/trusted-type.h
@@ -64,7 +64,7 @@ struct trusted_key_ops {
/* Unseal a key. */
int (*unseal)(struct trusted_key_payload *p, char *datablob);
- /* Get a randomized key. */
+ /* Optional: Get a randomized key. */
int (*get_random)(unsigned char *key, size_t key_len);
/* Exit key interface. */
diff --git a/security/keys/trusted-keys/trusted_core.c b/security/keys/trusted-keys/trusted_core.c
index 7cdbd16aed30..9235fb7d0ec9 100644
--- a/security/keys/trusted-keys/trusted_core.c
+++ b/security/keys/trusted-keys/trusted_core.c
@@ -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;
--
2.30.2