This is a revival of the previous patch set submitted by Richard Weinberger:
https://lore.kernel.org/linux-integrity/[email protected]/
After having been thoroughly reviewed by Jarkko, it would be great if this
could go into 6.10. :-)
v7 is here:
https://lore.kernel.org/keyrings/[email protected]/
v7 -> v8:
- Add Reviewed-by from Jarkko Sakkinen for patches #2 and #5
- Use kernel-doc for DCP blob format documentation instead of copy-pasting as
suggested by Jarkko Sakkinen
- Fix wording in docs for trusted.dcp_skip_zk_test kernel param
v6 -> v7:
- Add Reviewed-by from Jarkko Sakkinen for patches #1 and #3
- Improved commit messages
- Changed log level for non-trusted/secure mode check from error to warning
v5 -> v6:
- Cleaned up coding style and commit messages to make the whole series more
coherent as suggested by Jarkko Sakkinen
- Added Acked-By from Jarkko Sakkinen to patch #4 - thanks!
- Rebased against next-20240307
v4 -> v5:
- Make Kconfig for trust source check scalable as suggested by Jarkko Sakkinen
- Add Acked-By from Herbert Xu to patch #1 - thanks!
v3 -> v4:
- Split changes on MAINTAINERS and documentation into dedicated patches
- Use more concise wording in commit messages as suggested by Jarkko Sakkinen
v2 -> v3:
- Addressed review comments from Jarkko Sakkinen
v1 -> v2:
- Revive and rebase to latest version
- Include review comments from Ahmad Fatoum
The Data Co-Processor (DCP) is an IP core built into many NXP SoCs such
as i.mx6ull.
Similar to the CAAM engine used in more powerful SoCs, DCP can AES-
encrypt/decrypt user data using a unique, never-disclosed,
device-specific key. Unlike CAAM though, it cannot directly wrap and
unwrap blobs in hardware. As DCP offers only the bare minimum feature
set and a blob mechanism needs aid from software. A blob in this case
is a piece of sensitive data (e.g. a key) that is encrypted and
authenticated using the device-specific key so that unwrapping can only
be done on the hardware where the blob was wrapped.
This patch series adds a DCP based, trusted-key backend and is similar
in spirit to the one by Ahmad Fatoum [0] that does the same for CAAM.
It is of interest for similar use cases as the CAAM patch set, but for
lower end devices, where CAAM is not available.
Because constructing and parsing the blob has to happen in software,
we needed to decide on a blob format and chose the following:
struct dcp_blob_fmt {
__u8 fmt_version;
__u8 blob_key[AES_KEYSIZE_128];
__u8 nonce[AES_KEYSIZE_128];
__le32 payload_len;
__u8 payload[];
} __packed;
The `fmt_version` is currently 1.
The encrypted key is stored in the payload area. It is AES-128-GCM
encrypted using `blob_key` and `nonce`, GCM auth tag is attached at
the end of the payload (`payload_len` does not include the size of
the auth tag).
The `blob_key` itself is encrypted in AES-128-ECB mode by DCP using
the OTP or UNIQUE device key. A new `blob_key` and `nonce` are generated
randomly, when sealing/exporting the DCP blob.
This patchset was tested with dm-crypt on an i.MX6ULL board.
[0] https://lore.kernel.org/keyrings/[email protected]/
David Gstir (6):
crypto: mxs-dcp: Add support for hardware-bound keys
KEYS: trusted: improve scalability of trust source config
KEYS: trusted: Introduce NXP DCP-backed trusted keys
MAINTAINERS: add entry for DCP-based trusted keys
docs: document DCP-backed trusted keys kernel params
docs: trusted-encrypted: add DCP as new trust source
.../admin-guide/kernel-parameters.txt | 13 +
.../security/keys/trusted-encrypted.rst | 53 +++
MAINTAINERS | 9 +
drivers/crypto/mxs-dcp.c | 104 +++++-
include/keys/trusted_dcp.h | 11 +
include/soc/fsl/dcp.h | 20 ++
security/keys/trusted-keys/Kconfig | 18 +-
security/keys/trusted-keys/Makefile | 2 +
security/keys/trusted-keys/trusted_core.c | 6 +-
security/keys/trusted-keys/trusted_dcp.c | 332 ++++++++++++++++++
10 files changed, 554 insertions(+), 14 deletions(-)
create mode 100644 include/keys/trusted_dcp.h
create mode 100644 include/soc/fsl/dcp.h
create mode 100644 security/keys/trusted-keys/trusted_dcp.c
--
2.35.3
Document the kernel parameters trusted.dcp_use_otp_key
and trusted.dcp_skip_zk_test for DCP-backed trusted keys.
Co-developed-by: Richard Weinberger <[email protected]>
Signed-off-by: Richard Weinberger <[email protected]>
Co-developed-by: David Oberhollenzer <[email protected]>
Signed-off-by: David Oberhollenzer <[email protected]>
Signed-off-by: David Gstir <[email protected]>
Reviewed-by: Jarkko Sakkinen <[email protected]>
---
Documentation/admin-guide/kernel-parameters.txt | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 24c02c704049..3a59abf06039 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -6698,6 +6698,7 @@
- "tpm"
- "tee"
- "caam"
+ - "dcp"
If not specified then it defaults to iterating through
the trust source list starting with TPM and assigns the
first trust source as a backend which is initialized
@@ -6713,6 +6714,18 @@
If not specified, "default" is used. In this case,
the RNG's choice is left to each individual trust source.
+ trusted.dcp_use_otp_key
+ This is intended to be used in combination with
+ trusted.source=dcp and will select the DCP OTP key
+ instead of the DCP UNIQUE key blob encryption.
+
+ trusted.dcp_skip_zk_test
+ This is intended to be used in combination with
+ trusted.source=dcp and will disable the check if the
+ blob key is all zeros. This is helpful for situations where
+ having this key zero'ed is acceptable. E.g. in testing
+ scenarios.
+
tsc= Disable clocksource stability checks for TSC.
Format: <string>
[x86] reliable: mark tsc clocksource as reliable, this
--
2.35.3
DCP (Data Co-Processor) is the little brother of NXP's CAAM IP.
Beside of accelerated crypto operations, it also offers support for
hardware-bound keys. Using this feature it is possible to implement a blob
mechanism similar to what CAAM offers. Unlike on CAAM, constructing and
parsing the blob has to happen in software (i.e. the kernel).
The software-based blob format used by DCP trusted keys encrypts
the payload using AES-128-GCM with a freshly generated random key and nonce.
The random key itself is AES-128-ECB encrypted using the DCP unique
or OTP key.
The DCP trusted key blob format is:
/*
* struct dcp_blob_fmt - DCP BLOB format.
*
* @fmt_version: Format version, currently being %1
* @blob_key: Random AES 128 key which is used to encrypt @payload,
* @blob_key itself is encrypted with OTP or UNIQUE device key in
* AES-128-ECB mode by DCP.
* @nonce: Random nonce used for @payload encryption.
* @payload_len: Length of the plain text @payload.
* @payload: The payload itself, encrypted using AES-128-GCM and @blob_key,
* GCM auth tag of size AES_BLOCK_SIZE is attached at the end of it.
*
* The total size of a DCP BLOB is sizeof(struct dcp_blob_fmt) + @payload_len +
* AES_BLOCK_SIZE.
*/
struct dcp_blob_fmt {
__u8 fmt_version;
__u8 blob_key[AES_KEYSIZE_128];
__u8 nonce[AES_KEYSIZE_128];
__le32 payload_len;
__u8 payload[];
} __packed;
By default the unique key is used. It is also possible to use the
OTP key. While the unique key should be unique it is not documented how
this key is derived. Therefore selection the OTP key is supported as
well via the use_otp_key module parameter.
Co-developed-by: Richard Weinberger <[email protected]>
Signed-off-by: Richard Weinberger <[email protected]>
Co-developed-by: David Oberhollenzer <[email protected]>
Signed-off-by: David Oberhollenzer <[email protected]>
Signed-off-by: David Gstir <[email protected]>
Reviewed-by: Jarkko Sakkinen <[email protected]>
---
include/keys/trusted_dcp.h | 11 +
security/keys/trusted-keys/Kconfig | 8 +
security/keys/trusted-keys/Makefile | 2 +
security/keys/trusted-keys/trusted_core.c | 6 +-
security/keys/trusted-keys/trusted_dcp.c | 313 ++++++++++++++++++++++
5 files changed, 339 insertions(+), 1 deletion(-)
create mode 100644 include/keys/trusted_dcp.h
create mode 100644 security/keys/trusted-keys/trusted_dcp.c
diff --git a/include/keys/trusted_dcp.h b/include/keys/trusted_dcp.h
new file mode 100644
index 000000000000..9aaa42075b40
--- /dev/null
+++ b/include/keys/trusted_dcp.h
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2021 sigma star gmbh
+ */
+
+#ifndef TRUSTED_DCP_H
+#define TRUSTED_DCP_H
+
+extern struct trusted_key_ops dcp_trusted_key_ops;
+
+#endif
diff --git a/security/keys/trusted-keys/Kconfig b/security/keys/trusted-keys/Kconfig
index 553dc117f385..1fb8aa001995 100644
--- a/security/keys/trusted-keys/Kconfig
+++ b/security/keys/trusted-keys/Kconfig
@@ -39,6 +39,14 @@ config TRUSTED_KEYS_CAAM
Enable use of NXP's Cryptographic Accelerator and Assurance Module
(CAAM) as trusted key backend.
+config TRUSTED_KEYS_DCP
+ bool "DCP-based trusted keys"
+ depends on CRYPTO_DEV_MXS_DCP >= TRUSTED_KEYS
+ default y
+ select HAVE_TRUSTED_KEYS
+ help
+ Enable use of NXP's DCP (Data Co-Processor) as trusted key backend.
+
if !HAVE_TRUSTED_KEYS
comment "No trust source selected!"
endif
diff --git a/security/keys/trusted-keys/Makefile b/security/keys/trusted-keys/Makefile
index 735aa0bc08ef..f0f3b27f688b 100644
--- a/security/keys/trusted-keys/Makefile
+++ b/security/keys/trusted-keys/Makefile
@@ -14,3 +14,5 @@ trusted-$(CONFIG_TRUSTED_KEYS_TPM) += tpm2key.asn1.o
trusted-$(CONFIG_TRUSTED_KEYS_TEE) += trusted_tee.o
trusted-$(CONFIG_TRUSTED_KEYS_CAAM) += trusted_caam.o
+
+trusted-$(CONFIG_TRUSTED_KEYS_DCP) += trusted_dcp.o
diff --git a/security/keys/trusted-keys/trusted_core.c b/security/keys/trusted-keys/trusted_core.c
index fee1ab2c734d..5113aeae5628 100644
--- a/security/keys/trusted-keys/trusted_core.c
+++ b/security/keys/trusted-keys/trusted_core.c
@@ -10,6 +10,7 @@
#include <keys/trusted-type.h>
#include <keys/trusted_tee.h>
#include <keys/trusted_caam.h>
+#include <keys/trusted_dcp.h>
#include <keys/trusted_tpm.h>
#include <linux/capability.h>
#include <linux/err.h>
@@ -30,7 +31,7 @@ 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)");
+MODULE_PARM_DESC(source, "Select trusted keys source (tpm, tee, caam or dcp)");
static const struct trusted_key_source trusted_key_sources[] = {
#if defined(CONFIG_TRUSTED_KEYS_TPM)
@@ -42,6 +43,9 @@ static const struct trusted_key_source trusted_key_sources[] = {
#if defined(CONFIG_TRUSTED_KEYS_CAAM)
{ "caam", &trusted_key_caam_ops },
#endif
+#if defined(CONFIG_TRUSTED_KEYS_DCP)
+ { "dcp", &dcp_trusted_key_ops },
+#endif
};
DEFINE_STATIC_CALL_NULL(trusted_key_seal, *trusted_key_sources[0].ops->seal);
diff --git a/security/keys/trusted-keys/trusted_dcp.c b/security/keys/trusted-keys/trusted_dcp.c
new file mode 100644
index 000000000000..16c44aafeab3
--- /dev/null
+++ b/security/keys/trusted-keys/trusted_dcp.c
@@ -0,0 +1,313 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2021 sigma star gmbh
+ */
+
+#include <crypto/aead.h>
+#include <crypto/aes.h>
+#include <crypto/algapi.h>
+#include <crypto/gcm.h>
+#include <crypto/skcipher.h>
+#include <keys/trusted-type.h>
+#include <linux/key-type.h>
+#include <linux/module.h>
+#include <linux/printk.h>
+#include <linux/random.h>
+#include <linux/scatterlist.h>
+#include <soc/fsl/dcp.h>
+
+#define DCP_BLOB_VERSION 1
+#define DCP_BLOB_AUTHLEN 16
+
+/**
+ * struct dcp_blob_fmt - DCP BLOB format.
+ *
+ * @fmt_version: Format version, currently being %1.
+ * @blob_key: Random AES 128 key which is used to encrypt @payload,
+ * @blob_key itself is encrypted with OTP or UNIQUE device key in
+ * AES-128-ECB mode by DCP.
+ * @nonce: Random nonce used for @payload encryption.
+ * @payload_len: Length of the plain text @payload.
+ * @payload: The payload itself, encrypted using AES-128-GCM and @blob_key,
+ * GCM auth tag of size DCP_BLOB_AUTHLEN is attached at the end of it.
+ *
+ * The total size of a DCP BLOB is sizeof(struct dcp_blob_fmt) + @payload_len +
+ * DCP_BLOB_AUTHLEN.
+ */
+struct dcp_blob_fmt {
+ __u8 fmt_version;
+ __u8 blob_key[AES_KEYSIZE_128];
+ __u8 nonce[AES_KEYSIZE_128];
+ __le32 payload_len;
+ __u8 payload[];
+} __packed;
+
+static bool use_otp_key;
+module_param_named(dcp_use_otp_key, use_otp_key, bool, 0);
+MODULE_PARM_DESC(dcp_use_otp_key, "Use OTP instead of UNIQUE key for sealing");
+
+static bool skip_zk_test;
+module_param_named(dcp_skip_zk_test, skip_zk_test, bool, 0);
+MODULE_PARM_DESC(dcp_skip_zk_test, "Don't test whether device keys are zero'ed");
+
+static unsigned int calc_blob_len(unsigned int payload_len)
+{
+ return sizeof(struct dcp_blob_fmt) + payload_len + DCP_BLOB_AUTHLEN;
+}
+
+static int do_dcp_crypto(u8 *in, u8 *out, bool do_encrypt)
+{
+ struct skcipher_request *req = NULL;
+ struct scatterlist src_sg, dst_sg;
+ struct crypto_skcipher *tfm;
+ u8 paes_key[DCP_PAES_KEYSIZE];
+ DECLARE_CRYPTO_WAIT(wait);
+ int res = 0;
+
+ if (use_otp_key)
+ paes_key[0] = DCP_PAES_KEY_OTP;
+ else
+ paes_key[0] = DCP_PAES_KEY_UNIQUE;
+
+ tfm = crypto_alloc_skcipher("ecb-paes-dcp", CRYPTO_ALG_INTERNAL,
+ CRYPTO_ALG_INTERNAL);
+ if (IS_ERR(tfm)) {
+ res = PTR_ERR(tfm);
+ tfm = NULL;
+ goto out;
+ }
+
+ req = skcipher_request_alloc(tfm, GFP_NOFS);
+ if (!req) {
+ res = -ENOMEM;
+ goto out;
+ }
+
+ skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
+ CRYPTO_TFM_REQ_MAY_SLEEP,
+ crypto_req_done, &wait);
+ res = crypto_skcipher_setkey(tfm, paes_key, sizeof(paes_key));
+ if (res < 0)
+ goto out;
+
+ sg_init_one(&src_sg, in, AES_KEYSIZE_128);
+ sg_init_one(&dst_sg, out, AES_KEYSIZE_128);
+ skcipher_request_set_crypt(req, &src_sg, &dst_sg, AES_KEYSIZE_128,
+ NULL);
+
+ if (do_encrypt)
+ res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
+ else
+ res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
+
+out:
+ skcipher_request_free(req);
+ crypto_free_skcipher(tfm);
+
+ return res;
+}
+
+static int do_aead_crypto(u8 *in, u8 *out, size_t len, u8 *key, u8 *nonce,
+ bool do_encrypt)
+{
+ struct aead_request *aead_req = NULL;
+ struct scatterlist src_sg, dst_sg;
+ struct crypto_aead *aead;
+ int ret;
+
+ aead = crypto_alloc_aead("gcm(aes)", 0, CRYPTO_ALG_ASYNC);
+ if (IS_ERR(aead)) {
+ ret = PTR_ERR(aead);
+ goto out;
+ }
+
+ ret = crypto_aead_setauthsize(aead, DCP_BLOB_AUTHLEN);
+ if (ret < 0) {
+ pr_err("Can't set crypto auth tag len: %d\n", ret);
+ goto free_aead;
+ }
+
+ aead_req = aead_request_alloc(aead, GFP_KERNEL);
+ if (!aead_req) {
+ ret = -ENOMEM;
+ goto free_aead;
+ }
+
+ sg_init_one(&src_sg, in, len);
+ if (do_encrypt) {
+ /*
+ * If we encrypt our buffer has extra space for the auth tag.
+ */
+ sg_init_one(&dst_sg, out, len + DCP_BLOB_AUTHLEN);
+ } else {
+ sg_init_one(&dst_sg, out, len);
+ }
+
+ aead_request_set_crypt(aead_req, &src_sg, &dst_sg, len, nonce);
+ aead_request_set_callback(aead_req, CRYPTO_TFM_REQ_MAY_SLEEP, NULL,
+ NULL);
+ aead_request_set_ad(aead_req, 0);
+
+ if (crypto_aead_setkey(aead, key, AES_KEYSIZE_128)) {
+ pr_err("Can't set crypto AEAD key\n");
+ ret = -EINVAL;
+ goto free_req;
+ }
+
+ if (do_encrypt)
+ ret = crypto_aead_encrypt(aead_req);
+ else
+ ret = crypto_aead_decrypt(aead_req);
+
+free_req:
+ aead_request_free(aead_req);
+free_aead:
+ crypto_free_aead(aead);
+out:
+ return ret;
+}
+
+static int decrypt_blob_key(u8 *key)
+{
+ return do_dcp_crypto(key, key, false);
+}
+
+static int encrypt_blob_key(u8 *key)
+{
+ return do_dcp_crypto(key, key, true);
+}
+
+static int trusted_dcp_seal(struct trusted_key_payload *p, char *datablob)
+{
+ struct dcp_blob_fmt *b = (struct dcp_blob_fmt *)p->blob;
+ int blen, ret;
+
+ blen = calc_blob_len(p->key_len);
+ if (blen > MAX_BLOB_SIZE)
+ return -E2BIG;
+
+ b->fmt_version = DCP_BLOB_VERSION;
+ get_random_bytes(b->nonce, AES_KEYSIZE_128);
+ get_random_bytes(b->blob_key, AES_KEYSIZE_128);
+
+ ret = do_aead_crypto(p->key, b->payload, p->key_len, b->blob_key,
+ b->nonce, true);
+ if (ret) {
+ pr_err("Unable to encrypt blob payload: %i\n", ret);
+ return ret;
+ }
+
+ ret = encrypt_blob_key(b->blob_key);
+ if (ret) {
+ pr_err("Unable to encrypt blob key: %i\n", ret);
+ return ret;
+ }
+
+ b->payload_len = get_unaligned_le32(&p->key_len);
+ p->blob_len = blen;
+ return 0;
+}
+
+static int trusted_dcp_unseal(struct trusted_key_payload *p, char *datablob)
+{
+ struct dcp_blob_fmt *b = (struct dcp_blob_fmt *)p->blob;
+ int blen, ret;
+
+ if (b->fmt_version != DCP_BLOB_VERSION) {
+ pr_err("DCP blob has bad version: %i, expected %i\n",
+ b->fmt_version, DCP_BLOB_VERSION);
+ ret = -EINVAL;
+ goto out;
+ }
+
+ p->key_len = le32_to_cpu(b->payload_len);
+ blen = calc_blob_len(p->key_len);
+ if (blen != p->blob_len) {
+ pr_err("DCP blob has bad length: %i != %i\n", blen,
+ p->blob_len);
+ ret = -EINVAL;
+ goto out;
+ }
+
+ ret = decrypt_blob_key(b->blob_key);
+ if (ret) {
+ pr_err("Unable to decrypt blob key: %i\n", ret);
+ goto out;
+ }
+
+ ret = do_aead_crypto(b->payload, p->key, p->key_len + DCP_BLOB_AUTHLEN,
+ b->blob_key, b->nonce, false);
+ if (ret) {
+ pr_err("Unwrap of DCP payload failed: %i\n", ret);
+ goto out;
+ }
+
+ ret = 0;
+out:
+ return ret;
+}
+
+static int test_for_zero_key(void)
+{
+ /*
+ * Encrypting a plaintext of all 0x55 bytes will yield
+ * this ciphertext in case the DCP test key is used.
+ */
+ static const u8 bad[] = {0x9a, 0xda, 0xe0, 0x54, 0xf6, 0x3d, 0xfa, 0xff,
+ 0x5e, 0xa1, 0x8e, 0x45, 0xed, 0xf6, 0xea, 0x6f};
+ void *buf = NULL;
+ int ret = 0;
+
+ if (skip_zk_test)
+ goto out;
+
+ buf = kmalloc(AES_BLOCK_SIZE, GFP_KERNEL);
+ if (!buf) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ memset(buf, 0x55, AES_BLOCK_SIZE);
+
+ ret = do_dcp_crypto(buf, buf, true);
+ if (ret)
+ goto out;
+
+ if (memcmp(buf, bad, AES_BLOCK_SIZE) == 0) {
+ pr_warn("Device neither in secure nor trusted mode!\n");
+ ret = -EINVAL;
+ }
+out:
+ kfree(buf);
+ return ret;
+}
+
+static int trusted_dcp_init(void)
+{
+ int ret;
+
+ if (use_otp_key)
+ pr_info("Using DCP OTP key\n");
+
+ ret = test_for_zero_key();
+ if (ret) {
+ pr_warn("Test for zero'ed keys failed: %i\n", ret);
+
+ return -EINVAL;
+ }
+
+ return register_key_type(&key_type_trusted);
+}
+
+static void trusted_dcp_exit(void)
+{
+ unregister_key_type(&key_type_trusted);
+}
+
+struct trusted_key_ops dcp_trusted_key_ops = {
+ .exit = trusted_dcp_exit,
+ .init = trusted_dcp_init,
+ .seal = trusted_dcp_seal,
+ .unseal = trusted_dcp_unseal,
+ .migratable = 0,
+};
--
2.35.3
Update the documentation for trusted and encrypted KEYS with DCP as new
trust source:
- Describe security properties of DCP trust source
- Describe key usage
- Document blob format
Co-developed-by: Richard Weinberger <[email protected]>
Signed-off-by: Richard Weinberger <[email protected]>
Co-developed-by: David Oberhollenzer <[email protected]>
Signed-off-by: David Oberhollenzer <[email protected]>
Signed-off-by: David Gstir <[email protected]>
---
.../security/keys/trusted-encrypted.rst | 53 +++++++++++++++++++
security/keys/trusted-keys/trusted_dcp.c | 19 +++++++
2 files changed, 72 insertions(+)
diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst
index e989b9802f92..f4d7e162d5e4 100644
--- a/Documentation/security/keys/trusted-encrypted.rst
+++ b/Documentation/security/keys/trusted-encrypted.rst
@@ -42,6 +42,14 @@ safe.
randomly generated and fused into each SoC at manufacturing time.
Otherwise, a common fixed test key is used instead.
+ (4) DCP (Data Co-Processor: crypto accelerator of various i.MX SoCs)
+
+ Rooted to a one-time programmable key (OTP) that is generally burnt
+ in the on-chip fuses and is accessible to the DCP encryption engine only.
+ DCP provides two keys that can be used as root of trust: the OTP key
+ and the UNIQUE key. Default is to use the UNIQUE key, but selecting
+ the OTP key can be done via a module parameter (dcp_use_otp_key).
+
* Execution isolation
(1) TPM
@@ -57,6 +65,12 @@ safe.
Fixed set of operations running in isolated execution environment.
+ (4) DCP
+
+ Fixed set of cryptographic operations running in isolated execution
+ environment. Only basic blob key encryption is executed there.
+ The actual key sealing/unsealing is done on main processor/kernel space.
+
* Optional binding to platform integrity state
(1) TPM
@@ -79,6 +93,11 @@ safe.
Relies on the High Assurance Boot (HAB) mechanism of NXP SoCs
for platform integrity.
+ (4) DCP
+
+ Relies on Secure/Trusted boot process (called HAB by vendor) for
+ platform integrity.
+
* Interfaces and APIs
(1) TPM
@@ -94,6 +113,11 @@ safe.
Interface is specific to silicon vendor.
+ (4) DCP
+
+ Vendor-specific API that is implemented as part of the DCP crypto driver in
+ ``drivers/crypto/mxs-dcp.c``.
+
* Threat model
The strength and appropriateness of a particular trust source for a given
@@ -129,6 +153,13 @@ selected trust source:
CAAM HWRNG, enable CRYPTO_DEV_FSL_CAAM_RNG_API and ensure the device
is probed.
+ * DCP (Data Co-Processor: crypto accelerator of various i.MX SoCs)
+
+ The DCP hardware device itself does not provide a dedicated RNG interface,
+ so the kernel default RNG is used. SoCs with DCP like the i.MX6ULL do have
+ a dedicated hardware RNG that is independent from DCP which can be enabled
+ to back the kernel RNG.
+
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.
@@ -231,6 +262,19 @@ Usage::
CAAM-specific format. The key length for new keys is always in bytes.
Trusted Keys can be 32 - 128 bytes (256 - 1024 bits).
+Trusted Keys usage: DCP
+-----------------------
+
+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 this DCP key-blob implementation. The key length for new keys is
+always in bytes. Trusted Keys can be 32 - 128 bytes (256 - 1024 bits).
+
Encrypted Keys usage
--------------------
@@ -426,3 +470,12 @@ string length.
privkey is the binary representation of TPM2B_PUBLIC excluding the
initial TPM2B header which can be reconstructed from the ASN.1 octed
string length.
+
+DCP Blob Format
+---------------
+
+.. kernel-doc:: security/keys/trusted-keys/trusted_dcp.c
+ :doc: dcp blob format
+
+.. kernel-doc:: security/keys/trusted-keys/trusted_dcp.c
+ :identifiers: struct dcp_blob_fmt
diff --git a/security/keys/trusted-keys/trusted_dcp.c b/security/keys/trusted-keys/trusted_dcp.c
index 16c44aafeab3..b5f81a05be36 100644
--- a/security/keys/trusted-keys/trusted_dcp.c
+++ b/security/keys/trusted-keys/trusted_dcp.c
@@ -19,6 +19,25 @@
#define DCP_BLOB_VERSION 1
#define DCP_BLOB_AUTHLEN 16
+/**
+ * DOC: dcp blob format
+ *
+ * The Data Co-Processor (DCP) provides hardware-bound AES keys using its
+ * AES encryption engine only. It does not provide direct key sealing/unsealing.
+ * To make DCP hardware encryption keys usable as trust source, we define
+ * our own custom format that uses a hardware-bound key to secure the sealing
+ * key stored in the key blob.
+ *
+ * Whenever a new trusted key using DCP is generated, we generate a random 128-bit
+ * blob encryption key (BEK) and 128-bit nonce. The BEK and nonce are used to
+ * encrypt the trusted key payload using AES-128-GCM.
+ *
+ * The BEK itself is encrypted using the hardware-bound key using the DCP's AES
+ * encryption engine with AES-128-ECB. The encrypted BEK, generated nonce,
+ * BEK-encrypted payload and authentication tag make up the blob format together
+ * with a version number, payload length and authentication tag.
+ */
+
/**
* struct dcp_blob_fmt - DCP BLOB format.
*
--
2.35.3
On Wed, Apr 03, 2024 at 09:21:22AM +0200, David Gstir wrote:
> diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst
> index e989b9802f92..f4d7e162d5e4 100644
> --- a/Documentation/security/keys/trusted-encrypted.rst
> +++ b/Documentation/security/keys/trusted-encrypted.rst
> @@ -42,6 +42,14 @@ safe.
> randomly generated and fused into each SoC at manufacturing time.
> Otherwise, a common fixed test key is used instead.
>
> + (4) DCP (Data Co-Processor: crypto accelerator of various i.MX SoCs)
> +
> + Rooted to a one-time programmable key (OTP) that is generally burnt
> + in the on-chip fuses and is accessible to the DCP encryption engine only.
> + DCP provides two keys that can be used as root of trust: the OTP key
> + and the UNIQUE key. Default is to use the UNIQUE key, but selecting
> + the OTP key can be done via a module parameter (dcp_use_otp_key).
> +
> * Execution isolation
>
> (1) TPM
> @@ -57,6 +65,12 @@ safe.
>
> Fixed set of operations running in isolated execution environment.
>
> + (4) DCP
> +
> + Fixed set of cryptographic operations running in isolated execution
> + environment. Only basic blob key encryption is executed there.
> + The actual key sealing/unsealing is done on main processor/kernel space.
> +
> * Optional binding to platform integrity state
>
> (1) TPM
> @@ -79,6 +93,11 @@ safe.
> Relies on the High Assurance Boot (HAB) mechanism of NXP SoCs
> for platform integrity.
>
> + (4) DCP
> +
> + Relies on Secure/Trusted boot process (called HAB by vendor) for
> + platform integrity.
> +
> * Interfaces and APIs
>
> (1) TPM
> @@ -94,6 +113,11 @@ safe.
>
> Interface is specific to silicon vendor.
>
> + (4) DCP
> +
> + Vendor-specific API that is implemented as part of the DCP crypto driver in
> + ``drivers/crypto/mxs-dcp.c``.
> +
> * Threat model
>
> The strength and appropriateness of a particular trust source for a given
> @@ -129,6 +153,13 @@ selected trust source:
> CAAM HWRNG, enable CRYPTO_DEV_FSL_CAAM_RNG_API and ensure the device
> is probed.
>
> + * DCP (Data Co-Processor: crypto accelerator of various i.MX SoCs)
> +
> + The DCP hardware device itself does not provide a dedicated RNG interface,
> + so the kernel default RNG is used. SoCs with DCP like the i.MX6ULL do have
> + a dedicated hardware RNG that is independent from DCP which can be enabled
> + to back the kernel RNG.
> +
> 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.
>
> @@ -231,6 +262,19 @@ Usage::
> CAAM-specific format. The key length for new keys is always in bytes.
> Trusted Keys can be 32 - 128 bytes (256 - 1024 bits).
>
> +Trusted Keys usage: DCP
> +-----------------------
> +
> +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 this DCP key-blob implementation. The key length for new keys is
> +always in bytes. Trusted Keys can be 32 - 128 bytes (256 - 1024 bits).
> +
> Encrypted Keys usage
> --------------------
>
> @@ -426,3 +470,12 @@ string length.
> privkey is the binary representation of TPM2B_PUBLIC excluding the
> initial TPM2B header which can be reconstructed from the ASN.1 octed
> string length.
> +
> +DCP Blob Format
> +---------------
> +
> +.. kernel-doc:: security/keys/trusted-keys/trusted_dcp.c
> + :doc: dcp blob format
> +
> +.. kernel-doc:: security/keys/trusted-keys/trusted_dcp.c
> + :identifiers: struct dcp_blob_fmt
> diff --git a/security/keys/trusted-keys/trusted_dcp.c b/security/keys/trusted-keys/trusted_dcp.c
> index 16c44aafeab3..b5f81a05be36 100644
> --- a/security/keys/trusted-keys/trusted_dcp.c
> +++ b/security/keys/trusted-keys/trusted_dcp.c
> @@ -19,6 +19,25 @@
> #define DCP_BLOB_VERSION 1
> #define DCP_BLOB_AUTHLEN 16
>
> +/**
> + * DOC: dcp blob format
> + *
> + * The Data Co-Processor (DCP) provides hardware-bound AES keys using its
> + * AES encryption engine only. It does not provide direct key sealing/unsealing.
> + * To make DCP hardware encryption keys usable as trust source, we define
> + * our own custom format that uses a hardware-bound key to secure the sealing
> + * key stored in the key blob.
> + *
> + * Whenever a new trusted key using DCP is generated, we generate a random 128-bit
> + * blob encryption key (BEK) and 128-bit nonce. The BEK and nonce are used to
> + * encrypt the trusted key payload using AES-128-GCM.
> + *
> + * The BEK itself is encrypted using the hardware-bound key using the DCP's AES
> + * encryption engine with AES-128-ECB. The encrypted BEK, generated nonce,
> + * BEK-encrypted payload and authentication tag make up the blob format together
> + * with a version number, payload length and authentication tag.
> + */
> +
> /**
> * struct dcp_blob_fmt - DCP BLOB format.
> *
The doc LGTM, thanks!
Reviewed-by: Bagas Sanjaya <[email protected]>
--
An old man doll... just what I always wanted! - Clara
Hi David,
> -----Original Message-----
> From: David Gstir <[email protected]>
> Sent: Wednesday, April 3, 2024 12:51 PM
> To: Mimi Zohar <[email protected]>; James Bottomley
> <[email protected]>; Jarkko Sakkinen <[email protected]>; Herbert Xu
> <[email protected]>; David S. Miller <[email protected]>
> Cc: David Gstir <[email protected]>; Shawn Guo <[email protected]>;
> Jonathan Corbet <[email protected]>; Sascha Hauer
> <[email protected]>; Pengutronix Kernel Team
> <[email protected]>; Fabio Estevam <[email protected]>; dl-linux-
> imx <[email protected]>; Ahmad Fatoum <[email protected]>;
> sigma star Kernel Team <[email protected]>; David Howells
> <[email protected]>; Li Yang <[email protected]>; Paul Moore
> <[email protected]>; James Morris <[email protected]>; Serge E.
> Hallyn <[email protected]>; Paul E. McKenney <[email protected]>;
> Randy Dunlap <[email protected]>; Catalin Marinas
> <[email protected]>; Rafael J. Wysocki
> <[email protected]>; Tejun Heo <[email protected]>; Steven Rostedt
> (Google) <[email protected]>; [email protected]; linux-
> [email protected]; [email protected];
> [email protected]; [email protected]; linux-arm-
> [email protected]; [email protected]; linux-security-
> [email protected]; Richard Weinberger <[email protected]>; David
> Oberhollenzer <[email protected]>
> Subject: [EXT] [PATCH v8 3/6] KEYS: trusted: Introduce NXP DCP-backed
> trusted keys
>
> Caution: This is an external email. Please take care when clicking links or
> opening attachments. When in doubt, report the message using the 'Report
> this email' button
>
>
> DCP (Data Co-Processor) is the little brother of NXP's CAAM IP.
> Beside of accelerated crypto operations, it also offers support for hardware-
> bound keys. Using this feature it is possible to implement a blob
> mechanism similar to what CAAM offers. Unlike on CAAM, constructing and
> parsing the blob has to happen in software (i.e. the kernel).
>
> The software-based blob format used by DCP trusted keys encrypts the
> payload using AES-128-GCM with a freshly generated random key and
> nonce.
> The random key itself is AES-128-ECB encrypted using the DCP unique or
> OTP key.
>
> The DCP trusted key blob format is:
> /*
> * struct dcp_blob_fmt - DCP BLOB format.
> *
> * @fmt_version: Format version, currently being %1
> * @blob_key: Random AES 128 key which is used to encrypt @payload,
> * @blob_key itself is encrypted with OTP or UNIQUE device key in
> * AES-128-ECB mode by DCP.
> * @nonce: Random nonce used for @payload encryption.
> * @payload_len: Length of the plain text @payload.
> * @payload: The payload itself, encrypted using AES-128-GCM and
> @blob_key,
> * GCM auth tag of size AES_BLOCK_SIZE is attached at the end of it.
> *
> * The total size of a DCP BLOB is sizeof(struct dcp_blob_fmt) +
> @payload_len +
> * AES_BLOCK_SIZE.
> */
> struct dcp_blob_fmt {
> __u8 fmt_version;
> __u8 blob_key[AES_KEYSIZE_128];
> __u8 nonce[AES_KEYSIZE_128];
> __le32 payload_len;
> __u8 payload[];
> } __packed;
>
> By default the unique key is used. It is also possible to use the OTP key.
> While the unique key should be unique it is not documented how this key is
> derived. Therefore selection the OTP key is supported as well via the
> use_otp_key module parameter.
>
> Co-developed-by: Richard Weinberger <[email protected]>
> Signed-off-by: Richard Weinberger <[email protected]>
> Co-developed-by: David Oberhollenzer <[email protected]>
> Signed-off-by: David Oberhollenzer <[email protected]>
> Signed-off-by: David Gstir <[email protected]>
> Reviewed-by: Jarkko Sakkinen <[email protected]>
> ---
> include/keys/trusted_dcp.h | 11 +
> security/keys/trusted-keys/Kconfig | 8 +
> security/keys/trusted-keys/Makefile | 2 +
> security/keys/trusted-keys/trusted_core.c | 6 +-
> security/keys/trusted-keys/trusted_dcp.c | 313
> ++++++++++++++++++++++
> 5 files changed, 339 insertions(+), 1 deletion(-) create mode 100644
> include/keys/trusted_dcp.h create mode 100644 security/keys/trusted-
> keys/trusted_dcp.c
>
> diff --git a/include/keys/trusted_dcp.h b/include/keys/trusted_dcp.h new
> file mode 100644 index 000000000000..9aaa42075b40
> --- /dev/null
> +++ b/include/keys/trusted_dcp.h
> @@ -0,0 +1,11 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2021 sigma star gmbh
> + */
> +
> +#ifndef TRUSTED_DCP_H
> +#define TRUSTED_DCP_H
> +
> +extern struct trusted_key_ops dcp_trusted_key_ops;
> +
> +#endif
> diff --git a/security/keys/trusted-keys/Kconfig b/security/keys/trusted-
> keys/Kconfig
> index 553dc117f385..1fb8aa001995 100644
> --- a/security/keys/trusted-keys/Kconfig
> +++ b/security/keys/trusted-keys/Kconfig
> @@ -39,6 +39,14 @@ config TRUSTED_KEYS_CAAM
> Enable use of NXP's Cryptographic Accelerator and Assurance Module
> (CAAM) as trusted key backend.
>
> +config TRUSTED_KEYS_DCP
> + bool "DCP-based trusted keys"
> + depends on CRYPTO_DEV_MXS_DCP >= TRUSTED_KEYS
> + default y
> + select HAVE_TRUSTED_KEYS
> + help
> + Enable use of NXP's DCP (Data Co-Processor) as trusted key backend.
> +
> if !HAVE_TRUSTED_KEYS
> comment "No trust source selected!"
> endif
> diff --git a/security/keys/trusted-keys/Makefile b/security/keys/trusted-
> keys/Makefile
> index 735aa0bc08ef..f0f3b27f688b 100644
> --- a/security/keys/trusted-keys/Makefile
> +++ b/security/keys/trusted-keys/Makefile
> @@ -14,3 +14,5 @@ trusted-$(CONFIG_TRUSTED_KEYS_TPM) +=
> tpm2key.asn1.o
> trusted-$(CONFIG_TRUSTED_KEYS_TEE) += trusted_tee.o
>
> trusted-$(CONFIG_TRUSTED_KEYS_CAAM) += trusted_caam.o
> +
> +trusted-$(CONFIG_TRUSTED_KEYS_DCP) += trusted_dcp.o
> diff --git a/security/keys/trusted-keys/trusted_core.c
> b/security/keys/trusted-keys/trusted_core.c
> index fee1ab2c734d..5113aeae5628 100644
> --- a/security/keys/trusted-keys/trusted_core.c
> +++ b/security/keys/trusted-keys/trusted_core.c
> @@ -10,6 +10,7 @@
> #include <keys/trusted-type.h>
> #include <keys/trusted_tee.h>
> #include <keys/trusted_caam.h>
> +#include <keys/trusted_dcp.h>
> #include <keys/trusted_tpm.h>
> #include <linux/capability.h>
> #include <linux/err.h>
> @@ -30,7 +31,7 @@ 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)");
> +MODULE_PARM_DESC(source, "Select trusted keys source (tpm, tee, caam
> or
> +dcp)");
>
> static const struct trusted_key_source trusted_key_sources[] = { #if
> defined(CONFIG_TRUSTED_KEYS_TPM) @@ -42,6 +43,9 @@ static const
> struct trusted_key_source trusted_key_sources[] = { #if
> defined(CONFIG_TRUSTED_KEYS_CAAM)
> { "caam", &trusted_key_caam_ops }, #endif
> +#if defined(CONFIG_TRUSTED_KEYS_DCP)
> + { "dcp", &dcp_trusted_key_ops }, #endif
> };
>
> DEFINE_STATIC_CALL_NULL(trusted_key_seal, *trusted_key_sources[0].ops-
> >seal);
> diff --git a/security/keys/trusted-keys/trusted_dcp.c
> b/security/keys/trusted-keys/trusted_dcp.c
> new file mode 100644
> index 000000000000..16c44aafeab3
> --- /dev/null
> +++ b/security/keys/trusted-keys/trusted_dcp.c
> @@ -0,0 +1,313 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2021 sigma star gmbh
> + */
> +
> +#include <crypto/aead.h>
> +#include <crypto/aes.h>
> +#include <crypto/algapi.h>
> +#include <crypto/gcm.h>
> +#include <crypto/skcipher.h>
> +#include <keys/trusted-type.h>
> +#include <linux/key-type.h>
> +#include <linux/module.h>
> +#include <linux/printk.h>
> +#include <linux/random.h>
> +#include <linux/scatterlist.h>
> +#include <soc/fsl/dcp.h>
> +
> +#define DCP_BLOB_VERSION 1
> +#define DCP_BLOB_AUTHLEN 16
> +
> +/**
> + * struct dcp_blob_fmt - DCP BLOB format.
> + *
> + * @fmt_version: Format version, currently being %1.
> + * @blob_key: Random AES 128 key which is used to encrypt @payload,
> + * @blob_key itself is encrypted with OTP or UNIQUE device key in
> + * AES-128-ECB mode by DCP.
> + * @nonce: Random nonce used for @payload encryption.
> + * @payload_len: Length of the plain text @payload.
> + * @payload: The payload itself, encrypted using AES-128-GCM and
> @blob_key,
> + * GCM auth tag of size DCP_BLOB_AUTHLEN is attached at the end of
> it.
> + *
> + * The total size of a DCP BLOB is sizeof(struct dcp_blob_fmt) +
> @payload_len +
> + * DCP_BLOB_AUTHLEN.
> + */
> +struct dcp_blob_fmt {
> + __u8 fmt_version;
> + __u8 blob_key[AES_KEYSIZE_128];
> + __u8 nonce[AES_KEYSIZE_128];
> + __le32 payload_len;
> + __u8 payload[];
> +} __packed;
> +
> +static bool use_otp_key;
> +module_param_named(dcp_use_otp_key, use_otp_key, bool, 0);
> +MODULE_PARM_DESC(dcp_use_otp_key, "Use OTP instead of UNIQUE key
> for sealing");
> +
> +static bool skip_zk_test;
> +module_param_named(dcp_skip_zk_test, skip_zk_test, bool, 0);
> +MODULE_PARM_DESC(dcp_skip_zk_test, "Don't test whether device keys
> are zero'ed");
> +
> +static unsigned int calc_blob_len(unsigned int payload_len)
> +{
> + return sizeof(struct dcp_blob_fmt) + payload_len +
> DCP_BLOB_AUTHLEN;
> +}
> +
> +static int do_dcp_crypto(u8 *in, u8 *out, bool do_encrypt)
> +{
> + struct skcipher_request *req = NULL;
> + struct scatterlist src_sg, dst_sg;
> + struct crypto_skcipher *tfm;
> + u8 paes_key[DCP_PAES_KEYSIZE];
> + DECLARE_CRYPTO_WAIT(wait);
> + int res = 0;
> +
> + if (use_otp_key)
> + paes_key[0] = DCP_PAES_KEY_OTP;
> + else
> + paes_key[0] = DCP_PAES_KEY_UNIQUE;
> +
> + tfm = crypto_alloc_skcipher("ecb-paes-dcp", CRYPTO_ALG_INTERNAL,
> + CRYPTO_ALG_INTERNAL);
> + if (IS_ERR(tfm)) {
> + res = PTR_ERR(tfm);
> + tfm = NULL;
> + goto out;
> + }
> +
> + req = skcipher_request_alloc(tfm, GFP_NOFS);
> + if (!req) {
> + res = -ENOMEM;
> + goto out;
> + }
> +
> + skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG
> |
> + CRYPTO_TFM_REQ_MAY_SLEEP,
> + crypto_req_done, &wait);
> + res = crypto_skcipher_setkey(tfm, paes_key, sizeof(paes_key));
> + if (res < 0)
> + goto out;
> +
> + sg_init_one(&src_sg, in, AES_KEYSIZE_128);
> + sg_init_one(&dst_sg, out, AES_KEYSIZE_128);
> + skcipher_request_set_crypt(req, &src_sg, &dst_sg, AES_KEYSIZE_128,
> + NULL);
> +
> + if (do_encrypt)
> + res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
> + else
> + res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
> +
> +out:
> + skcipher_request_free(req);
> + crypto_free_skcipher(tfm);
> +
> + return res;
> +}
> +
> +static int do_aead_crypto(u8 *in, u8 *out, size_t len, u8 *key, u8 *nonce,
> + bool do_encrypt)
> +{
> + struct aead_request *aead_req = NULL;
> + struct scatterlist src_sg, dst_sg;
> + struct crypto_aead *aead;
> + int ret;
> +
> + aead = crypto_alloc_aead("gcm(aes)", 0, CRYPTO_ALG_ASYNC);
> + if (IS_ERR(aead)) {
> + ret = PTR_ERR(aead);
> + goto out;
> + }
> +
> + ret = crypto_aead_setauthsize(aead, DCP_BLOB_AUTHLEN);
> + if (ret < 0) {
> + pr_err("Can't set crypto auth tag len: %d\n", ret);
> + goto free_aead;
> + }
> +
> + aead_req = aead_request_alloc(aead, GFP_KERNEL);
> + if (!aead_req) {
> + ret = -ENOMEM;
> + goto free_aead;
> + }
> +
> + sg_init_one(&src_sg, in, len);
> + if (do_encrypt) {
> + /*
> + * If we encrypt our buffer has extra space for the auth tag.
> + */
> + sg_init_one(&dst_sg, out, len + DCP_BLOB_AUTHLEN);
> + } else {
> + sg_init_one(&dst_sg, out, len);
> + }
> +
> + aead_request_set_crypt(aead_req, &src_sg, &dst_sg, len, nonce);
> + aead_request_set_callback(aead_req, CRYPTO_TFM_REQ_MAY_SLEEP,
> NULL,
> + NULL);
> + aead_request_set_ad(aead_req, 0);
> +
> + if (crypto_aead_setkey(aead, key, AES_KEYSIZE_128)) {
> + pr_err("Can't set crypto AEAD key\n");
> + ret = -EINVAL;
> + goto free_req;
> + }
> +
> + if (do_encrypt)
> + ret = crypto_aead_encrypt(aead_req);
> + else
> + ret = crypto_aead_decrypt(aead_req);
> +
> +free_req:
> + aead_request_free(aead_req);
> +free_aead:
> + crypto_free_aead(aead);
> +out:
> + return ret;
> +}
> +
> +static int decrypt_blob_key(u8 *key)
> +{
> + return do_dcp_crypto(key, key, false);
> +}
> +
> +static int encrypt_blob_key(u8 *key)
> +{
> + return do_dcp_crypto(key, key, true);
> +}
> +
> +static int trusted_dcp_seal(struct trusted_key_payload *p, char *datablob)
> +{
> + struct dcp_blob_fmt *b = (struct dcp_blob_fmt *)p->blob;
> + int blen, ret;
> +
> + blen = calc_blob_len(p->key_len);
> + if (blen > MAX_BLOB_SIZE)
> + return -E2BIG;
> +
> + b->fmt_version = DCP_BLOB_VERSION;
> + get_random_bytes(b->nonce, AES_KEYSIZE_128);
> + get_random_bytes(b->blob_key, AES_KEYSIZE_128);
We can use HWRNG instead of using kernel RNG. Please refer drivers/char/hw_random/imx-rngc.c
> +
> + ret = do_aead_crypto(p->key, b->payload, p->key_len, b->blob_key,
> + b->nonce, true);
> + if (ret) {
> + pr_err("Unable to encrypt blob payload: %i\n", ret);
> + return ret;
> + }
> +
> + ret = encrypt_blob_key(b->blob_key);
> + if (ret) {
> + pr_err("Unable to encrypt blob key: %i\n", ret);
> + return ret;
> + }
> +
> + b->payload_len = get_unaligned_le32(&p->key_len);
> + p->blob_len = blen;
> + return 0;
> +}
> +
> +static int trusted_dcp_unseal(struct trusted_key_payload *p, char
> *datablob)
> +{
> + struct dcp_blob_fmt *b = (struct dcp_blob_fmt *)p->blob;
> + int blen, ret;
> +
> + if (b->fmt_version != DCP_BLOB_VERSION) {
> + pr_err("DCP blob has bad version: %i, expected %i\n",
> + b->fmt_version, DCP_BLOB_VERSION);
> + ret = -EINVAL;
> + goto out;
> + }
> +
> + p->key_len = le32_to_cpu(b->payload_len);
> + blen = calc_blob_len(p->key_len);
> + if (blen != p->blob_len) {
> + pr_err("DCP blob has bad length: %i != %i\n", blen,
> + p->blob_len);
> + ret = -EINVAL;
> + goto out;
> + }
> +
> + ret = decrypt_blob_key(b->blob_key);
> + if (ret) {
> + pr_err("Unable to decrypt blob key: %i\n", ret);
> + goto out;
> + }
> +
> + ret = do_aead_crypto(b->payload, p->key, p->key_len +
> DCP_BLOB_AUTHLEN,
> + b->blob_key, b->nonce, false);
> + if (ret) {
> + pr_err("Unwrap of DCP payload failed: %i\n", ret);
> + goto out;
> + }
> +
> + ret = 0;
> +out:
> + return ret;
> +}
> +
> +static int test_for_zero_key(void)
> +{
> + /*
> + * Encrypting a plaintext of all 0x55 bytes will yield
> + * this ciphertext in case the DCP test key is used.
> + */
> + static const u8 bad[] = {0x9a, 0xda, 0xe0, 0x54, 0xf6, 0x3d, 0xfa, 0xff,
> + 0x5e, 0xa1, 0x8e, 0x45, 0xed, 0xf6, 0xea, 0x6f};
> + void *buf = NULL;
> + int ret = 0;
> +
> + if (skip_zk_test)
> + goto out;
> +
> + buf = kmalloc(AES_BLOCK_SIZE, GFP_KERNEL);
> + if (!buf) {
> + ret = -ENOMEM;
> + goto out;
> + }
> +
> + memset(buf, 0x55, AES_BLOCK_SIZE);
> +
> + ret = do_dcp_crypto(buf, buf, true);
> + if (ret)
> + goto out;
> +
> + if (memcmp(buf, bad, AES_BLOCK_SIZE) == 0) {
> + pr_warn("Device neither in secure nor trusted mode!\n");
> + ret = -EINVAL;
> + }
> +out:
> + kfree(buf);
> + return ret;
> +}
> +
> +static int trusted_dcp_init(void)
> +{
> + int ret;
> +
> + if (use_otp_key)
> + pr_info("Using DCP OTP key\n");
> +
> + ret = test_for_zero_key();
> + if (ret) {
> + pr_warn("Test for zero'ed keys failed: %i\n", ret);
> +
> + return -EINVAL;
> + }
> +
> + return register_key_type(&key_type_trusted);
> +}
> +
> +static void trusted_dcp_exit(void)
> +{
> + unregister_key_type(&key_type_trusted);
> +}
> +
> +struct trusted_key_ops dcp_trusted_key_ops = {
> + .exit = trusted_dcp_exit,
> + .init = trusted_dcp_init,
> + .seal = trusted_dcp_seal,
> + .unseal = trusted_dcp_unseal,
> + .migratable = 0,
> +};
> --
> 2.35.3
>
Regards,
Kshitiz
Hello Kshitiz,
On 09.04.24 12:54, Kshitiz Varshney wrote:
> Hi David,
>> + b->fmt_version = DCP_BLOB_VERSION;
>> + get_random_bytes(b->nonce, AES_KEYSIZE_128);
>> + get_random_bytes(b->blob_key, AES_KEYSIZE_128);
>
> We can use HWRNG instead of using kernel RNG. Please refer drivers/char/hw_random/imx-rngc.c
imx-rngc can be enabled and used to seed the kernel entropy pool. Adding
direct calls into imx-rngc here only introduces duplicated code at no extra
benefit.
Cheers,
Ahmad
--
Pengutronix e.K. | |
Steuerwalder Str. 21 | http://www.pengutronix.de/ |
31137 Hildesheim, Germany | Phone: +49-5121-206917-0 |
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
Hi Ahmad,
> -----Original Message-----
> From: Ahmad Fatoum <[email protected]>
> Sent: Tuesday, April 9, 2024 10:58 PM
> To: Kshitiz Varshney <[email protected]>; David Gstir
> <[email protected]>; Mimi Zohar <[email protected]>; James
> Bottomley <[email protected]>; Jarkko Sakkinen <[email protected]>;
> Herbert Xu <[email protected]>; David S. Miller
> <[email protected]>
> Cc: [email protected]; Gaurav Jain <[email protected]>; Catalin
> Marinas <[email protected]>; David Howells
> <[email protected]>; [email protected]; Fabio Estevam
> <[email protected]>; Paul Moore <[email protected]>; Jonathan
> Corbet <[email protected]>; Richard Weinberger <[email protected]>; Rafael J.
> Wysocki <[email protected]>; James Morris <[email protected]>;
> dl-linux-imx <[email protected]>; Serge E. Hallyn <[email protected]>;
> Paul E. McKenney <[email protected]>; Sascha Hauer
> <[email protected]>; Pankaj Gupta <[email protected]>; sigma
> star Kernel Team <[email protected]>; Steven Rostedt (Google)
> <[email protected]>; David Oberhollenzer <david.oberhollenzer@sigma-
> star.at>; [email protected]; [email protected];
> Randy Dunlap <[email protected]>; [email protected]; Li
> Yang <[email protected]>; [email protected]; linux-
> [email protected]; Pengutronix Kernel Team <[email protected]>;
> Tejun Heo <[email protected]>; [email protected]; Shawn Guo
> <[email protected]>; Varun Sethi <[email protected]>
> Subject: Re: [EXT] [PATCH v8 3/6] KEYS: trusted: Introduce NXP DCP-backed
> trusted keys
>
> Caution: This is an external email. Please take care when clicking links or
> opening attachments. When in doubt, report the message using the 'Report
> this email' button
>
>
> Hello Kshitiz,
>
> On 09.04.24 12:54, Kshitiz Varshney wrote:
> > Hi David,
> >> + b->fmt_version = DCP_BLOB_VERSION;
> >> + get_random_bytes(b->nonce, AES_KEYSIZE_128);
> >> + get_random_bytes(b->blob_key, AES_KEYSIZE_128);
> >
> > We can use HWRNG instead of using kernel RNG. Please refer
> > drivers/char/hw_random/imx-rngc.c
>
> imx-rngc can be enabled and used to seed the kernel entropy pool. Adding
> direct calls into imx-rngc here only introduces duplicated code at no extra
> benefit.
>
> Cheers,
> Ahmad
>
> --
> Pengutronix e.K. | |
> Steuerwalder Str. 21 |
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> pengutronix.de%2F&data=05%7C02%7Ckshitiz.varshney%40nxp.com%7Ce9
> 97f259d34548ad1a9808dc58ba63a8%7C686ea1d3bc2b4c6fa92cd99c5c30
> 1635%7C0%7C0%7C638482804763047266%7CUnknown%7CTWFpbGZsb3
> d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0
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> F7%2BQeDLQhF8I%3D&reserved=0 |
> 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 |
> Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
Understood.
Regards,
Kshitiz