This is a revival of the previous patch set submitted by Richard Weinberger:
https://lore.kernel.org/linux-integrity/[email protected]/
v1 -> v2:
- Revive and rebase to latest version
- Include review comments from Ahmad Fatoum
The Data CoProcessor (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 (3):
crypto: mxs-dcp: Add support for hardware provided keys
KEYS: trusted: Introduce support for NXP DCP-based trusted keys
doc: trusted-encrypted: add DCP as new trust source
.../admin-guide/kernel-parameters.txt | 13 +
.../security/keys/trusted-encrypted.rst | 85 +++++
MAINTAINERS | 9 +
drivers/crypto/mxs-dcp.c | 107 +++++-
include/keys/trusted_dcp.h | 13 +
include/soc/fsl/dcp.h | 19 ++
security/keys/trusted-keys/Kconfig | 9 +-
security/keys/trusted-keys/Makefile | 2 +
security/keys/trusted-keys/trusted_core.c | 6 +-
security/keys/trusted-keys/trusted_dcp.c | 313 ++++++++++++++++++
10 files changed, 563 insertions(+), 13 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
DCP is capable to performing AES with hardware-bound keys.
These keys are not stored in main memory and are therefore not directly
accessible by the operating system.
So instead of feeding the key into DCP, we need to place a
reference to such a key before initiating the crypto operation.
Keys are referenced by a one byte identifiers.
DCP supports 6 different keys: 4 slots in the secure memory area,
a one time programmable key which can be burnt via on-chip fuses
and an unique device key.
Using these keys is restricted to in-kernel users that use them as building
block for other crypto tools such as trusted keys. Allowing userspace
(e.g. via AF_ALG) to use these keys to crypt or decrypt data is a security
risk, because there is no access control mechanism.
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]>
---
drivers/crypto/mxs-dcp.c | 107 +++++++++++++++++++++++++++++++++++----
include/soc/fsl/dcp.h | 19 +++++++
2 files changed, 115 insertions(+), 11 deletions(-)
create mode 100644 include/soc/fsl/dcp.h
diff --git a/drivers/crypto/mxs-dcp.c b/drivers/crypto/mxs-dcp.c
index f6b7bce0e656..d525cb41f2ca 100644
--- a/drivers/crypto/mxs-dcp.c
+++ b/drivers/crypto/mxs-dcp.c
@@ -15,6 +15,7 @@
#include <linux/platform_device.h>
#include <linux/stmp_device.h>
#include <linux/clk.h>
+#include <soc/fsl/dcp.h>
#include <crypto/aes.h>
#include <crypto/sha1.h>
@@ -101,6 +102,7 @@ struct dcp_async_ctx {
struct crypto_skcipher *fallback;
unsigned int key_len;
uint8_t key[AES_KEYSIZE_128];
+ bool refkey;
};
struct dcp_aes_req_ctx {
@@ -155,6 +157,7 @@ static struct dcp *global_sdcp;
#define MXS_DCP_CONTROL0_HASH_TERM (1 << 13)
#define MXS_DCP_CONTROL0_HASH_INIT (1 << 12)
#define MXS_DCP_CONTROL0_PAYLOAD_KEY (1 << 11)
+#define MXS_DCP_CONTROL0_OTP_KEY (1 << 10)
#define MXS_DCP_CONTROL0_CIPHER_ENCRYPT (1 << 8)
#define MXS_DCP_CONTROL0_CIPHER_INIT (1 << 9)
#define MXS_DCP_CONTROL0_ENABLE_HASH (1 << 6)
@@ -168,6 +171,8 @@ static struct dcp *global_sdcp;
#define MXS_DCP_CONTROL1_CIPHER_MODE_ECB (0 << 4)
#define MXS_DCP_CONTROL1_CIPHER_SELECT_AES128 (0 << 0)
+#define MXS_DCP_CONTROL1_KEY_SELECT_SHIFT 8
+
static int mxs_dcp_start_dma(struct dcp_async_ctx *actx)
{
int dma_err;
@@ -224,13 +229,16 @@ static int mxs_dcp_run_aes(struct dcp_async_ctx *actx,
struct dcp *sdcp = global_sdcp;
struct dcp_dma_desc *desc = &sdcp->coh->desc[actx->chan];
struct dcp_aes_req_ctx *rctx = skcipher_request_ctx(req);
+ bool key_referenced = actx->refkey;
int ret;
- key_phys = dma_map_single(sdcp->dev, sdcp->coh->aes_key,
- 2 * AES_KEYSIZE_128, DMA_TO_DEVICE);
- ret = dma_mapping_error(sdcp->dev, key_phys);
- if (ret)
- return ret;
+ if (!key_referenced) {
+ key_phys = dma_map_single(sdcp->dev, sdcp->coh->aes_key,
+ 2 * AES_KEYSIZE_128, DMA_TO_DEVICE);
+ ret = dma_mapping_error(sdcp->dev, key_phys);
+ if (ret)
+ return ret;
+ }
src_phys = dma_map_single(sdcp->dev, sdcp->coh->aes_in_buf,
DCP_BUF_SZ, DMA_TO_DEVICE);
@@ -255,8 +263,13 @@ static int mxs_dcp_run_aes(struct dcp_async_ctx *actx,
MXS_DCP_CONTROL0_INTERRUPT |
MXS_DCP_CONTROL0_ENABLE_CIPHER;
- /* Payload contains the key. */
- desc->control0 |= MXS_DCP_CONTROL0_PAYLOAD_KEY;
+ if (key_referenced) {
+ /* Set OTP key bit to select the key via KEY_SELECT. */
+ desc->control0 |= MXS_DCP_CONTROL0_OTP_KEY;
+ } else {
+ /* Payload contains the key. */
+ desc->control0 |= MXS_DCP_CONTROL0_PAYLOAD_KEY;
+ }
if (rctx->enc)
desc->control0 |= MXS_DCP_CONTROL0_CIPHER_ENCRYPT;
@@ -270,6 +283,9 @@ static int mxs_dcp_run_aes(struct dcp_async_ctx *actx,
else
desc->control1 |= MXS_DCP_CONTROL1_CIPHER_MODE_CBC;
+ if (key_referenced)
+ desc->control1 |= sdcp->coh->aes_key[0] << MXS_DCP_CONTROL1_KEY_SELECT_SHIFT;
+
desc->next_cmd_addr = 0;
desc->source = src_phys;
desc->destination = dst_phys;
@@ -284,9 +300,10 @@ static int mxs_dcp_run_aes(struct dcp_async_ctx *actx,
err_dst:
dma_unmap_single(sdcp->dev, src_phys, DCP_BUF_SZ, DMA_TO_DEVICE);
err_src:
- dma_unmap_single(sdcp->dev, key_phys, 2 * AES_KEYSIZE_128,
- DMA_TO_DEVICE);
-
+ if (!key_referenced) {
+ dma_unmap_single(sdcp->dev, key_phys, 2 * AES_KEYSIZE_128,
+ DMA_TO_DEVICE);
+ }
return ret;
}
@@ -453,7 +470,7 @@ static int mxs_dcp_aes_enqueue(struct skcipher_request *req, int enc, int ecb)
struct dcp_aes_req_ctx *rctx = skcipher_request_ctx(req);
int ret;
- if (unlikely(actx->key_len != AES_KEYSIZE_128))
+ if (unlikely(actx->key_len != AES_KEYSIZE_128 && !actx->refkey))
return mxs_dcp_block_fallback(req, enc);
rctx->enc = enc;
@@ -500,6 +517,7 @@ static int mxs_dcp_aes_setkey(struct crypto_skcipher *tfm, const u8 *key,
* there can still be an operation in progress.
*/
actx->key_len = len;
+ actx->refkey = false;
if (len == AES_KEYSIZE_128) {
memcpy(actx->key, key, len);
return 0;
@@ -516,6 +534,33 @@ static int mxs_dcp_aes_setkey(struct crypto_skcipher *tfm, const u8 *key,
return crypto_skcipher_setkey(actx->fallback, key, len);
}
+static int mxs_dcp_aes_setrefkey(struct crypto_skcipher *tfm, const u8 *key,
+ unsigned int len)
+{
+ struct dcp_async_ctx *actx = crypto_skcipher_ctx(tfm);
+
+ if (len != DCP_PAES_KEYSIZE)
+ return -EINVAL;
+
+ switch (key[0]) {
+ case DCP_PAES_KEY_SLOT0:
+ case DCP_PAES_KEY_SLOT1:
+ case DCP_PAES_KEY_SLOT2:
+ case DCP_PAES_KEY_SLOT3:
+ case DCP_PAES_KEY_UNIQUE:
+ case DCP_PAES_KEY_OTP:
+ memcpy(actx->key, key, len);
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ actx->key_len = len;
+ actx->refkey = true;
+
+ return 0;
+}
+
static int mxs_dcp_aes_fallback_init_tfm(struct crypto_skcipher *tfm)
{
const char *name = crypto_tfm_alg_name(crypto_skcipher_tfm(tfm));
@@ -539,6 +584,13 @@ static void mxs_dcp_aes_fallback_exit_tfm(struct crypto_skcipher *tfm)
crypto_free_skcipher(actx->fallback);
}
+static int mxs_dcp_paes_init_tfm(struct crypto_skcipher *tfm)
+{
+ crypto_skcipher_set_reqsize(tfm, sizeof(struct dcp_aes_req_ctx));
+
+ return 0;
+}
+
/*
* Hashing (SHA1/SHA256)
*/
@@ -889,6 +941,39 @@ static struct skcipher_alg dcp_aes_algs[] = {
.ivsize = AES_BLOCK_SIZE,
.init = mxs_dcp_aes_fallback_init_tfm,
.exit = mxs_dcp_aes_fallback_exit_tfm,
+ }, {
+ .base.cra_name = "ecb(paes)",
+ .base.cra_driver_name = "ecb-paes-dcp",
+ .base.cra_priority = 401,
+ .base.cra_alignmask = 15,
+ .base.cra_flags = CRYPTO_ALG_ASYNC | CRYPTO_ALG_INTERNAL,
+ .base.cra_blocksize = AES_BLOCK_SIZE,
+ .base.cra_ctxsize = sizeof(struct dcp_async_ctx),
+ .base.cra_module = THIS_MODULE,
+
+ .min_keysize = DCP_PAES_KEYSIZE,
+ .max_keysize = DCP_PAES_KEYSIZE,
+ .setkey = mxs_dcp_aes_setrefkey,
+ .encrypt = mxs_dcp_aes_ecb_encrypt,
+ .decrypt = mxs_dcp_aes_ecb_decrypt,
+ .init = mxs_dcp_paes_init_tfm,
+ }, {
+ .base.cra_name = "cbc(paes)",
+ .base.cra_driver_name = "cbc-paes-dcp",
+ .base.cra_priority = 401,
+ .base.cra_alignmask = 15,
+ .base.cra_flags = CRYPTO_ALG_ASYNC | CRYPTO_ALG_INTERNAL,
+ .base.cra_blocksize = AES_BLOCK_SIZE,
+ .base.cra_ctxsize = sizeof(struct dcp_async_ctx),
+ .base.cra_module = THIS_MODULE,
+
+ .min_keysize = DCP_PAES_KEYSIZE,
+ .max_keysize = DCP_PAES_KEYSIZE,
+ .setkey = mxs_dcp_aes_setrefkey,
+ .encrypt = mxs_dcp_aes_cbc_encrypt,
+ .decrypt = mxs_dcp_aes_cbc_decrypt,
+ .ivsize = AES_BLOCK_SIZE,
+ .init = mxs_dcp_paes_init_tfm,
},
};
diff --git a/include/soc/fsl/dcp.h b/include/soc/fsl/dcp.h
new file mode 100644
index 000000000000..df6678ee10a1
--- /dev/null
+++ b/include/soc/fsl/dcp.h
@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Copyright (C) 2021 sigma star gmbh
+ * Authors: David Gstir <[email protected]>
+ * Richard Weinberger <[email protected]>
+ */
+
+#ifndef MXS_DCP_H
+#define MXS_DCP_H
+
+#define DCP_PAES_KEYSIZE 1
+#define DCP_PAES_KEY_SLOT0 0x00
+#define DCP_PAES_KEY_SLOT1 0x01
+#define DCP_PAES_KEY_SLOT2 0x02
+#define DCP_PAES_KEY_SLOT3 0x03
+#define DCP_PAES_KEY_UNIQUE 0xfe
+#define DCP_PAES_KEY_OTP 0xff
+
+#endif /* MXS_DCP_H */
--
2.35.3
On Tue Sep 12, 2023 at 2:11 PM EEST, David Gstir wrote:
> @@ -101,6 +102,7 @@ struct dcp_async_ctx {
> struct crypto_skcipher *fallback;
> unsigned int key_len;
> uint8_t key[AES_KEYSIZE_128];
> + bool refkey;
> };
s/refkey/key_referenced/
No reason to obfuscate it, especially since there is no supporting
documentation.
BR, Jarkko
On Tue Sep 12, 2023 at 2:11 PM EEST, David Gstir wrote:
> DCP is capable to performing AES with hardware-bound keys.
> These keys are not stored in main memory and are therefore not directly
> accessible by the operating system.
>
> So instead of feeding the key into DCP, we need to place a
> reference to such a key before initiating the crypto operation.
> Keys are referenced by a one byte identifiers.
>
> DCP supports 6 different keys: 4 slots in the secure memory area,
> a one time programmable key which can be burnt via on-chip fuses
> and an unique device key.
>
> Using these keys is restricted to in-kernel users that use them as building
> block for other crypto tools such as trusted keys. Allowing userspace
> (e.g. via AF_ALG) to use these keys to crypt or decrypt data is a security
> risk, because there is no access control mechanism.
>
> 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]>
> ---
> drivers/crypto/mxs-dcp.c | 107 +++++++++++++++++++++++++++++++++++----
> include/soc/fsl/dcp.h | 19 +++++++
> 2 files changed, 115 insertions(+), 11 deletions(-)
> create mode 100644 include/soc/fsl/dcp.h
>
> diff --git a/drivers/crypto/mxs-dcp.c b/drivers/crypto/mxs-dcp.c
> index f6b7bce0e656..d525cb41f2ca 100644
> --- a/drivers/crypto/mxs-dcp.c
> +++ b/drivers/crypto/mxs-dcp.c
> @@ -15,6 +15,7 @@
> #include <linux/platform_device.h>
> #include <linux/stmp_device.h>
> #include <linux/clk.h>
> +#include <soc/fsl/dcp.h>
>
> #include <crypto/aes.h>
> #include <crypto/sha1.h>
> @@ -101,6 +102,7 @@ struct dcp_async_ctx {
> struct crypto_skcipher *fallback;
> unsigned int key_len;
> uint8_t key[AES_KEYSIZE_128];
> + bool refkey;
> };
>
> struct dcp_aes_req_ctx {
> @@ -155,6 +157,7 @@ static struct dcp *global_sdcp;
> #define MXS_DCP_CONTROL0_HASH_TERM (1 << 13)
> #define MXS_DCP_CONTROL0_HASH_INIT (1 << 12)
> #define MXS_DCP_CONTROL0_PAYLOAD_KEY (1 << 11)
> +#define MXS_DCP_CONTROL0_OTP_KEY (1 << 10)
> #define MXS_DCP_CONTROL0_CIPHER_ENCRYPT (1 << 8)
> #define MXS_DCP_CONTROL0_CIPHER_INIT (1 << 9)
> #define MXS_DCP_CONTROL0_ENABLE_HASH (1 << 6)
> @@ -168,6 +171,8 @@ static struct dcp *global_sdcp;
> #define MXS_DCP_CONTROL1_CIPHER_MODE_ECB (0 << 4)
> #define MXS_DCP_CONTROL1_CIPHER_SELECT_AES128 (0 << 0)
>
> +#define MXS_DCP_CONTROL1_KEY_SELECT_SHIFT 8
> +
> static int mxs_dcp_start_dma(struct dcp_async_ctx *actx)
> {
> int dma_err;
> @@ -224,13 +229,16 @@ static int mxs_dcp_run_aes(struct dcp_async_ctx *actx,
> struct dcp *sdcp = global_sdcp;
> struct dcp_dma_desc *desc = &sdcp->coh->desc[actx->chan];
> struct dcp_aes_req_ctx *rctx = skcipher_request_ctx(req);
> + bool key_referenced = actx->refkey;
> int ret;
>
> - key_phys = dma_map_single(sdcp->dev, sdcp->coh->aes_key,
> - 2 * AES_KEYSIZE_128, DMA_TO_DEVICE);
> - ret = dma_mapping_error(sdcp->dev, key_phys);
> - if (ret)
> - return ret;
> + if (!key_referenced) {
> + key_phys = dma_map_single(sdcp->dev, sdcp->coh->aes_key,
> + 2 * AES_KEYSIZE_128, DMA_TO_DEVICE);
> + ret = dma_mapping_error(sdcp->dev, key_phys);
> + if (ret)
> + return ret;
> + }
>
> src_phys = dma_map_single(sdcp->dev, sdcp->coh->aes_in_buf,
> DCP_BUF_SZ, DMA_TO_DEVICE);
> @@ -255,8 +263,13 @@ static int mxs_dcp_run_aes(struct dcp_async_ctx *actx,
> MXS_DCP_CONTROL0_INTERRUPT |
> MXS_DCP_CONTROL0_ENABLE_CIPHER;
>
> - /* Payload contains the key. */
> - desc->control0 |= MXS_DCP_CONTROL0_PAYLOAD_KEY;
> + if (key_referenced) {
> + /* Set OTP key bit to select the key via KEY_SELECT. */
> + desc->control0 |= MXS_DCP_CONTROL0_OTP_KEY;
> + } else {
> + /* Payload contains the key. */
> + desc->control0 |= MXS_DCP_CONTROL0_PAYLOAD_KEY;
> + }
Remove curly braces (coding style).
>
> if (rctx->enc)
> desc->control0 |= MXS_DCP_CONTROL0_CIPHER_ENCRYPT;
> @@ -270,6 +283,9 @@ static int mxs_dcp_run_aes(struct dcp_async_ctx *actx,
> else
> desc->control1 |= MXS_DCP_CONTROL1_CIPHER_MODE_CBC;
>
> + if (key_referenced)
> + desc->control1 |= sdcp->coh->aes_key[0] << MXS_DCP_CONTROL1_KEY_SELECT_SHIFT;
> +
> desc->next_cmd_addr = 0;
> desc->source = src_phys;
> desc->destination = dst_phys;
> @@ -284,9 +300,10 @@ static int mxs_dcp_run_aes(struct dcp_async_ctx *actx,
> err_dst:
> dma_unmap_single(sdcp->dev, src_phys, DCP_BUF_SZ, DMA_TO_DEVICE);
> err_src:
> - dma_unmap_single(sdcp->dev, key_phys, 2 * AES_KEYSIZE_128,
> - DMA_TO_DEVICE);
> -
> + if (!key_referenced) {
> + dma_unmap_single(sdcp->dev, key_phys, 2 * AES_KEYSIZE_128,
> + DMA_TO_DEVICE);
> + }
Ditto.
> return ret;
> }
>
> @@ -453,7 +470,7 @@ static int mxs_dcp_aes_enqueue(struct skcipher_request *req, int enc, int ecb)
> struct dcp_aes_req_ctx *rctx = skcipher_request_ctx(req);
> int ret;
>
> - if (unlikely(actx->key_len != AES_KEYSIZE_128))
> + if (unlikely(actx->key_len != AES_KEYSIZE_128 && !actx->refkey))
> return mxs_dcp_block_fallback(req, enc);
>
> rctx->enc = enc;
> @@ -500,6 +517,7 @@ static int mxs_dcp_aes_setkey(struct crypto_skcipher *tfm, const u8 *key,
> * there can still be an operation in progress.
> */
> actx->key_len = len;
> + actx->refkey = false;
> if (len == AES_KEYSIZE_128) {
> memcpy(actx->key, key, len);
> return 0;
> @@ -516,6 +534,33 @@ static int mxs_dcp_aes_setkey(struct crypto_skcipher *tfm, const u8 *key,
> return crypto_skcipher_setkey(actx->fallback, key, len);
> }
>
> +static int mxs_dcp_aes_setrefkey(struct crypto_skcipher *tfm, const u8 *key,
> + unsigned int len)
> +{
> + struct dcp_async_ctx *actx = crypto_skcipher_ctx(tfm);
> +
> + if (len != DCP_PAES_KEYSIZE)
> + return -EINVAL;
> +
> + switch (key[0]) {
> + case DCP_PAES_KEY_SLOT0:
> + case DCP_PAES_KEY_SLOT1:
> + case DCP_PAES_KEY_SLOT2:
> + case DCP_PAES_KEY_SLOT3:
> + case DCP_PAES_KEY_UNIQUE:
> + case DCP_PAES_KEY_OTP:
> + memcpy(actx->key, key, len);
> + break;
I don't understand why the "commit" is split into two parts
(memcpy and assignments in different code blocks). You should
probably rather:
switch (key[0]) {
case DCP_PAES_KEY_SLOT0:
case DCP_PAES_KEY_SLOT1:
case DCP_PAES_KEY_SLOT2:
case DCP_PAES_KEY_SLOT3:
case DCP_PAES_KEY_UNIQUE:
case DCP_PAES_KEY_OTP:
memcpy(actx->key, key, len);
actx->key_len = len;
actx->refkey = true;
return 0;
default:
return -EINVAL;
}
}
Or alternatively you can move all operations after the switch-case
statement. IMHO, any state change is better to put into a singular
location.
> + default:
> + return -EINVAL;
> + }
> +
> + actx->key_len = len;
> + actx->refkey = true;
> +
> + return 0;
> +}
> +
> static int mxs_dcp_aes_fallback_init_tfm(struct crypto_skcipher *tfm)
> {
> const char *name = crypto_tfm_alg_name(crypto_skcipher_tfm(tfm));
> @@ -539,6 +584,13 @@ static void mxs_dcp_aes_fallback_exit_tfm(struct crypto_skcipher *tfm)
> crypto_free_skcipher(actx->fallback);
> }
>
> +static int mxs_dcp_paes_init_tfm(struct crypto_skcipher *tfm)
> +{
> + crypto_skcipher_set_reqsize(tfm, sizeof(struct dcp_aes_req_ctx));
> +
> + return 0;
> +}
> +
> /*
> * Hashing (SHA1/SHA256)
> */
> @@ -889,6 +941,39 @@ static struct skcipher_alg dcp_aes_algs[] = {
> .ivsize = AES_BLOCK_SIZE,
> .init = mxs_dcp_aes_fallback_init_tfm,
> .exit = mxs_dcp_aes_fallback_exit_tfm,
> + }, {
> + .base.cra_name = "ecb(paes)",
> + .base.cra_driver_name = "ecb-paes-dcp",
> + .base.cra_priority = 401,
> + .base.cra_alignmask = 15,
> + .base.cra_flags = CRYPTO_ALG_ASYNC | CRYPTO_ALG_INTERNAL,
> + .base.cra_blocksize = AES_BLOCK_SIZE,
> + .base.cra_ctxsize = sizeof(struct dcp_async_ctx),
> + .base.cra_module = THIS_MODULE,
> +
> + .min_keysize = DCP_PAES_KEYSIZE,
> + .max_keysize = DCP_PAES_KEYSIZE,
> + .setkey = mxs_dcp_aes_setrefkey,
> + .encrypt = mxs_dcp_aes_ecb_encrypt,
> + .decrypt = mxs_dcp_aes_ecb_decrypt,
> + .init = mxs_dcp_paes_init_tfm,
> + }, {
> + .base.cra_name = "cbc(paes)",
> + .base.cra_driver_name = "cbc-paes-dcp",
> + .base.cra_priority = 401,
> + .base.cra_alignmask = 15,
> + .base.cra_flags = CRYPTO_ALG_ASYNC | CRYPTO_ALG_INTERNAL,
> + .base.cra_blocksize = AES_BLOCK_SIZE,
> + .base.cra_ctxsize = sizeof(struct dcp_async_ctx),
> + .base.cra_module = THIS_MODULE,
> +
> + .min_keysize = DCP_PAES_KEYSIZE,
> + .max_keysize = DCP_PAES_KEYSIZE,
> + .setkey = mxs_dcp_aes_setrefkey,
> + .encrypt = mxs_dcp_aes_cbc_encrypt,
> + .decrypt = mxs_dcp_aes_cbc_decrypt,
> + .ivsize = AES_BLOCK_SIZE,
> + .init = mxs_dcp_paes_init_tfm,
> },
> };
>
> diff --git a/include/soc/fsl/dcp.h b/include/soc/fsl/dcp.h
> new file mode 100644
> index 000000000000..df6678ee10a1
> --- /dev/null
> +++ b/include/soc/fsl/dcp.h
> @@ -0,0 +1,19 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2021 sigma star gmbh
> + * Authors: David Gstir <[email protected]>
> + * Richard Weinberger <[email protected]>
Git already has author-field and commit can have co-developed-by so
this is totally obsolete.
> + */
> +
> +#ifndef MXS_DCP_H
> +#define MXS_DCP_H
> +
> +#define DCP_PAES_KEYSIZE 1
> +#define DCP_PAES_KEY_SLOT0 0x00
> +#define DCP_PAES_KEY_SLOT1 0x01
> +#define DCP_PAES_KEY_SLOT2 0x02
> +#define DCP_PAES_KEY_SLOT3 0x03
> +#define DCP_PAES_KEY_UNIQUE 0xfe
> +#define DCP_PAES_KEY_OTP 0xff
> +
> +#endif /* MXS_DCP_H */
> --
> 2.35.3
BR, Jarkko
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 | 85 +++++++++++++++++++
1 file changed, 85 insertions(+)
diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst
index 9bc9db8ec651..4452070afbe9 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 +470,44 @@ 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
+---------------
+
+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.
+ *
+ * @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;
--
2.35.3