On Tue Oct 24, 2023 at 7:20 PM EEST, David Gstir wrote:
> 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 <richard@xxxxxx>
> Signed-off-by: Richard Weinberger <richard@xxxxxx>
> Co-developed-by: David Oberhollenzer <david.oberhollenzer@xxxxxxxxxxxxx>
> Signed-off-by: David Oberhollenzer <david.oberhollenzer@xxxxxxxxxxxxx>
> Signed-off-by: David Gstir <david@xxxxxxxxxxxxx>
> ---
> include/keys/trusted_dcp.h | 11 +
> 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 | 311 ++++++++++++++++++++++
> 5 files changed, 337 insertions(+), 2 deletions(-)
> 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 dbfdd8536468..c6b80b7e5c78 100644
> --- a/security/keys/trusted-keys/Kconfig
> +++ b/security/keys/trusted-keys/Kconfig
> @@ -33,6 +33,13 @@ config TRUSTED_KEYS_CAAM
> Enable use of NXP's Cryptographic Accelerator and Assurance Module
> (CAAM) as trusted key backend.
>
> -if !TRUSTED_KEYS_TPM && !TRUSTED_KEYS_TEE && !TRUSTED_KEYS_CAAM
> +config TRUSTED_KEYS_DCP
> + bool "DCP-based trusted keys"
> + depends on CRYPTO_DEV_MXS_DCP >= TRUSTED_KEYS
> + default y
> + help
> + Enable use of NXP's DCP (Data Co-Processor) as trusted key backend.
> +
> +if !TRUSTED_KEYS_TPM && !TRUSTED_KEYS_TEE && !TRUSTED_KEYS_CAAM && !TRUSTED_KEYS_DCP
This does not scale tbh.
I'd suggest to add additional patch before adding the new key type,
which clears this up a little bit.
First:
config HAVE_TRUSTED_KEYS
bool
And then following this pattern to all trusted key types:
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.
And finally:
if !HAVE_TRUSTED_KEYS
comment "No trust source selected!"
endif
BR, Jarkko
