Trusted keys unseal the key blob on load, but keep the sealed payload in
the blob field so that every subsequent read (export) will simply
convert this field to hex and send it to userspace.
With DCP-based trusted keys, we decrypt the blob encryption key (BEK)
in the Kernel due hardware limitations and then decrypt the blob payload.
BEK decryption is done in-place which means that the trusted key blob
field is modified and it consequently holds the BEK in plain text.
Every subsequent read of that key thus send the plain text BEK instead
of the encrypted BEK to userspace.
This issue only occurs when importing a trusted DCP-based key and
then exporting it again. This should rarely happen as the common use cases
are to either create a new trusted key and export it, or import a key
blob and then just use it without exporting it again.
Fix this by performing BEK decryption and encryption in a dedicated
buffer. Further always wipe the plain text BEK buffer to prevent leaking
the key via uninitialized memory.
Cc: stable@vger.kernel.org # v6.10+
Fixes: 2e8a0f40a3 ("KEYS: trusted: Introduce NXP DCP-backed trusted keys")
Signed-off-by: David Gstir <david@sigma-star.at>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
The DCP trusted key type uses the wrong helper function to store
the blob's payload length which can lead to the wrong byte order
being used in case this would ever run on big endian architectures.
Fix by using correct helper function.
Cc: stable@vger.kernel.org # v6.10+
Fixes: 2e8a0f40a3 ("KEYS: trusted: Introduce NXP DCP-backed trusted keys")
Suggested-by: Richard Weinberger <richard@nod.at>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202405240610.fj53EK0q-lkp@intel.com/
Signed-off-by: David Gstir <david@sigma-star.at>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
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 <richard@nod.at>
Signed-off-by: Richard Weinberger <richard@nod.at>
Co-developed-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
Signed-off-by: David Gstir <david@sigma-star.at>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
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@nod.at>
Signed-off-by: Richard Weinberger <richard@nod.at>
Co-developed-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
Signed-off-by: David Gstir <david@sigma-star.at>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
