When user space issues a KEYCTL_PKEY_QUERY system call for a NIST P521
key, the key_size is incorrectly reported as 528 bits instead of 521.
That's because the key size obtained through crypto_sig_keysize() is in
bytes and software_key_query() multiplies by 8 to yield the size in bits.
The underlying assumption is that the key size is always a multiple of 8.
With the recent addition of NIST P521, that's no longer the case.
Fix by returning the key_size in bits from crypto_sig_keysize() and
adjusting the calculations in software_key_query().
The ->key_size() callbacks of sig_alg algorithms now return the size in
bits, whereas the ->digest_size() and ->max_size() callbacks return the
size in bytes. This matches with the units in struct keyctl_pkey_query.
Fixes: a7d45ba77d ("crypto: ecdsa - Register NIST P521 and extend test suite")
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Reviewed-by: Ignat Korchagin <ignat@cloudflare.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Herbert notes that DIV_ROUND_UP() may overflow unnecessarily if an ecdsa
implementation's ->key_size() callback returns an unusually large value.
Herbert instead suggests (for a division by 8):
X / 8 + !!(X & 7)
Based on this formula, introduce a generic DIV_ROUND_UP_POW2() macro and
use it in lieu of DIV_ROUND_UP() for ->key_size() return values.
Additionally, use the macro in ecc_digits_from_bytes(), whose "nbytes"
parameter is a ->key_size() return value in some instances, or a
user-specified ASN.1 length in the case of ecdsa_get_signature_rs().
Link: https://lore.kernel.org/r/Z3iElsILmoSu6FuC@gondor.apana.org.au/
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Alternatively to the X9.62 encoding of ecdsa signatures, which uses
ASN.1 and is already supported by the kernel, there's another common
encoding called P1363. It stores r and s as the concatenation of two
big endian, unsigned integers. The name originates from IEEE P1363.
Add a P1363 template in support of the forthcoming SPDM library
(Security Protocol and Data Model) for PCI device authentication.
P1363 is prescribed by SPDM 1.2.1 margin no 44:
"For ECDSA signatures, excluding SM2, in SPDM, the signature shall be
the concatenation of r and s. The size of r shall be the size of
the selected curve. Likewise, the size of s shall be the size of
the selected curve. See BaseAsymAlgo in NEGOTIATE_ALGORITHMS for
the size of r and s. The byte order for r and s shall be in big
endian order. When placing ECDSA signatures into an SPDM signature
field, r shall come first followed by s."
Link: https://www.dmtf.org/sites/default/files/standards/documents/DSP0274_1.2.1.pdf
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
