Re: [PATCH v3 01/14] mpi: Introduce mpi_key_length()

Jarkko Sakkinen
2024-09-12T13:26:36Z

On Wed Sep 11, 2024 at 3:28 PM EEST, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu@huawei.com>
>
> Introduce the new function to get the number of bits and bytes from an MPI.
>
> Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
> Signed-off-by: David Howells <dhowells@redhat.com>
> ---
> include/linux/mpi.h | 2 ++
> lib/crypto/mpi/mpicoder.c | 33 ++++++++++++++++++++++++++-------
> 2 files changed, 28 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/mpi.h b/include/linux/mpi.h
> index eb0d1c1db208..a7dd4c9d8120 100644
> --- a/include/linux/mpi.h
> +++ b/include/linux/mpi.h
> @@ -90,6 +90,8 @@ enum gcry_mpi_format {
> };
>
> MPI mpi_read_raw_data(const void *xbuffer, size_t nbytes);
> +int mpi_key_length(const void *xbuffer, unsigned int ret_nread,
> + unsigned int *nbits_arg, unsigned int *nbytes_arg);

"_arg" - what is the point of this?

> MPI mpi_read_from_buffer(const void *buffer, unsigned *ret_nread);
> int mpi_fromstr(MPI val, const char *str);
> MPI mpi_scanval(const char *string);
> diff --git a/lib/crypto/mpi/mpicoder.c b/lib/crypto/mpi/mpicoder.c
> index 3cb6bd148fa9..92447a1c8bf9 100644
> --- a/lib/crypto/mpi/mpicoder.c
> +++ b/lib/crypto/mpi/mpicoder.c
> @@ -79,22 +79,41 @@ MPI mpi_read_raw_data(const void *xbuffer, size_t nbytes)
> }
> EXPORT_SYMBOL_GPL(mpi_read_raw_data);
>
> -MPI mpi_read_from_buffer(const void *xbuffer, unsigned *ret_nread)
> +int mpi_key_length(const void *xbuffer, unsigned int ret_nread,
> + unsigned int *nbits_arg, unsigned int *nbytes_arg)
> {
> const uint8_t *buffer = xbuffer;
> - unsigned int nbits, nbytes;
> - MPI val;
> + unsigned int nbits;
>
> - if (*ret_nread < 2)
> - return ERR_PTR(-EINVAL);
> + if (ret_nread < 2)
> + return -EINVAL;
> nbits = buffer[0] << 8 | buffer[1];
>
> if (nbits > MAX_EXTERN_MPI_BITS) {
> pr_info("MPI: mpi too large (%u bits)\n", nbits);
> - return ERR_PTR(-EINVAL);
> + return -EINVAL;
> }
>
> - nbytes = DIV_ROUND_UP(nbits, 8);
> + if (nbits_arg)
> + *nbits_arg = nbits;
> + if (nbytes_arg)
> + *nbytes_arg = DIV_ROUND_UP(nbits, 8);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(mpi_key_length);
> +
> +MPI mpi_read_from_buffer(const void *xbuffer, unsigned int *ret_nread)
> +{
> + const uint8_t *buffer = xbuffer;
> + unsigned int nbytes;
> + MPI val;
> + int ret;
> +
> + ret = mpi_key_length(xbuffer, *ret_nread, NULL, &nbytes);
> + if (ret < 0)
> + return ERR_PTR(ret);
> +
> if (nbytes + 2 > *ret_nread) {
> pr_info("MPI: mpi larger than buffer nbytes=%u ret_nread=%u\n",
> nbytes, *ret_nread);

BR, Jarkko