Re: [PATCH v2] KEYS: asymmetric: Copy sig and digest in public_key_verify_signature()

Herbert Xu
2022-12-12T09:16:42Z

On Mon, Dec 12, 2022 at 10:07:38AM +0100, Roberto Sassu wrote:
>
> The problem is a misalignment between req->src_len (set to sig->s_size
> by akcipher_request_set_crypt()) and the length of the scatterlist (if
> we set the latter to sig->s_size + sig->digest_size).
>
> When rsa_enc() calls mpi_read_raw_from_sgl(), it passes req->src_len as
> argument, and the latter allocates the MPI according to that. However,
> it does parsing depending on the length of the scatterlist.
>
> If there are two scatterlists, it is not a problem, there is no
> misalignment. mpi_read_raw_from_sgl() picks the first. If there is just
> one, mpi_read_raw_from_sgl() parses all data there.

Thanks for the explanation. That's definitely a bug which should
be fixed either in the RSA code or in MPI.

I'll look into it.

Cheers,
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt