Re: [PATCH bpf-next v2 1/5] crypto: Add BPF hash algorithm type registration module

[Song Liu]

On Fri, Dec 5, 2025 at 9:40 AM Daniel Hodges <g...@danielhodges.dev> wrote:
>
> Add bpf_crypto_shash module that registers a hash type with the BPF
> crypto infrastructure, enabling BPF programs to access kernel hash
> algorithms through a unified interface.
>
> Update the bpf_crypto_type interface with hash-specific callbacks:
>    - alloc_tfm: Allocates crypto_shash context with proper descriptor size
>    - free_tfm: Releases hash transform and context memory
>    - has_algo: Checks algorithm availability via crypto_has_shash()
>    - hash: Performs single-shot hashing via crypto_shash_digest()
>    - digestsize: Returns the output size for the hash algorithm
>    - get_flags: Exposes transform flags to BPF programs
>
> Update bpf_shash_ctx to contain crypto_shash transform and shash_desc
> descriptor to accommodate algorithm-specific descriptor requirements.
>
> Signed-off-by: Daniel Hodges <g...@danielhodges.dev>
> ---
>  crypto/Makefile           |  3 ++
>  crypto/bpf_crypto_shash.c | 94 +++++++++++++++++++++++++++++++++++++++
>  2 files changed, 97 insertions(+)
>  create mode 100644 crypto/bpf_crypto_shash.c
>
> diff --git a/crypto/Makefile b/crypto/Makefile
> index 16a35649dd91..853dff375906 100644
> --- a/crypto/Makefile
> +++ b/crypto/Makefile
> @@ -30,6 +30,9 @@ obj-$(CONFIG_CRYPTO_ECHAINIV) += echainiv.o
>  crypto_hash-y += ahash.o
>  crypto_hash-y += shash.o
>  obj-$(CONFIG_CRYPTO_HASH2) += crypto_hash.o
> +ifeq ($(CONFIG_BPF_SYSCALL),y)
> +obj-$(CONFIG_CRYPTO_HASH2) += bpf_crypto_shash.o
> +endif
>
>  obj-$(CONFIG_CRYPTO_AKCIPHER2) += akcipher.o
>  obj-$(CONFIG_CRYPTO_SIG2) += sig.o
> diff --git a/crypto/bpf_crypto_shash.c b/crypto/bpf_crypto_shash.c
> new file mode 100644
> index 000000000000..39032e7dd602
> --- /dev/null
> +++ b/crypto/bpf_crypto_shash.c
> @@ -0,0 +1,94 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +#include <linux/types.h>
> +#include <linux/module.h>
> +#include <linux/bpf_crypto.h>
> +#include <crypto/hash.h>
> +
> +struct bpf_shash_ctx {
> +       struct crypto_shash *tfm;
> +       struct shash_desc desc;
> +};

Instead of adding bpf_shash_ctx and bpf_ecdsa_ctx, can we extend
bpf_crypto_ctx to cover all hash and ECDSA? bpf_crypto_ctx has a
const pointer to bpf_crypto_type, so this should be possible?

Thanks,
Song