On Wed, Dec 17, 2025 at 06:45:14AM +0900, Song Liu wrote:
On Sun, Dec 7, 2025 at 7:01 PM Daniel Hodges git@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 git@danielhodges.dev
crypto/Makefile | 3 ++ crypto/bpf_crypto_shash.c | 95 +++++++++++++++++++++++++++++++++++++++ 2 files changed, 98 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..95c178ec0ce8 --- /dev/null +++ b/crypto/bpf_crypto_shash.c @@ -0,0 +1,95 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */ +#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;+};
+static void *bpf_crypto_shash_alloc_tfm(const char *algo) +{
struct bpf_shash_ctx *ctx;struct crypto_shash *tfm;tfm = crypto_alloc_shash(algo, 0, 0);if (IS_ERR(tfm))return tfm;ctx = kzalloc(sizeof(*ctx) + crypto_shash_descsize(tfm), GFP_KERNEL);if (!ctx) {crypto_free_shash(tfm);return ERR_PTR(-ENOMEM);}ctx->tfm = tfm;ctx->desc.tfm = tfm;return ctx;+}
What if we let bpf_crypto_shash_alloc_tfm() return a "struct shash_desc"? shash_desc->tfm is already struct crypto_shash. This way, we don't need bpf_shash_ctx any more. Would this work?
Thanks, Song
Yeah, that's much cleaner than the void * return.
-Daniel