linux-kernel - Re: [PATCH bpf-next v3 5/6] bpf: Add ECDSA signature verification kfuncs

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Message-ID: <CAPhsuW5OKja2U5x-X_N_F7DN7D_RAZYf9ryoMb4RBHtKKSidhw@mail.gmail.com>
Date: Wed, 17 Dec 2025 07:35:22 +0900
From: Song Liu <song@...nel.org>
To: Daniel Hodges <git@...ielhodges.dev>
Cc: bpf@...r.kernel.org, ast@...nel.org, andrii@...nel.org, 
	daniel@...earbox.net, vadim.fedorenko@...ux.dev, yatsenko@...a.com, 
	martin.lau@...ux.dev, eddyz87@...il.com, haoluo@...gle.com, jolsa@...nel.org, 
	john.fastabend@...il.com, kpsingh@...nel.org, sdf@...ichev.me, 
	yonghong.song@...ux.dev, herbert@...dor.apana.org.au, davem@...emloft.net, 
	linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-kselftest@...r.kernel.org
Subject: Re: [PATCH bpf-next v3 5/6] bpf: Add ECDSA signature verification kfuncs

On Mon, Dec 8, 2025 at 5:43 PM Daniel Hodges <git@...ielhodges.dev> wrote:
>
> Add context-based ECDSA signature verification kfuncs:
> - bpf_ecdsa_ctx_create(): Creates reusable ECDSA context with public key
> - bpf_ecdsa_verify(): Verifies signatures using the context
> - bpf_ecdsa_ctx_acquire(): Increments context reference count
> - bpf_ecdsa_ctx_release(): Releases context with RCU safety
>
> The ECDSA implementation supports NIST curves (P-256, P-384, P-521) and
> uses the kernel's crypto_sig API. Public keys must be in uncompressed
> format (0x04 || x || y), and signatures are in r || s format.
>
> Signed-off-by: Daniel Hodges <git@...ielhodges.dev>
> ---
>  kernel/bpf/crypto.c | 230 ++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 230 insertions(+)
>
> diff --git a/kernel/bpf/crypto.c b/kernel/bpf/crypto.c
> index 47e6a43a46d4..138abe58e87e 100644
> --- a/kernel/bpf/crypto.c
> +++ b/kernel/bpf/crypto.c
> @@ -9,6 +9,7 @@
>  #include <linux/scatterlist.h>
>  #include <linux/skbuff.h>
>  #include <crypto/skcipher.h>
> +#include <crypto/sig.h>
>
>  struct bpf_crypto_type_list {
>         const struct bpf_crypto_type *type;
> @@ -57,6 +58,21 @@ struct bpf_crypto_ctx {
>         refcount_t usage;
>  };
>
> +#if IS_ENABLED(CONFIG_CRYPTO_ECDSA)
> +/**
> + * struct bpf_ecdsa_ctx - refcounted BPF ECDSA context structure
> + * @tfm:       The crypto_sig transform for ECDSA operations
> + * @rcu:       The RCU head used to free the context with RCU safety
> + * @usage:     Object reference counter. When the refcount goes to 0, the
> + *             memory is released with RCU safety.
> + */
> +struct bpf_ecdsa_ctx {
> +       struct crypto_sig *tfm;
> +       struct rcu_head rcu;
> +       refcount_t usage;
> +};
> +#endif

Can we use bpf_crypto_ctx for ECDSA?

Thanks,
Song