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Message-ID: <CAMj1kXF2BEv1GvHdYOMRoq0_V03r27Yr6DTM-Rp3kR7OrgMn4A@mail.gmail.com>
Date: Mon, 14 Jul 2025 15:24:54 +1000
From: Ard Biesheuvel <ardb@...nel.org>
To: Eric Biggers <ebiggers@...nel.org>
Cc: linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
"Jason A . Donenfeld" <Jason@...c4.com>
Subject: Re: [PATCH] lib/crypto: sha2: Add hmac_sha*_init_usingrawkey()
On Sat, 12 Jul 2025 at 07:59, Eric Biggers <ebiggers@...nel.org> wrote:
>
> While the HMAC library functions support both incremental and one-shot
> computation and both prepared and raw keys, the combination of raw key
> + incremental was missing. It turns out that several potential users of
> the HMAC library functions (tpm2-sessions.c, smb2transport.c,
> trusted_tpm1.c) want exactly that.
>
> Therefore, add the missing functions hmac_sha*_init_usingrawkey().
>
> Implement them in an optimized way that directly initializes the HMAC
> context without a separate key preparation step.
>
> Reimplement the one-shot raw key functions hmac_sha*_usingrawkey() on
> top of the new functions, which makes them a bit more efficient.
>
> Signed-off-by: Eric Biggers <ebiggers@...nel.org>
Reviewed-by: Ard Biesheuvel <ardb@...nel.org>
> ---
> include/crypto/sha2.h | 60 +++++++++++++++++++++++++++++++++++++++++++
> lib/crypto/sha256.c | 53 ++++++++++++++++++++++++++------------
> lib/crypto/sha512.c | 55 +++++++++++++++++++++++++++------------
> 3 files changed, 134 insertions(+), 34 deletions(-)
>
> diff --git a/include/crypto/sha2.h b/include/crypto/sha2.h
> index e0a08f6addd00..15e461e568cca 100644
> --- a/include/crypto/sha2.h
> +++ b/include/crypto/sha2.h
> @@ -245,10 +245,25 @@ static inline void hmac_sha224_init(struct hmac_sha224_ctx *ctx,
> const struct hmac_sha224_key *key)
> {
> __hmac_sha256_init(&ctx->ctx, &key->key);
> }
>
> +/**
> + * hmac_sha224_init_usingrawkey() - Initialize an HMAC-SHA224 context for a new
> + * message, using a raw key
> + * @ctx: (output) the HMAC context to initialize
> + * @raw_key: the raw HMAC-SHA224 key
> + * @raw_key_len: the key length in bytes. All key lengths are supported.
> + *
> + * If you don't need incremental computation, consider hmac_sha224_usingrawkey()
> + * instead.
> + *
> + * Context: Any context.
> + */
> +void hmac_sha224_init_usingrawkey(struct hmac_sha224_ctx *ctx,
> + const u8 *raw_key, size_t raw_key_len);
> +
> /**
> * hmac_sha224_update() - Update an HMAC-SHA224 context with message data
> * @ctx: the HMAC context to update; must have been initialized
> * @data: the message data
> * @data_len: the data length in bytes
> @@ -403,10 +418,25 @@ static inline void hmac_sha256_init(struct hmac_sha256_ctx *ctx,
> const struct hmac_sha256_key *key)
> {
> __hmac_sha256_init(&ctx->ctx, &key->key);
> }
>
> +/**
> + * hmac_sha256_init_usingrawkey() - Initialize an HMAC-SHA256 context for a new
> + * message, using a raw key
> + * @ctx: (output) the HMAC context to initialize
> + * @raw_key: the raw HMAC-SHA256 key
> + * @raw_key_len: the key length in bytes. All key lengths are supported.
> + *
> + * If you don't need incremental computation, consider hmac_sha256_usingrawkey()
> + * instead.
> + *
> + * Context: Any context.
> + */
> +void hmac_sha256_init_usingrawkey(struct hmac_sha256_ctx *ctx,
> + const u8 *raw_key, size_t raw_key_len);
> +
> /**
> * hmac_sha256_update() - Update an HMAC-SHA256 context with message data
> * @ctx: the HMAC context to update; must have been initialized
> * @data: the message data
> * @data_len: the data length in bytes
> @@ -595,10 +625,25 @@ static inline void hmac_sha384_init(struct hmac_sha384_ctx *ctx,
> const struct hmac_sha384_key *key)
> {
> __hmac_sha512_init(&ctx->ctx, &key->key);
> }
>
> +/**
> + * hmac_sha384_init_usingrawkey() - Initialize an HMAC-SHA384 context for a new
> + * message, using a raw key
> + * @ctx: (output) the HMAC context to initialize
> + * @raw_key: the raw HMAC-SHA384 key
> + * @raw_key_len: the key length in bytes. All key lengths are supported.
> + *
> + * If you don't need incremental computation, consider hmac_sha384_usingrawkey()
> + * instead.
> + *
> + * Context: Any context.
> + */
> +void hmac_sha384_init_usingrawkey(struct hmac_sha384_ctx *ctx,
> + const u8 *raw_key, size_t raw_key_len);
> +
> /**
> * hmac_sha384_update() - Update an HMAC-SHA384 context with message data
> * @ctx: the HMAC context to update; must have been initialized
> * @data: the message data
> * @data_len: the data length in bytes
> @@ -753,10 +798,25 @@ static inline void hmac_sha512_init(struct hmac_sha512_ctx *ctx,
> const struct hmac_sha512_key *key)
> {
> __hmac_sha512_init(&ctx->ctx, &key->key);
> }
>
> +/**
> + * hmac_sha512_init_usingrawkey() - Initialize an HMAC-SHA512 context for a new
> + * message, using a raw key
> + * @ctx: (output) the HMAC context to initialize
> + * @raw_key: the raw HMAC-SHA512 key
> + * @raw_key_len: the key length in bytes. All key lengths are supported.
> + *
> + * If you don't need incremental computation, consider hmac_sha512_usingrawkey()
> + * instead.
> + *
> + * Context: Any context.
> + */
> +void hmac_sha512_init_usingrawkey(struct hmac_sha512_ctx *ctx,
> + const u8 *raw_key, size_t raw_key_len);
> +
> /**
> * hmac_sha512_update() - Update an HMAC-SHA512 context with message data
> * @ctx: the HMAC context to update; must have been initialized
> * @data: the message data
> * @data_len: the data length in bytes
> diff --git a/lib/crypto/sha256.c b/lib/crypto/sha256.c
> index 808438d4f4278..8fa15165d23e8 100644
> --- a/lib/crypto/sha256.c
> +++ b/lib/crypto/sha256.c
> @@ -261,11 +261,12 @@ void sha256(const u8 *data, size_t len, u8 out[SHA256_DIGEST_SIZE])
> }
> EXPORT_SYMBOL(sha256);
>
> /* pre-boot environment (as indicated by __DISABLE_EXPORTS) doesn't need HMAC */
> #ifndef __DISABLE_EXPORTS
> -static void __hmac_sha256_preparekey(struct __hmac_sha256_key *key,
> +static void __hmac_sha256_preparekey(struct sha256_block_state *istate,
> + struct sha256_block_state *ostate,
> const u8 *raw_key, size_t raw_key_len,
> const struct sha256_block_state *iv)
> {
> union {
> u8 b[SHA256_BLOCK_SIZE];
> @@ -281,33 +282,35 @@ static void __hmac_sha256_preparekey(struct __hmac_sha256_key *key,
> memcpy(derived_key.b, raw_key, raw_key_len);
> }
>
> for (size_t i = 0; i < ARRAY_SIZE(derived_key.w); i++)
> derived_key.w[i] ^= REPEAT_BYTE(HMAC_IPAD_VALUE);
> - key->istate = *iv;
> - sha256_blocks(&key->istate, derived_key.b, 1);
> + *istate = *iv;
> + sha256_blocks(istate, derived_key.b, 1);
>
> for (size_t i = 0; i < ARRAY_SIZE(derived_key.w); i++)
> derived_key.w[i] ^= REPEAT_BYTE(HMAC_OPAD_VALUE ^
> HMAC_IPAD_VALUE);
> - key->ostate = *iv;
> - sha256_blocks(&key->ostate, derived_key.b, 1);
> + *ostate = *iv;
> + sha256_blocks(ostate, derived_key.b, 1);
>
> memzero_explicit(&derived_key, sizeof(derived_key));
> }
>
> void hmac_sha224_preparekey(struct hmac_sha224_key *key,
> const u8 *raw_key, size_t raw_key_len)
> {
> - __hmac_sha256_preparekey(&key->key, raw_key, raw_key_len, &sha224_iv);
> + __hmac_sha256_preparekey(&key->key.istate, &key->key.ostate,
> + raw_key, raw_key_len, &sha224_iv);
> }
> EXPORT_SYMBOL_GPL(hmac_sha224_preparekey);
>
> void hmac_sha256_preparekey(struct hmac_sha256_key *key,
> const u8 *raw_key, size_t raw_key_len)
> {
> - __hmac_sha256_preparekey(&key->key, raw_key, raw_key_len, &sha256_iv);
> + __hmac_sha256_preparekey(&key->key.istate, &key->key.ostate,
> + raw_key, raw_key_len, &sha256_iv);
> }
> EXPORT_SYMBOL_GPL(hmac_sha256_preparekey);
>
> void __hmac_sha256_init(struct __hmac_sha256_ctx *ctx,
> const struct __hmac_sha256_key *key)
> @@ -315,10 +318,28 @@ void __hmac_sha256_init(struct __hmac_sha256_ctx *ctx,
> __sha256_init(&ctx->sha_ctx, &key->istate, SHA256_BLOCK_SIZE);
> ctx->ostate = key->ostate;
> }
> EXPORT_SYMBOL_GPL(__hmac_sha256_init);
>
> +void hmac_sha224_init_usingrawkey(struct hmac_sha224_ctx *ctx,
> + const u8 *raw_key, size_t raw_key_len)
> +{
> + __hmac_sha256_preparekey(&ctx->ctx.sha_ctx.state, &ctx->ctx.ostate,
> + raw_key, raw_key_len, &sha224_iv);
> + ctx->ctx.sha_ctx.bytecount = SHA256_BLOCK_SIZE;
> +}
> +EXPORT_SYMBOL_GPL(hmac_sha224_init_usingrawkey);
> +
> +void hmac_sha256_init_usingrawkey(struct hmac_sha256_ctx *ctx,
> + const u8 *raw_key, size_t raw_key_len)
> +{
> + __hmac_sha256_preparekey(&ctx->ctx.sha_ctx.state, &ctx->ctx.ostate,
> + raw_key, raw_key_len, &sha256_iv);
> + ctx->ctx.sha_ctx.bytecount = SHA256_BLOCK_SIZE;
> +}
> +EXPORT_SYMBOL_GPL(hmac_sha256_init_usingrawkey);
> +
> static void __hmac_sha256_final(struct __hmac_sha256_ctx *ctx,
> u8 *out, size_t digest_size)
> {
> /* Generate the padded input for the outer hash in ctx->sha_ctx.buf. */
> __sha256_final(&ctx->sha_ctx, ctx->sha_ctx.buf, digest_size);
> @@ -374,29 +395,27 @@ EXPORT_SYMBOL_GPL(hmac_sha256);
>
> void hmac_sha224_usingrawkey(const u8 *raw_key, size_t raw_key_len,
> const u8 *data, size_t data_len,
> u8 out[SHA224_DIGEST_SIZE])
> {
> - struct hmac_sha224_key key;
> -
> - hmac_sha224_preparekey(&key, raw_key, raw_key_len);
> - hmac_sha224(&key, data, data_len, out);
> + struct hmac_sha224_ctx ctx;
>
> - memzero_explicit(&key, sizeof(key));
> + hmac_sha224_init_usingrawkey(&ctx, raw_key, raw_key_len);
> + hmac_sha224_update(&ctx, data, data_len);
> + hmac_sha224_final(&ctx, out);
> }
> EXPORT_SYMBOL_GPL(hmac_sha224_usingrawkey);
>
> void hmac_sha256_usingrawkey(const u8 *raw_key, size_t raw_key_len,
> const u8 *data, size_t data_len,
> u8 out[SHA256_DIGEST_SIZE])
> {
> - struct hmac_sha256_key key;
> -
> - hmac_sha256_preparekey(&key, raw_key, raw_key_len);
> - hmac_sha256(&key, data, data_len, out);
> + struct hmac_sha256_ctx ctx;
>
> - memzero_explicit(&key, sizeof(key));
> + hmac_sha256_init_usingrawkey(&ctx, raw_key, raw_key_len);
> + hmac_sha256_update(&ctx, data, data_len);
> + hmac_sha256_final(&ctx, out);
> }
> EXPORT_SYMBOL_GPL(hmac_sha256_usingrawkey);
> #endif /* !__DISABLE_EXPORTS */
>
> #ifdef sha256_mod_init_arch
> diff --git a/lib/crypto/sha512.c b/lib/crypto/sha512.c
> index d514721491ca0..d8062188be98a 100644
> --- a/lib/crypto/sha512.c
> +++ b/lib/crypto/sha512.c
> @@ -247,11 +247,12 @@ void sha512(const u8 *data, size_t len, u8 out[SHA512_DIGEST_SIZE])
> sha512_update(&ctx, data, len);
> sha512_final(&ctx, out);
> }
> EXPORT_SYMBOL_GPL(sha512);
>
> -static void __hmac_sha512_preparekey(struct __hmac_sha512_key *key,
> +static void __hmac_sha512_preparekey(struct sha512_block_state *istate,
> + struct sha512_block_state *ostate,
> const u8 *raw_key, size_t raw_key_len,
> const struct sha512_block_state *iv)
> {
> union {
> u8 b[SHA512_BLOCK_SIZE];
> @@ -267,33 +268,35 @@ static void __hmac_sha512_preparekey(struct __hmac_sha512_key *key,
> memcpy(derived_key.b, raw_key, raw_key_len);
> }
>
> for (size_t i = 0; i < ARRAY_SIZE(derived_key.w); i++)
> derived_key.w[i] ^= REPEAT_BYTE(HMAC_IPAD_VALUE);
> - key->istate = *iv;
> - sha512_blocks(&key->istate, derived_key.b, 1);
> + *istate = *iv;
> + sha512_blocks(istate, derived_key.b, 1);
>
> for (size_t i = 0; i < ARRAY_SIZE(derived_key.w); i++)
> derived_key.w[i] ^= REPEAT_BYTE(HMAC_OPAD_VALUE ^
> HMAC_IPAD_VALUE);
> - key->ostate = *iv;
> - sha512_blocks(&key->ostate, derived_key.b, 1);
> + *ostate = *iv;
> + sha512_blocks(ostate, derived_key.b, 1);
>
> memzero_explicit(&derived_key, sizeof(derived_key));
> }
>
> void hmac_sha384_preparekey(struct hmac_sha384_key *key,
> const u8 *raw_key, size_t raw_key_len)
> {
> - __hmac_sha512_preparekey(&key->key, raw_key, raw_key_len, &sha384_iv);
> + __hmac_sha512_preparekey(&key->key.istate, &key->key.ostate,
> + raw_key, raw_key_len, &sha384_iv);
> }
> EXPORT_SYMBOL_GPL(hmac_sha384_preparekey);
>
> void hmac_sha512_preparekey(struct hmac_sha512_key *key,
> const u8 *raw_key, size_t raw_key_len)
> {
> - __hmac_sha512_preparekey(&key->key, raw_key, raw_key_len, &sha512_iv);
> + __hmac_sha512_preparekey(&key->key.istate, &key->key.ostate,
> + raw_key, raw_key_len, &sha512_iv);
> }
> EXPORT_SYMBOL_GPL(hmac_sha512_preparekey);
>
> void __hmac_sha512_init(struct __hmac_sha512_ctx *ctx,
> const struct __hmac_sha512_key *key)
> @@ -301,10 +304,30 @@ void __hmac_sha512_init(struct __hmac_sha512_ctx *ctx,
> __sha512_init(&ctx->sha_ctx, &key->istate, SHA512_BLOCK_SIZE);
> ctx->ostate = key->ostate;
> }
> EXPORT_SYMBOL_GPL(__hmac_sha512_init);
>
> +void hmac_sha384_init_usingrawkey(struct hmac_sha384_ctx *ctx,
> + const u8 *raw_key, size_t raw_key_len)
> +{
> + __hmac_sha512_preparekey(&ctx->ctx.sha_ctx.state, &ctx->ctx.ostate,
> + raw_key, raw_key_len, &sha384_iv);
> + ctx->ctx.sha_ctx.bytecount_lo = SHA512_BLOCK_SIZE;
> + ctx->ctx.sha_ctx.bytecount_hi = 0;
> +}
> +EXPORT_SYMBOL_GPL(hmac_sha384_init_usingrawkey);
> +
> +void hmac_sha512_init_usingrawkey(struct hmac_sha512_ctx *ctx,
> + const u8 *raw_key, size_t raw_key_len)
> +{
> + __hmac_sha512_preparekey(&ctx->ctx.sha_ctx.state, &ctx->ctx.ostate,
> + raw_key, raw_key_len, &sha512_iv);
> + ctx->ctx.sha_ctx.bytecount_lo = SHA512_BLOCK_SIZE;
> + ctx->ctx.sha_ctx.bytecount_hi = 0;
> +}
> +EXPORT_SYMBOL_GPL(hmac_sha512_init_usingrawkey);
> +
> static void __hmac_sha512_final(struct __hmac_sha512_ctx *ctx,
> u8 *out, size_t digest_size)
> {
> /* Generate the padded input for the outer hash in ctx->sha_ctx.buf. */
> __sha512_final(&ctx->sha_ctx, ctx->sha_ctx.buf, digest_size);
> @@ -360,29 +383,27 @@ EXPORT_SYMBOL_GPL(hmac_sha512);
>
> void hmac_sha384_usingrawkey(const u8 *raw_key, size_t raw_key_len,
> const u8 *data, size_t data_len,
> u8 out[SHA384_DIGEST_SIZE])
> {
> - struct hmac_sha384_key key;
> -
> - hmac_sha384_preparekey(&key, raw_key, raw_key_len);
> - hmac_sha384(&key, data, data_len, out);
> + struct hmac_sha384_ctx ctx;
>
> - memzero_explicit(&key, sizeof(key));
> + hmac_sha384_init_usingrawkey(&ctx, raw_key, raw_key_len);
> + hmac_sha384_update(&ctx, data, data_len);
> + hmac_sha384_final(&ctx, out);
> }
> EXPORT_SYMBOL_GPL(hmac_sha384_usingrawkey);
>
> void hmac_sha512_usingrawkey(const u8 *raw_key, size_t raw_key_len,
> const u8 *data, size_t data_len,
> u8 out[SHA512_DIGEST_SIZE])
> {
> - struct hmac_sha512_key key;
> -
> - hmac_sha512_preparekey(&key, raw_key, raw_key_len);
> - hmac_sha512(&key, data, data_len, out);
> + struct hmac_sha512_ctx ctx;
>
> - memzero_explicit(&key, sizeof(key));
> + hmac_sha512_init_usingrawkey(&ctx, raw_key, raw_key_len);
> + hmac_sha512_update(&ctx, data, data_len);
> + hmac_sha512_final(&ctx, out);
> }
> EXPORT_SYMBOL_GPL(hmac_sha512_usingrawkey);
>
> #ifdef sha512_mod_init_arch
> static int __init sha512_mod_init(void)
>
> base-commit: e14ada7ed2e1dda5161051be1d2131b606c8ab96
> --
> 2.50.1
>
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