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crypto: hmac - remove unnecessary alignment logic

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The hmac template is setting its alignmask to that of its underlying
unkeyed hash algorithm, and it is aligning the ipad and opad fields in
its tfm context to that alignment.  However, hmac does not actually need
any sort of alignment itself, which makes this pointless except to keep
the pads aligned to what the underlying algorithm prefers.  But very few
shash algorithms actually set an alignmask, and it is being removed from
those remaining ones; also, after setkey, the pads are only passed to
crypto_shash_import and crypto_shash_export which ignore the alignmask.

Therefore, make the hmac template stop setting an alignmask and simply
use natural alignment for ipad and opad.  Note, this change also moves
the pads from the beginning of the tfm context to the end, which makes
much more sense; the variable-length fields should be at the end.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Eric Biggers 2023-10-18 22:53:34 -07:00 committed by Herbert Xu
parent f9dc9f2e40
commit 25c74a39e0
1 changed files with 22 additions and 34 deletions
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56
crypto/hmac.c
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@ -24,31 +24,20 @@
struct hmac_ctx {
struct crypto_shash *hash;
/* Contains 'u8 ipad[statesize];', then 'u8 opad[statesize];' */
u8 pads[];
};
static inline void *align_ptr(void *p, unsigned int align)
{
return (void *)ALIGN((unsigned long)p, align);
}
static inline struct hmac_ctx *hmac_ctx(struct crypto_shash *tfm)
{
return align_ptr(crypto_shash_ctx_aligned(tfm) +
crypto_shash_statesize(tfm) * 2,
crypto_tfm_ctx_alignment());
}
static int hmac_setkey(struct crypto_shash *parent,
const u8 *inkey, unsigned int keylen)
{
int bs = crypto_shash_blocksize(parent);
int ds = crypto_shash_digestsize(parent);
int ss = crypto_shash_statesize(parent);
char *ipad = crypto_shash_ctx_aligned(parent);
char *opad = ipad + ss;
struct hmac_ctx *ctx = align_ptr(opad + ss,
crypto_tfm_ctx_alignment());
struct crypto_shash *hash = ctx->hash;
struct hmac_ctx *tctx = crypto_shash_ctx(parent);
struct crypto_shash *hash = tctx->hash;
u8 *ipad = &tctx->pads[0];
u8 *opad = &tctx->pads[ss];
SHASH_DESC_ON_STACK(shash, hash);
unsigned int i;
@ -94,16 +83,18 @@ static int hmac_export(struct shash_desc *pdesc, void *out)
static int hmac_import(struct shash_desc *pdesc, const void *in)
{
struct shash_desc *desc = shash_desc_ctx(pdesc);
struct hmac_ctx *ctx = hmac_ctx(pdesc->tfm);
const struct hmac_ctx *tctx = crypto_shash_ctx(pdesc->tfm);
desc->tfm = ctx->hash;
desc->tfm = tctx->hash;
return crypto_shash_import(desc, in);
}
static int hmac_init(struct shash_desc *pdesc)
{
return hmac_import(pdesc, crypto_shash_ctx_aligned(pdesc->tfm));
const struct hmac_ctx *tctx = crypto_shash_ctx(pdesc->tfm);
return hmac_import(pdesc, &tctx->pads[0]);
}
static int hmac_update(struct shash_desc *pdesc,
@ -119,7 +110,8 @@ static int hmac_final(struct shash_desc *pdesc, u8 *out)
struct crypto_shash *parent = pdesc->tfm;
int ds = crypto_shash_digestsize(parent);
int ss = crypto_shash_statesize(parent);
char *opad = crypto_shash_ctx_aligned(parent) + ss;
const struct hmac_ctx *tctx = crypto_shash_ctx(parent);
const u8 *opad = &tctx->pads[ss];
struct shash_desc *desc = shash_desc_ctx(pdesc);
return crypto_shash_final(desc, out) ?:
@ -134,7 +126,8 @@ static int hmac_finup(struct shash_desc *pdesc, const u8 *data,
struct crypto_shash *parent = pdesc->tfm;
int ds = crypto_shash_digestsize(parent);
int ss = crypto_shash_statesize(parent);
char *opad = crypto_shash_ctx_aligned(parent) + ss;
const struct hmac_ctx *tctx = crypto_shash_ctx(parent);
const u8 *opad = &tctx->pads[ss];
struct shash_desc *desc = shash_desc_ctx(pdesc);
return crypto_shash_finup(desc, data, nbytes, out) ?:
@ -147,7 +140,7 @@ static int hmac_init_tfm(struct crypto_shash *parent)
struct crypto_shash *hash;
struct shash_instance *inst = shash_alg_instance(parent);
struct crypto_shash_spawn *spawn = shash_instance_ctx(inst);
struct hmac_ctx *ctx = hmac_ctx(parent);
struct hmac_ctx *tctx = crypto_shash_ctx(parent);
hash = crypto_spawn_shash(spawn);
if (IS_ERR(hash))
@ -156,14 +149,14 @@ static int hmac_init_tfm(struct crypto_shash *parent)
parent->descsize = sizeof(struct shash_desc) +
crypto_shash_descsize(hash);
ctx->hash = hash;
tctx->hash = hash;
return 0;
}
static int hmac_clone_tfm(struct crypto_shash *dst, struct crypto_shash *src)
{
struct hmac_ctx *sctx = hmac_ctx(src);
struct hmac_ctx *dctx = hmac_ctx(dst);
struct hmac_ctx *sctx = crypto_shash_ctx(src);
struct hmac_ctx *dctx = crypto_shash_ctx(dst);
struct crypto_shash *hash;
hash = crypto_clone_shash(sctx->hash);
@ -176,9 +169,9 @@ static int hmac_clone_tfm(struct crypto_shash *dst, struct crypto_shash *src)
static void hmac_exit_tfm(struct crypto_shash *parent)
{
struct hmac_ctx *ctx = hmac_ctx(parent);
struct hmac_ctx *tctx = crypto_shash_ctx(parent);
crypto_free_shash(ctx->hash);
crypto_free_shash(tctx->hash);
}
static int hmac_create(struct crypto_template *tmpl, struct rtattr **tb)
@ -225,15 +218,10 @@ static int hmac_create(struct crypto_template *tmpl, struct rtattr **tb)
inst->alg.base.cra_priority = alg->cra_priority;
inst->alg.base.cra_blocksize = alg->cra_blocksize;
inst->alg.base.cra_alignmask = alg->cra_alignmask;
inst->alg.base.cra_ctxsize = sizeof(struct hmac_ctx) + (ss * 2);
ss = ALIGN(ss, alg->cra_alignmask + 1);
inst->alg.digestsize = ds;
inst->alg.statesize = ss;
inst->alg.base.cra_ctxsize = sizeof(struct hmac_ctx) +
ALIGN(ss * 2, crypto_tfm_ctx_alignment());
inst->alg.init = hmac_init;
inst->alg.update = hmac_update;
inst->alg.final = hmac_final;