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crypto: drbg - Simplify drbg_generate_long() and fold into caller

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Simplify drbg_generate_long() to use a more straightforward loop, and
then fold it into its only caller.  No functional change.

Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Eric Biggers 2026-04-19 23:34:12 -07:00 committed by Herbert Xu
parent 6585b5b4fd
commit 7ba94ec2d8
1 changed files with 17 additions and 31 deletions
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48
crypto/drbg.c
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@ -506,35 +506,6 @@ static int drbg_generate(struct drbg_state *drbg,
return len;
}
/*
* Wrapper around drbg_generate which can pull arbitrary long strings
* from the DRBG without hitting the maximum request limitation.
*
* Parameters: see drbg_generate
* Return codes: see drbg_generate -- if one drbg_generate request fails,
* the entire drbg_generate_long request fails
*/
static int drbg_generate_long(struct drbg_state *drbg,
unsigned char *buf, unsigned int buflen,
const u8 *addtl, size_t addtl_len)
{
unsigned int len = 0;
unsigned int slice = 0;
do {
int err = 0;
unsigned int chunk = 0;
slice = (buflen - len) / DRBG_MAX_REQUEST_BYTES;
chunk = slice ? DRBG_MAX_REQUEST_BYTES : (buflen - len);
mutex_lock(&drbg->drbg_mutex);
err = drbg_generate(drbg, buf + len, chunk, addtl, addtl_len);
mutex_unlock(&drbg->drbg_mutex);
if (0 > err)
return err;
len += chunk;
} while (slice > 0 && (len < buflen));
return 0;
}
static int drbg_prepare_hrng(struct drbg_state *drbg)
{
/* We do not need an HRNG in test mode. */
@ -676,7 +647,6 @@ static void drbg_kcapi_cleanup(struct crypto_tfm *tfm)
/*
* Generate random numbers invoked by the kernel crypto API:
* The API of the kernel crypto API is extended as follows:
*
* src is additional input supplied to the RNG.
* slen is the length of src.
@ -689,7 +659,23 @@ static int drbg_kcapi_random(struct crypto_rng *tfm,
{
struct drbg_state *drbg = crypto_rng_ctx(tfm);
return drbg_generate_long(drbg, dst, dlen, src, slen);
/*
* Break the request into multiple requests if needed, to avoid
* exceeding the maximum request length of the core algorithm.
*/
do {
unsigned int n = min(dlen, DRBG_MAX_REQUEST_BYTES);
int err;
mutex_lock(&drbg->drbg_mutex);
err = drbg_generate(drbg, dst, n, src, slen);
mutex_unlock(&drbg->drbg_mutex);
if (err < 0)
return err;
dst += n;
dlen -= n;
} while (dlen);
return 0;
}
/* Seed (i.e. instantiate) or re-seed the DRBG. */