[PATCH 24/38] crypto: drbg - Install separate seed functions for pr and nopr

[Eric Biggers]

Set rng_alg::seed to different functions for the prediction-resistant
and non-prediction-resistant algorithms, so that the function does not
need to parse the algorithm name to figure out which algorithm it is.

Signed-off-by: Eric Biggers <ebiggers@xxxxxxxxxx>
---
 crypto/drbg.c | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/crypto/drbg.c b/crypto/drbg.c
index 161070b10f85..c29f4ca93d1b 100644
--- a/crypto/drbg.c
+++ b/crypto/drbg.c
@@ -731,20 +731,15 @@ static int drbg_kcapi_random(struct crypto_rng *tfm,
 	}
 
 	return drbg_generate_long(drbg, dst, dlen, addtl);
 }
 
-/*
- * Seed the DRBG invoked by the kernel crypto API
- */
+/* Seed (i.e. instantiate) or re-seed the DRBG. */
 static int drbg_kcapi_seed(struct crypto_rng *tfm,
-			   const u8 *seed, unsigned int slen)
+			   const u8 *seed, unsigned int slen, bool pr)
 {
 	struct drbg_state *drbg = crypto_rng_ctx(tfm);
-	struct crypto_tfm *tfm_base = crypto_rng_tfm(tfm);
-	bool pr = memcmp(crypto_tfm_alg_driver_name(tfm_base),
-			 "drbg_nopr_", 10) != 0;
 	struct drbg_string string;
 	struct drbg_string *seed_string = NULL;
 
 	if (0 < slen) {
 		drbg_string_fill(&string, seed, slen);
@@ -752,10 +747,22 @@ static int drbg_kcapi_seed(struct crypto_rng *tfm,
 	}
 
 	return drbg_instantiate(drbg, seed_string, pr);
 }
 
+static int drbg_kcapi_seed_pr(struct crypto_rng *tfm,
+			      const u8 *seed, unsigned int slen)
+{
+	return drbg_kcapi_seed(tfm, seed, slen, /* pr= */ true);
+}
+
+static int drbg_kcapi_seed_nopr(struct crypto_rng *tfm,
+				const u8 *seed, unsigned int slen)
+{
+	return drbg_kcapi_seed(tfm, seed, slen, /* pr= */ false);
+}
+
 /***************************************************************
  * Kernel module: code to load the module
  ***************************************************************/
 
 /*
@@ -825,11 +832,11 @@ static struct rng_alg drbg_algs[] = {
 		.base.cra_priority	= 200,
 		.base.cra_ctxsize	= sizeof(struct drbg_state),
 		.base.cra_module	= THIS_MODULE,
 		.base.cra_init		= drbg_kcapi_init,
 		.set_ent		= drbg_kcapi_set_entropy,
-		.seed			= drbg_kcapi_seed,
+		.seed			= drbg_kcapi_seed_pr,
 		.generate		= drbg_kcapi_random,
 		.base.cra_exit		= drbg_kcapi_cleanup,
 	},
 	{
 		.base.cra_name		= "stdrng",
@@ -837,11 +844,11 @@ static struct rng_alg drbg_algs[] = {
 		.base.cra_priority	= 201,
 		.base.cra_ctxsize	= sizeof(struct drbg_state),
 		.base.cra_module	= THIS_MODULE,
 		.base.cra_init		= drbg_kcapi_init,
 		.set_ent		= drbg_kcapi_set_entropy,
-		.seed			= drbg_kcapi_seed,
+		.seed			= drbg_kcapi_seed_nopr,
 		.generate		= drbg_kcapi_random,
 		.base.cra_exit		= drbg_kcapi_cleanup,
 	},
 };
 
-- 
2.53.0