crypto: drbg - reduce number of setkey calls

The CTR DRBG code always set the key for each sym cipher invocation even
though the key has not been changed.

The patch ensures that the setkey is only invoked when a new key is
generated by the DRBG.

With this patch, the CTR DRBG performance increases by more than 150%.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/drbg.c

@@ -252,8 +252,10 @@ MODULE_ALIAS_CRYPTO("drbg_nopr_ctr_aes192");
 MODULE_ALIAS_CRYPTO("drbg_pr_ctr_aes128");
 MODULE_ALIAS_CRYPTO("drbg_nopr_ctr_aes128");
 
-static int drbg_kcapi_sym(struct drbg_state *drbg, const unsigned char *key,
-			  unsigned char *outval, const struct drbg_string *in);
+static void drbg_kcapi_symsetkey(struct drbg_state *drbg,
+				 const unsigned char *key);
+static int drbg_kcapi_sym(struct drbg_state *drbg, unsigned char *outval,
+			  const struct drbg_string *in);
 static int drbg_init_sym_kernel(struct drbg_state *drbg);
 static int drbg_fini_sym_kernel(struct drbg_state *drbg);
 
@@ -270,6 +272,7 @@ static int drbg_ctr_bcc(struct drbg_state *drbg,
 	drbg_string_fill(&data, out, drbg_blocklen(drbg));
 
 	/* 10.4.3 step 2 / 4 */
+	drbg_kcapi_symsetkey(drbg, key);
 	list_for_each_entry(curr, in, list) {
 		const unsigned char *pos = curr->buf;
 		size_t len = curr->len;
@@ -278,7 +281,7 @@ static int drbg_ctr_bcc(struct drbg_state *drbg,
 			/* 10.4.3 step 4.2 */
 			if (drbg_blocklen(drbg) == cnt) {
 				cnt = 0;
-				ret = drbg_kcapi_sym(drbg, key, out, &data);
+				ret = drbg_kcapi_sym(drbg, out, &data);
 				if (ret)
 					return ret;
 			}
@@ -290,7 +293,7 @@ static int drbg_ctr_bcc(struct drbg_state *drbg,
 	}
 	/* 10.4.3 step 4.2 for last block */
 	if (cnt)
-		ret = drbg_kcapi_sym(drbg, key, out, &data);
+		ret = drbg_kcapi_sym(drbg, out, &data);
 
 	return ret;
 }
@@ -425,6 +428,7 @@ static int drbg_ctr_df(struct drbg_state *drbg,
 	/* 10.4.2 step 12: overwriting of outval is implemented in next step */
 
 	/* 10.4.2 step 13 */
+	drbg_kcapi_symsetkey(drbg, temp);
 	while (generated_len < bytes_to_return) {
 		short blocklen = 0;
 		/*
@@ -432,7 +436,7 @@ static int drbg_ctr_df(struct drbg_state *drbg,
 		 * implicit as the key is only drbg_blocklen in size based on
 		 * the implementation of the cipher function callback
 		 */
-		ret = drbg_kcapi_sym(drbg, temp, X, &cipherin);
+		ret = drbg_kcapi_sym(drbg, X, &cipherin);
 		if (ret)
 			goto out;
 		blocklen = (drbg_blocklen(drbg) <
@@ -488,6 +492,7 @@ static int drbg_ctr_update(struct drbg_state *drbg, struct list_head *seed,
 		ret = drbg_ctr_df(drbg, df_data, drbg_statelen(drbg), seed);
 		if (ret)
 			goto out;
+		drbg_kcapi_symsetkey(drbg, drbg->C);
 	}
 
 	drbg_string_fill(&cipherin, drbg->V, drbg_blocklen(drbg));
@@ -500,7 +505,7 @@ static int drbg_ctr_update(struct drbg_state *drbg, struct list_head *seed,
 		crypto_inc(drbg->V, drbg_blocklen(drbg));
 		/*
 		 * 10.2.1.2 step 2.2 */
-		ret = drbg_kcapi_sym(drbg, drbg->C, temp + len, &cipherin);
+		ret = drbg_kcapi_sym(drbg, temp + len, &cipherin);
 		if (ret)
 			goto out;
 		/* 10.2.1.2 step 2.3 and 3 */
@@ -517,6 +522,7 @@ static int drbg_ctr_update(struct drbg_state *drbg, struct list_head *seed,
 
 	/* 10.2.1.2 step 5 */
 	memcpy(drbg->C, temp, drbg_keylen(drbg));
+	drbg_kcapi_symsetkey(drbg, drbg->C);
 	/* 10.2.1.2 step 6 */
 	memcpy(drbg->V, temp + drbg_keylen(drbg), drbg_blocklen(drbg));
 	ret = 0;
@@ -546,6 +552,7 @@ static int drbg_ctr_generate(struct drbg_state *drbg,
 		ret = drbg_ctr_update(drbg, addtl, 2);
 		if (ret)
 			return 0;
+		drbg_kcapi_symsetkey(drbg, drbg->C);
 	}
 
 	/* 10.2.1.5.2 step 4.1 */
@@ -554,7 +561,7 @@ static int drbg_ctr_generate(struct drbg_state *drbg,
 	while (len < buflen) {
 		int outlen = 0;
 		/* 10.2.1.5.2 step 4.2 */
-		ret = drbg_kcapi_sym(drbg, drbg->C, drbg->scratchpad, &data);
+		ret = drbg_kcapi_sym(drbg, drbg->scratchpad, &data);
 		if (ret) {
 			len = ret;
 			goto out;
@@ -1653,13 +1660,21 @@ static int drbg_fini_sym_kernel(struct drbg_state *drbg)
 	return 0;
 }
 
-static int drbg_kcapi_sym(struct drbg_state *drbg, const unsigned char *key,
-			  unsigned char *outval, const struct drbg_string *in)
+static void drbg_kcapi_symsetkey(struct drbg_state *drbg,
+				 const unsigned char *key)
 {
 	struct crypto_cipher *tfm =
 		(struct crypto_cipher *)drbg->priv_data;
 
 	crypto_cipher_setkey(tfm, key, (drbg_keylen(drbg)));
+}
+
+static int drbg_kcapi_sym(struct drbg_state *drbg, unsigned char *outval,
+			  const struct drbg_string *in)
+{
+	struct crypto_cipher *tfm =
+		(struct crypto_cipher *)drbg->priv_data;
+
 	/* there is only component in *in */
 	BUG_ON(in->len < drbg_blocklen(drbg));
 	crypto_cipher_encrypt_one(tfm, outval, in->buf);