crypto: drbg - remove superflowous memsets

The DRBG code contains memset(0) calls to initialize a varaible
that are not necessary as the variable is always overwritten by
the processing.

This patch increases the CTR and Hash DRBGs by about 5%.

Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

diff --git a/crypto/drbg.c b/crypto/drbg.c
index c14274ac8d61bfbed4201485e68de822d5b46d32..56c1d7ec3d9e3280725cbf6358207318a3d5ca35 100644 (file)
--- a/crypto/drbg.c
+++ b/crypto/drbg.c
@@ -308,9 +308,6 @@ static int drbg_ctr_bcc(struct drbg_state *drbg,
 
        drbg_string_fill(&data, out, drbg_blocklen(drbg));
 
-       /* 10.4.3 step 1 */
-       memset(out, 0, drbg_blocklen(drbg));
-
        /* 10.4.3 step 2 / 4 */
        list_for_each_entry(curr, in, list) {
                const unsigned char *pos = curr->buf;
@@ -406,7 +403,6 @@ static int drbg_ctr_df(struct drbg_state *drbg,
 
        memset(pad, 0, drbg_blocklen(drbg));
        memset(iv, 0, drbg_blocklen(drbg));
-       memset(temp, 0, drbg_statelen(drbg));
 
        /* 10.4.2 step 1 is implicit as we work byte-wise */
 
@@ -523,7 +519,6 @@ static int drbg_ctr_update(struct drbg_state *drbg, struct list_head *seed,
        unsigned int len = 0;
        struct drbg_string cipherin;
 
-       memset(temp, 0, drbg_statelen(drbg) + drbg_blocklen(drbg));
        if (3 > reseed)
                memset(df_data, 0, drbg_statelen(drbg));
 
@@ -585,8 +580,6 @@ static int drbg_ctr_generate(struct drbg_state *drbg,
        int ret = 0;
        struct drbg_string data;
 
-       memset(drbg->scratchpad, 0, drbg_blocklen(drbg));
-
        /* 10.2.1.5.2 step 2 */
        if (addtl && !list_empty(addtl)) {
                ret = drbg_ctr_update(drbg, addtl, 2);
@@ -761,7 +754,6 @@ static struct drbg_state_ops drbg_hmac_ops = {
        .generate       = drbg_hmac_generate,
        .crypto_init    = drbg_init_hash_kernel,
        .crypto_fini    = drbg_fini_hash_kernel,
-
 };
 #endif /* CONFIG_CRYPTO_DRBG_HMAC */
 
@@ -838,8 +830,6 @@ static int drbg_hash_df(struct drbg_state *drbg,
        unsigned char *tmp = drbg->scratchpad + drbg_statelen(drbg);
        struct drbg_string data;
 
-       memset(tmp, 0, drbg_blocklen(drbg));
-
        /* 10.4.1 step 3 */
        input[0] = 1;
        drbg_cpu_to_be32((outlen * 8), &input[1]);
@@ -879,7 +869,6 @@ static int drbg_hash_update(struct drbg_state *drbg, struct list_head *seed,
        unsigned char *V = drbg->scratchpad;
        unsigned char prefix = DRBG_PREFIX1;
 
-       memset(drbg->scratchpad, 0, drbg_statelen(drbg));
        if (!seed)
                return -EINVAL;
 
@@ -921,9 +910,6 @@ static int drbg_hash_process_addtl(struct drbg_state *drbg,
        LIST_HEAD(datalist);
        unsigned char prefix = DRBG_PREFIX2;
 
-       /* this is value w as per documentation */
-       memset(drbg->scratchpad, 0, drbg_blocklen(drbg));
-
        /* 10.1.1.4 step 2 */
        if (!addtl || list_empty(addtl))
                return 0;
@@ -959,9 +945,6 @@ static int drbg_hash_hashgen(struct drbg_state *drbg,
        struct drbg_string data;
        LIST_HEAD(datalist);
 
-       memset(src, 0, drbg_statelen(drbg));
-       memset(dst, 0, drbg_blocklen(drbg));
-
        /* 10.1.1.4 step hashgen 2 */
        memcpy(src, drbg->V, drbg_statelen(drbg));
 
@@ -1018,7 +1001,6 @@ static int drbg_hash_generate(struct drbg_state *drbg,
        len = drbg_hash_hashgen(drbg, buf, buflen);
 
        /* this is the value H as documented in 10.1.1.4 */
-       memset(drbg->scratchpad, 0, drbg_blocklen(drbg));
        /* 10.1.1.4 step 4 */
        drbg_string_fill(&data1, &prefix, 1);
        list_add_tail(&data1.list, &datalist);