[PATCH] crypto: drbg - use crypto_inc

[Stephan Mueller]

The DRBG internal buffer addition function is replaced with crypto_inc when
a buffer is to be incremented by one.

The function drbg_add_buf is moved to the CONFIG_CRYPTO_DRBG_HASH ifdef
area as it is now only needed for the Hash DRBG.

Signed-off-by: Stephan Mueller <***@chronox.de>
---
crypto/drbg.c | 79 ++++++++++++++++++++++++++++-------------------------------
1 file changed, 38 insertions(+), 41 deletions(-)

diff --git a/crypto/drbg.c b/crypto/drbg.c
index 54cfd48..8c0a742 100644
--- a/crypto/drbg.c
+++ b/crypto/drbg.c
@@ -283,38 +283,6 @@ static inline void drbg_cpu_to_be32(__u32 val, unsigned char *buf)

conversion->conv = cpu_to_be32(val);
}
-
-/*
- * Increment buffer
- *
- * @dst buffer to increment
- * @add value to add
- */
-static inline void drbg_add_buf(unsigned char *dst, size_t dstlen,
- const unsigned char *add, size_t addlen)
-{
- /* implied: dstlen > addlen */
- unsigned char *dstptr;
- const unsigned char *addptr;
- unsigned int remainder = 0;
- size_t len = addlen;
-
- dstptr = dst + (dstlen-1);
- addptr = add + (addlen-1);
- while (len) {
- remainder += *dstptr + *addptr;
- *dstptr = remainder & 0xff;
- remainder >>= 8;
- len--; dstptr--; addptr--;
- }
- len = dstlen - addlen;
- while (len && remainder > 0) {
- remainder = *dstptr + 1;
- *dstptr = remainder & 0xff;
- remainder >>= 8;
- len--; dstptr--;
- }
-}
#endif /* defined(CONFIG_CRYPTO_DRBG_HASH) || defined(CONFIG_CRYPTO_DRBG_CTR) */

/******************************************************************
@@ -554,7 +522,6 @@ static int drbg_ctr_update(struct drbg_state *drbg, struct list_head *seed,
unsigned char *temp_p, *df_data_p; /* pointer to iterate over buffers */
unsigned int len = 0;
struct drbg_string cipherin;
- unsigned char prefix = DRBG_PREFIX1;

memset(temp, 0, drbg_statelen(drbg) + drbg_blocklen(drbg));
if (3 > reseed)
@@ -574,7 +541,7 @@ static int drbg_ctr_update(struct drbg_state *drbg, struct list_head *seed,
*/
while (len < (drbg_statelen(drbg))) {
/* 10.2.1.2 step 2.1 */
- drbg_add_buf(drbg->V, drbg_blocklen(drbg), &prefix, 1);
+ crypto_inc(drbg->V, drbg_blocklen(drbg));
/*
* 10.2.1.2 step 2.2 */
ret = drbg_kcapi_sym(drbg, drbg->C, temp + len, &cipherin);
@@ -617,7 +584,6 @@ static int drbg_ctr_generate(struct drbg_state *drbg,
int len = 0;
int ret = 0;
struct drbg_string data;
- unsigned char prefix = DRBG_PREFIX1;

memset(drbg->scratchpad, 0, drbg_blocklen(drbg));

@@ -629,7 +595,7 @@ static int drbg_ctr_generate(struct drbg_state *drbg,
}

/* 10.2.1.5.2 step 4.1 */
- drbg_add_buf(drbg->V, drbg_blocklen(drbg), &prefix, 1);
+ crypto_inc(drbg->V, drbg_blocklen(drbg));
drbg_string_fill(&data, drbg->V, drbg_blocklen(drbg));
while (len < buflen) {
int outlen = 0;
@@ -643,7 +609,7 @@ static int drbg_ctr_generate(struct drbg_state *drbg,
drbg_blocklen(drbg) : (buflen - len);
if (!drbg_fips_continuous_test(drbg, drbg->scratchpad)) {
/* 10.2.1.5.2 step 6 */
- drbg_add_buf(drbg->V, drbg_blocklen(drbg), &prefix, 1);
+ crypto_inc(drbg->V, drbg_blocklen(drbg));
continue;
}
/* 10.2.1.5.2 step 4.3 */
@@ -651,7 +617,7 @@ static int drbg_ctr_generate(struct drbg_state *drbg,
len += outlen;
/* 10.2.1.5.2 step 6 */
if (len < buflen)
- drbg_add_buf(drbg->V, drbg_blocklen(drbg), &prefix, 1);
+ crypto_inc(drbg->V, drbg_blocklen(drbg));
}

/* 10.2.1.5.2 step 6 */
@@ -797,6 +763,38 @@ static struct drbg_state_ops drbg_hmac_ops = {
#ifdef CONFIG_CRYPTO_DRBG_HASH
#define CRYPTO_DRBG_HASH_STRING "HASH "
/*
+ * Increment buffer
+ *
+ * @dst buffer to increment
+ * @add value to add
+ */
+static inline void drbg_add_buf(unsigned char *dst, size_t dstlen,
+ const unsigned char *add, size_t addlen)
+{
+ /* implied: dstlen > addlen */
+ unsigned char *dstptr;
+ const unsigned char *addptr;
+ unsigned int remainder = 0;
+ size_t len = addlen;
+
+ dstptr = dst + (dstlen-1);
+ addptr = add + (addlen-1);
+ while (len) {
+ remainder += *dstptr + *addptr;
+ *dstptr = remainder & 0xff;
+ remainder >>= 8;
+ len--; dstptr--; addptr--;
+ }
+ len = dstlen - addlen;
+ while (len && remainder > 0) {
+ remainder = *dstptr + 1;
+ *dstptr = remainder & 0xff;
+ remainder >>= 8;
+ len--; dstptr--;
+ }
+}
+
+/*
* scratchpad usage: as drbg_hash_update and drbg_hash_df are used
* interlinked, the scratchpad is used as follows:
* drbg_hash_update
@@ -942,7 +940,6 @@ static int drbg_hash_hashgen(struct drbg_state *drbg,
unsigned char *dst = drbg->scratchpad + drbg_statelen(drbg);
struct drbg_string data;
LIST_HEAD(datalist);
- unsigned char prefix = DRBG_PREFIX1;

memset(src, 0, drbg_statelen(drbg));
memset(dst, 0, drbg_blocklen(drbg));
@@ -963,7 +960,7 @@ static int drbg_hash_hashgen(struct drbg_state *drbg,
outlen = (drbg_blocklen(drbg) < (buflen - len)) ?
drbg_blocklen(drbg) : (buflen - len);
if (!drbg_fips_continuous_test(drbg, dst)) {
- drbg_add_buf(src, drbg_statelen(drbg), &prefix, 1);
+ crypto_inc(src, drbg_statelen(drbg));
continue;
}
/* 10.1.1.4 step hashgen 4.2 */
@@ -971,7 +968,7 @@ static int drbg_hash_hashgen(struct drbg_state *drbg,
len += outlen;
/* 10.1.1.4 hashgen step 4.3 */
if (len < buflen)
- drbg_add_buf(src, drbg_statelen(drbg), &prefix, 1);
+ crypto_inc(src, drbg_statelen(drbg));
}

out: