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crypto: drbg - replace int2byte with cpu_to_be 

The DRBG requires the conversion of an integer into a string
representation of that integer. The previous implementation converted
the given integer byte-wise. However, the kernel offers the cpu_to_be
function which already re-arranges the memory representation of an
integer such that it applies when interpreting the same memory as
character string.

The change therefore uses an integer-cast / union of the target
character array together with the cpu_to_be function to convert an
integer into its string representation.

Tests show that the Hash and CTR DRBG implementations (the HMAC DRBG
does not require such conversion) is about 10% faster (or requires less
computing power, respectively).

Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Stephan Mueller 2014-08-17 17:37:34 +02:00 committed by Herbert Xu
parent 4451d494b1
commit 72f3e00dd6
1 changed files with 18 additions and 16 deletions
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34
crypto/drbg.c
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@ -302,20 +302,19 @@ static bool drbg_fips_continuous_test(struct drbg_state *drbg,
* Convert an integer into a byte representation of this integer.
* The byte representation is big-endian
*
* @buf buffer holding the converted integer
* @val value to be converted
* @buflen length of buffer
* @buf buffer holding the converted integer -- caller must ensure that
* buffer size is at least 32 bit
*/
#if (defined(CONFIG_CRYPTO_DRBG_HASH) || defined(CONFIG_CRYPTO_DRBG_CTR))
static inline void drbg_int2byte(unsigned char *buf, uint64_t val,
size_t buflen)
static inline void drbg_cpu_to_be32(__u32 val, unsigned char *buf)
{
unsigned char *byte;
uint64_t i;
struct s {
__u32 conv;
};
struct s *conversion = (struct s *) buf;
byte = buf + (buflen - 1);
for (i = 0; i < buflen; i++)
*(byte--) = val >> (i * 8) & 0xff;
conversion->conv = cpu_to_be32(val);
}
/*
@ -483,10 +482,10 @@ static int drbg_ctr_df(struct drbg_state *drbg,
/* 10.4.2 step 2 -- calculate the entire length of all input data */
list_for_each_entry(seed, seedlist, list)
inputlen += seed->len;
drbg_int2byte(&L_N[0], inputlen, 4);
drbg_cpu_to_be32(inputlen, &L_N[0]);
/* 10.4.2 step 3 */
drbg_int2byte(&L_N[4], bytes_to_return, 4);
drbg_cpu_to_be32(bytes_to_return, &L_N[4]);
/* 10.4.2 step 5: length is L_N, input_string, one byte, padding */
padlen = (inputlen + sizeof(L_N) + 1) % (drbg_blocklen(drbg));
@ -517,7 +516,7 @@ static int drbg_ctr_df(struct drbg_state *drbg,
* holds zeros after allocation -- even the increment of i
* is irrelevant as the increment remains within length of i
*/
drbg_int2byte(iv, i, 4);
drbg_cpu_to_be32(i, iv);
/* 10.4.2 step 9.2 -- BCC and concatenation with temp */
ret = drbg_ctr_bcc(drbg, temp + templen, K, &bcc_list);
if (ret)
@ -862,7 +861,7 @@ static int drbg_hash_df(struct drbg_state *drbg,
/* 10.4.1 step 3 */
input[0] = 1;
drbg_int2byte(&input[1], (outlen * 8), 4);
drbg_cpu_to_be32((outlen * 8), &input[1]);
/* 10.4.1 step 4.1 -- concatenation of data for input into hash */
drbg_string_fill(&data, input, 5);
@ -1023,7 +1022,10 @@ static int drbg_hash_generate(struct drbg_state *drbg,
{
int len = 0;
int ret = 0;
unsigned char req[8];
union {
unsigned char req[8];
__u64 req_int;
} u;
unsigned char prefix = DRBG_PREFIX3;
struct drbg_string data1, data2;
LIST_HEAD(datalist);
@ -1053,8 +1055,8 @@ static int drbg_hash_generate(struct drbg_state *drbg,
drbg->scratchpad, drbg_blocklen(drbg));
drbg_add_buf(drbg->V, drbg_statelen(drbg),
drbg->C, drbg_statelen(drbg));
drbg_int2byte(req, drbg->reseed_ctr, sizeof(req));
drbg_add_buf(drbg->V, drbg_statelen(drbg), req, 8);
u.req_int = cpu_to_be64(drbg->reseed_ctr);
drbg_add_buf(drbg->V, drbg_statelen(drbg), u.req, 8);
out:
memset(drbg->scratchpad, 0, drbg_blocklen(drbg));