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Commit 72f3e00d authored by Stephan Mueller's avatar Stephan Mueller Committed by Herbert Xu
Browse files

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: default avatarStephan Mueller <smueller@chronox.de>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent 4451d494

crypto/drbg.c

+18 −16
Original line number Diff line number Diff line
@@ -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;

	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));