crypto: ecdh - Initialize ctx->private_key in proper byte order

The private key in ctx->private_key is currently initialized in reverse
byte order in ecdh_set_secret and whenever the key is needed in proper
byte order the variable priv is introduced and the bytes from
ctx->private_key are copied into priv while being byte-swapped
(ecc_swap_digits). To get rid of the unnecessary byte swapping initialize
ctx->private_key in proper byte order and clean up all functions that were
previously using priv or were called with ctx->private_key:

- ecc_gen_privkey: Directly initialize the passed ctx->private_key with
  random bytes filling all the digits of the private key. Get rid of the
  priv variable. This function only has ecdh_set_secret as a caller to
  create NIST P192/256/384 private keys.

- crypto_ecdh_shared_secret: Called only from ecdh_compute_value with
  ctx->private_key. Get rid of the priv variable and work with the passed
  private_key directly.

- ecc_make_pub_key: Called only from ecdh_compute_value with
  ctx->private_key. Get rid of the priv variable and work with the passed
  private_key directly.

Cc: Salvatore Benedetto <salvatore.benedetto@intel.com>
Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Acked-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 3 insertions, 5 deletions

diff --git a/crypto/ecdh.c b/crypto/ecdh.c
index c02c9a2b9682..72cfd1590156 100644
--- a/crypto/ecdh.c
+++ b/crypto/ecdh.c
@@ -27,7 +27,6 @@ static int ecdh_set_secret(struct crypto_kpp *tfm, const void *buf,
 			   unsigned int len)
 {
 	struct ecdh_ctx *ctx = ecdh_get_ctx(tfm);
-	u64 priv[ECC_MAX_DIGITS];
 	struct ecdh params;
 	int ret = 0;
 
@@ -41,15 +40,14 @@ static int ecdh_set_secret(struct crypto_kpp *tfm, const void *buf,
 		return ecc_gen_privkey(ctx->curve_id, ctx->ndigits,
 				       ctx->private_key);
 
-	memcpy(ctx->private_key, params.key, params.key_size);
-	ecc_swap_digits(ctx->private_key, priv, ctx->ndigits);
+	ecc_digits_from_bytes(params.key, params.key_size,
+			      ctx->private_key, ctx->ndigits);
 
 	if (ecc_is_key_valid(ctx->curve_id, ctx->ndigits,
-			     priv, params.key_size) < 0) {
+			     ctx->private_key, params.key_size) < 0) {
 		memzero_explicit(ctx->private_key, params.key_size);
 		ret = -EINVAL;
 	}
-	memzero_explicit(priv, sizeof(priv));
 
 	return ret;
 }