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s390x assembly pack: process x25519 and x448 non-canonical values

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...in constant time.

Signed-off-by: Patrick Steuer <patrick.steuer@de.ibm.com>

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/10339)
This commit is contained in:
Patrick Steuer 2019-11-03 00:32:04 +01:00
parent 6376c229c4
commit 677c4a012a
2 changed files with 37 additions and 8 deletions
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17
crypto/ec/ecx_meth.c
View File

@ -854,6 +854,7 @@ static const EVP_PKEY_METHOD ed448_pkey_meth = {
#ifdef S390X_EC_ASM
# include "s390x_arch.h"
# include "internal/constant_time.h"
static void s390x_x25519_mod_p(unsigned char u[32])
{
@ -867,16 +868,16 @@ static void s390x_x25519_mod_p(unsigned char u[32])
u_red[31] = (unsigned char)c;
c >>= 8;
for (i = 30; c > 0 && i >= 0; i--) {
for (i = 30; i >= 0; i--) {
c += (unsigned int)u_red[i];
u_red[i] = (unsigned char)c;
c >>= 8;
}
if (u_red[0] & 0x80) {
u_red[0] &= 0x7f;
memcpy(u, u_red, sizeof(u_red));
}
c = (u_red[0] & 0x80) >> 7;
u_red[0] &= 0x7f;
constant_time_cond_swap_buff(0 - (unsigned char)c,
u, u_red, sizeof(u_red));
}
static void s390x_x448_mod_p(unsigned char u[56])
@ -901,14 +902,14 @@ static void s390x_x448_mod_p(unsigned char u[56])
u_red[27] = (unsigned char)c;
c >>= 8;
for (i = 26; c > 0 && i >= 0; i--) {
for (i = 26; i >= 0; i--) {
c += (unsigned int)u_red[i];
u_red[i] = (unsigned char)c;
c >>= 8;
}
if (c)
memcpy(u, u_red, sizeof(u_red));
constant_time_cond_swap_buff(0 - (unsigned char)c,
u, u_red, sizeof(u_red));
}
static int s390x_x25519_mul(unsigned char u_dst[32],

28
include/internal/constant_time.h
View File

@ -352,6 +352,34 @@ static ossl_inline void constant_time_cond_swap_64(uint64_t mask, uint64_t *a,
*b ^= xor;
}
/*
* mask must be 0xFF or 0x00.
* "constant time" is per len.
*
* if (mask) {
* unsigned char tmp[len];
*
* memcpy(tmp, a, len);
* memcpy(a, b);
* memcpy(b, tmp);
* }
*/
static ossl_inline void constant_time_cond_swap_buff(unsigned char mask,
unsigned char *a,
unsigned char *b,
size_t len)
{
size_t i;
unsigned char tmp;
for (i = 0; i < len; i++) {
tmp = a[i] ^ b[i];
tmp &= mask;
a[i] ^= tmp;
b[i] ^= tmp;
}
}
/*
* table is a two dimensional array of bytes. Each row has rowsize elements.
* Copies row number idx into out. rowsize and numrows are not considered