* limitations under the License.
*/
+/*
+ * ECDSA low level APIs are deprecated for public use, but still ok for
+ * internal use.
+ */
+#include "internal/deprecated.h"
+
/*
* A 64-bit implementation of the NIST P-256 elliptic curve point multiplication
*
# include <stdint.h>
# include <string.h>
# include <openssl/err.h>
-# include "ec_lcl.h"
+# include "ec_local.h"
# if defined(__SIZEOF_INT128__) && __SIZEOF_INT128__==16
/* even with gcc, the typedef won't work for 32-bit platforms */
*((u64 *)&out[24]) = in[3];
}
-/* To preserve endianness when using BN_bn2bin and BN_bin2bn */
-static void flip_endian(u8 *out, const u8 *in, unsigned len)
-{
- unsigned i;
- for (i = 0; i < len; ++i)
- out[i] = in[len - 1 - i];
-}
-
/* BN_to_felem converts an OpenSSL BIGNUM into an felem */
static int BN_to_felem(felem out, const BIGNUM *bn)
{
- felem_bytearray b_in;
felem_bytearray b_out;
- unsigned num_bytes;
+ int num_bytes;
- /* BN_bn2bin eats leading zeroes */
- memset(b_out, 0, sizeof(b_out));
- num_bytes = BN_num_bytes(bn);
- if (num_bytes > sizeof(b_out)) {
+ if (BN_is_negative(bn)) {
ECerr(EC_F_BN_TO_FELEM, EC_R_BIGNUM_OUT_OF_RANGE);
return 0;
}
- if (BN_is_negative(bn)) {
+ num_bytes = BN_bn2lebinpad(bn, b_out, sizeof(b_out));
+ if (num_bytes < 0) {
ECerr(EC_F_BN_TO_FELEM, EC_R_BIGNUM_OUT_OF_RANGE);
return 0;
}
- num_bytes = BN_bn2bin(bn, b_in);
- flip_endian(b_out, b_in, num_bytes);
bin32_to_felem(out, b_out);
return 1;
}
/* felem_to_BN converts an felem into an OpenSSL BIGNUM */
static BIGNUM *smallfelem_to_BN(BIGNUM *out, const smallfelem in)
{
- felem_bytearray b_in, b_out;
- smallfelem_to_bin32(b_in, in);
- flip_endian(b_out, b_in, sizeof(b_out));
- return BN_bin2bn(b_out, sizeof(b_out), out);
+ felem_bytearray b_out;
+ smallfelem_to_bin32(b_out, in);
+ return BN_lebin2bn(b_out, sizeof(b_out), out);
}
/*-
longfelem tmp, tmp2;
smallfelem small1, small2, small3, small4, small5;
limb x_equal, y_equal, z1_is_zero, z2_is_zero;
+ limb points_equal;
felem_shrink(small3, z1);
felem_shrink(small1, ftmp5);
y_equal = smallfelem_is_zero(small1);
- if (x_equal && y_equal && !z1_is_zero && !z2_is_zero) {
+ /*
+ * The formulae are incorrect if the points are equal, in affine coordinates
+ * (X_1, Y_1) == (X_2, Y_2), so we check for this and do doubling if this
+ * happens.
+ *
+ * We use bitwise operations to avoid potential side-channels introduced by
+ * the short-circuiting behaviour of boolean operators.
+ *
+ * The special case of either point being the point at infinity (z1 and/or
+ * z2 are zero), is handled separately later on in this function, so we
+ * avoid jumping to point_double here in those special cases.
+ */
+ points_equal = (x_equal & y_equal & (~z1_is_zero) & (~z2_is_zero));
+
+ if (points_equal) {
+ /*
+ * This is obviously not constant-time but, as mentioned before, this
+ * case never happens during single point multiplication, so there is no
+ * timing leak for ECDH or ECDSA signing.
+ */
point_double(x3, y3, z3, x1, y1, z1);
return;
}
felem_bytearray *secrets = NULL;
smallfelem (*pre_comp)[17][3] = NULL;
smallfelem *tmp_smallfelems = NULL;
- felem_bytearray tmp;
- unsigned i, num_bytes;
+ unsigned i;
+ int num_bytes;
int have_pre_comp = 0;
size_t num_points = num;
smallfelem x_in, y_in, z_in;
memset(secrets, 0, sizeof(*secrets) * num_points);
memset(pre_comp, 0, sizeof(*pre_comp) * num_points);
for (i = 0; i < num_points; ++i) {
- if (i == num)
+ if (i == num) {
/*
* we didn't have a valid precomputation, so we pick the
* generator
*/
- {
p = EC_GROUP_get0_generator(group);
p_scalar = scalar;
- } else
+ } else {
/* the i^th point */
- {
p = points[i];
p_scalar = scalars[i];
}
ECerr(EC_F_EC_GFP_NISTP256_POINTS_MUL, ERR_R_BN_LIB);
goto err;
}
- num_bytes = BN_bn2bin(tmp_scalar, tmp);
- } else
- num_bytes = BN_bn2bin(p_scalar, tmp);
- flip_endian(secrets[i], tmp, num_bytes);
+ num_bytes = BN_bn2lebinpad(tmp_scalar,
+ secrets[i], sizeof(secrets[i]));
+ } else {
+ num_bytes = BN_bn2lebinpad(p_scalar,
+ secrets[i], sizeof(secrets[i]));
+ }
+ if (num_bytes < 0) {
+ ECerr(EC_F_EC_GFP_NISTP256_POINTS_MUL, ERR_R_BN_LIB);
+ goto err;
+ }
/* precompute multiples */
if ((!BN_to_felem(x_out, p->X)) ||
(!BN_to_felem(y_out, p->Y)) ||
ECerr(EC_F_EC_GFP_NISTP256_POINTS_MUL, ERR_R_BN_LIB);
goto err;
}
- num_bytes = BN_bn2bin(tmp_scalar, tmp);
- } else
- num_bytes = BN_bn2bin(scalar, tmp);
- flip_endian(g_secret, tmp, num_bytes);
+ num_bytes = BN_bn2lebinpad(tmp_scalar, g_secret, sizeof(g_secret));
+ } else {
+ num_bytes = BN_bn2lebinpad(scalar, g_secret, sizeof(g_secret));
+ }
/* do the multiplication with generator precomputation */
batch_mul(x_out, y_out, z_out,
(const felem_bytearray(*))secrets, num_points,
g_secret,
mixed, (const smallfelem(*)[17][3])pre_comp, g_pre_comp);
- } else
+ } else {
/* do the multiplication without generator precomputation */
batch_mul(x_out, y_out, z_out,
(const felem_bytearray(*))secrets, num_points,
NULL, mixed, (const smallfelem(*)[17][3])pre_comp, NULL);
+ }
/* reduce the output to its unique minimal representation */
felem_contract(x_in, x_out);
felem_contract(y_in, y_out);
projects / openssl.git / blobdiff