diff options
| author | Denys Vlasenko <vda.linux@googlemail.com> | 2021-11-27 18:07:42 +0300 |
|---|---|---|
| committer | Denys Vlasenko <vda.linux@googlemail.com> | 2021-11-27 18:24:49 +0300 |
| commit | dcfd8d3d1013ba989fa511f44bb0553a88c1ef10 (patch) | |
| tree | 60daf7a0b94df58752928f8f3f0ac3f80fe0ed02 | |
| parent | 8cbb70365f653397c8c2b9370214d5aed36ec9fa (diff) | |
tls: P256: fix sp_256_div2_8 - it wouldn't use a[] if low bit is 0
It worked by chance because the only caller passed both parameters
as two pointers to the same array.
My fault (I made this error when converting from 26-bit code).
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
| -rw-r--r-- | networking/tls_sp_c32.c | 12 |
1 files changed, 7 insertions, 5 deletions
diff --git a/networking/tls_sp_c32.c b/networking/tls_sp_c32.c index baed62f41..b3f7888f5 100644 --- a/networking/tls_sp_c32.c +++ b/networking/tls_sp_c32.c @@ -636,12 +636,14 @@ static void sp_256_rshift1_8(sp_digit* r, sp_digit carry) } #endif -/* Divide the number by 2 mod the modulus (prime). (r = a / 2 % m) */ -static void sp_256_div2_8(sp_digit* r, const sp_digit* a, const sp_digit* m) +/* Divide the number by 2 mod the modulus (prime). (r = (r / 2) % m) */ +static void sp_256_div2_8(sp_digit* r /*, const sp_digit* m*/) { + const sp_digit* m = p256_mod; + int carry = 0; - if (a[0] & 1) - carry = sp_256_add_8(r, a, m); + if (r[0] & 1) + carry = sp_256_add_8(r, r, m); sp_256_norm_8(r); sp_256_rshift1_8(r, carry); } @@ -1125,7 +1127,7 @@ static void sp_256_proj_point_dbl_8(sp_point* r, sp_point* p) /* T2 = Y * Y */ sp_256to512z_mont_sqr_8(t2, r->y /*, p256_mod, p256_mp_mod*/); /* T2 = T2/2 */ - sp_256_div2_8(t2, t2, p256_mod); + sp_256_div2_8(t2 /*, p256_mod*/); /* Y = Y * X */ sp_256to512z_mont_mul_8(r->y, r->y, r->x /*, p256_mod, p256_mp_mod*/); /* X = T1 * T1 */ |