diff --git a/ssl/record/tls_pad.c b/ssl/record/tls_pad.c index e559350461..7311c8266a 100644 --- a/ssl/record/tls_pad.c +++ b/ssl/record/tls_pad.c @@ -207,6 +207,7 @@ static int ssl3_cbc_copy_mac(size_t *reclen, #if defined(CBC_MAC_ROTATE_IN_PLACE) unsigned char rotated_mac_buf[64 + EVP_MAX_MD_SIZE]; unsigned char *rotated_mac; + char aux1, aux2, aux3, mask; #else unsigned char rotated_mac[EVP_MAX_MD_SIZE]; #endif @@ -288,12 +289,19 @@ static int ssl3_cbc_copy_mac(size_t *reclen, #if defined(CBC_MAC_ROTATE_IN_PLACE) j = 0; for (i = 0; i < mac_size; i++) { - /* in case cache-line is 32 bytes, touch second line */ - ((volatile unsigned char *)rotated_mac)[rotate_offset ^ 32]; + /* + * in case cache-line is 32 bytes, + * load from both lines and select appropriately + */ + aux1 = rotated_mac[rotate_offset & ~32]; + aux2 = rotated_mac[rotate_offset | 32]; + mask = constant_time_eq_8(rotate_offset & ~32, rotate_offset); + aux3 = constant_time_select_8(mask, aux1, aux2); + rotate_offset++; /* If the padding wasn't good we emit a random MAC */ out[j++] = constant_time_select_8((unsigned char)(good & 0xff), - rotated_mac[rotate_offset++], + aux3, randmac[i]); rotate_offset &= constant_time_lt_s(rotate_offset, mac_size); }