The point type was being hard coded to 0x3 (BIT1) which may have resulted in the peer subtracting Y from P when reading in the point (depending on if Y was odd or not). Instead set the compressed type to whatever avoids the subtraction which both saves IWD from needing to do it, as well as the peer. --- src/dpp-util.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) diff --git a/src/dpp-util.c b/src/dpp-util.c index 048009c4..a643beb1 100644 --- a/src/dpp-util.c +++ b/src/dpp-util.c @@ -728,6 +728,7 @@ uint8_t *dpp_point_to_asn1(const struct l_ecc_point *p, size_t *len_out) uint64_t x[L_ECC_MAX_DIGITS]; ssize_t ret; size_t len; + uint8_t point_type; switch (key_size) { case 32: @@ -744,6 +745,17 @@ uint8_t *dpp_point_to_asn1(const struct l_ecc_point *p, size_t *len_out) if (ret < 0 || ret != key_size) return NULL; + /* + * Set the type to whatever avoids doing p - y when reading in the + * key. Working backwards from l_ecc_point_from_data if Y is odd and + * the type is BIT0 there is no subtraction. Similarly if Y is even + * and the type is BIT1. + */ + if (l_ecc_point_y_isodd(p)) + point_type = L_ECC_POINT_TYPE_COMPRESSED_BIT0; + else + point_type = L_ECC_POINT_TYPE_COMPRESSED_BIT1; + len = 2 + ec_oid.asn1_len + 2 + key_type->asn1_len + 2 + key_size + 4; if (L_WARN_ON(len > 128)) @@ -775,7 +787,7 @@ uint8_t *dpp_point_to_asn1(const struct l_ecc_point *p, size_t *len_out) *ptr++ = ASN1_ID_BIT_STRING; *ptr++ = key_size + 2; *ptr++ = 0x00; - *ptr++ = 0x03; + *ptr++ = point_type; memcpy(ptr, x, key_size); ptr += key_size; -- 2.31.1