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authorMathy Vanhoef <mathy.vanhoef@nyu.edu>2019-03-31 15:13:06 (GMT)
committerJouni Malinen <j@w1.fi>2019-04-09 14:11:15 (GMT)
commit70ff850e89fbc8bc7da515321b4d15b5eef70581 (patch)
treed618db98c2fa036c31bf9f6a59a0f9a6a5fcf1d8
parentac8fa9ef198640086cf2ce7c94673be2b6a018a0 (diff)
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EAP-pwd server: Verify received scalar and element
When processing an EAP-pwd Commit frame, the peer's scalar and element (elliptic curve point) were not validated. This allowed an adversary to bypass authentication, and impersonate any user if the crypto implementation did not verify the validity of the EC point. Fix this vulnerability by assuring the received scalar lies within the valid range, and by checking that the received element is not the point at infinity and lies on the elliptic curve being used. (CVE-2019-9498) The vulnerability is only exploitable if OpenSSL version 1.0.2 or lower is used, or if LibreSSL or wolfssl is used. Newer versions of OpenSSL (and also BoringSSL) implicitly validate the elliptic curve point in EC_POINT_set_affine_coordinates_GFp(), preventing the attack. Signed-off-by: Mathy Vanhoef <mathy.vanhoef@nyu.edu>
-rw-r--r--src/eap_server/eap_server_pwd.c20
1 files changed, 20 insertions, 0 deletions
diff --git a/src/eap_server/eap_server_pwd.c b/src/eap_server/eap_server_pwd.c
index d0fa54a..74979da 100644
--- a/src/eap_server/eap_server_pwd.c
+++ b/src/eap_server/eap_server_pwd.c
@@ -718,6 +718,26 @@ eap_pwd_process_commit_resp(struct eap_sm *sm, struct eap_pwd_data *data,
goto fin;
}
+ /* verify received scalar */
+ if (crypto_bignum_is_zero(data->peer_scalar) ||
+ crypto_bignum_is_one(data->peer_scalar) ||
+ crypto_bignum_cmp(data->peer_scalar,
+ crypto_ec_get_order(data->grp->group)) >= 0) {
+ wpa_printf(MSG_INFO,
+ "EAP-PWD (server): received scalar is invalid");
+ goto fin;
+ }
+
+ /* verify received element */
+ if (!crypto_ec_point_is_on_curve(data->grp->group,
+ data->peer_element) ||
+ crypto_ec_point_is_at_infinity(data->grp->group,
+ data->peer_element)) {
+ wpa_printf(MSG_INFO,
+ "EAP-PWD (server): received element is invalid");
+ goto fin;
+ }
+
/* check to ensure peer's element is not in a small sub-group */
if (!crypto_bignum_is_one(cofactor)) {
if (crypto_ec_point_mul(data->grp->group, data->peer_element,