[src/trunk]: src/external/bsd/wpa/dist/src/eap_peer When processing an EAP-pw...

[christos <christos%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/8d19c61d5eac
branches:  trunk
changeset: 455701:8d19c61d5eac
user:      christos <christos%NetBSD.org@localhost>
date:      Wed Apr 10 17:49:59 2019 +0000

description:
When processing an EAP-pwd Commit frame, the server's scalar and element
(elliptic curve point) were not validated. This allowed an adversary to
bypass authentication, and act as a rogue Access Point (AP) 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-2019-9499)

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.

diffstat:

 external/bsd/wpa/dist/src/eap_peer/eap_pwd.c |  20 ++++++++++++++++++++
 1 files changed, 20 insertions(+), 0 deletions(-)

diffs (30 lines):

diff -r ebd095271736 -r 8d19c61d5eac external/bsd/wpa/dist/src/eap_peer/eap_pwd.c
--- a/external/bsd/wpa/dist/src/eap_peer/eap_pwd.c      Wed Apr 10 17:49:26 2019 +0000
+++ b/external/bsd/wpa/dist/src/eap_peer/eap_pwd.c      Wed Apr 10 17:49:59 2019 +0000
@@ -594,6 +594,26 @@
                goto fin;
        }
 
+       /* verify received scalar */
+       if (crypto_bignum_is_zero(data->server_scalar) ||
+           crypto_bignum_is_one(data->server_scalar) ||
+           crypto_bignum_cmp(data->server_scalar,
+                             crypto_ec_get_order(data->grp->group)) >= 0) {
+               wpa_printf(MSG_INFO,
+                          "EAP-PWD (peer): received scalar is invalid");
+               goto fin;
+       }
+
+       /* verify received element */
+       if (!crypto_ec_point_is_on_curve(data->grp->group,
+                                        data->server_element) ||
+           crypto_ec_point_is_at_infinity(data->grp->group,
+                                          data->server_element)) {
+               wpa_printf(MSG_INFO,
+                          "EAP-PWD (peer): received element is invalid");
+               goto fin;
+       }
+
        /* check to ensure server's element is not in a small sub-group */
        if (!crypto_bignum_is_one(cofactor)) {
                if (crypto_ec_point_mul(data->grp->group, data->server_element,