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54 lines
2.0 KiB
Diff
54 lines
2.0 KiB
Diff
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From 8ad8585f91823ddcc3728155e288e0f9f872e31a Mon Sep 17 00:00:00 2001
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From: Mathy Vanhoef <mathy.vanhoef@nyu.edu>
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Date: Sun, 31 Mar 2019 17:43:44 +0200
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Subject: [PATCH 13/14] EAP-pwd client: Verify received scalar and element
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When processing an EAP-pwd Commit frame, the server's scalar and element
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(elliptic curve point) were not validated. This allowed an adversary to
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bypass authentication, and act as a rogue Access Point (AP) if the
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crypto implementation did not verify the validity of the EC point.
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Fix this vulnerability by assuring the received scalar lies within the
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valid range, and by checking that the received element is not the point
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at infinity and lies on the elliptic curve being used. (CVE-2019-9499)
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The vulnerability is only exploitable if OpenSSL version 1.0.2 or lower
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is used, or if LibreSSL or wolfssl is used. Newer versions of OpenSSL
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(and also BoringSSL) implicitly validate the elliptic curve point in
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EC_POINT_set_affine_coordinates_GFp(), preventing the attack.
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Signed-off-by: Mathy Vanhoef <mathy.vanhoef@nyu.edu>
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---
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src/eap_peer/eap_pwd.c | 20 ++++++++++++++++++++
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1 file changed, 20 insertions(+)
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--- a/src/eap_peer/eap_pwd.c
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+++ b/src/eap_peer/eap_pwd.c
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@@ -594,6 +594,26 @@ eap_pwd_perform_commit_exchange(struct e
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goto fin;
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}
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+ /* verify received scalar */
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+ if (crypto_bignum_is_zero(data->server_scalar) ||
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+ crypto_bignum_is_one(data->server_scalar) ||
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+ crypto_bignum_cmp(data->server_scalar,
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+ crypto_ec_get_order(data->grp->group)) >= 0) {
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+ wpa_printf(MSG_INFO,
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+ "EAP-PWD (peer): received scalar is invalid");
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+ goto fin;
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+ }
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+
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+ /* verify received element */
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+ if (!crypto_ec_point_is_on_curve(data->grp->group,
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+ data->server_element) ||
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+ crypto_ec_point_is_at_infinity(data->grp->group,
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+ data->server_element)) {
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+ wpa_printf(MSG_INFO,
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+ "EAP-PWD (peer): received element is invalid");
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+ goto fin;
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+ }
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+
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/* check to ensure server's element is not in a small sub-group */
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if (!crypto_bignum_is_one(cofactor)) {
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if (crypto_ec_point_mul(data->grp->group, data->server_element,
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