59 lines
2.2 KiB
Diff
59 lines
2.2 KiB
Diff
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From 70ff850e89fbc8bc7da515321b4d15b5eef70581 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 17:13:06 +0200
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Subject: [PATCH 11/14] EAP-pwd server: Verify received scalar and element
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When processing an EAP-pwd Commit frame, the peer'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 impersonate any user if the crypto
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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-2019-9498)
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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_server/eap_server_pwd.c | 20 ++++++++++++++++++++
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1 file changed, 20 insertions(+)
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diff --git a/src/eap_server/eap_server_pwd.c b/src/eap_server/eap_server_pwd.c
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index d0fa54a..74979da 100644
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--- a/src/eap_server/eap_server_pwd.c
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+++ b/src/eap_server/eap_server_pwd.c
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@@ -718,6 +718,26 @@ eap_pwd_process_commit_resp(struct eap_sm *sm, struct eap_pwd_data *data,
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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->peer_scalar) ||
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+ crypto_bignum_is_one(data->peer_scalar) ||
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+ crypto_bignum_cmp(data->peer_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 (server): 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->peer_element) ||
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+ crypto_ec_point_is_at_infinity(data->grp->group,
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+ data->peer_element)) {
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+ wpa_printf(MSG_INFO,
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+ "EAP-PWD (server): 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 peer'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->peer_element,
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--
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2.7.4
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