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From d89edb6112f54fb65036c31eba291bda5fcad2b3 Mon Sep 17 00:00:00 2001
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Message-Id: <d89edb6112f54fb65036c31eba291bda5fcad2b3.1522770749.git.davide.caratti@gmail.com>
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From: Davide Caratti <davide.caratti@gmail.com>
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Date: Wed, 28 Mar 2018 16:34:56 +0200
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Subject: [PATCH] wpa_supplicant: Don't reply to EAPOL if pkt_type is
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PACKET_OTHERHOST
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When wpa_supplicant is running on a Linux interface that is configured in
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promiscuous mode, and it is not a member of a bridge, incoming EAPOL
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packets are processed regardless of the Destination Address in the frame.
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As a consequence, there are situations where wpa_supplicant replies to
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EAPOL packets that are not destined for it.
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This behavior seems undesired (see IEEE Std 802.1X-2010, 11.4.a), and can
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be avoided by attaching a BPF filter that lets the kernel discard packets
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having pkt_type equal to PACKET_OTHERHOST.
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Signed-off-by: Davide Caratti <davide.caratti@gmail.com>
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---
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src/l2_packet/l2_packet.h | 1 +
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src/l2_packet/l2_packet_linux.c | 23 +++++++++++++++++++++++
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wpa_supplicant/wpa_supplicant.c | 5 +++++
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3 files changed, 29 insertions(+)
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diff --git a/src/l2_packet/l2_packet.h b/src/l2_packet/l2_packet.h
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index 2a4524582..53871774b 100644
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--- a/src/l2_packet/l2_packet.h
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+++ b/src/l2_packet/l2_packet.h
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@@ -42,6 +42,7 @@ struct l2_ethhdr {
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enum l2_packet_filter_type {
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L2_PACKET_FILTER_DHCP,
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L2_PACKET_FILTER_NDISC,
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+ L2_PACKET_FILTER_PKTTYPE,
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};
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/**
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diff --git a/src/l2_packet/l2_packet_linux.c b/src/l2_packet/l2_packet_linux.c
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index 65b490679..291c9dd26 100644
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--- a/src/l2_packet/l2_packet_linux.c
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+++ b/src/l2_packet/l2_packet_linux.c
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@@ -84,6 +84,26 @@ static const struct sock_fprog ndisc_sock_filter = {
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.filter = ndisc_sock_filter_insns,
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};
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+/* drop packet if skb->pkt_type is PACKET_OTHERHOST (0x03). Generated by:
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+ * $ bpfc - <
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+ * > ldb #type
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+ * > jeq #0x03, drop
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+ * > pass: ret #-1
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+ * > drop: ret #0
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+ * > EOF
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+ */
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+static struct sock_filter pkt_type_filter_insns[] = {
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+ { 0x30, 0, 0, 0xfffff004 },
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+ { 0x15, 1, 0, 0x00000003 },
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+ { 0x6, 0, 0, 0xffffffff },
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+ { 0x6, 0, 0, 0x00000000 },
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+};
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+
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+static const struct sock_fprog pkt_type_sock_filter = {
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+ .len = ARRAY_SIZE(pkt_type_filter_insns),
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+ .filter = pkt_type_filter_insns,
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+};
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+
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int l2_packet_get_own_addr(struct l2_packet_data *l2, u8 *addr)
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{
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@@ -471,6 +491,9 @@ int l2_packet_set_packet_filter(struct l2_packet_data *l2,
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case L2_PACKET_FILTER_NDISC:
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sock_filter = &ndisc_sock_filter;
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break;
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+ case L2_PACKET_FILTER_PKTTYPE:
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+ sock_filter = &pkt_type_sock_filter;
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+ break;
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default:
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return -1;
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}
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diff --git a/wpa_supplicant/wpa_supplicant.c b/wpa_supplicant/wpa_supplicant.c
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index 2a05ef910..dcec68a03 100644
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--- a/wpa_supplicant/wpa_supplicant.c
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+++ b/wpa_supplicant/wpa_supplicant.c
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@@ -4014,6 +4014,11 @@ int wpa_supplicant_update_mac_addr(struct wpa_supplicant *wpa_s)
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wpa_supplicant_rx_eapol, wpa_s, 0);
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if (wpa_s->l2 == NULL)
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return -1;
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+
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+ if (l2_packet_set_packet_filter(wpa_s->l2,
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+ L2_PACKET_FILTER_PKTTYPE))
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+ wpa_dbg(wpa_s, MSG_DEBUG,
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+ "Failed to attach pkt_type filter");
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} else {
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const u8 *addr = wpa_drv_get_mac_addr(wpa_s);
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if (addr)
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--
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2.14.3
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