summaryrefslogtreecommitdiff
path: root/net/bridge/br_fdb.c
diff options
context:
space:
mode:
authorHans J. Schultz <netdev@kapio-technology.com>2022-11-01 22:39:21 +0300
committerJakub Kicinski <kuba@kernel.org>2022-11-04 06:46:32 +0300
commita35ec8e38cdd1766f29924ca391a01de20163931 (patch)
tree69e818805df919167194d8de8da7cc69a4262fb9 /net/bridge/br_fdb.c
parentfbeb229a6622523c092a13c02bd0e15f69240dde (diff)
downloadlinux-a35ec8e38cdd1766f29924ca391a01de20163931.tar.xz
bridge: Add MAC Authentication Bypass (MAB) support
Hosts that support 802.1X authentication are able to authenticate themselves by exchanging EAPOL frames with an authenticator (Ethernet bridge, in this case) and an authentication server. Access to the network is only granted by the authenticator to successfully authenticated hosts. The above is implemented in the bridge using the "locked" bridge port option. When enabled, link-local frames (e.g., EAPOL) can be locally received by the bridge, but all other frames are dropped unless the host is authenticated. That is, unless the user space control plane installed an FDB entry according to which the source address of the frame is located behind the locked ingress port. The entry can be dynamic, in which case learning needs to be enabled so that the entry will be refreshed by incoming traffic. There are deployments in which not all the devices connected to the authenticator (the bridge) support 802.1X. Such devices can include printers and cameras. One option to support such deployments is to unlock the bridge ports connecting these devices, but a slightly more secure option is to use MAB. When MAB is enabled, the MAC address of the connected device is used as the user name and password for the authentication. For MAB to work, the user space control plane needs to be notified about MAC addresses that are trying to gain access so that they will be compared against an allow list. This can be implemented via the regular learning process with the sole difference that learned FDB entries are installed with a new "locked" flag indicating that the entry cannot be used to authenticate the device. The flag cannot be set by user space, but user space can clear the flag by replacing the entry, thereby authenticating the device. Locked FDB entries implement the following semantics with regards to roaming, aging and forwarding: 1. Roaming: Locked FDB entries can roam to unlocked (authorized) ports, in which case the "locked" flag is cleared. FDB entries cannot roam to locked ports regardless of MAB being enabled or not. Therefore, locked FDB entries are only created if an FDB entry with the given {MAC, VID} does not already exist. This behavior prevents unauthenticated devices from disrupting traffic destined to already authenticated devices. 2. Aging: Locked FDB entries age and refresh by incoming traffic like regular entries. 3. Forwarding: Locked FDB entries forward traffic like regular entries. If user space detects an unauthorized MAC behind a locked port and wishes to prevent traffic with this MAC DA from reaching the host, it can do so using tc or a different mechanism. Enable the above behavior using a new bridge port option called "mab". It can only be enabled on a bridge port that is both locked and has learning enabled. Locked FDB entries are flushed from the port once MAB is disabled. A new option is added because there are pure 802.1X deployments that are not interested in notifications about locked FDB entries. Signed-off-by: Hans J. Schultz <netdev@kapio-technology.com> Signed-off-by: Ido Schimmel <idosch@nvidia.com> Acked-by: Nikolay Aleksandrov <razor@blackwall.org> Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net/bridge/br_fdb.c')
-rw-r--r--net/bridge/br_fdb.c24
1 files changed, 24 insertions, 0 deletions
diff --git a/net/bridge/br_fdb.c b/net/bridge/br_fdb.c
index e7f4fccb6adb..3b83af4458b8 100644
--- a/net/bridge/br_fdb.c
+++ b/net/bridge/br_fdb.c
@@ -105,6 +105,7 @@ static int fdb_fill_info(struct sk_buff *skb, const struct net_bridge *br,
struct nda_cacheinfo ci;
struct nlmsghdr *nlh;
struct ndmsg *ndm;
+ u32 ext_flags = 0;
nlh = nlmsg_put(skb, portid, seq, type, sizeof(*ndm), flags);
if (nlh == NULL)
@@ -125,11 +126,16 @@ static int fdb_fill_info(struct sk_buff *skb, const struct net_bridge *br,
ndm->ndm_flags |= NTF_EXT_LEARNED;
if (test_bit(BR_FDB_STICKY, &fdb->flags))
ndm->ndm_flags |= NTF_STICKY;
+ if (test_bit(BR_FDB_LOCKED, &fdb->flags))
+ ext_flags |= NTF_EXT_LOCKED;
if (nla_put(skb, NDA_LLADDR, ETH_ALEN, &fdb->key.addr))
goto nla_put_failure;
if (nla_put_u32(skb, NDA_MASTER, br->dev->ifindex))
goto nla_put_failure;
+ if (nla_put_u32(skb, NDA_FLAGS_EXT, ext_flags))
+ goto nla_put_failure;
+
ci.ndm_used = jiffies_to_clock_t(now - fdb->used);
ci.ndm_confirmed = 0;
ci.ndm_updated = jiffies_to_clock_t(now - fdb->updated);
@@ -171,6 +177,7 @@ static inline size_t fdb_nlmsg_size(void)
return NLMSG_ALIGN(sizeof(struct ndmsg))
+ nla_total_size(ETH_ALEN) /* NDA_LLADDR */
+ nla_total_size(sizeof(u32)) /* NDA_MASTER */
+ + nla_total_size(sizeof(u32)) /* NDA_FLAGS_EXT */
+ nla_total_size(sizeof(u16)) /* NDA_VLAN */
+ nla_total_size(sizeof(struct nda_cacheinfo))
+ nla_total_size(0) /* NDA_FDB_EXT_ATTRS */
@@ -879,6 +886,11 @@ void br_fdb_update(struct net_bridge *br, struct net_bridge_port *source,
&fdb->flags)))
clear_bit(BR_FDB_ADDED_BY_EXT_LEARN,
&fdb->flags);
+ /* Clear locked flag when roaming to an
+ * unlocked port.
+ */
+ if (unlikely(test_bit(BR_FDB_LOCKED, &fdb->flags)))
+ clear_bit(BR_FDB_LOCKED, &fdb->flags);
}
if (unlikely(test_bit(BR_FDB_ADDED_BY_USER, &flags)))
@@ -1082,6 +1094,9 @@ static int fdb_add_entry(struct net_bridge *br, struct net_bridge_port *source,
modified = true;
}
+ if (test_and_clear_bit(BR_FDB_LOCKED, &fdb->flags))
+ modified = true;
+
if (fdb_handle_notify(fdb, notify))
modified = true;
@@ -1150,6 +1165,7 @@ int br_fdb_add(struct ndmsg *ndm, struct nlattr *tb[],
struct net_bridge_port *p = NULL;
struct net_bridge_vlan *v;
struct net_bridge *br = NULL;
+ u32 ext_flags = 0;
int err = 0;
trace_br_fdb_add(ndm, dev, addr, vid, nlh_flags);
@@ -1178,6 +1194,14 @@ int br_fdb_add(struct ndmsg *ndm, struct nlattr *tb[],
vg = nbp_vlan_group(p);
}
+ if (tb[NDA_FLAGS_EXT])
+ ext_flags = nla_get_u32(tb[NDA_FLAGS_EXT]);
+
+ if (ext_flags & NTF_EXT_LOCKED) {
+ NL_SET_ERR_MSG_MOD(extack, "Cannot add FDB entry with \"locked\" flag set");
+ return -EINVAL;
+ }
+
if (tb[NDA_FDB_EXT_ATTRS]) {
attr = tb[NDA_FDB_EXT_ATTRS];
err = nla_parse_nested(nfea_tb, NFEA_MAX, attr,