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macsec: Support XPN frame handling - IEEE 802.1AEbw
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Support extended packet number cipher suites (802.1AEbw) frames handling.
This does not include the needed netlink patches.

    * Added xpn boolean field to `struct macsec_secy`.
    * Added ssci field to `struct_macsec_tx_sa` (802.1AE figure 10-5).
    * Added ssci field to `struct_macsec_rx_sa` (802.1AE figure 10-5).
    * Added salt field to `struct macsec_key` (802.1AE 10.7 NOTE 1).
    * Created pn_t type for easy access to lower and upper halves.
    * Created salt_t type for easy access to the "ssci" and "pn" parts.
    * Created `macsec_fill_iv_xpn` function to create IV in XPN mode.
    * Support in PN recovery and preliminary replay check in XPN mode.

In addition, according to IEEE 802.1AEbw figure 10-5, the PN of incoming
frame can be 0 when XPN cipher suite is used, so fixed the function
`macsec_validate_skb` to fail on PN=0 only if XPN is off.

Signed-off-by: Era Mayflower <mayflowerera@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Era Mayflower authored and David S. Miller committed Mar 16, 2020
1 parent 65b7a2c commit a21ecf0
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Showing 2 changed files with 136 additions and 39 deletions.
130 changes: 94 additions & 36 deletions drivers/net/macsec.c
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@
#include <net/gro_cells.h>
#include <net/macsec.h>
#include <linux/phy.h>
#include <linux/byteorder/generic.h>

#include <uapi/linux/if_macsec.h>

Expand Down Expand Up @@ -68,6 +69,16 @@ struct macsec_eth_header {
sc; \
sc = rtnl_dereference(sc->next))

#define pn_same_half(pn1, pn2) (!(((pn1) >> 31) ^ ((pn2) >> 31)))

struct gcm_iv_xpn {
union {
u8 short_secure_channel_id[4];
ssci_t ssci;
};
__be64 pn;
} __packed;

struct gcm_iv {
union {
u8 secure_channel_id[8];
Expand Down Expand Up @@ -372,8 +383,8 @@ static const struct macsec_ops *macsec_get_ops(struct macsec_dev *macsec,
return __macsec_get_ops(macsec->offload, macsec, ctx);
}

/* validate MACsec packet according to IEEE 802.1AE-2006 9.12 */
static bool macsec_validate_skb(struct sk_buff *skb, u16 icv_len)
/* validate MACsec packet according to IEEE 802.1AE-2018 9.12 */
static bool macsec_validate_skb(struct sk_buff *skb, u16 icv_len, bool xpn)
{
struct macsec_eth_header *h = (struct macsec_eth_header *)skb->data;
int len = skb->len - 2 * ETH_ALEN;
Expand All @@ -398,8 +409,8 @@ static bool macsec_validate_skb(struct sk_buff *skb, u16 icv_len)
if (h->unused)
return false;

/* rx.pn != 0 (figure 10-5) */
if (!h->packet_number)
/* rx.pn != 0 if not XPN (figure 10-5 with 802.11AEbw-2013 amendment) */
if (!h->packet_number && !xpn)
return false;

/* length check, f) g) h) i) */
Expand All @@ -411,6 +422,15 @@ static bool macsec_validate_skb(struct sk_buff *skb, u16 icv_len)
#define MACSEC_NEEDED_HEADROOM (macsec_extra_len(true))
#define MACSEC_NEEDED_TAILROOM MACSEC_STD_ICV_LEN

static void macsec_fill_iv_xpn(unsigned char *iv, ssci_t ssci, u64 pn,
salt_t salt)
{
struct gcm_iv_xpn *gcm_iv = (struct gcm_iv_xpn *)iv;

gcm_iv->ssci = ssci ^ salt.ssci;
gcm_iv->pn = cpu_to_be64(pn) ^ salt.pn;
}

static void macsec_fill_iv(unsigned char *iv, sci_t sci, u32 pn)
{
struct gcm_iv *gcm_iv = (struct gcm_iv *)iv;
Expand Down Expand Up @@ -446,14 +466,19 @@ void macsec_pn_wrapped(struct macsec_secy *secy, struct macsec_tx_sa *tx_sa)
}
EXPORT_SYMBOL_GPL(macsec_pn_wrapped);

static u32 tx_sa_update_pn(struct macsec_tx_sa *tx_sa, struct macsec_secy *secy)
static pn_t tx_sa_update_pn(struct macsec_tx_sa *tx_sa,
struct macsec_secy *secy)
{
u32 pn;
pn_t pn;

spin_lock_bh(&tx_sa->lock);
pn = tx_sa->next_pn;

tx_sa->next_pn++;
pn = tx_sa->next_pn_halves;
if (secy->xpn)
tx_sa->next_pn++;
else
tx_sa->next_pn_halves.lower++;

if (tx_sa->next_pn == 0)
__macsec_pn_wrapped(secy, tx_sa);
spin_unlock_bh(&tx_sa->lock);
Expand Down Expand Up @@ -568,7 +593,7 @@ static struct sk_buff *macsec_encrypt(struct sk_buff *skb,
struct macsec_tx_sa *tx_sa;
struct macsec_dev *macsec = macsec_priv(dev);
bool sci_present;
u32 pn;
pn_t pn;

secy = &macsec->secy;
tx_sc = &secy->tx_sc;
Expand Down Expand Up @@ -610,12 +635,12 @@ static struct sk_buff *macsec_encrypt(struct sk_buff *skb,
memmove(hh, eth, 2 * ETH_ALEN);

pn = tx_sa_update_pn(tx_sa, secy);
if (pn == 0) {
if (pn.full64 == 0) {
macsec_txsa_put(tx_sa);
kfree_skb(skb);
return ERR_PTR(-ENOLINK);
}
macsec_fill_sectag(hh, secy, pn, sci_present);
macsec_fill_sectag(hh, secy, pn.lower, sci_present);
macsec_set_shortlen(hh, unprotected_len - 2 * ETH_ALEN);

skb_put(skb, secy->icv_len);
Expand Down Expand Up @@ -646,7 +671,10 @@ static struct sk_buff *macsec_encrypt(struct sk_buff *skb,
return ERR_PTR(-ENOMEM);
}

macsec_fill_iv(iv, secy->sci, pn);
if (secy->xpn)
macsec_fill_iv_xpn(iv, tx_sa->ssci, pn.full64, tx_sa->key.salt);
else
macsec_fill_iv(iv, secy->sci, pn.lower);

sg_init_table(sg, ret);
ret = skb_to_sgvec(skb, sg, 0, skb->len);
Expand Down Expand Up @@ -698,13 +726,14 @@ static bool macsec_post_decrypt(struct sk_buff *skb, struct macsec_secy *secy, u
u32 lowest_pn = 0;

spin_lock(&rx_sa->lock);
if (rx_sa->next_pn >= secy->replay_window)
lowest_pn = rx_sa->next_pn - secy->replay_window;
if (rx_sa->next_pn_halves.lower >= secy->replay_window)
lowest_pn = rx_sa->next_pn_halves.lower - secy->replay_window;

/* Now perform replay protection check again
* (see IEEE 802.1AE-2006 figure 10-5)
*/
if (secy->replay_protect && pn < lowest_pn) {
if (secy->replay_protect && pn < lowest_pn &&
(!secy->xpn || pn_same_half(pn, lowest_pn))) {
spin_unlock(&rx_sa->lock);
u64_stats_update_begin(&rxsc_stats->syncp);
rxsc_stats->stats.InPktsLate++;
Expand Down Expand Up @@ -753,8 +782,15 @@ static bool macsec_post_decrypt(struct sk_buff *skb, struct macsec_secy *secy, u
}
u64_stats_update_end(&rxsc_stats->syncp);

if (pn >= rx_sa->next_pn)
rx_sa->next_pn = pn + 1;
// Instead of "pn >=" - to support pn overflow in xpn
if (pn + 1 > rx_sa->next_pn_halves.lower) {
rx_sa->next_pn_halves.lower = pn + 1;
} else if (secy->xpn &&
!pn_same_half(pn, rx_sa->next_pn_halves.lower)) {
rx_sa->next_pn_halves.upper++;
rx_sa->next_pn_halves.lower = pn + 1;
}

spin_unlock(&rx_sa->lock);
}

Expand Down Expand Up @@ -841,6 +877,7 @@ static struct sk_buff *macsec_decrypt(struct sk_buff *skb,
unsigned char *iv;
struct aead_request *req;
struct macsec_eth_header *hdr;
u32 hdr_pn;
u16 icv_len = secy->icv_len;

macsec_skb_cb(skb)->valid = false;
Expand All @@ -860,7 +897,21 @@ static struct sk_buff *macsec_decrypt(struct sk_buff *skb,
}

hdr = (struct macsec_eth_header *)skb->data;
macsec_fill_iv(iv, sci, ntohl(hdr->packet_number));
hdr_pn = ntohl(hdr->packet_number);

if (secy->xpn) {
pn_t recovered_pn = rx_sa->next_pn_halves;

recovered_pn.lower = hdr_pn;
if (hdr_pn < rx_sa->next_pn_halves.lower &&
!pn_same_half(hdr_pn, rx_sa->next_pn_halves.lower))
recovered_pn.upper++;

macsec_fill_iv_xpn(iv, rx_sa->ssci, recovered_pn.full64,
rx_sa->key.salt);
} else {
macsec_fill_iv(iv, sci, hdr_pn);
}

sg_init_table(sg, ret);
ret = skb_to_sgvec(skb, sg, 0, skb->len);
Expand Down Expand Up @@ -1001,7 +1052,7 @@ static rx_handler_result_t macsec_handle_frame(struct sk_buff **pskb)
struct macsec_rxh_data *rxd;
struct macsec_dev *macsec;
sci_t sci;
u32 pn;
u32 hdr_pn;
bool cbit;
struct pcpu_rx_sc_stats *rxsc_stats;
struct pcpu_secy_stats *secy_stats;
Expand Down Expand Up @@ -1072,7 +1123,7 @@ static rx_handler_result_t macsec_handle_frame(struct sk_buff **pskb)
secy_stats = this_cpu_ptr(macsec->stats);
rxsc_stats = this_cpu_ptr(rx_sc->stats);

if (!macsec_validate_skb(skb, secy->icv_len)) {
if (!macsec_validate_skb(skb, secy->icv_len, secy->xpn)) {
u64_stats_update_begin(&secy_stats->syncp);
secy_stats->stats.InPktsBadTag++;
u64_stats_update_end(&secy_stats->syncp);
Expand Down Expand Up @@ -1104,13 +1155,16 @@ static rx_handler_result_t macsec_handle_frame(struct sk_buff **pskb)
}

/* First, PN check to avoid decrypting obviously wrong packets */
pn = ntohl(hdr->packet_number);
hdr_pn = ntohl(hdr->packet_number);
if (secy->replay_protect) {
bool late;

spin_lock(&rx_sa->lock);
late = rx_sa->next_pn >= secy->replay_window &&
pn < (rx_sa->next_pn - secy->replay_window);
late = rx_sa->next_pn_halves.lower >= secy->replay_window &&
hdr_pn < (rx_sa->next_pn_halves.lower - secy->replay_window);

if (secy->xpn)
late = late && pn_same_half(rx_sa->next_pn_halves.lower, hdr_pn);
spin_unlock(&rx_sa->lock);

if (late) {
Expand Down Expand Up @@ -1139,7 +1193,7 @@ static rx_handler_result_t macsec_handle_frame(struct sk_buff **pskb)
return RX_HANDLER_CONSUMED;
}

if (!macsec_post_decrypt(skb, secy, pn))
if (!macsec_post_decrypt(skb, secy, hdr_pn))
goto drop;

deliver:
Expand Down Expand Up @@ -1666,7 +1720,7 @@ static int macsec_add_rxsa(struct sk_buff *skb, struct genl_info *info)

if (tb_sa[MACSEC_SA_ATTR_PN]) {
spin_lock_bh(&rx_sa->lock);
rx_sa->next_pn = nla_get_u32(tb_sa[MACSEC_SA_ATTR_PN]);
rx_sa->next_pn_halves.lower = nla_get_u32(tb_sa[MACSEC_SA_ATTR_PN]);
spin_unlock_bh(&rx_sa->lock);
}

Expand Down Expand Up @@ -1873,7 +1927,7 @@ static int macsec_add_txsa(struct sk_buff *skb, struct genl_info *info)
}

spin_lock_bh(&tx_sa->lock);
tx_sa->next_pn = nla_get_u32(tb_sa[MACSEC_SA_ATTR_PN]);
tx_sa->next_pn_halves.lower = nla_get_u32(tb_sa[MACSEC_SA_ATTR_PN]);
spin_unlock_bh(&tx_sa->lock);

if (tb_sa[MACSEC_SA_ATTR_ACTIVE])
Expand Down Expand Up @@ -2137,9 +2191,11 @@ static int macsec_upd_txsa(struct sk_buff *skb, struct genl_info *info)
u8 assoc_num;
struct nlattr *tb_sa[MACSEC_SA_ATTR_MAX + 1];
bool was_operational, was_active;
u32 prev_pn = 0;
pn_t prev_pn;
int ret = 0;

prev_pn.full64 = 0;

if (!attrs[MACSEC_ATTR_IFINDEX])
return -EINVAL;

Expand All @@ -2159,8 +2215,8 @@ static int macsec_upd_txsa(struct sk_buff *skb, struct genl_info *info)

if (tb_sa[MACSEC_SA_ATTR_PN]) {
spin_lock_bh(&tx_sa->lock);
prev_pn = tx_sa->next_pn;
tx_sa->next_pn = nla_get_u32(tb_sa[MACSEC_SA_ATTR_PN]);
prev_pn = tx_sa->next_pn_halves;
tx_sa->next_pn_halves.lower = nla_get_u32(tb_sa[MACSEC_SA_ATTR_PN]);
spin_unlock_bh(&tx_sa->lock);
}

Expand Down Expand Up @@ -2198,7 +2254,7 @@ static int macsec_upd_txsa(struct sk_buff *skb, struct genl_info *info)
cleanup:
if (tb_sa[MACSEC_SA_ATTR_PN]) {
spin_lock_bh(&tx_sa->lock);
tx_sa->next_pn = prev_pn;
tx_sa->next_pn_halves = prev_pn;
spin_unlock_bh(&tx_sa->lock);
}
tx_sa->active = was_active;
Expand All @@ -2218,9 +2274,11 @@ static int macsec_upd_rxsa(struct sk_buff *skb, struct genl_info *info)
struct nlattr *tb_rxsc[MACSEC_RXSC_ATTR_MAX + 1];
struct nlattr *tb_sa[MACSEC_SA_ATTR_MAX + 1];
bool was_active;
u32 prev_pn = 0;
pn_t prev_pn;
int ret = 0;

prev_pn.full64 = 0;

if (!attrs[MACSEC_ATTR_IFINDEX])
return -EINVAL;

Expand All @@ -2243,8 +2301,8 @@ static int macsec_upd_rxsa(struct sk_buff *skb, struct genl_info *info)

if (tb_sa[MACSEC_SA_ATTR_PN]) {
spin_lock_bh(&rx_sa->lock);
prev_pn = rx_sa->next_pn;
rx_sa->next_pn = nla_get_u32(tb_sa[MACSEC_SA_ATTR_PN]);
prev_pn = rx_sa->next_pn_halves;
rx_sa->next_pn_halves.lower = nla_get_u32(tb_sa[MACSEC_SA_ATTR_PN]);
spin_unlock_bh(&rx_sa->lock);
}

Expand Down Expand Up @@ -2277,7 +2335,7 @@ static int macsec_upd_rxsa(struct sk_buff *skb, struct genl_info *info)
cleanup:
if (tb_sa[MACSEC_SA_ATTR_PN]) {
spin_lock_bh(&rx_sa->lock);
rx_sa->next_pn = prev_pn;
rx_sa->next_pn_halves = prev_pn;
spin_unlock_bh(&rx_sa->lock);
}
rx_sa->active = was_active;
Expand Down Expand Up @@ -2796,7 +2854,7 @@ dump_secy(struct macsec_secy *secy, struct net_device *dev,
}

if (nla_put_u8(skb, MACSEC_SA_ATTR_AN, i) ||
nla_put_u32(skb, MACSEC_SA_ATTR_PN, tx_sa->next_pn) ||
nla_put_u32(skb, MACSEC_SA_ATTR_PN, tx_sa->next_pn_halves.lower) ||
nla_put(skb, MACSEC_SA_ATTR_KEYID, MACSEC_KEYID_LEN, tx_sa->key.id) ||
nla_put_u8(skb, MACSEC_SA_ATTR_ACTIVE, tx_sa->active)) {
nla_nest_cancel(skb, txsa_nest);
Expand Down Expand Up @@ -2900,7 +2958,7 @@ dump_secy(struct macsec_secy *secy, struct net_device *dev,
nla_nest_end(skb, attr);

if (nla_put_u8(skb, MACSEC_SA_ATTR_AN, i) ||
nla_put_u32(skb, MACSEC_SA_ATTR_PN, rx_sa->next_pn) ||
nla_put_u32(skb, MACSEC_SA_ATTR_PN, rx_sa->next_pn_halves.lower) ||
nla_put(skb, MACSEC_SA_ATTR_KEYID, MACSEC_KEYID_LEN, rx_sa->key.id) ||
nla_put_u8(skb, MACSEC_SA_ATTR_ACTIVE, rx_sa->active)) {
nla_nest_cancel(skb, rxsa_nest);
Expand Down
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