[PATCH v3 1/2] macsec: Support XPN frame handling - IEEE 802.1AEbw

From: Era Mayflower
Date: Mon Mar 09 2020 - 06:47:19 EST

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@xxxxxxxxx>
---
drivers/net/macsec.c | 130 +++++++++++++++++++++++++++++++------------
include/net/macsec.h | 45 ++++++++++++++-
2 files changed, 136 insertions(+), 39 deletions(-)

diff --git a/drivers/net/macsec.c b/drivers/net/macsec.c
index 45bfd99f1..de9578daa 100644
--- a/drivers/net/macsec.c
+++ b/drivers/net/macsec.c
@@ -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>

@@ -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];
@@ -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;
@@ -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) */
@@ -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;
@@ -441,14 +461,19 @@ 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);
@@ -563,7 +588,7 @@ 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;
@@ -605,12 +630,12 @@ 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);
@@ -641,7 +666,10 @@ 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);
@@ -693,13 +721,14 @@ 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++;
@@ -748,8 +777,15 @@ 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);
}

@@ -836,6 +872,7 @@ 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;
@@ -855,7 +892,21 @@ 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);
@@ -996,7 +1047,7 @@ 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;
@@ -1067,7 +1118,7 @@ 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);
@@ -1099,13 +1150,16 @@ 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) {
@@ -1134,7 +1188,7 @@ 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:
@@ -1661,7 +1715,7 @@ 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);
}

@@ -1868,7 +1922,7 @@ 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])
@@ -2132,9 +2186,11 @@ 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;

@@ -2154,8 +2210,8 @@ 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);
}

@@ -2193,7 +2249,7 @@ 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;
@@ -2213,9 +2269,11 @@ 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;

@@ -2238,8 +2296,8 @@ 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);
}

@@ -2272,7 +2330,7 @@ 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;
@@ -2791,7 +2849,7 @@ 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);
@@ -2895,7 +2953,7 @@ 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);
diff --git a/include/net/macsec.h b/include/net/macsec.h
index 92e43db8b..43cd54e17 100644
--- a/include/net/macsec.h
+++ b/include/net/macsec.h
@@ -11,18 +11,45 @@
#include <uapi/linux/if_link.h>
#include <uapi/linux/if_macsec.h>

+#define MACSEC_SALT_LEN 12
+#define MACSEC_NUM_AN 4 /* 2 bits for the association number */
+
typedef u64 __bitwise sci_t;
+typedef u32 __bitwise ssci_t;

-#define MACSEC_NUM_AN 4 /* 2 bits for the association number */
+typedef union salt {
+ struct {
+ u32 ssci;
+ u64 pn;
+ } __packed;
+ u8 bytes[MACSEC_SALT_LEN];
+} __packed salt_t;
+
+typedef union pn {
+ struct {
+#if defined(__LITTLE_ENDIAN_BITFIELD)
+ u32 lower;
+ u32 upper;
+#elif defined(__BIG_ENDIAN_BITFIELD)
+ u32 upper;
+ u32 lower;
+#else
+#error "Please fix <asm/byteorder.h>"
+#endif
+ };
+ u64 full64;
+} pn_t;

/**
* struct macsec_key - SA key
* @id: user-provided key identifier
* @tfm: crypto struct, key storage
+ * @salt: salt used to generate IV in XPN cipher suites
*/
struct macsec_key {
u8 id[MACSEC_KEYID_LEN];
struct crypto_aead *tfm;
+ salt_t salt;
};

struct macsec_rx_sc_stats {
@@ -64,12 +91,17 @@ struct macsec_tx_sc_stats {
* @next_pn: packet number expected for the next packet
* @lock: protects next_pn manipulations
* @key: key structure
+ * @ssci: short secure channel identifier
* @stats: per-SA stats
*/
struct macsec_rx_sa {
struct macsec_key key;
+ ssci_t ssci;
spinlock_t lock;
- u32 next_pn;
+ union {
+ pn_t next_pn_halves;
+ u64 next_pn;
+ };
refcount_t refcnt;
bool active;
struct macsec_rx_sa_stats __percpu *stats;
@@ -110,12 +142,17 @@ struct macsec_rx_sc {
* @next_pn: packet number to use for the next packet
* @lock: protects next_pn manipulations
* @key: key structure
+ * @ssci: short secure channel identifier
* @stats: per-SA stats
*/
struct macsec_tx_sa {
struct macsec_key key;
+ ssci_t ssci;
spinlock_t lock;
- u32 next_pn;
+ union {
+ pn_t next_pn_halves;
+ u64 next_pn;
+ };
refcount_t refcnt;
bool active;
struct macsec_tx_sa_stats __percpu *stats;
@@ -152,6 +189,7 @@ struct macsec_tx_sc {
* @key_len: length of keys used by the cipher suite
* @icv_len: length of ICV used by the cipher suite
* @validate_frames: validation mode
+ * @xpn: enable XPN for this SecY
* @operational: MAC_Operational flag
* @protect_frames: enable protection for this SecY
* @replay_protect: enable packet number checks on receive
@@ -166,6 +204,7 @@ struct macsec_secy {
u16 key_len;
u16 icv_len;
enum macsec_validation_type validate_frames;
+ bool xpn;
bool operational;
bool protect_frames;
bool replay_protect;
--
2.20.1