xref: /linux/net/psp/psp_main.c (revision 0ddb69e2406eba0c2f6bee0d6084e7dd17333c2b)

// SPDX-License-Identifier: GPL-2.0-only

#include <linux/bitfield.h>
#include <linux/list.h>
#include <linux/netdevice.h>
#include <linux/xarray.h>
#include <net/net_namespace.h>
#include <net/psp.h>
#include <net/udp.h>

#include "psp.h"
#include "psp-nl-gen.h"

DEFINE_XARRAY_ALLOC1(psp_devs);
struct mutex psp_devs_lock;

/**
 * DOC: PSP locking
 *
 * psp_devs_lock protects the psp_devs xarray.
 * Ordering is take the psp_devs_lock and then the instance lock.
 * Each instance is protected by RCU, and has a refcount.
 * When driver unregisters the instance gets flushed, but struct sticks around.
 */

/**
 * psp_dev_check_access() - check if user in a given net ns can access PSP dev
 * @psd:	PSP device structure user is trying to access
 * @net:	net namespace user is in
 * @admin:	If true, only allow access from @psd's main device's netns,
 *		for admin operations like config changes and key rotation.
 *		If false, also allow access from network namespaces that have
 *		an associated device with @psd, for read-only and association
 *		management operations.
 *
 * Return: 0 if PSP device should be visible in @net, errno otherwise.
 */
int psp_dev_check_access(struct psp_dev *psd, struct net *net, bool admin)
{
	if (dev_net(psd->main_netdev) == net)
		return 0;

	if (!admin && psp_has_assoc_dev_in_ns(psd, net))
		return 0;

	return -ENOENT;
}

/**
 * psp_dev_create() - create and register PSP device
 * @netdev:	main netdevice
 * @psd_ops:	driver callbacks
 * @psd_caps:	device capabilities
 * @priv_ptr:	back-pointer to driver private data
 *
 * Return: pointer to allocated PSP device, or ERR_PTR.
 */
struct psp_dev *
psp_dev_create(struct net_device *netdev,
	       struct psp_dev_ops *psd_ops, struct psp_dev_caps *psd_caps,
	       void *priv_ptr)
{
	struct psp_dev *psd;
	static u32 last_id;
	int err;

	if (WARN_ON(!psd_caps->versions ||
		    !psd_ops->set_config ||
		    !psd_ops->key_rotate ||
		    !psd_ops->rx_spi_alloc ||
		    !psd_ops->tx_key_add ||
		    !psd_ops->tx_key_del ||
		    !psd_ops->get_stats))
		return ERR_PTR(-EINVAL);

	psd = kzalloc_obj(*psd);
	if (!psd)
		return ERR_PTR(-ENOMEM);

	psd->main_netdev = netdev;
	INIT_LIST_HEAD(&psd->assoc_dev_list);
	psd->ops = psd_ops;
	psd->caps = psd_caps;
	psd->drv_priv = priv_ptr;

	mutex_init(&psd->lock);
	INIT_LIST_HEAD(&psd->active_assocs);
	INIT_LIST_HEAD(&psd->prev_assocs);
	INIT_LIST_HEAD(&psd->stale_assocs);
	refcount_set(&psd->refcnt, 1);

	mutex_lock(&psp_devs_lock);
	err = xa_alloc_cyclic(&psp_devs, &psd->id, psd, xa_limit_16b,
			      &last_id, GFP_KERNEL);
	if (err) {
		mutex_unlock(&psp_devs_lock);
		kfree(psd);
		return ERR_PTR(err);
	}
	mutex_lock(&psd->lock);
	mutex_unlock(&psp_devs_lock);

	/* notify before netdev assignment
	 * There's no strong reason for it, but thinking is to avoid creating
	 * implicit expectations about the PSP dev <> netdev relationship.
	 */
	psp_nl_notify_dev(psd, PSP_CMD_DEV_ADD_NTF);

	rcu_assign_pointer(netdev->psp_dev, psd);

	mutex_unlock(&psd->lock);

	return psd;
}
EXPORT_SYMBOL(psp_dev_create);

void psp_dev_free(struct psp_dev *psd)
{
	mutex_lock(&psp_devs_lock);
	xa_erase(&psp_devs, psd->id);
	mutex_unlock(&psp_devs_lock);

	mutex_destroy(&psd->lock);
	kfree_rcu(psd, rcu);
}

/**
 * psp_dev_unregister() - unregister PSP device
 * @psd:	PSP device structure
 */
void psp_dev_unregister(struct psp_dev *psd)
{
	struct psp_assoc_dev *entry, *entry_tmp;
	struct psp_assoc *pas, *next;

	mutex_lock(&psp_devs_lock);
	mutex_lock(&psd->lock);

	psp_nl_notify_dev(psd, PSP_CMD_DEV_DEL_NTF);

	/* Wait until psp_dev_free() to call xa_erase() to prevent a
	 * different psd from being added to the xarray with this id, while
	 * there are still references to this psd being held.
	 */
	xa_store(&psp_devs, psd->id, NULL, GFP_KERNEL);
	mutex_unlock(&psp_devs_lock);

	list_splice_init(&psd->active_assocs, &psd->prev_assocs);
	list_splice_init(&psd->prev_assocs, &psd->stale_assocs);
	list_for_each_entry_safe(pas, next, &psd->stale_assocs, assocs_list)
		psp_dev_tx_key_del(psd, pas);

	list_for_each_entry_safe(entry, entry_tmp, &psd->assoc_dev_list,
				 dev_list) {
		list_del(&entry->dev_list);
		rcu_assign_pointer(entry->assoc_dev->psp_dev, NULL);
		netdev_put(entry->assoc_dev, &entry->dev_tracker);
		kfree(entry);
	}
	psd->assoc_dev_cnt = 0;

	rcu_assign_pointer(psd->main_netdev->psp_dev, NULL);

	psd->ops = NULL;
	psd->drv_priv = NULL;

	mutex_unlock(&psd->lock);

	psp_dev_put(psd);
}
EXPORT_SYMBOL(psp_dev_unregister);

unsigned int psp_key_size(u32 version)
{
	switch (version) {
	case PSP_VERSION_HDR0_AES_GCM_128:
	case PSP_VERSION_HDR0_AES_GMAC_128:
		return 16;
	case PSP_VERSION_HDR0_AES_GCM_256:
	case PSP_VERSION_HDR0_AES_GMAC_256:
		return 32;
	default:
		return 0;
	}
}
EXPORT_SYMBOL(psp_key_size);

static void psp_write_headers(struct net *net, struct sk_buff *skb, __be32 spi,
			      u8 ver, unsigned int udp_len, __be16 sport)
{
	struct udphdr *uh = udp_hdr(skb);
	struct psphdr *psph = (struct psphdr *)(uh + 1);
	const struct sock *sk = skb->sk;

	uh->dest = htons(PSP_DEFAULT_UDP_PORT);

	/* A bit of theory: Selection of the source port.
	 *
	 * We need some entropy, so that multiple flows use different
	 * source ports for better RSS spreading at the receiver.
	 *
	 * We also need that all packets belonging to one TCP flow
	 * use the same source port through their duration,
	 * so that all these packets land in the same receive queue.
	 *
	 * udp_flow_src_port() is using sk_txhash, inherited from
	 * skb_set_hash_from_sk() call in __tcp_transmit_skb().
	 * This field is subject to reshuffling, thanks to
	 * sk_rethink_txhash() calls in various TCP functions.
	 *
	 * Instead, use sk->sk_hash which is constant through
	 * the whole flow duration.
	 */
	if (likely(sk)) {
		u32 hash = sk->sk_hash;
		int min, max;

		/* These operations are cheap, no need to cache the result
		 * in another socket field.
		 */
		inet_get_local_port_range(net, &min, &max);
		/* Since this is being sent on the wire obfuscate hash a bit
		 * to minimize possibility that any useful information to an
		 * attacker is leaked. Only upper 16 bits are relevant in the
		 * computation for 16 bit port value because we use a
		 * reciprocal divide.
		 */
		hash ^= hash << 16;
		uh->source = htons(reciprocal_scale(hash, max - min + 1) + min);
	} else {
		uh->source = udp_flow_src_port(net, skb, 0, 0, false);
	}
	uh->check = 0;
	uh->len = htons(udp_len);

	psph->nexthdr = IPPROTO_TCP;
	psph->hdrlen = PSP_HDRLEN_NOOPT;
	psph->crypt_offset = 0;
	psph->verfl = FIELD_PREP(PSPHDR_VERFL_VERSION, ver) |
		      FIELD_PREP(PSPHDR_VERFL_ONE, 1);
	psph->spi = spi;
	memset(&psph->iv, 0, sizeof(psph->iv));
}

/* Encapsulate a TCP packet with PSP by adding the UDP+PSP headers and filling
 * them in.
 */
bool psp_dev_encapsulate(struct net *net, struct sk_buff *skb, __be32 spi,
			 u8 ver, __be16 sport)
{
	u32 network_len = skb_network_header_len(skb);
	u32 ethr_len = skb_mac_header_len(skb);
	u32 bufflen = ethr_len + network_len;

	if (skb->protocol != htons(ETH_P_IP) &&
	    skb->protocol != htons(ETH_P_IPV6))
		return false;

	if (skb_cow_head(skb, PSP_ENCAP_HLEN))
		return false;

	skb_push(skb, PSP_ENCAP_HLEN);
	skb->mac_header		-= PSP_ENCAP_HLEN;
	skb->network_header	-= PSP_ENCAP_HLEN;
	skb->transport_header	-= PSP_ENCAP_HLEN;
	memmove(skb->data, skb->data + PSP_ENCAP_HLEN, bufflen);

	if (skb->protocol == htons(ETH_P_IP)) {
		ip_hdr(skb)->protocol = IPPROTO_UDP;
		be16_add_cpu(&ip_hdr(skb)->tot_len, PSP_ENCAP_HLEN);
		ip_hdr(skb)->check = 0;
		ip_hdr(skb)->check =
			ip_fast_csum((u8 *)ip_hdr(skb), ip_hdr(skb)->ihl);
	} else {
		ipv6_hdr(skb)->nexthdr = IPPROTO_UDP;
		be16_add_cpu(&ipv6_hdr(skb)->payload_len, PSP_ENCAP_HLEN);
	}

	skb_set_inner_ipproto(skb, IPPROTO_TCP);
	skb_set_inner_transport_header(skb, skb_transport_offset(skb) +
						    PSP_ENCAP_HLEN);
	skb->encapsulation = 1;
	psp_write_headers(net, skb, spi, ver,
			  skb->len - skb_transport_offset(skb), sport);

	return true;
}
EXPORT_SYMBOL(psp_dev_encapsulate);

/* Receive handler for PSP packets.
 *
 * Accepts only already-authenticated packets. The full PSP header is
 * stripped according to psph->hdrlen; any optional fields it advertises
 * (virtualization cookies, etc.) are ignored and discarded along with the
 * rest of the header. The caller should ensure that skb->data is pointing
 * to the mac header, and that skb->mac_len is set. This function does not
 * currently adjust skb->csum (CHECKSUM_COMPLETE is not supported).
 */
int psp_dev_rcv(struct sk_buff *skb, u16 dev_id, u8 generation, bool strip_icv)
{
	int l2_hlen = 0, l3_hlen, encap, psp_hlen;
	struct psp_skb_ext *pse;
	struct psphdr *psph;
	struct ethhdr *eth;
	struct udphdr *uh;
	__be16 proto;
	bool is_udp;

	eth = (struct ethhdr *)skb->data;
	proto = __vlan_get_protocol(skb, eth->h_proto, &l2_hlen);
	if (proto == htons(ETH_P_IP))
		l3_hlen = sizeof(struct iphdr);
	else if (proto == htons(ETH_P_IPV6))
		l3_hlen = sizeof(struct ipv6hdr);
	else
		return -EINVAL;

	if (unlikely(!pskb_may_pull(skb, l2_hlen + l3_hlen + PSP_ENCAP_HLEN)))
		return -EINVAL;

	if (proto == htons(ETH_P_IP)) {
		struct iphdr *iph = (struct iphdr *)(skb->data + l2_hlen);

		if (unlikely(iph->ihl < 5))
			return -EINVAL;

		is_udp = iph->protocol == IPPROTO_UDP;
		l3_hlen = iph->ihl * 4;
		if (l3_hlen != sizeof(struct iphdr) &&
		    !pskb_may_pull(skb, l2_hlen + l3_hlen + PSP_ENCAP_HLEN))
			return -EINVAL;
	} else {
		struct ipv6hdr *ipv6h = (struct ipv6hdr *)(skb->data + l2_hlen);

		is_udp = ipv6h->nexthdr == IPPROTO_UDP;
	}

	if (unlikely(!is_udp))
		return -EINVAL;

	uh = (struct udphdr *)(skb->data + l2_hlen + l3_hlen);
	if (unlikely(uh->dest != htons(PSP_DEFAULT_UDP_PORT)))
		return -EINVAL;

	psph = (struct psphdr *)(skb->data + l2_hlen + l3_hlen +
				 sizeof(struct udphdr));

	/* Strip the full PSP header per psph->hdrlen; VC/options are pulled
	 * into the linear region only so they can be discarded with the
	 * rest of the header.
	 */
	psp_hlen = (psph->hdrlen + 1) * 8;

	if (unlikely(psp_hlen < sizeof(struct psphdr)))
		return -EINVAL;

	if (psp_hlen > sizeof(struct psphdr) &&
	    !pskb_may_pull(skb, l2_hlen + l3_hlen +
				sizeof(struct udphdr) + psp_hlen))
		return -EINVAL;

	psph = (struct psphdr *)(skb->data + l2_hlen + l3_hlen +
				 sizeof(struct udphdr));

	pse = skb_ext_add(skb, SKB_EXT_PSP);
	if (!pse)
		return -EINVAL;

	pse->spi = psph->spi;
	pse->dev_id = dev_id;
	pse->generation = generation;
	pse->version = FIELD_GET(PSPHDR_VERFL_VERSION, psph->verfl);

	encap = sizeof(struct udphdr) + psp_hlen;
	encap += strip_icv ? PSP_TRL_SIZE : 0;

	if (proto == htons(ETH_P_IP)) {
		struct iphdr *iph = (struct iphdr *)(skb->data + l2_hlen);

		if (unlikely(ntohs(iph->tot_len) < l3_hlen + encap))
			return -EINVAL;

		iph->protocol = psph->nexthdr;
		iph->tot_len = htons(ntohs(iph->tot_len) - encap);
		iph->check = 0;
		iph->check = ip_fast_csum((u8 *)iph, iph->ihl);
	} else {
		struct ipv6hdr *ipv6h = (struct ipv6hdr *)(skb->data + l2_hlen);

		if (unlikely(ntohs(ipv6h->payload_len) < encap))
			return -EINVAL;

		ipv6h->nexthdr = psph->nexthdr;
		ipv6h->payload_len = htons(ntohs(ipv6h->payload_len) - encap);
	}

	memmove(skb->data + sizeof(struct udphdr) + psp_hlen,
		skb->data, l2_hlen + l3_hlen);
	skb_pull(skb, sizeof(struct udphdr) + psp_hlen);

	if (strip_icv)
		pskb_trim(skb, skb->len - PSP_TRL_SIZE);

	return 0;
}
EXPORT_SYMBOL(psp_dev_rcv);

static void psp_dev_disassoc_one(struct psp_dev *psd, struct net_device *dev)
{
	struct psp_assoc_dev *entry;

	list_for_each_entry(entry, &psd->assoc_dev_list, dev_list) {
		if (entry->assoc_dev == dev) {
			list_del(&entry->dev_list);
			psd->assoc_dev_cnt--;
			rcu_assign_pointer(entry->assoc_dev->psp_dev, NULL);
			netdev_put(entry->assoc_dev, &entry->dev_tracker);
			kfree(entry);
			return;
		}
	}
}

static int psp_netdev_event(struct notifier_block *nb, unsigned long event,
			    void *ptr)
{
	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
	struct psp_dev *psd;

	if (event != NETDEV_UNREGISTER)
		return NOTIFY_DONE;

	rcu_read_lock();
	psd = rcu_dereference(dev->psp_dev);
	if (psd && psp_dev_tryget(psd)) {
		rcu_read_unlock();
		mutex_lock(&psd->lock);
		if (psp_dev_is_registered(psd))
			psp_nl_notify_dev(psd, PSP_CMD_DEV_CHANGE_NTF);
		psp_dev_disassoc_one(psd, dev);
		mutex_unlock(&psd->lock);
		psp_dev_put(psd);
	} else {
		rcu_read_unlock();
	}

	return NOTIFY_DONE;
}

static struct notifier_block psp_netdev_notifier = {
	.notifier_call = psp_netdev_event,
};

static DEFINE_MUTEX(psp_notifier_lock);
static bool psp_notifier_registered;

/* Register the netdevice notifier when the first device association
 * is created. In many installations no associations will be created and
 * the notifier won't be needed.
 *
 * Must be called without psd->lock held, due to lock ordering:
 * rtnl_lock -> psd->lock (the notifier callback runs under rtnl_lock
 * and takes psd->lock).
 */
int psp_attach_netdev_notifier(void)
{
	int err = 0;

	if (READ_ONCE(psp_notifier_registered))
		return 0;

	mutex_lock(&psp_notifier_lock);
	if (!psp_notifier_registered) {
		err = register_netdevice_notifier(&psp_netdev_notifier);
		if (!err)
			WRITE_ONCE(psp_notifier_registered, true);
	}
	mutex_unlock(&psp_notifier_lock);

	return err;
}

static int __init psp_init(void)
{
	mutex_init(&psp_devs_lock);

	return genl_register_family(&psp_nl_family);
}

subsys_initcall(psp_init);