diff options
Diffstat (limited to 'drivers/net/wireguard/peerlookup.c')
| -rw-r--r-- | drivers/net/wireguard/peerlookup.c | 226 |
1 files changed, 226 insertions, 0 deletions
diff --git a/drivers/net/wireguard/peerlookup.c b/drivers/net/wireguard/peerlookup.c new file mode 100644 index 0000000000..f2783aa7a8 --- /dev/null +++ b/drivers/net/wireguard/peerlookup.c @@ -0,0 +1,226 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved. + */ + +#include "peerlookup.h" +#include "peer.h" +#include "noise.h" + +static struct hlist_head *pubkey_bucket(struct pubkey_hashtable *table, + const u8 pubkey[NOISE_PUBLIC_KEY_LEN]) +{ + /* siphash gives us a secure 64bit number based on a random key. Since + * the bits are uniformly distributed, we can then mask off to get the + * bits we need. + */ + const u64 hash = siphash(pubkey, NOISE_PUBLIC_KEY_LEN, &table->key); + + return &table->hashtable[hash & (HASH_SIZE(table->hashtable) - 1)]; +} + +struct pubkey_hashtable *wg_pubkey_hashtable_alloc(void) +{ + struct pubkey_hashtable *table = kvmalloc(sizeof(*table), GFP_KERNEL); + + if (!table) + return NULL; + + get_random_bytes(&table->key, sizeof(table->key)); + hash_init(table->hashtable); + mutex_init(&table->lock); + return table; +} + +void wg_pubkey_hashtable_add(struct pubkey_hashtable *table, + struct wg_peer *peer) +{ + mutex_lock(&table->lock); + hlist_add_head_rcu(&peer->pubkey_hash, + pubkey_bucket(table, peer->handshake.remote_static)); + mutex_unlock(&table->lock); +} + +void wg_pubkey_hashtable_remove(struct pubkey_hashtable *table, + struct wg_peer *peer) +{ + mutex_lock(&table->lock); + hlist_del_init_rcu(&peer->pubkey_hash); + mutex_unlock(&table->lock); +} + +/* Returns a strong reference to a peer */ +struct wg_peer * +wg_pubkey_hashtable_lookup(struct pubkey_hashtable *table, + const u8 pubkey[NOISE_PUBLIC_KEY_LEN]) +{ + struct wg_peer *iter_peer, *peer = NULL; + + rcu_read_lock_bh(); + hlist_for_each_entry_rcu_bh(iter_peer, pubkey_bucket(table, pubkey), + pubkey_hash) { + if (!memcmp(pubkey, iter_peer->handshake.remote_static, + NOISE_PUBLIC_KEY_LEN)) { + peer = iter_peer; + break; + } + } + peer = wg_peer_get_maybe_zero(peer); + rcu_read_unlock_bh(); + return peer; +} + +static struct hlist_head *index_bucket(struct index_hashtable *table, + const __le32 index) +{ + /* Since the indices are random and thus all bits are uniformly + * distributed, we can find its bucket simply by masking. + */ + return &table->hashtable[(__force u32)index & + (HASH_SIZE(table->hashtable) - 1)]; +} + +struct index_hashtable *wg_index_hashtable_alloc(void) +{ + struct index_hashtable *table = kvmalloc(sizeof(*table), GFP_KERNEL); + + if (!table) + return NULL; + + hash_init(table->hashtable); + spin_lock_init(&table->lock); + return table; +} + +/* At the moment, we limit ourselves to 2^20 total peers, which generally might + * amount to 2^20*3 items in this hashtable. The algorithm below works by + * picking a random number and testing it. We can see that these limits mean we + * usually succeed pretty quickly: + * + * >>> def calculation(tries, size): + * ... return (size / 2**32)**(tries - 1) * (1 - (size / 2**32)) + * ... + * >>> calculation(1, 2**20 * 3) + * 0.999267578125 + * >>> calculation(2, 2**20 * 3) + * 0.0007318854331970215 + * >>> calculation(3, 2**20 * 3) + * 5.360489012673497e-07 + * >>> calculation(4, 2**20 * 3) + * 3.9261394135792216e-10 + * + * At the moment, we don't do any masking, so this algorithm isn't exactly + * constant time in either the random guessing or in the hash list lookup. We + * could require a minimum of 3 tries, which would successfully mask the + * guessing. this would not, however, help with the growing hash lengths, which + * is another thing to consider moving forward. + */ + +__le32 wg_index_hashtable_insert(struct index_hashtable *table, + struct index_hashtable_entry *entry) +{ + struct index_hashtable_entry *existing_entry; + + spin_lock_bh(&table->lock); + hlist_del_init_rcu(&entry->index_hash); + spin_unlock_bh(&table->lock); + + rcu_read_lock_bh(); + +search_unused_slot: + /* First we try to find an unused slot, randomly, while unlocked. */ + entry->index = (__force __le32)get_random_u32(); + hlist_for_each_entry_rcu_bh(existing_entry, + index_bucket(table, entry->index), + index_hash) { + if (existing_entry->index == entry->index) + /* If it's already in use, we continue searching. */ + goto search_unused_slot; + } + + /* Once we've found an unused slot, we lock it, and then double-check + * that nobody else stole it from us. + */ + spin_lock_bh(&table->lock); + hlist_for_each_entry_rcu_bh(existing_entry, + index_bucket(table, entry->index), + index_hash) { + if (existing_entry->index == entry->index) { + spin_unlock_bh(&table->lock); + /* If it was stolen, we start over. */ + goto search_unused_slot; + } + } + /* Otherwise, we know we have it exclusively (since we're locked), + * so we insert. + */ + hlist_add_head_rcu(&entry->index_hash, + index_bucket(table, entry->index)); + spin_unlock_bh(&table->lock); + + rcu_read_unlock_bh(); + + return entry->index; +} + +bool wg_index_hashtable_replace(struct index_hashtable *table, + struct index_hashtable_entry *old, + struct index_hashtable_entry *new) +{ + bool ret; + + spin_lock_bh(&table->lock); + ret = !hlist_unhashed(&old->index_hash); + if (unlikely(!ret)) + goto out; + + new->index = old->index; + hlist_replace_rcu(&old->index_hash, &new->index_hash); + + /* Calling init here NULLs out index_hash, and in fact after this + * function returns, it's theoretically possible for this to get + * reinserted elsewhere. That means the RCU lookup below might either + * terminate early or jump between buckets, in which case the packet + * simply gets dropped, which isn't terrible. + */ + INIT_HLIST_NODE(&old->index_hash); +out: + spin_unlock_bh(&table->lock); + return ret; +} + +void wg_index_hashtable_remove(struct index_hashtable *table, + struct index_hashtable_entry *entry) +{ + spin_lock_bh(&table->lock); + hlist_del_init_rcu(&entry->index_hash); + spin_unlock_bh(&table->lock); +} + +/* Returns a strong reference to a entry->peer */ +struct index_hashtable_entry * +wg_index_hashtable_lookup(struct index_hashtable *table, + const enum index_hashtable_type type_mask, + const __le32 index, struct wg_peer **peer) +{ + struct index_hashtable_entry *iter_entry, *entry = NULL; + + rcu_read_lock_bh(); + hlist_for_each_entry_rcu_bh(iter_entry, index_bucket(table, index), + index_hash) { + if (iter_entry->index == index) { + if (likely(iter_entry->type & type_mask)) + entry = iter_entry; + break; + } + } + if (likely(entry)) { + entry->peer = wg_peer_get_maybe_zero(entry->peer); + if (likely(entry->peer)) + *peer = entry->peer; + else + entry = NULL; + } + rcu_read_unlock_bh(); + return entry; +} |