/* SPDX-License-Identifier: GPL-2.0 */
/*
 * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
 */
#ifndef _WG_NOISE_H
#define _WG_NOISE_H

#include "messages.h"
#include "peerlookup.h"

#include <linux/types.h>
#include <linux/spinlock.h>
#include <linux/atomic.h>
#include <linux/rwsem.h>
#include <linux/mutex.h>
#include <linux/kref.h>

struct noise_replay_counter {
        u64 counter;
        spinlock_t lock;
        unsigned long backtrack[COUNTER_BITS_TOTAL / BITS_PER_LONG];
};

struct noise_symmetric_key {
        u8 key[NOISE_SYMMETRIC_KEY_LEN];
        u64 birthdate;
        bool is_valid;
};

struct noise_keypair {
        struct index_hashtable_entry entry;
        struct noise_symmetric_key sending;
        atomic64_t sending_counter;
        struct noise_symmetric_key receiving;
        struct noise_replay_counter receiving_counter;
        __le32 remote_index;
        bool i_am_the_initiator;
        struct kref refcount;
        struct rcu_head rcu;
        u64 internal_id;
};

struct noise_keypairs {
        struct noise_keypair __rcu *current_keypair;
        struct noise_keypair __rcu *previous_keypair;
        struct noise_keypair __rcu *next_keypair;
        spinlock_t keypair_update_lock;
};

struct noise_static_identity {
        u8 static_public[NOISE_PUBLIC_KEY_LEN];
        u8 static_private[NOISE_PUBLIC_KEY_LEN];
        struct rw_semaphore lock;
        bool has_identity;
};

enum noise_handshake_state {
        HANDSHAKE_ZEROED,
        HANDSHAKE_CREATED_INITIATION,
        HANDSHAKE_CONSUMED_INITIATION,
        HANDSHAKE_CREATED_RESPONSE,
        HANDSHAKE_CONSUMED_RESPONSE
};

struct noise_handshake {
        struct index_hashtable_entry entry;

        enum noise_handshake_state state;
        u64 last_initiation_consumption;

        struct noise_static_identity *static_identity;

        u8 ephemeral_private[NOISE_PUBLIC_KEY_LEN];
        u8 remote_static[NOISE_PUBLIC_KEY_LEN];
        u8 remote_ephemeral[NOISE_PUBLIC_KEY_LEN];
        u8 precomputed_static_static[NOISE_PUBLIC_KEY_LEN];

        u8 preshared_key[NOISE_SYMMETRIC_KEY_LEN];

        u8 hash[NOISE_HASH_LEN];
        u8 chaining_key[NOISE_HASH_LEN];

        u8 latest_timestamp[NOISE_TIMESTAMP_LEN];
        __le32 remote_index;

        /* Protects all members except the immutable (after noise_handshake_
         * init): remote_static, precomputed_static_static, static_identity.
         */
        struct rw_semaphore lock;
};

struct wg_device;

void wg_noise_init(void);
void wg_noise_handshake_init(struct noise_handshake *handshake,
                             struct noise_static_identity *static_identity,
                             const u8 peer_public_key[NOISE_PUBLIC_KEY_LEN],
                             const u8 peer_preshared_key[NOISE_SYMMETRIC_KEY_LEN],
                             struct wg_peer *peer);
void wg_noise_handshake_clear(struct noise_handshake *handshake);
static inline void wg_noise_reset_last_sent_handshake(atomic64_t *handshake_ns)
{
        atomic64_set(handshake_ns, ktime_get_coarse_boottime_ns() -
                                       (u64)(REKEY_TIMEOUT + 1) * NSEC_PER_SEC);
}

void wg_noise_keypair_put(struct noise_keypair *keypair, bool unreference_now);
struct noise_keypair *wg_noise_keypair_get(struct noise_keypair *keypair);
void wg_noise_keypairs_clear(struct noise_keypairs *keypairs);
bool wg_noise_received_with_keypair(struct noise_keypairs *keypairs,
                                    struct noise_keypair *received_keypair);
void wg_noise_expire_current_peer_keypairs(struct wg_peer *peer);

void wg_noise_set_static_identity_private_key(
        struct noise_static_identity *static_identity,
        const u8 private_key[NOISE_PUBLIC_KEY_LEN]);
void wg_noise_precompute_static_static(struct wg_peer *peer);

bool
wg_noise_handshake_create_initiation(struct message_handshake_initiation *dst,
                                     struct noise_handshake *handshake);
struct wg_peer *
wg_noise_handshake_consume_initiation(struct message_handshake_initiation *src,
                                      struct wg_device *wg);

bool wg_noise_handshake_create_response(struct message_handshake_response *dst,
                                        struct noise_handshake *handshake);
struct wg_peer *
wg_noise_handshake_consume_response(struct message_handshake_response *src,
                                    struct wg_device *wg);

bool wg_noise_handshake_begin_session(struct noise_handshake *handshake,
                                      struct noise_keypairs *keypairs);

#endif /* _WG_NOISE_H */