Hi Leonard,
On 11/1/21 16:34, Leonard Crestez wrote:
[..]
> +struct tcp_authopt_key {
> + /** @flags: Combination of &enum tcp_authopt_key_flag */
> + __u32 flags;
> + /** @send_id: keyid value for send */
> + __u8 send_id;
> + /** @recv_id: keyid value for receive */
> + __u8 recv_id;
> + /** @alg: One of &enum tcp_authopt_alg */
> + __u8 alg;
> + /** @keylen: Length of the key buffer */
> + __u8 keylen;
> + /** @key: Secret key */
> + __u8 key[TCP_AUTHOPT_MAXKEYLEN];
> + /**
> + * @addr: Key is only valid for this address
> + *
> + * Ignored unless TCP_AUTHOPT_KEY_ADDR_BIND flag is set
> + */
> + struct __kernel_sockaddr_storage addr;
> +};
[..]
> +/* Free key nicely, for living sockets */
> +static void tcp_authopt_key_del(struct sock *sk,
> + struct tcp_authopt_info *info,
> + struct tcp_authopt_key_info *key)
> +{
> + sock_owned_by_me(sk);
> + hlist_del_rcu(&key->node);
> + atomic_sub(sizeof(*key), &sk->sk_omem_alloc);
> + kfree_rcu(key, rcu);
> +}
[..]
> +#define TCP_AUTHOPT_KEY_KNOWN_FLAGS ( \
> + TCP_AUTHOPT_KEY_DEL | \
> + TCP_AUTHOPT_KEY_EXCLUDE_OPTS | \
> + TCP_AUTHOPT_KEY_ADDR_BIND)
> +
> +int tcp_set_authopt_key(struct sock *sk, sockptr_t optval, unsigned int optlen)
> +{
[..]
> + /* Delete is a special case: */
> + if (opt.flags & TCP_AUTHOPT_KEY_DEL) {
> + info = rcu_dereference_check(tcp_sk(sk)->authopt_info, lockdep_sock_is_held(sk));
> + if (!info)
> + return -ENOENT;
> + key_info = tcp_authopt_key_lookup_exact(sk, info, &opt);
> + if (!key_info)
> + return -ENOENT;
> + tcp_authopt_key_del(sk, info, key_info);
> + return 0;
I remember we discussed it in RFC, that removing a key that's currently
in use may result in random MKT to be used.
I think, it's possible to make this API a bit more predictable if:
- DEL command fails to remove a key that is current/receive_next;
- opt.flags has CURR/NEXT flag that has corresponding `u8 current_key`
and `u8 receive_next` values. As socket lock is held - that makes
current_key/receive_next change atomic with deletion of an existing key
that might have been in use.
In result user may remove a key that's not in use or has to set new
current/next. Which avoids the issue with random MKT being used to sign
segments.
Thanks,
Dmitry
