On Wed, Aug 09, 2023 at 02:58:51PM +0200, Sabrina Dubroca wrote:
> When a TLS handshake record carrying a KeyUpdate message is received,
> all subsequent records will be encrypted with a new key. We need to
> stop decrypting incoming records with the old key, and wait until
> userspace provides a new key.
>
> Make a note of this in the RX context just after decrypting that
> record, and stop recvmsg/splice calls with EKEYEXPIRED until the new
> key is available.
>
> v3:
> - move key_update_pending check into tls_rx_rec_wait (Jakub)
> - TLS_RECORD_TYPE_HANDSHAKE was added to include/net/tls_prot.h by
> the tls handshake series, drop that from this patch
> - move key_update_pending into an existing hole
>
> Signed-off-by: Sabrina Dubroca <sd@xxxxxxxxxxxxxxx>
> ---
> include/net/tls.h | 3 +++
> net/tls/tls_sw.c | 36 ++++++++++++++++++++++++++++++++++++
> 2 files changed, 39 insertions(+)
>
> diff --git a/include/net/tls.h b/include/net/tls.h
> index 06fca9160346..219a4f38c0e4 100644
> --- a/include/net/tls.h
> +++ b/include/net/tls.h
> @@ -69,6 +69,8 @@ extern const struct tls_cipher_size_desc tls_cipher_size_desc[];
>
> #define TLS_CRYPTO_INFO_READY(info) ((info)->cipher_type)
>
> +#define TLS_HANDSHAKE_KEYUPDATE 24 /* rfc8446 B.3: Key update */
> +
> #define TLS_AAD_SPACE_SIZE 13
>
> #define MAX_IV_SIZE 16
> @@ -141,6 +143,7 @@ struct tls_sw_context_rx {
> u8 async_capable:1;
> u8 zc_capable:1;
> u8 reader_contended:1;
> + bool key_update_pending;
Hi Sabrina,
Would it make sense for this to be
u8 key_update_pending:1;
>
> struct tls_strparser strp;
>
> diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
> index 2ca0eb90a2a5..497f56c5f169 100644
> --- a/net/tls/tls_sw.c
> +++ b/net/tls/tls_sw.c
> @@ -1293,6 +1293,10 @@ tls_rx_rec_wait(struct sock *sk, struct sk_psock *psock, bool nonblock,
> DEFINE_WAIT_FUNC(wait, woken_wake_function);
> long timeo;
>
> + /* a rekey is pending, let userspace deal with it */
> + if (unlikely(ctx->key_update_pending))
> + return -EKEYEXPIRED;
> +
> timeo = sock_rcvtimeo(sk, nonblock);
>
> while (!tls_strp_msg_ready(ctx)) {
> @@ -1689,6 +1693,33 @@ tls_decrypt_device(struct sock *sk, struct msghdr *msg,
> return 1;
> }
>
> +static int tls_check_pending_rekey(struct sock *sk, struct sk_buff *skb)
> +{
> + const struct tls_msg *tlm = tls_msg(skb);
> + const struct strp_msg *rxm = strp_msg(skb);
nit: reverse xmas tree
> +
> + if (tlm->control == TLS_RECORD_TYPE_HANDSHAKE) {
> + char hs_type;
> + int err;
> +
> + if (rxm->full_len < 1)
> + return -EINVAL;
> +
> + err = skb_copy_bits(skb, rxm->offset, &hs_type, 1);
> + if (err < 0)
> + return err;
> +
> + if (hs_type == TLS_HANDSHAKE_KEYUPDATE) {
> + struct tls_context *ctx = tls_get_ctx(sk);
> + struct tls_sw_context_rx *rx_ctx = ctx->priv_ctx_rx;
> +
> + rx_ctx->key_update_pending = true;
> + }
> + }
> +
> + return 0;
> +}
> +
> static int tls_rx_one_record(struct sock *sk, struct msghdr *msg,
> struct tls_decrypt_arg *darg)
> {
> @@ -1708,6 +1739,10 @@ static int tls_rx_one_record(struct sock *sk, struct msghdr *msg,
> rxm->full_len -= prot->overhead_size;
> tls_advance_record_sn(sk, prot, &tls_ctx->rx);
>
> + err = tls_check_pending_rekey(sk, darg->skb);
> + if (err < 0)
> + return err;
> +
> return 0;
> }
>
> @@ -2642,6 +2677,7 @@ int tls_set_sw_offload(struct sock *sk, int tx)
> skb_queue_head_init(&sw_ctx_rx->rx_list);
> skb_queue_head_init(&sw_ctx_rx->async_hold);
> aead = &sw_ctx_rx->aead_recv;
> + sw_ctx_rx->key_update_pending = false;
> }
>
> switch (crypto_info->cipher_type) {
> --
> 2.40.1
>
>
