tls: implement rekey for TLS1.3

This adds the possibility to change the key and IV when using
TLS1.3. Changing the cipher or TLS version is not supported.

Once we have updated the RX key, we can unblock the receive side. If
the rekey fails, the context is unmodified and userspace is free to
retry the update or close the socket.

This change only affects tls_sw, since 1.3 offload isn't supported.

Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 34 insertions, 12 deletions

diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c
index 6b4b9f2749a6..68b5735dafc1 100644
--- a/net/tls/tls_main.c
+++ b/net/tls/tls_main.c
@@ -423,9 +423,10 @@ static __poll_t tls_sk_poll(struct file *file, struct socket *sock,
 	ctx = tls_sw_ctx_rx(tls_ctx);
 	psock = sk_psock_get(sk);
 
-	if (skb_queue_empty_lockless(&ctx->rx_list) &&
-	    !tls_strp_msg_ready(ctx) &&
-	    sk_psock_queue_empty(psock))
+	if ((skb_queue_empty_lockless(&ctx->rx_list) &&
+	     !tls_strp_msg_ready(ctx) &&
+	     sk_psock_queue_empty(psock)) ||
+	    READ_ONCE(ctx->key_update_pending))
 		mask &= ~(EPOLLIN | EPOLLRDNORM);
 
 	if (psock)
@@ -612,11 +613,13 @@ static int validate_crypto_info(const struct tls_crypto_info *crypto_info,
 static int do_tls_setsockopt_conf(struct sock *sk, sockptr_t optval,
 				  unsigned int optlen, int tx)
 {
-	struct tls_crypto_info *crypto_info;
-	struct tls_crypto_info *alt_crypto_info;
+	struct tls_crypto_info *crypto_info, *alt_crypto_info;
+	struct tls_crypto_info *old_crypto_info = NULL;
 	struct tls_context *ctx = tls_get_ctx(sk);
 	const struct tls_cipher_desc *cipher_desc;
 	union tls_crypto_context *crypto_ctx;
+	union tls_crypto_context tmp = {};
+	bool update = false;
 	int rc = 0;
 	int conf;
 
@@ -633,9 +636,18 @@ static int do_tls_setsockopt_conf(struct sock *sk, sockptr_t optval,
 
 	crypto_info = &crypto_ctx->info;
 
-	/* Currently we don't support set crypto info more than one time */
-	if (TLS_CRYPTO_INFO_READY(crypto_info))
-		return -EBUSY;
+	if (TLS_CRYPTO_INFO_READY(crypto_info)) {
+		/* Currently we only support setting crypto info more
+		 * than one time for TLS 1.3
+		 */
+		if (crypto_info->version != TLS_1_3_VERSION)
+			return -EBUSY;
+
+		update = true;
+		old_crypto_info = crypto_info;
+		crypto_info = &tmp.info;
+		crypto_ctx = &tmp;
+	}
 
 	rc = copy_from_sockptr(crypto_info, optval, sizeof(*crypto_info));
 	if (rc) {
@@ -643,7 +655,14 @@ static int do_tls_setsockopt_conf(struct sock *sk, sockptr_t optval,
 		goto err_crypto_info;
 	}
 
-	rc = validate_crypto_info(crypto_info, alt_crypto_info);
+	if (update) {
+		/* Ensure that TLS version and ciphers are not modified */
+		if (crypto_info->version != old_crypto_info->version ||
+		    crypto_info->cipher_type != old_crypto_info->cipher_type)
+			rc = -EINVAL;
+	} else {
+		rc = validate_crypto_info(crypto_info, alt_crypto_info);
+	}
 	if (rc)
 		goto err_crypto_info;
 
@@ -673,7 +692,8 @@ static int do_tls_setsockopt_conf(struct sock *sk, sockptr_t optval,
 			TLS_INC_STATS(sock_net(sk), LINUX_MIB_TLSTXDEVICE);
 			TLS_INC_STATS(sock_net(sk), LINUX_MIB_TLSCURRTXDEVICE);
 		} else {
-			rc = tls_set_sw_offload(sk, 1);
+			rc = tls_set_sw_offload(sk, 1,
+						update ? crypto_info : NULL);
 			if (rc)
 				goto err_crypto_info;
 			TLS_INC_STATS(sock_net(sk), LINUX_MIB_TLSTXSW);
@@ -687,14 +707,16 @@ static int do_tls_setsockopt_conf(struct sock *sk, sockptr_t optval,
 			TLS_INC_STATS(sock_net(sk), LINUX_MIB_TLSRXDEVICE);
 			TLS_INC_STATS(sock_net(sk), LINUX_MIB_TLSCURRRXDEVICE);
 		} else {
-			rc = tls_set_sw_offload(sk, 0);
+			rc = tls_set_sw_offload(sk, 0,
+						update ? crypto_info : NULL);
 			if (rc)
 				goto err_crypto_info;
 			TLS_INC_STATS(sock_net(sk), LINUX_MIB_TLSRXSW);
 			TLS_INC_STATS(sock_net(sk), LINUX_MIB_TLSCURRRXSW);
 			conf = TLS_SW;
 		}
-		tls_sw_strparser_arm(sk, ctx);
+		if (!update)
+			tls_sw_strparser_arm(sk, ctx);
 	}
 
 	if (tx)