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>

net/tls/tls.h

@@ -145,7 +145,8 @@ void tls_err_abort(struct sock *sk, int err);
 int init_prot_info(struct tls_prot_info *prot,
 		   const struct tls_crypto_info *crypto_info,
 		   const struct tls_cipher_desc *cipher_desc);
-int tls_set_sw_offload(struct sock *sk, int tx);
+int tls_set_sw_offload(struct sock *sk, int tx,
+		       struct tls_crypto_info *new_crypto_info);
 void tls_update_rx_zc_capable(struct tls_context *tls_ctx);
 void tls_sw_strparser_arm(struct sock *sk, struct tls_context *ctx);
 void tls_sw_strparser_done(struct tls_context *tls_ctx);

net/tls/tls_device.c

@@ -1227,7 +1227,7 @@ int tls_set_device_offload_rx(struct sock *sk, struct tls_context *ctx)
 	context->resync_nh_reset = 1;
 
 	ctx->priv_ctx_rx = context;
-	rc = tls_set_sw_offload(sk, 0);
+	rc = tls_set_sw_offload(sk, 0, NULL);
 	if (rc)
 		goto release_ctx;
 

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) &&
+	if ((skb_queue_empty_lockless(&ctx->rx_list) &&
 	     !tls_strp_msg_ready(ctx) &&
-	    sk_psock_queue_empty(psock))
+	     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 *crypto_info, *alt_crypto_info;
-	struct tls_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;
 
@@ -633,17 +636,33 @@ 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)) {
-	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) {
 		rc = -EFAULT;
 		goto err_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);
@@ -687,13 +707,15 @@ 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;
 		}
+		if (!update)
 			tls_sw_strparser_arm(sk, ctx);
 	}
 

net/tls/tls_sw.c

@@ -2716,12 +2716,22 @@ int init_prot_info(struct tls_prot_info *prot,
 	return 0;
 }
 
-int tls_set_sw_offload(struct sock *sk, int tx)
+static void tls_finish_key_update(struct sock *sk, struct tls_context *tls_ctx)
 {
+	struct tls_sw_context_rx *ctx = tls_ctx->priv_ctx_rx;
+
+	WRITE_ONCE(ctx->key_update_pending, false);
+	/* wake-up pre-existing poll() */
+	ctx->saved_data_ready(sk);
+}
+
+int tls_set_sw_offload(struct sock *sk, int tx,
+		       struct tls_crypto_info *new_crypto_info)
+{
+	struct tls_crypto_info *crypto_info, *src_crypto_info;
 	struct tls_sw_context_tx *sw_ctx_tx = NULL;
 	struct tls_sw_context_rx *sw_ctx_rx = NULL;
 	const struct tls_cipher_desc *cipher_desc;
-	struct tls_crypto_info *crypto_info;
 	char *iv, *rec_seq, *key, *salt;
 	struct cipher_context *cctx;
 	struct tls_prot_info *prot;
@@ -2733,45 +2743,47 @@ int tls_set_sw_offload(struct sock *sk, int tx)
 	ctx = tls_get_ctx(sk);
 	prot = &ctx->prot_info;
 
+	/* new_crypto_info != NULL means rekey */
+	if (!new_crypto_info) {
 		if (tx) {
 			ctx->priv_ctx_tx = init_ctx_tx(ctx, sk);
 			if (!ctx->priv_ctx_tx)
 				return -ENOMEM;
+		} else {
+			ctx->priv_ctx_rx = init_ctx_rx(ctx);
+			if (!ctx->priv_ctx_rx)
+				return -ENOMEM;
+		}
+	}
 
+	if (tx) {
 		sw_ctx_tx = ctx->priv_ctx_tx;
 		crypto_info = &ctx->crypto_send.info;
 		cctx = &ctx->tx;
 		aead = &sw_ctx_tx->aead_send;
 	} else {
-		ctx->priv_ctx_rx = init_ctx_rx(ctx);
-		if (!ctx->priv_ctx_rx)
-			return -ENOMEM;
-
 		sw_ctx_rx = ctx->priv_ctx_rx;
 		crypto_info = &ctx->crypto_recv.info;
 		cctx = &ctx->rx;
 		aead = &sw_ctx_rx->aead_recv;
-		sw_ctx_rx->key_update_pending = false;
 	}
 
-	cipher_desc = get_cipher_desc(crypto_info->cipher_type);
+	src_crypto_info = new_crypto_info ?: crypto_info;
+
+	cipher_desc = get_cipher_desc(src_crypto_info->cipher_type);
 	if (!cipher_desc) {
 		rc = -EINVAL;
 		goto free_priv;
 	}
 
-	rc = init_prot_info(prot, crypto_info, cipher_desc);
+	rc = init_prot_info(prot, src_crypto_info, cipher_desc);
 	if (rc)
 		goto free_priv;
 
-	iv = crypto_info_iv(crypto_info, cipher_desc);
+	iv = crypto_info_iv(src_crypto_info, cipher_desc);
-	key = crypto_info_key(crypto_info, cipher_desc);
+	key = crypto_info_key(src_crypto_info, cipher_desc);
-	salt = crypto_info_salt(crypto_info, cipher_desc);
+	salt = crypto_info_salt(src_crypto_info, cipher_desc);
-	rec_seq = crypto_info_rec_seq(crypto_info, cipher_desc);
+	rec_seq = crypto_info_rec_seq(src_crypto_info, cipher_desc);
-
-	memcpy(cctx->iv, salt, cipher_desc->salt);
-	memcpy(cctx->iv + cipher_desc->salt, iv, cipher_desc->iv);
-	memcpy(cctx->rec_seq, rec_seq, cipher_desc->rec_seq);
 
 	if (!*aead) {
 		*aead = crypto_alloc_aead(cipher_desc->cipher_name, 0, 0);
@@ -2784,20 +2796,30 @@ int tls_set_sw_offload(struct sock *sk, int tx)
 
 	ctx->push_pending_record = tls_sw_push_pending_record;
 
+	/* setkey is the last operation that could fail during a
+	 * rekey. if it succeeds, we can start modifying the
+	 * context.
+	 */
 	rc = crypto_aead_setkey(*aead, key, cipher_desc->key);
-	if (rc)
+	if (rc) {
+		if (new_crypto_info)
+			goto out;
+		else
 			goto free_aead;
+	}
 
+	if (!new_crypto_info) {
 		rc = crypto_aead_setauthsize(*aead, prot->tag_size);
 		if (rc)
 			goto free_aead;
+	}
 
-	if (sw_ctx_rx) {
+	if (!tx && !new_crypto_info) {
 		tfm = crypto_aead_tfm(sw_ctx_rx->aead_recv);
 
 		tls_update_rx_zc_capable(ctx);
 		sw_ctx_rx->async_capable =
-			crypto_info->version != TLS_1_3_VERSION &&
+			src_crypto_info->version != TLS_1_3_VERSION &&
 			!!(tfm->__crt_alg->cra_flags & CRYPTO_ALG_ASYNC);
 
 		rc = tls_strp_init(&sw_ctx_rx->strp, sk);
@@ -2805,12 +2827,26 @@ int tls_set_sw_offload(struct sock *sk, int tx)
 			goto free_aead;
 	}
 
+	memcpy(cctx->iv, salt, cipher_desc->salt);
+	memcpy(cctx->iv + cipher_desc->salt, iv, cipher_desc->iv);
+	memcpy(cctx->rec_seq, rec_seq, cipher_desc->rec_seq);
+
+	if (new_crypto_info) {
+		unsafe_memcpy(crypto_info, new_crypto_info,
+			      cipher_desc->crypto_info,
+			      /* size was checked in do_tls_setsockopt_conf */);
+		memzero_explicit(new_crypto_info, cipher_desc->crypto_info);
+		if (!tx)
+			tls_finish_key_update(sk, ctx);
+	}
+
 	goto out;
 
 free_aead:
 	crypto_free_aead(*aead);
 	*aead = NULL;
 free_priv:
+	if (!new_crypto_info) {
 		if (tx) {
 			kfree(ctx->priv_ctx_tx);
 			ctx->priv_ctx_tx = NULL;
@@ -2818,6 +2854,7 @@ free_priv:
 			kfree(ctx->priv_ctx_rx);
 			ctx->priv_ctx_rx = NULL;
 		}
+	}
 out:
 	return rc;
 }