Re: [PATCH v2 12/15] SUNRPC: Add RPC-with-TLS support to xprtsock.c

[Jeff Layton <jlayton@kernel.org>]

On Mon, 2022-06-06 at 10:51 -0400, Chuck Lever wrote:
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> ---
>  include/linux/sunrpc/xprtsock.h |    1 
>  net/sunrpc/xprtsock.c           |  243 ++++++++++++++++++++++++++++++++-------
>  2 files changed, 201 insertions(+), 43 deletions(-)
> 
> diff --git a/include/linux/sunrpc/xprtsock.h b/include/linux/sunrpc/xprtsock.h
> index e0b6009f1f69..eaf3d705f758 100644
> --- a/include/linux/sunrpc/xprtsock.h
> +++ b/include/linux/sunrpc/xprtsock.h
> @@ -57,6 +57,7 @@ struct sock_xprt {
>  	struct work_struct	error_worker;
>  	struct work_struct	recv_worker;
>  	struct mutex		recv_mutex;
> +	struct completion	handshake_done;
>  	struct sockaddr_storage	srcaddr;
>  	unsigned short		srcport;
>  	int			xprt_err;
> diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
> index a4fee00412d4..63fe97ede573 100644
> --- a/net/sunrpc/xprtsock.c
> +++ b/net/sunrpc/xprtsock.c
> @@ -48,6 +48,7 @@
>  #include <net/udp.h>
>  #include <net/tcp.h>
>  #include <net/tls.h>
> +#include <net/tlsh.h>
>  
>  #include <linux/bvec.h>
>  #include <linux/highmem.h>
> @@ -197,6 +198,11 @@ static struct ctl_table sunrpc_table[] = {
>   */
>  #define XS_IDLE_DISC_TO		(5U * 60 * HZ)
>  
> +/*
> + * TLS handshake timeout.
> + */
> +#define XS_TLS_HANDSHAKE_TO    (20U * HZ)
> +
>  #if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
>  # undef  RPC_DEBUG_DATA
>  # define RPCDBG_FACILITY	RPCDBG_TRANS
> @@ -1254,6 +1260,8 @@ static void xs_reset_transport(struct sock_xprt *transport)
>  	if (atomic_read(&transport->xprt.swapper))
>  		sk_clear_memalloc(sk);
>  
> +	/* TODO: Maybe send a TLS Closure alert */
> +
>  	kernel_sock_shutdown(sock, SHUT_RDWR);
>  
>  	mutex_lock(&transport->recv_mutex);
> @@ -2424,6 +2432,147 @@ static void xs_tcp_setup_socket(struct work_struct *work)
>  
>  #if IS_ENABLED(CONFIG_TLS)
>  
> +/**
> + * xs_tls_handshake_done - TLS handshake completion handler
> + * @data: address of xprt to wake
> + * @status: status of handshake
> + *
> + */
> +static void xs_tls_handshake_done(void *data, int status)
> +{
> +	struct rpc_xprt *xprt = data;
> +	struct sock_xprt *transport =
> +				container_of(xprt, struct sock_xprt, xprt);
> +
> +	transport->xprt_err = status ? -EACCES : 0;
> +	complete(&transport->handshake_done);
> +	xprt_put(xprt);
> +}
> +
> +static int xs_tls_handshake_sync(struct rpc_xprt *xprt, unsigned int xprtsec)
> +{
> +	struct sock_xprt *transport =
> +				container_of(xprt, struct sock_xprt, xprt);
> +	int rc;
> +
> +	init_completion(&transport->handshake_done);
> +	set_bit(XPRT_SOCK_IGNORE_RECV, &transport->sock_state);
> +
> +	transport->xprt_err = -ETIMEDOUT;
> +	switch (xprtsec) {
> +	case RPC_XPRTSEC_TLS_X509:
> +		rc = tls_client_hello_x509(transport->sock,
> +					   xs_tls_handshake_done, xprt_get(xprt),
> +					   TLSH_DEFAULT_PRIORITIES, TLSH_NO_PEERID,
> +					   TLSH_NO_CERT);
> +		break;
> +	case RPC_XPRTSEC_TLS_PSK:
> +		rc = tls_client_hello_psk(transport->sock, xs_tls_handshake_done,
> +					  xprt_get(xprt), TLSH_DEFAULT_PRIORITIES,
> +					  TLSH_NO_PEERID);
> +		break;
> +	default:
> +		rc = -EACCES;
> +	}
> +	if (rc)
> +		goto out;
> +
> +	rc = wait_for_completion_interruptible_timeout(&transport->handshake_done,
> +						       XS_TLS_HANDSHAKE_TO);

Should this be interruptible or killable? I'm not sure we want to give
up on a non-fatal signal, do we? (e.g. SIGCHLD).

Actually...it looks like this function always runs in workqueue context,
so this should probably just be wait_for_completion...or better yet,
consider doing this asynchronously so we don't block a workqueue thread.

> +	if (rc < 0)
> +		goto out;
> +
> +	rc = transport->xprt_err;
> +
> +out:
> +	xs_stream_reset_connect(transport);
> +	clear_bit(XPRT_SOCK_IGNORE_RECV, &transport->sock_state);
> +	return rc;
> +}
> +
> +/*
> + * Transfer the connected socket to @dst_transport, then mark that
> + * xprt CONNECTED.
> + */
> +static int xs_tls_finish_connecting(struct rpc_xprt *src_xprt,
> +				    struct sock_xprt *dst_transport)
> +{
> +	struct sock_xprt *src_transport =
> +			container_of(src_xprt, struct sock_xprt, xprt);
> +	struct rpc_xprt *dst_xprt = &dst_transport->xprt;
> +
> +	if (!dst_transport->inet) {
> +		struct socket *sock = src_transport->sock;
> +		struct sock *sk = sock->sk;
> +
> +		/* Avoid temporary address, they are bad for long-lived
> +		 * connections such as NFS mounts.
> +		 * RFC4941, section 3.6 suggests that:
> +		 *    Individual applications, which have specific
> +		 *    knowledge about the normal duration of connections,
> +		 *    MAY override this as appropriate.
> +		 */
> +		if (xs_addr(dst_xprt)->sa_family == PF_INET6) {
> +			ip6_sock_set_addr_preferences(sk,
> +				IPV6_PREFER_SRC_PUBLIC);
> +		}
> +
> +		xs_tcp_set_socket_timeouts(dst_xprt, sock);
> +		tcp_sock_set_nodelay(sk);
> +
> +		lock_sock(sk);
> +
> +		/*
> +		 * @sk is already connected, so it now has the RPC callbacks.
> +		 * Reach into @src_transport to save the original ones.
> +		 */
> +		dst_transport->old_data_ready = src_transport->old_data_ready;
> +		dst_transport->old_state_change = src_transport->old_state_change;
> +		dst_transport->old_write_space = src_transport->old_write_space;
> +		dst_transport->old_error_report = src_transport->old_error_report;
> +		sk->sk_user_data = dst_xprt;
> +
> +		/* socket options */
> +		sock_reset_flag(sk, SOCK_LINGER);
> +
> +		xprt_clear_connected(dst_xprt);
> +
> +		dst_transport->sock = sock;
> +		dst_transport->inet = sk;
> +		dst_transport->file = src_transport->file;
> +
> +		release_sock(sk);
> +
> +		/* Reset src_transport before shutting down its clnt */
> +		mutex_lock(&src_transport->recv_mutex);
> +		src_transport->inet = NULL;
> +		src_transport->sock = NULL;
> +		src_transport->file = NULL;
> +
> +		xprt_clear_connected(src_xprt);
> +		xs_sock_reset_connection_flags(src_xprt);
> +		xs_stream_reset_connect(src_transport);
> +		mutex_unlock(&src_transport->recv_mutex);
> +	}
> +
> +	if (!xprt_bound(dst_xprt))
> +		return -ENOTCONN;
> +
> +	xs_set_memalloc(dst_xprt);
> +
> +	if (!xprt_test_and_set_connected(dst_xprt)) {
> +		dst_xprt->connect_cookie++;
> +		clear_bit(XPRT_SOCK_CONNECTING, &dst_transport->sock_state);
> +		xprt_clear_connecting(dst_xprt);
> +
> +		dst_xprt->stat.connect_count++;
> +		dst_xprt->stat.connect_time += (long)jiffies -
> +					   dst_xprt->stat.connect_start;
> +		xs_run_error_worker(dst_transport, XPRT_SOCK_WAKE_PENDING);
> +	}
> +	return 0;
> +}
> +
>  /**
>   * xs_tls_connect - establish a TLS session on a socket
>   * @work: queued work item
> @@ -2433,61 +2582,70 @@ static void xs_tls_connect(struct work_struct *work)
>  {
>  	struct sock_xprt *transport =
>  		container_of(work, struct sock_xprt, connect_worker.work);
> +	struct rpc_create_args args = {
> +		.net		= transport->xprt.xprt_net,
> +		.protocol	= transport->xprt.prot,
> +		.address	= (struct sockaddr *)&transport->xprt.addr,
> +		.addrsize	= transport->xprt.addrlen,
> +		.timeout	= transport->xprtsec_clnt->cl_timeout,
> +		.servername	= transport->xprt.servername,
> +		.nodename	= transport->xprtsec_clnt->cl_nodename,
> +		.program	= transport->xprtsec_clnt->cl_program,
> +		.prognumber	= transport->xprtsec_clnt->cl_prog,
> +		.version	= transport->xprtsec_clnt->cl_vers,
> +		.authflavor	= RPC_AUTH_TLS,
> +		.cred		= transport->xprtsec_clnt->cl_cred,
> +		.xprtsec	= RPC_XPRTSEC_NONE,
> +	};
> +	unsigned int pflags = current->flags;
>  	struct rpc_clnt *clnt;
> +	struct rpc_xprt *xprt;
> +	int status;
>  
> -	clnt = transport->xprtsec_clnt;
> -	transport->xprtsec_clnt = NULL;
> +	if (atomic_read(&transport->xprt.swapper))
> +		current->flags |= PF_MEMALLOC;
> +
> +	xs_stream_start_connect(transport);
> +
> +	clnt = rpc_create(&args);
>  	if (IS_ERR(clnt))
>  		goto out_unlock;
> +	rcu_read_lock();
> +	xprt = xprt_get(rcu_dereference(clnt->cl_xprt));
> +	rcu_read_unlock();
>  
> -	xs_tcp_setup_socket(work);
> +	status = xs_tls_handshake_sync(xprt, transport->xprt.xprtsec);
> +	if (status)
> +		goto out_close;
>  
> +	status = xs_tls_finish_connecting(xprt, transport);
> +	if (status)
> +		goto out_close;
> +	trace_rpc_socket_connect(&transport->xprt, transport->sock, 0);
> +
> +	xprt_put(xprt);
>  	rpc_shutdown_client(clnt);
>  
>  out_unlock:
> +	xprt_unlock_connect(&transport->xprt, transport);
> +	current_restore_flags(pflags, PF_MEMALLOC);
> +	transport->xprtsec_clnt = NULL;
>  	return;
> -}
>  
> -static void xs_set_xprtsec_clnt(struct rpc_clnt *clnt, struct rpc_xprt *xprt)
> -{
> -	struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);
> -	struct rpc_create_args args = {
> -		.net		= xprt->xprt_net,
> -		.protocol	= xprt->prot,
> -		.address	= (struct sockaddr *)&xprt->addr,
> -		.addrsize	= xprt->addrlen,
> -		.timeout	= clnt->cl_timeout,
> -		.servername	= xprt->servername,
> -		.nodename	= clnt->cl_nodename,
> -		.program	= clnt->cl_program,
> -		.prognumber	= clnt->cl_prog,
> -		.version	= clnt->cl_vers,
> -		.authflavor	= RPC_AUTH_TLS,
> -		.cred		= clnt->cl_cred,
> -		.xprtsec	= RPC_XPRTSEC_NONE,
> -		.flags		= RPC_CLNT_CREATE_NOPING,
> -	};
> -
> -	switch (xprt->xprtsec) {
> -	case RPC_XPRTSEC_TLS_X509:
> -	case RPC_XPRTSEC_TLS_PSK:
> -		transport->xprtsec_clnt = rpc_create(&args);
> -		break;
> -	default:
> -		transport->xprtsec_clnt = ERR_PTR(-ENOTCONN);
> -	}
> -}
> -
> -#else
> -
> -static void xs_set_xprtsec_clnt(struct rpc_clnt *clnt, struct rpc_xprt *xprt)
> -{
> -	struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt);
> +out_close:
> +	xprt_put(xprt);
> +	rpc_shutdown_client(clnt);
>  
> -	transport->xprtsec_clnt = ERR_PTR(-ENOTCONN);
> +	/* xprt_force_disconnect() wakes tasks with a fixed tk_status code.
> +	 * Wake them first here to ensure they get our tk_status code.
> +	 */
> +	xprt_wake_pending_tasks(&transport->xprt, status);
> +	xs_tcp_force_close(&transport->xprt);
> +	xprt_clear_connecting(&transport->xprt);
> +	goto out_unlock;
>  }
>  
> -#endif /*CONFIG_TLS */
> +#endif /* CONFIG_TLS */
>  
>  /**
>   * xs_connect - connect a socket to a remote endpoint
> @@ -2520,8 +2678,7 @@ static void xs_connect(struct rpc_xprt *xprt, struct rpc_task *task)
>  	} else
>  		dprintk("RPC:       xs_connect scheduled xprt %p\n", xprt);
>  
> -	xs_set_xprtsec_clnt(task->tk_client, xprt);
> -
> +	transport->xprtsec_clnt = task->tk_client;
>  	queue_delayed_work(xprtiod_workqueue,
>  			&transport->connect_worker,
>  			delay);
> 
> 

-- 
Jeff Layton <jlayton@kernel.org>