From 3b3009ea8abb713b022d94fba95ec270cf6e7eae Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Mon, 17 Apr 2023 10:32:26 -0400 Subject: net/handshake: Create a NETLINK service for handling handshake requests When a kernel consumer needs a transport layer security session, it first needs a handshake to negotiate and establish a session. This negotiation can be done in user space via one of the several existing library implementations, or it can be done in the kernel. No in-kernel handshake implementations yet exist. In their absence, we add a netlink service that can: a. Notify a user space daemon that a handshake is needed. b. Once notified, the daemon calls the kernel back via this netlink service to get the handshake parameters, including an open socket on which to establish the session. c. Once the handshake is complete, the daemon reports the session status and other information via a second netlink operation. This operation marks that it is safe for the kernel to use the open socket and the security session established there. The notification service uses a multicast group. Each handshake mechanism (eg, tlshd) adopts its own group number so that the handshake services are completely independent of one another. The kernel can then tell via netlink_has_listeners() whether a handshake service is active and prepared to handle a handshake request. A new netlink operation, ACCEPT, acts like accept(2) in that it instantiates a file descriptor in the user space daemon's fd table. If this operation is successful, the reply carries the fd number, which can be treated as an open and ready file descriptor. While user space is performing the handshake, the kernel keeps its muddy paws off the open socket. A second new netlink operation, DONE, indicates that the user space daemon is finished with the socket and it is safe for the kernel to use again. The operation also indicates whether a session was established successfully. Signed-off-by: Chuck Lever Signed-off-by: Jakub Kicinski --- net/handshake/netlink.c | 312 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 312 insertions(+) create mode 100644 net/handshake/netlink.c (limited to 'net/handshake/netlink.c') diff --git a/net/handshake/netlink.c b/net/handshake/netlink.c new file mode 100644 index 000000000000..7264cac04047 --- /dev/null +++ b/net/handshake/netlink.c @@ -0,0 +1,312 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Generic netlink handshake service + * + * Author: Chuck Lever + * + * Copyright (c) 2023, Oracle and/or its affiliates. + */ + +#include +#include +#include +#include +#include +#include + +#include +#include +#include + +#include +#include "handshake.h" +#include "genl.h" + +#include + +/** + * handshake_genl_notify - Notify handlers that a request is waiting + * @net: target network namespace + * @proto: handshake protocol + * @flags: memory allocation control flags + * + * Returns zero on success or a negative errno if notification failed. + */ +int handshake_genl_notify(struct net *net, const struct handshake_proto *proto, + gfp_t flags) +{ + struct sk_buff *msg; + void *hdr; + + if (!genl_has_listeners(&handshake_nl_family, net, + proto->hp_handler_class)) + return -ESRCH; + + msg = genlmsg_new(GENLMSG_DEFAULT_SIZE, GFP_KERNEL); + if (!msg) + return -ENOMEM; + + hdr = genlmsg_put(msg, 0, 0, &handshake_nl_family, 0, + HANDSHAKE_CMD_READY); + if (!hdr) + goto out_free; + + if (nla_put_u32(msg, HANDSHAKE_A_ACCEPT_HANDLER_CLASS, + proto->hp_handler_class) < 0) { + genlmsg_cancel(msg, hdr); + goto out_free; + } + + genlmsg_end(msg, hdr); + return genlmsg_multicast_netns(&handshake_nl_family, net, msg, + 0, proto->hp_handler_class, flags); + +out_free: + nlmsg_free(msg); + return -EMSGSIZE; +} + +/** + * handshake_genl_put - Create a generic netlink message header + * @msg: buffer in which to create the header + * @info: generic netlink message context + * + * Returns a ready-to-use header, or NULL. + */ +struct nlmsghdr *handshake_genl_put(struct sk_buff *msg, + struct genl_info *info) +{ + return genlmsg_put(msg, info->snd_portid, info->snd_seq, + &handshake_nl_family, 0, info->genlhdr->cmd); +} +EXPORT_SYMBOL(handshake_genl_put); + +/* + * dup() a kernel socket for use as a user space file descriptor + * in the current process. The kernel socket must have an + * instatiated struct file. + * + * Implicit argument: "current()" + */ +static int handshake_dup(struct socket *sock) +{ + struct file *file; + int newfd; + + if (!sock->file) + return -EBADF; + + file = get_file(sock->file); + newfd = get_unused_fd_flags(O_CLOEXEC); + if (newfd < 0) { + fput(file); + return newfd; + } + + fd_install(newfd, file); + return newfd; +} + +int handshake_nl_accept_doit(struct sk_buff *skb, struct genl_info *info) +{ + struct net *net = sock_net(skb->sk); + struct handshake_net *hn = handshake_pernet(net); + struct handshake_req *req = NULL; + struct socket *sock; + int class, fd, err; + + err = -EOPNOTSUPP; + if (!hn) + goto out_status; + + err = -EINVAL; + if (GENL_REQ_ATTR_CHECK(info, HANDSHAKE_A_ACCEPT_HANDLER_CLASS)) + goto out_status; + class = nla_get_u32(info->attrs[HANDSHAKE_A_ACCEPT_HANDLER_CLASS]); + + err = -EAGAIN; + req = handshake_req_next(hn, class); + if (!req) + goto out_status; + + sock = req->hr_sk->sk_socket; + fd = handshake_dup(sock); + if (fd < 0) { + err = fd; + goto out_complete; + } + err = req->hr_proto->hp_accept(req, info, fd); + if (err) + goto out_complete; + + trace_handshake_cmd_accept(net, req, req->hr_sk, fd); + return 0; + +out_complete: + handshake_complete(req, -EIO, NULL); + fput(sock->file); +out_status: + trace_handshake_cmd_accept_err(net, req, NULL, err); + return err; +} + +int handshake_nl_done_doit(struct sk_buff *skb, struct genl_info *info) +{ + struct net *net = sock_net(skb->sk); + struct socket *sock = NULL; + struct handshake_req *req; + int fd, status, err; + + if (GENL_REQ_ATTR_CHECK(info, HANDSHAKE_A_DONE_SOCKFD)) + return -EINVAL; + fd = nla_get_u32(info->attrs[HANDSHAKE_A_DONE_SOCKFD]); + + err = 0; + sock = sockfd_lookup(fd, &err); + if (err) { + err = -EBADF; + goto out_status; + } + + req = handshake_req_hash_lookup(sock->sk); + if (!req) { + err = -EBUSY; + fput(sock->file); + goto out_status; + } + + trace_handshake_cmd_done(net, req, sock->sk, fd); + + status = -EIO; + if (info->attrs[HANDSHAKE_A_DONE_STATUS]) + status = nla_get_u32(info->attrs[HANDSHAKE_A_DONE_STATUS]); + + handshake_complete(req, status, info); + fput(sock->file); + return 0; + +out_status: + trace_handshake_cmd_done_err(net, req, sock->sk, err); + return err; +} + +static unsigned int handshake_net_id; + +static int __net_init handshake_net_init(struct net *net) +{ + struct handshake_net *hn = net_generic(net, handshake_net_id); + unsigned long tmp; + struct sysinfo si; + + /* + * Arbitrary limit to prevent handshakes that do not make + * progress from clogging up the system. The cap scales up + * with the amount of physical memory on the system. + */ + si_meminfo(&si); + tmp = si.totalram / (25 * si.mem_unit); + hn->hn_pending_max = clamp(tmp, 3UL, 50UL); + + spin_lock_init(&hn->hn_lock); + hn->hn_pending = 0; + hn->hn_flags = 0; + INIT_LIST_HEAD(&hn->hn_requests); + return 0; +} + +static void __net_exit handshake_net_exit(struct net *net) +{ + struct handshake_net *hn = net_generic(net, handshake_net_id); + struct handshake_req *req; + LIST_HEAD(requests); + + /* + * Drain the net's pending list. Requests that have been + * accepted and are in progress will be destroyed when + * the socket is closed. + */ + spin_lock(&hn->hn_lock); + set_bit(HANDSHAKE_F_NET_DRAINING, &hn->hn_flags); + list_splice_init(&requests, &hn->hn_requests); + spin_unlock(&hn->hn_lock); + + while (!list_empty(&requests)) { + req = list_first_entry(&requests, struct handshake_req, hr_list); + list_del(&req->hr_list); + + /* + * Requests on this list have not yet been + * accepted, so they do not have an fd to put. + */ + + handshake_complete(req, -ETIMEDOUT, NULL); + } +} + +static struct pernet_operations __net_initdata handshake_genl_net_ops = { + .init = handshake_net_init, + .exit = handshake_net_exit, + .id = &handshake_net_id, + .size = sizeof(struct handshake_net), +}; + +/** + * handshake_pernet - Get the handshake private per-net structure + * @net: network namespace + * + * Returns a pointer to the net's private per-net structure for the + * handshake module, or NULL if handshake_init() failed. + */ +struct handshake_net *handshake_pernet(struct net *net) +{ + return handshake_net_id ? + net_generic(net, handshake_net_id) : NULL; +} + +static int __init handshake_init(void) +{ + int ret; + + ret = handshake_req_hash_init(); + if (ret) { + pr_warn("handshake: hash initialization failed (%d)\n", ret); + return ret; + } + + ret = genl_register_family(&handshake_nl_family); + if (ret) { + pr_warn("handshake: netlink registration failed (%d)\n", ret); + handshake_req_hash_destroy(); + return ret; + } + + /* + * ORDER: register_pernet_subsys must be done last. + * + * If initialization does not make it past pernet_subsys + * registration, then handshake_net_id will remain 0. That + * shunts the handshake consumer API to return ENOTSUPP + * to prevent it from dereferencing something that hasn't + * been allocated. + */ + ret = register_pernet_subsys(&handshake_genl_net_ops); + if (ret) { + pr_warn("handshake: pernet registration failed (%d)\n", ret); + genl_unregister_family(&handshake_nl_family); + handshake_req_hash_destroy(); + } + + return ret; +} + +static void __exit handshake_exit(void) +{ + unregister_pernet_subsys(&handshake_genl_net_ops); + handshake_net_id = 0; + + handshake_req_hash_destroy(); + genl_unregister_family(&handshake_nl_family); +} + +module_init(handshake_init); +module_exit(handshake_exit); -- cgit From 88232ec1ec5ecf4aa5de439cff3d5e2b7adcac93 Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Mon, 17 Apr 2023 10:32:39 -0400 Subject: net/handshake: Add Kunit tests for the handshake consumer API These verify the API contracts and help exercise lifetime rules for consumer sockets and handshake_req structures. One way to run these tests: ./tools/testing/kunit/kunit.py run --kunitconfig ./net/handshake/.kunitconfig Signed-off-by: Chuck Lever Signed-off-by: Jakub Kicinski --- net/handshake/netlink.c | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'net/handshake/netlink.c') diff --git a/net/handshake/netlink.c b/net/handshake/netlink.c index 7264cac04047..8ea0ff993f9f 100644 --- a/net/handshake/netlink.c +++ b/net/handshake/netlink.c @@ -18,6 +18,8 @@ #include #include +#include + #include #include "handshake.h" #include "genl.h" @@ -38,6 +40,10 @@ int handshake_genl_notify(struct net *net, const struct handshake_proto *proto, struct sk_buff *msg; void *hdr; + /* Disable notifications during unit testing */ + if (!test_bit(HANDSHAKE_F_PROTO_NOTIFY, &proto->hp_flags)) + return 0; + if (!genl_has_listeners(&handshake_nl_family, net, proto->hp_handler_class)) return -ESRCH; @@ -262,6 +268,7 @@ struct handshake_net *handshake_pernet(struct net *net) return handshake_net_id ? net_generic(net, handshake_net_id) : NULL; } +EXPORT_SYMBOL_IF_KUNIT(handshake_pernet); static int __init handshake_init(void) { -- cgit From 6aa445e39693bff9c98b12f960e66b4e18c7378b Mon Sep 17 00:00:00 2001 From: Geert Uytterhoeven Date: Thu, 20 Apr 2023 19:37:23 +0200 Subject: net/handshake: Fix section mismatch in handshake_exit If CONFIG_NET_NS=n (e.g. m68k/defconfig): WARNING: modpost: vmlinux.o: section mismatch in reference: handshake_exit (section: .exit.text) -> handshake_genl_net_ops (section: .init.data) ERROR: modpost: Section mismatches detected. Fix this by dropping the __net_initdata tag from handshake_genl_net_ops. Fixes: 3b3009ea8abb713b ("net/handshake: Create a NETLINK service for handling handshake requests") Reported-by: noreply@ellerman.id.au Closes: http://kisskb.ellerman.id.au/kisskb/buildresult/14912987 Signed-off-by: Geert Uytterhoeven Reviewed-by: Chuck Lever Link: https://lore.kernel.org/r/20230420173723.3773434-1-geert@linux-m68k.org Signed-off-by: Jakub Kicinski --- net/handshake/netlink.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'net/handshake/netlink.c') diff --git a/net/handshake/netlink.c b/net/handshake/netlink.c index 8ea0ff993f9f..35c9c445e0b8 100644 --- a/net/handshake/netlink.c +++ b/net/handshake/netlink.c @@ -249,7 +249,7 @@ static void __net_exit handshake_net_exit(struct net *net) } } -static struct pernet_operations __net_initdata handshake_genl_net_ops = { +static struct pernet_operations handshake_genl_net_ops = { .init = handshake_net_init, .exit = handshake_net_exit, .id = &handshake_net_id, -- cgit From a095326e2c0f33743ce8e887d5b90edf3f36cced Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Thu, 11 May 2023 11:47:09 -0400 Subject: net/handshake: Remove unneeded check from handshake_dup() handshake_req_submit() now verifies that the socket has a file. Fixes: 3b3009ea8abb ("net/handshake: Create a NETLINK service for handling handshake requests") Reviewed-by: Simon Horman Signed-off-by: Chuck Lever Signed-off-by: Jakub Kicinski --- net/handshake/netlink.c | 3 --- 1 file changed, 3 deletions(-) (limited to 'net/handshake/netlink.c') diff --git a/net/handshake/netlink.c b/net/handshake/netlink.c index 35c9c445e0b8..7ec8a76c3c8a 100644 --- a/net/handshake/netlink.c +++ b/net/handshake/netlink.c @@ -99,9 +99,6 @@ static int handshake_dup(struct socket *sock) struct file *file; int newfd; - if (!sock->file) - return -EBADF; - file = get_file(sock->file); newfd = get_unused_fd_flags(O_CLOEXEC); if (newfd < 0) { -- cgit From 7ea9c1ec66bc099b0bfba961a8a46dfe25d7d8e4 Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Thu, 11 May 2023 11:47:40 -0400 Subject: net/handshake: Fix handshake_dup() ref counting If get_unused_fd_flags() fails, we ended up calling fput(sock->file) twice. Reported-by: Dan Carpenter Suggested-by: Paolo Abeni Fixes: 3b3009ea8abb ("net/handshake: Create a NETLINK service for handling handshake requests") Signed-off-by: Chuck Lever Signed-off-by: Jakub Kicinski --- net/handshake/netlink.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'net/handshake/netlink.c') diff --git a/net/handshake/netlink.c b/net/handshake/netlink.c index 7ec8a76c3c8a..f5dc170689d9 100644 --- a/net/handshake/netlink.c +++ b/net/handshake/netlink.c @@ -139,15 +139,16 @@ int handshake_nl_accept_doit(struct sk_buff *skb, struct genl_info *info) goto out_complete; } err = req->hr_proto->hp_accept(req, info, fd); - if (err) + if (err) { + fput(sock->file); goto out_complete; + } trace_handshake_cmd_accept(net, req, req->hr_sk, fd); return 0; out_complete: handshake_complete(req, -EIO, NULL); - fput(sock->file); out_status: trace_handshake_cmd_accept_err(net, req, NULL, err); return err; -- cgit From 7afc6d0a107ffbd448c96eb2458b9e64a5af7860 Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Thu, 11 May 2023 11:48:13 -0400 Subject: net/handshake: Fix uninitialized local variable trace_handshake_cmd_done_err() simply records the pointer in @req, so initializing it to NULL is sufficient and safe. Reported-by: Dan Carpenter Fixes: 3b3009ea8abb ("net/handshake: Create a NETLINK service for handling handshake requests") Reviewed-by: Simon Horman Signed-off-by: Chuck Lever Signed-off-by: Jakub Kicinski --- net/handshake/netlink.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'net/handshake/netlink.c') diff --git a/net/handshake/netlink.c b/net/handshake/netlink.c index f5dc170689d9..16a4bde648ba 100644 --- a/net/handshake/netlink.c +++ b/net/handshake/netlink.c @@ -157,8 +157,8 @@ out_status: int handshake_nl_done_doit(struct sk_buff *skb, struct genl_info *info) { struct net *net = sock_net(skb->sk); + struct handshake_req *req = NULL; struct socket *sock = NULL; - struct handshake_req *req; int fd, status, err; if (GENL_REQ_ATTR_CHECK(info, HANDSHAKE_A_DONE_SOCKFD)) -- cgit From fc490880e39d86c65ab2bcbd357af1950fa55e48 Mon Sep 17 00:00:00 2001 From: Chuck Lever Date: Thu, 11 May 2023 11:48:45 -0400 Subject: net/handshake: handshake_genl_notify() shouldn't ignore @flags Reported-by: Dan Carpenter Fixes: 3b3009ea8abb ("net/handshake: Create a NETLINK service for handling handshake requests") Reviewed-by: Simon Horman Signed-off-by: Chuck Lever Signed-off-by: Jakub Kicinski --- net/handshake/netlink.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'net/handshake/netlink.c') diff --git a/net/handshake/netlink.c b/net/handshake/netlink.c index 16a4bde648ba..1086653e1fad 100644 --- a/net/handshake/netlink.c +++ b/net/handshake/netlink.c @@ -48,7 +48,7 @@ int handshake_genl_notify(struct net *net, const struct handshake_proto *proto, proto->hp_handler_class)) return -ESRCH; - msg = genlmsg_new(GENLMSG_DEFAULT_SIZE, GFP_KERNEL); + msg = genlmsg_new(GENLMSG_DEFAULT_SIZE, flags); if (!msg) return -ENOMEM; -- cgit