git: 4f02a7d739b3 - main - inpcb: Remove bogus SO_REUSEPORT(_LB) checks in in_pcbbind()
- Go to: [ bottom of page ] [ top of archives ] [ this month ]
Date: Thu, 12 Dec 2024 14:27:34 UTC
The branch main has been updated by markj:
URL: https://cgit.FreeBSD.org/src/commit/?id=4f02a7d739b354eef38e19b25866f64842d69414
commit 4f02a7d739b354eef38e19b25866f64842d69414
Author: Mark Johnston <markj@FreeBSD.org>
AuthorDate: 2024-12-12 14:06:06 +0000
Commit: Mark Johnston <markj@FreeBSD.org>
CommitDate: 2024-12-12 14:25:15 +0000
inpcb: Remove bogus SO_REUSEPORT(_LB) checks in in_pcbbind()
This check for SO_REUSEPORT was added way back in commit 52b65dbe85faf.
Per the commit log, this commit restricted this port-stealing check to
unicast addresses, and then only if the existing socket does not have
SO_REUSEPORT set. In other words, if there exists a socket bound to
INADDR_ANY, and we bind a socket to INADDR_ANY with the same port, then
the two sockets need not be owned by the same user if the existing
socket has SO_REUSEPORT set.
This is a surprising semantic; bugzilla PR 7713 gives some additional
context. That PR makes a case for the behaviour described above when
binding to a multicast address. But, the SO_REUSEPORT check is only
applied when binding to a non-multicast address, so it doesn't really
make sense. In the PR the committer notes that "unicast applications
don't set SO_REUSEPORT", which makes some sense, but also refers to
"multicast applications that bind to INADDR_ANY", which sounds a bit
suspicious.
OpenBSD performs the multicast check, but not the SO_REUSEPORT check.
DragonflyBSD removed the SO_REUSEPORT (and INADDR_ANY) checks back in
2014 (commit 0323d5fde12a4). NetBSD explicitly copied our logic and
still has it.
The plot thickens: 20 years later, SO_REUSEPORT_LB was ported from
DragonflyBSD: this option provides similar semantics to SO_REUSEPORT,
but for unicast addresses it causes incoming connections/datagrams to be
distributed among all sockets in the group. This commit (1a43cff92a20d)
inverted the check for SO_REUSEPORT while adding one for
SO_REUSEPORT_LB; this appears to have been inadvertent. However:
- apparently no one has noticed that the semantics were changed;
- sockets belonging to different users can now be bound to the same port
so long as they belong to a single lbgroup bound to INADDR_ANY, which
is not correct.
Simply remove the SO_REUSEPORT(_LB) checks, as their original
justification was dubious and their current implementation is wrong; add
some tests.
Reviewed by: glebius
MFC after: 1 month
Sponsored by: Klara, Inc.
Sponsored by: Stormshield
Differential Revision: https://reviews.freebsd.org/D47832
---
sys/netinet/in_pcb.c | 4 +-
sys/netinet6/in6_pcb.c | 4 +-
tests/sys/netinet/socket_afinet.c | 240 +++++++++++++++++++++++++++++++++++++-
3 files changed, 241 insertions(+), 7 deletions(-)
diff --git a/sys/netinet/in_pcb.c b/sys/netinet/in_pcb.c
index cfe3fd65e032..432cae68062a 100644
--- a/sys/netinet/in_pcb.c
+++ b/sys/netinet/in_pcb.c
@@ -925,9 +925,7 @@ in_pcbbind_avail(struct inpcb *inp, const struct in_addr laddr,
(inp->inp_socket->so_type != SOCK_STREAM ||
in_nullhost(t->inp_faddr)) &&
(!in_nullhost(laddr) ||
- !in_nullhost(t->inp_laddr) ||
- (t->inp_socket->so_options & SO_REUSEPORT) ||
- (t->inp_socket->so_options & SO_REUSEPORT_LB) == 0) &&
+ !in_nullhost(t->inp_laddr)) &&
(inp->inp_cred->cr_uid != t->inp_cred->cr_uid))
return (EADDRINUSE);
}
diff --git a/sys/netinet6/in6_pcb.c b/sys/netinet6/in6_pcb.c
index ada5058e56b3..51f2a29918fe 100644
--- a/sys/netinet6/in6_pcb.c
+++ b/sys/netinet6/in6_pcb.c
@@ -245,9 +245,7 @@ in6_pcbbind_avail(struct inpcb *inp, const struct sockaddr_in6 *sin6,
(inp->inp_socket->so_type != SOCK_STREAM ||
IN6_IS_ADDR_UNSPECIFIED(&t->in6p_faddr)) &&
(!IN6_IS_ADDR_UNSPECIFIED(laddr) ||
- !IN6_IS_ADDR_UNSPECIFIED(&t->in6p_laddr) ||
- (t->inp_socket->so_options & SO_REUSEPORT) ||
- (t->inp_socket->so_options & SO_REUSEPORT_LB) == 0) &&
+ !IN6_IS_ADDR_UNSPECIFIED(&t->in6p_laddr)) &&
(inp->inp_cred->cr_uid != t->inp_cred->cr_uid))
return (EADDRINUSE);
diff --git a/tests/sys/netinet/socket_afinet.c b/tests/sys/netinet/socket_afinet.c
index 7076f084719a..ba8c03af46a6 100644
--- a/tests/sys/netinet/socket_afinet.c
+++ b/tests/sys/netinet/socket_afinet.c
@@ -2,6 +2,7 @@
* SPDX-License-Identifier: BSD-2-Clause
*
* Copyright (c) 2019 Bjoern A. Zeeb
+ * Copyright (c) 2024 Stormshield
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
@@ -25,11 +26,17 @@
* SUCH DAMAGE.
*/
-#include <sys/cdefs.h>
+#include <sys/param.h>
#include <sys/socket.h>
+#include <sys/wait.h>
+
#include <netinet/in.h>
+
#include <errno.h>
#include <poll.h>
+#include <pwd.h>
+#include <stdio.h>
+#include <unistd.h>
#include <atf-c.h>
@@ -281,6 +288,235 @@ ATF_TC_BODY(socket_afinet_stream_reconnect, tc)
ATF_CHECK_EQ(0, rc);
}
+/*
+ * Make sure that unprivileged users can't set the IP_BINDANY or IPV6_BINDANY
+ * socket options.
+ */
+ATF_TC(socket_afinet_bindany);
+ATF_TC_HEAD(socket_afinet_bindany, tc)
+{
+ atf_tc_set_md_var(tc, "require.user", "unprivileged");
+}
+ATF_TC_BODY(socket_afinet_bindany, tc)
+{
+ int s;
+
+ s = socket(AF_INET, SOCK_STREAM, 0);
+ ATF_REQUIRE(s >= 0);
+ ATF_REQUIRE_ERRNO(EPERM,
+ setsockopt(s, IPPROTO_IP, IP_BINDANY, &(int){1}, sizeof(int)) ==
+ -1);
+ ATF_REQUIRE(close(s) == 0);
+
+ s = socket(AF_INET, SOCK_DGRAM, 0);
+ ATF_REQUIRE(s >= 0);
+ ATF_REQUIRE_ERRNO(EPERM,
+ setsockopt(s, IPPROTO_IP, IP_BINDANY, &(int){1}, sizeof(int)) ==
+ -1);
+ ATF_REQUIRE(close(s) == 0);
+
+ s = socket(AF_INET6, SOCK_STREAM, 0);
+ ATF_REQUIRE(s >= 0);
+ ATF_REQUIRE_ERRNO(EPERM,
+ setsockopt(s, IPPROTO_IPV6, IPV6_BINDANY, &(int){1}, sizeof(int)) ==
+ -1);
+ ATF_REQUIRE(close(s) == 0);
+
+ s = socket(AF_INET6, SOCK_DGRAM, 0);
+ ATF_REQUIRE(s >= 0);
+ ATF_REQUIRE_ERRNO(EPERM,
+ setsockopt(s, IPPROTO_IPV6, IPV6_BINDANY, &(int){1}, sizeof(int)) ==
+ -1);
+ ATF_REQUIRE(close(s) == 0);
+}
+
+/*
+ * Bind a socket to the specified address, optionally dropping privileges and
+ * setting one of the SO_REUSE* options first.
+ *
+ * Returns true if the bind succeeded, and false if it failed with EADDRINUSE.
+ */
+static bool
+child_bind(const atf_tc_t *tc, int type, struct sockaddr *sa, int opt, bool unpriv)
+{
+ const char *user;
+ pid_t child;
+
+ if (unpriv) {
+ if (!atf_tc_has_config_var(tc, "unprivileged_user"))
+ atf_tc_skip("unprivileged_user not set");
+ user = atf_tc_get_config_var(tc, "unprivileged_user");
+ } else {
+ user = NULL;
+ }
+
+ child = fork();
+ ATF_REQUIRE(child != -1);
+ if (child == 0) {
+ int s;
+
+ if (user != NULL) {
+ struct passwd *passwd;
+
+ passwd = getpwnam(user);
+ if (seteuid(passwd->pw_uid) != 0)
+ _exit(1);
+ }
+
+ s = socket(sa->sa_family, type, 0);
+ if (s < 0)
+ _exit(2);
+ if (bind(s, sa, sa->sa_len) == 0)
+ _exit(3);
+ if (errno != EADDRINUSE)
+ _exit(4);
+ if (opt != 0) {
+ if (setsockopt(s, SOL_SOCKET, opt, &(int){1},
+ sizeof(int)) != 0)
+ _exit(5);
+ }
+ if (bind(s, sa, sa->sa_len) == 0)
+ _exit(6);
+ if (errno != EADDRINUSE)
+ _exit(7);
+ _exit(0);
+ } else {
+ int status;
+
+ ATF_REQUIRE_EQ(waitpid(child, &status, 0), child);
+ ATF_REQUIRE(WIFEXITED(status));
+ status = WEXITSTATUS(status);
+ ATF_REQUIRE_MSG(status == 0 || status == 6,
+ "child exited with %d", status);
+ return (status == 6);
+ }
+}
+
+static bool
+child_bind_priv(const atf_tc_t *tc, int type, struct sockaddr *sa, int opt)
+{
+ return (child_bind(tc, type, sa, opt, false));
+}
+
+static bool
+child_bind_unpriv(const atf_tc_t *tc, int type, struct sockaddr *sa, int opt)
+{
+ return (child_bind(tc, type, sa, opt, true));
+}
+
+static int
+bind_socket(int domain, int type, int opt, bool unspec, struct sockaddr *sa)
+{
+ socklen_t slen;
+ int s;
+
+ s = socket(domain, type, 0);
+ ATF_REQUIRE(s >= 0);
+
+ if (domain == AF_INET) {
+ struct sockaddr_in sin;
+
+ bzero(&sin, sizeof(sin));
+ sin.sin_family = AF_INET;
+ sin.sin_len = sizeof(sin);
+ sin.sin_addr.s_addr = htonl(unspec ?
+ INADDR_ANY : INADDR_LOOPBACK);
+ sin.sin_port = htons(0);
+ ATF_REQUIRE(bind(s, (struct sockaddr *)&sin, sizeof(sin)) == 0);
+
+ slen = sizeof(sin);
+ } else /* if (domain == AF_INET6) */ {
+ struct sockaddr_in6 sin6;
+
+ bzero(&sin6, sizeof(sin6));
+ sin6.sin6_family = AF_INET6;
+ sin6.sin6_len = sizeof(sin6);
+ sin6.sin6_addr = unspec ? in6addr_any : in6addr_loopback;
+ sin6.sin6_port = htons(0);
+ ATF_REQUIRE(bind(s, (struct sockaddr *)&sin6, sizeof(sin6)) == 0);
+
+ slen = sizeof(sin6);
+ }
+
+ if (opt != 0) {
+ ATF_REQUIRE(setsockopt(s, SOL_SOCKET, opt, &(int){1},
+ sizeof(int)) == 0);
+ }
+
+ ATF_REQUIRE(getsockname(s, sa, &slen) == 0);
+
+ return (s);
+}
+
+static void
+multibind_test(const atf_tc_t *tc, int domain, int type)
+{
+ struct sockaddr_storage ss;
+ int opts[4] = { 0, SO_REUSEADDR, SO_REUSEPORT, SO_REUSEPORT_LB };
+ int s;
+ bool flags[2] = { false, true };
+ bool res;
+
+ for (size_t flagi = 0; flagi < nitems(flags); flagi++) {
+ for (size_t opti = 0; opti < nitems(opts); opti++) {
+ s = bind_socket(domain, type, opts[opti], flags[flagi],
+ (struct sockaddr *)&ss);
+ for (size_t optj = 0; optj < nitems(opts); optj++) {
+ int opt;
+
+ opt = opts[optj];
+ res = child_bind_priv(tc, type,
+ (struct sockaddr *)&ss, opt);
+ /*
+ * Multi-binding is only allowed when both
+ * sockets have SO_REUSEPORT or SO_REUSEPORT_LB
+ * set.
+ */
+ if (opts[opti] != 0 &&
+ opts[opti] != SO_REUSEADDR && opti == optj)
+ ATF_REQUIRE(res);
+ else
+ ATF_REQUIRE(!res);
+
+ res = child_bind_unpriv(tc, type,
+ (struct sockaddr *)&ss, opt);
+ /*
+ * Multi-binding is only allowed when both
+ * sockets have the same owner.
+ *
+ * XXX-MJ we for some reason permit this when
+ * binding to the unspecified address, but I
+ * don't think that's right
+ */
+ if (flags[flagi] && opts[opti] != 0 &&
+ opts[opti] != SO_REUSEADDR && opti == optj)
+ ATF_REQUIRE(res);
+ else
+ ATF_REQUIRE(!res);
+ }
+ ATF_REQUIRE(close(s) == 0);
+ }
+ }
+}
+
+/*
+ * Try to bind two sockets to the same address/port tuple. Under some
+ * conditions this is permitted.
+ */
+ATF_TC(socket_afinet_multibind);
+ATF_TC_HEAD(socket_afinet_multibind, tc)
+{
+ atf_tc_set_md_var(tc, "require.user", "root");
+ atf_tc_set_md_var(tc, "require.config", "unprivileged_user");
+}
+ATF_TC_BODY(socket_afinet_multibind, tc)
+{
+ multibind_test(tc, AF_INET, SOCK_STREAM);
+ multibind_test(tc, AF_INET, SOCK_DGRAM);
+ multibind_test(tc, AF_INET6, SOCK_STREAM);
+ multibind_test(tc, AF_INET6, SOCK_DGRAM);
+}
+
ATF_TP_ADD_TCS(tp)
{
ATF_TP_ADD_TC(tp, socket_afinet);
@@ -289,6 +525,8 @@ ATF_TP_ADD_TCS(tp)
ATF_TP_ADD_TC(tp, socket_afinet_poll_no_rdhup);
ATF_TP_ADD_TC(tp, socket_afinet_poll_rdhup);
ATF_TP_ADD_TC(tp, socket_afinet_stream_reconnect);
+ ATF_TP_ADD_TC(tp, socket_afinet_bindany);
+ ATF_TP_ADD_TC(tp, socket_afinet_multibind);
return atf_no_error();
}