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Message-ID: <20230817.Jeeb9buaf9oa@digikod.net>
Date: Thu, 17 Aug 2023 17:36:53 +0200
From: Mickaël Salaün <mic@...ikod.net>
To: "Konstantin Meskhidze (A)" <konstantin.meskhidze@...wei.com>
Cc: artem.kuzin@...wei.com, gnoack3000@...il.com,
willemdebruijn.kernel@...il.com, yusongping@...wei.com, linux-security-module@...r.kernel.org,
netdev@...r.kernel.org, netfilter-devel@...r.kernel.org
Subject: Re: [PATCH] landlock: Fix and test network AF inconsistencies
On Thu, Aug 17, 2023 at 05:13:28PM +0300, Konstantin Meskhidze (A) wrote:
>
>
> 8/17/2023 4:00 PM, Mickaël Salaün пишет:
> > Check af_family consistency while handling AF_UNSPEC specifically.
> >
> > This patch should be squashed into the "Network support for Landlock"
> > v11 patch series.
>
> Thank you so much.
> Can I find this patch in
> https://git.kernel.org/pub/scm/linux/kernel/git/mic/linux ???
It is now in the landlock-net-v11 branch.
> >
> > Signed-off-by: Mickaël Salaün <mic@...ikod.net>
> > ---
> > security/landlock/net.c | 29 ++++-
> > tools/testing/selftests/landlock/net_test.c | 124 +++++++++++++-------
> > 2 files changed, 108 insertions(+), 45 deletions(-)
> >
> > diff --git a/security/landlock/net.c b/security/landlock/net.c
> > index f8d2be53ac0d..ea5373f774f9 100644
> > --- a/security/landlock/net.c
> > +++ b/security/landlock/net.c
> > @@ -80,11 +80,11 @@ static int check_socket_access(struct socket *const sock,
> > if (WARN_ON_ONCE(domain->num_layers < 1))
> > return -EACCES;
> > - /* Checks if it's a TCP socket. */
> > + /* Checks if it's a (potential) TCP socket. */
> > if (sock->type != SOCK_STREAM)
> > return 0;
> > - /* Checks for minimal header length. */
> > + /* Checks for minimal header length to safely read sa_family. */
> > if (addrlen < offsetofend(struct sockaddr, sa_family))
> > return -EINVAL;
> > @@ -106,7 +106,6 @@ static int check_socket_access(struct socket *const sock,
> > return 0;
> > }
> > - /* Specific AF_UNSPEC handling. */
> > if (address->sa_family == AF_UNSPEC) {
> > /*
> > * Connecting to an address with AF_UNSPEC dissolves the TCP
> > @@ -114,6 +113,10 @@ static int check_socket_access(struct socket *const sock,
> > * connection while retaining the socket object (i.e., the file
> > * descriptor). As for dropping privileges, closing
> > * connections is always allowed.
> > + *
> > + * For a TCP access control system, this request is legitimate.
> > + * Let the network stack handle potential inconsistencies and
> > + * return -EINVAL if needed.
> > */
> > if (access_request == LANDLOCK_ACCESS_NET_CONNECT_TCP)
> > return 0;
> > @@ -124,14 +127,34 @@ static int check_socket_access(struct socket *const sock,
> > * INADDR_ANY (cf. __inet_bind). Checking the address is
> > * required to not wrongfully return -EACCES instead of
> > * -EAFNOSUPPORT.
> > + *
> > + * We could return 0 and let the network stack handle these
> > + * checks, but it is safer to return a proper error and test
> > + * consistency thanks to kselftest.
> > */
> > if (access_request == LANDLOCK_ACCESS_NET_BIND_TCP) {
> > + /* addrlen has already been checked for AF_UNSPEC. */
> > const struct sockaddr_in *const sockaddr =
> > (struct sockaddr_in *)address;
> > + if (sock->sk->__sk_common.skc_family != AF_INET)
> > + return -EINVAL;
> > +
> > if (sockaddr->sin_addr.s_addr != htonl(INADDR_ANY))
> > return -EAFNOSUPPORT;
> > }
> > + } else {
> > + /*
> > + * Checks sa_family consistency to not wrongfully return
> > + * -EACCES instead of -EINVAL. Valid sa_family changes are
> > + * only (from AF_INET or AF_INET6) to AF_UNSPEC.
> > + *
> > + * We could return 0 and let the network stack handle this
> > + * check, but it is safer to return a proper error and test
> > + * consistency thanks to kselftest.
> > + */
> > + if (address->sa_family != sock->sk->__sk_common.skc_family)
> > + return -EINVAL;
> > }
> > id.key.data = (__force uintptr_t)port;
> > diff --git a/tools/testing/selftests/landlock/net_test.c b/tools/testing/selftests/landlock/net_test.c
> > index 12dc127ea7d1..504a26c63fd9 100644
> > --- a/tools/testing/selftests/landlock/net_test.c
> > +++ b/tools/testing/selftests/landlock/net_test.c
> > @@ -233,7 +233,7 @@ static int connect_variant(const int sock_fd,
> > FIXTURE(protocol)
> > {
> > - struct service_fixture srv0, srv1, srv2, unspec_any, unspec_srv0;
> > + struct service_fixture srv0, srv1, srv2, unspec_any0, unspec_srv0;
> > };
> > FIXTURE_VARIANT(protocol)
> > @@ -257,8 +257,8 @@ FIXTURE_SETUP(protocol)
> > ASSERT_EQ(0, set_service(&self->unspec_srv0, prot_unspec, 0));
> > - ASSERT_EQ(0, set_service(&self->unspec_any, prot_unspec, 0));
> > - self->unspec_any.ipv4_addr.sin_addr.s_addr = htonl(INADDR_ANY);
> > + ASSERT_EQ(0, set_service(&self->unspec_any0, prot_unspec, 0));
> > + self->unspec_any0.ipv4_addr.sin_addr.s_addr = htonl(INADDR_ANY);
> > setup_loopback(_metadata);
> > };
> > @@ -615,20 +615,18 @@ TEST_F(protocol, connect)
> > // Kernel FIXME: tcp_sandbox_with_ipv6_tcp and tcp_sandbox_with_unix_stream
> > TEST_F(protocol, bind_unspec)
> > {
> > + const struct landlock_ruleset_attr ruleset_attr = {
> > + .handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP,
> > + };
> > + const struct landlock_net_service_attr tcp_bind = {
> > + .allowed_access = LANDLOCK_ACCESS_NET_BIND_TCP,
> > + .port = self->srv0.port,
> > + };
> > int bind_fd, ret;
> > if (variant->sandbox == TCP_SANDBOX) {
> > - const struct landlock_ruleset_attr ruleset_attr = {
> > - .handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP,
> > - };
> > - const struct landlock_net_service_attr tcp_bind = {
> > - .allowed_access = LANDLOCK_ACCESS_NET_BIND_TCP,
> > - .port = self->srv0.port,
> > - };
> > - int ruleset_fd;
> > -
> > - ruleset_fd = landlock_create_ruleset(&ruleset_attr,
> > - sizeof(ruleset_attr), 0);
> > + const int ruleset_fd = landlock_create_ruleset(
> > + &ruleset_attr, sizeof(ruleset_attr), 0);
> > ASSERT_LE(0, ruleset_fd);
> > /* Allows bind. */
> > @@ -642,8 +640,8 @@ TEST_F(protocol, bind_unspec)
> > bind_fd = socket_variant(&self->srv0);
> > ASSERT_LE(0, bind_fd);
> > - /* Binds on AF_UNSPEC/INADDR_ANY. */
> > - ret = bind_variant(bind_fd, &self->unspec_any);
> > + /* Allowed bind on AF_UNSPEC/INADDR_ANY. */
> > + ret = bind_variant(bind_fd, &self->unspec_any0);
> > if (variant->prot.domain == AF_INET) {
> > EXPECT_EQ(0, ret)
> > {
> > @@ -655,6 +653,33 @@ TEST_F(protocol, bind_unspec)
> > }
> > EXPECT_EQ(0, close(bind_fd));
> > + if (variant->sandbox == TCP_SANDBOX) {
> > + const int ruleset_fd = landlock_create_ruleset(
> > + &ruleset_attr, sizeof(ruleset_attr), 0);
> > + ASSERT_LE(0, ruleset_fd);
> > +
> > + /* Denies bind. */
> > + enforce_ruleset(_metadata, ruleset_fd);
> > + EXPECT_EQ(0, close(ruleset_fd));
> > + }
> > +
> > + bind_fd = socket_variant(&self->srv0);
> > + ASSERT_LE(0, bind_fd);
> > +
> > + /* Denied bind on AF_UNSPEC/INADDR_ANY. */
> > + ret = bind_variant(bind_fd, &self->unspec_any0);
> > + if (variant->prot.domain == AF_INET) {
> > + if (is_restricted(&variant->prot, variant->sandbox)) {
> > + EXPECT_EQ(-EACCES, ret);
> > + } else {
> > + EXPECT_EQ(0, ret);
> > + }
> > + } else {
> > + EXPECT_EQ(-EINVAL, ret);
> > + }
> > + EXPECT_EQ(0, close(bind_fd));
> > +
> > + /* Checks bind with AF_UNSPEC and the loopback address. */
> > bind_fd = socket_variant(&self->srv0);
> > ASSERT_LE(0, bind_fd);
> > ret = bind_variant(bind_fd, &self->unspec_srv0);
> > @@ -671,34 +696,16 @@ TEST_F(protocol, bind_unspec)
> > TEST_F(protocol, connect_unspec)
> > {
> > + const struct landlock_ruleset_attr ruleset_attr = {
> > + .handled_access_net = LANDLOCK_ACCESS_NET_CONNECT_TCP,
> > + };
> > + const struct landlock_net_service_attr tcp_connect = {
> > + .allowed_access = LANDLOCK_ACCESS_NET_CONNECT_TCP,
> > + .port = self->srv0.port,
> > + };
> > int bind_fd, client_fd, status;
> > pid_t child;
> > - if (variant->sandbox == TCP_SANDBOX) {
> > - const struct landlock_ruleset_attr ruleset_attr = {
> > - .handled_access_net = LANDLOCK_ACCESS_NET_CONNECT_TCP,
> > - };
> > - const struct landlock_net_service_attr tcp_connect = {
> > - .allowed_access = LANDLOCK_ACCESS_NET_CONNECT_TCP,
> > - .port = self->srv0.port,
> > - };
> > - int ruleset_fd;
> > -
> > - ruleset_fd = landlock_create_ruleset(&ruleset_attr,
> > - sizeof(ruleset_attr), 0);
> > - ASSERT_LE(0, ruleset_fd);
> > -
> > - /* Allows connect. */
> > - ASSERT_EQ(0, landlock_add_rule(ruleset_fd,
> > - LANDLOCK_RULE_NET_SERVICE,
> > - &tcp_connect, 0));
> > - enforce_ruleset(_metadata, ruleset_fd);
> > - EXPECT_EQ(0, close(ruleset_fd));
> > - }
> > -
> > - /* Generic connection tests. */
> > - test_bind_and_connect(_metadata, &self->srv0, false, false);
> > -
> > /* Specific connection tests. */
> > bind_fd = socket_variant(&self->srv0);
> > ASSERT_LE(0, bind_fd);
> > @@ -726,8 +733,22 @@ TEST_F(protocol, connect_unspec)
> > EXPECT_EQ(0, ret);
> > }
> > + if (variant->sandbox == TCP_SANDBOX) {
> > + const int ruleset_fd = landlock_create_ruleset(
> > + &ruleset_attr, sizeof(ruleset_attr), 0);
> > + ASSERT_LE(0, ruleset_fd);
> > +
> > + /* Allows connect. */
> > + ASSERT_EQ(0,
> > + landlock_add_rule(ruleset_fd,
> > + LANDLOCK_RULE_NET_SERVICE,
> > + &tcp_connect, 0));
> > + enforce_ruleset(_metadata, ruleset_fd);
> > + EXPECT_EQ(0, close(ruleset_fd));
> > + }
> > +
> > /* Disconnects already connected socket, or set peer. */
> > - ret = connect_variant(connect_fd, &self->unspec_any);
> > + ret = connect_variant(connect_fd, &self->unspec_any0);
> > if (self->srv0.protocol.domain == AF_UNIX &&
> > self->srv0.protocol.type == SOCK_STREAM) {
> > EXPECT_EQ(-EINVAL, ret);
> > @@ -744,6 +765,25 @@ TEST_F(protocol, connect_unspec)
> > EXPECT_EQ(0, ret);
> > }
> > + if (variant->sandbox == TCP_SANDBOX) {
> > + const int ruleset_fd = landlock_create_ruleset(
> > + &ruleset_attr, sizeof(ruleset_attr), 0);
> > + ASSERT_LE(0, ruleset_fd);
> > +
> > + /* Denies connect. */
> > + enforce_ruleset(_metadata, ruleset_fd);
> > + EXPECT_EQ(0, close(ruleset_fd));
> > + }
> > +
> > + ret = connect_variant(connect_fd, &self->unspec_any0);
> > + if (self->srv0.protocol.domain == AF_UNIX &&
> > + self->srv0.protocol.type == SOCK_STREAM) {
> > + EXPECT_EQ(-EINVAL, ret);
> > + } else {
> > + /* Always allowed to disconnect. */
> > + EXPECT_EQ(0, ret);
> > + }
> > +
> > EXPECT_EQ(0, close(connect_fd));
> > _exit(_metadata->passed ? EXIT_SUCCESS : EXIT_FAILURE);
> > return;
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