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[87.106.108.193]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-482fbac7c01sm18901239f8f.14.2026.08.30.13.17.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 30 Aug 2026 13:17:09 -0700 (PDT) From: =?UTF-8?q?G=C3=BCnther=20Noack?= To: =?UTF-8?q?Micka=C3=ABl=20Sala=C3=BCn?= Cc: Matthieu Baerts , Mat Martineau , Geliang Tang , Mikhail Ivanov , mptcp@lists.linux.dev, netdev@vger.kernel.org, linux-security-module@vger.kernel.org, =?UTF-8?q?G=C3=BCnther=20Noack?= Subject: [PATCH 5/6] samples/landlock: Support MPTCP access rights Date: Sun, 30 Aug 2026 22:16:49 +0200 Message-ID: <20260830201650.67050-6-gnoack3000@gmail.com> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260830201650.67050-1-gnoack3000@gmail.com> References: <20260830201650.67050-1-gnoack3000@gmail.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Add the LL_MPTCP_BIND and LL_MPTCP_CONNECT environment variables to restrict the ports MPTCP sockets may bind and connect to, and the matching "mptcp_bind" and "mptcp_connect" values for LL_QUIET_ACCESS. Because MPTCP sockets use TCP port numbers but are not covered by the TCP access rights, LL_TCP_BIND and LL_TCP_CONNECT alone leave MPTCP unrestricted. Point that out in the help text. Bump LANDLOCK_ABI_LAST to 12 and drop the new access rights when running on an older kernel. Signed-off-by: Günther Noack --- samples/landlock/sandboxer.c | 52 ++++++++++++++++++++++++++++++++++-- 1 file changed, 50 insertions(+), 2 deletions(-) diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c index 1c514efecafb..5eae6fe7467f 100644 --- a/samples/landlock/sandboxer.c +++ b/samples/landlock/sandboxer.c @@ -67,6 +67,8 @@ static inline int landlock_restrict_self(const int ruleset_fd, #define ENV_FORCE_LOG_NAME "LL_FORCE_LOG" #define ENV_UDP_BIND_NAME "LL_UDP_BIND" #define ENV_UDP_CONNECT_SEND_NAME "LL_UDP_CONNECT_SEND" +#define ENV_MPTCP_BIND_NAME "LL_MPTCP_BIND" +#define ENV_MPTCP_CONNECT_NAME "LL_MPTCP_CONNECT" #define ENV_DELIMITER ":" static int str2num(const char *numstr, __u64 *num_dst) @@ -353,6 +355,12 @@ static int add_quiet_access(const char *const env_var, else if (strcmp(str_access, "udp_connect") == 0) ruleset_attr->quiet_access_net |= LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP; + else if (strcmp(str_access, "mptcp_bind") == 0) + ruleset_attr->quiet_access_net |= + LANDLOCK_ACCESS_NET_BIND_MPTCP; + else if (strcmp(str_access, "mptcp_connect") == 0) + ruleset_attr->quiet_access_net |= + LANDLOCK_ACCESS_NET_CONNECT_MPTCP; else if (strcmp(str_access, "abstract_unix_socket") == 0) ruleset_attr->quiet_scoped |= LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET; @@ -373,7 +381,7 @@ static int add_quiet_access(const char *const env_var, return 0; } -#define LANDLOCK_ABI_LAST 11 +#define LANDLOCK_ABI_LAST 12 #define XSTR(s) #s #define STR(s) XSTR(s) @@ -401,6 +409,12 @@ static const char help[] = "* " ENV_UDP_CONNECT_SEND_NAME ": remote UDP ports allowed to connect " "or send to (client: use as destination port / server: receive only from it)\n" "(caution: sending requires being able to bind to a local source port)\n" + "* " ENV_MPTCP_BIND_NAME ": ports allowed to bind with MPTCP sockets " + "(server)\n" + "* " ENV_MPTCP_CONNECT_NAME ": ports allowed to connect to with MPTCP " + "sockets (client)\n" + "(caution: MPTCP sockets use TCP ports but are not covered by " + ENV_TCP_BIND_NAME " nor " ENV_TCP_CONNECT_NAME ")\n" "* " ENV_SCOPED_NAME ": actions denied on the outside of the landlock domain\n" " - \"a\" to restrict opening abstract unix sockets\n" " - \"s\" to restrict sending signals\n" @@ -418,6 +432,8 @@ static const char help[] = " - \"tcp_connect\" to quiet tcp connect denials\n" " - \"udp_bind\" to quiet udp bind denials\n" " - \"udp_connect\" to quiet udp connect / send denials\n" + " - \"mptcp_bind\" to quiet mptcp bind denials\n" + " - \"mptcp_connect\" to quiet mptcp connect denials\n" " - \"abstract_unix_socket\" to quiet abstract unix socket denials\n" " - \"signal\" to quiet signal denials\n" "\n" @@ -449,7 +465,9 @@ int main(const int argc, char *const argv[], char *const *const envp) .handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP | LANDLOCK_ACCESS_NET_CONNECT_TCP | LANDLOCK_ACCESS_NET_BIND_UDP | - LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP, + LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP | + LANDLOCK_ACCESS_NET_BIND_MPTCP | + LANDLOCK_ACCESS_NET_CONNECT_MPTCP, .scoped = LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET | LANDLOCK_SCOPE_SIGNAL, .quiet_access_fs = 0, @@ -556,6 +574,12 @@ int main(const int argc, char *const argv[], char *const *const envp) supported_restrict_flags &= ~LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS; set_restrict_flags &= ~LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS; + __attribute__((fallthrough)); + case 11: + /* Removes MPTCP support for ABI < 12 */ + ruleset_attr.handled_access_net &= + ~(LANDLOCK_ACCESS_NET_BIND_MPTCP | + LANDLOCK_ACCESS_NET_CONNECT_MPTCP); /* Must be printed for any ABI < LANDLOCK_ABI_LAST. */ fprintf(stderr, @@ -600,6 +624,18 @@ int main(const int argc, char *const argv[], char *const *const envp) ruleset_attr.handled_access_net &= ~LANDLOCK_ACCESS_NET_CONNECT_SEND_UDP; } + /* Removes MPTCP bind access control if not supported by a user. */ + env_port_name = getenv(ENV_MPTCP_BIND_NAME); + if (!env_port_name) { + ruleset_attr.handled_access_net &= + ~LANDLOCK_ACCESS_NET_BIND_MPTCP; + } + /* Removes MPTCP connect access control if not supported by a user. */ + env_port_name = getenv(ENV_MPTCP_CONNECT_NAME); + if (!env_port_name) { + ruleset_attr.handled_access_net &= + ~LANDLOCK_ACCESS_NET_CONNECT_MPTCP; + } if (check_ruleset_scope(ENV_SCOPED_NAME, &ruleset_attr)) return 1; @@ -684,6 +720,18 @@ int main(const int argc, char *const argv[], char *const *const envp) 0)) { goto err_close_ruleset; } + if (populate_ruleset_net(ENV_MPTCP_BIND_NAME, ruleset_fd, + ruleset_attr.handled_access_net & + LANDLOCK_ACCESS_NET_BIND_MPTCP, + 0)) { + goto err_close_ruleset; + } + if (populate_ruleset_net(ENV_MPTCP_CONNECT_NAME, ruleset_fd, + ruleset_attr.handled_access_net & + LANDLOCK_ACCESS_NET_CONNECT_MPTCP, + 0)) { + goto err_close_ruleset; + } if (quiet_supported) { if (populate_ruleset_net(ENV_NET_QUIET_NAME, ruleset_fd, 0, -- 2.55.0