Add environment variables to control associated access rights:
(each one takes a list of ports separated by colons, like other
list options)

- LL_UDP_BIND
- LL_UDP_CONNECT
- LL_UDP_SENDTO

Signed-off-by: Matthieu Buffet <redacted>
---
  samples/landlock/sandboxer.c | 58 ++++++++++++++++++++++++++++++++++--
  1 file changed, 56 insertions(+), 2 deletions(-)

diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
index 57565dfd74a2..61dc2645371e 100644
--- a/samples/landlock/sandboxer.c
+++ b/samples/landlock/sandboxer.c

@@ -58,6 +58,9 @@ static inline int landlock_restrict_self(const int ruleset_fd,
  #define ENV_TCP_BIND_NAME "LL_TCP_BIND"
  #define ENV_TCP_CONNECT_NAME "LL_TCP_CONNECT"
  #define ENV_SCOPED_NAME "LL_SCOPED"
+#define ENV_UDP_BIND_NAME "LL_UDP_BIND"
+#define ENV_UDP_CONNECT_NAME "LL_UDP_CONNECT"
+#define ENV_UDP_SENDTO_NAME "LL_UDP_SENDTO"
  #define ENV_DELIMITER ":"
  
  static int str2num(const char *numstr, __u64 *num_dst)

@@ -288,7 +291,7 @@ static bool check_ruleset_scope(const char *const env_var,
  
  /* clang-format on */
  
-#define LANDLOCK_ABI_LAST 6
+#define LANDLOCK_ABI_LAST 7
  
  #define XSTR(s) #s
  #define STR(s) XSTR(s)

@@ -311,6 +314,11 @@ static const char help[] =
  	"means an empty list):\n"
  	"* " ENV_TCP_BIND_NAME ": ports allowed to bind (server)\n"
  	"* " ENV_TCP_CONNECT_NAME ": ports allowed to connect (client)\n"
+	"* " ENV_UDP_BIND_NAME ": UDP ports allowed to bind (client: set as "
+	"source port / server: prepare to listen on port)\n"

+	"* " ENV_UDP_CONNECT_NAME ": UDP ports allowed to connect (client: "
+	"set as destination port / server: only receive from one client)\n"
+	"* " ENV_UDP_SENDTO_NAME ": UDP ports allowed to send to (client/server)\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"

@@ -320,6 +328,8 @@ static const char help[] =
  	ENV_FS_RW_NAME "=\"/dev/null:/dev/full:/dev/zero:/dev/pts:/tmp\" "
  	ENV_TCP_BIND_NAME "=\"9418\" "
  	ENV_TCP_CONNECT_NAME "=\"80:443\" "
+	ENV_UDP_CONNECT_NAME "=\"53\" "
+	ENV_UDP_SENDTO_NAME "=\"53\" "
  	ENV_SCOPED_NAME "=\"a:s\" "
  	"%1$s bash -i\n"
  	"\n"

@@ -340,7 +350,10 @@ int main(const int argc, char *const argv[], char *const *const envp)
  	struct landlock_ruleset_attr ruleset_attr = {
  		.handled_access_fs = access_fs_rw,
  		.handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP |
-				      LANDLOCK_ACCESS_NET_CONNECT_TCP,
+				      LANDLOCK_ACCESS_NET_CONNECT_TCP |
+				      LANDLOCK_ACCESS_NET_BIND_UDP |
+				      LANDLOCK_ACCESS_NET_CONNECT_UDP |
+				      LANDLOCK_ACCESS_NET_SENDTO_UDP,
  		.scoped = LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET |
  			  LANDLOCK_SCOPE_SIGNAL,
  	};

@@ -415,6 +428,14 @@ int main(const int argc, char *const argv[], char *const *const envp)
  		/* Removes LANDLOCK_SCOPE_* for ABI < 6 */
  		ruleset_attr.scoped &= ~(LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET |
  					 LANDLOCK_SCOPE_SIGNAL);
+
+		__attribute__((fallthrough));
+	case 6:
+		/* Removes UDP support for ABI < 7 */
+		ruleset_attr.handled_access_fs &=

+			~(LANDLOCK_ACCESS_NET_BIND_UDP |
+			  LANDLOCK_ACCESS_NET_CONNECT_UDP |
+			  LANDLOCK_ACCESS_NET_SENDTO_UDP);
  		fprintf(stderr,
  			"Hint: You should update the running kernel "
  			"to leverage Landlock features "

@@ -445,6 +466,27 @@ int main(const int argc, char *const argv[], char *const *const envp)
  		ruleset_attr.handled_access_net &=
  			~LANDLOCK_ACCESS_NET_CONNECT_TCP;
  	}
+	/* Removes UDP bind access control if not supported by a user */

+	env_port_name = getenv(ENV_UDP_BIND_NAME);
+	if (!env_port_name) {
+		ruleset_attr.handled_access_net &=
+			~LANDLOCK_ACCESS_NET_BIND_UDP;
+	}
+	/* Removes UDP connect access control if not supported by a user */
+	env_port_name = getenv(ENV_UDP_CONNECT_NAME);
+	if (!env_port_name) {
+		ruleset_attr.handled_access_net &=
+			~LANDLOCK_ACCESS_NET_CONNECT_UDP;
+	}
+	/*
+	 * Removes UDP sendmsg(addr != NULL) access control if not
+	 * supported by a user
+	 */
+	env_port_name = getenv(ENV_UDP_SENDTO_NAME);
+	if (!env_port_name) {
+		ruleset_attr.handled_access_net &=
+			~LANDLOCK_ACCESS_NET_SENDTO_UDP;
+	}
  
  	if (check_ruleset_scope(ENV_SCOPED_NAME, &ruleset_attr))
  		return 1;

@@ -471,6 +513,18 @@ int main(const int argc, char *const argv[], char *const *const envp)
  				 LANDLOCK_ACCESS_NET_CONNECT_TCP)) {
  		goto err_close_ruleset;
  	}
+	if (populate_ruleset_net(ENV_UDP_BIND_NAME, ruleset_fd,
+				 LANDLOCK_ACCESS_NET_BIND_UDP)) {
+		goto err_close_ruleset;
+	}
+	if (populate_ruleset_net(ENV_UDP_CONNECT_NAME, ruleset_fd,
+				 LANDLOCK_ACCESS_NET_CONNECT_UDP)) {
+		goto err_close_ruleset;
+	}
+	if (populate_ruleset_net(ENV_UDP_SENDTO_NAME, ruleset_fd,
+				 LANDLOCK_ACCESS_NET_SENDTO_UDP)) {
+		goto err_close_ruleset;
+	}
  
  	if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {
  		perror("Failed to restrict privileges");