1 files changed, 69 insertions, 43 deletions

diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c
index f847e832ba14..57565dfd74a2 100644
--- a/samples/landlock/sandboxer.c
+++ b/samples/landlock/sandboxer.c
@@ -60,6 +60,25 @@ static inline int landlock_restrict_self(const int ruleset_fd,
 #define ENV_SCOPED_NAME "LL_SCOPED"
 #define ENV_DELIMITER ":"
 
+static int str2num(const char *numstr, __u64 *num_dst)
+{
+	char *endptr = NULL;
+	int err = 0;
+	__u64 num;
+
+	errno = 0;
+	num = strtoull(numstr, &endptr, 10);
+	if (errno != 0)
+		err = errno;
+	/* Was the string empty, or not entirely parsed successfully? */
+	else if ((*numstr == '\0') || (*endptr != '\0'))
+		err = EINVAL;
+	else
+		*num_dst = num;
+
+	return err;
+}
+
 static int parse_path(char *env_path, const char ***const path_list)
 {
 	int i, num_paths = 0;
@@ -160,7 +179,6 @@ static int populate_ruleset_net(const char *const env_var, const int ruleset_fd,
 	char *env_port_name, *env_port_name_next, *strport;
 	struct landlock_net_port_attr net_port = {
 		.allowed_access = allowed_access,
-		.port = 0,
 	};
 
 	env_port_name = getenv(env_var);
@@ -171,7 +189,17 @@ static int populate_ruleset_net(const char *const env_var, const int ruleset_fd,
 
 	env_port_name_next = env_port_name;
 	while ((strport = strsep(&env_port_name_next, ENV_DELIMITER))) {
-		net_port.port = atoi(strport);
+		__u64 port;
+
+		if (strcmp(strport, "") == 0)
+			continue;
+
+		if (str2num(strport, &port)) {
+			fprintf(stderr, "Failed to parse port at \"%s\"\n",
+				strport);
+			goto out_free_name;
+		}
+		net_port.port = port;
 		if (landlock_add_rule(ruleset_fd, LANDLOCK_RULE_NET_PORT,
 				      &net_port, 0)) {
 			fprintf(stderr,
@@ -262,6 +290,44 @@ out_unset:
 
 #define LANDLOCK_ABI_LAST 6
 
+#define XSTR(s) #s
+#define STR(s) XSTR(s)
+
+/* clang-format off */
+
+static const char help[] =
+	"usage: " ENV_FS_RO_NAME "=\"...\" " ENV_FS_RW_NAME "=\"...\" "
+	"[other environment variables] %1$s <cmd> [args]...\n"
+	"\n"
+	"Execute the given command in a restricted environment.\n"
+	"Multi-valued settings (lists of ports, paths, scopes) are colon-delimited.\n"
+	"\n"
+	"Mandatory settings:\n"
+	"* " ENV_FS_RO_NAME ": paths allowed to be used in a read-only way\n"
+	"* " ENV_FS_RW_NAME ": paths allowed to be used in a read-write way\n"
+	"\n"
+	"Optional settings (when not set, their associated access check "
+	"is always allowed, which is different from an empty string which "
+	"means an empty list):\n"
+	"* " ENV_TCP_BIND_NAME ": ports allowed to bind (server)\n"
+	"* " ENV_TCP_CONNECT_NAME ": ports allowed to connect (client)\n"
+	"* " ENV_SCOPED_NAME ": actions denied on the outside of the landlock domain\n"
+	"  - \"a\" to restrict opening abstract unix sockets\n"
+	"  - \"s\" to restrict sending signals\n"
+	"\n"
+	"Example:\n"
+	ENV_FS_RO_NAME "=\"${PATH}:/lib:/usr:/proc:/etc:/dev/urandom\" "
+	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_SCOPED_NAME "=\"a:s\" "
+	"%1$s bash -i\n"
+	"\n"
+	"This sandboxer can use Landlock features up to ABI version "
+	STR(LANDLOCK_ABI_LAST) ".\n";
+
+/* clang-format on */
+
 int main(const int argc, char *const argv[], char *const *const envp)
 {
 	const char *cmd_path;
@@ -280,47 +346,7 @@ int main(const int argc, char *const argv[], char *const *const envp)
 	};
 
 	if (argc < 2) {
-		fprintf(stderr,
-			"usage: %s=\"...\" %s=\"...\" %s=\"...\" %s=\"...\" %s=\"...\" %s "
-			"<cmd> [args]...\n\n",
-			ENV_FS_RO_NAME, ENV_FS_RW_NAME, ENV_TCP_BIND_NAME,
-			ENV_TCP_CONNECT_NAME, ENV_SCOPED_NAME, argv[0]);
-		fprintf(stderr,
-			"Execute a command in a restricted environment.\n\n");
-		fprintf(stderr,
-			"Environment variables containing paths and ports "
-			"each separated by a colon:\n");
-		fprintf(stderr,
-			"* %s: list of paths allowed to be used in a read-only way.\n",
-			ENV_FS_RO_NAME);
-		fprintf(stderr,
-			"* %s: list of paths allowed to be used in a read-write way.\n\n",
-			ENV_FS_RW_NAME);
-		fprintf(stderr,
-			"Environment variables containing ports are optional "
-			"and could be skipped.\n");
-		fprintf(stderr,
-			"* %s: list of ports allowed to bind (server).\n",
-			ENV_TCP_BIND_NAME);
-		fprintf(stderr,
-			"* %s: list of ports allowed to connect (client).\n",
-			ENV_TCP_CONNECT_NAME);
-		fprintf(stderr, "* %s: list of scoped IPCs.\n",
-			ENV_SCOPED_NAME);
-		fprintf(stderr,
-			"\nexample:\n"
-			"%s=\"${PATH}:/lib:/usr:/proc:/etc:/dev/urandom\" "
-			"%s=\"/dev/null:/dev/full:/dev/zero:/dev/pts:/tmp\" "
-			"%s=\"9418\" "
-			"%s=\"80:443\" "
-			"%s=\"a:s\" "
-			"%s bash -i\n\n",
-			ENV_FS_RO_NAME, ENV_FS_RW_NAME, ENV_TCP_BIND_NAME,
-			ENV_TCP_CONNECT_NAME, ENV_SCOPED_NAME, argv[0]);
-		fprintf(stderr,
-			"This sandboxer can use Landlock features "
-			"up to ABI version %d.\n",
-			LANDLOCK_ABI_LAST);
+		fprintf(stderr, help, argv[0]);
 		return 1;
 	}