Unverified Commit 5e990dce authored by Konstantin Meskhidze's avatar Konstantin Meskhidze Committed by Mickaël Salaün
Browse files

samples/landlock: Support TCP restrictions 



Add TCP restrictions to the sandboxer demo. It's possible to allow a
sandboxer to bind/connect to a list of specified ports restricting
network actions to the rest of them. This is controlled with the new
LL_TCP_BIND and LL_TCP_CONNECT environment variables.

Rename ENV_PATH_TOKEN to ENV_DELIMITER.

Signed-off-by: default avatarKonstantin Meskhidze <konstantin.meskhidze@huawei.com>
Link: https://lore.kernel.org/r/20231026014751.414649-12-konstantin.meskhidze@huawei.com


[mic: Extend commit message]
Signed-off-by: default avatarMickaël Salaün <mic@digikod.net>
parent a549d055

samples/landlock/sandboxer.c

+100 −15
Original line number Diff line number Diff line
@@ -8,6 +8,8 @@ 
 */



#define _GNU_SOURCE

#define __SANE_USERSPACE_TYPES__

#include <arpa/inet.h>

#include <errno.h>

#include <fcntl.h>

#include <linux/landlock.h>
@@ -51,7 +53,9 @@ static inline int landlock_restrict_self(const int ruleset_fd, 


#define ENV_FS_RO_NAME "LL_FS_RO"

#define ENV_FS_RW_NAME "LL_FS_RW"

#define ENV_PATH_TOKEN ":"

#define ENV_TCP_BIND_NAME "LL_TCP_BIND"

#define ENV_TCP_CONNECT_NAME "LL_TCP_CONNECT"

#define ENV_DELIMITER ":"



static int parse_path(char *env_path, const char ***const path_list)

{
@@ -60,13 +64,13 @@ static int parse_path(char *env_path, const char ***const path_list) 
	if (env_path) {

		num_paths++;

		for (i = 0; env_path[i]; i++) {

			if (env_path[i] == ENV_PATH_TOKEN[0])

			if (env_path[i] == ENV_DELIMITER[0])

				num_paths++;

		}

	}

	*path_list = malloc(num_paths * sizeof(**path_list));

	for (i = 0; i < num_paths; i++)

		(*path_list)[i] = strsep(&env_path, ENV_PATH_TOKEN);

		(*path_list)[i] = strsep(&env_path, ENV_DELIMITER);



	return num_paths;

}
@@ -81,7 +85,7 @@ static int parse_path(char *env_path, const char ***const path_list) 


/* clang-format on */



static int populate_ruleset(const char *const env_var, const int ruleset_fd,

static int populate_ruleset_fs(const char *const env_var, const int ruleset_fd,

			       const __u64 allowed_access)

{

	int num_paths, i, ret = 1;
@@ -143,6 +147,39 @@ static int populate_ruleset(const char *const env_var, const int ruleset_fd, 
	return ret;

}



static int populate_ruleset_net(const char *const env_var, const int ruleset_fd,

				const __u64 allowed_access)

{

	int ret = 1;

	char *env_port_name, *strport;

	struct landlock_net_port_attr net_port = {

		.allowed_access = allowed_access,

		.port = 0,

	};



	env_port_name = getenv(env_var);

	if (!env_port_name)

		return 0;

	env_port_name = strdup(env_port_name);

	unsetenv(env_var);



	while ((strport = strsep(&env_port_name, ENV_DELIMITER))) {

		net_port.port = atoi(strport);

		if (landlock_add_rule(ruleset_fd, LANDLOCK_RULE_NET_PORT,

				      &net_port, 0)) {

			fprintf(stderr,

				"Failed to update the ruleset with port \"%llu\": %s\n",

				net_port.port, strerror(errno));

			goto out_free_name;

		}

	}

	ret = 0;



out_free_name:

	free(env_port_name);

	return ret;

}



/* clang-format off */



#define ACCESS_FS_ROUGHLY_READ ( \
@@ -166,39 +203,58 @@ static int populate_ruleset(const char *const env_var, const int ruleset_fd, 


/* clang-format on */



#define LANDLOCK_ABI_LAST 3

#define LANDLOCK_ABI_LAST 4



int main(const int argc, char *const argv[], char *const *const envp)

{

	const char *cmd_path;

	char *const *cmd_argv;

	int ruleset_fd, abi;

	char *env_port_name;

	__u64 access_fs_ro = ACCESS_FS_ROUGHLY_READ,

	      access_fs_rw = ACCESS_FS_ROUGHLY_READ | ACCESS_FS_ROUGHLY_WRITE;



	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,

	};



	if (argc < 2) {

		fprintf(stderr,

			"usage: %s=\"...\" %s=\"...\" %s <cmd> [args]...\n\n",

			ENV_FS_RO_NAME, ENV_FS_RW_NAME, argv[0]);

			"usage: %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, argv[0]);

		fprintf(stderr,

			"Launch a command in a restricted environment.\n\n");

		fprintf(stderr, "Environment variables containing paths, "

		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",

			"* %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,

			"\nexample:\n"

			"%s=\"/bin:/lib:/usr:/proc:/etc:/dev/urandom\" "

			"%s=\"/dev/null:/dev/full:/dev/zero:/dev/pts:/tmp\" "

			"%s=\"9418\" "

			"%s=\"80:443\" "

			"%s bash -i\n\n",

			ENV_FS_RO_NAME, ENV_FS_RW_NAME, argv[0]);

			ENV_FS_RO_NAME, ENV_FS_RW_NAME, ENV_TCP_BIND_NAME,

			ENV_TCP_CONNECT_NAME, argv[0]);

		fprintf(stderr,

			"This sandboxer can use Landlock features "

			"up to ABI version %d.\n",
@@ -255,7 +311,12 @@ int main(const int argc, char *const argv[], char *const *const envp) 
	case 2:

		/* Removes LANDLOCK_ACCESS_FS_TRUNCATE for ABI < 3 */

		ruleset_attr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_TRUNCATE;



		__attribute__((fallthrough));

	case 3:

		/* Removes network support for ABI < 4 */

		ruleset_attr.handled_access_net &=

			~(LANDLOCK_ACCESS_NET_BIND_TCP |

			  LANDLOCK_ACCESS_NET_CONNECT_TCP);

		fprintf(stderr,

			"Hint: You should update the running kernel "

			"to leverage Landlock features "
@@ -274,18 +335,42 @@ int main(const int argc, char *const argv[], char *const *const envp) 
	access_fs_ro &= ruleset_attr.handled_access_fs;

	access_fs_rw &= ruleset_attr.handled_access_fs;



	/* Removes bind access attribute if not supported by a user. */

	env_port_name = getenv(ENV_TCP_BIND_NAME);

	if (!env_port_name) {

		ruleset_attr.handled_access_net &=

			~LANDLOCK_ACCESS_NET_BIND_TCP;

	}

	/* Removes connect access attribute if not supported by a user. */

	env_port_name = getenv(ENV_TCP_CONNECT_NAME);

	if (!env_port_name) {

		ruleset_attr.handled_access_net &=

			~LANDLOCK_ACCESS_NET_CONNECT_TCP;

	}



	ruleset_fd =

		landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);

	if (ruleset_fd < 0) {

		perror("Failed to create a ruleset");

		return 1;

	}

	if (populate_ruleset(ENV_FS_RO_NAME, ruleset_fd, access_fs_ro)) {



	if (populate_ruleset_fs(ENV_FS_RO_NAME, ruleset_fd, access_fs_ro)) {

		goto err_close_ruleset;

	}

	if (populate_ruleset_fs(ENV_FS_RW_NAME, ruleset_fd, access_fs_rw)) {

		goto err_close_ruleset;

	}

	if (populate_ruleset(ENV_FS_RW_NAME, ruleset_fd, access_fs_rw)) {



	if (populate_ruleset_net(ENV_TCP_BIND_NAME, ruleset_fd,

				 LANDLOCK_ACCESS_NET_BIND_TCP)) {

		goto err_close_ruleset;

	}

	if (populate_ruleset_net(ENV_TCP_CONNECT_NAME, ruleset_fd,

				 LANDLOCK_ACCESS_NET_CONNECT_TCP)) {

		goto err_close_ruleset;

	}



	if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {

		perror("Failed to restrict privileges");

		goto err_close_ruleset;