Unverified Commit f490e205 authored by Tahera Fahimi's avatar Tahera Fahimi Committed by Mickaël Salaün
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samples/landlock: Add support for signal scoping 



The sandboxer can receive the character "s" as input from the
environment variable LL_SCOPE to restrict sandboxed processes from
sending signals to processes outside of the sandbox.

Example
=======

Create a sandboxed shell and pass the character "s" to LL_SCOPED:
  LL_FS_RO=/ LL_FS_RW=. LL_SCOPED="s" ./sandboxer /bin/bash

Try to send a SIGTRAP to a process with process ID <PID> through:
  kill -SIGTRAP <PID>

The sandboxed process should not be able to send the signal.

Signed-off-by: default avatarTahera Fahimi <fahimitahera@gmail.com>
Link: https://lore.kernel.org/r/1f3f1992b2abeb8e5d7aa61b854e1b0721978b9a.1725657728.git.fahimitahera@gmail.com


[mic: Improve commit message, simplify code, rebase on previous sample
change]
Signed-off-by: default avatarMickaël Salaün <mic@digikod.net>
parent f34e9ce5

samples/landlock/sandboxer.c

+14 −5
Original line number Diff line number Diff line
@@ -194,9 +194,11 @@ static bool check_ruleset_scope(const char *const env_var, 
	char *env_type_scope, *env_type_scope_next, *ipc_scoping_name;

	bool error = false;

	bool abstract_scoping = false;

	bool signal_scoping = false;



	/* Scoping is not supported by Landlock ABI */

	if (!(ruleset_attr->scoped & LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET))

	if (!(ruleset_attr->scoped &

	      (LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET | LANDLOCK_SCOPE_SIGNAL)))

		goto out_unset;



	env_type_scope = getenv(env_var);
@@ -210,6 +212,9 @@ static bool check_ruleset_scope(const char *const env_var, 
			strsep(&env_type_scope_next, ENV_DELIMITER))) {

		if (strcmp("a", ipc_scoping_name) == 0 && !abstract_scoping) {

			abstract_scoping = true;

		} else if (strcmp("s", ipc_scoping_name) == 0 &&

			   !signal_scoping) {

			signal_scoping = true;

		} else {

			fprintf(stderr, "Unknown or duplicate scope \"%s\"\n",

				ipc_scoping_name);
@@ -224,6 +229,8 @@ static bool check_ruleset_scope(const char *const env_var, 
out_unset:

	if (!abstract_scoping)

		ruleset_attr->scoped &= ~LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET;

	if (!signal_scoping)

		ruleset_attr->scoped &= ~LANDLOCK_SCOPE_SIGNAL;



	unsetenv(env_var);

	return error;
@@ -268,7 +275,8 @@ int main(const int argc, char *const argv[], char *const *const envp) 
		.handled_access_fs = access_fs_rw,

		.handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP |

				      LANDLOCK_ACCESS_NET_CONNECT_TCP,

		.scoped = LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET,

		.scoped = LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET |

			  LANDLOCK_SCOPE_SIGNAL,

	};



	if (argc < 2) {
@@ -305,7 +313,7 @@ int main(const int argc, char *const argv[], char *const *const envp) 
			"%s=\"/dev/null:/dev/full:/dev/zero:/dev/pts:/tmp\" "

			"%s=\"9418\" "

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

			"%s=\"a\" "

			"%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]);
@@ -378,8 +386,9 @@ int main(const int argc, char *const argv[], char *const *const envp) 


		__attribute__((fallthrough));

	case 5:

		/* Removes LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET for ABI < 6 */

		ruleset_attr.scoped &= ~LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET;

		/* Removes LANDLOCK_SCOPE_* for ABI < 6 */

		ruleset_attr.scoped &= ~(LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET |

					 LANDLOCK_SCOPE_SIGNAL);

		fprintf(stderr,

			"Hint: You should update the running kernel "

			"to leverage Landlock features "