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samples/landlock: Add support for signal scoping

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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: Tahera 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: Mickaël Salaün <mic@digikod.net>
This commit is contained in:
Tahera Fahimi 2024-09-06 15:30:07 -06:00 committed by Mickaël Salaün
parent f34e9ce5f4
commit f490e205bc
No known key found for this signature in database
GPG key ID: E5E3D0E88C82F6D2
1 changed files with 14 additions and 5 deletions
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19
samples/landlock/sandboxer.c
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@ -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 "