[PATCH v1 1/2] Landlock: Add signal control
Tahera Fahimi
fahimitahera at gmail.com
Fri Jul 5 21:21:42 UTC 2024
Currently, a sandbox process is not restricted to send a signal
(e.g. SIGKILL) to a process outside of the sandbox environment.
Ability to sending a signal for a sandboxed process should be
scoped the same way abstract unix sockets are scoped.
The same way as abstract unix socket, we extend "scoped" field
in a ruleset with "LANDLOCK_SCOPED_SIGNAL" to specify that a ruleset
will deny sending any signal from within a sandbox process to its
parent(i.e. any parent sandbox or non-sandboxed procsses).
Signed-off-by: Tahera Fahimi <fahimitahera at gmail.com>
---
include/uapi/linux/landlock.h | 3 +++
security/landlock/limits.h | 2 +-
security/landlock/task.c | 49 +++++++++++++++++++++++++++++++++++
3 files changed, 53 insertions(+), 1 deletion(-)
diff --git a/include/uapi/linux/landlock.h b/include/uapi/linux/landlock.h
index 010aaca5b05a..878479a1b9dd 100644
--- a/include/uapi/linux/landlock.h
+++ b/include/uapi/linux/landlock.h
@@ -291,8 +291,11 @@ struct landlock_net_port_attr {
* from connecting to an abstract unix socket created by a process
* outside the related Landlock domain (e.g. a parent domain or a process
* which is not sandboxed).
+ * - %LANDLOCK_SCOPED_SIGNAL: Restrict a sandboxed process from sending a signal
+ * to another process outside sandbox domain.
*/
/* clang-format off */
#define LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET (1ULL << 0)
+#define LANDLOCK_SCOPED_SIGNAL (1ULL << 1)
/* clang-format on*/
#endif /* _UAPI_LINUX_LANDLOCK_H */
diff --git a/security/landlock/limits.h b/security/landlock/limits.h
index eb01d0fb2165..fa28f9236407 100644
--- a/security/landlock/limits.h
+++ b/security/landlock/limits.h
@@ -26,7 +26,7 @@
#define LANDLOCK_MASK_ACCESS_NET ((LANDLOCK_LAST_ACCESS_NET << 1) - 1)
#define LANDLOCK_NUM_ACCESS_NET __const_hweight64(LANDLOCK_MASK_ACCESS_NET)
-#define LANDLOCK_LAST_SCOPE LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET
+#define LANDLOCK_LAST_SCOPE LANDLOCK_SCOPED_SIGNAL
#define LANDLOCK_MASK_SCOPE ((LANDLOCK_LAST_SCOPE << 1) - 1)
#define LANDLOCK_NUM_SCOPE __const_hweight64(LANDLOCK_MASK_SCOPE)
/* clang-format on */
diff --git a/security/landlock/task.c b/security/landlock/task.c
index acc6e0fbc111..caee485b97b2 100644
--- a/security/landlock/task.c
+++ b/security/landlock/task.c
@@ -168,11 +168,60 @@ static int hook_unix_may_send(struct socket *const sock,
return -EPERM;
}
+static bool signal_is_scoped(const struct landlock_ruleset *const sender_dom,
+ struct task_struct *const target)
+{
+ const struct landlock_ruleset *target_dom =
+ landlock_get_task_domain(target);
+
+ /* quick return if there is no domain or .scoped is not set */
+ if (!sender_dom || !get_scoped_accesses(sender_dom))
+ return true;
+
+ if (!target_dom || !get_scoped_accesses(target_dom))
+ return false;
+
+ /* other is scoped, they connect if they are in the same domain */
+ return domain_scope_le(sender_dom, target_dom);
+}
+
+static int hook_task_kill(struct task_struct *const p,
+ struct kernel_siginfo *const info, const int sig,
+ const struct cred *const cred)
+{
+ const struct landlock_ruleset *const dom =
+ landlock_get_current_domain();
+ bool ret = false;
+
+ if (!cred)
+ ret = signal_is_scoped(dom, p);
+ else
+ ret = signal_is_scoped(landlock_cred(cred)->domain, p);
+ if (ret)
+ return 0;
+ return EPERM;
+}
+
+static int hook_file_send_sigiotask(struct task_struct *tsk,
+ struct fown_struct *fown, int signum)
+{
+ const struct task_struct *result =
+ get_pid_task(fown->pid, fown->pid_type);
+
+ const struct landlock_ruleset *const dom =
+ landlock_get_task_domain(result);
+ if (signal_is_scoped(dom, tsk))
+ return 0;
+ return EPERM;
+}
+
static struct security_hook_list landlock_hooks[] __ro_after_init = {
LSM_HOOK_INIT(ptrace_access_check, hook_ptrace_access_check),
LSM_HOOK_INIT(ptrace_traceme, hook_ptrace_traceme),
LSM_HOOK_INIT(unix_stream_connect, hook_unix_stream_connect),
LSM_HOOK_INIT(unix_may_send, hook_unix_may_send),
+ LSM_HOOK_INIT(task_kill, hook_task_kill),
+ LSM_HOOK_INIT(file_send_sigiotask, hook_file_send_sigiotask),
};
__init void landlock_add_task_hooks(void)
--
2.34.1
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