// SPDX-License-Identifier: GPL-2.0
/*
* Landlock tests - Signal Scoping
*
* Copyright © 2024 Tahera Fahimi <[email protected]>
*/
#define _GNU_SOURCE
#include <errno.h>
#include <fcntl.h>
#include <linux/landlock.h>
#include <pthread.h>
#include <signal.h>
#include <sys/prctl.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include "common.h"
#include "scoped_common.h"
/* This variable is used for handling several signals. */
static volatile sig_atomic_t is_signaled;
/* clang-format off */
FIXTURE(scoping_signals) {};
/* clang-format on */
FIXTURE_VARIANT(scoping_signals)
{
int sig;
};
/* clang-format off */
FIXTURE_VARIANT_ADD(scoping_signals, sigtrap) {
/* clang-format on */
.sig = SIGTRAP,
};
/* clang-format off */
FIXTURE_VARIANT_ADD(scoping_signals, sigurg) {
/* clang-format on */
.sig = SIGURG,
};
/* clang-format off */
FIXTURE_VARIANT_ADD(scoping_signals, sighup) {
/* clang-format on */
.sig = SIGHUP,
};
/* clang-format off */
FIXTURE_VARIANT_ADD(scoping_signals, sigtstp) {
/* clang-format on */
.sig = SIGTSTP,
};
FIXTURE_SETUP(scoping_signals)
{
drop_caps(_metadata);
is_signaled = 0;
}
FIXTURE_TEARDOWN(scoping_signals)
{
}
static void scope_signal_handler(int sig, siginfo_t *info, void *ucontext)
{
if (sig == SIGTRAP || sig == SIGURG || sig == SIGHUP || sig == SIGTSTP)
is_signaled = 1;
}
/*
* In this test, a child process sends a signal to parent before and
* after getting scoped.
*/
TEST_F(scoping_signals, send_sig_to_parent)
{
int pipe_parent[2];
int status;
pid_t child;
pid_t parent = getpid();
struct sigaction action = {
.sa_sigaction = scope_signal_handler,
.sa_flags = SA_SIGINFO,
};
ASSERT_EQ(0, pipe2(pipe_parent, O_CLOEXEC));
ASSERT_LE(0, sigaction(variant->sig, &action, NULL));
/* The process should not have already been signaled. */
EXPECT_EQ(0, is_signaled);
child = fork();
ASSERT_LE(0, child);
if (child == 0) {
char buf_child;
int err;
EXPECT_EQ(0, close(pipe_parent[1]));
/*
* The child process can send signal to parent when
* domain is not scoped.
*/
err = kill(parent, variant->sig);
ASSERT_EQ(0, err);
ASSERT_EQ(1, read(pipe_parent[0], &buf_child, 1));
EXPECT_EQ(0, close(pipe_parent[0]));
create_scoped_domain(_metadata, LANDLOCK_SCOPE_SIGNAL);
/*
* The child process cannot send signal to the parent
* anymore.
*/
err = kill(parent, variant->sig);
ASSERT_EQ(-1, err);
ASSERT_EQ(EPERM, errno);
/*
* No matter of the domain, a process should be able to
* send a signal to itself.
*/
ASSERT_EQ(0, is_signaled);
ASSERT_EQ(0, raise(variant->sig));
ASSERT_EQ(1, is_signaled);
_exit(_metadata->exit_code);
return;
}
EXPECT_EQ(0, close(pipe_parent[0]));
/* Waits for a first signal to be received, without race condition. */
while (!is_signaled && !usleep(1))
;
ASSERT_EQ(1, is_signaled);
ASSERT_EQ(1, write(pipe_parent[1], ".", 1));
EXPECT_EQ(0, close(pipe_parent[1]));
is_signaled = 0;
ASSERT_EQ(child, waitpid(child, &status, 0));
if (WIFSIGNALED(status) || !WIFEXITED(status) ||
WEXITSTATUS(status) != EXIT_SUCCESS)
_metadata->exit_code = KSFT_FAIL;
EXPECT_EQ(0, is_signaled);
}
/* clang-format off */
FIXTURE(scoped_domains) {};
/* clang-format on */
#include "scoped_base_variants.h"
FIXTURE_SETUP(scoped_domains)
{
drop_caps(_metadata);
}
FIXTURE_TEARDOWN(scoped_domains)
{
}
/*
* This test ensures that a scoped process cannot send signal out of
* scoped domain.
*/
TEST_F(scoped_domains, check_access_signal)
{
pid_t child;
pid_t parent = getpid();
int status;
bool can_signal_child, can_signal_parent;
int pipe_parent[2], pipe_child[2];
char buf_parent;
int err;
can_signal_parent = !variant->domain_child;
can_signal_child = !variant->domain_parent;
if (variant->domain_both)
create_scoped_domain(_metadata, LANDLOCK_SCOPE_SIGNAL);
ASSERT_EQ(0, pipe2(pipe_parent, O_CLOEXEC));
ASSERT_EQ(0, pipe2(pipe_child, O_CLOEXEC));
child = fork();
ASSERT_LE(0, child);
if (child == 0) {
char buf_child;
EXPECT_EQ(0, close(pipe_child[0]));
EXPECT_EQ(0, close(pipe_parent[1]));
if (variant->domain_child)
create_scoped_domain(_metadata, LANDLOCK_SCOPE_SIGNAL);
ASSERT_EQ(1, write(pipe_child[1], ".", 1));
EXPECT_EQ(0, close(pipe_child[1]));
/* Waits for the parent to send signals. */
ASSERT_EQ(1, read(pipe_parent[0], &buf_child, 1));
EXPECT_EQ(0, close(pipe_parent[0]));
err = kill(parent, 0);
if (can_signal_parent) {
ASSERT_EQ(0, err);
} else {
ASSERT_EQ(-1, err);
ASSERT_EQ(EPERM, errno);
}
/*
* No matter of the domain, a process should be able to
* send a signal to itself.
*/
ASSERT_EQ(0, raise(0));
_exit(_metadata->exit_code);
return;
}
EXPECT_EQ(0, close(pipe_parent[0]));
EXPECT_EQ(0, close(pipe_child[1]));
if (variant->domain_parent)
create_scoped_domain(_metadata, LANDLOCK_SCOPE_SIGNAL);
ASSERT_EQ(1, read(pipe_child[0], &buf_parent, 1));
EXPECT_EQ(0, close(pipe_child[0]));
err = kill(child, 0);
if (can_signal_child) {
ASSERT_EQ(0, err);
} else {
ASSERT_EQ(-1, err);
ASSERT_EQ(EPERM, errno);
}
ASSERT_EQ(0, raise(0));
ASSERT_EQ(1, write(pipe_parent[1], ".", 1));
EXPECT_EQ(0, close(pipe_parent[1]));
ASSERT_EQ(child, waitpid(child, &status, 0));
if (WIFSIGNALED(status) || !WIFEXITED(status) ||
WEXITSTATUS(status) != EXIT_SUCCESS)
_metadata->exit_code = KSFT_FAIL;
}
static int thread_pipe[2];
enum thread_return {
THREAD_INVALID = 0,
THREAD_SUCCESS = 1,
THREAD_ERROR = 2,
};
void *thread_func(void *arg)
{
char buf;
if (read(thread_pipe[0], &buf, 1) != 1)
return (void *)THREAD_ERROR;
return (void *)THREAD_SUCCESS;
}
TEST(signal_scoping_threads)
{
pthread_t no_sandbox_thread, scoped_thread;
enum thread_return ret = THREAD_INVALID;
drop_caps(_metadata);
ASSERT_EQ(0, pipe2(thread_pipe, O_CLOEXEC));
ASSERT_EQ(0,
pthread_create(&no_sandbox_thread, NULL, thread_func, NULL));
/* Restricts the domain after creating the first thread. */
create_scoped_domain(_metadata, LANDLOCK_SCOPE_SIGNAL);
ASSERT_EQ(EPERM, pthread_kill(no_sandbox_thread, 0));
ASSERT_EQ(1, write(thread_pipe[1], ".", 1));
ASSERT_EQ(0, pthread_create(&scoped_thread, NULL, thread_func, NULL));
ASSERT_EQ(0, pthread_kill(scoped_thread, 0));
ASSERT_EQ(1, write(thread_pipe[1], ".", 1));
EXPECT_EQ(0, pthread_join(no_sandbox_thread, (void **)&ret));
EXPECT_EQ(THREAD_SUCCESS, ret);
EXPECT_EQ(0, pthread_join(scoped_thread, (void **)&ret));
EXPECT_EQ(THREAD_SUCCESS, ret);
EXPECT_EQ(0, close(thread_pipe[0]));
EXPECT_EQ(0, close(thread_pipe[1]));
}
const short backlog = 10;
static volatile sig_atomic_t signal_received;
static void handle_sigurg(int sig)
{
if (sig == SIGURG)
signal_received = 1;
else
signal_received = -1;
}
static int setup_signal_handler(int signal)
{
struct sigaction sa = {
.sa_handler = handle_sigurg,
};
if (sigemptyset(&sa.sa_mask))
return -1;
sa.sa_flags = SA_SIGINFO | SA_RESTART;
return sigaction(SIGURG, &sa, NULL);
}
/* clang-format off */
FIXTURE(fown) {};
/* clang-format on */
enum fown_sandbox {
SANDBOX_NONE,
SANDBOX_BEFORE_FORK,
SANDBOX_BEFORE_SETOWN,
SANDBOX_AFTER_SETOWN,
};
FIXTURE_VARIANT(fown)
{
const enum fown_sandbox sandbox_setown;
};
/* clang-format off */
FIXTURE_VARIANT_ADD(fown, no_sandbox) {
/* clang-format on */
.sandbox_setown = SANDBOX_NONE,
};
/* clang-format off */
FIXTURE_VARIANT_ADD(fown, sandbox_before_fork) {
/* clang-format on */
.sandbox_setown = SANDBOX_BEFORE_FORK,
};
/* clang-format off */
FIXTURE_VARIANT_ADD(fown, sandbox_before_setown) {
/* clang-format on */
.sandbox_setown = SANDBOX_BEFORE_SETOWN,
};
/* clang-format off */
FIXTURE_VARIANT_ADD(fown, sandbox_after_setown) {
/* clang-format on */
.sandbox_setown = SANDBOX_AFTER_SETOWN,
};
FIXTURE_SETUP(fown)
{
drop_caps(_metadata);
}
FIXTURE_TEARDOWN(fown)
{
}
/*
* Sending an out of bound message will trigger the SIGURG signal
* through file_send_sigiotask.
*/
TEST_F(fown, sigurg_socket)
{
int server_socket, recv_socket;
struct service_fixture server_address;
char buffer_parent;
int status;
int pipe_parent[2], pipe_child[2];
pid_t child;
memset(&server_address, 0, sizeof(server_address));
set_unix_address(&server_address, 0);
ASSERT_EQ(0, pipe2(pipe_parent, O_CLOEXEC));
ASSERT_EQ(0, pipe2(pipe_child, O_CLOEXEC));
if (variant->sandbox_setown == SANDBOX_BEFORE_FORK)
create_scoped_domain(_metadata, LANDLOCK_SCOPE_SIGNAL);
child = fork();
ASSERT_LE(0, child);
if (child == 0) {
int client_socket;
char buffer_child;
EXPECT_EQ(0, close(pipe_parent[1]));
EXPECT_EQ(0, close(pipe_child[0]));
ASSERT_EQ(0, setup_signal_handler(SIGURG));
client_socket = socket(AF_UNIX, SOCK_STREAM, 0);
ASSERT_LE(0, client_socket);
/* Waits for the parent to listen. */
ASSERT_EQ(1, read(pipe_parent[0], &buffer_child, 1));
ASSERT_EQ(0, connect(client_socket, &server_address.unix_addr,
server_address.unix_addr_len));
/*
* Waits for the parent to accept the connection, sandbox
* itself, and call fcntl(2).
*/
ASSERT_EQ(1, read(pipe_parent[0], &buffer_child, 1));
/* May signal itself. */
ASSERT_EQ(1, send(client_socket, ".", 1, MSG_OOB));
EXPECT_EQ(0, close(client_socket));
ASSERT_EQ(1, write(pipe_child[1], ".", 1));
EXPECT_EQ(0, close(pipe_child[1]));
/* Waits for the message to be received. */
ASSERT_EQ(1, read(pipe_parent[0], &buffer_child, 1));
EXPECT_EQ(0, close(pipe_parent[0]));
if (variant->sandbox_setown == SANDBOX_BEFORE_SETOWN) {
ASSERT_EQ(0, signal_received);
} else {
/*
* A signal is only received if fcntl(F_SETOWN) was
* called before any sandboxing or if the signal
* receiver is in the same domain.
*/
ASSERT_EQ(1, signal_received);
}
_exit(_metadata->exit_code);
return;
}
EXPECT_EQ(0, close(pipe_parent[0]));
EXPECT_EQ(0, close(pipe_child[1]));
server_socket = socket(AF_UNIX, SOCK_STREAM, 0);
ASSERT_LE(0, server_socket);
ASSERT_EQ(0, bind(server_socket, &server_address.unix_addr,
server_address.unix_addr_len));
ASSERT_EQ(0, listen(server_socket, backlog));
ASSERT_EQ(1, write(pipe_parent[1], ".", 1));
recv_socket = accept(server_socket, NULL, NULL);
ASSERT_LE(0, recv_socket);
if (variant->sandbox_setown == SANDBOX_BEFORE_SETOWN)
create_scoped_domain(_metadata, LANDLOCK_SCOPE_SIGNAL);
/*
* Sets the child to receive SIGURG for MSG_OOB. This uncommon use is
* a valid attack scenario which also simplifies this test.
*/
ASSERT_EQ(0, fcntl(recv_socket, F_SETOWN, child));
if (variant->sandbox_setown == SANDBOX_AFTER_SETOWN)
create_scoped_domain(_metadata, LANDLOCK_SCOPE_SIGNAL);
ASSERT_EQ(1, write(pipe_parent[1], ".", 1));
/* Waits for the child to send MSG_OOB. */
ASSERT_EQ(1, read(pipe_child[0], &buffer_parent, 1));
EXPECT_EQ(0, close(pipe_child[0]));
ASSERT_EQ(1, recv(recv_socket, &buffer_parent, 1, MSG_OOB));
EXPECT_EQ(0, close(recv_socket));
EXPECT_EQ(0, close(server_socket));
ASSERT_EQ(1, write(pipe_parent[1], ".", 1));
EXPECT_EQ(0, close(pipe_parent[1]));
ASSERT_EQ(child, waitpid(child, &status, 0));
if (WIFSIGNALED(status) || !WIFEXITED(status) ||
WEXITSTATUS(status) != EXIT_SUCCESS)
_metadata->exit_code = KSFT_FAIL;
}
TEST_HARNESS_MAIN
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