selftests/landlock: Test inherited restriction of abstract UNIX socket

A socket can be shared between multiple processes, so it can connect and
send data to them. Provide a test scenario where a sandboxed process
inherits a socket's file descriptor. The process cannot connect or send
data to the inherited socket since the process is scoped.

Test coverage for security/landlock is 92.0% of 1013 lines according to
gcc/gcov-14.

Signed-off-by: Tahera Fahimi <fahimitahera@gmail.com>
Link: https://lore.kernel.org/r/1428574deec13603b6ab2f2ed68ecbfa3b63bcb3.1725494372.git.fahimitahera@gmail.com
[mic: Remove negative ASSERT, fix potential race condition because of
closed connections, remove useless buffer, add test coverage]
Signed-off-by: Mickaël Salaün <mic@digikod.net>

diff --git a/tools/testing/selftests/landlock/scoped_abstract_unix_test.c b/tools/testing/selftests/landlock/scoped_abstract_unix_test.c
index ad97f14f97dea39716387792c13e63506a7259a5..a6b59d2ab1b42b125919daca2d7c7d2788f8d37c 100644 (file)
--- a/tools/testing/selftests/landlock/scoped_abstract_unix_test.c
+++ b/tools/testing/selftests/landlock/scoped_abstract_unix_test.c
@@ -974,4 +974,68 @@ TEST(datagram_sockets)
                _metadata->exit_code = KSFT_FAIL;
 }
 
+TEST(self_connect)
+{
+       struct service_fixture connected_addr, non_connected_addr;
+       int connected_socket, non_connected_socket, status;
+       pid_t child;
+
+       drop_caps(_metadata);
+       memset(&connected_addr, 0, sizeof(connected_addr));
+       set_unix_address(&connected_addr, 0);
+       memset(&non_connected_addr, 0, sizeof(non_connected_addr));
+       set_unix_address(&non_connected_addr, 1);
+
+       connected_socket = socket(AF_UNIX, SOCK_DGRAM, 0);
+       non_connected_socket = socket(AF_UNIX, SOCK_DGRAM, 0);
+       ASSERT_LE(0, connected_socket);
+       ASSERT_LE(0, non_connected_socket);
+
+       ASSERT_EQ(0, bind(connected_socket, &connected_addr.unix_addr,
+                         connected_addr.unix_addr_len));
+       ASSERT_EQ(0, bind(non_connected_socket, &non_connected_addr.unix_addr,
+                         non_connected_addr.unix_addr_len));
+
+       child = fork();
+       ASSERT_LE(0, child);
+       if (child == 0) {
+               /* Child's domain is scoped. */
+               create_scoped_domain(_metadata,
+                                    LANDLOCK_SCOPE_ABSTRACT_UNIX_SOCKET);
+
+               /*
+                * The child inherits the sockets, and cannot connect or
+                * send data to them.
+                */
+               ASSERT_EQ(-1,
+                         connect(connected_socket, &connected_addr.unix_addr,
+                                 connected_addr.unix_addr_len));
+               ASSERT_EQ(EPERM, errno);
+
+               ASSERT_EQ(-1, sendto(connected_socket, ".", 1, 0,
+                                    &connected_addr.unix_addr,
+                                    connected_addr.unix_addr_len));
+               ASSERT_EQ(EPERM, errno);
+
+               ASSERT_EQ(-1, sendto(non_connected_socket, ".", 1, 0,
+                                    &non_connected_addr.unix_addr,
+                                    non_connected_addr.unix_addr_len));
+               ASSERT_EQ(EPERM, errno);
+
+               EXPECT_EQ(0, close(connected_socket));
+               EXPECT_EQ(0, close(non_connected_socket));
+               _exit(_metadata->exit_code);
+               return;
+       }
+
+       /* Waits for all tests to finish. */
+       ASSERT_EQ(child, waitpid(child, &status, 0));
+       EXPECT_EQ(0, close(connected_socket));
+       EXPECT_EQ(0, close(non_connected_socket));
+
+       if (WIFSIGNALED(status) || !WIFEXITED(status) ||
+           WEXITSTATUS(status) != EXIT_SUCCESS)
+               _metadata->exit_code = KSFT_FAIL;
+}
+
 TEST_HARNESS_MAIN