1// SPDX-License-Identifier: GPL-2.0
2
3/*
4 * Copyright (C) 2020 Google LLC.
5 */
6
7#include <test_progs.h>
8#include <linux/limits.h>
9
10#include "bprm_opts.skel.h"
11#include "network_helpers.h"
12#include "task_local_storage_helpers.h"
13
14static const char * const bash_envp[] = { "TMPDIR=shouldnotbeset", NULL };
15
16static int update_storage(int map_fd, int secureexec)
17{
18	int task_fd, ret = 0;
19
20	task_fd = sys_pidfd_open(getpid(), 0);
21	if (task_fd < 0)
22		return errno;
23
24	ret = bpf_map_update_elem(map_fd, &task_fd, &secureexec, BPF_NOEXIST);
25	if (ret)
26		ret = errno;
27
28	close(task_fd);
29	return ret;
30}
31
32static int run_set_secureexec(int map_fd, int secureexec)
33{
34	int child_pid, child_status, ret, null_fd;
35
36	child_pid = fork();
37	if (child_pid == 0) {
38		null_fd = open("/dev/null", O_WRONLY);
39		if (null_fd == -1)
40			exit(errno);
41		dup2(null_fd, STDOUT_FILENO);
42		dup2(null_fd, STDERR_FILENO);
43		close(null_fd);
44
45		/* Ensure that all executions from hereon are
46		 * secure by setting a local storage which is read by
47		 * the bprm_creds_for_exec hook and sets bprm->secureexec.
48		 */
49		ret = update_storage(map_fd, secureexec);
50		if (ret)
51			exit(ret);
52
53		/* If the binary is executed with securexec=1, the dynamic
54		 * loader ingores and unsets certain variables like LD_PRELOAD,
55		 * TMPDIR etc. TMPDIR is used here to simplify the example, as
56		 * LD_PRELOAD requires a real .so file.
57		 *
58		 * If the value of TMPDIR is set, the bash command returns 10
59		 * and if the value is unset, it returns 20.
60		 */
61		execle("/bin/bash", "bash", "-c",
62		       "[[ -z \"${TMPDIR}\" ]] || exit 10 && exit 20", NULL,
63		       bash_envp);
64		exit(errno);
65	} else if (child_pid > 0) {
66		waitpid(child_pid, &child_status, 0);
67		ret = WEXITSTATUS(child_status);
68
69		/* If a secureexec occurred, the exit status should be 20 */
70		if (secureexec && ret == 20)
71			return 0;
72
73		/* If normal execution happened, the exit code should be 10 */
74		if (!secureexec && ret == 10)
75			return 0;
76	}
77
78	return -EINVAL;
79}
80
81void test_test_bprm_opts(void)
82{
83	int err, duration = 0;
84	struct bprm_opts *skel = NULL;
85
86	skel = bprm_opts__open_and_load();
87	if (CHECK(!skel, "skel_load", "skeleton failed\n"))
88		goto close_prog;
89
90	err = bprm_opts__attach(skel);
91	if (CHECK(err, "attach", "attach failed: %d\n", err))
92		goto close_prog;
93
94	/* Run the test with the secureexec bit unset */
95	err = run_set_secureexec(bpf_map__fd(skel->maps.secure_exec_task_map),
96				 0 /* secureexec */);
97	if (CHECK(err, "run_set_secureexec:0", "err = %d\n", err))
98		goto close_prog;
99
100	/* Run the test with the secureexec bit set */
101	err = run_set_secureexec(bpf_map__fd(skel->maps.secure_exec_task_map),
102				 1 /* secureexec */);
103	if (CHECK(err, "run_set_secureexec:1", "err = %d\n", err))
104		goto close_prog;
105
106close_prog:
107	bprm_opts__destroy(skel);
108}
109