LXR linux/tools/testing/selftests/bpf/prog_tests/test_bprm

   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
  13#ifndef __NR_pidfd_open
  14#define __NR_pidfd_open 434
  15#endif
  16
  17static const char * const bash_envp[] = { "TMPDIR=shouldnotbeset", NULL };
  18
  19static inline int sys_pidfd_open(pid_t pid, unsigned int flags)
  20{
  21        return syscall(__NR_pidfd_open, pid, flags);
  22}
  23
  24static int update_storage(int map_fd, int secureexec)
  25{
  26        int task_fd, ret = 0;
  27
  28        task_fd = sys_pidfd_open(getpid(), 0);
  29        if (task_fd < 0)
  30                return errno;
  31
  32        ret = bpf_map_update_elem(map_fd, &task_fd, &secureexec, BPF_NOEXIST);
  33        if (ret)
  34                ret = errno;
  35
  36        close(task_fd);
  37        return ret;
  38}
  39
  40static int run_set_secureexec(int map_fd, int secureexec)
  41{
  42        int child_pid, child_status, ret, null_fd;
  43
  44        child_pid = fork();
  45        if (child_pid == 0) {
  46                null_fd = open("/dev/null", O_WRONLY);
  47                if (null_fd == -1)
  48                        exit(errno);
  49                dup2(null_fd, STDOUT_FILENO);
  50                dup2(null_fd, STDERR_FILENO);
  51                close(null_fd);
  52
  53                /* Ensure that all executions from hereon are
  54                 * secure by setting a local storage which is read by
  55                 * the bprm_creds_for_exec hook and sets bprm->secureexec.
  56                 */
  57                ret = update_storage(map_fd, secureexec);
  58                if (ret)
  59                        exit(ret);
  60
  61                /* If the binary is executed with securexec=1, the dynamic
  62                 * loader ingores and unsets certain variables like LD_PRELOAD,
  63                 * TMPDIR etc. TMPDIR is used here to simplify the example, as
  64                 * LD_PRELOAD requires a real .so file.
  65                 *
  66                 * If the value of TMPDIR is set, the bash command returns 10
  67                 * and if the value is unset, it returns 20.
  68                 */
  69                execle("/bin/bash", "bash", "-c",
  70                       "[[ -z \"${TMPDIR}\" ]] || exit 10 && exit 20", NULL,
  71                       bash_envp);
  72                exit(errno);
  73        } else if (child_pid > 0) {
  74                waitpid(child_pid, &child_status, 0);
  75                ret = WEXITSTATUS(child_status);
  76
  77                /* If a secureexec occurred, the exit status should be 20 */
  78                if (secureexec && ret == 20)
  79                        return 0;
  80
  81                /* If normal execution happened, the exit code should be 10 */
  82                if (!secureexec && ret == 10)
  83                        return 0;
  84        }
  85
  86        return -EINVAL;
  87}
  88
  89void test_test_bprm_opts(void)
  90{
  91        int err, duration = 0;
  92        struct bprm_opts *skel = NULL;
  93
  94        skel = bprm_opts__open_and_load();
  95        if (CHECK(!skel, "skel_load", "skeleton failed\n"))
  96                goto close_prog;
  97
  98        err = bprm_opts__attach(skel);
  99        if (CHECK(err, "attach", "attach failed: %d\n", err))
 100                goto close_prog;
 101
 102        /* Run the test with the secureexec bit unset */
 103        err = run_set_secureexec(bpf_map__fd(skel->maps.secure_exec_task_map),
 104                                 0 /* secureexec */);
 105        if (CHECK(err, "run_set_secureexec:0", "err = %d\n", err))
 106                goto close_prog;
 107
 108        /* Run the test with the secureexec bit set */
 109        err = run_set_secureexec(bpf_map__fd(skel->maps.secure_exec_task_map),
 110                                 1 /* secureexec */);
 111        if (CHECK(err, "run_set_secureexec:1", "err = %d\n", err))
 112                goto close_prog;
 113
 114close_prog:
 115        bprm_opts__destroy(skel);
 116}
 117