tools/testing/selftests/bpf/prog_tests/test_bprm_opts.c

   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
  14 static const char * const bash_envp[] = { "TMPDIR=shouldnotbeset", NULL };
  15
  16 static 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
  32 static 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 ignores 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
  81 void 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
 106 close_prog:
 107         bprm_opts__destroy(skel);
 108 }