posix/tst-wordexp-nocmd.c

   1 /* Test for (lack of) command execution in wordexp.
   2    Copyright (C) 1997-2020 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 /* This test optionally counts PIDs in a PID namespace to detect
  20    forks.  Without kernel support for that, it will merely look at the
  21    error codes from wordexp to check that no command execution
  22    happens.  */
  23
  24 #include <sched.h>
  25 #include <stdbool.h>
  26 #include <stdio.h>
  27 #include <stdlib.h>
  28 #include <support/check.h>
  29 #include <support/namespace.h>
  30 #include <support/xunistd.h>
  31 #include <wordexp.h>
  32
  33 /* Set to true if the test runs in a PID namespace and can therefore
  34    use next_pid below.  */
  35 static bool pid_tests_supported;
  36
  37 /* The next PID, as returned from next_pid below.  Only meaningful if
  38    pid_tests_supported.  */
  39 static pid_t expected_pid;
  40
  41 /* Allocate the next PID and return it.  The process is terminated.
  42    Note that the test itself advances the next PID.  */
  43 static pid_t
  44 next_pid (void)
  45 {
  46   pid_t pid = xfork ();
  47   if (pid == 0)
  48     _exit (0);
  49   xwaitpid (pid, NULL, 0);
  50   return pid;
  51 }
  52
  53 /* Check that evaluating PATTERN with WRDE_NOCMD results in
  54    EXPECTED_ERROR.  */
  55 static void
  56 expect_failure (const char *pattern, int expected_error)
  57 {
  58   printf ("info: testing pattern: %s\n", pattern);
  59   wordexp_t w;
  60   TEST_COMPARE (wordexp (pattern, &w, WRDE_NOCMD), expected_error);
  61   if (pid_tests_supported)
  62     TEST_COMPARE (expected_pid++, next_pid ());
  63 }
  64
  65 /* Run all the tests.  Invoked with different IFS values.  */
  66 static void
  67 run_tests (void)
  68 {
  69   /* Integer overflow in division.  */
  70   {
  71     static const char *const numbers[] = {
  72       "0",
  73       "1",
  74       "65536",
  75       "2147483648",
  76       "4294967296"
  77       "9223372036854775808",
  78       "18446744073709551616",
  79       "170141183460469231731687303715884105728",
  80       "340282366920938463463374607431768211456",
  81       NULL
  82     };
  83
  84     for (const char *const *num = numbers; *num != NULL; ++num)
  85       {
  86         wordexp_t w;
  87         char pattern[256];
  88         snprintf (pattern, sizeof (pattern), "$[(-%s)/(-1)]", *num);
  89         int ret = wordexp (pattern, &w, WRDE_NOCMD);
  90         if (ret == 0)
  91           {
  92             /* If the call is successful, the result must match the
  93                original number.  */
  94             TEST_COMPARE (w.we_wordc, 1);
  95             TEST_COMPARE_STRING (w.we_wordv[0], *num);
  96             TEST_COMPARE_STRING (w.we_wordv[1], NULL);
  97             wordfree (&w);
  98           }
  99         else
 100           /* Otherwise, the test must fail with a syntax error.  */
 101           TEST_COMPARE (ret, WRDE_SYNTAX);
 102
 103         /* In both cases, command execution is not permitted.  */
 104         if (pid_tests_supported)
 105           TEST_COMPARE (expected_pid++, next_pid ());
 106       }
 107   }
 108
 109   /* (Lack of) command execution tests.  */
 110
 111   expect_failure ("$(ls)", WRDE_CMDSUB);
 112
 113   /* Test for CVE-2014-7817. We test 3 combinations of command
 114      substitution inside an arithmetic expression to make sure that
 115      no commands are executed and error is returned.  */
 116   expect_failure ("$((`echo 1`))", WRDE_CMDSUB);
 117   expect_failure ("$((1+`echo 1`))", WRDE_CMDSUB);
 118   expect_failure ("$((1+$((`echo 1`))))", WRDE_CMDSUB);
 119
 120   expect_failure ("$[1/0]", WRDE_SYNTAX); /* BZ 18100.  */
 121 }
 122
 123 static void
 124 subprocess (void *closure)
 125 {
 126   expected_pid = 2;
 127   if (pid_tests_supported)
 128     TEST_COMPARE (expected_pid++, next_pid ());
 129
 130   /* Check that triggering command execution via wordexp results in a
 131      PID increase.  */
 132   if (pid_tests_supported)
 133     {
 134       wordexp_t w;
 135       TEST_COMPARE (wordexp ("$(echo Test)", &w, 0), 0);
 136       TEST_COMPARE (w.we_wordc, 1);
 137       TEST_COMPARE_STRING (w.we_wordv[0], "Test");
 138       TEST_COMPARE_STRING (w.we_wordv[1], NULL);
 139       wordfree (&w);
 140
 141       pid_t n = next_pid ();
 142       printf ("info: self-test resulted in PID %d (processes created: %d)\n",
 143               (int) n, (int) (n - expected_pid));
 144       TEST_VERIFY (n > expected_pid);
 145       expected_pid = n + 1;
 146   }
 147
 148   puts ("info: testing without IFS");
 149   unsetenv ("IFS");
 150   run_tests ();
 151
 152   puts ("info: testing with IFS");
 153   TEST_COMPARE (setenv ("IFS", " \t\n", 1), 0);
 154   run_tests ();
 155 }
 156
 157 static int
 158 do_test (void)
 159 {
 160   support_become_root ();
 161
 162 #ifdef CLONE_NEWPID
 163   if (unshare (CLONE_NEWPID) != 0)
 164     printf ("warning: unshare (CLONE_NEWPID) failed: %m\n"
 165             "warning: This leads to reduced test coverage.\n");
 166   else
 167     pid_tests_supported = true;
 168 #else
 169   printf ("warning: CLONE_NEWPID not available.\n"
 170           "warning: This leads to reduced test coverage.\n");
 171 #endif
 172
 173   /* CLONE_NEWPID only has an effect after fork.  */
 174   support_isolate_in_subprocess (subprocess, NULL);
 175
 176   return 0;
 177 }
 178
 179 #include <support/test-driver.c>