tools/testing/selftests/exec/execveat.c

   1 /*
   2  * Copyright (c) 2014 Google, Inc.
   3  *
   4  * Licensed under the terms of the GNU GPL License version 2
   5  *
   6  * Selftests for execveat(2).
   7  */
   8
   9 #define _GNU_SOURCE  /* to get O_PATH, AT_EMPTY_PATH */
  10 #include <sys/sendfile.h>
  11 #include <sys/stat.h>
  12 #include <sys/syscall.h>
  13 #include <sys/types.h>
  14 #include <sys/wait.h>
  15 #include <errno.h>
  16 #include <fcntl.h>
  17 #include <limits.h>
  18 #include <stdio.h>
  19 #include <stdlib.h>
  20 #include <string.h>
  21 #include <unistd.h>
  22
  23 static char longpath[2 * PATH_MAX] = "";
  24 static char *envp[] = { "IN_TEST=yes", NULL, NULL };
  25 static char *argv[] = { "execveat", "99", NULL };
  26
  27 static int execveat_(int fd, const char *path, char **argv, char **envp,
  28                      int flags)
  29 {
  30 #ifdef __NR_execveat
  31         return syscall(__NR_execveat, fd, path, argv, envp, flags);
  32 #else
  33         errno = ENOSYS;
  34         return -1;
  35 #endif
  36 }
  37
  38 #define check_execveat_fail(fd, path, flags, errno)     \
  39         _check_execveat_fail(fd, path, flags, errno, #errno)
  40 static int _check_execveat_fail(int fd, const char *path, int flags,
  41                                 int expected_errno, const char *errno_str)
  42 {
  43         int rc;
  44
  45         errno = 0;
  46         printf("Check failure of execveat(%d, '%s', %d) with %s... ",
  47                 fd, path?:"(null)", flags, errno_str);
  48         rc = execveat_(fd, path, argv, envp, flags);
  49
  50         if (rc > 0) {
  51                 printf("[FAIL] (unexpected success from execveat(2))\n");
  52                 return 1;
  53         }
  54         if (errno != expected_errno) {
  55                 printf("[FAIL] (expected errno %d (%s) not %d (%s)\n",
  56                         expected_errno, strerror(expected_errno),
  57                         errno, strerror(errno));
  58                 return 1;
  59         }
  60         printf("[OK]\n");
  61         return 0;
  62 }
  63
  64 static int check_execveat_invoked_rc(int fd, const char *path, int flags,
  65                                      int expected_rc, int expected_rc2)
  66 {
  67         int status;
  68         int rc;
  69         pid_t child;
  70         int pathlen = path ? strlen(path) : 0;
  71
  72         if (pathlen > 40)
  73                 printf("Check success of execveat(%d, '%.20s...%s', %d)... ",
  74                         fd, path, (path + pathlen - 20), flags);
  75         else
  76                 printf("Check success of execveat(%d, '%s', %d)... ",
  77                         fd, path?:"(null)", flags);
  78         child = fork();
  79         if (child < 0) {
  80                 printf("[FAIL] (fork() failed)\n");
  81                 return 1;
  82         }
  83         if (child == 0) {
  84                 /* Child: do execveat(). */
  85                 rc = execveat_(fd, path, argv, envp, flags);
  86                 printf("[FAIL]: execveat() failed, rc=%d errno=%d (%s)\n",
  87                         rc, errno, strerror(errno));
  88                 exit(1);  /* should not reach here */
  89         }
  90         /* Parent: wait for & check child's exit status. */
  91         rc = waitpid(child, &status, 0);
  92         if (rc != child) {
  93                 printf("[FAIL] (waitpid(%d,...) returned %d)\n", child, rc);
  94                 return 1;
  95         }
  96         if (!WIFEXITED(status)) {
  97                 printf("[FAIL] (child %d did not exit cleanly, status=%08x)\n",
  98                         child, status);
  99                 return 1;
 100         }
 101         if ((WEXITSTATUS(status) != expected_rc) &&
 102             (WEXITSTATUS(status) != expected_rc2)) {
 103                 printf("[FAIL] (child %d exited with %d not %d nor %d)\n",
 104                         child, WEXITSTATUS(status), expected_rc, expected_rc2);
 105                 return 1;
 106         }
 107         printf("[OK]\n");
 108         return 0;
 109 }
 110
 111 static int check_execveat(int fd, const char *path, int flags)
 112 {
 113         return check_execveat_invoked_rc(fd, path, flags, 99, 99);
 114 }
 115
 116 static char *concat(const char *left, const char *right)
 117 {
 118         char *result = malloc(strlen(left) + strlen(right) + 1);
 119
 120         strcpy(result, left);
 121         strcat(result, right);
 122         return result;
 123 }
 124
 125 static int open_or_die(const char *filename, int flags)
 126 {
 127         int fd = open(filename, flags);
 128
 129         if (fd < 0) {
 130                 printf("Failed to open '%s'; "
 131                         "check prerequisites are available\n", filename);
 132                 exit(1);
 133         }
 134         return fd;
 135 }
 136
 137 static void exe_cp(const char *src, const char *dest)
 138 {
 139         int in_fd = open_or_die(src, O_RDONLY);
 140         int out_fd = open(dest, O_RDWR|O_CREAT|O_TRUNC, 0755);
 141         struct stat info;
 142
 143         fstat(in_fd, &info);
 144         sendfile(out_fd, in_fd, NULL, info.st_size);
 145         close(in_fd);
 146         close(out_fd);
 147 }
 148
 149 #define XX_DIR_LEN 200
 150 static int check_execveat_pathmax(int dot_dfd, const char *src, int is_script)
 151 {
 152         int fail = 0;
 153         int ii, count, len;
 154         char longname[XX_DIR_LEN + 1];
 155         int fd;
 156
 157         if (*longpath == '\0') {
 158                 /* Create a filename close to PATH_MAX in length */
 159                 memset(longname, 'x', XX_DIR_LEN - 1);
 160                 longname[XX_DIR_LEN - 1] = '/';
 161                 longname[XX_DIR_LEN] = '\0';
 162                 count = (PATH_MAX - 3) / XX_DIR_LEN;
 163                 for (ii = 0; ii < count; ii++) {
 164                         strcat(longpath, longname);
 165                         mkdir(longpath, 0755);
 166                 }
 167                 len = (PATH_MAX - 3) - (count * XX_DIR_LEN);
 168                 if (len <= 0)
 169                         len = 1;
 170                 memset(longname, 'y', len);
 171                 longname[len] = '\0';
 172                 strcat(longpath, longname);
 173         }
 174         exe_cp(src, longpath);
 175
 176         /*
 177          * Execute as a pre-opened file descriptor, which works whether this is
 178          * a script or not (because the interpreter sees a filename like
 179          * "/dev/fd/20").
 180          */
 181         fd = open(longpath, O_RDONLY);
 182         if (fd > 0) {
 183                 printf("Invoke copy of '%s' via filename of length %zu:\n",
 184                         src, strlen(longpath));
 185                 fail += check_execveat(fd, "", AT_EMPTY_PATH);
 186         } else {
 187                 printf("Failed to open length %zu filename, errno=%d (%s)\n",
 188                         strlen(longpath), errno, strerror(errno));
 189                 fail++;
 190         }
 191
 192         /*
 193          * Execute as a long pathname relative to ".".  If this is a script,
 194          * the interpreter will launch but fail to open the script because its
 195          * name ("/dev/fd/5/xxx....") is bigger than PATH_MAX.
 196          *
 197          * The failure code is usually 127 (POSIX: "If a command is not found,
 198          * the exit status shall be 127."), but some systems give 126 (POSIX:
 199          * "If the command name is found, but it is not an executable utility,
 200          * the exit status shall be 126."), so allow either.
 201          */
 202         if (is_script)
 203                 fail += check_execveat_invoked_rc(dot_dfd, longpath, 0,
 204                                                   127, 126);
 205         else
 206                 fail += check_execveat(dot_dfd, longpath, 0);
 207
 208         return fail;
 209 }
 210
 211 static int run_tests(void)
 212 {
 213         int fail = 0;
 214         char *fullname = realpath("execveat", NULL);
 215         char *fullname_script = realpath("script", NULL);
 216         char *fullname_symlink = concat(fullname, ".symlink");
 217         int subdir_dfd = open_or_die("subdir", O_DIRECTORY|O_RDONLY);
 218         int subdir_dfd_ephemeral = open_or_die("subdir.ephemeral",
 219                                                O_DIRECTORY|O_RDONLY);
 220         int dot_dfd = open_or_die(".", O_DIRECTORY|O_RDONLY);
 221         int dot_dfd_path = open_or_die(".", O_DIRECTORY|O_RDONLY|O_PATH);
 222         int dot_dfd_cloexec = open_or_die(".", O_DIRECTORY|O_RDONLY|O_CLOEXEC);
 223         int fd = open_or_die("execveat", O_RDONLY);
 224         int fd_path = open_or_die("execveat", O_RDONLY|O_PATH);
 225         int fd_symlink = open_or_die("execveat.symlink", O_RDONLY);
 226         int fd_denatured = open_or_die("execveat.denatured", O_RDONLY);
 227         int fd_denatured_path = open_or_die("execveat.denatured",
 228                                             O_RDONLY|O_PATH);
 229         int fd_script = open_or_die("script", O_RDONLY);
 230         int fd_ephemeral = open_or_die("execveat.ephemeral", O_RDONLY);
 231         int fd_ephemeral_path = open_or_die("execveat.path.ephemeral",
 232                                             O_RDONLY|O_PATH);
 233         int fd_script_ephemeral = open_or_die("script.ephemeral", O_RDONLY);
 234         int fd_cloexec = open_or_die("execveat", O_RDONLY|O_CLOEXEC);
 235         int fd_script_cloexec = open_or_die("script", O_RDONLY|O_CLOEXEC);
 236
 237         /* Check if we have execveat at all, and bail early if not */
 238         errno = 0;
 239         execveat_(-1, NULL, NULL, NULL, 0);
 240         if (errno == ENOSYS) {
 241                 printf("[FAIL] ENOSYS calling execveat - no kernel support?\n");
 242                 return 1;
 243         }
 244
 245         /* Change file position to confirm it doesn't affect anything */
 246         lseek(fd, 10, SEEK_SET);
 247
 248         /* Normal executable file: */
 249         /*   dfd + path */
 250         fail += check_execveat(subdir_dfd, "../execveat", 0);
 251         fail += check_execveat(dot_dfd, "execveat", 0);
 252         fail += check_execveat(dot_dfd_path, "execveat", 0);
 253         /*   absolute path */
 254         fail += check_execveat(AT_FDCWD, fullname, 0);
 255         /*   absolute path with nonsense dfd */
 256         fail += check_execveat(99, fullname, 0);
 257         /*   fd + no path */
 258         fail += check_execveat(fd, "", AT_EMPTY_PATH);
 259         /*   O_CLOEXEC fd + no path */
 260         fail += check_execveat(fd_cloexec, "", AT_EMPTY_PATH);
 261         /*   O_PATH fd */
 262         fail += check_execveat(fd_path, "", AT_EMPTY_PATH);
 263
 264         /* Mess with executable file that's already open: */
 265         /*   fd + no path to a file that's been renamed */
 266         rename("execveat.ephemeral", "execveat.moved");
 267         fail += check_execveat(fd_ephemeral, "", AT_EMPTY_PATH);
 268         /*   fd + no path to a file that's been deleted */
 269         unlink("execveat.moved"); /* remove the file now fd open */
 270         fail += check_execveat(fd_ephemeral, "", AT_EMPTY_PATH);
 271
 272         /* Mess with executable file that's already open with O_PATH */
 273         /*   fd + no path to a file that's been deleted */
 274         unlink("execveat.path.ephemeral");
 275         fail += check_execveat(fd_ephemeral_path, "", AT_EMPTY_PATH);
 276
 277         /* Invalid argument failures */
 278         fail += check_execveat_fail(fd, "", 0, ENOENT);
 279         fail += check_execveat_fail(fd, NULL, AT_EMPTY_PATH, EFAULT);
 280
 281         /* Symlink to executable file: */
 282         /*   dfd + path */
 283         fail += check_execveat(dot_dfd, "execveat.symlink", 0);
 284         fail += check_execveat(dot_dfd_path, "execveat.symlink", 0);
 285         /*   absolute path */
 286         fail += check_execveat(AT_FDCWD, fullname_symlink, 0);
 287         /*   fd + no path, even with AT_SYMLINK_NOFOLLOW (already followed) */
 288         fail += check_execveat(fd_symlink, "", AT_EMPTY_PATH);
 289         fail += check_execveat(fd_symlink, "",
 290                                AT_EMPTY_PATH|AT_SYMLINK_NOFOLLOW);
 291
 292         /* Symlink fails when AT_SYMLINK_NOFOLLOW set: */
 293         /*   dfd + path */
 294         fail += check_execveat_fail(dot_dfd, "execveat.symlink",
 295                                     AT_SYMLINK_NOFOLLOW, ELOOP);
 296         fail += check_execveat_fail(dot_dfd_path, "execveat.symlink",
 297                                     AT_SYMLINK_NOFOLLOW, ELOOP);
 298         /*   absolute path */
 299         fail += check_execveat_fail(AT_FDCWD, fullname_symlink,
 300                                     AT_SYMLINK_NOFOLLOW, ELOOP);
 301
 302         /* Shell script wrapping executable file: */
 303         /*   dfd + path */
 304         fail += check_execveat(subdir_dfd, "../script", 0);
 305         fail += check_execveat(dot_dfd, "script", 0);
 306         fail += check_execveat(dot_dfd_path, "script", 0);
 307         /*   absolute path */
 308         fail += check_execveat(AT_FDCWD, fullname_script, 0);
 309         /*   fd + no path */
 310         fail += check_execveat(fd_script, "", AT_EMPTY_PATH);
 311         fail += check_execveat(fd_script, "",
 312                                AT_EMPTY_PATH|AT_SYMLINK_NOFOLLOW);
 313         /*   O_CLOEXEC fd fails for a script (as script file inaccessible) */
 314         fail += check_execveat_fail(fd_script_cloexec, "", AT_EMPTY_PATH,
 315                                     ENOENT);
 316         fail += check_execveat_fail(dot_dfd_cloexec, "script", 0, ENOENT);
 317
 318         /* Mess with script file that's already open: */
 319         /*   fd + no path to a file that's been renamed */
 320         rename("script.ephemeral", "script.moved");
 321         fail += check_execveat(fd_script_ephemeral, "", AT_EMPTY_PATH);
 322         /*   fd + no path to a file that's been deleted */
 323         unlink("script.moved"); /* remove the file while fd open */
 324         fail += check_execveat(fd_script_ephemeral, "", AT_EMPTY_PATH);
 325
 326         /* Rename a subdirectory in the path: */
 327         rename("subdir.ephemeral", "subdir.moved");
 328         fail += check_execveat(subdir_dfd_ephemeral, "../script", 0);
 329         fail += check_execveat(subdir_dfd_ephemeral, "script", 0);
 330         /* Remove the subdir and its contents */
 331         unlink("subdir.moved/script");
 332         unlink("subdir.moved");
 333         /* Shell loads via deleted subdir OK because name starts with .. */
 334         fail += check_execveat(subdir_dfd_ephemeral, "../script", 0);
 335         fail += check_execveat_fail(subdir_dfd_ephemeral, "script", 0, ENOENT);
 336
 337         /* Flag values other than AT_SYMLINK_NOFOLLOW => EINVAL */
 338         fail += check_execveat_fail(dot_dfd, "execveat", 0xFFFF, EINVAL);
 339         /* Invalid path => ENOENT */
 340         fail += check_execveat_fail(dot_dfd, "no-such-file", 0, ENOENT);
 341         fail += check_execveat_fail(dot_dfd_path, "no-such-file", 0, ENOENT);
 342         fail += check_execveat_fail(AT_FDCWD, "no-such-file", 0, ENOENT);
 343         /* Attempt to execute directory => EACCES */
 344         fail += check_execveat_fail(dot_dfd, "", AT_EMPTY_PATH, EACCES);
 345         /* Attempt to execute non-executable => EACCES */
 346         fail += check_execveat_fail(dot_dfd, "Makefile", 0, EACCES);
 347         fail += check_execveat_fail(fd_denatured, "", AT_EMPTY_PATH, EACCES);
 348         fail += check_execveat_fail(fd_denatured_path, "", AT_EMPTY_PATH,
 349                                     EACCES);
 350         /* Attempt to execute nonsense FD => EBADF */
 351         fail += check_execveat_fail(99, "", AT_EMPTY_PATH, EBADF);
 352         fail += check_execveat_fail(99, "execveat", 0, EBADF);
 353         /* Attempt to execute relative to non-directory => ENOTDIR */
 354         fail += check_execveat_fail(fd, "execveat", 0, ENOTDIR);
 355
 356         fail += check_execveat_pathmax(dot_dfd, "execveat", 0);
 357         fail += check_execveat_pathmax(dot_dfd, "script", 1);
 358         return fail;
 359 }
 360
 361 static void prerequisites(void)
 362 {
 363         int fd;
 364         const char *script = "#!/bin/sh\nexit $*\n";
 365
 366         /* Create ephemeral copies of files */
 367         exe_cp("execveat", "execveat.ephemeral");
 368         exe_cp("execveat", "execveat.path.ephemeral");
 369         exe_cp("script", "script.ephemeral");
 370         mkdir("subdir.ephemeral", 0755);
 371
 372         fd = open("subdir.ephemeral/script", O_RDWR|O_CREAT|O_TRUNC, 0755);
 373         write(fd, script, strlen(script));
 374         close(fd);
 375 }
 376
 377 int main(int argc, char **argv)
 378 {
 379         int ii;
 380         int rc;
 381         const char *verbose = getenv("VERBOSE");
 382
 383         if (argc >= 2) {
 384                 /* If we are invoked with an argument, don't run tests. */
 385                 const char *in_test = getenv("IN_TEST");
 386
 387                 if (verbose) {
 388                         printf("  invoked with:");
 389                         for (ii = 0; ii < argc; ii++)
 390                                 printf(" [%d]='%s'", ii, argv[ii]);
 391                         printf("\n");
 392                 }
 393
 394                 /* Check expected environment transferred. */
 395                 if (!in_test || strcmp(in_test, "yes") != 0) {
 396                         printf("[FAIL] (no IN_TEST=yes in env)\n");
 397                         return 1;
 398                 }
 399
 400                 /* Use the final argument as an exit code. */
 401                 rc = atoi(argv[argc - 1]);
 402                 fflush(stdout);
 403         } else {
 404                 prerequisites();
 405                 if (verbose)
 406                         envp[1] = "VERBOSE=1";
 407                 rc = run_tests();
 408                 if (rc > 0)
 409                         printf("%d tests failed\n", rc);
 410         }
 411         return rc;
 412 }