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 #include "../kselftest.h" 24 25 static char longpath[2 * PATH_MAX] = ""; 26 static char *envp[] = { "IN_TEST=yes", NULL, NULL }; 27 static char *argv[] = { "execveat", "99", NULL }; 28 29 static int execveat_(int fd, const char *path, char **argv, char **envp, 30 int flags) 31 { 32 #ifdef __NR_execveat 33 return syscall(__NR_execveat, fd, path, argv, envp, flags); 34 #else 35 errno = ENOSYS; 36 return -1; 37 #endif 38 } 39 40 #define check_execveat_fail(fd, path, flags, errno) \ 41 _check_execveat_fail(fd, path, flags, errno, #errno) 42 static int _check_execveat_fail(int fd, const char *path, int flags, 43 int expected_errno, const char *errno_str) 44 { 45 int rc; 46 47 errno = 0; 48 printf("Check failure of execveat(%d, '%s', %d) with %s... ", 49 fd, path?:"(null)", flags, errno_str); 50 rc = execveat_(fd, path, argv, envp, flags); 51 52 if (rc > 0) { 53 printf("[FAIL] (unexpected success from execveat(2))\n"); 54 return 1; 55 } 56 if (errno != expected_errno) { 57 printf("[FAIL] (expected errno %d (%s) not %d (%s)\n", 58 expected_errno, strerror(expected_errno), 59 errno, strerror(errno)); 60 return 1; 61 } 62 printf("[OK]\n"); 63 return 0; 64 } 65 66 static int check_execveat_invoked_rc(int fd, const char *path, int flags, 67 int expected_rc, int expected_rc2) 68 { 69 int status; 70 int rc; 71 pid_t child; 72 int pathlen = path ? strlen(path) : 0; 73 74 if (pathlen > 40) 75 printf("Check success of execveat(%d, '%.20s...%s', %d)... ", 76 fd, path, (path + pathlen - 20), flags); 77 else 78 printf("Check success of execveat(%d, '%s', %d)... ", 79 fd, path?:"(null)", flags); 80 child = fork(); 81 if (child < 0) { 82 printf("[FAIL] (fork() failed)\n"); 83 return 1; 84 } 85 if (child == 0) { 86 /* Child: do execveat(). */ 87 rc = execveat_(fd, path, argv, envp, flags); 88 printf("[FAIL]: execveat() failed, rc=%d errno=%d (%s)\n", 89 rc, errno, strerror(errno)); 90 exit(1); /* should not reach here */ 91 } 92 /* Parent: wait for & check child's exit status. */ 93 rc = waitpid(child, &status, 0); 94 if (rc != child) { 95 printf("[FAIL] (waitpid(%d,...) returned %d)\n", child, rc); 96 return 1; 97 } 98 if (!WIFEXITED(status)) { 99 printf("[FAIL] (child %d did not exit cleanly, status=%08x)\n", 100 child, status); 101 return 1; 102 } 103 if ((WEXITSTATUS(status) != expected_rc) && 104 (WEXITSTATUS(status) != expected_rc2)) { 105 printf("[FAIL] (child %d exited with %d not %d nor %d)\n", 106 child, WEXITSTATUS(status), expected_rc, expected_rc2); 107 return 1; 108 } 109 printf("[OK]\n"); 110 return 0; 111 } 112 113 static int check_execveat(int fd, const char *path, int flags) 114 { 115 return check_execveat_invoked_rc(fd, path, flags, 99, 99); 116 } 117 118 static char *concat(const char *left, const char *right) 119 { 120 char *result = malloc(strlen(left) + strlen(right) + 1); 121 122 strcpy(result, left); 123 strcat(result, right); 124 return result; 125 } 126 127 static int open_or_die(const char *filename, int flags) 128 { 129 int fd = open(filename, flags); 130 131 if (fd < 0) { 132 printf("Failed to open '%s'; " 133 "check prerequisites are available\n", filename); 134 exit(1); 135 } 136 return fd; 137 } 138 139 static void exe_cp(const char *src, const char *dest) 140 { 141 int in_fd = open_or_die(src, O_RDONLY); 142 int out_fd = open(dest, O_RDWR|O_CREAT|O_TRUNC, 0755); 143 struct stat info; 144 145 fstat(in_fd, &info); 146 sendfile(out_fd, in_fd, NULL, info.st_size); 147 close(in_fd); 148 close(out_fd); 149 } 150 151 #define XX_DIR_LEN 200 152 static int check_execveat_pathmax(int root_dfd, const char *src, int is_script) 153 { 154 int fail = 0; 155 int ii, count, len; 156 char longname[XX_DIR_LEN + 1]; 157 int fd; 158 159 if (*longpath == '\0') { 160 /* Create a filename close to PATH_MAX in length */ 161 char *cwd = getcwd(NULL, 0); 162 163 if (!cwd) { 164 printf("Failed to getcwd(), errno=%d (%s)\n", 165 errno, strerror(errno)); 166 return 2; 167 } 168 strcpy(longpath, cwd); 169 strcat(longpath, "/"); 170 memset(longname, 'x', XX_DIR_LEN - 1); 171 longname[XX_DIR_LEN - 1] = '/'; 172 longname[XX_DIR_LEN] = '\0'; 173 count = (PATH_MAX - 3 - strlen(cwd)) / XX_DIR_LEN; 174 for (ii = 0; ii < count; ii++) { 175 strcat(longpath, longname); 176 mkdir(longpath, 0755); 177 } 178 len = (PATH_MAX - 3 - strlen(cwd)) - (count * XX_DIR_LEN); 179 if (len <= 0) 180 len = 1; 181 memset(longname, 'y', len); 182 longname[len] = '\0'; 183 strcat(longpath, longname); 184 free(cwd); 185 } 186 exe_cp(src, longpath); 187 188 /* 189 * Execute as a pre-opened file descriptor, which works whether this is 190 * a script or not (because the interpreter sees a filename like 191 * "/dev/fd/20"). 192 */ 193 fd = open(longpath, O_RDONLY); 194 if (fd > 0) { 195 printf("Invoke copy of '%s' via filename of length %zu:\n", 196 src, strlen(longpath)); 197 fail += check_execveat(fd, "", AT_EMPTY_PATH); 198 } else { 199 printf("Failed to open length %zu filename, errno=%d (%s)\n", 200 strlen(longpath), errno, strerror(errno)); 201 fail++; 202 } 203 204 /* 205 * Execute as a long pathname relative to "/". If this is a script, 206 * the interpreter will launch but fail to open the script because its 207 * name ("/dev/fd/5/xxx....") is bigger than PATH_MAX. 208 * 209 * The failure code is usually 127 (POSIX: "If a command is not found, 210 * the exit status shall be 127."), but some systems give 126 (POSIX: 211 * "If the command name is found, but it is not an executable utility, 212 * the exit status shall be 126."), so allow either. 213 */ 214 if (is_script) 215 fail += check_execveat_invoked_rc(root_dfd, longpath + 1, 0, 216 127, 126); 217 else 218 fail += check_execveat(root_dfd, longpath + 1, 0); 219 220 return fail; 221 } 222 223 static int run_tests(void) 224 { 225 int fail = 0; 226 char *fullname = realpath("execveat", NULL); 227 char *fullname_script = realpath("script", NULL); 228 char *fullname_symlink = concat(fullname, ".symlink"); 229 int subdir_dfd = open_or_die("subdir", O_DIRECTORY|O_RDONLY); 230 int subdir_dfd_ephemeral = open_or_die("subdir.ephemeral", 231 O_DIRECTORY|O_RDONLY); 232 int dot_dfd = open_or_die(".", O_DIRECTORY|O_RDONLY); 233 int root_dfd = open_or_die("/", O_DIRECTORY|O_RDONLY); 234 int dot_dfd_path = open_or_die(".", O_DIRECTORY|O_RDONLY|O_PATH); 235 int dot_dfd_cloexec = open_or_die(".", O_DIRECTORY|O_RDONLY|O_CLOEXEC); 236 int fd = open_or_die("execveat", O_RDONLY); 237 int fd_path = open_or_die("execveat", O_RDONLY|O_PATH); 238 int fd_symlink = open_or_die("execveat.symlink", O_RDONLY); 239 int fd_denatured = open_or_die("execveat.denatured", O_RDONLY); 240 int fd_denatured_path = open_or_die("execveat.denatured", 241 O_RDONLY|O_PATH); 242 int fd_script = open_or_die("script", O_RDONLY); 243 int fd_ephemeral = open_or_die("execveat.ephemeral", O_RDONLY); 244 int fd_ephemeral_path = open_or_die("execveat.path.ephemeral", 245 O_RDONLY|O_PATH); 246 int fd_script_ephemeral = open_or_die("script.ephemeral", O_RDONLY); 247 int fd_cloexec = open_or_die("execveat", O_RDONLY|O_CLOEXEC); 248 int fd_script_cloexec = open_or_die("script", O_RDONLY|O_CLOEXEC); 249 250 /* Check if we have execveat at all, and bail early if not */ 251 errno = 0; 252 execveat_(-1, NULL, NULL, NULL, 0); 253 if (errno == ENOSYS) { 254 ksft_exit_skip( 255 "ENOSYS calling execveat - no kernel support?\n"); 256 } 257 258 /* Change file position to confirm it doesn't affect anything */ 259 lseek(fd, 10, SEEK_SET); 260 261 /* Normal executable file: */ 262 /* dfd + path */ 263 fail += check_execveat(subdir_dfd, "../execveat", 0); 264 fail += check_execveat(dot_dfd, "execveat", 0); 265 fail += check_execveat(dot_dfd_path, "execveat", 0); 266 /* absolute path */ 267 fail += check_execveat(AT_FDCWD, fullname, 0); 268 /* absolute path with nonsense dfd */ 269 fail += check_execveat(99, fullname, 0); 270 /* fd + no path */ 271 fail += check_execveat(fd, "", AT_EMPTY_PATH); 272 /* O_CLOEXEC fd + no path */ 273 fail += check_execveat(fd_cloexec, "", AT_EMPTY_PATH); 274 /* O_PATH fd */ 275 fail += check_execveat(fd_path, "", AT_EMPTY_PATH); 276 277 /* Mess with executable file that's already open: */ 278 /* fd + no path to a file that's been renamed */ 279 rename("execveat.ephemeral", "execveat.moved"); 280 fail += check_execveat(fd_ephemeral, "", AT_EMPTY_PATH); 281 /* fd + no path to a file that's been deleted */ 282 unlink("execveat.moved"); /* remove the file now fd open */ 283 fail += check_execveat(fd_ephemeral, "", AT_EMPTY_PATH); 284 285 /* Mess with executable file that's already open with O_PATH */ 286 /* fd + no path to a file that's been deleted */ 287 unlink("execveat.path.ephemeral"); 288 fail += check_execveat(fd_ephemeral_path, "", AT_EMPTY_PATH); 289 290 /* Invalid argument failures */ 291 fail += check_execveat_fail(fd, "", 0, ENOENT); 292 fail += check_execveat_fail(fd, NULL, AT_EMPTY_PATH, EFAULT); 293 294 /* Symlink to executable file: */ 295 /* dfd + path */ 296 fail += check_execveat(dot_dfd, "execveat.symlink", 0); 297 fail += check_execveat(dot_dfd_path, "execveat.symlink", 0); 298 /* absolute path */ 299 fail += check_execveat(AT_FDCWD, fullname_symlink, 0); 300 /* fd + no path, even with AT_SYMLINK_NOFOLLOW (already followed) */ 301 fail += check_execveat(fd_symlink, "", AT_EMPTY_PATH); 302 fail += check_execveat(fd_symlink, "", 303 AT_EMPTY_PATH|AT_SYMLINK_NOFOLLOW); 304 305 /* Symlink fails when AT_SYMLINK_NOFOLLOW set: */ 306 /* dfd + path */ 307 fail += check_execveat_fail(dot_dfd, "execveat.symlink", 308 AT_SYMLINK_NOFOLLOW, ELOOP); 309 fail += check_execveat_fail(dot_dfd_path, "execveat.symlink", 310 AT_SYMLINK_NOFOLLOW, ELOOP); 311 /* absolute path */ 312 fail += check_execveat_fail(AT_FDCWD, fullname_symlink, 313 AT_SYMLINK_NOFOLLOW, ELOOP); 314 315 /* Shell script wrapping executable file: */ 316 /* dfd + path */ 317 fail += check_execveat(subdir_dfd, "../script", 0); 318 fail += check_execveat(dot_dfd, "script", 0); 319 fail += check_execveat(dot_dfd_path, "script", 0); 320 /* absolute path */ 321 fail += check_execveat(AT_FDCWD, fullname_script, 0); 322 /* fd + no path */ 323 fail += check_execveat(fd_script, "", AT_EMPTY_PATH); 324 fail += check_execveat(fd_script, "", 325 AT_EMPTY_PATH|AT_SYMLINK_NOFOLLOW); 326 /* O_CLOEXEC fd fails for a script (as script file inaccessible) */ 327 fail += check_execveat_fail(fd_script_cloexec, "", AT_EMPTY_PATH, 328 ENOENT); 329 fail += check_execveat_fail(dot_dfd_cloexec, "script", 0, ENOENT); 330 331 /* Mess with script file that's already open: */ 332 /* fd + no path to a file that's been renamed */ 333 rename("script.ephemeral", "script.moved"); 334 fail += check_execveat(fd_script_ephemeral, "", AT_EMPTY_PATH); 335 /* fd + no path to a file that's been deleted */ 336 unlink("script.moved"); /* remove the file while fd open */ 337 fail += check_execveat(fd_script_ephemeral, "", AT_EMPTY_PATH); 338 339 /* Rename a subdirectory in the path: */ 340 rename("subdir.ephemeral", "subdir.moved"); 341 fail += check_execveat(subdir_dfd_ephemeral, "../script", 0); 342 fail += check_execveat(subdir_dfd_ephemeral, "script", 0); 343 /* Remove the subdir and its contents */ 344 unlink("subdir.moved/script"); 345 unlink("subdir.moved"); 346 /* Shell loads via deleted subdir OK because name starts with .. */ 347 fail += check_execveat(subdir_dfd_ephemeral, "../script", 0); 348 fail += check_execveat_fail(subdir_dfd_ephemeral, "script", 0, ENOENT); 349 350 /* Flag values other than AT_SYMLINK_NOFOLLOW => EINVAL */ 351 fail += check_execveat_fail(dot_dfd, "execveat", 0xFFFF, EINVAL); 352 /* Invalid path => ENOENT */ 353 fail += check_execveat_fail(dot_dfd, "no-such-file", 0, ENOENT); 354 fail += check_execveat_fail(dot_dfd_path, "no-such-file", 0, ENOENT); 355 fail += check_execveat_fail(AT_FDCWD, "no-such-file", 0, ENOENT); 356 /* Attempt to execute directory => EACCES */ 357 fail += check_execveat_fail(dot_dfd, "", AT_EMPTY_PATH, EACCES); 358 /* Attempt to execute non-executable => EACCES */ 359 fail += check_execveat_fail(dot_dfd, "Makefile", 0, EACCES); 360 fail += check_execveat_fail(fd_denatured, "", AT_EMPTY_PATH, EACCES); 361 fail += check_execveat_fail(fd_denatured_path, "", AT_EMPTY_PATH, 362 EACCES); 363 /* Attempt to execute nonsense FD => EBADF */ 364 fail += check_execveat_fail(99, "", AT_EMPTY_PATH, EBADF); 365 fail += check_execveat_fail(99, "execveat", 0, EBADF); 366 /* Attempt to execute relative to non-directory => ENOTDIR */ 367 fail += check_execveat_fail(fd, "execveat", 0, ENOTDIR); 368 369 fail += check_execveat_pathmax(root_dfd, "execveat", 0); 370 fail += check_execveat_pathmax(root_dfd, "script", 1); 371 return fail; 372 } 373 374 static void prerequisites(void) 375 { 376 int fd; 377 const char *script = "#!/bin/sh\nexit $*\n"; 378 379 /* Create ephemeral copies of files */ 380 exe_cp("execveat", "execveat.ephemeral"); 381 exe_cp("execveat", "execveat.path.ephemeral"); 382 exe_cp("script", "script.ephemeral"); 383 mkdir("subdir.ephemeral", 0755); 384 385 fd = open("subdir.ephemeral/script", O_RDWR|O_CREAT|O_TRUNC, 0755); 386 write(fd, script, strlen(script)); 387 close(fd); 388 } 389 390 int main(int argc, char **argv) 391 { 392 int ii; 393 int rc; 394 const char *verbose = getenv("VERBOSE"); 395 396 if (argc >= 2) { 397 /* If we are invoked with an argument, don't run tests. */ 398 const char *in_test = getenv("IN_TEST"); 399 400 if (verbose) { 401 printf(" invoked with:"); 402 for (ii = 0; ii < argc; ii++) 403 printf(" [%d]='%s'", ii, argv[ii]); 404 printf("\n"); 405 } 406 407 /* Check expected environment transferred. */ 408 if (!in_test || strcmp(in_test, "yes") != 0) { 409 printf("[FAIL] (no IN_TEST=yes in env)\n"); 410 return 1; 411 } 412 413 /* Use the final argument as an exit code. */ 414 rc = atoi(argv[argc - 1]); 415 fflush(stdout); 416 } else { 417 prerequisites(); 418 if (verbose) 419 envp[1] = "VERBOSE=1"; 420 rc = run_tests(); 421 if (rc > 0) 422 printf("%d tests failed\n", rc); 423 } 424 return rc; 425 } 426