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 /* Change file position to confirm it doesn't affect anything */ 238 lseek(fd, 10, SEEK_SET); 239 240 /* Normal executable file: */ 241 /* dfd + path */ 242 fail += check_execveat(subdir_dfd, "../execveat", 0); 243 fail += check_execveat(dot_dfd, "execveat", 0); 244 fail += check_execveat(dot_dfd_path, "execveat", 0); 245 /* absolute path */ 246 fail += check_execveat(AT_FDCWD, fullname, 0); 247 /* absolute path with nonsense dfd */ 248 fail += check_execveat(99, fullname, 0); 249 /* fd + no path */ 250 fail += check_execveat(fd, "", AT_EMPTY_PATH); 251 /* O_CLOEXEC fd + no path */ 252 fail += check_execveat(fd_cloexec, "", AT_EMPTY_PATH); 253 /* O_PATH fd */ 254 fail += check_execveat(fd_path, "", AT_EMPTY_PATH); 255 256 /* Mess with executable file that's already open: */ 257 /* fd + no path to a file that's been renamed */ 258 rename("execveat.ephemeral", "execveat.moved"); 259 fail += check_execveat(fd_ephemeral, "", AT_EMPTY_PATH); 260 /* fd + no path to a file that's been deleted */ 261 unlink("execveat.moved"); /* remove the file now fd open */ 262 fail += check_execveat(fd_ephemeral, "", AT_EMPTY_PATH); 263 264 /* Mess with executable file that's already open with O_PATH */ 265 /* fd + no path to a file that's been deleted */ 266 unlink("execveat.path.ephemeral"); 267 fail += check_execveat(fd_ephemeral_path, "", AT_EMPTY_PATH); 268 269 /* Invalid argument failures */ 270 fail += check_execveat_fail(fd, "", 0, ENOENT); 271 fail += check_execveat_fail(fd, NULL, AT_EMPTY_PATH, EFAULT); 272 273 /* Symlink to executable file: */ 274 /* dfd + path */ 275 fail += check_execveat(dot_dfd, "execveat.symlink", 0); 276 fail += check_execveat(dot_dfd_path, "execveat.symlink", 0); 277 /* absolute path */ 278 fail += check_execveat(AT_FDCWD, fullname_symlink, 0); 279 /* fd + no path, even with AT_SYMLINK_NOFOLLOW (already followed) */ 280 fail += check_execveat(fd_symlink, "", AT_EMPTY_PATH); 281 fail += check_execveat(fd_symlink, "", 282 AT_EMPTY_PATH|AT_SYMLINK_NOFOLLOW); 283 284 /* Symlink fails when AT_SYMLINK_NOFOLLOW set: */ 285 /* dfd + path */ 286 fail += check_execveat_fail(dot_dfd, "execveat.symlink", 287 AT_SYMLINK_NOFOLLOW, ELOOP); 288 fail += check_execveat_fail(dot_dfd_path, "execveat.symlink", 289 AT_SYMLINK_NOFOLLOW, ELOOP); 290 /* absolute path */ 291 fail += check_execveat_fail(AT_FDCWD, fullname_symlink, 292 AT_SYMLINK_NOFOLLOW, ELOOP); 293 294 /* Shell script wrapping executable file: */ 295 /* dfd + path */ 296 fail += check_execveat(subdir_dfd, "../script", 0); 297 fail += check_execveat(dot_dfd, "script", 0); 298 fail += check_execveat(dot_dfd_path, "script", 0); 299 /* absolute path */ 300 fail += check_execveat(AT_FDCWD, fullname_script, 0); 301 /* fd + no path */ 302 fail += check_execveat(fd_script, "", AT_EMPTY_PATH); 303 fail += check_execveat(fd_script, "", 304 AT_EMPTY_PATH|AT_SYMLINK_NOFOLLOW); 305 /* O_CLOEXEC fd fails for a script (as script file inaccessible) */ 306 fail += check_execveat_fail(fd_script_cloexec, "", AT_EMPTY_PATH, 307 ENOENT); 308 fail += check_execveat_fail(dot_dfd_cloexec, "script", 0, ENOENT); 309 310 /* Mess with script file that's already open: */ 311 /* fd + no path to a file that's been renamed */ 312 rename("script.ephemeral", "script.moved"); 313 fail += check_execveat(fd_script_ephemeral, "", AT_EMPTY_PATH); 314 /* fd + no path to a file that's been deleted */ 315 unlink("script.moved"); /* remove the file while fd open */ 316 fail += check_execveat(fd_script_ephemeral, "", AT_EMPTY_PATH); 317 318 /* Rename a subdirectory in the path: */ 319 rename("subdir.ephemeral", "subdir.moved"); 320 fail += check_execveat(subdir_dfd_ephemeral, "../script", 0); 321 fail += check_execveat(subdir_dfd_ephemeral, "script", 0); 322 /* Remove the subdir and its contents */ 323 unlink("subdir.moved/script"); 324 unlink("subdir.moved"); 325 /* Shell loads via deleted subdir OK because name starts with .. */ 326 fail += check_execveat(subdir_dfd_ephemeral, "../script", 0); 327 fail += check_execveat_fail(subdir_dfd_ephemeral, "script", 0, ENOENT); 328 329 /* Flag values other than AT_SYMLINK_NOFOLLOW => EINVAL */ 330 fail += check_execveat_fail(dot_dfd, "execveat", 0xFFFF, EINVAL); 331 /* Invalid path => ENOENT */ 332 fail += check_execveat_fail(dot_dfd, "no-such-file", 0, ENOENT); 333 fail += check_execveat_fail(dot_dfd_path, "no-such-file", 0, ENOENT); 334 fail += check_execveat_fail(AT_FDCWD, "no-such-file", 0, ENOENT); 335 /* Attempt to execute directory => EACCES */ 336 fail += check_execveat_fail(dot_dfd, "", AT_EMPTY_PATH, EACCES); 337 /* Attempt to execute non-executable => EACCES */ 338 fail += check_execveat_fail(dot_dfd, "Makefile", 0, EACCES); 339 fail += check_execveat_fail(fd_denatured, "", AT_EMPTY_PATH, EACCES); 340 fail += check_execveat_fail(fd_denatured_path, "", AT_EMPTY_PATH, 341 EACCES); 342 /* Attempt to execute nonsense FD => EBADF */ 343 fail += check_execveat_fail(99, "", AT_EMPTY_PATH, EBADF); 344 fail += check_execveat_fail(99, "execveat", 0, EBADF); 345 /* Attempt to execute relative to non-directory => ENOTDIR */ 346 fail += check_execveat_fail(fd, "execveat", 0, ENOTDIR); 347 348 fail += check_execveat_pathmax(dot_dfd, "execveat", 0); 349 fail += check_execveat_pathmax(dot_dfd, "script", 1); 350 return fail; 351 } 352 353 static void prerequisites(void) 354 { 355 int fd; 356 const char *script = "#!/bin/sh\nexit $*\n"; 357 358 /* Create ephemeral copies of files */ 359 exe_cp("execveat", "execveat.ephemeral"); 360 exe_cp("execveat", "execveat.path.ephemeral"); 361 exe_cp("script", "script.ephemeral"); 362 mkdir("subdir.ephemeral", 0755); 363 364 fd = open("subdir.ephemeral/script", O_RDWR|O_CREAT|O_TRUNC, 0755); 365 write(fd, script, strlen(script)); 366 close(fd); 367 } 368 369 int main(int argc, char **argv) 370 { 371 int ii; 372 int rc; 373 const char *verbose = getenv("VERBOSE"); 374 375 if (argc >= 2) { 376 /* If we are invoked with an argument, don't run tests. */ 377 const char *in_test = getenv("IN_TEST"); 378 379 if (verbose) { 380 printf(" invoked with:"); 381 for (ii = 0; ii < argc; ii++) 382 printf(" [%d]='%s'", ii, argv[ii]); 383 printf("\n"); 384 } 385 386 /* Check expected environment transferred. */ 387 if (!in_test || strcmp(in_test, "yes") != 0) { 388 printf("[FAIL] (no IN_TEST=yes in env)\n"); 389 return 1; 390 } 391 392 /* Use the final argument as an exit code. */ 393 rc = atoi(argv[argc - 1]); 394 fflush(stdout); 395 } else { 396 prerequisites(); 397 if (verbose) 398 envp[1] = "VERBOSE=1"; 399 rc = run_tests(); 400 if (rc > 0) 401 printf("%d tests failed\n", rc); 402 } 403 return rc; 404 } 405