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
execveat_(int fd,const char * path,char ** argv,char ** envp,int flags)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)
_check_execveat_fail(int fd,const char * path,int flags,int expected_errno,const char * errno_str)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
check_execveat_invoked_rc(int fd,const char * path,int flags,int expected_rc,int expected_rc2)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
check_execveat(int fd,const char * path,int flags)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
concat(const char * left,const char * right)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
open_or_die(const char * filename,int flags)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
exe_cp(const char * src,const char * dest)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
check_execveat_pathmax(int dot_dfd,const char * src,int is_script)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
run_tests(void)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
prerequisites(void)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
main(int argc,char ** argv)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 }
413