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
23static char longpath[2 * PATH_MAX] = "";
24static char *envp[] = { "IN_TEST=yes", NULL, NULL };
25static char *argv[] = { "execveat", "99", NULL };
26
27static 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)
40static 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
64static 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
111static int check_execveat(int fd, const char *path, int flags)
112{
113	return check_execveat_invoked_rc(fd, path, flags, 99, 99);
114}
115
116static 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
125static 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
137static 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
150static 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
211static 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
361static 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
377int 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