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)
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 		printf("[FAIL] (child %d exited with %d not %d)\n",
103 			child, WEXITSTATUS(status), expected_rc);
104 		return 1;
105 	}
106 	printf("[OK]\n");
107 	return 0;
108 }
109 
110 static int check_execveat(int fd, const char *path, int flags)
111 {
112 	return check_execveat_invoked_rc(fd, path, flags, 99);
113 }
114 
115 static char *concat(const char *left, const char *right)
116 {
117 	char *result = malloc(strlen(left) + strlen(right) + 1);
118 
119 	strcpy(result, left);
120 	strcat(result, right);
121 	return result;
122 }
123 
124 static int open_or_die(const char *filename, int flags)
125 {
126 	int fd = open(filename, flags);
127 
128 	if (fd < 0) {
129 		printf("Failed to open '%s'; "
130 			"check prerequisites are available\n", filename);
131 		exit(1);
132 	}
133 	return fd;
134 }
135 
136 static void exe_cp(const char *src, const char *dest)
137 {
138 	int in_fd = open_or_die(src, O_RDONLY);
139 	int out_fd = open(dest, O_RDWR|O_CREAT|O_TRUNC, 0755);
140 	struct stat info;
141 
142 	fstat(in_fd, &info);
143 	sendfile(out_fd, in_fd, NULL, info.st_size);
144 	close(in_fd);
145 	close(out_fd);
146 }
147 
148 #define XX_DIR_LEN 200
149 static int check_execveat_pathmax(int dot_dfd, const char *src, int is_script)
150 {
151 	int fail = 0;
152 	int ii, count, len;
153 	char longname[XX_DIR_LEN + 1];
154 	int fd;
155 
156 	if (*longpath == '\0') {
157 		/* Create a filename close to PATH_MAX in length */
158 		memset(longname, 'x', XX_DIR_LEN - 1);
159 		longname[XX_DIR_LEN - 1] = '/';
160 		longname[XX_DIR_LEN] = '\0';
161 		count = (PATH_MAX - 3) / XX_DIR_LEN;
162 		for (ii = 0; ii < count; ii++) {
163 			strcat(longpath, longname);
164 			mkdir(longpath, 0755);
165 		}
166 		len = (PATH_MAX - 3) - (count * XX_DIR_LEN);
167 		if (len <= 0)
168 			len = 1;
169 		memset(longname, 'y', len);
170 		longname[len] = '\0';
171 		strcat(longpath, longname);
172 	}
173 	exe_cp(src, longpath);
174 
175 	/*
176 	 * Execute as a pre-opened file descriptor, which works whether this is
177 	 * a script or not (because the interpreter sees a filename like
178 	 * "/dev/fd/20").
179 	 */
180 	fd = open(longpath, O_RDONLY);
181 	if (fd > 0) {
182 		printf("Invoke copy of '%s' via filename of length %lu:\n",
183 			src, strlen(longpath));
184 		fail += check_execveat(fd, "", AT_EMPTY_PATH);
185 	} else {
186 		printf("Failed to open length %lu filename, errno=%d (%s)\n",
187 			strlen(longpath), errno, strerror(errno));
188 		fail++;
189 	}
190 
191 	/*
192 	 * Execute as a long pathname relative to ".".  If this is a script,
193 	 * the interpreter will launch but fail to open the script because its
194 	 * name ("/dev/fd/5/xxx....") is bigger than PATH_MAX.
195 	 */
196 	if (is_script)
197 		fail += check_execveat_invoked_rc(dot_dfd, longpath, 0, 127);
198 	else
199 		fail += check_execveat(dot_dfd, longpath, 0);
200 
201 	return fail;
202 }
203 
204 static int run_tests(void)
205 {
206 	int fail = 0;
207 	char *fullname = realpath("execveat", NULL);
208 	char *fullname_script = realpath("script", NULL);
209 	char *fullname_symlink = concat(fullname, ".symlink");
210 	int subdir_dfd = open_or_die("subdir", O_DIRECTORY|O_RDONLY);
211 	int subdir_dfd_ephemeral = open_or_die("subdir.ephemeral",
212 					       O_DIRECTORY|O_RDONLY);
213 	int dot_dfd = open_or_die(".", O_DIRECTORY|O_RDONLY);
214 	int dot_dfd_path = open_or_die(".", O_DIRECTORY|O_RDONLY|O_PATH);
215 	int dot_dfd_cloexec = open_or_die(".", O_DIRECTORY|O_RDONLY|O_CLOEXEC);
216 	int fd = open_or_die("execveat", O_RDONLY);
217 	int fd_path = open_or_die("execveat", O_RDONLY|O_PATH);
218 	int fd_symlink = open_or_die("execveat.symlink", O_RDONLY);
219 	int fd_denatured = open_or_die("execveat.denatured", O_RDONLY);
220 	int fd_denatured_path = open_or_die("execveat.denatured",
221 					    O_RDONLY|O_PATH);
222 	int fd_script = open_or_die("script", O_RDONLY);
223 	int fd_ephemeral = open_or_die("execveat.ephemeral", O_RDONLY);
224 	int fd_ephemeral_path = open_or_die("execveat.path.ephemeral",
225 					    O_RDONLY|O_PATH);
226 	int fd_script_ephemeral = open_or_die("script.ephemeral", O_RDONLY);
227 	int fd_cloexec = open_or_die("execveat", O_RDONLY|O_CLOEXEC);
228 	int fd_script_cloexec = open_or_die("script", O_RDONLY|O_CLOEXEC);
229 
230 	/* Change file position to confirm it doesn't affect anything */
231 	lseek(fd, 10, SEEK_SET);
232 
233 	/* Normal executable file: */
234 	/*   dfd + path */
235 	fail += check_execveat(subdir_dfd, "../execveat", 0);
236 	fail += check_execveat(dot_dfd, "execveat", 0);
237 	fail += check_execveat(dot_dfd_path, "execveat", 0);
238 	/*   absolute path */
239 	fail += check_execveat(AT_FDCWD, fullname, 0);
240 	/*   absolute path with nonsense dfd */
241 	fail += check_execveat(99, fullname, 0);
242 	/*   fd + no path */
243 	fail += check_execveat(fd, "", AT_EMPTY_PATH);
244 	/*   O_CLOEXEC fd + no path */
245 	fail += check_execveat(fd_cloexec, "", AT_EMPTY_PATH);
246 	/*   O_PATH fd */
247 	fail += check_execveat(fd_path, "", AT_EMPTY_PATH);
248 
249 	/* Mess with executable file that's already open: */
250 	/*   fd + no path to a file that's been renamed */
251 	rename("execveat.ephemeral", "execveat.moved");
252 	fail += check_execveat(fd_ephemeral, "", AT_EMPTY_PATH);
253 	/*   fd + no path to a file that's been deleted */
254 	unlink("execveat.moved"); /* remove the file now fd open */
255 	fail += check_execveat(fd_ephemeral, "", AT_EMPTY_PATH);
256 
257 	/* Mess with executable file that's already open with O_PATH */
258 	/*   fd + no path to a file that's been deleted */
259 	unlink("execveat.path.ephemeral");
260 	fail += check_execveat(fd_ephemeral_path, "", AT_EMPTY_PATH);
261 
262 	/* Invalid argument failures */
263 	fail += check_execveat_fail(fd, "", 0, ENOENT);
264 	fail += check_execveat_fail(fd, NULL, AT_EMPTY_PATH, EFAULT);
265 
266 	/* Symlink to executable file: */
267 	/*   dfd + path */
268 	fail += check_execveat(dot_dfd, "execveat.symlink", 0);
269 	fail += check_execveat(dot_dfd_path, "execveat.symlink", 0);
270 	/*   absolute path */
271 	fail += check_execveat(AT_FDCWD, fullname_symlink, 0);
272 	/*   fd + no path, even with AT_SYMLINK_NOFOLLOW (already followed) */
273 	fail += check_execveat(fd_symlink, "", AT_EMPTY_PATH);
274 	fail += check_execveat(fd_symlink, "",
275 			       AT_EMPTY_PATH|AT_SYMLINK_NOFOLLOW);
276 
277 	/* Symlink fails when AT_SYMLINK_NOFOLLOW set: */
278 	/*   dfd + path */
279 	fail += check_execveat_fail(dot_dfd, "execveat.symlink",
280 				    AT_SYMLINK_NOFOLLOW, ELOOP);
281 	fail += check_execveat_fail(dot_dfd_path, "execveat.symlink",
282 				    AT_SYMLINK_NOFOLLOW, ELOOP);
283 	/*   absolute path */
284 	fail += check_execveat_fail(AT_FDCWD, fullname_symlink,
285 				    AT_SYMLINK_NOFOLLOW, ELOOP);
286 
287 	/* Shell script wrapping executable file: */
288 	/*   dfd + path */
289 	fail += check_execveat(subdir_dfd, "../script", 0);
290 	fail += check_execveat(dot_dfd, "script", 0);
291 	fail += check_execveat(dot_dfd_path, "script", 0);
292 	/*   absolute path */
293 	fail += check_execveat(AT_FDCWD, fullname_script, 0);
294 	/*   fd + no path */
295 	fail += check_execveat(fd_script, "", AT_EMPTY_PATH);
296 	fail += check_execveat(fd_script, "",
297 			       AT_EMPTY_PATH|AT_SYMLINK_NOFOLLOW);
298 	/*   O_CLOEXEC fd fails for a script (as script file inaccessible) */
299 	fail += check_execveat_fail(fd_script_cloexec, "", AT_EMPTY_PATH,
300 				    ENOENT);
301 	fail += check_execveat_fail(dot_dfd_cloexec, "script", 0, ENOENT);
302 
303 	/* Mess with script file that's already open: */
304 	/*   fd + no path to a file that's been renamed */
305 	rename("script.ephemeral", "script.moved");
306 	fail += check_execveat(fd_script_ephemeral, "", AT_EMPTY_PATH);
307 	/*   fd + no path to a file that's been deleted */
308 	unlink("script.moved"); /* remove the file while fd open */
309 	fail += check_execveat(fd_script_ephemeral, "", AT_EMPTY_PATH);
310 
311 	/* Rename a subdirectory in the path: */
312 	rename("subdir.ephemeral", "subdir.moved");
313 	fail += check_execveat(subdir_dfd_ephemeral, "../script", 0);
314 	fail += check_execveat(subdir_dfd_ephemeral, "script", 0);
315 	/* Remove the subdir and its contents */
316 	unlink("subdir.moved/script");
317 	unlink("subdir.moved");
318 	/* Shell loads via deleted subdir OK because name starts with .. */
319 	fail += check_execveat(subdir_dfd_ephemeral, "../script", 0);
320 	fail += check_execveat_fail(subdir_dfd_ephemeral, "script", 0, ENOENT);
321 
322 	/* Flag values other than AT_SYMLINK_NOFOLLOW => EINVAL */
323 	fail += check_execveat_fail(dot_dfd, "execveat", 0xFFFF, EINVAL);
324 	/* Invalid path => ENOENT */
325 	fail += check_execveat_fail(dot_dfd, "no-such-file", 0, ENOENT);
326 	fail += check_execveat_fail(dot_dfd_path, "no-such-file", 0, ENOENT);
327 	fail += check_execveat_fail(AT_FDCWD, "no-such-file", 0, ENOENT);
328 	/* Attempt to execute directory => EACCES */
329 	fail += check_execveat_fail(dot_dfd, "", AT_EMPTY_PATH, EACCES);
330 	/* Attempt to execute non-executable => EACCES */
331 	fail += check_execveat_fail(dot_dfd, "Makefile", 0, EACCES);
332 	fail += check_execveat_fail(fd_denatured, "", AT_EMPTY_PATH, EACCES);
333 	fail += check_execveat_fail(fd_denatured_path, "", AT_EMPTY_PATH,
334 				    EACCES);
335 	/* Attempt to execute nonsense FD => EBADF */
336 	fail += check_execveat_fail(99, "", AT_EMPTY_PATH, EBADF);
337 	fail += check_execveat_fail(99, "execveat", 0, EBADF);
338 	/* Attempt to execute relative to non-directory => ENOTDIR */
339 	fail += check_execveat_fail(fd, "execveat", 0, ENOTDIR);
340 
341 	fail += check_execveat_pathmax(dot_dfd, "execveat", 0);
342 	fail += check_execveat_pathmax(dot_dfd, "script", 1);
343 	return fail;
344 }
345 
346 static void prerequisites(void)
347 {
348 	int fd;
349 	const char *script = "#!/bin/sh\nexit $*\n";
350 
351 	/* Create ephemeral copies of files */
352 	exe_cp("execveat", "execveat.ephemeral");
353 	exe_cp("execveat", "execveat.path.ephemeral");
354 	exe_cp("script", "script.ephemeral");
355 	mkdir("subdir.ephemeral", 0755);
356 
357 	fd = open("subdir.ephemeral/script", O_RDWR|O_CREAT|O_TRUNC, 0755);
358 	write(fd, script, strlen(script));
359 	close(fd);
360 }
361 
362 int main(int argc, char **argv)
363 {
364 	int ii;
365 	int rc;
366 	const char *verbose = getenv("VERBOSE");
367 
368 	if (argc >= 2) {
369 		/* If we are invoked with an argument, don't run tests. */
370 		const char *in_test = getenv("IN_TEST");
371 
372 		if (verbose) {
373 			printf("  invoked with:");
374 			for (ii = 0; ii < argc; ii++)
375 				printf(" [%d]='%s'", ii, argv[ii]);
376 			printf("\n");
377 		}
378 
379 		/* Check expected environment transferred. */
380 		if (!in_test || strcmp(in_test, "yes") != 0) {
381 			printf("[FAIL] (no IN_TEST=yes in env)\n");
382 			return 1;
383 		}
384 
385 		/* Use the final argument as an exit code. */
386 		rc = atoi(argv[argc - 1]);
387 		fflush(stdout);
388 	} else {
389 		prerequisites();
390 		if (verbose)
391 			envp[1] = "VERBOSE=1";
392 		rc = run_tests();
393 		if (rc > 0)
394 			printf("%d tests failed\n", rc);
395 	}
396 	return rc;
397 }
398