1 // SPDX-License-Identifier: GPL-2.0
2 #define _GNU_SOURCE
3 
4 #include <cap-ng.h>
5 #include <linux/capability.h>
6 #include <stdbool.h>
7 #include <string.h>
8 #include <stdio.h>
9 #include <fcntl.h>
10 #include <errno.h>
11 #include <stdarg.h>
12 #include <sched.h>
13 #include <sys/mount.h>
14 #include <limits.h>
15 #include <libgen.h>
16 #include <malloc.h>
17 #include <sys/wait.h>
18 #include <sys/prctl.h>
19 #include <sys/stat.h>
20 
21 #include "../kselftest.h"
22 
23 #ifndef PR_CAP_AMBIENT
24 #define PR_CAP_AMBIENT			47
25 # define PR_CAP_AMBIENT_IS_SET		1
26 # define PR_CAP_AMBIENT_RAISE		2
27 # define PR_CAP_AMBIENT_LOWER		3
28 # define PR_CAP_AMBIENT_CLEAR_ALL	4
29 #endif
30 
31 static int nerrs;
32 static pid_t mpid;	/*  main() pid is used to avoid duplicate test counts */
33 
34 static void vmaybe_write_file(bool enoent_ok, char *filename, char *fmt, va_list ap)
35 {
36 	char buf[4096];
37 	int fd;
38 	ssize_t written;
39 	int buf_len;
40 
41 	buf_len = vsnprintf(buf, sizeof(buf), fmt, ap);
42 	if (buf_len < 0)
43 		ksft_exit_fail_msg("vsnprintf failed - %s\n", strerror(errno));
44 
45 	if (buf_len >= sizeof(buf))
46 		ksft_exit_fail_msg("vsnprintf output truncated\n");
47 
48 
49 	fd = open(filename, O_WRONLY);
50 	if (fd < 0) {
51 		if ((errno == ENOENT) && enoent_ok)
52 			return;
53 		ksft_exit_fail_msg("open of %s failed - %s\n",
54 					filename, strerror(errno));
55 	}
56 	written = write(fd, buf, buf_len);
57 	if (written != buf_len) {
58 		if (written >= 0) {
59 			ksft_exit_fail_msg("short write to %s\n", filename);
60 		} else {
61 			ksft_exit_fail_msg("write to %s failed - %s\n",
62 						filename, strerror(errno));
63 		}
64 	}
65 	if (close(fd) != 0) {
66 		ksft_exit_fail_msg("close of %s failed - %s\n",
67 					filename, strerror(errno));
68 	}
69 }
70 
71 static void maybe_write_file(char *filename, char *fmt, ...)
72 {
73 	va_list ap;
74 
75 	va_start(ap, fmt);
76 	vmaybe_write_file(true, filename, fmt, ap);
77 	va_end(ap);
78 }
79 
80 static void write_file(char *filename, char *fmt, ...)
81 {
82 	va_list ap;
83 
84 	va_start(ap, fmt);
85 	vmaybe_write_file(false, filename, fmt, ap);
86 	va_end(ap);
87 }
88 
89 static bool create_and_enter_ns(uid_t inner_uid)
90 {
91 	uid_t outer_uid;
92 	gid_t outer_gid;
93 	int i;
94 	bool have_outer_privilege;
95 
96 	outer_uid = getuid();
97 	outer_gid = getgid();
98 
99 	/*
100 	 * TODO: If we're already root, we could skip creating the userns.
101 	 */
102 
103 	if (unshare(CLONE_NEWNS) == 0) {
104 		ksft_print_msg("[NOTE]\tUsing global UIDs for tests\n");
105 		if (prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0) != 0)
106 			ksft_exit_fail_msg("PR_SET_KEEPCAPS - %s\n",
107 						strerror(errno));
108 		if (setresuid(inner_uid, inner_uid, -1) != 0)
109 			ksft_exit_fail_msg("setresuid - %s\n", strerror(errno));
110 
111 		// Re-enable effective caps
112 		capng_get_caps_process();
113 		for (i = 0; i < CAP_LAST_CAP; i++)
114 			if (capng_have_capability(CAPNG_PERMITTED, i))
115 				capng_update(CAPNG_ADD, CAPNG_EFFECTIVE, i);
116 		if (capng_apply(CAPNG_SELECT_CAPS) != 0)
117 			ksft_exit_fail_msg(
118 					"capng_apply - %s\n", strerror(errno));
119 
120 		have_outer_privilege = true;
121 	} else if (unshare(CLONE_NEWUSER | CLONE_NEWNS) == 0) {
122 		ksft_print_msg("[NOTE]\tUsing a user namespace for tests\n");
123 		maybe_write_file("/proc/self/setgroups", "deny");
124 		write_file("/proc/self/uid_map", "%d %d 1", inner_uid, outer_uid);
125 		write_file("/proc/self/gid_map", "0 %d 1", outer_gid);
126 
127 		have_outer_privilege = false;
128 	} else {
129 		ksft_exit_skip("must be root or be able to create a userns\n");
130 	}
131 
132 	if (mount("none", "/", NULL, MS_REC | MS_PRIVATE, NULL) != 0)
133 		ksft_exit_fail_msg("remount everything private - %s\n",
134 					strerror(errno));
135 
136 	return have_outer_privilege;
137 }
138 
139 static void chdir_to_tmpfs(void)
140 {
141 	char cwd[PATH_MAX];
142 	if (getcwd(cwd, sizeof(cwd)) != cwd)
143 		ksft_exit_fail_msg("getcwd - %s\n", strerror(errno));
144 
145 	if (mount("private_tmp", ".", "tmpfs", 0, "mode=0777") != 0)
146 		ksft_exit_fail_msg("mount private tmpfs - %s\n",
147 					strerror(errno));
148 
149 	if (chdir(cwd) != 0)
150 		ksft_exit_fail_msg("chdir to private tmpfs - %s\n",
151 					strerror(errno));
152 }
153 
154 static void copy_fromat_to(int fromfd, const char *fromname, const char *toname)
155 {
156 	int from = openat(fromfd, fromname, O_RDONLY);
157 	if (from == -1)
158 		ksft_exit_fail_msg("open copy source - %s\n", strerror(errno));
159 
160 	int to = open(toname, O_CREAT | O_WRONLY | O_EXCL, 0700);
161 
162 	while (true) {
163 		char buf[4096];
164 		ssize_t sz = read(from, buf, sizeof(buf));
165 		if (sz == 0)
166 			break;
167 		if (sz < 0)
168 			ksft_exit_fail_msg("read - %s\n", strerror(errno));
169 
170 		if (write(to, buf, sz) != sz)
171 			/* no short writes on tmpfs */
172 			ksft_exit_fail_msg("write - %s\n", strerror(errno));
173 	}
174 
175 	close(from);
176 	close(to);
177 }
178 
179 static bool fork_wait(void)
180 {
181 	pid_t child = fork();
182 	if (child == 0) {
183 		nerrs = 0;
184 		return true;
185 	} else if (child > 0) {
186 		int status;
187 		if (waitpid(child, &status, 0) != child ||
188 		    !WIFEXITED(status)) {
189 			ksft_print_msg("Child died\n");
190 			nerrs++;
191 		} else if (WEXITSTATUS(status) != 0) {
192 			ksft_print_msg("Child failed\n");
193 			nerrs++;
194 		} else {
195 			/* don't print this message for mpid */
196 			if (getpid() != mpid)
197 				ksft_test_result_pass("Passed\n");
198 		}
199 		return false;
200 	} else {
201 		ksft_exit_fail_msg("fork - %s\n", strerror(errno));
202 		return false;
203 	}
204 }
205 
206 static void exec_other_validate_cap(const char *name,
207 				    bool eff, bool perm, bool inh, bool ambient)
208 {
209 	execl(name, name, (eff ? "1" : "0"),
210 	      (perm ? "1" : "0"), (inh ? "1" : "0"), (ambient ? "1" : "0"),
211 	      NULL);
212 	ksft_exit_fail_msg("execl - %s\n", strerror(errno));
213 }
214 
215 static void exec_validate_cap(bool eff, bool perm, bool inh, bool ambient)
216 {
217 	exec_other_validate_cap("./validate_cap", eff, perm, inh, ambient);
218 }
219 
220 static int do_tests(int uid, const char *our_path)
221 {
222 	bool have_outer_privilege = create_and_enter_ns(uid);
223 
224 	int ourpath_fd = open(our_path, O_RDONLY | O_DIRECTORY);
225 	if (ourpath_fd == -1)
226 		ksft_exit_fail_msg("open '%s' - %s\n",
227 					our_path, strerror(errno));
228 
229 	chdir_to_tmpfs();
230 
231 	copy_fromat_to(ourpath_fd, "validate_cap", "validate_cap");
232 
233 	if (have_outer_privilege) {
234 		uid_t gid = getegid();
235 
236 		copy_fromat_to(ourpath_fd, "validate_cap",
237 			       "validate_cap_suidroot");
238 		if (chown("validate_cap_suidroot", 0, -1) != 0)
239 			ksft_exit_fail_msg("chown - %s\n", strerror(errno));
240 		if (chmod("validate_cap_suidroot", S_ISUID | 0700) != 0)
241 			ksft_exit_fail_msg("chmod - %s\n", strerror(errno));
242 
243 		copy_fromat_to(ourpath_fd, "validate_cap",
244 			       "validate_cap_suidnonroot");
245 		if (chown("validate_cap_suidnonroot", uid + 1, -1) != 0)
246 			ksft_exit_fail_msg("chown - %s\n", strerror(errno));
247 		if (chmod("validate_cap_suidnonroot", S_ISUID | 0700) != 0)
248 			ksft_exit_fail_msg("chmod - %s\n", strerror(errno));
249 
250 		copy_fromat_to(ourpath_fd, "validate_cap",
251 			       "validate_cap_sgidroot");
252 		if (chown("validate_cap_sgidroot", -1, 0) != 0)
253 			ksft_exit_fail_msg("chown - %s\n", strerror(errno));
254 		if (chmod("validate_cap_sgidroot", S_ISGID | 0710) != 0)
255 			ksft_exit_fail_msg("chmod - %s\n", strerror(errno));
256 
257 		copy_fromat_to(ourpath_fd, "validate_cap",
258 			       "validate_cap_sgidnonroot");
259 		if (chown("validate_cap_sgidnonroot", -1, gid + 1) != 0)
260 			ksft_exit_fail_msg("chown - %s\n", strerror(errno));
261 		if (chmod("validate_cap_sgidnonroot", S_ISGID | 0710) != 0)
262 			ksft_exit_fail_msg("chmod - %s\n", strerror(errno));
263 	}
264 
265 	capng_get_caps_process();
266 
267 	/* Make sure that i starts out clear */
268 	capng_update(CAPNG_DROP, CAPNG_INHERITABLE, CAP_NET_BIND_SERVICE);
269 	if (capng_apply(CAPNG_SELECT_CAPS) != 0)
270 		ksft_exit_fail_msg("capng_apply - %s\n", strerror(errno));
271 
272 	if (uid == 0) {
273 		ksft_print_msg("[RUN]\tRoot => ep\n");
274 		if (fork_wait())
275 			exec_validate_cap(true, true, false, false);
276 	} else {
277 		ksft_print_msg("[RUN]\tNon-root => no caps\n");
278 		if (fork_wait())
279 			exec_validate_cap(false, false, false, false);
280 	}
281 
282 	ksft_print_msg("Check cap_ambient manipulation rules\n");
283 
284 	/* We should not be able to add ambient caps yet. */
285 	if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, CAP_NET_BIND_SERVICE, 0, 0, 0) != -1 || errno != EPERM) {
286 		if (errno == EINVAL)
287 			ksft_test_result_fail(
288 				"PR_CAP_AMBIENT_RAISE isn't supported\n");
289 		else
290 			ksft_test_result_fail(
291 				"PR_CAP_AMBIENT_RAISE should have failed eith EPERM on a non-inheritable cap\n");
292 		return 1;
293 	}
294 	ksft_test_result_pass(
295 		"PR_CAP_AMBIENT_RAISE failed on non-inheritable cap\n");
296 
297 	capng_update(CAPNG_ADD, CAPNG_INHERITABLE, CAP_NET_RAW);
298 	capng_update(CAPNG_DROP, CAPNG_PERMITTED, CAP_NET_RAW);
299 	capng_update(CAPNG_DROP, CAPNG_EFFECTIVE, CAP_NET_RAW);
300 	if (capng_apply(CAPNG_SELECT_CAPS) != 0)
301 		ksft_exit_fail_msg("capng_apply - %s\n", strerror(errno));
302 	if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, CAP_NET_RAW, 0, 0, 0) != -1 || errno != EPERM) {
303 		ksft_test_result_fail(
304 			"PR_CAP_AMBIENT_RAISE should have failed on a non-permitted cap\n");
305 		return 1;
306 	}
307 	ksft_test_result_pass(
308 		"PR_CAP_AMBIENT_RAISE failed on non-permitted cap\n");
309 
310 	capng_update(CAPNG_ADD, CAPNG_INHERITABLE, CAP_NET_BIND_SERVICE);
311 	if (capng_apply(CAPNG_SELECT_CAPS) != 0)
312 		ksft_exit_fail_msg("capng_apply - %s\n", strerror(errno));
313 	if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, CAP_NET_BIND_SERVICE, 0, 0, 0) != 0) {
314 		ksft_test_result_fail(
315 			"PR_CAP_AMBIENT_RAISE should have succeeded\n");
316 		return 1;
317 	}
318 	ksft_test_result_pass("PR_CAP_AMBIENT_RAISE worked\n");
319 
320 	if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_IS_SET, CAP_NET_BIND_SERVICE, 0, 0, 0) != 1) {
321 		ksft_test_result_fail("PR_CAP_AMBIENT_IS_SET is broken\n");
322 		return 1;
323 	}
324 
325 	if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_CLEAR_ALL, 0, 0, 0, 0) != 0)
326 		ksft_exit_fail_msg("PR_CAP_AMBIENT_CLEAR_ALL - %s\n",
327 					strerror(errno));
328 
329 	if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_IS_SET, CAP_NET_BIND_SERVICE, 0, 0, 0) != 0) {
330 		ksft_test_result_fail(
331 			"PR_CAP_AMBIENT_CLEAR_ALL didn't work\n");
332 		return 1;
333 	}
334 
335 	if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, CAP_NET_BIND_SERVICE, 0, 0, 0) != 0)
336 		ksft_exit_fail_msg("PR_CAP_AMBIENT_RAISE - %s\n",
337 					strerror(errno));
338 
339 	capng_update(CAPNG_DROP, CAPNG_INHERITABLE, CAP_NET_BIND_SERVICE);
340 	if (capng_apply(CAPNG_SELECT_CAPS) != 0)
341 		ksft_exit_fail_msg("capng_apply - %s\n", strerror(errno));
342 
343 	if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_IS_SET, CAP_NET_BIND_SERVICE, 0, 0, 0) != 0) {
344 		ksft_test_result_fail("Dropping I should have dropped A\n");
345 		return 1;
346 	}
347 
348 	ksft_test_result_pass("Basic manipulation appears to work\n");
349 
350 	capng_update(CAPNG_ADD, CAPNG_INHERITABLE, CAP_NET_BIND_SERVICE);
351 	if (capng_apply(CAPNG_SELECT_CAPS) != 0)
352 		ksft_exit_fail_msg("capng_apply - %s\n", strerror(errno));
353 	if (uid == 0) {
354 		ksft_print_msg("[RUN]\tRoot +i => eip\n");
355 		if (fork_wait())
356 			exec_validate_cap(true, true, true, false);
357 	} else {
358 		ksft_print_msg("[RUN]\tNon-root +i => i\n");
359 		if (fork_wait())
360 			exec_validate_cap(false, false, true, false);
361 	}
362 
363 	if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, CAP_NET_BIND_SERVICE, 0, 0, 0) != 0)
364 		ksft_exit_fail_msg("PR_CAP_AMBIENT_RAISE - %s\n",
365 					strerror(errno));
366 
367 	ksft_print_msg("[RUN]\tUID %d +ia => eipa\n", uid);
368 	if (fork_wait())
369 		exec_validate_cap(true, true, true, true);
370 
371 	/* The remaining tests need real privilege */
372 
373 	if (!have_outer_privilege) {
374 		ksft_test_result_skip("SUID/SGID tests (needs privilege)\n");
375 		goto done;
376 	}
377 
378 	if (uid == 0) {
379 		ksft_print_msg("[RUN]\tRoot +ia, suidroot => eipa\n");
380 		if (fork_wait())
381 			exec_other_validate_cap("./validate_cap_suidroot",
382 						true, true, true, true);
383 
384 		ksft_print_msg("[RUN]\tRoot +ia, suidnonroot => ip\n");
385 		if (fork_wait())
386 			exec_other_validate_cap("./validate_cap_suidnonroot",
387 						false, true, true, false);
388 
389 		ksft_print_msg("[RUN]\tRoot +ia, sgidroot => eipa\n");
390 		if (fork_wait())
391 			exec_other_validate_cap("./validate_cap_sgidroot",
392 						true, true, true, true);
393 
394 		if (fork_wait()) {
395 			ksft_print_msg(
396 				"[RUN]\tRoot, gid != 0, +ia, sgidroot => eip\n");
397 			if (setresgid(1, 1, 1) != 0)
398 				ksft_exit_fail_msg("setresgid - %s\n",
399 							strerror(errno));
400 			exec_other_validate_cap("./validate_cap_sgidroot",
401 						true, true, true, false);
402 		}
403 
404 		ksft_print_msg("[RUN]\tRoot +ia, sgidnonroot => eip\n");
405 		if (fork_wait())
406 			exec_other_validate_cap("./validate_cap_sgidnonroot",
407 						true, true, true, false);
408 	} else {
409 		ksft_print_msg("[RUN]\tNon-root +ia, sgidnonroot => i\n");
410 		if (fork_wait())
411 			exec_other_validate_cap("./validate_cap_sgidnonroot",
412 					false, false, true, false);
413 
414 		if (fork_wait()) {
415 			ksft_print_msg("[RUN]\tNon-root +ia, sgidroot => i\n");
416 			if (setresgid(1, 1, 1) != 0)
417 				ksft_exit_fail_msg("setresgid - %s\n",
418 							strerror(errno));
419 			exec_other_validate_cap("./validate_cap_sgidroot",
420 						false, false, true, false);
421 		}
422 	}
423 
424 done:
425 	ksft_print_cnts();
426 	return nerrs ? 1 : 0;
427 }
428 
429 int main(int argc, char **argv)
430 {
431 	char *tmp1, *tmp2, *our_path;
432 
433 	ksft_print_header();
434 
435 	/* Find our path */
436 	tmp1 = strdup(argv[0]);
437 	if (!tmp1)
438 		ksft_exit_fail_msg("strdup - %s\n", strerror(errno));
439 	tmp2 = dirname(tmp1);
440 	our_path = strdup(tmp2);
441 	if (!our_path)
442 		ksft_exit_fail_msg("strdup - %s\n", strerror(errno));
443 	free(tmp1);
444 
445 	mpid = getpid();
446 
447 	if (fork_wait()) {
448 		ksft_print_msg("[RUN]\t+++ Tests with uid == 0 +++\n");
449 		return do_tests(0, our_path);
450 	}
451 
452 	ksft_print_msg("==================================================\n");
453 
454 	if (fork_wait()) {
455 		ksft_print_msg("[RUN]\t+++ Tests with uid != 0 +++\n");
456 		return do_tests(1, our_path);
457 	}
458 
459 	return nerrs ? 1 : 0;
460 }
461