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1#define _GNU_SOURCE
2
3#include <cap-ng.h>
4#include <err.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#ifndef PR_CAP_AMBIENT
22#define PR_CAP_AMBIENT 47
23# define PR_CAP_AMBIENT_IS_SET 1
24# define PR_CAP_AMBIENT_RAISE 2
25# define PR_CAP_AMBIENT_LOWER 3
26# define PR_CAP_AMBIENT_CLEAR_ALL 4
27#endif
28
29static int nerrs;
30
31static void vmaybe_write_file(bool enoent_ok, char *filename, char *fmt, va_list ap)
32{
33 char buf[4096];
34 int fd;
35 ssize_t written;
36 int buf_len;
37
38 buf_len = vsnprintf(buf, sizeof(buf), fmt, ap);
39 if (buf_len < 0) {
40 err(1, "vsnprintf failed");
41 }
42 if (buf_len >= sizeof(buf)) {
43 errx(1, "vsnprintf output truncated");
44 }
45
46 fd = open(filename, O_WRONLY);
47 if (fd < 0) {
48 if ((errno == ENOENT) && enoent_ok)
49 return;
50 err(1, "open of %s failed", filename);
51 }
52 written = write(fd, buf, buf_len);
53 if (written != buf_len) {
54 if (written >= 0) {
55 errx(1, "short write to %s", filename);
56 } else {
57 err(1, "write to %s failed", filename);
58 }
59 }
60 if (close(fd) != 0) {
61 err(1, "close of %s failed", filename);
62 }
63}
64
65static void maybe_write_file(char *filename, char *fmt, ...)
66{
67 va_list ap;
68
69 va_start(ap, fmt);
70 vmaybe_write_file(true, filename, fmt, ap);
71 va_end(ap);
72}
73
74static void write_file(char *filename, char *fmt, ...)
75{
76 va_list ap;
77
78 va_start(ap, fmt);
79 vmaybe_write_file(false, filename, fmt, ap);
80 va_end(ap);
81}
82
83static bool create_and_enter_ns(uid_t inner_uid)
84{
85 uid_t outer_uid;
86 gid_t outer_gid;
87 int i;
88 bool have_outer_privilege;
89
90 outer_uid = getuid();
91 outer_gid = getgid();
92
93 /*
94 * TODO: If we're already root, we could skip creating the userns.
95 */
96
97 if (unshare(CLONE_NEWNS) == 0) {
98 printf("[NOTE]\tUsing global UIDs for tests\n");
99 if (prctl(PR_SET_KEEPCAPS, 1, 0, 0, 0) != 0)
100 err(1, "PR_SET_KEEPCAPS");
101 if (setresuid(inner_uid, inner_uid, -1) != 0)
102 err(1, "setresuid");
103
104 // Re-enable effective caps
105 capng_get_caps_process();
106 for (i = 0; i < CAP_LAST_CAP; i++)
107 if (capng_have_capability(CAPNG_PERMITTED, i))
108 capng_update(CAPNG_ADD, CAPNG_EFFECTIVE, i);
109 if (capng_apply(CAPNG_SELECT_CAPS) != 0)
110 err(1, "capng_apply");
111
112 have_outer_privilege = true;
113 } else if (unshare(CLONE_NEWUSER | CLONE_NEWNS) == 0) {
114 printf("[NOTE]\tUsing a user namespace for tests\n");
115 maybe_write_file("/proc/self/setgroups", "deny");
116 write_file("/proc/self/uid_map", "%d %d 1", inner_uid, outer_uid);
117 write_file("/proc/self/gid_map", "0 %d 1", outer_gid);
118
119 have_outer_privilege = false;
120 } else {
121 errx(1, "must be root or be able to create a userns");
122 }
123
124 if (mount("none", "/", NULL, MS_REC | MS_PRIVATE, NULL) != 0)
125 err(1, "remount everything private");
126
127 return have_outer_privilege;
128}
129
130static void chdir_to_tmpfs(void)
131{
132 char cwd[PATH_MAX];
133 if (getcwd(cwd, sizeof(cwd)) != cwd)
134 err(1, "getcwd");
135
136 if (mount("private_tmp", ".", "tmpfs", 0, "mode=0777") != 0)
137 err(1, "mount private tmpfs");
138
139 if (chdir(cwd) != 0)
140 err(1, "chdir to private tmpfs");
141
142 if (umount2(".", MNT_DETACH) != 0)
143 err(1, "detach private tmpfs");
144}
145
146static void copy_fromat_to(int fromfd, const char *fromname, const char *toname)
147{
148 int from = openat(fromfd, fromname, O_RDONLY);
149 if (from == -1)
150 err(1, "open copy source");
151
152 int to = open(toname, O_CREAT | O_WRONLY | O_EXCL, 0700);
153
154 while (true) {
155 char buf[4096];
156 ssize_t sz = read(from, buf, sizeof(buf));
157 if (sz == 0)
158 break;
159 if (sz < 0)
160 err(1, "read");
161
162 if (write(to, buf, sz) != sz)
163 err(1, "write"); /* no short writes on tmpfs */
164 }
165
166 close(from);
167 close(to);
168}
169
170static bool fork_wait(void)
171{
172 pid_t child = fork();
173 if (child == 0) {
174 nerrs = 0;
175 return true;
176 } else if (child > 0) {
177 int status;
178 if (waitpid(child, &status, 0) != child ||
179 !WIFEXITED(status)) {
180 printf("[FAIL]\tChild died\n");
181 nerrs++;
182 } else if (WEXITSTATUS(status) != 0) {
183 printf("[FAIL]\tChild failed\n");
184 nerrs++;
185 } else {
186 printf("[OK]\tChild succeeded\n");
187 }
188
189 return false;
190 } else {
191 err(1, "fork");
192 }
193}
194
195static void exec_other_validate_cap(const char *name,
196 bool eff, bool perm, bool inh, bool ambient)
197{
198 execl(name, name, (eff ? "1" : "0"),
199 (perm ? "1" : "0"), (inh ? "1" : "0"), (ambient ? "1" : "0"),
200 NULL);
201 err(1, "execl");
202}
203
204static void exec_validate_cap(bool eff, bool perm, bool inh, bool ambient)
205{
206 exec_other_validate_cap("./validate_cap", eff, perm, inh, ambient);
207}
208
209static int do_tests(int uid, const char *our_path)
210{
211 bool have_outer_privilege = create_and_enter_ns(uid);
212
213 int ourpath_fd = open(our_path, O_RDONLY | O_DIRECTORY);
214 if (ourpath_fd == -1)
215 err(1, "open '%s'", our_path);
216
217 chdir_to_tmpfs();
218
219 copy_fromat_to(ourpath_fd, "validate_cap", "validate_cap");
220
221 if (have_outer_privilege) {
222 uid_t gid = getegid();
223
224 copy_fromat_to(ourpath_fd, "validate_cap",
225 "validate_cap_suidroot");
226 if (chown("validate_cap_suidroot", 0, -1) != 0)
227 err(1, "chown");
228 if (chmod("validate_cap_suidroot", S_ISUID | 0700) != 0)
229 err(1, "chmod");
230
231 copy_fromat_to(ourpath_fd, "validate_cap",
232 "validate_cap_suidnonroot");
233 if (chown("validate_cap_suidnonroot", uid + 1, -1) != 0)
234 err(1, "chown");
235 if (chmod("validate_cap_suidnonroot", S_ISUID | 0700) != 0)
236 err(1, "chmod");
237
238 copy_fromat_to(ourpath_fd, "validate_cap",
239 "validate_cap_sgidroot");
240 if (chown("validate_cap_sgidroot", -1, 0) != 0)
241 err(1, "chown");
242 if (chmod("validate_cap_sgidroot", S_ISGID | 0710) != 0)
243 err(1, "chmod");
244
245 copy_fromat_to(ourpath_fd, "validate_cap",
246 "validate_cap_sgidnonroot");
247 if (chown("validate_cap_sgidnonroot", -1, gid + 1) != 0)
248 err(1, "chown");
249 if (chmod("validate_cap_sgidnonroot", S_ISGID | 0710) != 0)
250 err(1, "chmod");
251}
252
253 capng_get_caps_process();
254
255 /* Make sure that i starts out clear */
256 capng_update(CAPNG_DROP, CAPNG_INHERITABLE, CAP_NET_BIND_SERVICE);
257 if (capng_apply(CAPNG_SELECT_CAPS) != 0)
258 err(1, "capng_apply");
259
260 if (uid == 0) {
261 printf("[RUN]\tRoot => ep\n");
262 if (fork_wait())
263 exec_validate_cap(true, true, false, false);
264 } else {
265 printf("[RUN]\tNon-root => no caps\n");
266 if (fork_wait())
267 exec_validate_cap(false, false, false, false);
268 }
269
270 printf("[OK]\tCheck cap_ambient manipulation rules\n");
271
272 /* We should not be able to add ambient caps yet. */
273 if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, CAP_NET_BIND_SERVICE, 0, 0, 0) != -1 || errno != EPERM) {
274 if (errno == EINVAL)
275 printf("[FAIL]\tPR_CAP_AMBIENT_RAISE isn't supported\n");
276 else
277 printf("[FAIL]\tPR_CAP_AMBIENT_RAISE should have failed eith EPERM on a non-inheritable cap\n");
278 return 1;
279 }
280 printf("[OK]\tPR_CAP_AMBIENT_RAISE failed on non-inheritable cap\n");
281
282 capng_update(CAPNG_ADD, CAPNG_INHERITABLE, CAP_NET_RAW);
283 capng_update(CAPNG_DROP, CAPNG_PERMITTED, CAP_NET_RAW);
284 capng_update(CAPNG_DROP, CAPNG_EFFECTIVE, CAP_NET_RAW);
285 if (capng_apply(CAPNG_SELECT_CAPS) != 0)
286 err(1, "capng_apply");
287 if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, CAP_NET_RAW, 0, 0, 0) != -1 || errno != EPERM) {
288 printf("[FAIL]\tPR_CAP_AMBIENT_RAISE should have failed on a non-permitted cap\n");
289 return 1;
290 }
291 printf("[OK]\tPR_CAP_AMBIENT_RAISE failed on non-permitted cap\n");
292
293 capng_update(CAPNG_ADD, CAPNG_INHERITABLE, CAP_NET_BIND_SERVICE);
294 if (capng_apply(CAPNG_SELECT_CAPS) != 0)
295 err(1, "capng_apply");
296 if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, CAP_NET_BIND_SERVICE, 0, 0, 0) != 0) {
297 printf("[FAIL]\tPR_CAP_AMBIENT_RAISE should have succeeded\n");
298 return 1;
299 }
300 printf("[OK]\tPR_CAP_AMBIENT_RAISE worked\n");
301
302 if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_IS_SET, CAP_NET_BIND_SERVICE, 0, 0, 0) != 1) {
303 printf("[FAIL]\tPR_CAP_AMBIENT_IS_SET is broken\n");
304 return 1;
305 }
306
307 if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_CLEAR_ALL, 0, 0, 0, 0) != 0)
308 err(1, "PR_CAP_AMBIENT_CLEAR_ALL");
309
310 if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_IS_SET, CAP_NET_BIND_SERVICE, 0, 0, 0) != 0) {
311 printf("[FAIL]\tPR_CAP_AMBIENT_CLEAR_ALL didn't work\n");
312 return 1;
313 }
314
315 if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, CAP_NET_BIND_SERVICE, 0, 0, 0) != 0)
316 err(1, "PR_CAP_AMBIENT_RAISE");
317
318 capng_update(CAPNG_DROP, CAPNG_INHERITABLE, CAP_NET_BIND_SERVICE);
319 if (capng_apply(CAPNG_SELECT_CAPS) != 0)
320 err(1, "capng_apply");
321
322 if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_IS_SET, CAP_NET_BIND_SERVICE, 0, 0, 0) != 0) {
323 printf("[FAIL]\tDropping I should have dropped A\n");
324 return 1;
325 }
326
327 printf("[OK]\tBasic manipulation appears to work\n");
328
329 capng_update(CAPNG_ADD, CAPNG_INHERITABLE, CAP_NET_BIND_SERVICE);
330 if (capng_apply(CAPNG_SELECT_CAPS) != 0)
331 err(1, "capng_apply");
332 if (uid == 0) {
333 printf("[RUN]\tRoot +i => eip\n");
334 if (fork_wait())
335 exec_validate_cap(true, true, true, false);
336 } else {
337 printf("[RUN]\tNon-root +i => i\n");
338 if (fork_wait())
339 exec_validate_cap(false, false, true, false);
340 }
341
342 if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, CAP_NET_BIND_SERVICE, 0, 0, 0) != 0)
343 err(1, "PR_CAP_AMBIENT_RAISE");
344
345 printf("[RUN]\tUID %d +ia => eipa\n", uid);
346 if (fork_wait())
347 exec_validate_cap(true, true, true, true);
348
349 /* The remaining tests need real privilege */
350
351 if (!have_outer_privilege) {
352 printf("[SKIP]\tSUID/SGID tests (needs privilege)\n");
353 goto done;
354 }
355
356 if (uid == 0) {
357 printf("[RUN]\tRoot +ia, suidroot => eipa\n");
358 if (fork_wait())
359 exec_other_validate_cap("./validate_cap_suidroot",
360 true, true, true, true);
361
362 printf("[RUN]\tRoot +ia, suidnonroot => ip\n");
363 if (fork_wait())
364 exec_other_validate_cap("./validate_cap_suidnonroot",
365 false, true, true, false);
366
367 printf("[RUN]\tRoot +ia, sgidroot => eipa\n");
368 if (fork_wait())
369 exec_other_validate_cap("./validate_cap_sgidroot",
370 true, true, true, true);
371
372 if (fork_wait()) {
373 printf("[RUN]\tRoot, gid != 0, +ia, sgidroot => eip\n");
374 if (setresgid(1, 1, 1) != 0)
375 err(1, "setresgid");
376 exec_other_validate_cap("./validate_cap_sgidroot",
377 true, true, true, false);
378 }
379
380 printf("[RUN]\tRoot +ia, sgidnonroot => eip\n");
381 if (fork_wait())
382 exec_other_validate_cap("./validate_cap_sgidnonroot",
383 true, true, true, false);
384 } else {
385 printf("[RUN]\tNon-root +ia, sgidnonroot => i\n");
386 exec_other_validate_cap("./validate_cap_sgidnonroot",
387 false, false, true, false);
388
389 if (fork_wait()) {
390 printf("[RUN]\tNon-root +ia, sgidroot => i\n");
391 if (setresgid(1, 1, 1) != 0)
392 err(1, "setresgid");
393 exec_other_validate_cap("./validate_cap_sgidroot",
394 false, false, true, false);
395 }
396 }
397
398done:
399 return nerrs ? 1 : 0;
400}
401
402int main(int argc, char **argv)
403{
404 char *tmp1, *tmp2, *our_path;
405
406 /* Find our path */
407 tmp1 = strdup(argv[0]);
408 if (!tmp1)
409 err(1, "strdup");
410 tmp2 = dirname(tmp1);
411 our_path = strdup(tmp2);
412 if (!our_path)
413 err(1, "strdup");
414 free(tmp1);
415
416 if (fork_wait()) {
417 printf("[RUN]\t+++ Tests with uid == 0 +++\n");
418 return do_tests(0, our_path);
419 }
420
421 if (fork_wait()) {
422 printf("[RUN]\t+++ Tests with uid != 0 +++\n");
423 return do_tests(1, our_path);
424 }
425
426 return nerrs ? 1 : 0;
427}