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 29 static int nerrs; 30 31 static 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 65 static 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 74 static 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 83 static 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 } 129 130 static 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 } 142 143 static void copy_fromat_to(int fromfd, const char *fromname, const char *toname) 144 { 145 int from = openat(fromfd, fromname, O_RDONLY); 146 if (from == -1) 147 err(1, "open copy source"); 148 149 int to = open(toname, O_CREAT | O_WRONLY | O_EXCL, 0700); 150 151 while (true) { 152 char buf[4096]; 153 ssize_t sz = read(from, buf, sizeof(buf)); 154 if (sz == 0) 155 break; 156 if (sz < 0) 157 err(1, "read"); 158 159 if (write(to, buf, sz) != sz) 160 err(1, "write"); /* no short writes on tmpfs */ 161 } 162 163 close(from); 164 close(to); 165 } 166 167 static bool fork_wait(void) 168 { 169 pid_t child = fork(); 170 if (child == 0) { 171 nerrs = 0; 172 return true; 173 } else if (child > 0) { 174 int status; 175 if (waitpid(child, &status, 0) != child || 176 !WIFEXITED(status)) { 177 printf("[FAIL]\tChild died\n"); 178 nerrs++; 179 } else if (WEXITSTATUS(status) != 0) { 180 printf("[FAIL]\tChild failed\n"); 181 nerrs++; 182 } else { 183 printf("[OK]\tChild succeeded\n"); 184 } 185 186 return false; 187 } else { 188 err(1, "fork"); 189 } 190 } 191 192 static void exec_other_validate_cap(const char *name, 193 bool eff, bool perm, bool inh, bool ambient) 194 { 195 execl(name, name, (eff ? "1" : "0"), 196 (perm ? "1" : "0"), (inh ? "1" : "0"), (ambient ? "1" : "0"), 197 NULL); 198 err(1, "execl"); 199 } 200 201 static void exec_validate_cap(bool eff, bool perm, bool inh, bool ambient) 202 { 203 exec_other_validate_cap("./validate_cap", eff, perm, inh, ambient); 204 } 205 206 static int do_tests(int uid, const char *our_path) 207 { 208 bool have_outer_privilege = create_and_enter_ns(uid); 209 210 int ourpath_fd = open(our_path, O_RDONLY | O_DIRECTORY); 211 if (ourpath_fd == -1) 212 err(1, "open '%s'", our_path); 213 214 chdir_to_tmpfs(); 215 216 copy_fromat_to(ourpath_fd, "validate_cap", "validate_cap"); 217 218 if (have_outer_privilege) { 219 uid_t gid = getegid(); 220 221 copy_fromat_to(ourpath_fd, "validate_cap", 222 "validate_cap_suidroot"); 223 if (chown("validate_cap_suidroot", 0, -1) != 0) 224 err(1, "chown"); 225 if (chmod("validate_cap_suidroot", S_ISUID | 0700) != 0) 226 err(1, "chmod"); 227 228 copy_fromat_to(ourpath_fd, "validate_cap", 229 "validate_cap_suidnonroot"); 230 if (chown("validate_cap_suidnonroot", uid + 1, -1) != 0) 231 err(1, "chown"); 232 if (chmod("validate_cap_suidnonroot", S_ISUID | 0700) != 0) 233 err(1, "chmod"); 234 235 copy_fromat_to(ourpath_fd, "validate_cap", 236 "validate_cap_sgidroot"); 237 if (chown("validate_cap_sgidroot", -1, 0) != 0) 238 err(1, "chown"); 239 if (chmod("validate_cap_sgidroot", S_ISGID | 0710) != 0) 240 err(1, "chmod"); 241 242 copy_fromat_to(ourpath_fd, "validate_cap", 243 "validate_cap_sgidnonroot"); 244 if (chown("validate_cap_sgidnonroot", -1, gid + 1) != 0) 245 err(1, "chown"); 246 if (chmod("validate_cap_sgidnonroot", S_ISGID | 0710) != 0) 247 err(1, "chmod"); 248 } 249 250 capng_get_caps_process(); 251 252 /* Make sure that i starts out clear */ 253 capng_update(CAPNG_DROP, CAPNG_INHERITABLE, CAP_NET_BIND_SERVICE); 254 if (capng_apply(CAPNG_SELECT_CAPS) != 0) 255 err(1, "capng_apply"); 256 257 if (uid == 0) { 258 printf("[RUN]\tRoot => ep\n"); 259 if (fork_wait()) 260 exec_validate_cap(true, true, false, false); 261 } else { 262 printf("[RUN]\tNon-root => no caps\n"); 263 if (fork_wait()) 264 exec_validate_cap(false, false, false, false); 265 } 266 267 printf("[OK]\tCheck cap_ambient manipulation rules\n"); 268 269 /* We should not be able to add ambient caps yet. */ 270 if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, CAP_NET_BIND_SERVICE, 0, 0, 0) != -1 || errno != EPERM) { 271 if (errno == EINVAL) 272 printf("[FAIL]\tPR_CAP_AMBIENT_RAISE isn't supported\n"); 273 else 274 printf("[FAIL]\tPR_CAP_AMBIENT_RAISE should have failed eith EPERM on a non-inheritable cap\n"); 275 return 1; 276 } 277 printf("[OK]\tPR_CAP_AMBIENT_RAISE failed on non-inheritable cap\n"); 278 279 capng_update(CAPNG_ADD, CAPNG_INHERITABLE, CAP_NET_RAW); 280 capng_update(CAPNG_DROP, CAPNG_PERMITTED, CAP_NET_RAW); 281 capng_update(CAPNG_DROP, CAPNG_EFFECTIVE, CAP_NET_RAW); 282 if (capng_apply(CAPNG_SELECT_CAPS) != 0) 283 err(1, "capng_apply"); 284 if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, CAP_NET_RAW, 0, 0, 0) != -1 || errno != EPERM) { 285 printf("[FAIL]\tPR_CAP_AMBIENT_RAISE should have failed on a non-permitted cap\n"); 286 return 1; 287 } 288 printf("[OK]\tPR_CAP_AMBIENT_RAISE failed on non-permitted cap\n"); 289 290 capng_update(CAPNG_ADD, CAPNG_INHERITABLE, CAP_NET_BIND_SERVICE); 291 if (capng_apply(CAPNG_SELECT_CAPS) != 0) 292 err(1, "capng_apply"); 293 if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, CAP_NET_BIND_SERVICE, 0, 0, 0) != 0) { 294 printf("[FAIL]\tPR_CAP_AMBIENT_RAISE should have succeeded\n"); 295 return 1; 296 } 297 printf("[OK]\tPR_CAP_AMBIENT_RAISE worked\n"); 298 299 if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_IS_SET, CAP_NET_BIND_SERVICE, 0, 0, 0) != 1) { 300 printf("[FAIL]\tPR_CAP_AMBIENT_IS_SET is broken\n"); 301 return 1; 302 } 303 304 if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_CLEAR_ALL, 0, 0, 0, 0) != 0) 305 err(1, "PR_CAP_AMBIENT_CLEAR_ALL"); 306 307 if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_IS_SET, CAP_NET_BIND_SERVICE, 0, 0, 0) != 0) { 308 printf("[FAIL]\tPR_CAP_AMBIENT_CLEAR_ALL didn't work\n"); 309 return 1; 310 } 311 312 if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, CAP_NET_BIND_SERVICE, 0, 0, 0) != 0) 313 err(1, "PR_CAP_AMBIENT_RAISE"); 314 315 capng_update(CAPNG_DROP, CAPNG_INHERITABLE, CAP_NET_BIND_SERVICE); 316 if (capng_apply(CAPNG_SELECT_CAPS) != 0) 317 err(1, "capng_apply"); 318 319 if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_IS_SET, CAP_NET_BIND_SERVICE, 0, 0, 0) != 0) { 320 printf("[FAIL]\tDropping I should have dropped A\n"); 321 return 1; 322 } 323 324 printf("[OK]\tBasic manipulation appears to work\n"); 325 326 capng_update(CAPNG_ADD, CAPNG_INHERITABLE, CAP_NET_BIND_SERVICE); 327 if (capng_apply(CAPNG_SELECT_CAPS) != 0) 328 err(1, "capng_apply"); 329 if (uid == 0) { 330 printf("[RUN]\tRoot +i => eip\n"); 331 if (fork_wait()) 332 exec_validate_cap(true, true, true, false); 333 } else { 334 printf("[RUN]\tNon-root +i => i\n"); 335 if (fork_wait()) 336 exec_validate_cap(false, false, true, false); 337 } 338 339 if (prctl(PR_CAP_AMBIENT, PR_CAP_AMBIENT_RAISE, CAP_NET_BIND_SERVICE, 0, 0, 0) != 0) 340 err(1, "PR_CAP_AMBIENT_RAISE"); 341 342 printf("[RUN]\tUID %d +ia => eipa\n", uid); 343 if (fork_wait()) 344 exec_validate_cap(true, true, true, true); 345 346 /* The remaining tests need real privilege */ 347 348 if (!have_outer_privilege) { 349 printf("[SKIP]\tSUID/SGID tests (needs privilege)\n"); 350 goto done; 351 } 352 353 if (uid == 0) { 354 printf("[RUN]\tRoot +ia, suidroot => eipa\n"); 355 if (fork_wait()) 356 exec_other_validate_cap("./validate_cap_suidroot", 357 true, true, true, true); 358 359 printf("[RUN]\tRoot +ia, suidnonroot => ip\n"); 360 if (fork_wait()) 361 exec_other_validate_cap("./validate_cap_suidnonroot", 362 false, true, true, false); 363 364 printf("[RUN]\tRoot +ia, sgidroot => eipa\n"); 365 if (fork_wait()) 366 exec_other_validate_cap("./validate_cap_sgidroot", 367 true, true, true, true); 368 369 if (fork_wait()) { 370 printf("[RUN]\tRoot, gid != 0, +ia, sgidroot => eip\n"); 371 if (setresgid(1, 1, 1) != 0) 372 err(1, "setresgid"); 373 exec_other_validate_cap("./validate_cap_sgidroot", 374 true, true, true, false); 375 } 376 377 printf("[RUN]\tRoot +ia, sgidnonroot => eip\n"); 378 if (fork_wait()) 379 exec_other_validate_cap("./validate_cap_sgidnonroot", 380 true, true, true, false); 381 } else { 382 printf("[RUN]\tNon-root +ia, sgidnonroot => i\n"); 383 if (fork_wait()) 384 exec_other_validate_cap("./validate_cap_sgidnonroot", 385 false, false, true, false); 386 387 if (fork_wait()) { 388 printf("[RUN]\tNon-root +ia, sgidroot => i\n"); 389 if (setresgid(1, 1, 1) != 0) 390 err(1, "setresgid"); 391 exec_other_validate_cap("./validate_cap_sgidroot", 392 false, false, true, false); 393 } 394 } 395 396 done: 397 return nerrs ? 1 : 0; 398 } 399 400 int main(int argc, char **argv) 401 { 402 char *tmp1, *tmp2, *our_path; 403 404 /* Find our path */ 405 tmp1 = strdup(argv[0]); 406 if (!tmp1) 407 err(1, "strdup"); 408 tmp2 = dirname(tmp1); 409 our_path = strdup(tmp2); 410 if (!our_path) 411 err(1, "strdup"); 412 free(tmp1); 413 414 if (fork_wait()) { 415 printf("[RUN]\t+++ Tests with uid == 0 +++\n"); 416 return do_tests(0, our_path); 417 } 418 419 if (fork_wait()) { 420 printf("[RUN]\t+++ Tests with uid != 0 +++\n"); 421 return do_tests(1, our_path); 422 } 423 424 return nerrs ? 1 : 0; 425 } 426