tools/testing/selftests/capabilities/test_execve.c

   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         if (umount2(".", MNT_DETACH) != 0)
 143                 err(1, "detach private tmpfs");
 144 }
 145
 146 static 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
 170 static 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
 195 static 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
 204 static 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
 209 static 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
 398 done:
 399         return nerrs ? 1 : 0;
 400 }
 401
 402 int 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 }