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
 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                 exec_other_validate_cap("./validate_cap_sgidnonroot",
 384                                         false, false, true, false);
 385
 386                 if (fork_wait()) {
 387                         printf("[RUN]\tNon-root +ia, sgidroot => i\n");
 388                         if (setresgid(1, 1, 1) != 0)
 389                                 err(1, "setresgid");
 390                         exec_other_validate_cap("./validate_cap_sgidroot",
 391                                                 false, false, true, false);
 392                 }
 393         }
 394
 395 done:
 396         return nerrs ? 1 : 0;
 397 }
 398
 399 int main(int argc, char **argv)
 400 {
 401         char *tmp1, *tmp2, *our_path;
 402
 403         /* Find our path */
 404         tmp1 = strdup(argv[0]);
 405         if (!tmp1)
 406                 err(1, "strdup");
 407         tmp2 = dirname(tmp1);
 408         our_path = strdup(tmp2);
 409         if (!our_path)
 410                 err(1, "strdup");
 411         free(tmp1);
 412
 413         if (fork_wait()) {
 414                 printf("[RUN]\t+++ Tests with uid == 0 +++\n");
 415                 return do_tests(0, our_path);
 416         }
 417
 418         if (fork_wait()) {
 419                 printf("[RUN]\t+++ Tests with uid != 0 +++\n");
 420                 return do_tests(1, our_path);
 421         }
 422
 423         return nerrs ? 1 : 0;
 424 }