tools/testing/selftests/capabilities/test_execve.c

   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 }