aboutsummaryrefslogtreecommitdiffstats
path: root/capmode.cc
blob: 567773f319d98855fd3dcb9f7e43e66b48ead91a (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
// Test routines to make sure a variety of system calls are or are not
// available in capability mode.  The goal is not to see if they work, just
// whether or not they return the expected ECAPMODE.
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/mount.h>
#include <sys/mman.h>
#include <sys/wait.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/ptrace.h>
#include <dirent.h>
#include <netinet/in.h>
#include <fcntl.h>
#include <sched.h>
#include <time.h>
#include <unistd.h>
#include <pthread.h>

#include "capsicum.h"
#include "syscalls.h"
#include "capsicum-test.h"

// Test fixture that opens (and closes) a bunch of files.
class WithFiles : public ::testing::Test {
 public:
  WithFiles() :
    fd_file_(open(TmpFile("cap_capmode"), O_RDWR|O_CREAT, 0644)),
    fd_close_(open("/dev/null", O_RDWR)),
    fd_dir_(open(tmpdir.c_str(), O_RDONLY)),
    fd_socket_(socket(PF_INET, SOCK_DGRAM, 0)),
    fd_tcp_socket_(socket(PF_INET, SOCK_STREAM, 0)) {
    EXPECT_OK(fd_file_);
    EXPECT_OK(fd_close_);
    EXPECT_OK(fd_dir_);
    EXPECT_OK(fd_socket_);
    EXPECT_OK(fd_tcp_socket_);
  }
  ~WithFiles() {
    if (fd_tcp_socket_ >= 0) close(fd_tcp_socket_);
    if (fd_socket_ >= 0) close(fd_socket_);
    if (fd_dir_ >= 0) close(fd_dir_);
    if (fd_close_ >= 0) close(fd_close_);
    if (fd_file_ >= 0) close(fd_file_);
    unlink(TmpFile("cap_capmode"));
  }
 protected:
  int fd_file_;
  int fd_close_;
  int fd_dir_;
  int fd_socket_;
  int fd_tcp_socket_;
};

FORK_TEST_F(WithFiles, DisallowedFileSyscalls) {
  unsigned int mode = -1;
  EXPECT_OK(cap_getmode(&mode));
  EXPECT_EQ(0, (int)mode);
  EXPECT_OK(cap_enter());  // Enter capability mode.
  EXPECT_OK(cap_getmode(&mode));
  EXPECT_EQ(1, (int)mode);

  // System calls that are not permitted in capability mode.
  EXPECT_CAPMODE(access(TmpFile("cap_capmode_access"), F_OK));
  EXPECT_CAPMODE(acct(TmpFile("cap_capmode_acct")));
  EXPECT_CAPMODE(chdir(TmpFile("cap_capmode_chdir")));
#ifdef HAVE_CHFLAGS
  EXPECT_CAPMODE(chflags(TmpFile("cap_capmode_chflags"), UF_NODUMP));
#endif
  EXPECT_CAPMODE(chmod(TmpFile("cap_capmode_chmod"), 0644));
  EXPECT_CAPMODE(chown(TmpFile("cap_capmode_chown"), -1, -1));
  EXPECT_CAPMODE(chroot(TmpFile("cap_capmode_chroot")));
  EXPECT_CAPMODE(creat(TmpFile("cap_capmode_creat"), 0644));
  EXPECT_CAPMODE(fchdir(fd_dir_));
#ifdef HAVE_GETFSSTAT
  struct statfs statfs;
  EXPECT_CAPMODE(getfsstat(&statfs, sizeof(statfs), MNT_NOWAIT));
#endif
  EXPECT_CAPMODE(link(TmpFile("foo"), TmpFile("bar")));
  struct stat sb;
  EXPECT_CAPMODE(lstat(TmpFile("cap_capmode_lstat"), &sb));
  EXPECT_CAPMODE(mknod(TmpFile("capmode_mknod"), 0644 | S_IFIFO, 0));
  EXPECT_CAPMODE(bogus_mount_());
  EXPECT_CAPMODE(open("/dev/null", O_RDWR));
  char buf[64];
  EXPECT_CAPMODE(readlink(TmpFile("cap_capmode_readlink"), buf, sizeof(buf)));
#ifdef HAVE_REVOKE
  EXPECT_CAPMODE(revoke(TmpFile("cap_capmode_revoke")));
#endif
  EXPECT_CAPMODE(stat(TmpFile("cap_capmode_stat"), &sb));
  EXPECT_CAPMODE(symlink(TmpFile("cap_capmode_symlink_from"), TmpFile("cap_capmode_symlink_to")));
  EXPECT_CAPMODE(unlink(TmpFile("cap_capmode_unlink")));
  EXPECT_CAPMODE(umount2("/not_mounted", 0));
}

FORK_TEST_F(WithFiles, DisallowedSocketSyscalls) {
  EXPECT_OK(cap_enter());  // Enter capability mode.

  // System calls that are not permitted in capability mode.
  struct sockaddr_in addr;
  addr.sin_family = AF_INET;
  addr.sin_port = 0;
  addr.sin_addr.s_addr = htonl(INADDR_ANY);
  EXPECT_CAPMODE(bind_(fd_socket_, (sockaddr*)&addr, sizeof(addr)));
  addr.sin_family = AF_INET;
  addr.sin_port = 53;
  addr.sin_addr.s_addr = htonl(0x08080808);
  EXPECT_CAPMODE(connect_(fd_tcp_socket_, (sockaddr*)&addr, sizeof(addr)));
}

FORK_TEST_F(WithFiles, AllowedFileSyscalls) {
  int rc;
  EXPECT_OK(cap_enter());  // Enter capability mode.

  EXPECT_OK(close(fd_close_));
  fd_close_ = -1;
  int fd_dup = dup(fd_file_);
  EXPECT_OK(fd_dup);
  EXPECT_OK(dup2(fd_file_, fd_dup));
#ifdef HAVE_DUP3
  EXPECT_OK(dup3(fd_file_, fd_dup, 0));
#endif
  if (fd_dup >= 0) close(fd_dup);

  struct stat sb;
  EXPECT_OK(fstat(fd_file_, &sb));
  EXPECT_OK(lseek(fd_file_, 0, SEEK_SET));
  char ch;
  EXPECT_OK(read(fd_file_, &ch, sizeof(ch)));
  EXPECT_OK(write(fd_file_, &ch, sizeof(ch)));

#ifdef HAVE_CHFLAGS
  rc = fchflags(fd_file_, UF_NODUMP);
  if (rc < 0) {
    EXPECT_NE(ECAPMODE, errno);
  }
#endif

  char buf[1024];
  rc = getdents_(fd_dir_, (void*)buf, sizeof(buf));
  EXPECT_OK(rc);

  char data[] = "123";
  EXPECT_OK(pwrite(fd_file_, data, 1, 0));
  EXPECT_OK(pread(fd_file_, data, 1, 0));

  struct iovec io;
  io.iov_base = data;
  io.iov_len = 2;
#if !defined(__i386__) && !defined(__linux__)
  // TODO(drysdale): reinstate these tests for 32-bit runs when possible
  // libc bug is fixed.
  EXPECT_OK(pwritev(fd_file_, &io, 1, 0));
  EXPECT_OK(preadv(fd_file_, &io, 1, 0));
#endif
  EXPECT_OK(writev(fd_file_, &io, 1));
  EXPECT_OK(readv(fd_file_, &io, 1));

#ifdef HAVE_SYNCFS
  EXPECT_OK(syncfs(fd_file_));
#endif
#ifdef HAVE_SYNC_FILE_RANGE
  EXPECT_OK(sync_file_range(fd_file_, 0, 1, 0));
#endif
#ifdef HAVE_READAHEAD
  if (!tmpdir_on_tmpfs) {  // tmpfs doesn't support readahead(2)
    EXPECT_OK(readahead(fd_file_, 0, 1));
  }
#endif
}

FORK_TEST_F(WithFiles, AllowedSocketSyscalls) {
  EXPECT_OK(cap_enter());  // Enter capability mode.

  // recvfrom() either returns -1 with EAGAIN, or 0.
  int rc = recvfrom(fd_socket_, NULL, 0, MSG_DONTWAIT, NULL, NULL);
  if (rc < 0) {
    EXPECT_EQ(EAGAIN, errno);
  }
  char ch;
  EXPECT_OK(write(fd_file_, &ch, sizeof(ch)));

  // These calls will fail for lack of e.g. a proper name to send to,
  // but they are allowed in capability mode, so errno != ECAPMODE.
  EXPECT_FAIL_NOT_CAPMODE(accept(fd_socket_, NULL, NULL));
  EXPECT_FAIL_NOT_CAPMODE(getpeername(fd_socket_, NULL, NULL));
  EXPECT_FAIL_NOT_CAPMODE(getsockname(fd_socket_, NULL, NULL));
  EXPECT_FAIL_NOT_CAPMODE(recvmsg(fd_socket_, NULL, 0));
  EXPECT_FAIL_NOT_CAPMODE(sendmsg(fd_socket_, NULL, 0));
  EXPECT_FAIL_NOT_CAPMODE(sendto(fd_socket_, NULL, 0, 0, NULL, 0));
  off_t offset = 0;
  EXPECT_FAIL_NOT_CAPMODE(sendfile_(fd_socket_, fd_file_, &offset, 1));

  // The socket/socketpair syscalls are allowed, but they don't give
  // anything externally useful (can't call bind/connect on them).
  int fd_socket2 = socket(PF_INET, SOCK_DGRAM, 0);
  EXPECT_OK(fd_socket2);
  if (fd_socket2 >= 0) close(fd_socket2);
  int fd_pair[2] = {-1, -1};
  EXPECT_OK(socketpair(AF_UNIX, SOCK_STREAM, 0, fd_pair));
  if (fd_pair[0] >= 0) close(fd_pair[0]);
  if (fd_pair[1] >= 0) close(fd_pair[1]);
}

#ifdef HAVE_SEND_RECV_MMSG
FORK_TEST(Capmode, AllowedMmsgSendRecv) {
  int fd_socket = socket(PF_INET, SOCK_DGRAM, 0);

  struct sockaddr_in addr;
  addr.sin_family = AF_INET;
  addr.sin_port = htons(0);
  addr.sin_addr.s_addr = htonl(INADDR_ANY);
  EXPECT_OK(bind(fd_socket, (sockaddr*)&addr, sizeof(addr)));

  EXPECT_OK(cap_enter());  // Enter capability mode.

  char buffer[256] = {0};
  struct iovec iov;
  iov.iov_base = buffer;
  iov.iov_len = sizeof(buffer);
  struct mmsghdr mm;
  memset(&mm, 0, sizeof(mm));
  mm.msg_hdr.msg_iov = &iov;
  mm.msg_hdr.msg_iovlen = 1;
  struct timespec ts;
  ts.tv_sec = 1;
  ts.tv_nsec = 100;
  EXPECT_FAIL_NOT_CAPMODE(recvmmsg(fd_socket, &mm, 1, MSG_DONTWAIT, &ts));
  EXPECT_FAIL_NOT_CAPMODE(sendmmsg(fd_socket, &mm, 1, 0));
  close(fd_socket);
}
#endif

FORK_TEST(Capmode, AllowedIdentifierSyscalls) {
  // Record some identifiers
  gid_t my_gid = getgid();
  pid_t my_pid = getpid();
  pid_t my_ppid = getppid();
  uid_t my_uid = getuid();
  pid_t my_sid = getsid(my_pid);

  EXPECT_OK(cap_enter());  // Enter capability mode.

  EXPECT_EQ(my_gid, getegid_());
  EXPECT_EQ(my_uid, geteuid_());
  EXPECT_EQ(my_gid, getgid_());
  EXPECT_EQ(my_pid, getpid());
  EXPECT_EQ(my_ppid, getppid());
  EXPECT_EQ(my_uid, getuid_());
  EXPECT_EQ(my_sid, getsid(my_pid));
  gid_t grps[128];
  EXPECT_OK(getgroups_(128, grps));
  uid_t ruid;
  uid_t euid;
  uid_t suid;
  EXPECT_OK(getresuid(&ruid, &euid, &suid));
  gid_t rgid;
  gid_t egid;
  gid_t sgid;
  EXPECT_OK(getresgid(&rgid, &egid, &sgid));
#ifdef HAVE_GETLOGIN
  EXPECT_TRUE(getlogin() != NULL);
#endif

  // Set various identifiers (to their existing values).
  EXPECT_OK(setgid(my_gid));
#ifdef HAVE_SETFSGID
  EXPECT_OK(setfsgid(my_gid));
#endif
  EXPECT_OK(setuid(my_uid));
#ifdef HAVE_SETFSUID
  EXPECT_OK(setfsuid(my_uid));
#endif
  EXPECT_OK(setregid(my_gid, my_gid));
  EXPECT_OK(setresgid(my_gid, my_gid, my_gid));
  EXPECT_OK(setreuid(my_uid, my_uid));
  EXPECT_OK(setresuid(my_uid, my_uid, my_uid));
  EXPECT_OK(setsid());
}

FORK_TEST(Capmode, AllowedSchedSyscalls) {
  EXPECT_OK(cap_enter());  // Enter capability mode.
  int policy = sched_getscheduler(0);
  EXPECT_OK(policy);
  struct sched_param sp;
  EXPECT_OK(sched_getparam(0, &sp));
  if (policy >= 0 && (!SCHED_SETSCHEDULER_REQUIRES_ROOT || getuid() == 0)) {
    EXPECT_OK(sched_setscheduler(0, policy, &sp));
  }
  EXPECT_OK(sched_setparam(0, &sp));
  EXPECT_OK(sched_get_priority_max(policy));
  EXPECT_OK(sched_get_priority_min(policy));
  struct timespec ts;
  EXPECT_OK(sched_rr_get_interval(0, &ts));
  EXPECT_OK(sched_yield());
}


FORK_TEST(Capmode, AllowedTimerSyscalls) {
  EXPECT_OK(cap_enter());  // Enter capability mode.
  struct timespec ts;
  EXPECT_OK(clock_getres(CLOCK_REALTIME, &ts));
  EXPECT_OK(clock_gettime(CLOCK_REALTIME, &ts));
  struct itimerval itv;
  EXPECT_OK(getitimer(ITIMER_REAL, &itv));
  EXPECT_OK(setitimer(ITIMER_REAL, &itv, NULL));
  struct timeval tv;
  struct timezone tz;
  EXPECT_OK(gettimeofday(&tv, &tz));
  ts.tv_sec = 0;
  ts.tv_nsec = 1;
  EXPECT_OK(nanosleep(&ts, NULL));
}


FORK_TEST(Capmode, AllowedProfilSyscall) {
  EXPECT_OK(cap_enter());  // Enter capability mode.
  char sbuf[32];
  EXPECT_OK(profil((profil_arg1_t*)sbuf, sizeof(sbuf), 0, 1));
}


FORK_TEST(Capmode, AllowedResourceSyscalls) {
  EXPECT_OK(cap_enter());  // Enter capability mode.
  errno = 0;
  int rc = getpriority(PRIO_PROCESS, 0);
  EXPECT_EQ(0, errno);
  EXPECT_OK(setpriority(PRIO_PROCESS, 0, rc));
  struct rlimit rlim;
  EXPECT_OK(getrlimit_(RLIMIT_CORE, &rlim));
  EXPECT_OK(setrlimit(RLIMIT_CORE, &rlim));
  struct rusage ruse;
  EXPECT_OK(getrusage(RUSAGE_SELF, &ruse));
}

FORK_TEST(CapMode, AllowedMmapSyscalls) {
  // mmap() some memory.
  size_t mem_size = getpagesize();
  void *mem = mmap(NULL, mem_size, PROT_READ|PROT_WRITE, MAP_SHARED|MAP_ANONYMOUS, -1, 0);
  EXPECT_TRUE(mem != NULL);
  EXPECT_OK(cap_enter());  // Enter capability mode.

  EXPECT_OK(msync(mem, mem_size, MS_ASYNC));
  EXPECT_OK(madvise(mem, mem_size, MADV_NORMAL));
  unsigned char vec[2];
  EXPECT_OK(mincore_(mem, mem_size, vec));
  EXPECT_OK(mprotect(mem, mem_size, PROT_READ|PROT_WRITE));

  if (!MLOCK_REQUIRES_ROOT || getuid() == 0) {
    EXPECT_OK(mlock(mem, mem_size));
    EXPECT_OK(munlock(mem, mem_size));
    int rc = mlockall(MCL_CURRENT);
    if (rc != 0) {
      // mlockall may well fail with ENOMEM for non-root users, as the
      // default RLIMIT_MEMLOCK value isn't that big.
      EXPECT_NE(ECAPMODE, errno);
    }
    EXPECT_OK(munlockall());
  }
  // Unmap the memory.
  EXPECT_OK(munmap(mem, mem_size));
}

FORK_TEST(Capmode, AllowedPipeSyscalls) {
  EXPECT_OK(cap_enter());  // Enter capability mode
  int fd2[2];
  int rc = pipe(fd2);
  EXPECT_EQ(0, rc);

#ifdef HAVE_VMSPLICE
  char buf[11] = "0123456789";
  struct iovec iov;
  iov.iov_base = buf;
  iov.iov_len = sizeof(buf);
  EXPECT_FAIL_NOT_CAPMODE(vmsplice(fd2[0], &iov, 1, SPLICE_F_NONBLOCK));
#endif

  if (rc == 0) {
    close(fd2[0]);
    close(fd2[1]);
  };
#ifdef HAVE_PIPE2
  rc = pipe2(fd2, 0);
  EXPECT_EQ(0, rc);
  if (rc == 0) {
    close(fd2[0]);
    close(fd2[1]);
  };
#endif
}

TEST(Capmode, AllowedAtSyscalls) {
  int rc = mkdir(TmpFile("cap_at_syscalls"), 0755);
  EXPECT_OK(rc);
  if (rc < 0 && errno != EEXIST) return;
  int dfd = open(TmpFile("cap_at_syscalls"), O_RDONLY);
  EXPECT_OK(dfd);

  int file = openat(dfd, "testfile", O_RDONLY|O_CREAT, 0644);
  EXPECT_OK(file);
  EXPECT_OK(close(file));


  pid_t child = fork();
  if (child == 0) {
    // Child: enter cap mode and run tests
    EXPECT_OK(cap_enter());  // Enter capability mode

    struct stat fs;
    EXPECT_OK(fstatat(dfd, "testfile", &fs, 0));
    EXPECT_OK(mkdirat(dfd, "subdir", 0600));
    EXPECT_OK(fchmodat(dfd, "subdir", 0644, 0));
    EXPECT_OK(faccessat(dfd, "subdir", F_OK, 0));
    EXPECT_OK(renameat(dfd, "subdir", dfd, "subdir2"));
    EXPECT_OK(renameat(dfd, "subdir2", dfd, "subdir"));
    struct timeval tv[2];
    struct timezone tz;
    EXPECT_OK(gettimeofday(&tv[0], &tz));
    EXPECT_OK(gettimeofday(&tv[1], &tz));
    EXPECT_OK(futimesat(dfd, "testfile", tv));

    EXPECT_OK(fchownat(dfd, "testfile",  fs.st_uid, fs.st_gid, 0));
    EXPECT_OK(linkat(dfd, "testfile", dfd, "linky", 0));
    EXPECT_OK(symlinkat("testfile", dfd, "symlink"));
    char buffer[256];
    EXPECT_OK(readlinkat(dfd, "symlink", buffer, sizeof(buffer)));
    EXPECT_OK(unlinkat(dfd, "linky", 0));
    EXPECT_OK(unlinkat(dfd, "subdir", AT_REMOVEDIR));

    // Check that invalid requests get a non-Capsicum errno.
    errno = 0;
    rc = readlinkat(-1, "symlink", buffer, sizeof(buffer));
    EXPECT_GE(0, rc);
    EXPECT_NE(ECAPMODE, errno);

    exit(HasFailure());
  }

  // Wait for the child.
  int status;
  EXPECT_EQ(child, waitpid(child, &status, 0));
  rc = WIFEXITED(status) ? WEXITSTATUS(status) : -1;
  EXPECT_EQ(0, rc);

  // Tidy up.
  close(dfd);
  rmdir(TmpFile("cap_at_syscalls/subdir"));
  unlink(TmpFile("cap_at_syscalls/symlink"));
  unlink(TmpFile("cap_at_syscalls/linky"));
  unlink(TmpFile("cap_at_syscalls/testfile"));
  rmdir(TmpFile("cap_at_syscalls"));
}

TEST(Capmode, AllowedAtSyscallsCwd) {
  int rc = mkdir(TmpFile("cap_at_syscalls_cwd"), 0755);
  EXPECT_OK(rc);
  if (rc < 0 && errno != EEXIST) return;
  int dfd = open(TmpFile("cap_at_syscalls_cwd"), O_RDONLY);
  EXPECT_OK(dfd);

  int file = openat(dfd, "testfile", O_RDONLY|O_CREAT, 0644);
  EXPECT_OK(file);
  EXPECT_OK(close(file));

  pid_t child = fork();
  if (child == 0) {
    // Child: move into temp dir, enter cap mode and run tests
    EXPECT_OK(fchdir(dfd));
    EXPECT_OK(cap_enter());  // Enter capability mode

    // Test that *at(AT_FDCWD, path,...) is policed with ECAPMODE.
    EXPECT_CAPMODE(openat(AT_FDCWD, "testfile", O_RDONLY));
    struct stat fs;
    EXPECT_CAPMODE(fstatat(AT_FDCWD, "testfile", &fs, 0));
    EXPECT_CAPMODE(mkdirat(AT_FDCWD, "subdir", 0600));
    EXPECT_CAPMODE(fchmodat(AT_FDCWD, "subdir", 0644, 0));
    EXPECT_CAPMODE(faccessat(AT_FDCWD, "subdir", F_OK, 0));
    EXPECT_CAPMODE(renameat(AT_FDCWD, "subdir", AT_FDCWD, "subdir2"));
    EXPECT_CAPMODE(renameat(AT_FDCWD, "subdir2", AT_FDCWD, "subdir"));
    struct timeval tv[2];
    struct timezone tz;
    EXPECT_OK(gettimeofday(&tv[0], &tz));
    EXPECT_OK(gettimeofday(&tv[1], &tz));
    EXPECT_CAPMODE(futimesat(AT_FDCWD, "testfile", tv));

    EXPECT_CAPMODE(fchownat(AT_FDCWD, "testfile",  fs.st_uid, fs.st_gid, 0));
    EXPECT_CAPMODE(linkat(AT_FDCWD, "testfile", AT_FDCWD, "linky", 0));
    EXPECT_CAPMODE(symlinkat("testfile", AT_FDCWD, "symlink"));
    char buffer[256];
    EXPECT_CAPMODE(readlinkat(AT_FDCWD, "symlink", buffer, sizeof(buffer)));
    EXPECT_CAPMODE(unlinkat(AT_FDCWD, "linky", 0));

    exit(HasFailure());
  }

  // Wait for the child.
  int status;
  EXPECT_EQ(child, waitpid(child, &status, 0));
  rc = WIFEXITED(status) ? WEXITSTATUS(status) : -1;
  EXPECT_EQ(0, rc);

  // Tidy up.
  close(dfd);
  rmdir(TmpFile("cap_at_syscalls_cwd/subdir"));
  unlink(TmpFile("cap_at_syscalls_cwd/symlink"));
  unlink(TmpFile("cap_at_syscalls_cwd/linky"));
  unlink(TmpFile("cap_at_syscalls_cwd/testfile"));
  rmdir(TmpFile("cap_at_syscalls_cwd"));
}

TEST(Capmode, Abort) {
  // Check that abort(3) works even in capability mode.
  pid_t child = fork();
  if (child == 0) {
    // Child: enter capability mode and call abort(3).
    // Triggers something like kill(getpid(), SIGABRT).
    cap_enter();  // Enter capability mode.
    abort();
    exit(99);
  }
  int status;
  EXPECT_EQ(child, waitpid(child, &status, 0));
  EXPECT_TRUE(WIFSIGNALED(status)) << " status = " << std::hex << status;
  EXPECT_EQ(SIGABRT, WTERMSIG(status)) << " status = " << std::hex << status;
}

FORK_TEST_F(WithFiles, AllowedMiscSyscalls) {
  umask(022);
  mode_t um_before = umask(022);
  EXPECT_OK(cap_enter());  // Enter capability mode.

  mode_t um = umask(022);
  EXPECT_NE(-ECAPMODE, (int)um);
  EXPECT_EQ(um_before, um);
  stack_t ss;
  EXPECT_OK(sigaltstack(NULL, &ss));

  // Finally, tests for system calls that don't fit the pattern very well.
  pid_t pid = fork();
  EXPECT_OK(pid);
  if (pid == 0) {
    // Child: almost immediately exit.
    sleep(1);
    exit(0);
  } else if (pid > 0) {
    errno = 0;
    EXPECT_CAPMODE(ptrace_(PTRACE_PEEKDATA_, pid, &pid, NULL));
    EXPECT_CAPMODE(waitpid(pid, NULL, 0));
  }

  // No error return from sync(2) to test, but check errno remains unset.
  errno = 0;
  sync();
  EXPECT_EQ(0, errno);

  // TODO(FreeBSD): ktrace

#ifdef HAVE_SYSARCH
  // sysarch() is, by definition, architecture-dependent
#if defined (__amd64__) || defined (__i386__)
  long sysarch_arg = 0;
  EXPECT_CAPMODE(sysarch(I386_SET_IOPERM, &sysarch_arg));
#else
  // TOOD(jra): write a test for other architectures, like arm
#endif
#endif
}

void *thread_fn(void *p) {
  int delay = *(int *)p;
  sleep(delay);
  EXPECT_OK(getpid_());
  EXPECT_CAPMODE(open("/dev/null", O_RDWR));
  return NULL;
}

// Check that restrictions are the same in subprocesses and threads
FORK_TEST(Capmode, NewThread) {
  // Fire off a new thread before entering capability mode
  pthread_t early_thread;
  int one = 1;  // second
  EXPECT_OK(pthread_create(&early_thread, NULL, thread_fn, &one));

  // Fire off a new process before entering capability mode.
  int early_child = fork();
  EXPECT_OK(early_child);
  if (early_child == 0) {
    // Child: wait and then confirm this process is unaffect by capability mode in the parent.
    sleep(1);
    int fd = open("/dev/null", O_RDWR);
    EXPECT_OK(fd);
    close(fd);
    exit(0);
  }

  EXPECT_OK(cap_enter());  // Enter capability mode.
  // Do an allowed syscall.
  EXPECT_OK(getpid_());
  int child = fork();
  EXPECT_OK(child);
  if (child == 0) {
    // Child: do an allowed and a disallowed syscall.
    EXPECT_OK(getpid_());
    EXPECT_CAPMODE(open("/dev/null", O_RDWR));
    exit(0);
  }
  // Don't (can't) wait for either child.

  // Wait for the early-started thread.
  EXPECT_OK(pthread_join(early_thread, NULL));

  // Fire off a new thread.
  pthread_t child_thread;
  int zero = 0; // seconds
  EXPECT_OK(pthread_create(&child_thread, NULL, thread_fn, &zero));
  EXPECT_OK(pthread_join(child_thread, NULL));

  // Fork a subprocess which fires off a new thread.
  child = fork();
  EXPECT_OK(child);
  if (child == 0) {
    pthread_t child_thread2;
    EXPECT_OK(pthread_create(&child_thread2, NULL, thread_fn, &zero));
    EXPECT_OK(pthread_join(child_thread2, NULL));
    exit(0);
  }
  // Sleep for a bit to allow the subprocess to finish.
  sleep(2);
}

static int had_signal = 0;
static void handle_signal(int) { had_signal = 1; }

FORK_TEST(Capmode, SelfKill) {
  pid_t me = getpid();
  sighandler_t original = signal(SIGUSR1, handle_signal);

  pid_t child = fork();
  if (child == 0) {
    // Child: sleep and exit
    sleep(1);
    exit(0);
  }

  EXPECT_OK(cap_enter());  // Enter capability mode.

  // Can only kill(2) to own pid.
  EXPECT_CAPMODE(kill(child, SIGUSR1));
  EXPECT_OK(kill(me, SIGUSR1));
  EXPECT_EQ(1, had_signal);

  signal(SIGUSR1, original);
}