Initial snapshot of the new BPF-enabled seccomp sandbox. This code is

sandbox/linux/seccomp_bpf/demo.cc

+#include <errno.h>
+#include <fcntl.h>
+#include <linux/unistd.h>
+#include <netinet/in.h>
+#include <netinet/tcp.h>
+#include <netinet/udp.h>
+#include <pthread.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/ipc.h>
+#include <sys/mman.h>
+#include <sys/prctl.h>
+#include <sys/resource.h>
+#include <sys/shm.h>
+#include <sys/socket.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <time.h>
+#include <unistd.h>
+
+#include "sandbox/linux/seccomp_bpf/sandbox_bpf.h"
+#include "sandbox/linux/seccomp_bpf/util.h"
+
+#define ERR EPERM
+
+// We don't expect our sandbox to do anything useful yet. So, we will fail
+// almost immediately. For now, force the code to continue running. The
+// following line should be removed as soon as the sandbox is starting to
+// actually enforce restrictions in a meaningful way:
+#define _exit(x) do { } while (0)
+
+static playground2::Sandbox::ErrorCode evaluator(int sysno) {
+  switch (sysno) {
+  #if defined(__NR_accept)
+    case __NR_accept: case __NR_accept4:
+#endif
+    case __NR_alarm:
+    case __NR_brk:
+    case __NR_clock_gettime:
+    case __NR_close:
+    case __NR_dup: case __NR_dup2:
+    case __NR_epoll_create: case __NR_epoll_ctl: case __NR_epoll_wait:
+    case __NR_exit: case __NR_exit_group:
+    case __NR_fcntl:
+#if defined(__NR_fcntl64)
+    case __NR_fcntl64:
+#endif
+    case __NR_fdatasync:
+    case __NR_fstat:
+#if defined(__NR_fstat64)
+    case __NR_fstat64:
+#endif
+    case __NR_ftruncate:
+    case __NR_futex:
+    case __NR_getdents: case __NR_getdents64:
+    case __NR_getegid:
+#if defined(__NR_getegid32)
+    case __NR_getegid32:
+#endif
+    case __NR_geteuid:
+#if defined(__NR_geteuid32)
+    case __NR_geteuid32:
+#endif
+    case __NR_getgid:
+#if defined(__NR_getgid32)
+    case __NR_getgid32:
+#endif
+    case __NR_getitimer: case __NR_setitimer:
+#if defined(__NR_getpeername)
+    case __NR_getpeername:
+#endif
+    case __NR_getpid: case __NR_gettid:
+#if defined(__NR_getsockname)
+    case __NR_getsockname:
+#endif
+    case __NR_gettimeofday:
+    case __NR_getuid:
+#if defined(__NR_getuid32)
+    case __NR_getuid32:
+#endif
+#if defined(__NR__llseek)
+    case __NR__llseek:
+#endif
+    case __NR_lseek:
+    case __NR_nanosleep:
+    case __NR_pipe: case __NR_pipe2:
+    case __NR_poll:
+    case __NR_pread64: case __NR_preadv:
+    case __NR_pwrite64: case __NR_pwritev:
+    case __NR_read: case __NR_readv:
+    case __NR_restart_syscall:
+    case __NR_set_robust_list:
+    case __NR_rt_sigaction:
+#if defined(__NR_sigaction)
+    case __NR_sigaction:
+#endif
+#if defined(__NR_signal)
+    case __NR_signal:
+#endif
+    case __NR_rt_sigprocmask:
+#if defined(__NR_sigprocmask)
+    case __NR_sigprocmask:
+#endif
+#if defined(__NR_shutdown)
+    case __NR_shutdown:
+#endif
+    case __NR_rt_sigreturn:
+#if defined(__NR_sigreturn)
+    case __NR_sigreturn:
+#endif
+#if defined(__NR_socketpair)
+    case __NR_socketpair:
+#endif
+    case __NR_time:
+    case __NR_uname:
+    case __NR_write: case __NR_writev:
+      return playground2::Sandbox::SB_ALLOWED;
+
+  // The following system calls are temporarily permitted. This must be
+  // tightened later. But we currently don't implement enough of the sandboxing
+  // API to do so.
+  // As is, this sandbox isn't exactly safe :-/
+#if defined(__NR_sendmsg)
+  case __NR_sendmsg: case __NR_sendto:
+  case __NR_recvmsg: case __NR_recvfrom:
+  case __NR_getsockopt: case __NR_setsockopt:
+#elif defined(__NR_socketcall)
+  case __NR_socketcall:
+#endif
+#if defined(__NR_shmat)
+  case __NR_shmat: case __NR_shmctl: case __NR_shmdt: case __NR_shmget:
+#elif defined(__NR_ipc)
+  case __NR_ipc:
+#endif
+#if defined(__NR_mmap2)
+  case __NR_mmap2:
+#else
+  case __NR_mmap:
+#endif
+#if defined(__NR_ugetrlimit)
+  case __NR_ugetrlimit:
+#endif
+  case __NR_getrlimit:
+  case __NR_ioctl:
+  case __NR_prctl:
+  case __NR_clone:
+  case __NR_munmap: case __NR_mprotect: case __NR_madvise:
+  case __NR_remap_file_pages:
+      return playground2::Sandbox::SB_ALLOWED;
+
+  // Everything that isn't explicitly allowed is denied.
+  default:
+    return (playground2::Sandbox::ErrorCode)ERR;
+  }
+}
+
+static void *threadFnc(void *arg) {
+  return arg;
+}
+
+static void *sendmsgStressThreadFnc(void *arg) {
+  static const int repetitions = 100;
+  static const int kNumFds = 3;
+  for (int rep = 0; rep < repetitions; ++rep) {
+    int fds[2 + kNumFds];
+    if (socketpair(AF_UNIX, SOCK_STREAM, 0, fds)) {
+      perror("socketpair()");
+      _exit(1);
+    }
+    size_t len = 4;
+    char buf[4];
+    if (!playground2::Util::sendFds(fds[0], "test", 4,
+                                    fds[1], fds[1], fds[1], -1) ||
+        !playground2::Util::getFds(fds[1], buf, &len,
+                                   fds+2, fds+3, fds+4, NULL) ||
+        len != 4 ||
+        memcmp(buf, "test", len) ||
+        write(fds[2], "demo", 4) != 4 ||
+        read(fds[0], buf, 4) != 4 ||
+        memcmp(buf, "demo", 4)) {
+      perror("sending/receiving of fds");
+      _exit(1);
+    }
+    for (int i = 0; i < 2+kNumFds; ++i) {
+      if (close(fds[i])) {
+        perror("close");
+        _exit(1);
+      }
+    }
+  }
+  return NULL;
+}
+
+int main(int argc, char *argv[]) {
+  int proc_fd = open("/proc", O_RDONLY|O_DIRECTORY);
+  if (!playground2::Sandbox::supportsSeccompSandbox(proc_fd)) {
+    perror("sandbox");
+    _exit(1);
+  }
+  playground2::Sandbox::setProcFd(proc_fd);
+  playground2::Sandbox::setSandboxPolicy(evaluator, NULL);
+  playground2::Sandbox::startSandbox();
+
+  // Check that we can create threads
+  pthread_t thr;
+  if (!pthread_create(&thr, NULL, threadFnc,
+                      reinterpret_cast<void *>(0x1234))) {
+    void *ret;
+    pthread_join(thr, &ret);
+    if (ret != reinterpret_cast<void *>(0x1234)) {
+      perror("clone() failed");
+      _exit(1);
+    }
+  } else {
+    perror("clone() failed");
+    _exit(1);
+  }
+
+  // Check that we handle restart_syscall() without dieing. This is a little
+  // tricky to trigger. And I can't think of a good way to verify whether it
+  // actually executed.
+  signal(SIGALRM, SIG_IGN);
+  const struct itimerval tv = { { 0, 0 }, { 0, 5*1000 } };
+  const struct timespec tmo = { 0, 100*1000*1000 };
+  setitimer(ITIMER_REAL, &tv, NULL);
+  nanosleep(&tmo, NULL);
+
+  // Check that we can query the size of the stack, but that all other
+  // calls to getrlimit() fail.
+  if (((errno = 0), !getrlimit(RLIMIT_STACK, NULL)) || errno != EFAULT ||
+      ((errno = 0), !getrlimit(RLIMIT_CORE,  NULL)) || errno != ERR) {
+    perror("getrlimit()");
+    _exit(1);
+  }
+
+  // Check that we can query TCGETS and TIOCGWINSZ, but no other ioctls().
+  if (((errno = 0), !ioctl(2, TCGETS,     NULL)) || errno != EFAULT ||
+      ((errno = 0), !ioctl(2, TIOCGWINSZ, NULL)) || errno != EFAULT ||
+      ((errno = 0), !ioctl(2, TCSETS,     NULL)) || errno != ERR) {
+    perror("ioctl()");
+    _exit(1);
+  }
+
+  // Check that prctl() can manipulate the dumpable flag, but nothing else.
+  if (((errno = 0), !prctl(PR_GET_DUMPABLE))    || errno ||
+      ((errno = 0),  prctl(PR_SET_DUMPABLE, 1)) || errno ||
+      ((errno = 0), !prctl(PR_SET_SECCOMP,  0)) || errno != ERR) {
+    perror("prctl()");
+    _exit(1);
+  }
+
+  // Check that we can send and receive file handles.
+  int fds[3];
+  if (socketpair(AF_UNIX, SOCK_STREAM, 0, fds)) {
+    perror("socketpair()");
+    _exit(1);
+  }
+  size_t len = 4;
+  char buf[4];
+  if (!playground2::Util::sendFds(fds[0], "test", 4, fds[1], -1) ||
+      !playground2::Util::getFds(fds[1], buf, &len, fds+2, NULL) ||
+      len != 4 ||
+      memcmp(buf, "test", len) ||
+      write(fds[2], "demo", 4) != 4 ||
+      read(fds[0], buf, 4) != 4 ||
+      memcmp(buf, "demo", 4) ||
+      close(fds[0]) ||
+      close(fds[1]) ||
+      close(fds[2])) {
+    perror("sending/receiving of fds");
+    _exit(1);
+  }
+
+  // Check whether SysV IPC works.
+  int shmid;
+  void *addr;
+  if ((shmid = shmget(IPC_PRIVATE, 4096, IPC_CREAT|0600)) < 0 ||
+      (addr = shmat(shmid, NULL, 0)) == reinterpret_cast<void *>(-1) ||
+      shmdt(addr) ||
+      shmctl(shmid, IPC_RMID, NULL)) {
+    perror("sysv IPC");
+    _exit(1);
+  }
+
+  // Print a message so that the user can see the sandbox is activated.
+  time_t tm = time(NULL);
+  printf("Sandbox has been started at %s", ctime(&tm));
+
+  // Stress-test the sendmsg() code
+  static const int kSendmsgStressNumThreads = 10;
+  pthread_t sendmsgStressThreads[kSendmsgStressNumThreads];
+  for (int i = 0; i < kSendmsgStressNumThreads; ++i) {
+    if (pthread_create(sendmsgStressThreads + i, NULL,
+                       sendmsgStressThreadFnc, NULL)) {
+      perror("pthread_create");
+      _exit(1);
+    }
+  }
+  for (int i = 0; i < kSendmsgStressNumThreads; ++i) {
+    pthread_join(sendmsgStressThreads[i], NULL);
+  }
+
+  return 0;
+}