SECCOMP-BPF: Refactor the BPF sandbox API to use fewer "static" fields and methods.

sandbox/linux/seccomp-bpf/util.cc

-// Copyright (c) 2012 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include <dirent.h>
-#include <errno.h>
-#include <fcntl.h>
-#include <stdarg.h>
-#include <stdlib.h>
-#include <string.h>
-#include <sys/socket.h>
-#include <sys/types.h>
-#include <unistd.h>
-
-#include "sandbox/linux/seccomp-bpf/sandbox_bpf.h"
-#include "sandbox/linux/seccomp-bpf/util.h"
-
-namespace playground2 {
-
-bool Util::SendFds(int transport, const void *buf, size_t len, ...) {
-  int count = 0;
-  va_list ap;
-  va_start(ap, len);
-  while (va_arg(ap, int) >= 0) {
-    ++count;
-  }
-  va_end(ap);
-  if (!count) {
-    return false;
-  }
-  char cmsg_buf[CMSG_SPACE(count*sizeof(int))];
-  memset(cmsg_buf, 0, sizeof(cmsg_buf));
-  struct iovec  iov[2] = { { 0 } };
-  struct msghdr msg    = { 0 };
-  int dummy            = 0;
-  iov[0].iov_base      = &dummy;
-  iov[0].iov_len       = sizeof(dummy);
-  if (buf && len > 0) {
-    iov[1].iov_base    = const_cast<void *>(buf);
-    iov[1].iov_len     = len;
-  }
-  msg.msg_iov          = iov;
-  msg.msg_iovlen       = (buf && len > 0) ? 2 : 1;
-  msg.msg_control      = cmsg_buf;
-  msg.msg_controllen   = CMSG_LEN(count*sizeof(int));
-  struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
-  cmsg->cmsg_level     = SOL_SOCKET;
-  cmsg->cmsg_type      = SCM_RIGHTS;
-  cmsg->cmsg_len       = CMSG_LEN(count*sizeof(int));
-  va_start(ap, len);
-  for (int i = 0, fd; (fd = va_arg(ap, int)) >= 0; ++i) {
-    (reinterpret_cast<int *>(CMSG_DATA(cmsg)))[i] = fd;
-  }
-  return sendmsg(transport, &msg, 0) ==
-      static_cast<ssize_t>(sizeof(dummy) + ((buf && len > 0) ? len : 0));
-}
-
-bool Util::GetFds(int transport, void *buf, size_t *len, ...) {
-  int count = 0;
-  va_list ap;
-  va_start(ap, len);
-  for (int *fd; (fd = va_arg(ap, int *)) != NULL; ++count) {
-    *fd = -1;
-  }
-  va_end(ap);
-  if (!count) {
-    return false;
-  }
-  char cmsg_buf[CMSG_SPACE(count*sizeof(int))];
-  memset(cmsg_buf, 0, sizeof(cmsg_buf));
-  struct iovec iov[2] = { { 0 } };
-  struct msghdr msg   = { 0 };
-  int err;
-  iov[0].iov_base     = &err;
-  iov[0].iov_len      = sizeof(int);
-  if (buf && len && *len > 0) {
-    iov[1].iov_base   = buf;
-    iov[1].iov_len    = *len;
-  }
-  msg.msg_iov         = iov;
-  msg.msg_iovlen      = (buf && len && *len > 0) ? 2 : 1;
-  msg.msg_control     = cmsg_buf;
-  msg.msg_controllen  = CMSG_LEN(count*sizeof(int));
-  ssize_t bytes = recvmsg(transport, &msg, 0);
-  if (len) {
-    *len = bytes > static_cast<int>(sizeof(int)) ? bytes - sizeof(int) : 0;
-  }
-  if (bytes != static_cast<ssize_t>(sizeof(int) + iov[1].iov_len)) {
-    if (bytes >= 0) {
-      errno = 0;
-    }
-    return false;
-  }
-  if (err) {
-    // "err" is the first four bytes of the payload. If these are non-zero,
-    // the sender on the other side of the socketpair sent us an errno value.
-    // We don't expect to get any file handles in this case.
-    errno = err;
-    return false;
-  }
-  struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
-  if ((msg.msg_flags & (MSG_TRUNC|MSG_CTRUNC)) ||
-      !cmsg                                    ||
-      cmsg->cmsg_level != SOL_SOCKET           ||
-      cmsg->cmsg_type  != SCM_RIGHTS           ||
-      cmsg->cmsg_len   != CMSG_LEN(count*sizeof(int))) {
-    errno = EBADF;
-    return false;
-  }
-  va_start(ap, len);
-  for (int *fd, i = 0; (fd = va_arg(ap, int *)) != NULL; ++i) {
-    *fd = (reinterpret_cast<int *>(CMSG_DATA(cmsg)))[i];
-  }
-  va_end(ap);
-  return true;
-}
-
-void Util::CloseAllBut(int fd, ...) {
-  int proc_fd;
-  int fdir;
-  if ((proc_fd = Sandbox::proc_fd()) < 0 ||
-      (fdir = openat(proc_fd, "self/fd", O_RDONLY|O_DIRECTORY)) < 0) {
-    SANDBOX_DIE("Cannot access \"/proc/self/fd\"");
-  }
-  int dev_null = open("/dev/null", O_RDWR);
-  DIR *dir = fdopendir(fdir);
-  struct dirent de, *res;
-  while (!readdir_r(dir, &de, &res) && res) {
-    if (res->d_name[0] < '0') {
-      continue;
-    }
-    int i = atoi(res->d_name);
-    if (i >= 0 && i != dirfd(dir) && i != dev_null) {
-      va_list ap;
-      va_start(ap, fd);
-      for (int f = fd;; f = va_arg(ap, int)) {
-        if (f < 0) {
-          if (i <= 2) {
-            // Never ever close 0..2. If we cannot redirect to /dev/null,
-            // then we are better off leaving the standard descriptors open.
-            if (dev_null >= 0) {
-              if (HANDLE_EINTR(dup2(dev_null, i))) {
-                SANDBOX_DIE("Cannot dup2()");
-              }
-            }
-          } else {
-            if (HANDLE_EINTR(close(i))) { }
-          }
-          break;
-        } else if (i == f) {
-          break;
-        }
-      }
-      va_end(ap);
-    }
-  }
-  closedir(dir);
-  if (dev_null >= 0) {
-    if (HANDLE_EINTR(close(dev_null))) { }
-  }
-  return;
-}
-
-}  // namespace