text: /*****************************************************************************
   * rootbind.c: bind to reserved ports through the root wrapper
   *****************************************************************************
   * Copyright © 2005-2008 Rémi Denis-Courmont
   *
   * This program is free software; you can redistribute it and/or modify it
   * under the terms of the GNU Lesser General Public License as published by
   * the Free Software Foundation; either version 2.1 of the License, or
   * (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
   * GNU Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public License
   * along with this program; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
   *****************************************************************************/
  
  #ifdef HAVE_CONFIG_H
  # include <config.h>
  #endif
  
  #define _XPG4_2 /* ancillary data on Solaris */
  
  #if !defined (_WIN32) && !defined (__OS2__)
  # define ENABLE_ROOTWRAP 1
  #endif
  
  #include <stddef.h>
  struct sockaddr;
  int rootwrap_bind (int, int, int, const struct sockaddr *, size_t);
  
  #include <errno.h>
  
  #ifdef ENABLE_ROOTWRAP
  
  #include <string.h>
  #include <stdlib.h>
  
  #include <sys/types.h>
  #include <unistd.h>
  #include <sys/socket.h>
  #include <sys/uio.h>
  #include <sys/un.h>
  #include <netinet/in.h>
  #include <pthread.h>
  
  /* Required yet non-standard cmsg functions */
  #ifndef CMSG_ALIGN
  # define CMSG_ALIGN(len) (((len) + sizeof(intptr_t)-1) & ~(sizeof(intptr_t)-1))
  #endif
  #ifndef CMSG_SPACE
  # define CMSG_SPACE(len) (CMSG_ALIGN(sizeof(struct cmsghdr)) + CMSG_ALIGN(len))
  #endif
  #ifndef CMSG_LEN
  # define CMSG_LEN(len) (CMSG_ALIGN(sizeof(struct cmsghdr)) + (len))
  #endif
  #if !defined(MSG_NOSIGNAL)
  /* If the other end of the pipe hangs up and MSG_NOSIGNAL is missing, the
   * process will get a (likely fatal) SIGPIPE signal. Then again, the other end
   * can screw us up in various ways already (e.g. not answer to deadlock). */
  # define MSG_NOSIGNAL 0
  #endif
  
  #if defined(__OS2__) && !defined(ALIGN)
  /* CMSG_NXTHDR requires this */
  # define ALIGN(p) _ALIGN(p)
  #endif
  
  /**
   * Receive a file descriptor from another process
   */
  static int recv_fd (int p)
  {
      struct msghdr hdr;
      struct iovec iov;
      struct cmsghdr *cmsg;
      int val, fd;
      char buf[CMSG_SPACE (sizeof (fd))];
  
      hdr.msg_name = NULL;
      hdr.msg_namelen = 0;
      hdr.msg_iov = &iov;
      hdr.msg_iovlen = 1;
      hdr.msg_control = buf;
      hdr.msg_controllen = sizeof (buf);
  
      iov.iov_base = &val;
      iov.iov_len = sizeof (val);
  
      if (recvmsg (p, &hdr, 0) != sizeof (val))
          return -1;
  
      for (cmsg = CMSG_FIRSTHDR (&hdr); cmsg != NULL;
           cmsg = CMSG_NXTHDR (&hdr, cmsg))
      {
          if ((cmsg->cmsg_level == SOL_SOCKET)
           && (cmsg->cmsg_type == SCM_RIGHTS)
           && (cmsg->cmsg_len >= CMSG_LEN (sizeof (fd))))
          {
              memcpy (&fd, CMSG_DATA (cmsg), sizeof (fd));
              return fd;
          }
      }
  
      errno = val;
      return -1;
  }
  
  /**
   * Tries to obtain a bound TCP socket from the root process
   */
  int rootwrap_bind (int family, int socktype, int protocol,
                     const struct sockaddr *addr, size_t alen)
  {
      /* can't use libvlc */
      static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
      struct sockaddr_storage ss;
      int fd, sock = -1;
  
      const char *sockenv = getenv ("VLC_ROOTWRAP_SOCK");
      if (sockenv != NULL)
          sock = atoi (sockenv);
      if (sock == -1)
      {
          errno = EACCES;
          return -1;
      }
  
      switch (family)
      {
          case AF_INET:
              if (alen < sizeof (struct sockaddr_in))
              {
                  errno = EINVAL;
                  return -1;
              }
              break;
  
  #ifdef AF_INET6
          case AF_INET6:
              if (alen < sizeof (struct sockaddr_in6))
              {
                  errno = EINVAL;
                  return -1;
              }
              break;
  #endif
  
          default:
              errno = EAFNOSUPPORT;
              return -1;
      }
  
      if (family != addr->sa_family)
      {
          errno = EAFNOSUPPORT;
          return -1;
      }
  
      /* Only TCP is implemented at the moment */
      if ((socktype != SOCK_STREAM)
       || (protocol && (protocol != IPPROTO_TCP)))
      {
          errno = EACCES;
          return -1;
      }
  
      memset (&ss, 0, sizeof (ss));
      memcpy (&ss, addr, (alen > sizeof (ss)) ? sizeof (ss) : alen);
  
      pthread_mutex_lock (&mutex);
      if (send (sock, &ss, sizeof (ss), MSG_NOSIGNAL) != sizeof (ss))
      {
          pthread_mutex_unlock (&mutex);
          return -1;
      }
  
      fd = recv_fd (sock);
      pthread_mutex_unlock (&mutex);
      return fd;
  }
  
  #else
  int rootwrap_bind (int family, int socktype, int protocol,
                     const struct sockaddr *addr, size_t alen)
  {
      (void)family;
      (void)socktype;
      (void)protocol;
      (void)addr;
      (void)alen;
      errno = EACCES;
      return -1;
  }
  
  #endif /* ENABLE_ROOTWRAP */
  