src/network/rootbind.c

   1 /*****************************************************************************
   2  * rootbind.c: bind to reserved ports through the root wrapper
   3  *****************************************************************************
   4  * Copyright © 2005-2008 Rémi Denis-Courmont
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  19  *****************************************************************************/
  20
  21 #if HAVE_CONFIG_H
  22 # include <config.h>
  23 #endif
  24
  25 #if !defined (WIN32) && !defined (SYS_BEOS)
  26 # define ENABLE_ROOTWRAP 1
  27 #endif
  28
  29 #include <stddef.h>
  30 struct sockaddr;
  31 int rootwrap_bind (int, int, int, const struct sockaddr *, size_t);
  32
  33 #include <errno.h>
  34
  35 #ifdef ENABLE_ROOTWRAP
  36
  37 #include <string.h>
  38 #include <stdlib.h>
  39
  40 #include <sys/types.h>
  41 #include <unistd.h>
  42 #include <sys/socket.h>
  43 #include <sys/uio.h>
  44 #include <sys/un.h>
  45 #include <netinet/in.h>
  46 #include <pthread.h>
  47
  48 /**
  49  * Receive a file descriptor from another process
  50  */
  51 static int recv_fd (int p)
  52 {
  53     struct msghdr hdr;
  54     struct iovec iov;
  55     struct cmsghdr *cmsg;
  56     int val, fd;
  57     char buf[CMSG_SPACE (sizeof (fd))];
  58
  59     hdr.msg_name = NULL;
  60     hdr.msg_namelen = 0;
  61     hdr.msg_iov = &iov;
  62     hdr.msg_iovlen = 1;
  63     hdr.msg_control = buf;
  64     hdr.msg_controllen = sizeof (buf);
  65
  66     iov.iov_base = &val;
  67     iov.iov_len = sizeof (val);
  68
  69     if (recvmsg (p, &hdr, 0) != sizeof (val))
  70         return -1;
  71
  72     for (cmsg = CMSG_FIRSTHDR (&hdr); cmsg != NULL;
  73          cmsg = CMSG_NXTHDR (&hdr, cmsg))
  74     {
  75         if ((cmsg->cmsg_level == SOL_SOCKET)
  76          && (cmsg->cmsg_type = SCM_RIGHTS)
  77          && (cmsg->cmsg_len >= CMSG_LEN (sizeof (fd))))
  78         {
  79             memcpy (&fd, CMSG_DATA (cmsg), sizeof (fd));
  80             return fd;
  81         }
  82     }
  83
  84     errno = val;
  85     return -1;
  86 }
  87
  88 /**
  89  * Tries to obtain a bound TCP socket from the root process
  90  */
  91 int rootwrap_bind (int family, int socktype, int protocol,
  92                    const struct sockaddr *addr, size_t alen)
  93 {
  94     /* can't use libvlc */
  95     static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
  96     struct sockaddr_storage ss;
  97     int fd, sock = -1;
  98
  99     const char *sockenv = getenv ("VLC_ROOTWRAP_SOCK");
 100     if (sockenv != NULL)
 101         sock = atoi (sockenv);
 102     if (sock == -1)
 103     {
 104         errno = EACCES;
 105         return -1;
 106     }
 107
 108     switch (family)
 109     {
 110         case AF_INET:
 111             if (alen < sizeof (struct sockaddr_in))
 112             {
 113                 errno = EINVAL;
 114                 return -1;
 115             }
 116             break;
 117
 118 #ifdef AF_INET6
 119         case AF_INET6:
 120             if (alen < sizeof (struct sockaddr_in6))
 121             {
 122                 errno = EINVAL;
 123                 return -1;
 124             }
 125             break;
 126 #endif
 127
 128         default:
 129             errno = EAFNOSUPPORT;
 130             return -1;
 131     }
 132
 133     if (family != addr->sa_family)
 134     {
 135         errno = EAFNOSUPPORT;
 136         return -1;
 137     }
 138
 139     /* Only TCP is implemented at the moment */
 140     if ((socktype != SOCK_STREAM)
 141      || (protocol && (protocol != IPPROTO_TCP)))
 142     {
 143         errno = EACCES;
 144         return -1;
 145     }
 146
 147     memset (&ss, 0, sizeof (ss));
 148     memcpy (&ss, addr, (alen > sizeof (ss)) ? sizeof (ss) : alen);
 149
 150     pthread_mutex_lock (&mutex);
 151     if (send (sock, &ss, sizeof (ss), 0) != sizeof (ss))
 152         return -1;
 153
 154     fd = recv_fd (sock);
 155     pthread_mutex_unlock (&mutex);
 156     return fd;
 157 }
 158
 159 #else
 160 int rootwrap_bind (int family, int socktype, int protocol,
 161                    const struct sockaddr *addr, size_t alen)
 162 {
 163     (void)family;
 164     (void)socktype;
 165     (void)protocol;
 166     (void)addr;
 167     (void)alen;
 168     errno = EACCES;
 169     return -1;
 170 }
 171
 172 #endif /* ENABLE_ROOTWRAP */