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 #ifdef 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 /* Required yet non-standard cmsg functions */
  49 #ifndef CMSG_ALIGN
  50 # define CMSG_ALIGN(len) (((len) + sizeof(intptr_t)-1) & ~(sizeof(intptr_t)-1))
  51 #endif
  52 #ifndef CMSG_SPACE
  53 # define CMSG_SPACE(len) (CMSG_ALIGN(sizeof(struct cmsghdr)) + CMSG_ALIGN(len))
  54 #endif
  55 #ifndef CMSG_LEN
  56 # define CMSG_LEN(len) (CMSG_ALIGN(sizeof(struct cmsghdr)) + (len))
  57 #endif
  58
  59 /**
  60  * Receive a file descriptor from another process
  61  */
  62 static int recv_fd (int p)
  63 {
  64     struct msghdr hdr;
  65     struct iovec iov;
  66     struct cmsghdr *cmsg;
  67     int val, fd;
  68     char buf[CMSG_SPACE (sizeof (fd))];
  69
  70     hdr.msg_name = NULL;
  71     hdr.msg_namelen = 0;
  72     hdr.msg_iov = &iov;
  73     hdr.msg_iovlen = 1;
  74     hdr.msg_control = buf;
  75     hdr.msg_controllen = sizeof (buf);
  76
  77     iov.iov_base = &val;
  78     iov.iov_len = sizeof (val);
  79
  80     if (recvmsg (p, &hdr, 0) != sizeof (val))
  81         return -1;
  82
  83     for (cmsg = CMSG_FIRSTHDR (&hdr); cmsg != NULL;
  84          cmsg = CMSG_NXTHDR (&hdr, cmsg))
  85     {
  86         if ((cmsg->cmsg_level == SOL_SOCKET)
  87          && (cmsg->cmsg_type = SCM_RIGHTS)
  88          && (cmsg->cmsg_len >= CMSG_LEN (sizeof (fd))))
  89         {
  90             memcpy (&fd, CMSG_DATA (cmsg), sizeof (fd));
  91             return fd;
  92         }
  93     }
  94
  95     errno = val;
  96     return -1;
  97 }
  98
  99 /**
 100  * Tries to obtain a bound TCP socket from the root process
 101  */
 102 int rootwrap_bind (int family, int socktype, int protocol,
 103                    const struct sockaddr *addr, size_t alen)
 104 {
 105     /* can't use libvlc */
 106     static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
 107     struct sockaddr_storage ss;
 108     int fd, sock = -1;
 109
 110     const char *sockenv = getenv ("VLC_ROOTWRAP_SOCK");
 111     if (sockenv != NULL)
 112         sock = atoi (sockenv);
 113     if (sock == -1)
 114     {
 115         errno = EACCES;
 116         return -1;
 117     }
 118
 119     switch (family)
 120     {
 121         case AF_INET:
 122             if (alen < sizeof (struct sockaddr_in))
 123             {
 124                 errno = EINVAL;
 125                 return -1;
 126             }
 127             break;
 128
 129 #ifdef AF_INET6
 130         case AF_INET6:
 131             if (alen < sizeof (struct sockaddr_in6))
 132             {
 133                 errno = EINVAL;
 134                 return -1;
 135             }
 136             break;
 137 #endif
 138
 139         default:
 140             errno = EAFNOSUPPORT;
 141             return -1;
 142     }
 143
 144     if (family != addr->sa_family)
 145     {
 146         errno = EAFNOSUPPORT;
 147         return -1;
 148     }
 149
 150     /* Only TCP is implemented at the moment */
 151     if ((socktype != SOCK_STREAM)
 152      || (protocol && (protocol != IPPROTO_TCP)))
 153     {
 154         errno = EACCES;
 155         return -1;
 156     }
 157
 158     memset (&ss, 0, sizeof (ss));
 159     memcpy (&ss, addr, (alen > sizeof (ss)) ? sizeof (ss) : alen);
 160
 161     pthread_mutex_lock (&mutex);
 162     if (send (sock, &ss, sizeof (ss), 0) != sizeof (ss))
 163         return -1;
 164
 165     fd = recv_fd (sock);
 166     pthread_mutex_unlock (&mutex);
 167     return fd;
 168 }
 169
 170 #else
 171 int rootwrap_bind (int family, int socktype, int protocol,
 172                    const struct sockaddr *addr, size_t alen)
 173 {
 174     (void)family;
 175     (void)socktype;
 176     (void)protocol;
 177     (void)addr;
 178     (void)alen;
 179     errno = EACCES;
 180     return -1;
 181 }
 182
 183 #endif /* ENABLE_ROOTWRAP */