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 #define _XPG4_2 /* ancilliary data on Solaris */
  26
  27 #if !defined (WIN32) && !defined (SYS_BEOS)
  28 # define ENABLE_ROOTWRAP 1
  29 #endif
  30
  31 #include <stddef.h>
  32 struct sockaddr;
  33 int rootwrap_bind (int, int, int, const struct sockaddr *, size_t);
  34
  35 #include <errno.h>
  36
  37 #ifdef ENABLE_ROOTWRAP
  38
  39 #include <string.h>
  40 #include <stdlib.h>
  41
  42 #include <sys/types.h>
  43 #include <unistd.h>
  44 #include <sys/socket.h>
  45 #include <sys/uio.h>
  46 #include <sys/un.h>
  47 #include <netinet/in.h>
  48 #include <pthread.h>
  49
  50 /* Required yet non-standard cmsg functions */
  51 #ifndef CMSG_ALIGN
  52 # define CMSG_ALIGN(len) (((len) + sizeof(intptr_t)-1) & ~(sizeof(intptr_t)-1))
  53 #endif
  54 #ifndef CMSG_SPACE
  55 # define CMSG_SPACE(len) (CMSG_ALIGN(sizeof(struct cmsghdr)) + CMSG_ALIGN(len))
  56 #endif
  57 #ifndef CMSG_LEN
  58 # define CMSG_LEN(len) (CMSG_ALIGN(sizeof(struct cmsghdr)) + (len))
  59 #endif
  60
  61 /**
  62  * Receive a file descriptor from another process
  63  */
  64 static int recv_fd (int p)
  65 {
  66     struct msghdr hdr;
  67     struct iovec iov;
  68     struct cmsghdr *cmsg;
  69     int val, fd;
  70     char buf[CMSG_SPACE (sizeof (fd))];
  71
  72     hdr.msg_name = NULL;
  73     hdr.msg_namelen = 0;
  74     hdr.msg_iov = &iov;
  75     hdr.msg_iovlen = 1;
  76     hdr.msg_control = buf;
  77     hdr.msg_controllen = sizeof (buf);
  78
  79     iov.iov_base = &val;
  80     iov.iov_len = sizeof (val);
  81
  82     if (recvmsg (p, &hdr, 0) != sizeof (val))
  83         return -1;
  84
  85     for (cmsg = CMSG_FIRSTHDR (&hdr); cmsg != NULL;
  86          cmsg = CMSG_NXTHDR (&hdr, cmsg))
  87     {
  88         if ((cmsg->cmsg_level == SOL_SOCKET)
  89          && (cmsg->cmsg_type = SCM_RIGHTS)
  90          && (cmsg->cmsg_len >= CMSG_LEN (sizeof (fd))))
  91         {
  92             memcpy (&fd, CMSG_DATA (cmsg), sizeof (fd));
  93             return fd;
  94         }
  95     }
  96
  97     errno = val;
  98     return -1;
  99 }
 100
 101 /**
 102  * Tries to obtain a bound TCP socket from the root process
 103  */
 104 int rootwrap_bind (int family, int socktype, int protocol,
 105                    const struct sockaddr *addr, size_t alen)
 106 {
 107     /* can't use libvlc */
 108     static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
 109     struct sockaddr_storage ss;
 110     int fd, sock = -1;
 111
 112     const char *sockenv = getenv ("VLC_ROOTWRAP_SOCK");
 113     if (sockenv != NULL)
 114         sock = atoi (sockenv);
 115     if (sock == -1)
 116     {
 117         errno = EACCES;
 118         return -1;
 119     }
 120
 121     switch (family)
 122     {
 123         case AF_INET:
 124             if (alen < sizeof (struct sockaddr_in))
 125             {
 126                 errno = EINVAL;
 127                 return -1;
 128             }
 129             break;
 130
 131 #ifdef AF_INET6
 132         case AF_INET6:
 133             if (alen < sizeof (struct sockaddr_in6))
 134             {
 135                 errno = EINVAL;
 136                 return -1;
 137             }
 138             break;
 139 #endif
 140
 141         default:
 142             errno = EAFNOSUPPORT;
 143             return -1;
 144     }
 145
 146     if (family != addr->sa_family)
 147     {
 148         errno = EAFNOSUPPORT;
 149         return -1;
 150     }
 151
 152     /* Only TCP is implemented at the moment */
 153     if ((socktype != SOCK_STREAM)
 154      || (protocol && (protocol != IPPROTO_TCP)))
 155     {
 156         errno = EACCES;
 157         return -1;
 158     }
 159
 160     memset (&ss, 0, sizeof (ss));
 161     memcpy (&ss, addr, (alen > sizeof (ss)) ? sizeof (ss) : alen);
 162
 163     pthread_mutex_lock (&mutex);
 164     if (send (sock, &ss, sizeof (ss), 0) != sizeof (ss))
 165         return -1;
 166
 167     fd = recv_fd (sock);
 168     pthread_mutex_unlock (&mutex);
 169     return fd;
 170 }
 171
 172 #else
 173 int rootwrap_bind (int family, int socktype, int protocol,
 174                    const struct sockaddr *addr, size_t alen)
 175 {
 176     (void)family;
 177     (void)socktype;
 178     (void)protocol;
 179     (void)addr;
 180     (void)alen;
 181     errno = EACCES;
 182     return -1;
 183 }
 184
 185 #endif /* ENABLE_ROOTWRAP */