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 it
   7  * under the terms of the GNU Lesser General Public License as published by
   8  * the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public License
  17  * along with this program; if not, write to the Free Software Foundation,
  18  * 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 (__OS2__)
  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 #if defined(__OS2__) && !defined(ALIGN)
  62 /* CMSG_NXTHDR requires this */
  63 # define ALIGN(p) _ALIGN(p)
  64 #endif
  65
  66 /**
  67  * Receive a file descriptor from another process
  68  */
  69 static int recv_fd (int p)
  70 {
  71     struct msghdr hdr;
  72     struct iovec iov;
  73     struct cmsghdr *cmsg;
  74     int val, fd;
  75     char buf[CMSG_SPACE (sizeof (fd))];
  76
  77     hdr.msg_name = NULL;
  78     hdr.msg_namelen = 0;
  79     hdr.msg_iov = &iov;
  80     hdr.msg_iovlen = 1;
  81     hdr.msg_control = buf;
  82     hdr.msg_controllen = sizeof (buf);
  83
  84     iov.iov_base = &val;
  85     iov.iov_len = sizeof (val);
  86
  87     if (recvmsg (p, &hdr, 0) != sizeof (val))
  88         return -1;
  89
  90     for (cmsg = CMSG_FIRSTHDR (&hdr); cmsg != NULL;
  91          cmsg = CMSG_NXTHDR (&hdr, cmsg))
  92     {
  93         if ((cmsg->cmsg_level == SOL_SOCKET)
  94          && (cmsg->cmsg_type = SCM_RIGHTS)
  95          && (cmsg->cmsg_len >= CMSG_LEN (sizeof (fd))))
  96         {
  97             memcpy (&fd, CMSG_DATA (cmsg), sizeof (fd));
  98             return fd;
  99         }
 100     }
 101
 102     errno = val;
 103     return -1;
 104 }
 105
 106 /**
 107  * Tries to obtain a bound TCP socket from the root process
 108  */
 109 int rootwrap_bind (int family, int socktype, int protocol,
 110                    const struct sockaddr *addr, size_t alen)
 111 {
 112     /* can't use libvlc */
 113     static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
 114     struct sockaddr_storage ss;
 115     int fd, sock = -1;
 116
 117     const char *sockenv = getenv ("VLC_ROOTWRAP_SOCK");
 118     if (sockenv != NULL)
 119         sock = atoi (sockenv);
 120     if (sock == -1)
 121     {
 122         errno = EACCES;
 123         return -1;
 124     }
 125
 126     switch (family)
 127     {
 128         case AF_INET:
 129             if (alen < sizeof (struct sockaddr_in))
 130             {
 131                 errno = EINVAL;
 132                 return -1;
 133             }
 134             break;
 135
 136 #ifdef AF_INET6
 137         case AF_INET6:
 138             if (alen < sizeof (struct sockaddr_in6))
 139             {
 140                 errno = EINVAL;
 141                 return -1;
 142             }
 143             break;
 144 #endif
 145
 146         default:
 147             errno = EAFNOSUPPORT;
 148             return -1;
 149     }
 150
 151     if (family != addr->sa_family)
 152     {
 153         errno = EAFNOSUPPORT;
 154         return -1;
 155     }
 156
 157     /* Only TCP is implemented at the moment */
 158     if ((socktype != SOCK_STREAM)
 159      || (protocol && (protocol != IPPROTO_TCP)))
 160     {
 161         errno = EACCES;
 162         return -1;
 163     }
 164
 165     memset (&ss, 0, sizeof (ss));
 166     memcpy (&ss, addr, (alen > sizeof (ss)) ? sizeof (ss) : alen);
 167
 168     pthread_mutex_lock (&mutex);
 169     if (send (sock, &ss, sizeof (ss), 0) != sizeof (ss))
 170         return -1;
 171
 172     fd = recv_fd (sock);
 173     pthread_mutex_unlock (&mutex);
 174     return fd;
 175 }
 176
 177 #else
 178 int rootwrap_bind (int family, int socktype, int protocol,
 179                    const struct sockaddr *addr, size_t alen)
 180 {
 181     (void)family;
 182     (void)socktype;
 183     (void)protocol;
 184     (void)addr;
 185     (void)alen;
 186     errno = EACCES;
 187     return -1;
 188 }
 189
 190 #endif /* ENABLE_ROOTWRAP */