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 /* ancillary 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 #if !defined(MSG_NOSIGNAL)
  61 /* If the other end of the pipe hangs up and MSG_NOSIGNAL is missing, the
  62  * process will get a (likely fatal) SIGPIPE signal. Then again, the other end
  63  * can screw us up in various ways already (e.g. not answer to deadlock). */
  64 # define MSG_NOSIGNAL 0
  65 #endif
  66
  67 #if defined(__OS2__) && !defined(ALIGN)
  68 /* CMSG_NXTHDR requires this */
  69 # define ALIGN(p) _ALIGN(p)
  70 #endif
  71
  72 /**
  73  * Receive a file descriptor from another process
  74  */
  75 static int recv_fd (int p)
  76 {
  77     struct msghdr hdr;
  78     struct iovec iov;
  79     struct cmsghdr *cmsg;
  80     int val, fd;
  81     char buf[CMSG_SPACE (sizeof (fd))];
  82
  83     hdr.msg_name = NULL;
  84     hdr.msg_namelen = 0;
  85     hdr.msg_iov = &iov;
  86     hdr.msg_iovlen = 1;
  87     hdr.msg_control = buf;
  88     hdr.msg_controllen = sizeof (buf);
  89
  90     iov.iov_base = &val;
  91     iov.iov_len = sizeof (val);
  92
  93     if (recvmsg (p, &hdr, 0) != sizeof (val))
  94         return -1;
  95
  96     for (cmsg = CMSG_FIRSTHDR (&hdr); cmsg != NULL;
  97          cmsg = CMSG_NXTHDR (&hdr, cmsg))
  98     {
  99         if ((cmsg->cmsg_level == SOL_SOCKET)
 100          && (cmsg->cmsg_type == SCM_RIGHTS)
 101          && (cmsg->cmsg_len >= CMSG_LEN (sizeof (fd))))
 102         {
 103             memcpy (&fd, CMSG_DATA (cmsg), sizeof (fd));
 104             return fd;
 105         }
 106     }
 107
 108     errno = val;
 109     return -1;
 110 }
 111
 112 /**
 113  * Tries to obtain a bound TCP socket from the root process
 114  */
 115 int rootwrap_bind (int family, int socktype, int protocol,
 116                    const struct sockaddr *addr, size_t alen)
 117 {
 118     /* can't use libvlc */
 119     static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
 120     struct sockaddr_storage ss;
 121     int fd, sock = -1;
 122
 123     const char *sockenv = getenv ("VLC_ROOTWRAP_SOCK");
 124     if (sockenv != NULL)
 125         sock = atoi (sockenv);
 126     if (sock == -1)
 127     {
 128         errno = EACCES;
 129         return -1;
 130     }
 131
 132     switch (family)
 133     {
 134         case AF_INET:
 135             if (alen < sizeof (struct sockaddr_in))
 136             {
 137                 errno = EINVAL;
 138                 return -1;
 139             }
 140             break;
 141
 142 #ifdef AF_INET6
 143         case AF_INET6:
 144             if (alen < sizeof (struct sockaddr_in6))
 145             {
 146                 errno = EINVAL;
 147                 return -1;
 148             }
 149             break;
 150 #endif
 151
 152         default:
 153             errno = EAFNOSUPPORT;
 154             return -1;
 155     }
 156
 157     if (family != addr->sa_family)
 158     {
 159         errno = EAFNOSUPPORT;
 160         return -1;
 161     }
 162
 163     /* Only TCP is implemented at the moment */
 164     if ((socktype != SOCK_STREAM)
 165      || (protocol && (protocol != IPPROTO_TCP)))
 166     {
 167         errno = EACCES;
 168         return -1;
 169     }
 170
 171     memset (&ss, 0, sizeof (ss));
 172     memcpy (&ss, addr, (alen > sizeof (ss)) ? sizeof (ss) : alen);
 173
 174     pthread_mutex_lock (&mutex);
 175     if (send (sock, &ss, sizeof (ss), MSG_NOSIGNAL) != sizeof (ss))
 176     {
 177         pthread_mutex_unlock (&mutex);
 178         return -1;
 179     }
 180
 181     fd = recv_fd (sock);
 182     pthread_mutex_unlock (&mutex);
 183     return fd;
 184 }
 185
 186 #else
 187 int rootwrap_bind (int family, int socktype, int protocol,
 188                    const struct sockaddr *addr, size_t alen)
 189 {
 190     (void)family;
 191     (void)socktype;
 192     (void)protocol;
 193     (void)addr;
 194     (void)alen;
 195     errno = EACCES;
 196     return -1;
 197 }
 198
 199 #endif /* ENABLE_ROOTWRAP */