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 #ifdef HAVE_SYS_SOCKET_H
  45 #include <sys/socket.h>
  46 #endif
  47 #include <sys/uio.h>
  48 #include <sys/un.h>
  49 #include <netinet/in.h>
  50 #include <pthread.h>
  51
  52 /* Required yet non-standard cmsg functions */
  53 #ifndef CMSG_ALIGN
  54 # define CMSG_ALIGN(len) (((len) + sizeof(intptr_t)-1) & ~(sizeof(intptr_t)-1))
  55 #endif
  56 #ifndef CMSG_SPACE
  57 # define CMSG_SPACE(len) (CMSG_ALIGN(sizeof(struct cmsghdr)) + CMSG_ALIGN(len))
  58 #endif
  59 #ifndef CMSG_LEN
  60 # define CMSG_LEN(len) (CMSG_ALIGN(sizeof(struct cmsghdr)) + (len))
  61 #endif
  62 #if !defined(MSG_NOSIGNAL)
  63 /* If the other end of the pipe hangs up and MSG_NOSIGNAL is missing, the
  64  * process will get a (likely fatal) SIGPIPE signal. Then again, the other end
  65  * can screw us up in various ways already (e.g. not answer to deadlock). */
  66 # define MSG_NOSIGNAL 0
  67 #endif
  68
  69 #if defined(__OS2__) && !defined(ALIGN)
  70 /* CMSG_NXTHDR requires this */
  71 # define ALIGN(p) _ALIGN(p)
  72 #endif
  73
  74 /**
  75  * Receive a file descriptor from another process
  76  */
  77 static int recv_fd (int p)
  78 {
  79     struct msghdr hdr;
  80     struct iovec iov;
  81     struct cmsghdr *cmsg;
  82     int val, fd;
  83     char buf[CMSG_SPACE (sizeof (fd))];
  84
  85     hdr.msg_name = NULL;
  86     hdr.msg_namelen = 0;
  87     hdr.msg_iov = &iov;
  88     hdr.msg_iovlen = 1;
  89     hdr.msg_control = buf;
  90     hdr.msg_controllen = sizeof (buf);
  91
  92     iov.iov_base = &val;
  93     iov.iov_len = sizeof (val);
  94
  95     if (recvmsg (p, &hdr, 0) != sizeof (val))
  96         return -1;
  97
  98     for (cmsg = CMSG_FIRSTHDR (&hdr); cmsg != NULL;
  99          cmsg = CMSG_NXTHDR (&hdr, cmsg))
 100     {
 101         if ((cmsg->cmsg_level == SOL_SOCKET)
 102          && (cmsg->cmsg_type == SCM_RIGHTS)
 103          && (cmsg->cmsg_len >= CMSG_LEN (sizeof (fd))))
 104         {
 105             memcpy (&fd, CMSG_DATA (cmsg), sizeof (fd));
 106             return fd;
 107         }
 108     }
 109
 110     errno = val;
 111     return -1;
 112 }
 113
 114 /**
 115  * Tries to obtain a bound TCP socket from the root process
 116  */
 117 int rootwrap_bind (int family, int socktype, int protocol,
 118                    const struct sockaddr *addr, size_t alen)
 119 {
 120     /* can't use libvlc */
 121     static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
 122     struct sockaddr_storage ss;
 123     int fd, sock = -1;
 124
 125     const char *sockenv = getenv ("VLC_ROOTWRAP_SOCK");
 126     if (sockenv != NULL)
 127         sock = atoi (sockenv);
 128     if (sock == -1)
 129     {
 130         errno = EACCES;
 131         return -1;
 132     }
 133
 134     switch (family)
 135     {
 136         case AF_INET:
 137             if (alen < sizeof (struct sockaddr_in))
 138             {
 139                 errno = EINVAL;
 140                 return -1;
 141             }
 142             break;
 143
 144 #ifdef AF_INET6
 145         case AF_INET6:
 146             if (alen < sizeof (struct sockaddr_in6))
 147             {
 148                 errno = EINVAL;
 149                 return -1;
 150             }
 151             break;
 152 #endif
 153
 154         default:
 155             errno = EAFNOSUPPORT;
 156             return -1;
 157     }
 158
 159     if (family != addr->sa_family)
 160     {
 161         errno = EAFNOSUPPORT;
 162         return -1;
 163     }
 164
 165     /* Only TCP is implemented at the moment */
 166     if ((socktype != SOCK_STREAM)
 167      || (protocol && (protocol != IPPROTO_TCP)))
 168     {
 169         errno = EACCES;
 170         return -1;
 171     }
 172
 173     memset (&ss, 0, sizeof (ss));
 174     memcpy (&ss, addr, (alen > sizeof (ss)) ? sizeof (ss) : alen);
 175
 176     pthread_mutex_lock (&mutex);
 177     if (send (sock, &ss, sizeof (ss), MSG_NOSIGNAL) != sizeof (ss))
 178     {
 179         pthread_mutex_unlock (&mutex);
 180         return -1;
 181     }
 182
 183     fd = recv_fd (sock);
 184     pthread_mutex_unlock (&mutex);
 185     return fd;
 186 }
 187
 188 #else
 189 int rootwrap_bind (int family, int socktype, int protocol,
 190                    const struct sockaddr *addr, size_t alen)
 191 {
 192     (void)family;
 193     (void)socktype;
 194     (void)protocol;
 195     (void)addr;
 196     (void)alen;
 197     errno = EACCES;
 198     return -1;
 199 }
 200
 201 #endif /* ENABLE_ROOTWRAP */