tftpd/recvfrom.c

   1 /* ----------------------------------------------------------------------- *
   2  *
   3  *   Copyright 2001-2006 H. Peter Anvin - All Rights Reserved
   4  *
   5  *   This program is free software available under the same license
   6  *   as the "OpenBSD" operating system, distributed at
   7  *   http://www.openbsd.org/.
   8  *
   9  * ----------------------------------------------------------------------- */
  10
  11 /*
  12  * recvfrom.c
  13  *
  14  * Emulate recvfrom() using recvmsg(), but try to capture the local address
  15  * since some TFTP clients consider it an error to get the reply from another
  16  * IP address than the request was sent to.
  17  *
  18  */
  19
  20 #include "config.h"             /* Must be included first! */
  21 #include "common/tftpsubs.h"
  22 #include "recvfrom.h"
  23 #ifdef HAVE_MACHINE_PARAM_H
  24 #include <machine/param.h>      /* Needed on some versions of FreeBSD */
  25 #endif
  26
  27 #if defined(HAVE_RECVMSG) && defined(HAVE_MSGHDR_MSG_CONTROL)
  28
  29 #include <sys/uio.h>
  30
  31 #ifdef IP_PKTINFO
  32 # ifndef HAVE_STRUCT_IN_PKTINFO
  33 #  ifdef __linux__
  34 /* Assume this version of glibc simply lacks the definition */
  35 struct in_pktinfo {
  36     int ipi_ifindex;
  37     struct in_addr ipi_spec_dst;
  38     struct in_addr ipi_addr;
  39 };
  40 #  else
  41 #   undef IP_PKTINFO            /* No definition, no way to get it */
  42 #  endif
  43 # endif
  44 #endif
  45
  46 #ifndef CMSG_LEN
  47 # define CMSG_LEN(size)  (sizeof(struct cmsghdr) + (size))
  48 #endif
  49 #ifndef CMSG_SPACE
  50 # define CMSG_SPACE(size) (sizeof(struct cmsghdr) + (size))
  51 #endif
  52
  53 /*
  54  * Check to see if this is a valid local address, meaning that we can
  55  * legally bind to it.
  56  */
  57 static int address_is_local(const union sock_addr *addr)
  58 {
  59     union sock_addr sa1, sa2;
  60     int sockfd = -1;
  61     int e;
  62     int rv = 0;
  63     socklen_t addrlen;
  64
  65     memcpy(&sa1, addr, sizeof sa1);
  66
  67     /* Multicast or universal broadcast address? */
  68     if (sa1.sa.sa_family == AF_INET) {
  69         if (ntohl(sa1.si.sin_addr.s_addr) >= (224UL << 24))
  70             return 0;
  71         sa1.si.sin_port = 0;    /* Any port */
  72     }
  73 #ifdef HAVE_IPV6
  74     else if (sa1.sa.sa_family == AF_INET6) {
  75         if (IN6_IS_ADDR_MULTICAST(&sa1.s6.sin6_addr))
  76             return 0;
  77         sa1.s6.sin6_port = 0;   /* Any port */
  78     }
  79 #endif
  80     else
  81         return 0;
  82
  83     sockfd = socket(sa1.sa.sa_family, SOCK_DGRAM, 0);
  84     if (sockfd < 0)
  85         goto err;
  86
  87     if (bind(sockfd, &sa1.sa, SOCKLEN(&sa1)))
  88         goto err;
  89
  90     addrlen = SOCKLEN(addr);
  91     if (getsockname(sockfd, (struct sockaddr *)&sa2, &addrlen))
  92         goto err;
  93
  94     if (sa1.sa.sa_family != sa2.sa.sa_family)
  95         goto err;
  96
  97     if (sa2.sa.sa_family == AF_INET)
  98         rv = sa1.si.sin_addr.s_addr == sa2.si.sin_addr.s_addr;
  99 #ifdef HAVE_IPV6
 100     else if (sa2.sa.sa_family == AF_INET6)
 101         rv = IN6_ARE_ADDR_EQUAL(&sa1.s6.sin6_addr, &sa2.s6.sin6_addr);
 102 #endif
 103     else
 104         rv = 0;
 105
 106 err:
 107     e = errno;
 108
 109     if (sockfd >= 0)
 110         close(sockfd);
 111
 112     errno = e;
 113     return rv;
 114 }
 115
 116 int
 117 myrecvfrom(int s, void *buf, int len, unsigned int flags,
 118            struct sockaddr *from, socklen_t * fromlen,
 119            union sock_addr *myaddr)
 120 {
 121     struct msghdr msg;
 122     struct iovec iov;
 123     int n;
 124     struct cmsghdr *cmptr;
 125     union {
 126         struct cmsghdr cm;
 127 #ifdef IP_PKTINFO
 128         char control[CMSG_SPACE(sizeof(struct in_addr)) +
 129                      CMSG_SPACE(sizeof(struct in_pktinfo))];
 130 #else
 131         char control[CMSG_SPACE(sizeof(struct in_addr))];
 132 #endif
 133 #ifdef HAVE_IPV6
 134 #ifdef HAVE_STRUCT_IN6_PKTINFO
 135         char control6[CMSG_SPACE(sizeof(struct in6_addr)) +
 136                      CMSG_SPACE(sizeof(struct in6_pktinfo))];
 137 #else
 138         char control6[CMSG_SPACE(sizeof(struct in6_addr))];
 139 #endif
 140 #endif
 141     } control_un;
 142     int on = 1;
 143 #ifdef IP_PKTINFO
 144     struct in_pktinfo pktinfo;
 145 #endif
 146 #ifdef HAVE_STRUCT_IN6_PKTINFO
 147     struct in6_pktinfo pktinfo6;
 148 #endif
 149
 150     /* Try to enable getting the return address */
 151 #ifdef IP_RECVDSTADDR
 152     if (from->sa_family == AF_INET)
 153         setsockopt(s, IPPROTO_IP, IP_RECVDSTADDR, &on, sizeof(on));
 154 #endif
 155 #ifdef IP_PKTINFO
 156     if (from->sa_family == AF_INET)
 157         setsockopt(s, IPPROTO_IP, IP_PKTINFO, &on, sizeof(on));
 158 #endif
 159 #ifdef HAVE_IPV6
 160 #ifdef IPV6_RECVPKTINFO
 161     if (from->sa_family == AF_INET6)
 162         setsockopt(s, IPPROTO_IPV6, IPV6_RECVPKTINFO, &on, sizeof(on));
 163 #endif
 164 #endif
 165     bzero(&msg, sizeof msg);    /* Clear possible system-dependent fields */
 166     msg.msg_control = control_un.control;
 167     msg.msg_controllen = sizeof(control_un);
 168     msg.msg_flags = 0;
 169
 170     msg.msg_name = from;
 171     msg.msg_namelen = *fromlen;
 172     iov.iov_base = buf;
 173     iov.iov_len = len;
 174     msg.msg_iov = &iov;
 175     msg.msg_iovlen = 1;
 176
 177     if ((n = recvmsg(s, &msg, flags)) < 0)
 178         return n;               /* Error */
 179
 180     *fromlen = msg.msg_namelen;
 181
 182     if (myaddr) {
 183         bzero(myaddr, sizeof(*myaddr));
 184         myaddr->sa.sa_family = from->sa_family;
 185
 186         if (msg.msg_controllen < sizeof(struct cmsghdr) ||
 187             (msg.msg_flags & MSG_CTRUNC))
 188             return n;           /* No information available */
 189
 190         for (cmptr = CMSG_FIRSTHDR(&msg); cmptr != NULL;
 191              cmptr = CMSG_NXTHDR(&msg, cmptr)) {
 192
 193             if (from->sa_family == AF_INET) {
 194                 myaddr->sa.sa_family = AF_INET;
 195 #ifdef IP_RECVDSTADDR
 196                 if (cmptr->cmsg_level == IPPROTO_IP &&
 197                     cmptr->cmsg_type == IP_RECVDSTADDR) {
 198                     memcpy(&myaddr->si.sin_addr, CMSG_DATA(cmptr),
 199                            sizeof(struct in_addr));
 200                 }
 201 #endif
 202
 203 #ifdef IP_PKTINFO
 204                 if (cmptr->cmsg_level == IPPROTO_IP &&
 205                     cmptr->cmsg_type == IP_PKTINFO) {
 206                     memcpy(&pktinfo, CMSG_DATA(cmptr),
 207                            sizeof(struct in_pktinfo));
 208                     memcpy(&myaddr->si.sin_addr, &pktinfo.ipi_addr,
 209                            sizeof(struct in_addr));
 210                 }
 211 #endif
 212             }
 213 #ifdef HAVE_IPV6
 214             else if (from->sa_family == AF_INET6) {
 215                 myaddr->sa.sa_family = AF_INET6;
 216 #ifdef IP6_RECVDSTADDR
 217                 if (cmptr->cmsg_level == IPPROTO_IPV6 &&
 218                     cmptr->cmsg_type == IPV6_RECVDSTADDR )
 219                     memcpy(&myaddr->s6.sin6_addr, CMSG_DATA(cmptr),
 220                            sizeof(struct in6_addr));
 221 #endif
 222
 223 #ifdef HAVE_STRUCT_IN6_PKTINFO
 224                 if (cmptr->cmsg_level == IPPROTO_IPV6 &&
 225                     (
 226 #ifdef IPV6_RECVPKTINFO
 227                      cmptr->cmsg_type == IPV6_RECVPKTINFO ||
 228 #endif
 229                      cmptr->cmsg_type == IPV6_PKTINFO)) {
 230                     memcpy(&pktinfo6, CMSG_DATA(cmptr),
 231                            sizeof(struct in6_pktinfo));
 232                     memcpy(&myaddr->s6.sin6_addr, &pktinfo6.ipi6_addr,
 233                            sizeof(struct in6_addr));
 234                 }
 235 #endif
 236             }
 237 #endif
 238         }
 239         /* If the address is not a valid local address,
 240          * then bind to any address...
 241          */
 242         if (address_is_local(myaddr) != 1) {
 243             if (myaddr->sa.sa_family == AF_INET)
 244                 ((struct sockaddr_in *)myaddr)->sin_addr.s_addr = INADDR_ANY;
 245 #ifdef HAVE_IPV6
 246             else if (myaddr->sa.sa_family == AF_INET6)
 247                 memset(&myaddr->s6.sin6_addr, 0, sizeof(struct in6_addr));
 248 #endif
 249         }
 250     }
 251     return n;
 252 }
 253
 254 #else                           /* pointless... */
 255
 256 int
 257 myrecvfrom(int s, void *buf, int len, unsigned int flags,
 258            struct sockaddr *from, socklen_t * fromlen,
 259            union sock_addr *myaddr)
 260 {
 261     /* There is no way we can get the local address, fudge it */
 262
 263     bzero(myaddr, sizeof(*myaddr));
 264     myaddr->sa.sa_family = from->sa_family;
 265     sa_set_port(myaddr, htons(IPPORT_TFTP));
 266
 267     return recvfrom(s, buf, len, flags, from, fromlen);
 268 }
 269
 270 #endif