mdw@git.distorted.org.uk Git - secnet/blob - udp.c

   1 /* UDP send/receive module for secnet */
   2
   3 /* This module enables sites to communicate by sending UDP
   4  * packets. When an instance of the module is created we can
   5  * optionally bind to a particular local IP address (not implemented
   6  * yet).
   7  *
   8  * Packets are offered to registered receivers in turn. Once one
   9  * accepts it, it isn't offered to any more. */
  10
  11 #include "secnet.h"
  12 #include <stdio.h>
  13 #include <unistd.h>
  14 #include <fcntl.h>
  15 #include <string.h>
  16 #include <errno.h>
  17 #include <sys/socket.h>
  18 #include <sys/wait.h>
  19 #include <netinet/in.h>
  20 #include <arpa/inet.h>
  21 #include "util.h"
  22 #include "magic.h"
  23 #include "unaligned.h"
  24 #include "ipaddr.h"
  25 #include "magic.h"
  26 #include "comm-common.h"
  27
  28 static beforepoll_fn udp_beforepoll;
  29 static afterpoll_fn udp_afterpoll;
  30 static comm_sendmsg_fn udp_sendmsg;
  31
  32 struct udp {
  33     struct udpcommon uc;
  34     struct udpsocks socks;
  35 };
  36
  37 /*
  38  * Re comm_addr.ix: This field allows us to note in the comm_addr
  39  * which socket an incoming packet was received on.  This is required
  40  * for conveniently logging the actual source of a packet.  But the ix
  41  * does not formally form part of the address: it is not used when
  42  * sending, nor when comparing two comm_addrs.
  43  *
  44  * The special value -1 means that the comm_addr was constructed by
  45  * another module in secnet (eg the resolver), rather than being a
  46  * description of the source of an incoming packet.
  47  */
  48
  49 static const char *udp_addr_to_string(void *commst, const struct comm_addr *ca)
  50 {
  51     struct udp *st=commst;
  52     struct udpsocks *socks=&st->socks;
  53     static char sbuf[100];
  54     int ix=ca->ix>=0 ? ca->ix : 0;
  55
  56     assert(ix>=0 && ix<socks->n_socks);
  57     snprintf(sbuf, sizeof(sbuf), "udp:%s%s-%s",
  58              iaddr_to_string(&socks->socks[ix].addr),
  59              ca->ix<0 ? "&" : "",
  60              iaddr_to_string(&ca->ia));
  61     return sbuf;
  62 }
  63
  64 int udp_socks_beforepoll(struct udpsocks *socks,
  65                          struct pollfd *fds, int *nfds_io,
  66                          int *timeout_io)
  67 {
  68     int i;
  69     BEFOREPOLL_WANT_FDS(socks->n_socks);
  70     for (i=0; i<socks->n_socks; i++) {
  71         fds[i].fd=socks->socks[i].fd;
  72         fds[i].events=POLLIN;
  73     }
  74     return 0;
  75 }
  76
  77 static int udp_beforepoll(void *state, struct pollfd *fds, int *nfds_io,
  78                           int *timeout_io)
  79 {
  80     struct udp *st=state;
  81     return udp_socks_beforepoll(&st->socks,fds,nfds_io,timeout_io);
  82 }
  83
  84 void udp_socks_afterpoll(struct udpcommon *uc, struct udpsocks *socks,
  85                          struct pollfd *fds, int nfds)
  86 {
  87     union iaddr from;
  88     socklen_t fromlen;
  89     bool_t done;
  90     int rv;
  91     int i;
  92
  93     struct commcommon *cc=&uc->cc;
  94
  95     for (i=0; i<socks->n_socks; i++) {
  96         if (i>=nfds) continue;
  97         if (!(fds[i].revents & POLLIN)) continue;
  98         assert(fds[i].fd == socks->socks[i].fd);
  99         int fd=socks->socks[i].fd;
 100         do {
 101             fromlen=sizeof(from);
 102             BUF_ASSERT_FREE(cc->rbuf);
 103             BUF_ALLOC(cc->rbuf,"udp_afterpoll");
 104             buffer_init(cc->rbuf,calculate_max_start_pad());
 105             rv=recvfrom(fd, cc->rbuf->start,
 106                         buf_remaining_space(cc->rbuf),
 107                         0, &from.sa, &fromlen);
 108             if (rv>0) {
 109                 cc->rbuf->size=rv;
 110                 if (uc->use_proxy) {
 111                     /* Check that the packet came from our poxy server;
 112                        we shouldn't be contacted directly by anybody else
 113                        (since they can trivially forge source addresses) */
 114                     if (!iaddr_equal(&from,&uc->proxy)) {
 115                         Message(M_INFO,"udp: received packet that's not "
 116                                 "from the proxy\n");
 117                         BUF_FREE(cc->rbuf);
 118                         continue;
 119                     }
 120                     /* proxy protocol supports ipv4 transport only */
 121                     from.sa.sa_family=AF_INET;
 122                     BUF_GET_BYTES(unprepend,cc->rbuf,&from.sin.sin_addr,4);
 123                     buf_unprepend(cc->rbuf,2);
 124                     BUF_GET_BYTES(unprepend,cc->rbuf,&from.sin.sin_port,2);
 125                 }
 126                 struct comm_addr ca;
 127                 ca.comm=&cc->ops;
 128                 ca.ia=from;
 129                 ca.ix=i;
 130                 done=comm_notify(&cc->notify, cc->rbuf, &ca);
 131                 if (!done) {
 132                     uint32_t msgtype;
 133                     if (cc->rbuf->size>12 /* prevents traffic amplification */
 134                         && ((msgtype=get_uint32(cc->rbuf->start+8))
 135                             != LABEL_NAK)) {
 136                         uint32_t source,dest;
 137                         /* Manufacture and send NAK packet */
 138                         source=get_uint32(cc->rbuf->start); /* Us */
 139                         dest=get_uint32(cc->rbuf->start+4); /* Them */
 140                         send_nak(&ca,source,dest,msgtype,cc->rbuf,"unwanted");
 141                     }
 142                     BUF_FREE(cc->rbuf);
 143                 }
 144                 BUF_ASSERT_FREE(cc->rbuf);
 145             } else {
 146                 BUF_FREE(cc->rbuf);
 147             }
 148         } while (rv>=0);
 149     }
 150 }
 151
 152 static void udp_afterpoll(void *state, struct pollfd *fds, int nfds)
 153 {
 154     struct udp *st=state;
 155     return udp_socks_afterpoll(&st->uc,&st->socks,fds,nfds);
 156 }
 157
 158 static bool_t udp_sendmsg(void *commst, struct buffer_if *buf,
 159                           const struct comm_addr *dest)
 160 {
 161     struct udp *st=commst;
 162     struct udpcommon *uc=&st->uc;
 163     struct udpsocks *socks=&st->socks;
 164     uint8_t *sa;
 165
 166     if (uc->use_proxy) {
 167         sa=buf_prepend(buf,8);
 168         if (dest->ia.sa.sa_family != AF_INET) {
 169             Message(M_INFO,
 170                "udp: proxy means dropping outgoing non-IPv4 packet to %s\n",
 171                     iaddr_to_string(&dest->ia));
 172             return False;
 173         }
 174         memcpy(sa,&dest->ia.sin.sin_addr,4);
 175         memset(sa+4,0,4);
 176         memcpy(sa+6,&dest->ia.sin.sin_port,2);
 177         sendto(socks->socks[0].fd,sa,buf->size+8,0,&uc->proxy.sa,
 178                iaddr_socklen(&uc->proxy));
 179         buf_unprepend(buf,8);
 180     } else {
 181         int i,r;
 182         bool_t allunsupported=True;
 183         for (i=0; i<socks->n_socks; i++) {
 184             if (dest->ia.sa.sa_family != socks->socks[i].addr.sa.sa_family)
 185                 /* no point even trying */
 186                 continue;
 187             r=sendto(socks->socks[i].fd, buf->start, buf->size, 0,
 188                      &dest->ia.sa, iaddr_socklen(&dest->ia));
 189             if (r>=0) return True;
 190             if (!(errno==EAFNOSUPPORT || errno==ENETUNREACH))
 191                 /* who knows what that error means? */
 192                 allunsupported=False;
 193         }
 194         return !allunsupported; /* see doc for comm_sendmsg_fn in secnet.h */
 195     }
 196
 197     return True;
 198 }
 199
 200 static void udp_make_socket(struct udp *st, struct udpsock *us)
 201 {
 202     const union iaddr *addr=&us->addr;
 203     struct udpcommon *uc=&st->uc;
 204     struct commcommon *cc=&uc->cc;
 205
 206     us->fd=socket(addr->sa.sa_family, SOCK_DGRAM, IPPROTO_UDP);
 207     if (us->fd<0) {
 208         fatal_perror("udp (%s:%d): socket",cc->loc.file,cc->loc.line);
 209     }
 210     if (fcntl(us->fd, F_SETFL, fcntl(us->fd, F_GETFL)|O_NONBLOCK)==-1) {
 211         fatal_perror("udp (%s:%d): fcntl(set O_NONBLOCK)",
 212                      cc->loc.file,cc->loc.line);
 213     }
 214     setcloexec(us->fd);
 215 #ifdef CONFIG_IPV6
 216     if (addr->sa.sa_family==AF_INET6) {
 217         int r;
 218         int optval=1;
 219         socklen_t optlen=sizeof(optval);
 220         r=setsockopt(us->fd,IPPROTO_IPV6,IPV6_V6ONLY,&optval,optlen);
 221         if (r) fatal_perror("udp (%s:%d): setsockopt(,IPV6_V6ONLY,&1,)",
 222                             cc->loc.file,cc->loc.line);
 223     }
 224 #endif
 225
 226     if (uc->authbind) {
 227         pid_t c;
 228         int status;
 229
 230         /* XXX this fork() and waitpid() business needs to be hidden
 231            in some system-specific library functions. */
 232         c=fork();
 233         if (c==-1) {
 234             fatal_perror("udp_phase_hook: fork() for authbind");
 235         }
 236         if (c==0) {
 237             char *argv[5], addrstr[33], portstr[5];
 238             const char *addrfam;
 239             int port;
 240             switch (addr->sa.sa_family) {
 241             case AF_INET:
 242                 sprintf(addrstr,"%08lX",(long)addr->sin.sin_addr.s_addr);
 243                 port=addr->sin.sin_port;
 244                 addrfam=NULL;
 245                 break;
 246 #ifdef CONFIG_IPV6
 247             case AF_INET6: {
 248                 int i;
 249                 for (i=0; i<16; i++)
 250                     sprintf(addrstr+i*2,"%02X",addr->sin6.sin6_addr.s6_addr[i]);
 251                 port=addr->sin6.sin6_port;
 252                 addrfam="6";
 253                 break;
 254             }
 255 #endif /*CONFIG_IPV6*/
 256             default:
 257                 fatal("udp (%s:%d): unsupported address family for authbind",
 258                       cc->loc.file,cc->loc.line);
 259             }
 260             sprintf(portstr,"%04X",port);
 261             argv[0]=uc->authbind;
 262             argv[1]=addrstr;
 263             argv[2]=portstr;
 264             argv[3]=(char*)addrfam;
 265             argv[4]=NULL;
 266             dup2(us->fd,0);
 267             execvp(uc->authbind,argv);
 268             _exit(255);
 269         }
 270         while (waitpid(c,&status,0)==-1) {
 271             if (errno==EINTR) continue;
 272             fatal_perror("udp (%s:%d): authbind",cc->loc.file,cc->loc.line);
 273         }
 274         if (WIFSIGNALED(status)) {
 275             fatal("udp (%s:%d): authbind died on signal %d",cc->loc.file,
 276                   cc->loc.line, WTERMSIG(status));
 277         }
 278         if (WIFEXITED(status) && WEXITSTATUS(status)!=0) {
 279             fatal("udp (%s:%d): authbind died with status %d",cc->loc.file,
 280                   cc->loc.line, WEXITSTATUS(status));
 281         }
 282     } else {
 283         if (bind(us->fd, &addr->sa, iaddr_socklen(addr))!=0) {
 284             fatal_perror("udp (%s:%d): bind",cc->loc.file,cc->loc.line);
 285         }
 286     }
 287 }
 288
 289 static void udp_phase_hook(void *sst, uint32_t new_phase)
 290 {
 291     struct udp *st=sst;
 292     struct udpsocks *socks=&st->socks;
 293     int i;
 294     for (i=0; i<socks->n_socks; i++)
 295         udp_make_socket(st,&socks->socks[i]);
 296
 297     register_for_poll(st,udp_beforepoll,udp_afterpoll,"udp");
 298 }
 299
 300 static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context,
 301                          list_t *args)
 302 {
 303     struct udp *st;
 304     list_t *caddrl;
 305     list_t *l;
 306     uint32_t a;
 307     int i;
 308
 309     COMM_APPLY(st,&st->uc.cc,udp_,"udp",loc);
 310     COMM_APPLY_STANDARD(st,&st->uc.cc,"udp",args);
 311     UDP_APPLY_STANDARD(st,&st->uc,"udp");
 312
 313     struct udpcommon *uc=&st->uc;
 314     struct udpsocks *socks=&st->socks;
 315     struct commcommon *cc=&uc->cc;
 316
 317     union iaddr defaultaddrs[] = {
 318 #ifdef CONFIG_IPV6
 319         { .sin6 = { .sin6_family=AF_INET6,
 320                     .sin6_port=htons(uc->port),
 321                     .sin6_addr=IN6ADDR_ANY_INIT } },
 322 #endif
 323         { .sin = { .sin_family=AF_INET,
 324                    .sin_port=htons(uc->port),
 325                    .sin_addr= { .s_addr=INADDR_ANY } } }
 326     };
 327
 328     caddrl=dict_lookup(d,"address");
 329     socks->n_socks=caddrl ? list_length(caddrl) : (int)ARRAY_SIZE(defaultaddrs);
 330     if (socks->n_socks<=0 || socks->n_socks>UDP_MAX_SOCKETS)
 331         cfgfatal(cc->loc,"udp","`address' must be 1..%d addresses",
 332                  UDP_MAX_SOCKETS);
 333
 334     for (i=0; i<socks->n_socks; i++) {
 335         struct udpsock *us=&socks->socks[i];
 336         if (!list_length(caddrl)) {
 337             us->addr=defaultaddrs[i];
 338         } else {
 339             string_item_to_iaddr(list_elem(caddrl,i),uc->port,&us->addr,"udp");
 340         }
 341         us->fd=-1;
 342     }
 343
 344     l=dict_lookup(d,"proxy");
 345     if (l) {
 346         uc->use_proxy=True;
 347         uc->proxy.sa.sa_family=AF_INET;
 348         item=list_elem(l,0);
 349         if (!item || item->type!=t_string) {
 350             cfgfatal(cc->loc,"udp","proxy must supply ""addr"",port\n");
 351         }
 352         a=string_item_to_ipaddr(item,"proxy");
 353         uc->proxy.sin.sin_addr.s_addr=htonl(a);
 354         item=list_elem(l,1);
 355         if (!item || item->type!=t_number) {
 356             cfgfatal(cc->loc,"udp","proxy must supply ""addr"",port\n");
 357         }
 358         uc->proxy.sin.sin_port=htons(item->data.number);
 359     }
 360
 361     update_max_start_pad(&comm_max_start_pad, uc->use_proxy ? 8 : 0);
 362
 363     add_hook(PHASE_GETRESOURCES,udp_phase_hook,st);
 364
 365     return new_closure(&cc->cl);
 366 }
 367
 368 void udp_module(dict_t *dict)
 369 {
 370     add_closure(dict,"udp",udp_apply);
 371 }