udp.c

   1 /* UDP send/receive module for secnet */
   2
   3 /*
   4  * This file is part of secnet.
   5  * See README for full list of copyright holders.
   6  *
   7  * secnet is free software; you can redistribute it and/or modify it
   8  * under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 3 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * secnet is distributed in the hope that it will be useful, but
  13  * WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * version 3 along with secnet; if not, see
  19  * https://www.gnu.org/licenses/gpl.html.
  20  */
  21
  22 /* This module enables sites to communicate by sending UDP
  23  * packets. When an instance of the module is created we can
  24  * optionally bind to a particular local IP address (not implemented
  25  * yet).
  26  *
  27  * Packets are offered to registered receivers in turn. Once one
  28  * accepts it, it isn't offered to any more. */
  29
  30 #include "secnet.h"
  31 #include <stdio.h>
  32 #include <unistd.h>
  33 #include <fcntl.h>
  34 #include <string.h>
  35 #include <errno.h>
  36 #include <sys/socket.h>
  37 #include <sys/wait.h>
  38 #include <netinet/in.h>
  39 #include <arpa/inet.h>
  40 #include "util.h"
  41 #include "magic.h"
  42 #include "unaligned.h"
  43 #include "ipaddr.h"
  44 #include "magic.h"
  45 #include "comm-common.h"
  46
  47 static comm_sendmsg_fn udp_sendmsg;
  48
  49 struct udp {
  50     struct udpcommon uc;
  51     struct udpsocks socks;
  52     bool_t addr_configured;
  53     unsigned counter;
  54 };
  55
  56 /*
  57  * Re comm_addr.ix: This field allows us to note in the comm_addr
  58  * which socket an incoming packet was received on.  This is required
  59  * for conveniently logging the actual source of a packet.  But the ix
  60  * does not formally form part of the address: it is not used when
  61  * sending, nor when comparing two comm_addrs.
  62  *
  63  * The special value -1 means that the comm_addr was constructed by
  64  * another module in secnet (eg the resolver), rather than being a
  65  * description of the source of an incoming packet.
  66  */
  67
  68 static const char *udp_addr_to_string(void *commst, const struct comm_addr *ca)
  69 {
  70     struct udp *st=commst;
  71     struct udpsocks *socks=&st->socks;
  72     static char sbuf[100];
  73     int ix=ca->ix>=0 ? ca->ix : 0;
  74
  75     assert(ix>=0 && ix<socks->n_socks);
  76     snprintf(sbuf, sizeof(sbuf), "udp#%u@l%d:%s%s-%s",
  77              st->counter, st->uc.cc.loc.line,
  78              iaddr_to_string(&socks->socks[ix].addr),
  79              ca->ix<0 && socks->n_socks>1 ? "&" : "",
  80              iaddr_to_string(&ca->ia));
  81     return sbuf;
  82 }
  83
  84 static int udp_socks_beforepoll(void *state, struct pollfd *fds, int *nfds_io,
  85                                 int *timeout_io)
  86 {
  87     struct udpsocks *socks=state;
  88     int i;
  89     BEFOREPOLL_WANT_FDS(socks->n_socks);
  90     for (i=0; i<socks->n_socks; i++) {
  91         fds[i].fd=socks->socks[i].fd;
  92         fds[i].events=POLLIN;
  93     }
  94     return 0;
  95 }
  96
  97 const char *af_name(int af)
  98 {
  99     switch (af) {
 100     case AF_INET6: return "IPv6";
 101     case AF_INET:  return "IPv4";
 102     case 0:        return "(any)";
 103     default: abort();
 104     }
 105 }
 106
 107 void udp_sock_experienced(struct log_if *lg, struct udpcommon *uc,
 108                           struct udpsocks *socks, struct udpsock *us,
 109                           const union iaddr *dest, int af,
 110                           int r, int errnoval)
 111 {
 112     bool_t success=r>=0;
 113     if (us->experienced[!!dest][af][success]++)
 114         return;
 115     lg_perror(lg, uc->cc.cl.description, &uc->cc.loc,
 116               success ? M_INFO : M_WARNING,
 117               success ? 0 : errnoval,
 118               "%s %s experiencing some %s %s%s%s%s%s%s",
 119               socks->desc,iaddr_to_string(&us->addr),
 120               success?"success":"trouble",
 121               dest?"transmitting":"receiving",
 122               af?" ":"", af?af_name(af):"",
 123               dest?" (to ":"",
 124               dest?iaddr_to_string(dest):"",
 125               dest?")":"");
 126 }
 127
 128 static void udp_socks_afterpoll(void *state, struct pollfd *fds, int nfds)
 129 {
 130     struct udpsocks *socks=state;
 131     struct udpcommon *uc=socks->uc;
 132     union iaddr from;
 133     socklen_t fromlen;
 134     bool_t done;
 135     int rv;
 136     int i;
 137
 138     struct commcommon *cc=&uc->cc;
 139
 140     for (i=0; i<socks->n_socks; i++) {
 141         struct udpsock *us=&socks->socks[i];
 142         if (i>=nfds) continue;
 143         if (!(fds[i].revents & POLLIN)) continue;
 144         assert(fds[i].fd == us->fd);
 145         int fd=us->fd;
 146         do {
 147             fromlen=sizeof(from);
 148             BUF_ASSERT_FREE(cc->rbuf);
 149             BUF_ALLOC(cc->rbuf,"udp_afterpoll");
 150             buffer_init(cc->rbuf,calculate_max_start_pad());
 151             rv=recvfrom(fd, cc->rbuf->start,
 152                         buf_remaining_space(cc->rbuf),
 153                         0, &from.sa, &fromlen);
 154             if (rv>0) {
 155                 cc->rbuf->size=rv;
 156                 if (uc->use_proxy) {
 157                     /* Check that the packet came from our poxy server;
 158                        we shouldn't be contacted directly by anybody else
 159                        (since they can trivially forge source addresses) */
 160                     if (!iaddr_equal(&from,&uc->proxy,False)) {
 161                         Message(M_INFO,"udp: received packet that's not "
 162                                 "from the proxy\n");
 163                         BUF_FREE(cc->rbuf);
 164                         continue;
 165                     }
 166                     /* proxy protocol supports ipv4 transport only */
 167                     from.sa.sa_family=AF_INET;
 168                     BUF_GET_BYTES(unprepend,cc->rbuf,&from.sin.sin_addr,4);
 169                     buf_unprepend(cc->rbuf,2);
 170                     BUF_GET_BYTES(unprepend,cc->rbuf,&from.sin.sin_port,2);
 171                 }
 172                 struct comm_addr ca;
 173                 ca.comm=&cc->ops;
 174                 ca.ia=from;
 175                 ca.ix=i;
 176                 done=comm_notify(cc, cc->rbuf, &ca);
 177                 if (done) {
 178                     udp_sock_experienced(0,uc,socks,us,0,
 179                                          from.sa.sa_family,0,0);
 180                 } else {
 181                     uint32_t msgtype;
 182                     if (cc->rbuf->size>12 /* prevents traffic amplification */
 183                         && ((msgtype=get_uint32(cc->rbuf->start+8))
 184                             != LABEL_NAK)) {
 185                         uint32_t source,dest;
 186                         /* Manufacture and send NAK packet */
 187                         source=get_uint32(cc->rbuf->start); /* Us */
 188                         dest=get_uint32(cc->rbuf->start+4); /* Them */
 189                         send_nak(&ca,source,dest,msgtype,cc->rbuf,
 190                                  priomsg_getmessage(&cc->why_unwanted,
 191                                                     "unwanted"));
 192                     }
 193                     BUF_FREE(cc->rbuf);
 194                 }
 195                 BUF_ASSERT_FREE(cc->rbuf);
 196             } else { /* rv<=0 */
 197                 if (errno!=EINTR && !iswouldblock(errno))
 198                     udp_sock_experienced(0,uc,socks,us, 0,0, rv,errno);
 199                 BUF_FREE(cc->rbuf);
 200             }
 201         } while (rv>=0);
 202     }
 203 }
 204
 205 static bool_t udp_sendmsg(void *commst, struct buffer_if *buf,
 206                           const struct comm_addr *dest,
 207                           struct comm_clientinfo *clientinfo)
 208 {
 209     struct udp *st=commst;
 210     struct udpcommon *uc=&st->uc;
 211     struct udpsocks *socks=&st->socks;
 212     uint8_t *sa;
 213
 214     if (uc->use_proxy) {
 215         struct udpsock *us=&socks->socks[0];
 216         sa=buf_prepend(buf,8);
 217         if (dest->ia.sa.sa_family != AF_INET) {
 218             Message(M_INFO,
 219                "udp: proxy means dropping outgoing non-IPv4 packet to %s\n",
 220                     iaddr_to_string(&dest->ia));
 221             return False;
 222         }
 223         memcpy(sa,&dest->ia.sin.sin_addr,4);
 224         memset(sa+4,0,4);
 225         memcpy(sa+6,&dest->ia.sin.sin_port,2);
 226         int r=sendto(us->fd,sa,buf->size+8,0,&uc->proxy.sa,
 227                iaddr_socklen(&uc->proxy));
 228         udp_sock_experienced(0,uc,socks,us, &dest->ia,0, r,errno);
 229         buf_unprepend(buf,8);
 230     } else {
 231         int i,r;
 232         bool_t allunsupported=True;
 233         int af=dest->ia.sa.sa_family;
 234         for (i=0; i<socks->n_socks; i++) {
 235             struct udpsock *us=&socks->socks[i];
 236             if (us->addr.sa.sa_family != af)
 237                 /* no point even trying */
 238                 continue;
 239             r=sendto(us->fd, buf->start, buf->size, 0,
 240                      &dest->ia.sa, iaddr_socklen(&dest->ia));
 241             udp_sock_experienced(0,uc,socks,us, &dest->ia,af, r,errno);
 242             if (r>=0) return True;
 243             if (!(errno==EAFNOSUPPORT || errno==ENETUNREACH))
 244                 /* who knows what that error means? */
 245                 allunsupported=False;
 246         }
 247         return !allunsupported; /* see doc for comm_sendmsg_fn in secnet.h */
 248     }
 249
 250     return True;
 251 }
 252
 253 void udp_destroy_socket(struct udpcommon *uc, struct udpsock *us)
 254 {
 255     if (us->fd>=0) {
 256         close(us->fd);
 257         us->fd=-1;
 258     }
 259 }
 260
 261 #define FAIL_LG 0, cc->cl.description, &cc->loc, failmsgclass
 262 #define FAIL(...) do{                                           \
 263         lg_perror(FAIL_LG,errno,__VA_ARGS__);   \
 264         goto failed;                                            \
 265     }while(0)
 266
 267 static bool_t record_socket_gotaddr(struct udpcommon *uc, struct udpsock *us,
 268                                     int failmsgclass)
 269 {
 270     struct commcommon *cc=&uc->cc;
 271     socklen_t salen=sizeof(us->addr);
 272     int r=getsockname(us->fd,&us->addr.sa,&salen);
 273     if (r) FAIL("getsockname()");
 274     if ((size_t)salen>sizeof(us->addr)) /* cast squashes clang warning */
 275       { errno=0; FAIL("getsockname() length"); }
 276     return True;
 277
 278  failed:
 279     return False;
 280 }
 281
 282 bool_t udp_import_socket(struct udpcommon *uc, struct udpsock *us,
 283                          int failmsgclass, int fd)
 284 {
 285     FILLZERO(us->experienced);
 286     us->fd=fd;
 287     return record_socket_gotaddr(uc,us,failmsgclass);
 288 }
 289
 290 bool_t udp_make_socket(struct udpcommon *uc, struct udpsock *us,
 291                        int failmsgclass)
 292 {
 293     const union iaddr *addr=&us->addr;
 294     struct commcommon *cc=&uc->cc;
 295     us->fd=-1;
 296
 297     FILLZERO(us->experienced);
 298     us->fd=socket(addr->sa.sa_family, SOCK_DGRAM, IPPROTO_UDP);
 299     if (us->fd<0) FAIL("socket");
 300     setnonblock(us->fd);
 301     setcloexec(us->fd);
 302 #ifdef CONFIG_IPV6
 303     if (addr->sa.sa_family==AF_INET6) {
 304         int r;
 305         int optval=1;
 306         socklen_t optlen=sizeof(optval);
 307         r=setsockopt(us->fd,IPPROTO_IPV6,IPV6_V6ONLY,&optval,optlen);
 308         if (r) FAIL("setsockopt(,IPV6_V6ONLY,&1,)");
 309     }
 310 #endif
 311
 312     if (uc->authbind) {
 313         pid_t c;
 314         int status;
 315         char desc[200];
 316         snprintf(desc,sizeof(desc),"authbind for %s: %s",
 317                  iaddr_to_string(addr), uc->authbind);
 318
 319         /* XXX this fork() and waitpid() business needs to be hidden
 320            in some system-specific library functions. */
 321         c=fork();
 322         if (c==-1)
 323             FAIL("fork() for authbind");
 324         if (c==0) {
 325             char *argv[5], addrstr[33], portstr[5];
 326             const char *addrfam;
 327             int port;
 328             afterfork();
 329             switch (addr->sa.sa_family) {
 330             case AF_INET:
 331                 sprintf(addrstr,"%08lX",(long)addr->sin.sin_addr.s_addr);
 332                 port=addr->sin.sin_port;
 333                 addrfam=NULL;
 334                 break;
 335 #ifdef CONFIG_IPV6
 336             case AF_INET6: {
 337                 int i;
 338                 for (i=0; i<16; i++)
 339                     sprintf(addrstr+i*2,"%02X",addr->sin6.sin6_addr.s6_addr[i]);
 340                 port=addr->sin6.sin6_port;
 341                 addrfam="6";
 342                 break;
 343             }
 344 #endif /*CONFIG_IPV6*/
 345             default:
 346                 fatal("udp (%s:%d): unsupported address family for authbind",
 347                       cc->loc.file,cc->loc.line);
 348             }
 349             sprintf(portstr,"%04X",port);
 350             argv[0]=uc->authbind;
 351             argv[1]=addrstr;
 352             argv[2]=portstr;
 353             argv[3]=(char*)addrfam;
 354             argv[4]=NULL;
 355             dup2(us->fd,0);
 356             execvp(uc->authbind,argv);
 357             _exit(255);
 358         }
 359         while (waitpid(c,&status,0)==-1) {
 360             if (errno==EINTR) continue;
 361             FAIL("waitpid for authbind");
 362         }
 363         if (status) {
 364             if (WIFEXITED(status) && WEXITSTATUS(status)<127) {
 365                 int es=WEXITSTATUS(status);
 366                 lg_perror(FAIL_LG,es,
 367                           "%s exited with error exit status %d;"
 368                           " indicates error",desc,es);
 369             } else {
 370                 lg_exitstatus(FAIL_LG,status,desc);
 371             }
 372             goto failed;
 373         }
 374     } else {
 375         if (bind(us->fd, &addr->sa, iaddr_socklen(addr))!=0)
 376             FAIL("bind (%s)",iaddr_to_string(addr));
 377     }
 378
 379     bool_t ok=record_socket_gotaddr(uc,us,failmsgclass);
 380     if (!ok) goto failed;
 381
 382     return True;
 383
 384 failed:
 385     udp_destroy_socket(uc,us);
 386     return False;
 387 }
 388
 389 #undef FAIL
 390
 391 void udp_socks_register(struct udpcommon *uc, struct udpsocks *socks,
 392                         const char *desc)
 393 {
 394     socks->uc=uc;
 395     socks->desc=desc;
 396     socks->interest=
 397         register_for_poll(socks,udp_socks_beforepoll,udp_socks_afterpoll,"udp");
 398 }
 399
 400 void udp_socks_deregister(struct udpcommon *uc, struct udpsocks *socks)
 401 {
 402     socks->uc=uc;
 403     deregister_for_poll(socks->interest);
 404 }
 405
 406 void udp_socks_childpersist(struct udpcommon *uc, struct udpsocks *socks)
 407 {
 408     int i;
 409     for (i=0; i<socks->n_socks; i++)
 410         udp_destroy_socket(uc,&socks->socks[i]);
 411 }
 412
 413 static void udp_childpersist_hook(void *sst, uint32_t new_phase)
 414 {
 415     struct udp *st=sst;
 416     udp_socks_childpersist(&st->uc,&st->socks);
 417 }
 418
 419 static void udp_phase_hook(void *sst, uint32_t new_phase)
 420 {
 421     struct udp *st=sst;
 422     struct udpsocks *socks=&st->socks;
 423     struct udpcommon *uc=&st->uc;
 424     int i;
 425     bool_t anydone=0;
 426
 427     for (i=0; i<socks->n_socks; i++) {
 428         bool_t required=st->addr_configured
 429             || (!anydone && i==socks->n_socks-1);
 430         anydone += udp_make_socket(uc,&socks->socks[i],
 431                                    required ? M_FATAL : M_WARNING);
 432     }
 433
 434     udp_socks_register(uc,socks, uc->use_proxy ? "proxy" : "socket");
 435
 436     add_hook(PHASE_CHILDPERSIST,udp_childpersist_hook,st);
 437 }
 438
 439 static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context,
 440                          list_t *args)
 441 {
 442     static unsigned counter;
 443
 444     struct udp *st;
 445     list_t *caddrl;
 446     list_t *l;
 447     uint32_t a;
 448     int i;
 449
 450     COMM_APPLY(st,&st->uc.cc,udp_,"udp",loc);
 451     COMM_APPLY_STANDARD(st,&st->uc.cc,"udp",args);
 452     UDP_APPLY_STANDARD(st,&st->uc,"udp");
 453
 454     struct udpcommon *uc=&st->uc;
 455     struct udpsocks *socks=&st->socks;
 456     struct commcommon *cc=&uc->cc;
 457
 458     st->counter=counter++;
 459
 460     union iaddr defaultaddrs[] = {
 461 #ifdef CONFIG_IPV6
 462         { .sin6 = { .sin6_family=AF_INET6,
 463                     .sin6_port=htons(uc->port),
 464                     .sin6_addr=IN6ADDR_ANY_INIT } },
 465 #endif
 466         { .sin = { .sin_family=AF_INET,
 467                    .sin_port=htons(uc->port),
 468                    .sin_addr= { .s_addr=INADDR_ANY } } }
 469     };
 470
 471     caddrl=dict_lookup(d,"address");
 472     st->addr_configured=!!caddrl;
 473     socks->n_socks=st->addr_configured ? list_length(caddrl)
 474         : (int)ARRAY_SIZE(defaultaddrs);
 475     if (socks->n_socks<=0 || socks->n_socks>UDP_MAX_SOCKETS)
 476         cfgfatal(cc->loc,"udp","`address' must be 1..%d addresses",
 477                  UDP_MAX_SOCKETS);
 478
 479     for (i=0; i<socks->n_socks; i++) {
 480         struct udpsock *us=&socks->socks[i];
 481         if (!st->addr_configured) {
 482             us->addr=defaultaddrs[i];
 483         } else {
 484             string_item_to_iaddr(list_elem(caddrl,i),uc->port,&us->addr,"udp");
 485         }
 486         us->fd=-1;
 487     }
 488
 489     l=dict_lookup(d,"proxy");
 490     if (l) {
 491         uc->use_proxy=True;
 492         uc->proxy.sa.sa_family=AF_INET;
 493         item=list_elem(l,0);
 494         if (!item || item->type!=t_string) {
 495             cfgfatal(cc->loc,"udp","proxy must supply ""addr"",port\n");
 496         }
 497         a=string_item_to_ipaddr(item,"proxy");
 498         uc->proxy.sin.sin_addr.s_addr=htonl(a);
 499         item=list_elem(l,1);
 500         if (!item || item->type!=t_number) {
 501             cfgfatal(cc->loc,"udp","proxy must supply ""addr"",port\n");
 502         }
 503         uc->proxy.sin.sin_port=htons(item->data.number);
 504     }
 505
 506     update_max_start_pad(&comm_max_start_pad, uc->use_proxy ? 8 : 0);
 507
 508     add_hook(PHASE_GETRESOURCES,udp_phase_hook,st);
 509
 510     return new_closure(&cc->cl);
 511 }
 512
 513 void udp_module(dict_t *dict)
 514 {
 515     add_closure(dict,"udp",udp_apply);
 516 }