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->notify, 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,"unwanted");
 190                     }
 191                     BUF_FREE(cc->rbuf);
 192                 }
 193                 BUF_ASSERT_FREE(cc->rbuf);
 194             } else { /* rv<=0 */
 195                 if (errno!=EINTR && !iswouldblock(errno))
 196                     udp_sock_experienced(0,uc,socks,us, 0,0, rv,errno);
 197                 BUF_FREE(cc->rbuf);
 198             }
 199         } while (rv>=0);
 200     }
 201 }
 202
 203 static bool_t udp_sendmsg(void *commst, struct buffer_if *buf,
 204                           const struct comm_addr *dest,
 205                           struct comm_clientinfo *clientinfo)
 206 {
 207     struct udp *st=commst;
 208     struct udpcommon *uc=&st->uc;
 209     struct udpsocks *socks=&st->socks;
 210     uint8_t *sa;
 211
 212     if (uc->use_proxy) {
 213         struct udpsock *us=&socks->socks[0];
 214         sa=buf_prepend(buf,8);
 215         if (dest->ia.sa.sa_family != AF_INET) {
 216             Message(M_INFO,
 217                "udp: proxy means dropping outgoing non-IPv4 packet to %s\n",
 218                     iaddr_to_string(&dest->ia));
 219             return False;
 220         }
 221         memcpy(sa,&dest->ia.sin.sin_addr,4);
 222         memset(sa+4,0,4);
 223         memcpy(sa+6,&dest->ia.sin.sin_port,2);
 224         int r=sendto(us->fd,sa,buf->size+8,0,&uc->proxy.sa,
 225                iaddr_socklen(&uc->proxy));
 226         udp_sock_experienced(0,uc,socks,us, &dest->ia,0, r,errno);
 227         buf_unprepend(buf,8);
 228     } else {
 229         int i,r;
 230         bool_t allunsupported=True;
 231         int af=dest->ia.sa.sa_family;
 232         for (i=0; i<socks->n_socks; i++) {
 233             struct udpsock *us=&socks->socks[i];
 234             if (us->addr.sa.sa_family != af)
 235                 /* no point even trying */
 236                 continue;
 237             r=sendto(us->fd, buf->start, buf->size, 0,
 238                      &dest->ia.sa, iaddr_socklen(&dest->ia));
 239             udp_sock_experienced(0,uc,socks,us, &dest->ia,af, r,errno);
 240             if (r>=0) return True;
 241             if (!(errno==EAFNOSUPPORT || errno==ENETUNREACH))
 242                 /* who knows what that error means? */
 243                 allunsupported=False;
 244         }
 245         return !allunsupported; /* see doc for comm_sendmsg_fn in secnet.h */
 246     }
 247
 248     return True;
 249 }
 250
 251 void udp_destroy_socket(struct udpcommon *uc, struct udpsock *us)
 252 {
 253     if (us->fd>=0) {
 254         close(us->fd);
 255         us->fd=-1;
 256     }
 257 }
 258
 259 #define FAIL_LG 0, cc->cl.description, &cc->loc, failmsgclass
 260 #define FAIL(...) do{                                           \
 261         lg_perror(FAIL_LG,errno,__VA_ARGS__);   \
 262         goto failed;                                            \
 263     }while(0)
 264
 265 static bool_t record_socket_gotaddr(struct udpcommon *uc, struct udpsock *us,
 266                                     int failmsgclass)
 267 {
 268     struct commcommon *cc=&uc->cc;
 269     socklen_t salen=sizeof(us->addr);
 270     int r=getsockname(us->fd,&us->addr.sa,&salen);
 271     if (r) FAIL("getsockname()");
 272     if ((size_t)salen>sizeof(us->addr)) /* cast squashes clang warning */
 273       { errno=0; FAIL("getsockname() length"); }
 274     return True;
 275
 276  failed:
 277     return False;
 278 }
 279
 280 bool_t udp_import_socket(struct udpcommon *uc, struct udpsock *us,
 281                          int failmsgclass, int fd)
 282 {
 283     FILLZERO(us->experienced);
 284     us->fd=fd;
 285     return record_socket_gotaddr(uc,us,failmsgclass);
 286 }
 287
 288 bool_t udp_make_socket(struct udpcommon *uc, struct udpsock *us,
 289                        int failmsgclass)
 290 {
 291     const union iaddr *addr=&us->addr;
 292     struct commcommon *cc=&uc->cc;
 293     us->fd=-1;
 294
 295     FILLZERO(us->experienced);
 296     us->fd=socket(addr->sa.sa_family, SOCK_DGRAM, IPPROTO_UDP);
 297     if (us->fd<0) FAIL("socket");
 298     setnonblock(us->fd);
 299     setcloexec(us->fd);
 300 #ifdef CONFIG_IPV6
 301     if (addr->sa.sa_family==AF_INET6) {
 302         int r;
 303         int optval=1;
 304         socklen_t optlen=sizeof(optval);
 305         r=setsockopt(us->fd,IPPROTO_IPV6,IPV6_V6ONLY,&optval,optlen);
 306         if (r) FAIL("setsockopt(,IPV6_V6ONLY,&1,)");
 307     }
 308 #endif
 309
 310     if (uc->authbind) {
 311         pid_t c;
 312         int status;
 313         char desc[200];
 314         snprintf(desc,sizeof(desc),"authbind for %s: %s",
 315                  iaddr_to_string(addr), uc->authbind);
 316
 317         /* XXX this fork() and waitpid() business needs to be hidden
 318            in some system-specific library functions. */
 319         c=fork();
 320         if (c==-1)
 321             FAIL("fork() for authbind");
 322         if (c==0) {
 323             char *argv[5], addrstr[33], portstr[5];
 324             const char *addrfam;
 325             int port;
 326             afterfork();
 327             switch (addr->sa.sa_family) {
 328             case AF_INET:
 329                 sprintf(addrstr,"%08lX",(long)addr->sin.sin_addr.s_addr);
 330                 port=addr->sin.sin_port;
 331                 addrfam=NULL;
 332                 break;
 333 #ifdef CONFIG_IPV6
 334             case AF_INET6: {
 335                 int i;
 336                 for (i=0; i<16; i++)
 337                     sprintf(addrstr+i*2,"%02X",addr->sin6.sin6_addr.s6_addr[i]);
 338                 port=addr->sin6.sin6_port;
 339                 addrfam="6";
 340                 break;
 341             }
 342 #endif /*CONFIG_IPV6*/
 343             default:
 344                 fatal("udp (%s:%d): unsupported address family for authbind",
 345                       cc->loc.file,cc->loc.line);
 346             }
 347             sprintf(portstr,"%04X",port);
 348             argv[0]=uc->authbind;
 349             argv[1]=addrstr;
 350             argv[2]=portstr;
 351             argv[3]=(char*)addrfam;
 352             argv[4]=NULL;
 353             dup2(us->fd,0);
 354             execvp(uc->authbind,argv);
 355             _exit(255);
 356         }
 357         while (waitpid(c,&status,0)==-1) {
 358             if (errno==EINTR) continue;
 359             FAIL("waitpid for authbind");
 360         }
 361         if (status) {
 362             if (WIFEXITED(status) && WEXITSTATUS(status)<127) {
 363                 int es=WEXITSTATUS(status);
 364                 lg_perror(FAIL_LG,es,
 365                           "%s exited with error exit status %d;"
 366                           " indicates error",desc,es);
 367             } else {
 368                 lg_exitstatus(FAIL_LG,status,desc);
 369             }
 370             goto failed;
 371         }
 372     } else {
 373         if (bind(us->fd, &addr->sa, iaddr_socklen(addr))!=0)
 374             FAIL("bind (%s)",iaddr_to_string(addr));
 375     }
 376
 377     bool_t ok=record_socket_gotaddr(uc,us,failmsgclass);
 378     if (!ok) goto failed;
 379
 380     return True;
 381
 382 failed:
 383     udp_destroy_socket(uc,us);
 384     return False;
 385 }
 386
 387 #undef FAIL
 388
 389 void udp_socks_register(struct udpcommon *uc, struct udpsocks *socks,
 390                         const char *desc)
 391 {
 392     socks->uc=uc;
 393     socks->desc=desc;
 394     socks->interest=
 395         register_for_poll(socks,udp_socks_beforepoll,udp_socks_afterpoll,"udp");
 396 }
 397
 398 void udp_socks_deregister(struct udpcommon *uc, struct udpsocks *socks)
 399 {
 400     socks->uc=uc;
 401     deregister_for_poll(socks->interest);
 402 }
 403
 404 void udp_socks_childpersist(struct udpcommon *uc, struct udpsocks *socks)
 405 {
 406     int i;
 407     for (i=0; i<socks->n_socks; i++)
 408         udp_destroy_socket(uc,&socks->socks[i]);
 409 }
 410
 411 static void udp_childpersist_hook(void *sst, uint32_t new_phase)
 412 {
 413     struct udp *st=sst;
 414     udp_socks_childpersist(&st->uc,&st->socks);
 415 }
 416
 417 static void udp_phase_hook(void *sst, uint32_t new_phase)
 418 {
 419     struct udp *st=sst;
 420     struct udpsocks *socks=&st->socks;
 421     struct udpcommon *uc=&st->uc;
 422     int i;
 423     bool_t anydone=0;
 424
 425     for (i=0; i<socks->n_socks; i++) {
 426         bool_t required=st->addr_configured
 427             || (!anydone && i==socks->n_socks-1);
 428         anydone += udp_make_socket(uc,&socks->socks[i],
 429                                    required ? M_FATAL : M_WARNING);
 430     }
 431
 432     udp_socks_register(uc,socks, uc->use_proxy ? "proxy" : "socket");
 433
 434     add_hook(PHASE_CHILDPERSIST,udp_childpersist_hook,st);
 435 }
 436
 437 static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context,
 438                          list_t *args)
 439 {
 440     static unsigned counter;
 441
 442     struct udp *st;
 443     list_t *caddrl;
 444     list_t *l;
 445     uint32_t a;
 446     int i;
 447
 448     COMM_APPLY(st,&st->uc.cc,udp_,"udp",loc);
 449     COMM_APPLY_STANDARD(st,&st->uc.cc,"udp",args);
 450     UDP_APPLY_STANDARD(st,&st->uc,"udp");
 451
 452     struct udpcommon *uc=&st->uc;
 453     struct udpsocks *socks=&st->socks;
 454     struct commcommon *cc=&uc->cc;
 455
 456     st->counter=counter++;
 457
 458     union iaddr defaultaddrs[] = {
 459 #ifdef CONFIG_IPV6
 460         { .sin6 = { .sin6_family=AF_INET6,
 461                     .sin6_port=htons(uc->port),
 462                     .sin6_addr=IN6ADDR_ANY_INIT } },
 463 #endif
 464         { .sin = { .sin_family=AF_INET,
 465                    .sin_port=htons(uc->port),
 466                    .sin_addr= { .s_addr=INADDR_ANY } } }
 467     };
 468
 469     caddrl=dict_lookup(d,"address");
 470     st->addr_configured=!!caddrl;
 471     socks->n_socks=st->addr_configured ? list_length(caddrl)
 472         : (int)ARRAY_SIZE(defaultaddrs);
 473     if (socks->n_socks<=0 || socks->n_socks>UDP_MAX_SOCKETS)
 474         cfgfatal(cc->loc,"udp","`address' must be 1..%d addresses",
 475                  UDP_MAX_SOCKETS);
 476
 477     for (i=0; i<socks->n_socks; i++) {
 478         struct udpsock *us=&socks->socks[i];
 479         if (!st->addr_configured) {
 480             us->addr=defaultaddrs[i];
 481         } else {
 482             string_item_to_iaddr(list_elem(caddrl,i),uc->port,&us->addr,"udp");
 483         }
 484         us->fd=-1;
 485     }
 486
 487     l=dict_lookup(d,"proxy");
 488     if (l) {
 489         uc->use_proxy=True;
 490         uc->proxy.sa.sa_family=AF_INET;
 491         item=list_elem(l,0);
 492         if (!item || item->type!=t_string) {
 493             cfgfatal(cc->loc,"udp","proxy must supply ""addr"",port\n");
 494         }
 495         a=string_item_to_ipaddr(item,"proxy");
 496         uc->proxy.sin.sin_addr.s_addr=htonl(a);
 497         item=list_elem(l,1);
 498         if (!item || item->type!=t_number) {
 499             cfgfatal(cc->loc,"udp","proxy must supply ""addr"",port\n");
 500         }
 501         uc->proxy.sin.sin_port=htons(item->data.number);
 502     }
 503
 504     update_max_start_pad(&comm_max_start_pad, uc->use_proxy ? 8 : 0);
 505
 506     add_hook(PHASE_GETRESOURCES,udp_phase_hook,st);
 507
 508     return new_closure(&cc->cl);
 509 }
 510
 511 void udp_module(dict_t *dict)
 512 {
 513     add_closure(dict,"udp",udp_apply);
 514 }