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