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