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 ? "&" : "",
  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 static void udp_socks_afterpoll(void *state, struct pollfd *fds, int nfds)
  76 {
  77     struct udpsocks *socks=state;
  78     struct udpcommon *uc=socks->uc;
  79     union iaddr from;
  80     socklen_t fromlen;
  81     bool_t done;
  82     int rv;
  83     int i;
  84
  85     struct commcommon *cc=&uc->cc;
  86
  87     for (i=0; i<socks->n_socks; i++) {
  88         if (i>=nfds) continue;
  89         if (!(fds[i].revents & POLLIN)) continue;
  90         assert(fds[i].fd == socks->socks[i].fd);
  91         int fd=socks->socks[i].fd;
  92         do {
  93             fromlen=sizeof(from);
  94             BUF_ASSERT_FREE(cc->rbuf);
  95             BUF_ALLOC(cc->rbuf,"udp_afterpoll");
  96             buffer_init(cc->rbuf,calculate_max_start_pad());
  97             rv=recvfrom(fd, cc->rbuf->start,
  98                         buf_remaining_space(cc->rbuf),
  99                         0, &from.sa, &fromlen);
 100             if (rv>0) {
 101                 cc->rbuf->size=rv;
 102                 if (uc->use_proxy) {
 103                     /* Check that the packet came from our poxy server;
 104                        we shouldn't be contacted directly by anybody else
 105                        (since they can trivially forge source addresses) */
 106                     if (!iaddr_equal(&from,&uc->proxy)) {
 107                         Message(M_INFO,"udp: received packet that's not "
 108                                 "from the proxy\n");
 109                         BUF_FREE(cc->rbuf);
 110                         continue;
 111                     }
 112                     /* proxy protocol supports ipv4 transport only */
 113                     from.sa.sa_family=AF_INET;
 114                     BUF_GET_BYTES(unprepend,cc->rbuf,&from.sin.sin_addr,4);
 115                     buf_unprepend(cc->rbuf,2);
 116                     BUF_GET_BYTES(unprepend,cc->rbuf,&from.sin.sin_port,2);
 117                 }
 118                 struct comm_addr ca;
 119                 ca.comm=&cc->ops;
 120                 ca.ia=from;
 121                 ca.ix=i;
 122                 done=comm_notify(&cc->notify, cc->rbuf, &ca);
 123                 if (!done) {
 124                     uint32_t msgtype;
 125                     if (cc->rbuf->size>12 /* prevents traffic amplification */
 126                         && ((msgtype=get_uint32(cc->rbuf->start+8))
 127                             != LABEL_NAK)) {
 128                         uint32_t source,dest;
 129                         /* Manufacture and send NAK packet */
 130                         source=get_uint32(cc->rbuf->start); /* Us */
 131                         dest=get_uint32(cc->rbuf->start+4); /* Them */
 132                         send_nak(&ca,source,dest,msgtype,cc->rbuf,"unwanted");
 133                     }
 134                     BUF_FREE(cc->rbuf);
 135                 }
 136                 BUF_ASSERT_FREE(cc->rbuf);
 137             } else {
 138                 BUF_FREE(cc->rbuf);
 139             }
 140         } while (rv>=0);
 141     }
 142 }
 143
 144 static bool_t udp_sendmsg(void *commst, struct buffer_if *buf,
 145                           const struct comm_addr *dest)
 146 {
 147     struct udp *st=commst;
 148     struct udpcommon *uc=&st->uc;
 149     struct udpsocks *socks=&st->socks;
 150     uint8_t *sa;
 151
 152     if (uc->use_proxy) {
 153         sa=buf_prepend(buf,8);
 154         if (dest->ia.sa.sa_family != AF_INET) {
 155             Message(M_INFO,
 156                "udp: proxy means dropping outgoing non-IPv4 packet to %s\n",
 157                     iaddr_to_string(&dest->ia));
 158             return False;
 159         }
 160         memcpy(sa,&dest->ia.sin.sin_addr,4);
 161         memset(sa+4,0,4);
 162         memcpy(sa+6,&dest->ia.sin.sin_port,2);
 163         sendto(socks->socks[0].fd,sa,buf->size+8,0,&uc->proxy.sa,
 164                iaddr_socklen(&uc->proxy));
 165         buf_unprepend(buf,8);
 166     } else {
 167         int i,r;
 168         bool_t allunsupported=True;
 169         for (i=0; i<socks->n_socks; i++) {
 170             if (dest->ia.sa.sa_family != socks->socks[i].addr.sa.sa_family)
 171                 /* no point even trying */
 172                 continue;
 173             r=sendto(socks->socks[i].fd, buf->start, buf->size, 0,
 174                      &dest->ia.sa, iaddr_socklen(&dest->ia));
 175             if (r>=0) return True;
 176             if (!(errno==EAFNOSUPPORT || errno==ENETUNREACH))
 177                 /* who knows what that error means? */
 178                 allunsupported=False;
 179         }
 180         return !allunsupported; /* see doc for comm_sendmsg_fn in secnet.h */
 181     }
 182
 183     return True;
 184 }
 185
 186 bool_t udp_make_socket(struct udpcommon *uc, struct udpsock *us,
 187                        int failmsgclass)
 188 {
 189     const union iaddr *addr=&us->addr;
 190     struct commcommon *cc=&uc->cc;
 191     us->fd=-1;
 192
 193 #define FAIL_LG 0, cc->cl.description, &cc->loc, failmsgclass
 194 #define FAIL(...) do{                                           \
 195         lg_perror(FAIL_LG,errno,__VA_ARGS__);   \
 196         goto failed;                                            \
 197     }while(0)
 198
 199     us->fd=socket(addr->sa.sa_family, SOCK_DGRAM, IPPROTO_UDP);
 200     if (us->fd<0) FAIL("socket");
 201     if (fcntl(us->fd, F_SETFL, fcntl(us->fd, F_GETFL)|O_NONBLOCK)==-1)
 202         FAIL("fcntl(set O_NONBLOCK)");
 203     setcloexec(us->fd);
 204 #ifdef CONFIG_IPV6
 205     if (addr->sa.sa_family==AF_INET6) {
 206         int r;
 207         int optval=1;
 208         socklen_t optlen=sizeof(optval);
 209         r=setsockopt(us->fd,IPPROTO_IPV6,IPV6_V6ONLY,&optval,optlen);
 210         if (r) FAIL("setsockopt(,IPV6_V6ONLY,&1,)");
 211     }
 212 #endif
 213
 214     if (uc->authbind) {
 215         pid_t c;
 216         int status;
 217
 218         /* XXX this fork() and waitpid() business needs to be hidden
 219            in some system-specific library functions. */
 220         c=fork();
 221         if (c==-1)
 222             FAIL("fork() for authbind");
 223         if (c==0) {
 224             char *argv[5], addrstr[33], portstr[5];
 225             const char *addrfam;
 226             int port;
 227             switch (addr->sa.sa_family) {
 228             case AF_INET:
 229                 sprintf(addrstr,"%08lX",(long)addr->sin.sin_addr.s_addr);
 230                 port=addr->sin.sin_port;
 231                 addrfam=NULL;
 232                 break;
 233 #ifdef CONFIG_IPV6
 234             case AF_INET6: {
 235                 int i;
 236                 for (i=0; i<16; i++)
 237                     sprintf(addrstr+i*2,"%02X",addr->sin6.sin6_addr.s6_addr[i]);
 238                 port=addr->sin6.sin6_port;
 239                 addrfam="6";
 240                 break;
 241             }
 242 #endif /*CONFIG_IPV6*/
 243             default:
 244                 fatal("udp (%s:%d): unsupported address family for authbind",
 245                       cc->loc.file,cc->loc.line);
 246             }
 247             sprintf(portstr,"%04X",port);
 248             argv[0]=uc->authbind;
 249             argv[1]=addrstr;
 250             argv[2]=portstr;
 251             argv[3]=(char*)addrfam;
 252             argv[4]=NULL;
 253             dup2(us->fd,0);
 254             execvp(uc->authbind,argv);
 255             _exit(255);
 256         }
 257         while (waitpid(c,&status,0)==-1) {
 258             if (errno==EINTR) continue;
 259             FAIL("waitpid for authbind");
 260         }
 261         if (status) {
 262             if (WIFEXITED(status) && WEXITSTATUS(status)<127) {
 263                 int es=WEXITSTATUS(status);
 264                 lg_perror(FAIL_LG,es,
 265                           "authbind exited with error exit status %d;"
 266                           " indicates error",es);
 267             } else {
 268                 lg_exitstatus(FAIL_LG,status,"authbind");
 269             }
 270             goto failed;
 271         }
 272     } else {
 273         if (bind(us->fd, &addr->sa, iaddr_socklen(addr))!=0)
 274             FAIL("bind (%s)",iaddr_to_string(addr));
 275     }
 276     return True;
 277
 278 failed:
 279     if (us->fd>=0) {
 280         close(us->fd);
 281         us->fd=-1;
 282     }
 283     return False;
 284
 285 #undef FAIL
 286 }
 287
 288 void udp_socks_register(struct udpcommon *uc, struct udpsocks *socks)
 289 {
 290     socks->uc=uc;
 291     socks->interest=
 292         register_for_poll(socks,udp_socks_beforepoll,udp_socks_afterpoll,"udp");
 293 }
 294
 295 void udp_socks_deregister(struct udpcommon *uc, struct udpsocks *socks)
 296 {
 297     socks->uc=uc;
 298     deregister_for_poll(socks->interest);
 299 }
 300
 301 static void udp_phase_hook(void *sst, uint32_t new_phase)
 302 {
 303     struct udp *st=sst;
 304     struct udpsocks *socks=&st->socks;
 305     struct udpcommon *uc=&st->uc;
 306     int i;
 307     for (i=0; i<socks->n_socks; i++)
 308         udp_make_socket(uc,&socks->socks[i],M_FATAL);
 309
 310     udp_socks_register(uc,socks);
 311 }
 312
 313 static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context,
 314                          list_t *args)
 315 {
 316     struct udp *st;
 317     list_t *caddrl;
 318     list_t *l;
 319     uint32_t a;
 320     int i;
 321
 322     COMM_APPLY(st,&st->uc.cc,udp_,"udp",loc);
 323     COMM_APPLY_STANDARD(st,&st->uc.cc,"udp",args);
 324     UDP_APPLY_STANDARD(st,&st->uc,"udp");
 325
 326     struct udpcommon *uc=&st->uc;
 327     struct udpsocks *socks=&st->socks;
 328     struct commcommon *cc=&uc->cc;
 329
 330     union iaddr defaultaddrs[] = {
 331 #ifdef CONFIG_IPV6
 332         { .sin6 = { .sin6_family=AF_INET6,
 333                     .sin6_port=htons(uc->port),
 334                     .sin6_addr=IN6ADDR_ANY_INIT } },
 335 #endif
 336         { .sin = { .sin_family=AF_INET,
 337                    .sin_port=htons(uc->port),
 338                    .sin_addr= { .s_addr=INADDR_ANY } } }
 339     };
 340
 341     caddrl=dict_lookup(d,"address");
 342     socks->n_socks=caddrl ? list_length(caddrl) : (int)ARRAY_SIZE(defaultaddrs);
 343     if (socks->n_socks<=0 || socks->n_socks>UDP_MAX_SOCKETS)
 344         cfgfatal(cc->loc,"udp","`address' must be 1..%d addresses",
 345                  UDP_MAX_SOCKETS);
 346
 347     for (i=0; i<socks->n_socks; i++) {
 348         struct udpsock *us=&socks->socks[i];
 349         if (!list_length(caddrl)) {
 350             us->addr=defaultaddrs[i];
 351         } else {
 352             string_item_to_iaddr(list_elem(caddrl,i),uc->port,&us->addr,"udp");
 353         }
 354         us->fd=-1;
 355     }
 356
 357     l=dict_lookup(d,"proxy");
 358     if (l) {
 359         uc->use_proxy=True;
 360         uc->proxy.sa.sa_family=AF_INET;
 361         item=list_elem(l,0);
 362         if (!item || item->type!=t_string) {
 363             cfgfatal(cc->loc,"udp","proxy must supply ""addr"",port\n");
 364         }
 365         a=string_item_to_ipaddr(item,"proxy");
 366         uc->proxy.sin.sin_addr.s_addr=htonl(a);
 367         item=list_elem(l,1);
 368         if (!item || item->type!=t_number) {
 369             cfgfatal(cc->loc,"udp","proxy must supply ""addr"",port\n");
 370         }
 371         uc->proxy.sin.sin_port=htons(item->data.number);
 372     }
 373
 374     update_max_start_pad(&comm_max_start_pad, uc->use_proxy ? 8 : 0);
 375
 376     add_hook(PHASE_GETRESOURCES,udp_phase_hook,st);
 377
 378     return new_closure(&cc->cl);
 379 }
 380
 381 void udp_module(dict_t *dict)
 382 {
 383     add_closure(dict,"udp",udp_apply);
 384 }