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 static const char *udp_addr_to_string(void *commst, const struct comm_addr *ca)
  36 {
  37     struct udp *st=commst;
  38     struct udpsocks *socks=&st->socks;
  39     static char sbuf[100];
  40     int ix=ca->ix>=0 ? ca->ix : 0;
  41
  42     assert(ix>=0 && ix<socks->n_socks);
  43     snprintf(sbuf, sizeof(sbuf), "udp:%d:%s-%s",
  44              ca->ix,
  45              iaddr_to_string(&socks->socks[ix].addr),
  46              iaddr_to_string(&ca->ia));
  47     return sbuf;
  48 }
  49
  50 static int udp_socks_beforepoll(void *state, struct pollfd *fds, int *nfds_io,
  51                                 int *timeout_io)
  52 {
  53     struct udpsocks *socks=state;
  54     int i;
  55     BEFOREPOLL_WANT_FDS(socks->n_socks);
  56     for (i=0; i<socks->n_socks; i++) {
  57         fds[i].fd=socks->socks[i].fd;
  58         fds[i].events=POLLIN;
  59     }
  60     return 0;
  61 }
  62
  63 static void udp_socks_afterpoll(void *state, struct pollfd *fds, int nfds)
  64 {
  65     struct udpsocks *socks=state;
  66     struct udpcommon *uc=socks->uc;
  67     union iaddr from;
  68     socklen_t fromlen;
  69     bool_t done;
  70     int rv;
  71     int i;
  72
  73     struct commcommon *cc=&uc->cc;
  74
  75     for (i=0; i<socks->n_socks; i++) {
  76         struct udpsock *us=&socks->socks[i];
  77         if (i>=nfds) continue;
  78         if (!(fds[i].revents & POLLIN)) continue;
  79         assert(fds[i].fd == us->fd);
  80         int fd=us->fd;
  81         do {
  82             FILLZERO(from);
  83             fromlen=sizeof(from);
  84             BUF_ASSERT_FREE(cc->rbuf);
  85             BUF_ALLOC(cc->rbuf,"udp_afterpoll");
  86             buffer_init(cc->rbuf,calculate_max_start_pad());
  87             rv=recvfrom(fd, cc->rbuf->start,
  88                         buf_remaining_space(cc->rbuf),
  89                         0, (struct sockaddr *)&from, &fromlen);
  90             if (rv>0) {
  91                 cc->rbuf->size=rv;
  92                 if (uc->use_proxy) {
  93                     /* Check that the packet came from our poxy server;
  94                        we shouldn't be contacted directly by anybody else
  95                        (since they can trivially forge source addresses) */
  96                     if (!iaddr_equal(&from,&uc->proxy)) {
  97                         Message(M_INFO,"udp: received packet that's not "
  98                                 "from the proxy\n");
  99                         BUF_FREE(cc->rbuf);
 100                         continue;
 101                     }
 102                     /* proxy protocol supports ipv4 transport only */
 103                     FILLZERO(from);
 104                     from.sa.sa_family=AF_INET;
 105                     memcpy(&from.sin.sin_addr,buf_unprepend(cc->rbuf,4),4);
 106                     buf_unprepend(cc->rbuf,2);
 107                     memcpy(&from.sin.sin_port,buf_unprepend(cc->rbuf,2),2);
 108                 }
 109                 struct comm_addr ca;
 110                 FILLZERO(ca);
 111                 ca.comm=&cc->ops;
 112                 ca.ia=from;
 113                 ca.ix=i;
 114                 done=comm_notify(&cc->notify, cc->rbuf, &ca);
 115                 if (!done) {
 116                     uint32_t msgtype;
 117                     if (cc->rbuf->size>12 /* prevents traffic amplification */
 118                         && ((msgtype=get_uint32(cc->rbuf->start+8))
 119                             != LABEL_NAK)) {
 120                         uint32_t source,dest;
 121                         /* Manufacture and send NAK packet */
 122                         source=get_uint32(cc->rbuf->start); /* Us */
 123                         dest=get_uint32(cc->rbuf->start+4); /* Them */
 124                         send_nak(&ca,source,dest,msgtype,cc->rbuf,"unwanted");
 125                     }
 126                     BUF_FREE(cc->rbuf);
 127                 }
 128                 BUF_ASSERT_FREE(cc->rbuf);
 129             } else { /* rv<=0 */
 130                 BUF_FREE(cc->rbuf);
 131             }
 132         } while (rv>=0);
 133     }
 134 }
 135
 136 static bool_t udp_sendmsg(void *commst, struct buffer_if *buf,
 137                           const struct comm_addr *dest)
 138 {
 139     struct udp *st=commst;
 140     struct udpcommon *uc=&st->uc;
 141     struct udpsocks *socks=&st->socks;
 142     uint8_t *sa;
 143
 144     if (uc->use_proxy) {
 145         struct udpsock *us=&socks->socks[0];
 146         sa=buf_prepend(buf,8);
 147         if (dest->ia.sa.sa_family != AF_INET) {
 148             Message(M_INFO,
 149                "udp: proxy means dropping outgoing non-IPv4 packet to %s\n",
 150                     iaddr_to_string(&dest->ia));
 151             return False;
 152         }
 153         memcpy(sa,&dest->ia.sin.sin_addr,4);
 154         memset(sa+4,0,4);
 155         memcpy(sa+6,&dest->ia.sin.sin_port,2);
 156         sendto(us->fd,sa,buf->size+8,0,(struct sockaddr *)&uc->proxy,
 157                sizeof(uc->proxy));
 158         buf_unprepend(buf,8);
 159     } else {
 160         int i,r;
 161         bool_t allunsupported=True;
 162         int af=dest->ia.sa.sa_family;
 163         for (i=0; i<socks->n_socks; i++) {
 164             struct udpsock *us=&socks->socks[i];
 165             if (us->addr.sa.sa_family != af)
 166                 /* no point even trying */
 167                 continue;
 168             r=sendto(us->fd, buf->start, buf->size, 0,
 169                      &dest->ia.sa, iaddr_socklen(&dest->ia));
 170             if (!r) return True;
 171             if (!(errno==EAFNOSUPPORT || errno==ENETUNREACH))
 172                 /* who knows what that error means? */
 173                 allunsupported=False;
 174         }
 175         return !allunsupported; /* see doc for comm_sendmsg_fn in secnet.h */
 176     }
 177
 178     return True;
 179 }
 180
 181 void udp_destroy_socket(struct udpcommon *uc, struct udpsock *us)
 182 {
 183     if (us->fd>=0) {
 184         close(us->fd);
 185         us->fd=-1;
 186     }
 187 }
 188
 189 bool_t udp_make_socket(struct udpcommon *uc, struct udpsock *us,
 190                        int failmsgclass)
 191 {
 192     const union iaddr *addr=&us->addr;
 193     struct commcommon *cc=&uc->cc;
 194     us->fd=-1;
 195
 196 #define FAIL_LG 0, cc->cl.description, &cc->loc, failmsgclass
 197 #define FAIL(...) do{                                           \
 198         lg_perror(FAIL_LG,errno,__VA_ARGS__);   \
 199         goto failed;                                            \
 200     }while(0)
 201
 202     us->fd=socket(addr->sa.sa_family, SOCK_DGRAM, IPPROTO_UDP);
 203     if (us->fd<0) FAIL("socket");
 204     setnonblock(us->fd);
 205     setcloexec(us->fd);
 206 #ifdef CONFIG_IPV6
 207     if (addr->sa.sa_family==AF_INET6) {
 208         int r;
 209         int optval=1;
 210         socklen_t optlen=sizeof(optval);
 211         r=setsockopt(us->fd,IPPROTO_IPV6,IPV6_V6ONLY,&optval,optlen);
 212         if (r) FAIL("setsockopt(,IPV6_V6ONLY,&1,)");
 213     }
 214 #endif
 215
 216     if (uc->authbind) {
 217         pid_t c;
 218         int status;
 219
 220         /* XXX this fork() and waitpid() business needs to be hidden
 221            in some system-specific library functions. */
 222         c=fork();
 223         if (c==-1)
 224             FAIL("fork() for authbind");
 225         if (c==0) {
 226             char *argv[5], addrstr[33], portstr[5];
 227             const char *addrfam;
 228             int port;
 229             afterfork();
 230             switch (addr->sa.sa_family) {
 231             case AF_INET:
 232                 sprintf(addrstr,"%08lX",(long)addr->sin.sin_addr.s_addr);
 233                 port=addr->sin.sin_port;
 234                 addrfam=NULL;
 235                 break;
 236 #ifdef CONFIG_IPV6
 237             case AF_INET6: {
 238                 int i;
 239                 for (i=0; i<16; i++)
 240                     sprintf(addrstr+i*2,"%02X",addr->sin6.sin6_addr.s6_addr[i]);
 241                 port=addr->sin6.sin6_port;
 242                 addrfam="6";
 243                 break;
 244             }
 245 #endif /*CONFIG_IPV6*/
 246             default:
 247                 fatal("udp (%s:%d): unsupported address family for authbind",
 248                       cc->loc.file,cc->loc.line);
 249             }
 250             sprintf(portstr,"%04X",port);
 251             argv[0]=uc->authbind;
 252             argv[1]=addrstr;
 253             argv[2]=portstr;
 254             argv[3]=(char*)addrfam;
 255             argv[4]=NULL;
 256             dup2(us->fd,0);
 257             execvp(uc->authbind,argv);
 258             _exit(255);
 259         }
 260         while (waitpid(c,&status,0)==-1) {
 261             if (errno==EINTR) continue;
 262             FAIL("waitpid for authbind");
 263         }
 264         if (status) {
 265             lg_exitstatus(FAIL_LG,status,"authbind");
 266             goto failed;
 267         }
 268     } else {
 269         if (bind(us->fd, &addr->sa, iaddr_socklen(addr))!=0)
 270             FAIL("bind (%s)",iaddr_to_string(addr));
 271     }
 272     return True;
 273
 274 failed:
 275     udp_destroy_socket(uc,us);
 276     return False;
 277
 278 #undef FAIL
 279 }
 280
 281 void udp_socks_register(struct udpcommon *uc, struct udpsocks *socks)
 282 {
 283     socks->uc=uc;
 284     socks->interest=
 285         register_for_poll(socks,udp_socks_beforepoll,udp_socks_afterpoll,"udp");
 286 }
 287
 288 void udp_socks_deregister(struct udpcommon *uc, struct udpsocks *socks)
 289 {
 290     socks->uc=uc;
 291     deregister_for_poll(socks->interest);
 292 }
 293
 294 static void udp_phase_hook(void *sst, uint32_t new_phase)
 295 {
 296     struct udp *st=sst;
 297     struct udpsocks *socks=&st->socks;
 298     struct udpcommon *uc=&st->uc;
 299     int i;
 300     for (i=0; i<socks->n_socks; i++)
 301         udp_make_socket(uc,&socks->socks[i],M_FATAL);
 302
 303     udp_socks_register(uc,socks);
 304 }
 305
 306 static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context,
 307                          list_t *args)
 308 {
 309     struct udp *st;
 310     list_t *caddrl;
 311     list_t *l;
 312     uint32_t a;
 313     int i;
 314
 315     COMM_APPLY(st,&st->uc.cc,udp_,"udp",loc);
 316     COMM_APPLY_STANDARD(st,&st->uc.cc,"udp",args);
 317     UDP_APPLY_STANDARD(st,&st->uc,"udp");
 318
 319     struct udpcommon *uc=&st->uc;
 320     struct udpsocks *socks=&st->socks;
 321     struct commcommon *cc=&uc->cc;
 322
 323     union iaddr defaultaddrs[] = {
 324 #ifdef CONFIG_IPV6
 325         { .sin6 = { .sin6_family=AF_INET6,
 326                     .sin6_port=htons(uc->port),
 327                     .sin6_addr=IN6ADDR_ANY_INIT } },
 328 #endif
 329         { .sin = { .sin_family=AF_INET,
 330                    .sin_port=htons(uc->port),
 331                    .sin_addr= { .s_addr=INADDR_ANY } } }
 332     };
 333
 334     caddrl=dict_lookup(d,"address");
 335     socks->n_socks=caddrl ? list_length(caddrl) : (int)ARRAY_SIZE(defaultaddrs);
 336     if (socks->n_socks<=0 || socks->n_socks>UDP_MAX_SOCKETS)
 337         cfgfatal(cc->loc,"udp","`address' must be 1..%d addresses",
 338                  UDP_MAX_SOCKETS);
 339
 340     for (i=0; i<socks->n_socks; i++) {
 341         struct udpsock *us=&socks->socks[i];
 342         FILLZERO(us->addr);
 343         if (!list_length(caddrl)) {
 344             us->addr=defaultaddrs[i];
 345         } else {
 346             text2iaddr(list_elem(caddrl,i),uc->port,
 347                        &us->addr,"udp");
 348         }
 349         us->fd=-1;
 350     }
 351
 352     uc->authbind=dict_read_string(d,"authbind",False,"udp",cc->loc);
 353     l=dict_lookup(d,"proxy");
 354     if (l) {
 355         uc->use_proxy=True;
 356         FILLZERO(uc->proxy);
 357         uc->proxy.sa.sa_family=AF_INET;
 358         item=list_elem(l,0);
 359         if (!item || item->type!=t_string) {
 360             cfgfatal(cc->loc,"udp","proxy must supply ""addr"",port\n");
 361         }
 362         a=string_item_to_ipaddr(item,"proxy");
 363         uc->proxy.sin.sin_addr.s_addr=htonl(a);
 364         item=list_elem(l,1);
 365         if (!item || item->type!=t_number) {
 366             cfgfatal(cc->loc,"udp","proxy must supply ""addr"",port\n");
 367         }
 368         uc->proxy.sin.sin_port=htons(item->data.number);
 369     }
 370
 371     update_max_start_pad(&comm_max_start_pad, uc->use_proxy ? 8 : 0);
 372
 373     add_hook(PHASE_GETRESOURCES,udp_phase_hook,st);
 374
 375     return new_closure(&cc->cl);
 376 }
 377
 378 void udp_module(dict_t *dict)
 379 {
 380     add_closure(dict,"udp",udp_apply);
 381 }