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 beforepoll_fn udp_beforepoll;
  29 static afterpoll_fn udp_afterpoll;
  30 static comm_sendmsg_fn udp_sendmsg;
  31
  32 struct udp {
  33     struct udpcommon uc;
  34     struct udpsocks socks;
  35 };
  36
  37 static const char *udp_addr_to_string(void *commst, const struct comm_addr *ca)
  38 {
  39     struct udp *st=commst;
  40     struct udpsocks *socks=&st->socks;
  41     static char sbuf[100];
  42     int ix=ca->ix>=0 ? ca->ix : 0;
  43
  44     assert(ix>=0 && ix<socks->n_socks);
  45     snprintf(sbuf, sizeof(sbuf), "udp:%d:%s-%s",
  46              ca->ix,
  47              iaddr_to_string(&socks->socks[ix].addr),
  48              iaddr_to_string(&ca->ia));
  49     return sbuf;
  50 }
  51
  52 int udp_socks_beforepoll(struct udpsocks *socks,
  53                          struct pollfd *fds, int *nfds_io,
  54                          int *timeout_io)
  55 {
  56     int i;
  57     BEFOREPOLL_WANT_FDS(socks->n_socks);
  58     for (i=0; i<socks->n_socks; i++) {
  59         fds[i].fd=socks->socks[i].fd;
  60         fds[i].events=POLLIN;
  61     }
  62     return 0;
  63 }
  64
  65 static int udp_beforepoll(void *state, struct pollfd *fds, int *nfds_io,
  66                           int *timeout_io)
  67 {
  68     struct udp *st=state;
  69     return udp_socks_beforepoll(&st->socks,fds,nfds_io,timeout_io);
  70 }
  71
  72 void udp_socks_afterpoll(struct udpcommon *uc, struct udpsocks *socks,
  73                          struct pollfd *fds, int nfds)
  74 {
  75     union iaddr from;
  76     socklen_t fromlen;
  77     bool_t done;
  78     int rv;
  79     int i;
  80
  81     struct commcommon *cc=&uc->cc;
  82
  83     for (i=0; i<socks->n_socks; i++) {
  84         if (i>=nfds) continue;
  85         if (!(fds[i].revents & POLLIN)) continue;
  86         assert(fds[i].fd == socks->socks[i].fd);
  87         int fd=socks->socks[i].fd;
  88         do {
  89             FILLZERO(from);
  90             fromlen=sizeof(from);
  91             BUF_ASSERT_FREE(cc->rbuf);
  92             BUF_ALLOC(cc->rbuf,"udp_afterpoll");
  93             buffer_init(cc->rbuf,calculate_max_start_pad());
  94             rv=recvfrom(fd, cc->rbuf->start,
  95                         buf_remaining_space(cc->rbuf),
  96                         0, (struct sockaddr *)&from, &fromlen);
  97             if (rv>0) {
  98                 cc->rbuf->size=rv;
  99                 if (uc->use_proxy) {
 100                     /* Check that the packet came from our poxy server;
 101                        we shouldn't be contacted directly by anybody else
 102                        (since they can trivially forge source addresses) */
 103                     if (!iaddr_equal(&from,&uc->proxy)) {
 104                         Message(M_INFO,"udp: received packet that's not "
 105                                 "from the proxy\n");
 106                         BUF_FREE(cc->rbuf);
 107                         continue;
 108                     }
 109                     /* proxy protocol supports ipv4 transport only */
 110                     FILLZERO(from);
 111                     from.sa.sa_family=AF_INET;
 112                     memcpy(&from.sin.sin_addr,buf_unprepend(cc->rbuf,4),4);
 113                     buf_unprepend(cc->rbuf,2);
 114                     memcpy(&from.sin.sin_port,buf_unprepend(cc->rbuf,2),2);
 115                 }
 116                 struct comm_addr ca;
 117                 FILLZERO(ca);
 118                 ca.comm=&cc->ops;
 119                 ca.ia=from;
 120                 ca.ix=i;
 121                 done=comm_notify(&cc->notify, cc->rbuf, &ca);
 122                 if (!done) {
 123                     uint32_t msgtype;
 124                     if (cc->rbuf->size>12 /* prevents traffic amplification */
 125                         && ((msgtype=get_uint32(cc->rbuf->start+8))
 126                             != LABEL_NAK)) {
 127                         uint32_t source,dest;
 128                         /* Manufacture and send NAK packet */
 129                         source=get_uint32(cc->rbuf->start); /* Us */
 130                         dest=get_uint32(cc->rbuf->start+4); /* Them */
 131                         send_nak(&ca,source,dest,msgtype,cc->rbuf,"unwanted");
 132                     }
 133                     BUF_FREE(cc->rbuf);
 134                 }
 135                 BUF_ASSERT_FREE(cc->rbuf);
 136             } else {
 137                 BUF_FREE(cc->rbuf);
 138             }
 139         } while (rv>=0);
 140     }
 141 }
 142
 143 static void udp_afterpoll(void *state, struct pollfd *fds, int nfds)
 144 {
 145     struct udp *st=state;
 146     return udp_socks_afterpoll(&st->uc,&st->socks,fds,nfds);
 147 }
 148
 149 static bool_t udp_sendmsg(void *commst, struct buffer_if *buf,
 150                           const struct comm_addr *dest)
 151 {
 152     struct udp *st=commst;
 153     struct udpcommon *uc=&st->uc;
 154     struct udpsocks *socks=&st->socks;
 155     uint8_t *sa;
 156
 157     if (uc->use_proxy) {
 158         sa=buf_prepend(buf,8);
 159         if (dest->ia.sa.sa_family != AF_INET) {
 160             Message(M_INFO,
 161                "udp: proxy means dropping outgoing non-IPv4 packet to %s\n",
 162                     iaddr_to_string(&dest->ia));
 163             return False;
 164         }
 165         memcpy(sa,&dest->ia.sin.sin_addr,4);
 166         memset(sa+4,0,4);
 167         memcpy(sa+6,&dest->ia.sin.sin_port,2);
 168         sendto(socks->socks[0].fd,sa,buf->size+8,0,(struct sockaddr *)&uc->proxy,
 169                sizeof(uc->proxy));
 170         buf_unprepend(buf,8);
 171     } else {
 172         int i,r;
 173         bool_t allunsupported=True;
 174         for (i=0; i<socks->n_socks; i++) {
 175             if (dest->ia.sa.sa_family != socks->socks[i].addr.sa.sa_family)
 176                 /* no point even trying */
 177                 continue;
 178             r=sendto(socks->socks[i].fd, buf->start, buf->size, 0,
 179                      &dest->ia.sa, iaddr_socklen(&dest->ia));
 180             if (!r) return True;
 181             if (!(errno==EAFNOSUPPORT || errno==ENETUNREACH))
 182                 /* who knows what that error means? */
 183                 allunsupported=False;
 184         }
 185         return !allunsupported; /* see doc for comm_sendmsg_fn in secnet.h */
 186     }
 187
 188     return True;
 189 }
 190
 191 static void udp_make_socket(struct udp *st, struct udpsock *us)
 192 {
 193     const union iaddr *addr=&us->addr;
 194     struct udpcommon *uc=&st->uc;
 195     struct commcommon *cc=&uc->cc;
 196
 197     us->fd=socket(addr->sa.sa_family, SOCK_DGRAM, IPPROTO_UDP);
 198     if (us->fd<0) {
 199         fatal_perror("udp (%s:%d): socket",cc->loc.file,cc->loc.line);
 200     }
 201     if (fcntl(us->fd, F_SETFL, fcntl(us->fd, F_GETFL)|O_NONBLOCK)==-1) {
 202         fatal_perror("udp (%s:%d): fcntl(set O_NONBLOCK)",
 203                      cc->loc.file,cc->loc.line);
 204     }
 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) fatal_perror("udp (%s:%d): setsockopt(,IPV6_V6ONLY,&1,)",
 213                             cc->loc.file,cc->loc.line);
 214     }
 215 #endif
 216
 217     if (uc->authbind) {
 218         pid_t c;
 219         int status;
 220
 221         /* XXX this fork() and waitpid() business needs to be hidden
 222            in some system-specific library functions. */
 223         c=fork();
 224         if (c==-1) {
 225             fatal_perror("udp_phase_hook: fork() for authbind");
 226         }
 227         if (c==0) {
 228             char *argv[5], addrstr[33], portstr[5];
 229             const char *addrfam;
 230             int port;
 231             switch (addr->sa.sa_family) {
 232             case AF_INET:
 233                 sprintf(addrstr,"%08lX",(long)addr->sin.sin_addr.s_addr);
 234                 port=addr->sin.sin_port;
 235                 addrfam=NULL;
 236                 break;
 237 #ifdef CONFIG_IPV6
 238             case AF_INET6: {
 239                 int i;
 240                 for (i=0; i<16; i++)
 241                     sprintf(addrstr+i*2,"%02X",addr->sin6.sin6_addr.s6_addr[i]);
 242                 port=addr->sin6.sin6_port;
 243                 addrfam="6";
 244                 break;
 245             }
 246 #endif /*CONFIG_IPV6*/
 247             default:
 248                 fatal("udp (%s:%d): unsupported address family for authbind",
 249                       cc->loc.file,cc->loc.line);
 250             }
 251             sprintf(portstr,"%04X",port);
 252             argv[0]=uc->authbind;
 253             argv[1]=addrstr;
 254             argv[2]=portstr;
 255             argv[3]=(char*)addrfam;
 256             argv[4]=NULL;
 257             dup2(us->fd,0);
 258             execvp(uc->authbind,argv);
 259             _exit(255);
 260         }
 261         while (waitpid(c,&status,0)==-1) {
 262             if (errno==EINTR) continue;
 263             fatal_perror("udp (%s:%d): authbind",cc->loc.file,cc->loc.line);
 264         }
 265         if (WIFSIGNALED(status)) {
 266             fatal("udp (%s:%d): authbind died on signal %d",cc->loc.file,
 267                   cc->loc.line, WTERMSIG(status));
 268         }
 269         if (WIFEXITED(status) && WEXITSTATUS(status)!=0) {
 270             fatal("udp (%s:%d): authbind died with status %d",cc->loc.file,
 271                   cc->loc.line, WEXITSTATUS(status));
 272         }
 273     } else {
 274         if (bind(us->fd, &addr->sa, iaddr_socklen(addr))!=0) {
 275             fatal_perror("udp (%s:%d): bind",cc->loc.file,cc->loc.line);
 276         }
 277     }
 278 }
 279
 280 static void udp_phase_hook(void *sst, uint32_t new_phase)
 281 {
 282     struct udp *st=sst;
 283     struct udpsocks *socks=&st->socks;
 284     int i;
 285     for (i=0; i<socks->n_socks; i++)
 286         udp_make_socket(st,&socks->socks[i]);
 287
 288     register_for_poll(st,udp_beforepoll,udp_afterpoll,"udp");
 289 }
 290
 291 static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context,
 292                          list_t *args)
 293 {
 294     struct udp *st;
 295     list_t *caddrl;
 296     list_t *l;
 297     uint32_t a;
 298     int i;
 299
 300     COMM_APPLY(st,&st->uc.cc,udp_,"udp",loc);
 301     COMM_APPLY_STANDARD(st,&st->uc.cc,"udp",args);
 302     UDP_APPLY_STANDARD(st,&st->uc,"udp");
 303
 304     struct udpcommon *uc=&st->uc;
 305     struct udpsocks *socks=&st->socks;
 306     struct commcommon *cc=&uc->cc;
 307
 308     union iaddr defaultaddrs[] = {
 309 #ifdef CONFIG_IPV6
 310         { .sin6 = { .sin6_family=AF_INET6,
 311                     .sin6_port=htons(uc->port),
 312                     .sin6_addr=IN6ADDR_ANY_INIT } },
 313 #endif
 314         { .sin = { .sin_family=AF_INET,
 315                    .sin_port=htons(uc->port),
 316                    .sin_addr= { .s_addr=INADDR_ANY } } }
 317     };
 318
 319     caddrl=dict_lookup(d,"address");
 320     socks->n_socks=caddrl ? list_length(caddrl) : (int)ARRAY_SIZE(defaultaddrs);
 321     if (socks->n_socks<=0 || socks->n_socks>UDP_MAX_SOCKETS)
 322         cfgfatal(cc->loc,"udp","`address' must be 1..%d addresses",
 323                  UDP_MAX_SOCKETS);
 324
 325     for (i=0; i<socks->n_socks; i++) {
 326         struct udpsock *us=&socks->socks[i];
 327         FILLZERO(us->addr);
 328         if (!list_length(caddrl)) {
 329             us->addr=defaultaddrs[i];
 330         } else {
 331             text2iaddr(list_elem(caddrl,i),uc->port,
 332                        &us->addr,"udp");
 333         }
 334         us->fd=-1;
 335     }
 336
 337     uc->authbind=dict_read_string(d,"authbind",False,"udp",cc->loc);
 338     l=dict_lookup(d,"proxy");
 339     if (l) {
 340         uc->use_proxy=True;
 341         FILLZERO(uc->proxy);
 342         uc->proxy.sa.sa_family=AF_INET;
 343         item=list_elem(l,0);
 344         if (!item || item->type!=t_string) {
 345             cfgfatal(cc->loc,"udp","proxy must supply ""addr"",port\n");
 346         }
 347         a=string_item_to_ipaddr(item,"proxy");
 348         uc->proxy.sin.sin_addr.s_addr=htonl(a);
 349         item=list_elem(l,1);
 350         if (!item || item->type!=t_number) {
 351             cfgfatal(cc->loc,"udp","proxy must supply ""addr"",port\n");
 352         }
 353         uc->proxy.sin.sin_port=htons(item->data.number);
 354     }
 355
 356     update_max_start_pad(&comm_max_start_pad, uc->use_proxy ? 8 : 0);
 357
 358     add_hook(PHASE_GETRESOURCES,udp_phase_hook,st);
 359
 360     return new_closure(&cc->cl);
 361 }
 362
 363 void udp_module(dict_t *dict)
 364 {
 365     add_closure(dict,"udp",udp_apply);
 366 }