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