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
  27 static beforepoll_fn udp_beforepoll;
  28 static afterpoll_fn udp_afterpoll;
  29 static comm_request_notify_fn request_notify;
  30 static comm_release_notify_fn release_notify;
  31 static comm_sendmsg_fn udp_sendmsg;
  32
  33 struct comm_notify_entry {
  34     comm_notify_fn *fn;
  35     void *state;
  36     LIST_ENTRY(comm_notify_entry) entry;
  37 };
  38 LIST_HEAD(comm_notify_list, comm_notify_entry) notify;
  39
  40 #define MAX_SOCKETS 3 /* 2 ought to do really */
  41
  42 struct udpsock {
  43     union iaddr addr;
  44     int fd;
  45 };
  46
  47 struct udp {
  48     closure_t cl;
  49     struct comm_if ops;
  50     struct cloc loc;
  51     int n_socks;
  52     struct udpsock socks[MAX_SOCKETS];
  53     string_t authbind;
  54     struct buffer_if *rbuf;
  55     struct comm_notify_list notify;
  56     bool_t use_proxy;
  57     union iaddr proxy;
  58 };
  59
  60 static const char *addr_to_string(void *commst, const struct comm_addr *ca) {
  61     struct udp *st=commst;
  62     static char sbuf[100];
  63     int ix=ca->ix>=0 ? ca->ix : 0;
  64
  65     assert(ix>=0 && ix<st->n_socks);
  66     snprintf(sbuf, sizeof(sbuf), "udp:%d:%s-%s",
  67              ca->ix,
  68              iaddr_to_string(&st->socks[ix].addr),
  69              iaddr_to_string(&ca->ia));
  70     return sbuf;
  71 }
  72
  73 static int udp_beforepoll(void *state, struct pollfd *fds, int *nfds_io,
  74                           int *timeout_io)
  75 {
  76     int i;
  77     struct udp *st=state;
  78     if (*nfds_io<st->n_socks) {
  79         *nfds_io=st->n_socks;
  80         return ERANGE;
  81     }
  82     *nfds_io=st->n_socks;
  83     for (i=0; i<st->n_socks; i++) {
  84         fds[i].fd=st->socks[i].fd;
  85         fds[i].events=POLLIN;
  86     }
  87     return 0;
  88 }
  89
  90 static void udp_afterpoll(void *state, struct pollfd *fds, int nfds)
  91 {
  92     struct udp *st=state;
  93     union iaddr from;
  94     socklen_t fromlen;
  95     struct comm_notify_entry *n;
  96     bool_t done;
  97     int rv;
  98     int i;
  99
 100     for (i=0; i<st->n_socks; i++) {
 101         if (i>=nfds) continue;
 102         if (!(fds[i].revents & POLLIN)) continue;
 103         assert(fds[i].fd == st->socks[i].fd);
 104         int fd=st->socks[i].fd;
 105         do {
 106             FILLZERO(from);
 107             fromlen=sizeof(from);
 108             BUF_ASSERT_FREE(st->rbuf);
 109             BUF_ALLOC(st->rbuf,"udp_afterpoll");
 110             buffer_init(st->rbuf,calculate_max_start_pad());
 111             rv=recvfrom(fd, st->rbuf->start,
 112                         buf_remaining_space(st->rbuf),
 113                         0, (struct sockaddr *)&from, &fromlen);
 114             if (rv>0) {
 115                 st->rbuf->size=rv;
 116                 if (st->use_proxy) {
 117                     /* Check that the packet came from our poxy server;
 118                        we shouldn't be contacted directly by anybody else
 119                        (since they can trivially forge source addresses) */
 120                     if (!iaddr_equal(&from,&st->proxy)) {
 121                         Message(M_INFO,"udp: received packet that's not "
 122                                 "from the proxy\n");
 123                         BUF_FREE(st->rbuf);
 124                         continue;
 125                     }
 126                     /* proxy protocol supports ipv4 transport only */
 127                     FILLZERO(from);
 128                     from.sa.sa_family=AF_INET;
 129                     memcpy(&from.sin.sin_addr,buf_unprepend(st->rbuf,4),4);
 130                     buf_unprepend(st->rbuf,2);
 131                     memcpy(&from.sin.sin_port,buf_unprepend(st->rbuf,2),2);
 132                 }
 133                 struct comm_addr ca;
 134                 FILLZERO(ca);
 135                 ca.comm=&st->ops;
 136                 ca.ia=from;
 137                 ca.ix=i;
 138                 done=False;
 139                 LIST_FOREACH(n, &st->notify, entry) {
 140                     if (n->fn(n->state, st->rbuf, &ca)) {
 141                         done=True;
 142                         break;
 143                     }
 144                 }
 145                 if (!done) {
 146                     uint32_t msgtype;
 147                     if (st->rbuf->size>12 /* prevents traffic amplification */
 148                         && ((msgtype=get_uint32(st->rbuf->start+8))
 149                             != LABEL_NAK)) {
 150                         uint32_t source,dest;
 151                         /* Manufacture and send NAK packet */
 152                         source=get_uint32(st->rbuf->start); /* Us */
 153                         dest=get_uint32(st->rbuf->start+4); /* Them */
 154                         send_nak(&ca,source,dest,msgtype,st->rbuf,"unwanted");
 155                     }
 156                     BUF_FREE(st->rbuf);
 157                 }
 158                 BUF_ASSERT_FREE(st->rbuf);
 159             } else {
 160                 BUF_FREE(st->rbuf);
 161             }
 162         } while (rv>=0);
 163     }
 164 }
 165
 166 static void request_notify(void *commst, void *nst, comm_notify_fn *fn)
 167 {
 168     struct udp *st=commst;
 169     struct comm_notify_entry *n;
 170
 171     n=safe_malloc(sizeof(*n),"request_notify");
 172     n->fn=fn;
 173     n->state=nst;
 174     LIST_INSERT_HEAD(&st->notify, n, entry);
 175 }
 176
 177 static void release_notify(void *commst, void *nst, comm_notify_fn *fn)
 178 {
 179     struct udp *st=commst;
 180     struct comm_notify_entry *n, *t;
 181
 182     /* XXX untested */
 183     LIST_FOREACH_SAFE(n, &st->notify, entry, t) {
 184         if (n->state==nst && n->fn==fn) {
 185             LIST_REMOVE(n, entry);
 186             free(n);
 187         }
 188     }
 189 }
 190
 191 static bool_t udp_sendmsg(void *commst, struct buffer_if *buf,
 192                           const struct comm_addr *dest)
 193 {
 194     struct udp *st=commst;
 195     uint8_t *sa;
 196
 197     if (st->use_proxy) {
 198         sa=buf_prepend(buf,8);
 199         if (dest->ia.sa.sa_family != AF_INET) {
 200             Message(M_INFO,
 201                "udp: proxy means dropping outgoing non-IPv4 packet to %s\n",
 202                     iaddr_to_string(&dest->ia));
 203             return False;
 204         }
 205         memcpy(sa,&dest->ia.sin.sin_addr,4);
 206         memset(sa+4,0,4);
 207         memcpy(sa+6,&dest->ia.sin.sin_port,2);
 208         sendto(st->socks[0].fd,sa,buf->size+8,0,(struct sockaddr *)&st->proxy,
 209                sizeof(st->proxy));
 210         buf_unprepend(buf,8);
 211     } else {
 212         int i,r;
 213         bool_t allunsupported=True;
 214         for (i=0; i<st->n_socks; i++) {
 215             if (dest->ia.sa.sa_family != st->socks[i].addr.sa.sa_family)
 216                 /* no point even trying */
 217                 continue;
 218             r=sendto(st->socks[i].fd, buf->start, buf->size, 0,
 219                      &dest->ia.sa, iaddr_socklen(&dest->ia));
 220             if (!r) return True;
 221             if (!(errno==EAFNOSUPPORT || errno==ENETUNREACH))
 222                 /* who knows what that error means? */
 223                 allunsupported=False;
 224         }
 225         return !allunsupported; /* see doc for comm_sendmsg_fn in secnet.h */
 226     }
 227
 228     return True;
 229 }
 230
 231 static void udp_make_socket(struct udp *st, struct udpsock *us)
 232 {
 233     const union iaddr *addr=&us->addr;
 234     us->fd=socket(addr->sa.sa_family, SOCK_DGRAM, IPPROTO_UDP);
 235     if (us->fd<0) {
 236         fatal_perror("udp (%s:%d): socket",st->loc.file,st->loc.line);
 237     }
 238     if (fcntl(us->fd, F_SETFL, fcntl(us->fd, F_GETFL)|O_NONBLOCK)==-1) {
 239         fatal_perror("udp (%s:%d): fcntl(set O_NONBLOCK)",
 240                      st->loc.file,st->loc.line);
 241     }
 242     setcloexec(us->fd);
 243 #ifdef CONFIG_IPV6
 244     if (addr->sa.sa_family==AF_INET6) {
 245         int r;
 246         int optval=1;
 247         socklen_t optlen=sizeof(optval);
 248         r=setsockopt(us->fd,IPPROTO_IPV6,IPV6_V6ONLY,&optval,optlen);
 249         if (r) fatal_perror("udp (%s:%d): setsockopt(,IPV6_V6ONLY,&1,)",
 250                             st->loc.file,st->loc.line);
 251     }
 252 #endif
 253
 254     if (st->authbind) {
 255         pid_t c;
 256         int status;
 257
 258         /* XXX this fork() and waitpid() business needs to be hidden
 259            in some system-specific library functions. */
 260         c=fork();
 261         if (c==-1) {
 262             fatal_perror("udp_phase_hook: fork() for authbind");
 263         }
 264         if (c==0) {
 265             char *argv[5], addrstr[33], portstr[5];
 266             const char *addrfam;
 267             int port;
 268             switch (addr->sa.sa_family) {
 269             case AF_INET:
 270                 sprintf(addrstr,"%08lX",(long)addr->sin.sin_addr.s_addr);
 271                 port=addr->sin.sin_port;
 272                 addrfam=NULL;
 273                 break;
 274 #ifdef CONFIG_IPV6
 275             case AF_INET6: {
 276                 int i;
 277                 for (i=0; i<16; i++)
 278                     sprintf(addrstr+i*2,"%02X",addr->sin6.sin6_addr.s6_addr[i]);
 279                 port=addr->sin6.sin6_port;
 280                 addrfam="6";
 281                 break;
 282             }
 283 #endif /*CONFIG_IPV6*/
 284             default:
 285                 fatal("udp (%s:%d): unsupported address family for authbind",
 286                       st->loc.file,st->loc.line);
 287             }
 288             sprintf(portstr,"%04X",port);
 289             argv[0]=st->authbind;
 290             argv[1]=addrstr;
 291             argv[2]=portstr;
 292             argv[3]=(char*)addrfam;
 293             argv[4]=NULL;
 294             dup2(us->fd,0);
 295             execvp(st->authbind,argv);
 296             _exit(255);
 297         }
 298         while (waitpid(c,&status,0)==-1) {
 299             if (errno==EINTR) continue;
 300             fatal_perror("udp (%s:%d): authbind",st->loc.file,st->loc.line);
 301         }
 302         if (WIFSIGNALED(status)) {
 303             fatal("udp (%s:%d): authbind died on signal %d",st->loc.file,
 304                   st->loc.line, WTERMSIG(status));
 305         }
 306         if (WIFEXITED(status) && WEXITSTATUS(status)!=0) {
 307             fatal("udp (%s:%d): authbind died with status %d",st->loc.file,
 308                   st->loc.line, WEXITSTATUS(status));
 309         }
 310     } else {
 311         if (bind(us->fd, &addr->sa, iaddr_socklen(addr))!=0) {
 312             fatal_perror("udp (%s:%d): bind",st->loc.file,st->loc.line);
 313         }
 314     }
 315 }
 316
 317 static void udp_phase_hook(void *sst, uint32_t new_phase)
 318 {
 319     struct udp *st=sst;
 320     int i;
 321     for (i=0; i<st->n_socks; i++)
 322         udp_make_socket(st,&st->socks[i]);
 323
 324     register_for_poll(st,udp_beforepoll,udp_afterpoll,MAX_SOCKETS,"udp");
 325 }
 326
 327 static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context,
 328                          list_t *args)
 329 {
 330     struct udp *st;
 331     item_t *item;
 332     list_t *caddrl;
 333     dict_t *d;
 334     list_t *l;
 335     uint32_t a;
 336     int i;
 337
 338     st=safe_malloc(sizeof(*st),"udp_apply(st)");
 339     st->loc=loc;
 340     st->cl.description="udp";
 341     st->cl.type=CL_COMM;
 342     st->cl.apply=NULL;
 343     st->cl.interface=&st->ops;
 344     st->ops.st=st;
 345     st->ops.request_notify=request_notify;
 346     st->ops.release_notify=release_notify;
 347     st->ops.sendmsg=udp_sendmsg;
 348     st->ops.addr_to_string=addr_to_string;
 349     st->use_proxy=False;
 350     LIST_INIT(&st->notify);
 351
 352     item=list_elem(args,0);
 353     if (!item || item->type!=t_dict) {
 354         cfgfatal(st->loc,"udp","first argument must be a dictionary\n");
 355     }
 356     d=item->data.dict;
 357
 358     int port=dict_read_number(d,"port",True,"udp",st->loc,0);
 359
 360     union iaddr defaultaddrs[] = {
 361 #ifdef CONFIG_IPV6
 362         { .sin6 = { .sin6_family=AF_INET6,
 363                     .sin6_port=htons(port),
 364                     .sin6_addr=IN6ADDR_ANY_INIT } },
 365 #endif
 366         { .sin = { .sin_family=AF_INET,
 367                    .sin_port=htons(port),
 368                    .sin_addr= { .s_addr=INADDR_ANY } } }
 369     };
 370
 371     caddrl=dict_lookup(d,"address");
 372     st->n_socks=caddrl ? list_length(caddrl) : (int)ARRAY_SIZE(defaultaddrs);
 373     if (st->n_socks<=0 || st->n_socks>MAX_SOCKETS)
 374         cfgfatal(st->loc,"udp","`address' must be 1..%d addresses",
 375                  MAX_SOCKETS);
 376
 377     for (i=0; i<st->n_socks; i++) {
 378         struct udpsock *us=&st->socks[i];
 379         FILLZERO(us->addr);
 380         if (!list_length(caddrl)) {
 381             us->addr=defaultaddrs[i];
 382         } else {
 383             text2iaddr(list_elem(caddrl,i),port,
 384                        &us->addr,"udp");
 385         }
 386         us->fd=-1;
 387     }
 388
 389     st->rbuf=find_cl_if(d,"buffer",CL_BUFFER,True,"udp",st->loc);
 390     st->authbind=dict_read_string(d,"authbind",False,"udp",st->loc);
 391     l=dict_lookup(d,"proxy");
 392     if (l) {
 393         st->use_proxy=True;
 394         FILLZERO(st->proxy);
 395         st->proxy.sa.sa_family=AF_INET;
 396         item=list_elem(l,0);
 397         if (!item || item->type!=t_string) {
 398             cfgfatal(st->loc,"udp","proxy must supply ""addr"",port\n");
 399         }
 400         a=string_item_to_ipaddr(item,"proxy");
 401         st->proxy.sin.sin_addr.s_addr=htonl(a);
 402         item=list_elem(l,1);
 403         if (!item || item->type!=t_number) {
 404             cfgfatal(st->loc,"udp","proxy must supply ""addr"",port\n");
 405         }
 406         st->proxy.sin.sin_port=htons(item->data.number);
 407     }
 408
 409     update_max_start_pad(&comm_max_start_pad, st->use_proxy ? 8 : 0);
 410
 411     add_hook(PHASE_GETRESOURCES,udp_phase_hook,st);
 412
 413     return new_closure(&st->cl);
 414 }
 415
 416 void udp_module(dict_t *dict)
 417 {
 418     add_closure(dict,"udp",udp_apply);
 419 }