mdw@git.distorted.org.uk Git - secnet/blob - 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 /*
  61  * Re comm_addr.ix: This field allows us to note in the comm_addr
  62  * which socket an incoming packet was received on.  This is required
  63  * for conveniently logging the actual source of a packet.  But the ix
  64  * does not formally form part of the address: it is not used when
  65  * sending, nor when comparing two comm_addrs.
  66  *
  67  * The special value -1 means that the comm_addr was constructed by
  68  * another module in secnet (eg the resolver), rather than being a
  69  * description of the source of an incoming packet.
  70  */
  71
  72 static const char *addr_to_string(void *commst, const struct comm_addr *ca) {
  73     struct udp *st=commst;
  74     static char sbuf[100];
  75     int ix=ca->ix>=0 ? ca->ix : 0;
  76
  77     assert(ix>=0 && ix<st->n_socks);
  78     snprintf(sbuf, sizeof(sbuf), "udp:%s%s-%s",
  79              iaddr_to_string(&st->socks[ix].addr),
  80              ca->ix<0 ? "&" : "",
  81              iaddr_to_string(&ca->ia));
  82     return sbuf;
  83 }
  84
  85 static int udp_beforepoll(void *state, struct pollfd *fds, int *nfds_io,
  86                           int *timeout_io)
  87 {
  88     int i;
  89     struct udp *st=state;
  90     if (*nfds_io<st->n_socks) {
  91         *nfds_io=st->n_socks;
  92         return ERANGE;
  93     }
  94     *nfds_io=st->n_socks;
  95     for (i=0; i<st->n_socks; i++) {
  96         fds[i].fd=st->socks[i].fd;
  97         fds[i].events=POLLIN;
  98     }
  99     return 0;
 100 }
 101
 102 static void udp_afterpoll(void *state, struct pollfd *fds, int nfds)
 103 {
 104     struct udp *st=state;
 105     union iaddr from;
 106     socklen_t fromlen;
 107     struct comm_notify_entry *n;
 108     bool_t done;
 109     int rv;
 110     int i;
 111
 112     for (i=0; i<st->n_socks; i++) {
 113         if (i>=nfds) continue;
 114         if (!(fds[i].revents & POLLIN)) continue;
 115         assert(fds[i].fd == st->socks[i].fd);
 116         int fd=st->socks[i].fd;
 117         do {
 118             fromlen=sizeof(from);
 119             BUF_ASSERT_FREE(st->rbuf);
 120             BUF_ALLOC(st->rbuf,"udp_afterpoll");
 121             buffer_init(st->rbuf,calculate_max_start_pad());
 122             rv=recvfrom(fd, st->rbuf->start,
 123                         buf_remaining_space(st->rbuf),
 124                         0, &from.sa, &fromlen);
 125             if (rv>0) {
 126                 st->rbuf->size=rv;
 127                 if (st->use_proxy) {
 128                     /* Check that the packet came from our poxy server;
 129                        we shouldn't be contacted directly by anybody else
 130                        (since they can trivially forge source addresses) */
 131                     if (!iaddr_equal(&from,&st->proxy)) {
 132                         Message(M_INFO,"udp: received packet that's not "
 133                                 "from the proxy\n");
 134                         BUF_FREE(st->rbuf);
 135                         continue;
 136                     }
 137                     /* proxy protocol supports ipv4 transport only */
 138                     from.sa.sa_family=AF_INET;
 139                     memcpy(&from.sin.sin_addr,buf_unprepend(st->rbuf,4),4);
 140                     buf_unprepend(st->rbuf,2);
 141                     memcpy(&from.sin.sin_port,buf_unprepend(st->rbuf,2),2);
 142                 }
 143                 struct comm_addr ca;
 144                 ca.comm=&st->ops;
 145                 ca.ia=from;
 146                 ca.ix=i;
 147                 done=False;
 148                 LIST_FOREACH(n, &st->notify, entry) {
 149                     if (n->fn(n->state, st->rbuf, &ca)) {
 150                         done=True;
 151                         break;
 152                     }
 153                 }
 154                 if (!done) {
 155                     uint32_t msgtype;
 156                     if (st->rbuf->size>12 /* prevents traffic amplification */
 157                         && ((msgtype=get_uint32(st->rbuf->start+8))
 158                             != LABEL_NAK)) {
 159                         uint32_t source,dest;
 160                         /* Manufacture and send NAK packet */
 161                         source=get_uint32(st->rbuf->start); /* Us */
 162                         dest=get_uint32(st->rbuf->start+4); /* Them */
 163                         send_nak(&ca,source,dest,msgtype,st->rbuf,"unwanted");
 164                     }
 165                     BUF_FREE(st->rbuf);
 166                 }
 167                 BUF_ASSERT_FREE(st->rbuf);
 168             } else {
 169                 BUF_FREE(st->rbuf);
 170             }
 171         } while (rv>=0);
 172     }
 173 }
 174
 175 static void request_notify(void *commst, void *nst, comm_notify_fn *fn)
 176 {
 177     struct udp *st=commst;
 178     struct comm_notify_entry *n;
 179
 180     n=safe_malloc(sizeof(*n),"request_notify");
 181     n->fn=fn;
 182     n->state=nst;
 183     LIST_INSERT_HEAD(&st->notify, n, entry);
 184 }
 185
 186 static void release_notify(void *commst, void *nst, comm_notify_fn *fn)
 187 {
 188     struct udp *st=commst;
 189     struct comm_notify_entry *n, *t;
 190
 191     /* XXX untested */
 192     LIST_FOREACH_SAFE(n, &st->notify, entry, t) {
 193         if (n->state==nst && n->fn==fn) {
 194             LIST_REMOVE(n, entry);
 195             free(n);
 196         }
 197     }
 198 }
 199
 200 static bool_t udp_sendmsg(void *commst, struct buffer_if *buf,
 201                           const struct comm_addr *dest)
 202 {
 203     struct udp *st=commst;
 204     uint8_t *sa;
 205
 206     if (st->use_proxy) {
 207         sa=buf_prepend(buf,8);
 208         if (dest->ia.sa.sa_family != AF_INET) {
 209             Message(M_INFO,
 210                "udp: proxy means dropping outgoing non-IPv4 packet to %s\n",
 211                     iaddr_to_string(&dest->ia));
 212             return False;
 213         }
 214         memcpy(sa,&dest->ia.sin.sin_addr,4);
 215         memset(sa+4,0,4);
 216         memcpy(sa+6,&dest->ia.sin.sin_port,2);
 217         sendto(st->socks[0].fd,sa,buf->size+8,0,&st->proxy.sa,
 218                iaddr_socklen(&st->proxy));
 219         buf_unprepend(buf,8);
 220     } else {
 221         int i,r;
 222         bool_t allunsupported=True;
 223         for (i=0; i<st->n_socks; i++) {
 224             if (dest->ia.sa.sa_family != st->socks[i].addr.sa.sa_family)
 225                 /* no point even trying */
 226                 continue;
 227             r=sendto(st->socks[i].fd, buf->start, buf->size, 0,
 228                      &dest->ia.sa, iaddr_socklen(&dest->ia));
 229             if (r>=0) return True;
 230             if (!(errno==EAFNOSUPPORT || errno==ENETUNREACH))
 231                 /* who knows what that error means? */
 232                 allunsupported=False;
 233         }
 234         return !allunsupported; /* see doc for comm_sendmsg_fn in secnet.h */
 235     }
 236
 237     return True;
 238 }
 239
 240 static void udp_make_socket(struct udp *st, struct udpsock *us)
 241 {
 242     const union iaddr *addr=&us->addr;
 243     us->fd=socket(addr->sa.sa_family, SOCK_DGRAM, IPPROTO_UDP);
 244     if (us->fd<0) {
 245         fatal_perror("udp (%s:%d): socket",st->loc.file,st->loc.line);
 246     }
 247     if (fcntl(us->fd, F_SETFL, fcntl(us->fd, F_GETFL)|O_NONBLOCK)==-1) {
 248         fatal_perror("udp (%s:%d): fcntl(set O_NONBLOCK)",
 249                      st->loc.file,st->loc.line);
 250     }
 251     setcloexec(us->fd);
 252 #ifdef CONFIG_IPV6
 253     if (addr->sa.sa_family==AF_INET6) {
 254         int r;
 255         int optval=1;
 256         socklen_t optlen=sizeof(optval);
 257         r=setsockopt(us->fd,IPPROTO_IPV6,IPV6_V6ONLY,&optval,optlen);
 258         if (r) fatal_perror("udp (%s:%d): setsockopt(,IPV6_V6ONLY,&1,)",
 259                             st->loc.file,st->loc.line);
 260     }
 261 #endif
 262
 263     if (st->authbind) {
 264         pid_t c;
 265         int status;
 266
 267         /* XXX this fork() and waitpid() business needs to be hidden
 268            in some system-specific library functions. */
 269         c=fork();
 270         if (c==-1) {
 271             fatal_perror("udp_phase_hook: fork() for authbind");
 272         }
 273         if (c==0) {
 274             char *argv[5], addrstr[33], portstr[5];
 275             const char *addrfam;
 276             int port;
 277             switch (addr->sa.sa_family) {
 278             case AF_INET:
 279                 sprintf(addrstr,"%08lX",(long)addr->sin.sin_addr.s_addr);
 280                 port=addr->sin.sin_port;
 281                 addrfam=NULL;
 282                 break;
 283 #ifdef CONFIG_IPV6
 284             case AF_INET6: {
 285                 int i;
 286                 for (i=0; i<16; i++)
 287                     sprintf(addrstr+i*2,"%02X",addr->sin6.sin6_addr.s6_addr[i]);
 288                 port=addr->sin6.sin6_port;
 289                 addrfam="6";
 290                 break;
 291             }
 292 #endif /*CONFIG_IPV6*/
 293             default:
 294                 fatal("udp (%s:%d): unsupported address family for authbind",
 295                       st->loc.file,st->loc.line);
 296             }
 297             sprintf(portstr,"%04X",port);
 298             argv[0]=st->authbind;
 299             argv[1]=addrstr;
 300             argv[2]=portstr;
 301             argv[3]=(char*)addrfam;
 302             argv[4]=NULL;
 303             dup2(us->fd,0);
 304             execvp(st->authbind,argv);
 305             _exit(255);
 306         }
 307         while (waitpid(c,&status,0)==-1) {
 308             if (errno==EINTR) continue;
 309             fatal_perror("udp (%s:%d): authbind",st->loc.file,st->loc.line);
 310         }
 311         if (WIFSIGNALED(status)) {
 312             fatal("udp (%s:%d): authbind died on signal %d",st->loc.file,
 313                   st->loc.line, WTERMSIG(status));
 314         }
 315         if (WIFEXITED(status) && WEXITSTATUS(status)!=0) {
 316             fatal("udp (%s:%d): authbind died with status %d",st->loc.file,
 317                   st->loc.line, WEXITSTATUS(status));
 318         }
 319     } else {
 320         if (bind(us->fd, &addr->sa, iaddr_socklen(addr))!=0) {
 321             fatal_perror("udp (%s:%d): bind",st->loc.file,st->loc.line);
 322         }
 323     }
 324 }
 325
 326 static void udp_phase_hook(void *sst, uint32_t new_phase)
 327 {
 328     struct udp *st=sst;
 329     int i;
 330     for (i=0; i<st->n_socks; i++)
 331         udp_make_socket(st,&st->socks[i]);
 332
 333     register_for_poll(st,udp_beforepoll,udp_afterpoll,MAX_SOCKETS,"udp");
 334 }
 335
 336 static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context,
 337                          list_t *args)
 338 {
 339     struct udp *st;
 340     item_t *item;
 341     list_t *caddrl;
 342     dict_t *d;
 343     list_t *l;
 344     uint32_t a;
 345     int i;
 346
 347     st=safe_malloc(sizeof(*st),"udp_apply(st)");
 348     st->loc=loc;
 349     st->cl.description="udp";
 350     st->cl.type=CL_COMM;
 351     st->cl.apply=NULL;
 352     st->cl.interface=&st->ops;
 353     st->ops.st=st;
 354     st->ops.request_notify=request_notify;
 355     st->ops.release_notify=release_notify;
 356     st->ops.sendmsg=udp_sendmsg;
 357     st->ops.addr_to_string=addr_to_string;
 358     st->use_proxy=False;
 359     LIST_INIT(&st->notify);
 360
 361     item=list_elem(args,0);
 362     if (!item || item->type!=t_dict) {
 363         cfgfatal(st->loc,"udp","first argument must be a dictionary\n");
 364     }
 365     d=item->data.dict;
 366
 367     int port=dict_read_number(d,"port",True,"udp",st->loc,0);
 368
 369     union iaddr defaultaddrs[] = {
 370 #ifdef CONFIG_IPV6
 371         { .sin6 = { .sin6_family=AF_INET6,
 372                     .sin6_port=htons(port),
 373                     .sin6_addr=IN6ADDR_ANY_INIT } },
 374 #endif
 375         { .sin = { .sin_family=AF_INET,
 376                    .sin_port=htons(port),
 377                    .sin_addr= { .s_addr=INADDR_ANY } } }
 378     };
 379
 380     caddrl=dict_lookup(d,"address");
 381     st->n_socks=caddrl ? list_length(caddrl) : (int)ARRAY_SIZE(defaultaddrs);
 382     if (st->n_socks<=0 || st->n_socks>MAX_SOCKETS)
 383         cfgfatal(st->loc,"udp","`address' must be 1..%d addresses",
 384                  MAX_SOCKETS);
 385
 386     for (i=0; i<st->n_socks; i++) {
 387         struct udpsock *us=&st->socks[i];
 388         if (!list_length(caddrl)) {
 389             us->addr=defaultaddrs[i];
 390         } else {
 391             string_item_to_iaddr(list_elem(caddrl,i),port,&us->addr,"udp");
 392         }
 393         us->fd=-1;
 394     }
 395
 396     st->rbuf=find_cl_if(d,"buffer",CL_BUFFER,True,"udp",st->loc);
 397     st->authbind=dict_read_string(d,"authbind",False,"udp",st->loc);
 398     l=dict_lookup(d,"proxy");
 399     if (l) {
 400         st->use_proxy=True;
 401         st->proxy.sa.sa_family=AF_INET;
 402         item=list_elem(l,0);
 403         if (!item || item->type!=t_string) {
 404             cfgfatal(st->loc,"udp","proxy must supply ""addr"",port\n");
 405         }
 406         a=string_item_to_ipaddr(item,"proxy");
 407         st->proxy.sin.sin_addr.s_addr=htonl(a);
 408         item=list_elem(l,1);
 409         if (!item || item->type!=t_number) {
 410             cfgfatal(st->loc,"udp","proxy must supply ""addr"",port\n");
 411         }
 412         st->proxy.sin.sin_port=htons(item->data.number);
 413     }
 414
 415     update_max_start_pad(&comm_max_start_pad, st->use_proxy ? 8 : 0);
 416
 417     add_hook(PHASE_GETRESOURCES,udp_phase_hook,st);
 418
 419     return new_closure(&st->cl);
 420 }
 421
 422 void udp_module(dict_t *dict)
 423 {
 424     add_closure(dict,"udp",udp_apply);
 425 }