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