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 UDP_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[UDP_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     struct udp *socks=st; /* for now */
  75     static char sbuf[100];
  76     int ix=ca->ix>=0 ? ca->ix : 0;
  77
  78     assert(ix>=0 && ix<socks->n_socks);
  79     snprintf(sbuf, sizeof(sbuf), "udp:%s%s-%s",
  80              iaddr_to_string(&socks->socks[ix].addr),
  81              ca->ix<0 ? "&" : "",
  82              iaddr_to_string(&ca->ia));
  83     return sbuf;
  84 }
  85
  86 static int udp_beforepoll(void *state, struct pollfd *fds, int *nfds_io,
  87                           int *timeout_io)
  88 {
  89     int i;
  90     struct udp *st=state;
  91     struct udp *socks=st; /* for now */
  92     BEFOREPOLL_WANT_FDS(socks->n_socks);
  93     for (i=0; i<socks->n_socks; i++) {
  94         fds[i].fd=socks->socks[i].fd;
  95         fds[i].events=POLLIN;
  96     }
  97     return 0;
  98 }
  99
 100 static void udp_afterpoll(void *state, struct pollfd *fds, int nfds)
 101 {
 102     struct udp *st=state;
 103     struct udp *socks=st; /* for now */
 104     struct udp *cc=st; /* for now */
 105     struct udp *uc=st; /* for now */
 106     union iaddr from;
 107     socklen_t fromlen;
 108     struct comm_notify_entry *n;
 109     bool_t done;
 110     int rv;
 111     int i;
 112
 113     for (i=0; i<st->n_socks; i++) {
 114         if (i>=nfds) continue;
 115         if (!(fds[i].revents & POLLIN)) continue;
 116         assert(fds[i].fd == socks->socks[i].fd);
 117         int fd=socks->socks[i].fd;
 118         do {
 119             fromlen=sizeof(from);
 120             BUF_ASSERT_FREE(cc->rbuf);
 121             BUF_ALLOC(cc->rbuf,"udp_afterpoll");
 122             buffer_init(cc->rbuf,calculate_max_start_pad());
 123             rv=recvfrom(fd, cc->rbuf->start,
 124                         buf_remaining_space(cc->rbuf),
 125                         0, &from.sa, &fromlen);
 126             if (rv>0) {
 127                 cc->rbuf->size=rv;
 128                 if (uc->use_proxy) {
 129                     /* Check that the packet came from our poxy server;
 130                        we shouldn't be contacted directly by anybody else
 131                        (since they can trivially forge source addresses) */
 132                     if (!iaddr_equal(&from,&uc->proxy)) {
 133                         Message(M_INFO,"udp: received packet that's not "
 134                                 "from the proxy\n");
 135                         BUF_FREE(cc->rbuf);
 136                         continue;
 137                     }
 138                     /* proxy protocol supports ipv4 transport only */
 139                     from.sa.sa_family=AF_INET;
 140                     memcpy(&from.sin.sin_addr,buf_unprepend(cc->rbuf,4),4);
 141                     buf_unprepend(cc->rbuf,2);
 142                     memcpy(&from.sin.sin_port,buf_unprepend(cc->rbuf,2),2);
 143                 }
 144                 struct comm_addr ca;
 145                 ca.comm=&cc->ops;
 146                 ca.ia=from;
 147                 ca.ix=i;
 148                 done=False;
 149                 LIST_FOREACH(n, &cc->notify, entry) {
 150                     if (n->fn(n->state, cc->rbuf, &ca)) {
 151                         done=True;
 152                         break;
 153                     }
 154                 }
 155                 if (!done) {
 156                     uint32_t msgtype;
 157                     if (cc->rbuf->size>12 /* prevents traffic amplification */
 158                         && ((msgtype=get_uint32(cc->rbuf->start+8))
 159                             != LABEL_NAK)) {
 160                         uint32_t source,dest;
 161                         /* Manufacture and send NAK packet */
 162                         source=get_uint32(cc->rbuf->start); /* Us */
 163                         dest=get_uint32(cc->rbuf->start+4); /* Them */
 164                         send_nak(&ca,source,dest,msgtype,cc->rbuf,"unwanted");
 165                     }
 166                     BUF_FREE(cc->rbuf);
 167                 }
 168                 BUF_ASSERT_FREE(cc->rbuf);
 169             } else {
 170                 BUF_FREE(cc->rbuf);
 171             }
 172         } while (rv>=0);
 173     }
 174 }
 175
 176 static void request_notify(void *commst, void *nst, comm_notify_fn *fn)
 177 {
 178     struct udp *st=commst;
 179     struct udp *cc=st; /* for now */
 180     struct comm_notify_entry *n;
 181
 182     n=safe_malloc(sizeof(*n),"request_notify");
 183     n->fn=fn;
 184     n->state=nst;
 185     LIST_INSERT_HEAD(&cc->notify, n, entry);
 186 }
 187
 188 static void release_notify(void *commst, void *nst, comm_notify_fn *fn)
 189 {
 190     struct udp *st=commst;
 191     struct udp *cc=st; /* for now */
 192     struct comm_notify_entry *n, *t;
 193
 194     /* XXX untested */
 195     LIST_FOREACH_SAFE(n, &cc->notify, entry, t) {
 196         if (n->state==nst && n->fn==fn) {
 197             LIST_REMOVE(n, entry);
 198             free(n);
 199         }
 200     }
 201 }
 202
 203 static bool_t udp_sendmsg(void *commst, struct buffer_if *buf,
 204                           const struct comm_addr *dest)
 205 {
 206     struct udp *st=commst;
 207     struct udp *uc=st; /* for now */
 208     struct udp *socks=st; /* for now */
 209     uint8_t *sa;
 210
 211     if (uc->use_proxy) {
 212         sa=buf_prepend(buf,8);
 213         if (dest->ia.sa.sa_family != AF_INET) {
 214             Message(M_INFO,
 215                "udp: proxy means dropping outgoing non-IPv4 packet to %s\n",
 216                     iaddr_to_string(&dest->ia));
 217             return False;
 218         }
 219         memcpy(sa,&dest->ia.sin.sin_addr,4);
 220         memset(sa+4,0,4);
 221         memcpy(sa+6,&dest->ia.sin.sin_port,2);
 222         sendto(socks->socks[0].fd,sa,buf->size+8,0,&uc->proxy.sa,
 223                iaddr_socklen(&uc->proxy));
 224         buf_unprepend(buf,8);
 225     } else {
 226         int i,r;
 227         bool_t allunsupported=True;
 228         for (i=0; i<socks->n_socks; i++) {
 229             if (dest->ia.sa.sa_family != socks->socks[i].addr.sa.sa_family)
 230                 /* no point even trying */
 231                 continue;
 232             r=sendto(socks->socks[i].fd, buf->start, buf->size, 0,
 233                      &dest->ia.sa, iaddr_socklen(&dest->ia));
 234             if (r>=0) return True;
 235             if (!(errno==EAFNOSUPPORT || errno==ENETUNREACH))
 236                 /* who knows what that error means? */
 237                 allunsupported=False;
 238         }
 239         return !allunsupported; /* see doc for comm_sendmsg_fn in secnet.h */
 240     }
 241
 242     return True;
 243 }
 244
 245 static void udp_make_socket(struct udp *st, struct udpsock *us)
 246 {
 247     const union iaddr *addr=&us->addr;
 248     struct udp *cc=st; /* for now */
 249     struct udp *uc=st; /* for now */
 250     us->fd=socket(addr->sa.sa_family, SOCK_DGRAM, IPPROTO_UDP);
 251     if (us->fd<0) {
 252         fatal_perror("udp (%s:%d): socket",cc->loc.file,cc->loc.line);
 253     }
 254     if (fcntl(us->fd, F_SETFL, fcntl(us->fd, F_GETFL)|O_NONBLOCK)==-1) {
 255         fatal_perror("udp (%s:%d): fcntl(set O_NONBLOCK)",
 256                      cc->loc.file,cc->loc.line);
 257     }
 258     setcloexec(us->fd);
 259 #ifdef CONFIG_IPV6
 260     if (addr->sa.sa_family==AF_INET6) {
 261         int r;
 262         int optval=1;
 263         socklen_t optlen=sizeof(optval);
 264         r=setsockopt(us->fd,IPPROTO_IPV6,IPV6_V6ONLY,&optval,optlen);
 265         if (r) fatal_perror("udp (%s:%d): setsockopt(,IPV6_V6ONLY,&1,)",
 266                             cc->loc.file,cc->loc.line);
 267     }
 268 #endif
 269
 270     if (uc->authbind) {
 271         pid_t c;
 272         int status;
 273
 274         /* XXX this fork() and waitpid() business needs to be hidden
 275            in some system-specific library functions. */
 276         c=fork();
 277         if (c==-1) {
 278             fatal_perror("udp_phase_hook: fork() for authbind");
 279         }
 280         if (c==0) {
 281             char *argv[5], addrstr[33], portstr[5];
 282             const char *addrfam;
 283             int port;
 284             switch (addr->sa.sa_family) {
 285             case AF_INET:
 286                 sprintf(addrstr,"%08lX",(long)addr->sin.sin_addr.s_addr);
 287                 port=addr->sin.sin_port;
 288                 addrfam=NULL;
 289                 break;
 290 #ifdef CONFIG_IPV6
 291             case AF_INET6: {
 292                 int i;
 293                 for (i=0; i<16; i++)
 294                     sprintf(addrstr+i*2,"%02X",addr->sin6.sin6_addr.s6_addr[i]);
 295                 port=addr->sin6.sin6_port;
 296                 addrfam="6";
 297                 break;
 298             }
 299 #endif /*CONFIG_IPV6*/
 300             default:
 301                 fatal("udp (%s:%d): unsupported address family for authbind",
 302                       cc->loc.file,cc->loc.line);
 303             }
 304             sprintf(portstr,"%04X",port);
 305             argv[0]=uc->authbind;
 306             argv[1]=addrstr;
 307             argv[2]=portstr;
 308             argv[3]=(char*)addrfam;
 309             argv[4]=NULL;
 310             dup2(us->fd,0);
 311             execvp(uc->authbind,argv);
 312             _exit(255);
 313         }
 314         while (waitpid(c,&status,0)==-1) {
 315             if (errno==EINTR) continue;
 316             fatal_perror("udp (%s:%d): authbind",cc->loc.file,cc->loc.line);
 317         }
 318         if (WIFSIGNALED(status)) {
 319             fatal("udp (%s:%d): authbind died on signal %d",cc->loc.file,
 320                   cc->loc.line, WTERMSIG(status));
 321         }
 322         if (WIFEXITED(status) && WEXITSTATUS(status)!=0) {
 323             fatal("udp (%s:%d): authbind died with status %d",cc->loc.file,
 324                   cc->loc.line, WEXITSTATUS(status));
 325         }
 326     } else {
 327         if (bind(us->fd, &addr->sa, iaddr_socklen(addr))!=0) {
 328             fatal_perror("udp (%s:%d): bind",cc->loc.file,cc->loc.line);
 329         }
 330     }
 331 }
 332
 333 static void udp_phase_hook(void *sst, uint32_t new_phase)
 334 {
 335     struct udp *st=sst;
 336     struct udp *socks=st; /* for now */
 337     int i;
 338     for (i=0; i<socks->n_socks; i++)
 339         udp_make_socket(st,&socks->socks[i]);
 340
 341     register_for_poll(st,udp_beforepoll,udp_afterpoll,"udp");
 342 }
 343
 344 static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context,
 345                          list_t *args)
 346 {
 347     struct udp *st;
 348     item_t *item;
 349     list_t *caddrl;
 350     dict_t *d;
 351     list_t *l;
 352     uint32_t a;
 353     int i;
 354
 355     st=safe_malloc(sizeof(*st),"udp_apply(st)");
 356     struct udp *cc=st; /* for now */
 357     struct udp *uc=st; /* for now */
 358     struct udp *socks=st; /* for now */
 359     cc->loc=loc;
 360     cc->cl.description="udp";
 361     cc->cl.type=CL_COMM;
 362     cc->cl.apply=NULL;
 363     cc->cl.interface=&cc->ops;
 364     cc->ops.st=st;
 365     cc->ops.request_notify=request_notify;
 366     cc->ops.release_notify=release_notify;
 367     cc->ops.sendmsg=udp_sendmsg;
 368     cc->ops.addr_to_string=addr_to_string;
 369     uc->use_proxy=False;
 370     LIST_INIT(&cc->notify);
 371
 372     item=list_elem(args,0);
 373     if (!item || item->type!=t_dict) {
 374         cfgfatal(cc->loc,"udp","first argument must be a dictionary\n");
 375     }
 376     d=item->data.dict;
 377
 378     int port=dict_read_number(d,"port",True,"udp",cc->loc,0);
 379
 380     union iaddr defaultaddrs[] = {
 381 #ifdef CONFIG_IPV6
 382         { .sin6 = { .sin6_family=AF_INET6,
 383                     .sin6_port=htons(port),
 384                     .sin6_addr=IN6ADDR_ANY_INIT } },
 385 #endif
 386         { .sin = { .sin_family=AF_INET,
 387                    .sin_port=htons(port),
 388                    .sin_addr= { .s_addr=INADDR_ANY } } }
 389     };
 390
 391     caddrl=dict_lookup(d,"address");
 392     socks->n_socks=caddrl ? list_length(caddrl) : (int)ARRAY_SIZE(defaultaddrs);
 393     if (socks->n_socks<=0 || socks->n_socks>UDP_MAX_SOCKETS)
 394         cfgfatal(cc->loc,"udp","`address' must be 1..%d addresses",
 395                  UDP_MAX_SOCKETS);
 396
 397     for (i=0; i<socks->n_socks; i++) {
 398         struct udpsock *us=&socks->socks[i];
 399         if (!list_length(caddrl)) {
 400             us->addr=defaultaddrs[i];
 401         } else {
 402             string_item_to_iaddr(list_elem(caddrl,i),port,&us->addr,"udp");
 403         }
 404         us->fd=-1;
 405     }
 406
 407     cc->rbuf=find_cl_if(d,"buffer",CL_BUFFER,True,"udp",cc->loc);
 408     uc->authbind=dict_read_string(d,"authbind",False,"udp",cc->loc);
 409     l=dict_lookup(d,"proxy");
 410     if (l) {
 411         uc->use_proxy=True;
 412         uc->proxy.sa.sa_family=AF_INET;
 413         item=list_elem(l,0);
 414         if (!item || item->type!=t_string) {
 415             cfgfatal(cc->loc,"udp","proxy must supply ""addr"",port\n");
 416         }
 417         a=string_item_to_ipaddr(item,"proxy");
 418         uc->proxy.sin.sin_addr.s_addr=htonl(a);
 419         item=list_elem(l,1);
 420         if (!item || item->type!=t_number) {
 421             cfgfatal(cc->loc,"udp","proxy must supply ""addr"",port\n");
 422         }
 423         uc->proxy.sin.sin_port=htons(item->data.number);
 424     }
 425
 426     update_max_start_pad(&comm_max_start_pad, uc->use_proxy ? 8 : 0);
 427
 428     add_hook(PHASE_GETRESOURCES,udp_phase_hook,st);
 429
 430     return new_closure(&cc->cl);
 431 }
 432
 433 void udp_module(dict_t *dict)
 434 {
 435     add_closure(dict,"udp",udp_apply);
 436 }