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 notify_list {
  34     comm_notify_fn *fn;
  35     void *state;
  36     struct notify_list *next;
  37 };
  38
  39 #define MAX_SOCKETS 3 /* 2 ought to do really */
  40
  41 struct udpsock {
  42     union iaddr addr;
  43     int fd;
  44 };
  45
  46 struct udp {
  47     closure_t cl;
  48     struct comm_if ops;
  49     struct cloc loc;
  50     int n_socks;
  51     struct udpsock socks[MAX_SOCKETS];
  52     string_t authbind;
  53     struct buffer_if *rbuf;
  54     struct notify_list *notify;
  55     bool_t use_proxy;
  56     union iaddr proxy;
  57 };
  58
  59 /*
  60  * Re comm_addr.ix: This field allows us to note in the comm_addr
  61  * which socket an incoming packet was received on.  This is required
  62  * for conveniently logging the actual source of a packet.  But the ix
  63  * does not formally form part of the address: it is not used when
  64  * sending, nor when comparing two comm_addrs.
  65  *
  66  * The special value -1 means that the comm_addr was constructed by
  67  * another module in secnet (eg the resolver), rather than being a
  68  * description of the source of an incoming packet.
  69  */
  70
  71 static const char *addr_to_string(void *commst, const struct comm_addr *ca) {
  72     struct udp *st=commst;
  73     static char sbuf[100];
  74     int ix=ca->ix>=0 ? ca->ix : 0;
  75
  76     assert(ix>=0 && ix<st->n_socks);
  77     snprintf(sbuf, sizeof(sbuf), "udp:%s%s-%s",
  78              iaddr_to_string(&st->socks[ix].addr),
  79              ca->ix<0 ? "&" : "",
  80              iaddr_to_string(&ca->ia));
  81     return sbuf;
  82 }
  83
  84 static int udp_beforepoll(void *state, struct pollfd *fds, int *nfds_io,
  85                           int *timeout_io)
  86 {
  87     int i;
  88     struct udp *st=state;
  89     if (*nfds_io<st->n_socks) {
  90         *nfds_io=st->n_socks;
  91         return ERANGE;
  92     }
  93     *nfds_io=st->n_socks;
  94     for (i=0; i<st->n_socks; i++) {
  95         fds[i].fd=st->socks[i].fd;
  96         fds[i].events=POLLIN;
  97     }
  98     return 0;
  99 }
 100
 101 static void udp_afterpoll(void *state, struct pollfd *fds, int nfds)
 102 {
 103     struct udp *st=state;
 104     union iaddr from;
 105     socklen_t fromlen;
 106     struct notify_list *n;
 107     bool_t done;
 108     int rv;
 109     int i;
 110
 111     for (i=0; i<st->n_socks; i++) {
 112         if (i>=nfds) continue;
 113         if (!(fds[i].revents & POLLIN)) continue;
 114         assert(fds[i].fd == st->socks[i].fd);
 115         int fd=st->socks[i].fd;
 116         do {
 117             fromlen=sizeof(from);
 118             BUF_ASSERT_FREE(st->rbuf);
 119             BUF_ALLOC(st->rbuf,"udp_afterpoll");
 120             buffer_init(st->rbuf,calculate_max_start_pad());
 121             rv=recvfrom(fd, st->rbuf->start,
 122                         buf_remaining_space(st->rbuf),
 123                         0, &from.sa, &fromlen);
 124             if (rv>0) {
 125                 st->rbuf->size=rv;
 126                 if (st->use_proxy) {
 127                     /* Check that the packet came from our poxy server;
 128                        we shouldn't be contacted directly by anybody else
 129                        (since they can trivially forge source addresses) */
 130                     if (!iaddr_equal(&from,&st->proxy)) {
 131                         Message(M_INFO,"udp: received packet that's not "
 132                                 "from the proxy\n");
 133                         BUF_FREE(st->rbuf);
 134                         continue;
 135                     }
 136                     /* proxy protocol supports ipv4 transport only */
 137                     from.sa.sa_family=AF_INET;
 138                     memcpy(&from.sin.sin_addr,buf_unprepend(st->rbuf,4),4);
 139                     buf_unprepend(st->rbuf,2);
 140                     memcpy(&from.sin.sin_port,buf_unprepend(st->rbuf,2),2);
 141                 }
 142                 struct comm_addr ca;
 143                 ca.comm=&st->ops;
 144                 ca.ia=from;
 145                 ca.ix=i;
 146                 done=False;
 147                 for (n=st->notify; n; n=n->next) {
 148                     if (n->fn(n->state, st->rbuf, &ca)) {
 149                         done=True;
 150                         break;
 151                     }
 152                 }
 153                 if (!done) {
 154                     uint32_t msgtype;
 155                     if (st->rbuf->size>12 /* prevents traffic amplification */
 156                         && ((msgtype=get_uint32(st->rbuf->start+8))
 157                             != LABEL_NAK)) {
 158                         uint32_t source,dest;
 159                         /* Manufacture and send NAK packet */
 160                         source=get_uint32(st->rbuf->start); /* Us */
 161                         dest=get_uint32(st->rbuf->start+4); /* Them */
 162                         send_nak(&ca,source,dest,msgtype,st->rbuf,"unwanted");
 163                     }
 164                     BUF_FREE(st->rbuf);
 165                 }
 166                 BUF_ASSERT_FREE(st->rbuf);
 167             } else {
 168                 BUF_FREE(st->rbuf);
 169             }
 170         } while (rv>=0);
 171     }
 172 }
 173
 174 static void request_notify(void *commst, void *nst, comm_notify_fn *fn)
 175 {
 176     struct udp *st=commst;
 177     struct notify_list *n;
 178
 179     n=safe_malloc(sizeof(*n),"request_notify");
 180     n->fn=fn;
 181     n->state=nst;
 182     n->next=st->notify;
 183     st->notify=n;
 184 }
 185
 186 static void release_notify(void *commst, void *nst, comm_notify_fn *fn)
 187 {
 188     struct udp *st=commst;
 189     struct notify_list *n, **p, *t;
 190
 191     /* XXX untested */
 192     p=&st->notify;
 193     for (n=st->notify; n; )
 194     {
 195         if (n->state==nst && n->fn==fn) {
 196             t=n;
 197             *p=n->next;
 198             n=n->next;
 199             free(t);
 200         } else {
 201             p=&n->next;
 202             n=n->next;
 203         }
 204     }
 205 }
 206
 207 static bool_t udp_sendmsg(void *commst, struct buffer_if *buf,
 208                           const struct comm_addr *dest)
 209 {
 210     struct udp *st=commst;
 211     uint8_t *sa;
 212
 213     if (st->use_proxy) {
 214         sa=buf_prepend(buf,8);
 215         if (dest->ia.sa.sa_family != AF_INET) {
 216             Message(M_INFO,
 217                "udp: proxy means dropping outgoing non-IPv4 packet to %s\n",
 218                     iaddr_to_string(&dest->ia));
 219             return False;
 220         }
 221         memcpy(sa,&dest->ia.sin.sin_addr,4);
 222         memset(sa+4,0,4);
 223         memcpy(sa+6,&dest->ia.sin.sin_port,2);
 224         sendto(st->socks[0].fd,sa,buf->size+8,0,&st->proxy.sa,
 225                iaddr_socklen(&st->proxy));
 226         buf_unprepend(buf,8);
 227     } else {
 228         int i,r;
 229         bool_t allunsupported=True;
 230         for (i=0; i<st->n_socks; i++) {
 231             if (dest->ia.sa.sa_family != st->socks[i].addr.sa.sa_family)
 232                 /* no point even trying */
 233                 continue;
 234             r=sendto(st->socks[i].fd, buf->start, buf->size, 0,
 235                      &dest->ia.sa, iaddr_socklen(&dest->ia));
 236             if (r>=0) return True;
 237             if (!(errno==EAFNOSUPPORT || errno==ENETUNREACH))
 238                 /* who knows what that error means? */
 239                 allunsupported=False;
 240         }
 241         return !allunsupported; /* see doc for comm_sendmsg_fn in secnet.h */
 242     }
 243
 244     return True;
 245 }
 246
 247 static void udp_make_socket(struct udp *st, struct udpsock *us)
 248 {
 249     const union iaddr *addr=&us->addr;
 250     us->fd=socket(addr->sa.sa_family, SOCK_DGRAM, IPPROTO_UDP);
 251     if (us->fd<0) {
 252         fatal_perror("udp (%s:%d): socket",st->loc.file,st->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                      st->loc.file,st->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                             st->loc.file,st->loc.line);
 267     }
 268 #endif
 269
 270     if (st->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[4], addrstr[9], portstr[5];
 282             switch (addr->sa.sa_family) {
 283             case AF_INET:
 284                 sprintf(addrstr,"%08lX",(long)addr->sin.sin_addr.s_addr);
 285                 sprintf(portstr,"%04X",addr->sin.sin_port);
 286                 break;
 287             default:
 288                 fatal("udp (%s:%d): unsupported address family for authbind",
 289                       st->loc.file,st->loc.line);
 290             }
 291             argv[0]=st->authbind;
 292             argv[1]=addrstr;
 293             argv[2]=portstr;
 294             argv[3]=NULL;
 295             dup2(us->fd,0);
 296             execvp(st->authbind,argv);
 297             _exit(255);
 298         }
 299         while (waitpid(c,&status,0)==-1) {
 300             if (errno==EINTR) continue;
 301             fatal_perror("udp (%s:%d): authbind",st->loc.file,st->loc.line);
 302         }
 303         if (WIFSIGNALED(status)) {
 304             fatal("udp (%s:%d): authbind died on signal %d",st->loc.file,
 305                   st->loc.line, WTERMSIG(status));
 306         }
 307         if (WIFEXITED(status) && WEXITSTATUS(status)!=0) {
 308             fatal("udp (%s:%d): authbind died with status %d",st->loc.file,
 309                   st->loc.line, WEXITSTATUS(status));
 310         }
 311     } else {
 312         if (bind(us->fd, &addr->sa, iaddr_socklen(addr))!=0) {
 313             fatal_perror("udp (%s:%d): bind",st->loc.file,st->loc.line);
 314         }
 315     }
 316 }
 317
 318 static void udp_phase_hook(void *sst, uint32_t new_phase)
 319 {
 320     struct udp *st=sst;
 321     int i;
 322     for (i=0; i<st->n_socks; i++)
 323         udp_make_socket(st,&st->socks[i]);
 324
 325     register_for_poll(st,udp_beforepoll,udp_afterpoll,MAX_SOCKETS,"udp");
 326 }
 327
 328 static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context,
 329                          list_t *args)
 330 {
 331     struct udp *st;
 332     item_t *item;
 333     list_t *caddrl;
 334     dict_t *d;
 335     list_t *l;
 336     uint32_t a;
 337     int i;
 338
 339     st=safe_malloc(sizeof(*st),"udp_apply(st)");
 340     st->loc=loc;
 341     st->cl.description="udp";
 342     st->cl.type=CL_COMM;
 343     st->cl.apply=NULL;
 344     st->cl.interface=&st->ops;
 345     st->ops.st=st;
 346     st->ops.request_notify=request_notify;
 347     st->ops.release_notify=release_notify;
 348     st->ops.sendmsg=udp_sendmsg;
 349     st->ops.addr_to_string=addr_to_string;
 350     st->use_proxy=False;
 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         if (!list_length(caddrl)) {
 380             us->addr=defaultaddrs[i];
 381         } else {
 382             string_item_to_iaddr(list_elem(caddrl,i),port,&us->addr,"udp");
 383         }
 384         us->fd=-1;
 385     }
 386
 387     st->rbuf=find_cl_if(d,"buffer",CL_BUFFER,True,"udp",st->loc);
 388     st->authbind=dict_read_string(d,"authbind",False,"udp",st->loc);
 389     l=dict_lookup(d,"proxy");
 390     if (l) {
 391         st->use_proxy=True;
 392         st->proxy.sa.sa_family=AF_INET;
 393         item=list_elem(l,0);
 394         if (!item || item->type!=t_string) {
 395             cfgfatal(st->loc,"udp","proxy must supply ""addr"",port\n");
 396         }
 397         a=string_item_to_ipaddr(item,"proxy");
 398         st->proxy.sin.sin_addr.s_addr=htonl(a);
 399         item=list_elem(l,1);
 400         if (!item || item->type!=t_number) {
 401             cfgfatal(st->loc,"udp","proxy must supply ""addr"",port\n");
 402         }
 403         st->proxy.sin.sin_port=htons(item->data.number);
 404     }
 405
 406     update_max_start_pad(&comm_max_start_pad, st->use_proxy ? 8 : 0);
 407
 408     add_hook(PHASE_GETRESOURCES,udp_phase_hook,st);
 409
 410     return new_closure(&st->cl);
 411 }
 412
 413 void udp_module(dict_t *dict)
 414 {
 415     add_closure(dict,"udp",udp_apply);
 416 }