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