| 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[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 | st->loc.file,st->loc.line); |
| 303 | } |
| 304 | sprintf(portstr,"%04X",port); |
| 305 | argv[0]=st->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(st->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",st->loc.file,st->loc.line); |
| 317 | } |
| 318 | if (WIFSIGNALED(status)) { |
| 319 | fatal("udp (%s:%d): authbind died on signal %d",st->loc.file, |
| 320 | st->loc.line, WTERMSIG(status)); |
| 321 | } |
| 322 | if (WIFEXITED(status) && WEXITSTATUS(status)!=0) { |
| 323 | fatal("udp (%s:%d): authbind died with status %d",st->loc.file, |
| 324 | st->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",st->loc.file,st->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 | int i; |
| 337 | for (i=0; i<st->n_socks; i++) |
| 338 | udp_make_socket(st,&st->socks[i]); |
| 339 | |
| 340 | register_for_poll(st,udp_beforepoll,udp_afterpoll,MAX_SOCKETS,"udp"); |
| 341 | } |
| 342 | |
| 343 | static list_t *udp_apply(closure_t *self, struct cloc loc, dict_t *context, |
| 344 | list_t *args) |
| 345 | { |
| 346 | struct udp *st; |
| 347 | item_t *item; |
| 348 | list_t *caddrl; |
| 349 | dict_t *d; |
| 350 | list_t *l; |
| 351 | uint32_t a; |
| 352 | int i; |
| 353 | |
| 354 | st=safe_malloc(sizeof(*st),"udp_apply(st)"); |
| 355 | st->loc=loc; |
| 356 | st->cl.description="udp"; |
| 357 | st->cl.type=CL_COMM; |
| 358 | st->cl.apply=NULL; |
| 359 | st->cl.interface=&st->ops; |
| 360 | st->ops.st=st; |
| 361 | st->ops.request_notify=request_notify; |
| 362 | st->ops.release_notify=release_notify; |
| 363 | st->ops.sendmsg=udp_sendmsg; |
| 364 | st->ops.addr_to_string=addr_to_string; |
| 365 | st->use_proxy=False; |
| 366 | |
| 367 | item=list_elem(args,0); |
| 368 | if (!item || item->type!=t_dict) { |
| 369 | cfgfatal(st->loc,"udp","first argument must be a dictionary\n"); |
| 370 | } |
| 371 | d=item->data.dict; |
| 372 | |
| 373 | int port=dict_read_number(d,"port",True,"udp",st->loc,0); |
| 374 | |
| 375 | union iaddr defaultaddrs[] = { |
| 376 | #ifdef CONFIG_IPV6 |
| 377 | { .sin6 = { .sin6_family=AF_INET6, |
| 378 | .sin6_port=htons(port), |
| 379 | .sin6_addr=IN6ADDR_ANY_INIT } }, |
| 380 | #endif |
| 381 | { .sin = { .sin_family=AF_INET, |
| 382 | .sin_port=htons(port), |
| 383 | .sin_addr= { .s_addr=INADDR_ANY } } } |
| 384 | }; |
| 385 | |
| 386 | caddrl=dict_lookup(d,"address"); |
| 387 | st->n_socks=caddrl ? list_length(caddrl) : (int)ARRAY_SIZE(defaultaddrs); |
| 388 | if (st->n_socks<=0 || st->n_socks>MAX_SOCKETS) |
| 389 | cfgfatal(st->loc,"udp","`address' must be 1..%d addresses", |
| 390 | MAX_SOCKETS); |
| 391 | |
| 392 | for (i=0; i<st->n_socks; i++) { |
| 393 | struct udpsock *us=&st->socks[i]; |
| 394 | if (!list_length(caddrl)) { |
| 395 | us->addr=defaultaddrs[i]; |
| 396 | } else { |
| 397 | string_item_to_iaddr(list_elem(caddrl,i),port,&us->addr,"udp"); |
| 398 | } |
| 399 | us->fd=-1; |
| 400 | } |
| 401 | |
| 402 | st->rbuf=find_cl_if(d,"buffer",CL_BUFFER,True,"udp",st->loc); |
| 403 | st->authbind=dict_read_string(d,"authbind",False,"udp",st->loc); |
| 404 | l=dict_lookup(d,"proxy"); |
| 405 | if (l) { |
| 406 | st->use_proxy=True; |
| 407 | st->proxy.sa.sa_family=AF_INET; |
| 408 | item=list_elem(l,0); |
| 409 | if (!item || item->type!=t_string) { |
| 410 | cfgfatal(st->loc,"udp","proxy must supply ""addr"",port\n"); |
| 411 | } |
| 412 | a=string_item_to_ipaddr(item,"proxy"); |
| 413 | st->proxy.sin.sin_addr.s_addr=htonl(a); |
| 414 | item=list_elem(l,1); |
| 415 | if (!item || item->type!=t_number) { |
| 416 | cfgfatal(st->loc,"udp","proxy must supply ""addr"",port\n"); |
| 417 | } |
| 418 | st->proxy.sin.sin_port=htons(item->data.number); |
| 419 | } |
| 420 | |
| 421 | update_max_start_pad(&comm_max_start_pad, st->use_proxy ? 8 : 0); |
| 422 | |
| 423 | add_hook(PHASE_GETRESOURCES,udp_phase_hook,st); |
| 424 | |
| 425 | return new_closure(&st->cl); |
| 426 | } |
| 427 | |
| 428 | void udp_module(dict_t *dict) |
| 429 | { |
| 430 | add_closure(dict,"udp",udp_apply); |
| 431 | } |