usr.sbin/ypserv/yp_dnslookup.c

   1 /*
   2  * Copyright (c) 1995, 1996
   3  *      Bill Paul <wpaul@ctr.columbia.edu>. All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by Bill Paul.
  16  * 4. Neither the name of the University nor the names of its contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY Bill Paul AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL Bill Paul OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  *
  32  * $FreeBSD: src/usr.sbin/ypserv/yp_dnslookup.c,v 1.27 2005/05/20 13:04:10 charnier Exp $
  33  * $DragonFly: src/usr.sbin/ypserv/yp_dnslookup.c,v 1.4 2005/11/24 22:23:02 swildner Exp $
  34  */
  35
  36 /*
  37  * Do standard and reverse DNS lookups using the resolver library.
  38  * Take care of all the dirty work here so the main program only has to
  39  * pass us a pointer to an array of characters.
  40  *
  41  * We have to use direct resolver calls here otherwise the YP server
  42  * could end up looping by calling itself over and over again until
  43  * it disappeared up its own belly button.
  44  */
  45
  46 #include <sys/param.h>
  47 #include <sys/socket.h>
  48 #include <sys/time.h>
  49 #include <sys/fcntl.h>
  50 #include <sys/queue.h>
  51 #include <netinet/in.h>
  52 #include <arpa/inet.h>
  53 #include <arpa/nameser.h>
  54
  55 #include <ctype.h>
  56 #include <errno.h>
  57 #include <netdb.h>
  58 #include <stdio.h>
  59 #include <stdlib.h>
  60 #include <string.h>
  61 #include <resolv.h>
  62 #include <unistd.h>
  63
  64 #include <rpcsvc/yp.h>
  65 #include "yp_extern.h"
  66
  67 static char *
  68 parse(struct hostent *hp)
  69 {
  70         static char result[MAXHOSTNAMELEN * 2];
  71         int i;
  72         size_t len;
  73         char addr[46];
  74
  75         if (hp == NULL)
  76                 return(NULL);
  77
  78         if (inet_ntop(hp->h_addrtype, hp->h_addr, addr, sizeof(addr)) == NULL)
  79                 return(NULL);
  80
  81         len = strlen(addr) + 1 + strlen(hp->h_name);
  82         for (i = 0; hp->h_aliases[i]; i++)
  83                 len += strlen(hp->h_aliases[i]) + 1;
  84         len++;
  85
  86         if (len > sizeof(result))
  87                 return(NULL);
  88
  89         bzero(result, sizeof(result));
  90         snprintf(result, sizeof(result), "%s %s", addr, hp->h_name);
  91         for (i = 0; hp->h_aliases[i]; i++) {
  92                 strcat(result, " ");
  93                 strcat(result, hp->h_aliases[i]);
  94         }
  95
  96         return ((char *)&result);
  97 }
  98
  99 #define MAXPACKET (64*1024)
 100 #define DEF_TTL 50
 101
 102 #define BY_DNS_ID 1
 103 #define BY_RPC_XID 2
 104
 105 extern struct hostent *__dns_getanswer(char *, int, char *, int);
 106
 107 static TAILQ_HEAD(dns_qhead, circleq_dnsentry) qhead;
 108
 109 struct circleq_dnsentry {
 110         SVCXPRT *xprt;
 111         unsigned long xid;
 112         struct sockaddr_in client_addr;
 113         unsigned long ypvers;
 114         unsigned long id;
 115         unsigned long ttl;
 116         unsigned long type;
 117         unsigned short prot_type;
 118         char **domain;
 119         char *name;
 120         int addrtype;
 121         int addrlen;
 122         uint32_t addr[4];       /* IPv4 or IPv6 */
 123         TAILQ_ENTRY(circleq_dnsentry) links;
 124 };
 125
 126 static int pending = 0;
 127
 128 int
 129 yp_init_resolver(void)
 130 {
 131         TAILQ_INIT(&qhead);
 132         if (!(_res.options & RES_INIT) && res_init() == -1) {
 133                 yp_error("res_init failed");
 134                 return(1);
 135         }
 136         if ((resfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
 137                 yp_error("couldn't create socket");
 138                 return(1);
 139         }
 140         if (fcntl(resfd, F_SETFL, O_NONBLOCK) == -1) {
 141                 yp_error("couldn't make resolver socket non-blocking");
 142                 return(1);
 143         }
 144         return(0);
 145 }
 146
 147 static struct circleq_dnsentry *
 148 yp_malloc_dnsent(void)
 149 {
 150         struct circleq_dnsentry *q;
 151
 152         q = (struct circleq_dnsentry *)malloc(sizeof(struct circleq_dnsentry));
 153
 154         if (q == NULL) {
 155                 yp_error("failed to malloc() circleq dns entry");
 156                 return(NULL);
 157         }
 158
 159         return(q);
 160 }
 161
 162 /*
 163  * Transmit a query.
 164  */
 165 static unsigned long
 166 yp_send_dns_query(char *name, int type)
 167 {
 168         char buf[MAXPACKET];
 169         int n;
 170         HEADER *hptr;
 171         int ns;
 172         int rval;
 173         unsigned long id;
 174
 175         bzero(buf, sizeof(buf));
 176
 177         n = res_mkquery(QUERY,name,C_IN,type,NULL,0,NULL,buf,sizeof(buf));
 178
 179         if (n <= 0) {
 180                 yp_error("res_mkquery failed for %s type %d", name, type);
 181                 return(0);
 182         }
 183
 184         hptr = (HEADER *)&buf;
 185         id = ntohs(hptr->id);
 186
 187         for (ns = 0; ns < _res.nscount; ns++) {
 188                 rval = sendto(resfd, buf, n, 0,
 189                         (struct sockaddr *)&_res.nsaddr_list[ns],
 190                                 sizeof(struct sockaddr));
 191                 if (rval == -1) {
 192                         yp_error("sendto failed");
 193                         return(0);
 194                 }
 195         }
 196
 197         return(id);
 198 }
 199
 200 static struct circleq_dnsentry *
 201 yp_find_dnsqent(unsigned long id, int type)
 202 {
 203         struct circleq_dnsentry *q;
 204
 205         TAILQ_FOREACH(q, &qhead, links) {
 206                 switch (type) {
 207                 case BY_RPC_XID:
 208                         if (id == q->xid)
 209                                 return(q);
 210                         break;
 211                 case BY_DNS_ID:
 212                 default:
 213                         if (id == q->id)
 214                                 return(q);
 215                         break;
 216                 }
 217         }
 218         return (NULL);
 219 }
 220
 221 static void
 222 yp_send_dns_reply(struct circleq_dnsentry *q, char *buf)
 223 {
 224         ypresponse result_v1;
 225         ypresp_val result_v2;
 226         unsigned long xid;
 227         struct sockaddr_in client_addr;
 228         xdrproc_t xdrfunc;
 229         char *result;
 230
 231         /*
 232          * Set up correct reply struct and
 233          * XDR filter depending on ypvers.
 234          */
 235         switch (q->ypvers) {
 236         case YPVERS:
 237                 bzero((char *)&result_v2, sizeof(result_v2));
 238
 239                 if (buf == NULL)
 240                         result_v2.stat = YP_NOKEY;
 241                 else {
 242                         result_v2.val.valdat_len = strlen(buf);
 243                         result_v2.val.valdat_val = buf;
 244                         result_v2.stat = YP_TRUE;
 245                 }
 246                 result = (char *)&result_v2;
 247                 xdrfunc = (xdrproc_t)xdr_ypresp_val;
 248                 break;
 249         case YPOLDVERS:
 250                 /*
 251                  * The odds are we will _never_ execute this
 252                  * particular code, but we include it anyway
 253                  * for the sake of completeness.
 254                  */
 255                 bzero((char *)&result_v1, sizeof(result_v1));
 256                 result_v1.yp_resptype = YPRESP_VAL;
 257
 258 #define YPVAL ypresponse_u.yp_resp_valtype
 259                 if (buf == NULL)
 260                         result_v1.YPVAL.stat = YP_NOKEY;
 261                 else {
 262                         result_v1.YPVAL.val.valdat_len = strlen(buf);
 263                         result_v1.YPVAL.val.valdat_val = buf;
 264                         result_v1.YPVAL.stat = YP_TRUE;
 265                 }
 266                 result = (char *)&result_v1;
 267                 xdrfunc = (xdrproc_t)xdr_ypresponse;
 268                 break;
 269         default:
 270                 yp_error("bad YP program version (%lu)!", q->ypvers);
 271                         return;
 272                 break;
 273         }
 274
 275         if (debug)
 276                 yp_error("sending dns reply to %s (%lu)",
 277                         inet_ntoa(q->client_addr.sin_addr), q->id);
 278         /*
 279          * XXX This is disgusting. There's basically one transport
 280          * handle for UDP, but we're holding off on replying to a
 281          * client until we're ready, by which time we may have received
 282          * several other queries from other clients with different
 283          * transaction IDs. So to make the delayed response thing work,
 284          * we have to save the transaction ID and client address of
 285          * each request, then jam them into the transport handle when
 286          * we're ready to send a reply. Then after we've send the reply,
 287          * we put the old transaction ID and remote address back the
 288          * way we found 'em. This is _INCREDIBLY_ non-portable; it's
 289          * not even supported by the RPC library.
 290          */
 291         /*
 292          * XXX Don't frob the transaction ID for TCP handles.
 293          */
 294         if (q->prot_type == SOCK_DGRAM)
 295                 xid = svcudp_set_xid(q->xprt, q->xid);
 296         client_addr = q->xprt->xp_raddr;
 297         q->xprt->xp_raddr = q->client_addr;
 298
 299         if (!svc_sendreply(q->xprt, xdrfunc, result))
 300                 yp_error("svc_sendreply failed");
 301
 302         /*
 303          * Now that we sent the reply,
 304          * put the handle back the way it was.
 305          */
 306         if (q->prot_type == SOCK_DGRAM)
 307                 svcudp_set_xid(q->xprt, xid);
 308         q->xprt->xp_raddr = client_addr;
 309
 310         return;
 311 }
 312
 313 /*
 314  * Decrement TTL on all queue entries, possibly nuking
 315  * any that have been around too long without being serviced.
 316  */
 317 void
 318 yp_prune_dnsq(void)
 319 {
 320         struct circleq_dnsentry *q, *n;
 321
 322         q = TAILQ_FIRST(&qhead);
 323         while (q != NULL) {
 324                 q->ttl--;
 325                 n = TAILQ_NEXT(q, links);
 326                 if (!q->ttl) {
 327                         TAILQ_REMOVE(&qhead, q, links);
 328                         free(q->name);
 329                         free(q);
 330                         pending--;
 331                 }
 332                 q = n;
 333         }
 334
 335         if (pending < 0)
 336                 pending = 0;
 337
 338         return;
 339 }
 340
 341 /*
 342  * Data is pending on the DNS socket; check for valid replies
 343  * to our queries and dispatch them to waiting clients.
 344  */
 345 void
 346 yp_run_dnsq(void)
 347 {
 348         struct circleq_dnsentry *q;
 349         char buf[sizeof(HEADER) + MAXPACKET];
 350         struct sockaddr_in sin;
 351         socklen_t len;
 352         int rval;
 353         HEADER *hptr;
 354         struct hostent *hent;
 355
 356         if (debug)
 357                 yp_error("running dns queue");
 358
 359         bzero(buf, sizeof(buf));
 360
 361         len = sizeof(struct sockaddr_in);
 362         rval = recvfrom(resfd, buf, sizeof(buf), 0,
 363                         (struct sockaddr *)&sin, &len);
 364
 365         if (rval == -1) {
 366                 yp_error("recvfrom failed: %s", strerror(errno));
 367                 return;
 368         }
 369
 370         /*
 371          * We may have data left in the socket that represents
 372          * replies to earlier queries that we don't care about
 373          * anymore. If there are no lookups pending or the packet
 374          * ID doesn't match any of the queue IDs, just drop it
 375          * on the floor.
 376          */
 377         hptr = (HEADER *)&buf;
 378         if (!pending ||
 379                 (q = yp_find_dnsqent(ntohs(hptr->id), BY_DNS_ID)) == NULL) {
 380                 /* ignore */
 381                 return;
 382         }
 383
 384         if (debug)
 385                 yp_error("got dns reply from %s", inet_ntoa(sin.sin_addr));
 386
 387         hent = __dns_getanswer(buf, rval, q->name, q->type);
 388
 389         if (hent != NULL) {
 390                 if (q->type == T_PTR) {
 391                         hent->h_addr = (char *)q->addr;
 392                         hent->h_addrtype = q->addrtype;
 393                         hent->h_length = q->addrlen;
 394                 }
 395         }
 396
 397         /* Got an answer ready for a client -- send it off. */
 398         yp_send_dns_reply(q, parse(hent));
 399         pending--;
 400         TAILQ_REMOVE(&qhead, q, links);
 401         free(q->name);
 402         free(q);
 403
 404         /* Decrement TTLs on other entries while we're here. */
 405         yp_prune_dnsq();
 406
 407         return;
 408 }
 409
 410 /*
 411  * Queue and transmit an asynchronous DNS hostname lookup.
 412  */
 413 ypstat
 414 yp_async_lookup_name(struct svc_req *rqstp, char *name, int af)
 415 {
 416         struct circleq_dnsentry *q;
 417         socklen_t len;
 418         int type;
 419
 420         /* Check for SOCK_DGRAM or SOCK_STREAM -- we need to know later */
 421         type = -1;
 422         len = sizeof(type);
 423         if (getsockopt(rqstp->rq_xprt->xp_fd, SOL_SOCKET,
 424                                         SO_TYPE, &type, &len) == -1) {
 425                 yp_error("getsockopt failed: %s", strerror(errno));
 426                 return(YP_YPERR);
 427         }
 428
 429         /* Avoid transmitting dupe requests. */
 430         if (type == SOCK_DGRAM &&
 431             yp_find_dnsqent(svcudp_get_xid(rqstp->rq_xprt),BY_RPC_XID) != NULL)
 432                 return(YP_TRUE);
 433
 434         if ((q = yp_malloc_dnsent()) == NULL)
 435                 return(YP_YPERR);
 436
 437         q->type = (af == AF_INET) ? T_A : T_AAAA;
 438         q->ttl = DEF_TTL;
 439         q->xprt = rqstp->rq_xprt;
 440         q->ypvers = rqstp->rq_vers;
 441         q->prot_type = type;
 442         if (q->prot_type == SOCK_DGRAM)
 443                 q->xid = svcudp_get_xid(q->xprt);
 444         q->client_addr = q->xprt->xp_raddr;
 445         q->domain = _res.dnsrch;
 446         q->id = yp_send_dns_query(name, q->type);
 447
 448         if (q->id == 0) {
 449                 yp_error("DNS query failed");
 450                 free(q);
 451                 return(YP_YPERR);
 452         }
 453
 454         q->name = strdup(name);
 455         TAILQ_INSERT_HEAD(&qhead, q, links);
 456         pending++;
 457
 458         if (debug)
 459                 yp_error("queueing async DNS name lookup (%d)", q->id);
 460
 461         yp_prune_dnsq();
 462         return(YP_TRUE);
 463 }
 464
 465 /*
 466  * Queue and transmit an asynchronous DNS IP address lookup.
 467  */
 468 ypstat
 469 yp_async_lookup_addr(struct svc_req *rqstp, char *addr, int af)
 470 {
 471         struct circleq_dnsentry *q;
 472         char buf[MAXHOSTNAMELEN], *qp;
 473         uint32_t abuf[4];       /* IPv4 or IPv6 */
 474         u_char *uaddr = (u_char *)abuf;
 475         socklen_t len;
 476         int type, n;
 477
 478         /* Check for SOCK_DGRAM or SOCK_STREAM -- we need to know later */
 479         type = -1;
 480         len = sizeof(type);
 481         if (getsockopt(rqstp->rq_xprt->xp_fd, SOL_SOCKET,
 482                                         SO_TYPE, &type, &len) == -1) {
 483                 yp_error("getsockopt failed: %s", strerror(errno));
 484                 return(YP_YPERR);
 485         }
 486
 487         /* Avoid transmitting dupe requests. */
 488         if (type == SOCK_DGRAM &&
 489             yp_find_dnsqent(svcudp_get_xid(rqstp->rq_xprt),BY_RPC_XID) != NULL)
 490                 return(YP_TRUE);
 491
 492         if ((q = yp_malloc_dnsent()) == NULL)
 493                 return(YP_YPERR);
 494
 495         switch (af) {
 496         case AF_INET:
 497                 if (inet_aton(addr, (struct in_addr *)uaddr) != 1)
 498                         return(YP_NOKEY);
 499                 snprintf(buf, sizeof(buf), "%u.%u.%u.%u.in-addr.arpa",
 500                     (uaddr[3] & 0xff), (uaddr[2] & 0xff),
 501                     (uaddr[1] & 0xff), (uaddr[0] & 0xff));
 502                 len = INADDRSZ;
 503                 break;
 504         case AF_INET6:
 505                 if (inet_pton(af, addr, uaddr) != 1)
 506                         return(YP_NOKEY);
 507                 qp = buf;
 508                 for (n = IN6ADDRSZ - 1; n >= 0; n--) {
 509                         qp += (size_t)sprintf(qp, "%x.%x.", uaddr[n] & 0xf,
 510                             (uaddr[n] >> 4) & 0xf);
 511                 }
 512                 strlcat(buf, "ip6.arpa", sizeof(buf));
 513                 len = IN6ADDRSZ;
 514                 break;
 515         default:
 516                 return(YP_YPERR);
 517         }
 518
 519         if (debug)
 520                 yp_error("DNS address is: %s", buf);
 521
 522         q->type = T_PTR;
 523         q->ttl = DEF_TTL;
 524         q->xprt = rqstp->rq_xprt;
 525         q->ypvers = rqstp->rq_vers;
 526         q->domain = NULL;
 527         q->prot_type = type;
 528         if (q->prot_type == SOCK_DGRAM)
 529                 q->xid = svcudp_get_xid(q->xprt);
 530         q->client_addr = q->xprt->xp_raddr;
 531         q->id = yp_send_dns_query(buf, q->type);
 532
 533         if (q->id == 0) {
 534                 yp_error("DNS query failed");
 535                 free(q);
 536                 return(YP_YPERR);
 537         }
 538
 539         memcpy(q->addr, uaddr, len);
 540         q->addrlen = len;
 541         q->addrtype = af;
 542         q->name = strdup(buf);
 543         TAILQ_INSERT_HEAD(&qhead, q, links);
 544         pending++;
 545
 546         if (debug)
 547                 yp_error("queueing async DNS address lookup (%d)", q->id);
 548
 549         yp_prune_dnsq();
 550         return(YP_TRUE);
 551 }