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 1.16.2.1 2002/02/15 00:47:00 des 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 len,i;
  72         struct in_addr addr;
  73
  74         if (hp == NULL)
  75                 return(NULL);
  76
  77         len = 16 + strlen(hp->h_name);
  78         for (i = 0; hp->h_aliases[i]; i++)
  79                 len += strlen(hp->h_aliases[i]) + 1;
  80         len++;
  81
  82         if (len > sizeof(result))
  83                 return(NULL);
  84
  85         bzero(result, sizeof(result));
  86
  87         bcopy(hp->h_addr, &addr, sizeof(struct in_addr));
  88         snprintf(result, sizeof(result), "%s %s", inet_ntoa(addr), hp->h_name);
  89
  90         for (i = 0; hp->h_aliases[i]; i++) {
  91                 strcat(result, " ");
  92                 strcat(result, hp->h_aliases[i]);
  93         }
  94
  95         return ((char *)&result);
  96 }
  97
  98 #define MAXPACKET 1024
  99 #define DEF_TTL 50
 100
 101 #define BY_DNS_ID 1
 102 #define BY_RPC_XID 2
 103
 104 extern struct hostent *__dns_getanswer(char *, int, char *, int);
 105
 106 static CIRCLEQ_HEAD(dns_qhead, circleq_dnsentry) qhead;
 107
 108 struct circleq_dnsentry {
 109         SVCXPRT *xprt;
 110         unsigned long xid;
 111         struct sockaddr_in client_addr;
 112         unsigned long ypvers;
 113         unsigned long id;
 114         unsigned long ttl;
 115         unsigned long type;
 116         unsigned short prot_type;
 117         char **domain;
 118         char *name;
 119         struct in_addr addr;
 120         CIRCLEQ_ENTRY(circleq_dnsentry) links;
 121 };
 122
 123 static int pending = 0;
 124
 125 int
 126 yp_init_resolver(void)
 127 {
 128         CIRCLEQ_INIT(&qhead);
 129         if (!(_res.options & RES_INIT) && res_init() == -1) {
 130                 yp_error("res_init failed");
 131                 return(1);
 132         }
 133         if ((resfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
 134                 yp_error("couldn't create socket");
 135                 return(1);
 136         }
 137         if (fcntl(resfd, F_SETFL, O_NONBLOCK) == -1) {
 138                 yp_error("couldn't make resolver socket non-blocking");
 139                 return(1);
 140         }
 141         return(0);
 142 }
 143
 144 static struct circleq_dnsentry *
 145 yp_malloc_dnsent(void)
 146 {
 147         struct circleq_dnsentry *q;
 148
 149         q = (struct circleq_dnsentry *)malloc(sizeof(struct circleq_dnsentry));
 150
 151         if (q == NULL) {
 152                 yp_error("failed to malloc() circleq dns entry");
 153                 return(NULL);
 154         }
 155
 156         return(q);
 157 }
 158
 159 /*
 160  * Transmit a query.
 161  */
 162 static unsigned long
 163 yp_send_dns_query(char *name, int type)
 164 {
 165         char buf[MAXPACKET];
 166         int n;
 167         HEADER *hptr;
 168         int ns;
 169         int rval;
 170         unsigned long id;
 171
 172         bzero(buf, sizeof(buf));
 173
 174         n = res_mkquery(QUERY,name,C_IN,type,NULL,0,NULL,buf,sizeof(buf));
 175
 176         if (n <= 0) {
 177                 yp_error("res_mkquery failed");
 178                 return(0);
 179         }
 180
 181         hptr = (HEADER *)&buf;
 182         id = ntohs(hptr->id);
 183
 184         for (ns = 0; ns < _res.nscount; ns++) {
 185                 rval = sendto(resfd, buf, n, 0,
 186                         (struct sockaddr *)&_res.nsaddr_list[ns],
 187                                 sizeof(struct sockaddr));
 188                 if (rval == -1) {
 189                         yp_error("sendto failed");
 190                         return(0);
 191                 }
 192         }
 193
 194         return(id);
 195 }
 196
 197 static struct circleq_dnsentry *
 198 yp_find_dnsqent(unsigned long id, int type)
 199 {
 200         struct circleq_dnsentry *q;
 201
 202         for (q = qhead.cqh_first; q != (void *)&qhead; q = q->links.cqe_next) {
 203                 switch (type) {
 204                 case BY_RPC_XID:
 205                         if (id == q->xid)
 206                                 return(q);
 207                         break;
 208                 case BY_DNS_ID:
 209                 default:
 210                         if (id == q->id)
 211                                 return(q);
 212                         break;
 213                 }
 214         }
 215         return (NULL);
 216 }
 217
 218 static void
 219 yp_send_dns_reply(struct circleq_dnsentry *q, char *buf)
 220 {
 221         ypresponse result_v1;
 222         ypresp_val result_v2;
 223         unsigned long xid;
 224         struct sockaddr_in client_addr;
 225         xdrproc_t xdrfunc;
 226         char *result;
 227
 228         /*
 229          * Set up correct reply struct and
 230          * XDR filter depending on ypvers.
 231          */
 232         switch (q->ypvers) {
 233         case YPVERS:
 234                 bzero((char *)&result_v2, sizeof(result_v2));
 235
 236                 if (buf == NULL)
 237                         result_v2.stat = YP_NOKEY;
 238                 else {
 239                         result_v2.val.valdat_len = strlen(buf);
 240                         result_v2.val.valdat_val = buf;
 241                         result_v2.stat = YP_TRUE;
 242                 }
 243                 result = (char *)&result_v2;
 244                 xdrfunc = (xdrproc_t)xdr_ypresp_val;
 245                 break;
 246         case YPOLDVERS:
 247                 /*
 248                  * The odds are we will _never_ execute this
 249                  * particular code, but we include it anyway
 250                  * for the sake of completeness.
 251                  */
 252                 bzero((char *)&result_v1, sizeof(result_v1));
 253                 result_v1.yp_resptype = YPRESP_VAL;
 254 #               define YPVAL ypresponse_u.yp_resp_valtype
 255
 256                 if (buf == NULL)
 257                         result_v1.YPVAL.stat = YP_NOKEY;
 258                 else {
 259                         result_v1.YPVAL.val.valdat_len = strlen(buf);
 260                         result_v1.YPVAL.val.valdat_val = buf;
 261                         result_v1.YPVAL.stat = YP_TRUE;
 262                 }
 263                 result = (char *)&result_v1;
 264                 xdrfunc = (xdrproc_t)xdr_ypresponse;
 265                 break;
 266         default:
 267                 yp_error("bad YP program version (%lu)!", q->ypvers);
 268                         return;
 269                 break;
 270         }
 271
 272         if (debug)
 273                 yp_error("sending dns reply to %s (%lu)",
 274                         inet_ntoa(q->client_addr.sin_addr), q->id);
 275         /*
 276          * XXX This is disgusting. There's basically one transport
 277          * handle for UDP, but we're holding off on replying to a
 278          * client until we're ready, by which time we may have received
 279          * several other queries from other clients with different
 280          * transaction IDs. So to make the delayed response thing work,
 281          * we have to save the transaction ID and client address of
 282          * each request, then jam them into the transport handle when
 283          * we're ready to send a reply. Then after we've send the reply,
 284          * we put the old transaction ID and remote address back the
 285          * way we found 'em. This is _INCREDIBLY_ non-portable; it's
 286          * not even supported by the RPC library.
 287          */
 288         /*
 289          * XXX Don't frob the transaction ID for TCP handles.
 290          */
 291         if (q->prot_type == SOCK_DGRAM)
 292                 xid = svcudp_set_xid(q->xprt, q->xid);
 293         client_addr = q->xprt->xp_raddr;
 294         q->xprt->xp_raddr = q->client_addr;
 295
 296         if (!svc_sendreply(q->xprt, xdrfunc, result))
 297                 yp_error("svc_sendreply failed");
 298
 299         /*
 300          * Now that we sent the reply,
 301          * put the handle back the way it was.
 302          */
 303         if (q->prot_type == SOCK_DGRAM)
 304                 svcudp_set_xid(q->xprt, xid);
 305         q->xprt->xp_raddr = client_addr;
 306
 307         return;
 308 }
 309
 310 /*
 311  * Decrement TTL on all queue entries, possibly nuking
 312  * any that have been around too long without being serviced.
 313  */
 314 void
 315 yp_prune_dnsq(void)
 316 {
 317         struct circleq_dnsentry *q, *n;
 318
 319         q = qhead.cqh_first;
 320         while (q != (void *)&qhead) {
 321                 q->ttl--;
 322                 n = q->links.cqe_next;
 323                 if (!q->ttl) {
 324                         CIRCLEQ_REMOVE(&qhead, q, links);
 325                         free(q->name);
 326                         free(q);
 327                         pending--;
 328                 }
 329                 q = n;
 330         }
 331
 332         if (pending < 0)
 333                 pending = 0;
 334
 335         return;
 336 }
 337
 338 /*
 339  * Data is pending on the DNS socket; check for valid replies
 340  * to our queries and dispatch them to waiting clients.
 341  */
 342 void
 343 yp_run_dnsq(void)
 344 {
 345         struct circleq_dnsentry *q;
 346         char buf[sizeof(HEADER) + MAXPACKET];
 347         char retrybuf[MAXHOSTNAMELEN];
 348         struct sockaddr_in sin;
 349         int rval;
 350         int len;
 351         HEADER *hptr;
 352         struct hostent *hent;
 353
 354         if (debug)
 355                 yp_error("running dns queue");
 356
 357         bzero(buf, sizeof(buf));
 358
 359         len = sizeof(struct sockaddr_in);
 360         rval = recvfrom(resfd, buf, sizeof(buf), 0,
 361                         (struct sockaddr *)&sin, &len);
 362
 363         if (rval == -1) {
 364                 yp_error("recvfrom failed: %s", strerror(errno));
 365                 return;
 366         }
 367
 368         /*
 369          * We may have data left in the socket that represents
 370          * replies to earlier queries that we don't care about
 371          * anymore. If there are no lookups pending or the packet
 372          * ID doesn't match any of the queue IDs, just drop it
 373          * on the floor.
 374          */
 375         hptr = (HEADER *)&buf;
 376         if (!pending ||
 377                 (q = yp_find_dnsqent(ntohs(hptr->id), BY_DNS_ID)) == NULL) {
 378                 /* ignore */
 379                 return;
 380         }
 381
 382         if (debug)
 383                 yp_error("got dns reply from %s", inet_ntoa(sin.sin_addr));
 384
 385         hent = __dns_getanswer(buf, rval, q->name, q->type);
 386
 387         /*
 388          * If the lookup failed, try appending one of the domains
 389          * from resolv.conf. If we have no domains to test, the
 390          * query has failed.
 391          */
 392         if (hent == NULL) {
 393                 if ((h_errno == TRY_AGAIN || h_errno == NO_RECOVERY)
 394                                         && q->domain && *q->domain) {
 395                         snprintf(retrybuf, sizeof(retrybuf), "%s.%s",
 396                                                 q->name, *q->domain);
 397                         if (debug)
 398                                 yp_error("retrying with: %s", retrybuf);
 399                         q->id = yp_send_dns_query(retrybuf, q->type);
 400                         q->ttl = DEF_TTL;
 401                         q->domain++;
 402                         return;
 403                 }
 404         } else {
 405                 if (q->type == T_PTR) {
 406                         hent->h_addr = (char *)&q->addr.s_addr;
 407                         hent->h_length = sizeof(struct in_addr);
 408                 }
 409         }
 410
 411         /* Got an answer ready for a client -- send it off. */
 412         yp_send_dns_reply(q, parse(hent));
 413         pending--;
 414         CIRCLEQ_REMOVE(&qhead, q, links);
 415         free(q->name);
 416         free(q);
 417
 418         /* Decrement TTLs on other entries while we're here. */
 419         yp_prune_dnsq();
 420
 421         return;
 422 }
 423
 424 /*
 425  * Queue and transmit an asynchronous DNS hostname lookup.
 426  */
 427 ypstat
 428 yp_async_lookup_name(struct svc_req *rqstp, char *name)
 429 {
 430         struct circleq_dnsentry *q;
 431         int type, len;
 432
 433         /* Check for SOCK_DGRAM or SOCK_STREAM -- we need to know later */
 434         type = -1; len = sizeof(type);
 435         if (getsockopt(rqstp->rq_xprt->xp_sock, SOL_SOCKET,
 436                                         SO_TYPE, &type, &len) == -1) {
 437                 yp_error("getsockopt failed: %s", strerror(errno));
 438                 return(YP_YPERR);
 439         }
 440
 441         /* Avoid transmitting dupe requests. */
 442         if (type == SOCK_DGRAM &&
 443             yp_find_dnsqent(svcudp_get_xid(rqstp->rq_xprt),BY_RPC_XID) != NULL)
 444                 return(YP_TRUE);
 445
 446         if ((q = yp_malloc_dnsent()) == NULL)
 447                 return(YP_YPERR);
 448
 449         q->type = T_A;
 450         q->ttl = DEF_TTL;
 451         q->xprt = rqstp->rq_xprt;
 452         q->ypvers = rqstp->rq_vers;
 453         q->prot_type = type;
 454         if (q->prot_type == SOCK_DGRAM)
 455                 q->xid = svcudp_get_xid(q->xprt);
 456         q->client_addr = q->xprt->xp_raddr;
 457         q->domain = _res.dnsrch;
 458         q->id = yp_send_dns_query(name, q->type);
 459
 460         if (q->id == 0) {
 461                 yp_error("DNS query failed");
 462                 free(q);
 463                 return(YP_YPERR);
 464         }
 465
 466         q->name = strdup(name);
 467         CIRCLEQ_INSERT_HEAD(&qhead, q, links);
 468         pending++;
 469
 470         if (debug)
 471                 yp_error("queueing async DNS name lookup (%d)", q->id);
 472
 473         yp_prune_dnsq();
 474         return(YP_TRUE);
 475 }
 476
 477 /*
 478  * Queue and transmit an asynchronous DNS IP address lookup.
 479  */
 480 ypstat
 481 yp_async_lookup_addr(struct svc_req *rqstp, char *addr)
 482 {
 483         struct circleq_dnsentry *q;
 484         char buf[MAXHOSTNAMELEN];
 485         int a, b, c, d;
 486         int type, len;
 487
 488         /* Check for SOCK_DGRAM or SOCK_STREAM -- we need to know later */
 489         type = -1; len = sizeof(type);
 490         if (getsockopt(rqstp->rq_xprt->xp_sock, SOL_SOCKET,
 491                                         SO_TYPE, &type, &len) == -1) {
 492                 yp_error("getsockopt failed: %s", strerror(errno));
 493                 return(YP_YPERR);
 494         }
 495
 496         /* Avoid transmitting dupe requests. */
 497         if (type == SOCK_DGRAM &&
 498             yp_find_dnsqent(svcudp_get_xid(rqstp->rq_xprt),BY_RPC_XID) != NULL)
 499                 return(YP_TRUE);
 500
 501         if ((q = yp_malloc_dnsent()) == NULL)
 502                 return(YP_YPERR);
 503
 504         if (sscanf(addr, "%d.%d.%d.%d", &a, &b, &c, &d) != 4)
 505                 return(YP_NOKEY);
 506
 507         snprintf(buf, sizeof(buf), "%d.%d.%d.%d.in-addr.arpa", d, c, b, a);
 508
 509         if (debug)
 510                 yp_error("DNS address is: %s", buf);
 511
 512         q->type = T_PTR;
 513         q->ttl = DEF_TTL;
 514         q->xprt = rqstp->rq_xprt;
 515         q->ypvers = rqstp->rq_vers;
 516         q->domain = NULL;
 517         q->prot_type = type;
 518         if (q->prot_type == SOCK_DGRAM)
 519                 q->xid = svcudp_get_xid(q->xprt);
 520         q->client_addr = q->xprt->xp_raddr;
 521         q->id = yp_send_dns_query(buf, q->type);
 522
 523         if (q->id == 0) {
 524                 yp_error("DNS query failed");
 525                 free(q);
 526                 return(YP_YPERR);
 527         }
 528
 529         inet_aton(addr, &q->addr);
 530         q->name = strdup(buf);
 531         CIRCLEQ_INSERT_HEAD(&qhead, q, links);
 532         pending++;
 533
 534         if (debug)
 535                 yp_error("queueing async DNS address lookup (%d)", q->id);
 536
 537         yp_prune_dnsq();
 538         return(YP_TRUE);
 539 }