hesiod/hesiod.c

   1 #if defined(LIBC_SCCS) && !defined(lint)
   2 static const char rcsid[] = "$BINDId: hesiod.c,v 1.21 2000/02/28 14:51:08 vixie Exp $";
   3 #endif
   4
   5 /*
   6  * Copyright (c) 1996,1999 by Internet Software Consortium.
   7  *
   8  * Permission to use, copy, modify, and distribute this software for any
   9  * purpose with or without fee is hereby granted, provided that the above
  10  * copyright notice and this permission notice appear in all copies.
  11  *
  12  * THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
  13  * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
  14  * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
  15  * CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
  16  * DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
  17  * PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
  18  * ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
  19  * SOFTWARE.
  20  */
  21
  22 /*
  23  * This file is primarily maintained by <tytso@mit.edu> and <ghudson@mit.edu>.
  24  */
  25
  26 /*
  27  * hesiod.c --- the core portion of the hesiod resolver.
  28  *
  29  * This file is derived from the hesiod library from Project Athena;
  30  * It has been extensively rewritten by Theodore Ts'o to have a more
  31  * thread-safe interface.
  32  */
  33
  34 /* Imports */
  35
  36 #include <sys/types.h>
  37 #include <netinet/in.h>
  38 #include <arpa/nameser.h>
  39
  40 #include <errno.h>
  41 #include <netdb.h>
  42 #include <resolv.h>
  43 #include <stdio.h>
  44 #include <stdlib.h>
  45 #include <string.h>
  46
  47 #include "hesiod.h"
  48 #include "hesiod_p.h"
  49 #undef DEF_RHS
  50
  51 #define _PATH_HESIOD_CONF "/etc/hesiod.conf"
  52
  53 /* Forward */
  54
  55 int             hesiod_init(void **context);
  56 void            hesiod_end(void *context);
  57 char *          hesiod_to_bind(void *context, const char *name,
  58                                const char *type);
  59 char **         hesiod_resolve(void *context, const char *name,
  60                                const char *type);
  61 void            hesiod_free_list(void *context, char **list);
  62
  63 static int      parse_config_file(struct hesiod_p *ctx, const char *filename);
  64 static char **  get_txt_records(struct hesiod_p *ctx, int class,
  65                                 const char *name);
  66 static int      init(struct hesiod_p *ctx);
  67
  68 /* Public */
  69
  70 /*
  71  * This function is called to initialize a hesiod_p.
  72  */
  73 int
  74 hesiod_init(void **context) {
  75         struct hesiod_p *ctx;
  76         const char *configname;
  77         char *cp;
  78
  79         ctx = malloc(sizeof(struct hesiod_p));
  80         if (ctx == 0)
  81                 return (-1);
  82
  83         ctx->LHS = NULL;
  84         ctx->RHS = NULL;
  85         ctx->res = NULL;
  86
  87         configname = __secure_getenv("HESIOD_CONFIG");
  88         if (!configname)
  89           configname = _PATH_HESIOD_CONF;
  90         if (parse_config_file(ctx, configname) < 0) {
  91 #ifdef DEF_RHS
  92                 /*
  93                  * Use compiled in defaults.
  94                  */
  95                 ctx->LHS = malloc(strlen(DEF_LHS)+1);
  96                 ctx->RHS = malloc(strlen(DEF_RHS)+1);
  97                 if (ctx->LHS == 0 || ctx->RHS == 0)
  98                         goto cleanup;
  99                 strcpy(ctx->LHS, DEF_LHS);
 100                 strcpy(ctx->RHS, DEF_RHS);
 101 #else
 102                 goto cleanup;
 103 #endif
 104         }
 105         /*
 106          * The default RHS can be overridden by an environment
 107          * variable.
 108          */
 109         if ((cp = __secure_getenv("HES_DOMAIN")) != NULL) {
 110                 free(ctx->RHS);
 111                 ctx->RHS = malloc(strlen(cp)+2);
 112                 if (!ctx->RHS)
 113                         goto cleanup;
 114                 if (cp[0] == '.')
 115                         strcpy(ctx->RHS, cp);
 116                 else {
 117                         ctx->RHS[0] = '.';
 118                         strcpy(ctx->RHS + 1, cp);
 119                 }
 120         }
 121
 122         /*
 123          * If there is no default hesiod realm set, we return an
 124          * error.
 125          */
 126         if (!ctx->RHS) {
 127                 __set_errno(ENOEXEC);
 128                 goto cleanup;
 129         }
 130
 131 #if 0
 132         if (res_ninit(ctx->res) < 0)
 133                 goto cleanup;
 134 #endif
 135
 136         *context = ctx;
 137         return (0);
 138
 139  cleanup:
 140         hesiod_end(ctx);
 141         return (-1);
 142 }
 143
 144 /*
 145  * This function deallocates the hesiod_p
 146  */
 147 void
 148 hesiod_end(void *context) {
 149         struct hesiod_p *ctx = (struct hesiod_p *) context;
 150         int save_errno = errno;
 151
 152         if (ctx->res)
 153                 res_nclose(ctx->res);
 154         free(ctx->RHS);
 155         free(ctx->LHS);
 156         if (ctx->res && ctx->free_res)
 157                 (*ctx->free_res)(ctx->res);
 158         free(ctx);
 159         __set_errno(save_errno);
 160 }
 161
 162 /*
 163  * This function takes a hesiod (name, type) and returns a DNS
 164  * name which is to be resolved.
 165  */
 166 char *
 167 hesiod_to_bind(void *context, const char *name, const char *type) {
 168         struct hesiod_p *ctx = (struct hesiod_p *) context;
 169         char *bindname;
 170         char **rhs_list = NULL;
 171         const char *RHS, *cp;
 172         char *endp;
 173
 174         /* Decide what our RHS is, and set cp to the end of the actual name. */
 175         if ((cp = strchr(name, '@')) != NULL) {
 176                 if (strchr(cp + 1, '.'))
 177                         RHS = cp + 1;
 178                 else if ((rhs_list = hesiod_resolve(context, cp + 1,
 179                     "rhs-extension")) != NULL)
 180                         RHS = *rhs_list;
 181                 else {
 182                         __set_errno(ENOENT);
 183                         return (NULL);
 184                 }
 185         } else {
 186                 RHS = ctx->RHS;
 187                 cp = name + strlen(name);
 188         }
 189
 190         /*
 191          * Allocate the space we need, including up to three periods and
 192          * the terminating NUL.
 193          */
 194         if ((bindname = malloc((cp - name) + strlen(type) + strlen(RHS) +
 195             (ctx->LHS ? strlen(ctx->LHS) : 0) + 4)) == NULL) {
 196                 if (rhs_list)
 197                         hesiod_free_list(context, rhs_list);
 198                 return NULL;
 199         }
 200
 201         /* Now put together the DNS name. */
 202         endp = (char *) __mempcpy (bindname, name, cp - name);
 203         *endp++ = '.';
 204         endp = (char *) __stpcpy (endp, type);
 205         if (ctx->LHS) {
 206                 if (ctx->LHS[0] != '.')
 207                         *endp++ = '.';
 208                 endp = __stpcpy (endp, ctx->LHS);
 209         }
 210         if (RHS[0] != '.')
 211                 *endp++ = '.';
 212         strcpy (endp, RHS);
 213
 214         if (rhs_list)
 215                 hesiod_free_list(context, rhs_list);
 216
 217         return (bindname);
 218 }
 219
 220 /*
 221  * This is the core function.  Given a hesiod (name, type), it
 222  * returns an array of strings returned by the resolver.
 223  */
 224 char **
 225 hesiod_resolve(void *context, const char *name, const char *type) {
 226         struct hesiod_p *ctx = (struct hesiod_p *) context;
 227         char *bindname = hesiod_to_bind(context, name, type);
 228         char **retvec;
 229
 230         if (bindname == NULL)
 231                 return (NULL);
 232         if (init(ctx) == -1) {
 233                 free(bindname);
 234                 return (NULL);
 235         }
 236
 237         if ((retvec = get_txt_records(ctx, C_IN, bindname))) {
 238                 free(bindname);
 239                 return (retvec);
 240         }
 241
 242         if (errno != ENOENT && errno != ECONNREFUSED)
 243                 return (NULL);
 244
 245         retvec = get_txt_records(ctx, C_HS, bindname);
 246         free(bindname);
 247         return (retvec);
 248 }
 249
 250 void
 251 hesiod_free_list(void *context, char **list) {
 252         char **p;
 253
 254         for (p = list; *p; p++)
 255                 free(*p);
 256         free(list);
 257 }
 258
 259 /*
 260  * This function parses the /etc/hesiod.conf file
 261  */
 262 static int
 263 parse_config_file(struct hesiod_p *ctx, const char *filename) {
 264         char *key, *data, *cp, **cpp;
 265         char buf[MAXDNAME+7];
 266         FILE *fp;
 267
 268         /*
 269          * Clear the existing configuration variable, just in case
 270          * they're set.
 271          */
 272         free(ctx->RHS);
 273         free(ctx->LHS);
 274         ctx->RHS = ctx->LHS = 0;
 275
 276         /*
 277          * Now open and parse the file...
 278          */
 279         if (!(fp = fopen(filename, "r")))
 280                 return (-1);
 281
 282         while (fgets(buf, sizeof(buf), fp) != NULL) {
 283                 cp = buf;
 284                 if (*cp == '#' || *cp == '\n' || *cp == '\r')
 285                         continue;
 286                 while(*cp == ' ' || *cp == '\t')
 287                         cp++;
 288                 key = cp;
 289                 while(*cp != ' ' && *cp != '\t' && *cp != '=')
 290                         cp++;
 291                 *cp++ = '\0';
 292
 293                 while(*cp == ' ' || *cp == '\t' || *cp == '=')
 294                         cp++;
 295                 data = cp;
 296                 while(*cp != ' ' && *cp != '\n' && *cp != '\r')
 297                         cp++;
 298                 *cp++ = '\0';
 299
 300                 if (strcmp(key, "lhs") == 0)
 301                         cpp = &ctx->LHS;
 302                 else if (strcmp(key, "rhs") == 0)
 303                         cpp = &ctx->RHS;
 304                 else
 305                         continue;
 306
 307                 *cpp = malloc(strlen(data) + 1);
 308                 if (!*cpp)
 309                         goto cleanup;
 310                 strcpy(*cpp, data);
 311         }
 312         fclose(fp);
 313         return (0);
 314
 315  cleanup:
 316         fclose(fp);
 317         free(ctx->RHS);
 318         free(ctx->LHS);
 319         ctx->RHS = ctx->LHS = 0;
 320         return (-1);
 321 }
 322
 323 /*
 324  * Given a DNS class and a DNS name, do a lookup for TXT records, and
 325  * return a list of them.
 326  */
 327 static char **
 328 get_txt_records(struct hesiod_p *ctx, int class, const char *name) {
 329         struct {
 330                 int type;               /* RR type */
 331                 int class;              /* RR class */
 332                 int dlen;               /* len of data section */
 333                 u_char *data;           /* pointer to data */
 334         } rr;
 335         HEADER *hp;
 336         u_char qbuf[MAX_HESRESP], abuf[MAX_HESRESP];
 337         u_char *cp, *erdata, *eom;
 338         char *dst, *edst, **list;
 339         int ancount, qdcount;
 340         int i, j, n, skip;
 341
 342         /*
 343          * Construct the query and send it.
 344          */
 345         n = res_nmkquery(ctx->res, QUERY, name, class, T_TXT, NULL, 0,
 346                          NULL, qbuf, MAX_HESRESP);
 347         if (n < 0) {
 348                 __set_errno(EMSGSIZE);
 349                 return (NULL);
 350         }
 351         n = res_nsend(ctx->res, qbuf, n, abuf, MAX_HESRESP);
 352         if (n < 0) {
 353                 __set_errno(ECONNREFUSED);
 354                 return (NULL);
 355         }
 356         if (n < HFIXEDSZ) {
 357                 __set_errno(EMSGSIZE);
 358                 return (NULL);
 359         }
 360
 361         /*
 362          * OK, parse the result.
 363          */
 364         hp = (HEADER *) abuf;
 365         ancount = ntohs(hp->ancount);
 366         qdcount = ntohs(hp->qdcount);
 367         cp = abuf + sizeof(HEADER);
 368         eom = abuf + n;
 369
 370         /* Skip query, trying to get to the answer section which follows. */
 371         for (i = 0; i < qdcount; i++) {
 372                 skip = dn_skipname(cp, eom);
 373                 if (skip < 0 || cp + skip + QFIXEDSZ > eom) {
 374                         __set_errno(EMSGSIZE);
 375                         return (NULL);
 376                 }
 377                 cp += skip + QFIXEDSZ;
 378         }
 379
 380         list = malloc((ancount + 1) * sizeof(char *));
 381         if (!list)
 382                 return (NULL);
 383         j = 0;
 384         for (i = 0; i < ancount; i++) {
 385                 skip = dn_skipname(cp, eom);
 386                 if (skip < 0) {
 387                         __set_errno(EMSGSIZE);
 388                         goto cleanup;
 389                 }
 390                 cp += skip;
 391                 if (cp + 3 * INT16SZ + INT32SZ > eom) {
 392                         __set_errno(EMSGSIZE);
 393                         goto cleanup;
 394                 }
 395                 rr.type = ns_get16(cp);
 396                 cp += INT16SZ;
 397                 rr.class = ns_get16(cp);
 398                 cp += INT16SZ + INT32SZ;        /* skip the ttl, too */
 399                 rr.dlen = ns_get16(cp);
 400                 cp += INT16SZ;
 401                 if (cp + rr.dlen > eom) {
 402                         __set_errno(EMSGSIZE);
 403                         goto cleanup;
 404                 }
 405                 rr.data = cp;
 406                 cp += rr.dlen;
 407                 if (rr.class != class || rr.type != T_TXT)
 408                         continue;
 409                 if (!(list[j] = malloc(rr.dlen)))
 410                         goto cleanup;
 411                 dst = list[j++];
 412                 edst = dst + rr.dlen;
 413                 erdata = rr.data + rr.dlen;
 414                 cp = rr.data;
 415                 while (cp < erdata) {
 416                         n = (unsigned char) *cp++;
 417                         if (cp + n > eom || dst + n > edst) {
 418                                 __set_errno(EMSGSIZE);
 419                                 goto cleanup;
 420                         }
 421                         memcpy(dst, cp, n);
 422                         cp += n;
 423                         dst += n;
 424                 }
 425                 if (cp != erdata) {
 426                         __set_errno(EMSGSIZE);
 427                         goto cleanup;
 428                 }
 429                 *dst = '\0';
 430         }
 431         list[j] = NULL;
 432         if (j == 0) {
 433                 __set_errno(ENOENT);
 434                 goto cleanup;
 435         }
 436         return (list);
 437
 438  cleanup:
 439         for (i = 0; i < j; i++)
 440                 free(list[i]);
 441         free(list);
 442         return (NULL);
 443 }
 444
 445 struct __res_state *
 446 __hesiod_res_get(void *context) {
 447         struct hesiod_p *ctx = context;
 448
 449         if (!ctx->res) {
 450                 struct __res_state *res;
 451                 res = (struct __res_state *)calloc(1, sizeof *res);
 452                 if (res == NULL)
 453                         return (NULL);
 454                 __hesiod_res_set(ctx, res, free);
 455         }
 456
 457         return (ctx->res);
 458 }
 459
 460 void
 461 __hesiod_res_set(void *context, struct __res_state *res,
 462                  void (*free_res)(void *)) {
 463         struct hesiod_p *ctx = context;
 464
 465         if (ctx->res && ctx->free_res) {
 466                 res_nclose(ctx->res);
 467                 if ((ctx->res->options & RES_INIT) && ctx->res->nscount > 0) {
 468                         for (int ns = 0; ns < MAXNS; ns++) {
 469                                 free (ctx->res->_u._ext.nsaddrs[ns]);
 470                                 ctx->res->_u._ext.nsaddrs[ns] = NULL;
 471                         }
 472                 }
 473                 (*ctx->free_res)(ctx->res);
 474         }
 475
 476         ctx->res = res;
 477         ctx->free_res = free_res;
 478 }
 479
 480 static int
 481 init(struct hesiod_p *ctx) {
 482
 483         if (!ctx->res && !__hesiod_res_get(ctx))
 484                 return (-1);
 485
 486         if (__res_maybe_init (ctx->res, 0) == -1)
 487                 return (-1);
 488
 489         return (0);
 490 }