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         /* Set default query classes. */
  87         ctx->classes[0] = C_IN;
  88         ctx->classes[1] = C_HS;
  89
  90         configname = __libc_secure_getenv("HESIOD_CONFIG");
  91         if (!configname)
  92           configname = _PATH_HESIOD_CONF;
  93         if (parse_config_file(ctx, configname) < 0) {
  94 #ifdef DEF_RHS
  95                 /*
  96                  * Use compiled in defaults.
  97                  */
  98                 ctx->LHS = malloc(strlen(DEF_LHS)+1);
  99                 ctx->RHS = malloc(strlen(DEF_RHS)+1);
 100                 if (ctx->LHS == 0 || ctx->RHS == 0)
 101                         goto cleanup;
 102                 strcpy(ctx->LHS, DEF_LHS);
 103                 strcpy(ctx->RHS, DEF_RHS);
 104 #else
 105                 goto cleanup;
 106 #endif
 107         }
 108         /*
 109          * The default RHS can be overridden by an environment
 110          * variable.
 111          */
 112         if ((cp = __libc_secure_getenv("HES_DOMAIN")) != NULL) {
 113                 free(ctx->RHS);
 114                 ctx->RHS = malloc(strlen(cp)+2);
 115                 if (!ctx->RHS)
 116                         goto cleanup;
 117                 if (cp[0] == '.')
 118                         strcpy(ctx->RHS, cp);
 119                 else {
 120                         ctx->RHS[0] = '.';
 121                         strcpy(ctx->RHS + 1, cp);
 122                 }
 123         }
 124
 125         /*
 126          * If there is no default hesiod realm set, we return an
 127          * error.
 128          */
 129         if (!ctx->RHS) {
 130                 __set_errno(ENOEXEC);
 131                 goto cleanup;
 132         }
 133
 134 #if 0
 135         if (res_ninit(ctx->res) < 0)
 136                 goto cleanup;
 137 #endif
 138
 139         *context = ctx;
 140         return (0);
 141
 142  cleanup:
 143         hesiod_end(ctx);
 144         return (-1);
 145 }
 146
 147 /*
 148  * This function deallocates the hesiod_p
 149  */
 150 void
 151 hesiod_end(void *context) {
 152         struct hesiod_p *ctx = (struct hesiod_p *) context;
 153         int save_errno = errno;
 154
 155         if (ctx->res)
 156                 res_nclose(ctx->res);
 157         free(ctx->RHS);
 158         free(ctx->LHS);
 159         if (ctx->res && ctx->free_res)
 160                 (*ctx->free_res)(ctx->res);
 161         free(ctx);
 162         __set_errno(save_errno);
 163 }
 164
 165 /*
 166  * This function takes a hesiod (name, type) and returns a DNS
 167  * name which is to be resolved.
 168  */
 169 char *
 170 hesiod_to_bind(void *context, const char *name, const char *type) {
 171         struct hesiod_p *ctx = (struct hesiod_p *) context;
 172         char *bindname;
 173         char **rhs_list = NULL;
 174         const char *RHS, *cp;
 175         char *endp;
 176
 177         /* Decide what our RHS is, and set cp to the end of the actual name. */
 178         if ((cp = strchr(name, '@')) != NULL) {
 179                 if (strchr(cp + 1, '.'))
 180                         RHS = cp + 1;
 181                 else if ((rhs_list = hesiod_resolve(context, cp + 1,
 182                     "rhs-extension")) != NULL)
 183                         RHS = *rhs_list;
 184                 else {
 185                         __set_errno(ENOENT);
 186                         return (NULL);
 187                 }
 188         } else {
 189                 RHS = ctx->RHS;
 190                 cp = name + strlen(name);
 191         }
 192
 193         /*
 194          * Allocate the space we need, including up to three periods and
 195          * the terminating NUL.
 196          */
 197         if ((bindname = malloc((cp - name) + strlen(type) + strlen(RHS) +
 198             (ctx->LHS ? strlen(ctx->LHS) : 0) + 4)) == NULL) {
 199                 if (rhs_list)
 200                         hesiod_free_list(context, rhs_list);
 201                 return NULL;
 202         }
 203
 204         /* Now put together the DNS name. */
 205         endp = (char *) __mempcpy (bindname, name, cp - name);
 206         *endp++ = '.';
 207         endp = (char *) __stpcpy (endp, type);
 208         if (ctx->LHS) {
 209                 if (ctx->LHS[0] != '.')
 210                         *endp++ = '.';
 211                 endp = __stpcpy (endp, ctx->LHS);
 212         }
 213         if (RHS[0] != '.')
 214                 *endp++ = '.';
 215         strcpy (endp, RHS);
 216
 217         if (rhs_list)
 218                 hesiod_free_list(context, rhs_list);
 219
 220         return (bindname);
 221 }
 222
 223 /*
 224  * This is the core function.  Given a hesiod (name, type), it
 225  * returns an array of strings returned by the resolver.
 226  */
 227 char **
 228 hesiod_resolve(void *context, const char *name, const char *type) {
 229         struct hesiod_p *ctx = (struct hesiod_p *) context;
 230         char *bindname = hesiod_to_bind(context, name, type);
 231         char **retvec;
 232
 233         if (bindname == NULL)
 234                 return (NULL);
 235         if (init(ctx) == -1) {
 236                 free(bindname);
 237                 return (NULL);
 238         }
 239
 240         retvec = get_txt_records(ctx, ctx->classes[0], bindname);
 241
 242         if (retvec == NULL && (errno == ENOENT || errno == ECONNREFUSED) && ctx->classes[1])
 243                 retvec = get_txt_records(ctx, ctx->classes[1], bindname);
 244
 245
 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 buf[MAXDNAME+7];
 265         FILE *fp;
 266
 267         /*
 268          * Clear the existing configuration variable, just in case
 269          * they're set.
 270          */
 271         free(ctx->RHS);
 272         free(ctx->LHS);
 273         ctx->RHS = ctx->LHS = 0;
 274         /* Set default query classes. */
 275         ctx->classes[0] = C_IN;
 276         ctx->classes[1] = C_HS;
 277
 278         /*
 279          * Now open and parse the file...
 280          */
 281         if (!(fp = fopen(filename, "rce")))
 282                 return (-1);
 283
 284         while (fgets(buf, sizeof(buf), fp) != NULL) {
 285                 char *key, *data, *cp, **cpp;
 286
 287                 cp = buf;
 288                 if (*cp == '#' || *cp == '\n' || *cp == '\r')
 289                         continue;
 290                 while(*cp == ' ' || *cp == '\t')
 291                         cp++;
 292                 key = cp;
 293                 while(*cp != ' ' && *cp != '\t' && *cp != '=')
 294                         cp++;
 295                 *cp++ = '\0';
 296
 297                 while(*cp == ' ' || *cp == '\t' || *cp == '=')
 298                         cp++;
 299                 data = cp;
 300                 while(*cp != ' ' && *cp != '\n' && *cp != '\r')
 301                         cp++;
 302                 *cp++ = '\0';
 303
 304                 cpp = NULL;
 305                 if (strcasecmp(key, "lhs") == 0)
 306                         cpp = &ctx->LHS;
 307                 else if (strcasecmp(key, "rhs") == 0)
 308                         cpp = &ctx->RHS;
 309                 if (cpp) {
 310                         *cpp = strdup(data);
 311                         if (!*cpp)
 312                                 goto cleanup;
 313                 } else if (strcasecmp(key, "classes") == 0) {
 314                         int n = 0;
 315                         while (*data && n < 2) {
 316                                 cp = strchrnul(data, ',');
 317                                 if (*cp != '\0')
 318                                         *cp++ = '\0';
 319                                 if (strcasecmp(data, "IN") == 0)
 320                                         ctx->classes[n++] = C_IN;
 321                                 else if (strcasecmp(data, "HS") == 0)
 322                                         ctx->classes[n++] = C_HS;
 323                                 data = cp;
 324                         }
 325                         if (n == 0) {
 326                                 /* Restore the default.  Better than
 327                                    nother at all.  */
 328                                 ctx->classes[0] = C_IN;
 329                                 ctx->classes[1] = C_HS;
 330                         } else if (n == 1
 331                                    || ctx->classes[0] == ctx->classes[1])
 332                                 ctx->classes[1] = 0;
 333                 }
 334         }
 335         fclose(fp);
 336         return (0);
 337
 338  cleanup:
 339         fclose(fp);
 340         free(ctx->RHS);
 341         free(ctx->LHS);
 342         ctx->RHS = ctx->LHS = 0;
 343         return (-1);
 344 }
 345
 346 /*
 347  * Given a DNS class and a DNS name, do a lookup for TXT records, and
 348  * return a list of them.
 349  */
 350 static char **
 351 get_txt_records(struct hesiod_p *ctx, int class, const char *name) {
 352         struct {
 353                 int type;               /* RR type */
 354                 int class;              /* RR class */
 355                 int dlen;               /* len of data section */
 356                 u_char *data;           /* pointer to data */
 357         } rr;
 358         HEADER *hp;
 359         u_char qbuf[MAX_HESRESP], abuf[MAX_HESRESP];
 360         u_char *cp, *erdata, *eom;
 361         char *dst, *edst, **list;
 362         int ancount, qdcount;
 363         int i, j, n, skip;
 364
 365         /*
 366          * Construct the query and send it.
 367          */
 368         n = res_nmkquery(ctx->res, QUERY, name, class, T_TXT, NULL, 0,
 369                          NULL, qbuf, MAX_HESRESP);
 370         if (n < 0) {
 371                 __set_errno(EMSGSIZE);
 372                 return (NULL);
 373         }
 374         n = res_nsend(ctx->res, qbuf, n, abuf, MAX_HESRESP);
 375         if (n < 0) {
 376                 __set_errno(ECONNREFUSED);
 377                 return (NULL);
 378         }
 379         if (n < HFIXEDSZ) {
 380                 __set_errno(EMSGSIZE);
 381                 return (NULL);
 382         }
 383
 384         /*
 385          * OK, parse the result.
 386          */
 387         hp = (HEADER *) abuf;
 388         ancount = ntohs(hp->ancount);
 389         qdcount = ntohs(hp->qdcount);
 390         cp = abuf + sizeof(HEADER);
 391         eom = abuf + n;
 392
 393         /* Skip query, trying to get to the answer section which follows. */
 394         for (i = 0; i < qdcount; i++) {
 395                 skip = dn_skipname(cp, eom);
 396                 if (skip < 0 || cp + skip + QFIXEDSZ > eom) {
 397                         __set_errno(EMSGSIZE);
 398                         return (NULL);
 399                 }
 400                 cp += skip + QFIXEDSZ;
 401         }
 402
 403         list = malloc((ancount + 1) * sizeof(char *));
 404         if (!list)
 405                 return (NULL);
 406         j = 0;
 407         for (i = 0; i < ancount; i++) {
 408                 skip = dn_skipname(cp, eom);
 409                 if (skip < 0) {
 410                         __set_errno(EMSGSIZE);
 411                         goto cleanup;
 412                 }
 413                 cp += skip;
 414                 if (cp + 3 * INT16SZ + INT32SZ > eom) {
 415                         __set_errno(EMSGSIZE);
 416                         goto cleanup;
 417                 }
 418                 rr.type = ns_get16(cp);
 419                 cp += INT16SZ;
 420                 rr.class = ns_get16(cp);
 421                 cp += INT16SZ + INT32SZ;        /* skip the ttl, too */
 422                 rr.dlen = ns_get16(cp);
 423                 cp += INT16SZ;
 424                 if (cp + rr.dlen > eom) {
 425                         __set_errno(EMSGSIZE);
 426                         goto cleanup;
 427                 }
 428                 rr.data = cp;
 429                 cp += rr.dlen;
 430                 if (rr.class != class || rr.type != T_TXT)
 431                         continue;
 432                 if (!(list[j] = malloc(rr.dlen)))
 433                         goto cleanup;
 434                 dst = list[j++];
 435                 edst = dst + rr.dlen;
 436                 erdata = rr.data + rr.dlen;
 437                 cp = rr.data;
 438                 while (cp < erdata) {
 439                         n = (unsigned char) *cp++;
 440                         if (cp + n > eom || dst + n > edst) {
 441                                 __set_errno(EMSGSIZE);
 442                                 goto cleanup;
 443                         }
 444                         memcpy(dst, cp, n);
 445                         cp += n;
 446                         dst += n;
 447                 }
 448                 if (cp != erdata) {
 449                         __set_errno(EMSGSIZE);
 450                         goto cleanup;
 451                 }
 452                 *dst = '\0';
 453         }
 454         list[j] = NULL;
 455         if (j == 0) {
 456                 __set_errno(ENOENT);
 457                 goto cleanup;
 458         }
 459         return (list);
 460
 461  cleanup:
 462         for (i = 0; i < j; i++)
 463                 free(list[i]);
 464         free(list);
 465         return (NULL);
 466 }
 467
 468 struct __res_state *
 469 __hesiod_res_get(void *context) {
 470         struct hesiod_p *ctx = context;
 471
 472         if (!ctx->res) {
 473                 struct __res_state *res;
 474                 res = (struct __res_state *)calloc(1, sizeof *res);
 475                 if (res == NULL)
 476                         return (NULL);
 477                 __hesiod_res_set(ctx, res, free);
 478         }
 479
 480         return (ctx->res);
 481 }
 482
 483 void
 484 __hesiod_res_set(void *context, struct __res_state *res,
 485                  void (*free_res)(void *)) {
 486         struct hesiod_p *ctx = context;
 487
 488         if (ctx->res && ctx->free_res) {
 489                 res_nclose(ctx->res);
 490                 (*ctx->free_res)(ctx->res);
 491         }
 492
 493         ctx->res = res;
 494         ctx->free_res = free_res;
 495 }
 496
 497 static int
 498 init(struct hesiod_p *ctx) {
 499
 500         if (!ctx->res && !__hesiod_res_get(ctx))
 501                 return (-1);
 502
 503         if (__res_maybe_init (ctx->res, 0) == -1)
 504                 return (-1);
 505
 506         return (0);
 507 }