glibc/hesiod/hesiod.c
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2018-01-01 00:32:25 +00:00

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C

/* Copyright (C) 1997-2018 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
/*
* Copyright (c) 1996,1999 by Internet Software Consortium.
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM DISCLAIMS
* ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
* CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
* DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
* PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
* ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
* SOFTWARE.
*/
/*
* This file is primarily maintained by <tytso@mit.edu> and <ghudson@mit.edu>.
*/
/*
* hesiod.c --- the core portion of the hesiod resolver.
*
* This file is derived from the hesiod library from Project Athena;
* It has been extensively rewritten by Theodore Ts'o to have a more
* thread-safe interface.
*/
/* Imports */
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/nameser.h>
#include <errno.h>
#include <netdb.h>
#include <resolv.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "hesiod.h"
#include "hesiod_p.h"
#define _PATH_HESIOD_CONF "/etc/hesiod.conf"
/* Forward */
static int parse_config_file(struct hesiod_p *ctx, const char *filename);
static char ** get_txt_records(struct hesiod_p *ctx, int class,
const char *name);
/* Public */
/*
* This function is called to initialize a hesiod_p.
*/
int
hesiod_init(void **context) {
struct hesiod_p *ctx;
const char *configname;
char *cp;
ctx = malloc(sizeof(struct hesiod_p));
if (ctx == 0)
return (-1);
ctx->LHS = NULL;
ctx->RHS = NULL;
/* Set default query classes. */
ctx->classes[0] = C_IN;
ctx->classes[1] = C_HS;
configname = __libc_secure_getenv("HESIOD_CONFIG");
if (!configname)
configname = _PATH_HESIOD_CONF;
if (parse_config_file(ctx, configname) < 0) {
goto cleanup;
}
/*
* The default RHS can be overridden by an environment
* variable.
*/
if ((cp = __libc_secure_getenv("HES_DOMAIN")) != NULL) {
free(ctx->RHS);
ctx->RHS = malloc(strlen(cp)+2);
if (!ctx->RHS)
goto cleanup;
if (cp[0] == '.')
strcpy(ctx->RHS, cp);
else {
ctx->RHS[0] = '.';
strcpy(ctx->RHS + 1, cp);
}
}
/*
* If there is no default hesiod realm set, we return an
* error.
*/
if (!ctx->RHS) {
__set_errno(ENOEXEC);
goto cleanup;
}
*context = ctx;
return (0);
cleanup:
hesiod_end(ctx);
return (-1);
}
/*
* This function deallocates the hesiod_p
*/
void
hesiod_end(void *context) {
struct hesiod_p *ctx = (struct hesiod_p *) context;
int save_errno = errno;
free(ctx->RHS);
free(ctx->LHS);
free(ctx);
__set_errno(save_errno);
}
/*
* This function takes a hesiod (name, type) and returns a DNS
* name which is to be resolved.
*/
char *
hesiod_to_bind(void *context, const char *name, const char *type) {
struct hesiod_p *ctx = (struct hesiod_p *) context;
char *bindname;
char **rhs_list = NULL;
const char *RHS, *cp;
char *endp;
/* Decide what our RHS is, and set cp to the end of the actual name. */
if ((cp = strchr(name, '@')) != NULL) {
if (strchr(cp + 1, '.'))
RHS = cp + 1;
else if ((rhs_list = hesiod_resolve(context, cp + 1,
"rhs-extension")) != NULL)
RHS = *rhs_list;
else {
__set_errno(ENOENT);
return (NULL);
}
} else {
RHS = ctx->RHS;
cp = name + strlen(name);
}
/*
* Allocate the space we need, including up to three periods and
* the terminating NUL.
*/
if ((bindname = malloc((cp - name) + strlen(type) + strlen(RHS) +
(ctx->LHS ? strlen(ctx->LHS) : 0) + 4)) == NULL) {
if (rhs_list)
hesiod_free_list(context, rhs_list);
return NULL;
}
/* Now put together the DNS name. */
endp = (char *) __mempcpy (bindname, name, cp - name);
*endp++ = '.';
endp = (char *) __stpcpy (endp, type);
if (ctx->LHS) {
if (ctx->LHS[0] != '.')
*endp++ = '.';
endp = __stpcpy (endp, ctx->LHS);
}
if (RHS[0] != '.')
*endp++ = '.';
strcpy (endp, RHS);
if (rhs_list)
hesiod_free_list(context, rhs_list);
return (bindname);
}
/*
* This is the core function. Given a hesiod (name, type), it
* returns an array of strings returned by the resolver.
*/
char **
hesiod_resolve(void *context, const char *name, const char *type) {
struct hesiod_p *ctx = (struct hesiod_p *) context;
char *bindname = hesiod_to_bind(context, name, type);
char **retvec;
if (bindname == NULL)
return (NULL);
retvec = get_txt_records(ctx, ctx->classes[0], bindname);
if (retvec == NULL && (errno == ENOENT || errno == ECONNREFUSED) && ctx->classes[1])
retvec = get_txt_records(ctx, ctx->classes[1], bindname);
free(bindname);
return (retvec);
}
void
hesiod_free_list(void *context, char **list) {
char **p;
for (p = list; *p; p++)
free(*p);
free(list);
}
/*
* This function parses the /etc/hesiod.conf file
*/
static int
parse_config_file(struct hesiod_p *ctx, const char *filename) {
char buf[MAXDNAME+7];
FILE *fp;
/*
* Clear the existing configuration variable, just in case
* they're set.
*/
free(ctx->RHS);
free(ctx->LHS);
ctx->RHS = ctx->LHS = 0;
/* Set default query classes. */
ctx->classes[0] = C_IN;
ctx->classes[1] = C_HS;
/*
* Now open and parse the file...
*/
if (!(fp = fopen(filename, "rce")))
return (-1);
while (fgets(buf, sizeof(buf), fp) != NULL) {
char *key, *data, *cp, **cpp;
cp = buf;
if (*cp == '#' || *cp == '\n' || *cp == '\r')
continue;
while(*cp == ' ' || *cp == '\t')
cp++;
key = cp;
while(*cp != ' ' && *cp != '\t' && *cp != '=')
cp++;
*cp++ = '\0';
while(*cp == ' ' || *cp == '\t' || *cp == '=')
cp++;
data = cp;
while(*cp != ' ' && *cp != '\n' && *cp != '\r')
cp++;
*cp++ = '\0';
cpp = NULL;
if (strcasecmp(key, "lhs") == 0)
cpp = &ctx->LHS;
else if (strcasecmp(key, "rhs") == 0)
cpp = &ctx->RHS;
if (cpp) {
*cpp = strdup(data);
if (!*cpp)
goto cleanup;
} else if (strcasecmp(key, "classes") == 0) {
int n = 0;
while (*data && n < 2) {
cp = strchrnul(data, ',');
if (*cp != '\0')
*cp++ = '\0';
if (strcasecmp(data, "IN") == 0)
ctx->classes[n++] = C_IN;
else if (strcasecmp(data, "HS") == 0)
ctx->classes[n++] = C_HS;
data = cp;
}
if (n == 0) {
/* Restore the default. Better than
nother at all. */
ctx->classes[0] = C_IN;
ctx->classes[1] = C_HS;
} else if (n == 1
|| ctx->classes[0] == ctx->classes[1])
ctx->classes[1] = 0;
}
}
fclose(fp);
return (0);
cleanup:
fclose(fp);
free(ctx->RHS);
free(ctx->LHS);
ctx->RHS = ctx->LHS = 0;
return (-1);
}
/*
* Given a DNS class and a DNS name, do a lookup for TXT records, and
* return a list of them.
*/
static char **
get_txt_records(struct hesiod_p *ctx, int class, const char *name) {
struct {
int type; /* RR type */
int class; /* RR class */
int dlen; /* len of data section */
u_char *data; /* pointer to data */
} rr;
HEADER *hp;
u_char qbuf[MAX_HESRESP], abuf[MAX_HESRESP];
u_char *cp, *erdata, *eom;
char *dst, *edst, **list;
int ancount, qdcount;
int i, j, n, skip;
/*
* Construct the query and send it.
*/
n = res_mkquery(QUERY, name, class, T_TXT, NULL, 0,
NULL, qbuf, MAX_HESRESP);
if (n < 0) {
__set_errno(EMSGSIZE);
return (NULL);
}
n = res_send(qbuf, n, abuf, MAX_HESRESP);
if (n < 0) {
__set_errno(ECONNREFUSED);
return (NULL);
}
if (n < HFIXEDSZ) {
__set_errno(EMSGSIZE);
return (NULL);
}
/*
* OK, parse the result.
*/
hp = (HEADER *) abuf;
ancount = ntohs(hp->ancount);
qdcount = ntohs(hp->qdcount);
cp = abuf + sizeof(HEADER);
eom = abuf + n;
/* Skip query, trying to get to the answer section which follows. */
for (i = 0; i < qdcount; i++) {
skip = dn_skipname(cp, eom);
if (skip < 0 || cp + skip + QFIXEDSZ > eom) {
__set_errno(EMSGSIZE);
return (NULL);
}
cp += skip + QFIXEDSZ;
}
list = malloc((ancount + 1) * sizeof(char *));
if (!list)
return (NULL);
j = 0;
for (i = 0; i < ancount; i++) {
skip = dn_skipname(cp, eom);
if (skip < 0) {
__set_errno(EMSGSIZE);
goto cleanup;
}
cp += skip;
if (cp + 3 * INT16SZ + INT32SZ > eom) {
__set_errno(EMSGSIZE);
goto cleanup;
}
rr.type = ns_get16(cp);
cp += INT16SZ;
rr.class = ns_get16(cp);
cp += INT16SZ + INT32SZ; /* skip the ttl, too */
rr.dlen = ns_get16(cp);
cp += INT16SZ;
if (rr.dlen == 0 || cp + rr.dlen > eom) {
__set_errno(EMSGSIZE);
goto cleanup;
}
rr.data = cp;
cp += rr.dlen;
if (rr.class != class || rr.type != T_TXT)
continue;
if (!(list[j] = malloc(rr.dlen)))
goto cleanup;
dst = list[j++];
edst = dst + rr.dlen;
erdata = rr.data + rr.dlen;
cp = rr.data;
while (cp < erdata) {
n = (unsigned char) *cp++;
if (cp + n > eom || dst + n > edst) {
__set_errno(EMSGSIZE);
goto cleanup;
}
memcpy(dst, cp, n);
cp += n;
dst += n;
}
if (cp != erdata) {
__set_errno(EMSGSIZE);
goto cleanup;
}
*dst = '\0';
}
list[j] = NULL;
if (j == 0) {
__set_errno(ENOENT);
goto cleanup;
}
return (list);
cleanup:
for (i = 0; i < j; i++)
free(list[i]);
free(list);
return (NULL);
}