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glibc/hesiod/hesiod.c

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/* Copyright (c) 1996 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.
*/
/* Copyright 1996 by the Massachusetts Institute of Technology.
*
* Permission to use, copy, modify, and distribute this
* software and its documentation for any purpose and without
* fee is hereby granted, provided that the above copyright
* notice appear in all copies and that both that copyright
* notice and this permission notice appear in supporting
* documentation, and that the name of M.I.T. not be used in
* advertising or publicity pertaining to distribution of the
* software without specific, written prior permission.
* M.I.T. makes no representations about the suitability of
* this software for any purpose. It is provided "as is"
* without express or implied warranty.
*/
/* This file is part of the hesiod library. It implements the core
* portion of the hesiod resolver.
*
* This file is loosely based on an interim version of hesiod.c from
* the BIND IRS library, which was in turn based on an earlier version
* of this file. Extensive changes have been made on each step of the
* path.
*
* This implementation is not truly thread-safe at the moment because
* it uses res_send() and accesses _res.
*/
static const char rcsid[] = "$Id$";
#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 <ctype.h>
#include "hesiod.h"
#include "hesiod_p.h"
/* A few operating systems don't define these. */
#ifndef C_HS
#define C_HS 4
#endif
#ifndef T_TXT
#define T_TXT 16
#endif
static int read_config_file(struct hesiod_p *ctx, const char *filename);
static char **get_txt_records(struct hesiod_p *ctx, int class,
const char *name);
static int cistrcmp(const char *s1, const char *s2);
/* This function is called to initialize a hesiod_p. */
int hesiod_init(void **context)
{
struct hesiod_p *ctx;
const char *p, *configname;
ctx = malloc(sizeof(struct hesiod_p));
if (ctx)
{
*context = ctx;
configname = __secure_getenv("HESIOD_CONFIG");
if (!configname)
configname = SYSCONFDIR "/hesiod.conf";
if (read_config_file(ctx, configname) >= 0)
{
/* The default rhs can be overridden by an environment variable. */
p = __secure_getenv("HES_DOMAIN");
if (p)
{
if (ctx->rhs)
free(ctx->rhs);
ctx->rhs = malloc(strlen(p) + 2);
if (ctx->rhs)
{
*ctx->rhs = '.';
strcpy(ctx->rhs + 1, (*p == '.') ? p + 1 : p);
return 0;
}
else
__set_errno (ENOMEM);
}
else
return 0;
}
}
else
__set_errno (ENOMEM);
if (ctx->lhs)
free(ctx->lhs);
if (ctx->rhs)
free(ctx->rhs);
if (ctx)
free(ctx);
return -1;
}
/* This function deallocates the hesiod_p. */
void hesiod_end(void *context)
{
struct hesiod_p *ctx = (struct hesiod_p *) context;
free(ctx->rhs);
if (ctx->lhs)
free(ctx->lhs);
free(ctx);
}
/* 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[MAXDNAME], *p, *ret, **rhs_list = NULL;
const char *rhs;
int len;
strcpy(bindname, name);
/* Find the right right hand side to use, possibly truncating bindname. */
p = strchr(bindname, '@');
if (p)
{
*p++ = 0;
if (strchr(p, '.'))
rhs = name + (p - bindname);
else
{
rhs_list = hesiod_resolve(context, p, "rhs-extension");
if (rhs_list)
rhs = *rhs_list;
else
{
__set_errno (ENOENT);
return NULL;
}
}
} else
rhs = ctx->rhs;
/* See if we have enough room. */
len = strlen(bindname) + 1 + strlen(type);
if (ctx->lhs)
len += strlen(ctx->lhs) + ((ctx->lhs[0] != '.') ? 1 : 0);
len += strlen(rhs) + ((rhs[0] != '.') ? 1 : 0);
if (len > sizeof(bindname) - 1)
{
if (rhs_list)
hesiod_free_list(context, rhs_list);
__set_errno (EMSGSIZE);
return NULL;
}
/* Put together the rest of the domain. */
strcat(bindname, ".");
strcat(bindname, type);
if (ctx->lhs)
{
if (ctx->lhs[0] != '.')
strcat(bindname, ".");
strcat(bindname, ctx->lhs);
}
if (rhs[0] != '.')
strcat(bindname, ".");
strcat(bindname, rhs);
/* rhs_list is no longer needed, since we're done with rhs. */
if (rhs_list)
hesiod_free_list(context, rhs_list);
/* Make a copy of the result and return it to the caller. */
ret = malloc(strlen(bindname) + 1);
if (!ret)
{
__set_errno (ENOMEM);
return NULL;
}
strcpy(ret, bindname);
return ret;
}
/* This is the core function. Given a hesiod name and 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, **retvec;
bindname = hesiod_to_bind(context, name, type);
if (!bindname)
return NULL;
retvec = get_txt_records(ctx, ctx->classes[0], bindname);
if (retvec == NULL && errno == ENOENT && 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. Returns 0 on success,
* -1 on failure. On failure, it might leave values in ctx->lhs or
* ctx->rhs which need to be freed by the caller. */
static int read_config_file(struct hesiod_p *ctx, const char *filename)
{
char *key, *data, *p, **which;
char buf[MAXDNAME + 7];
int n;
FILE *fp;
/* Set default query classes. */
ctx->classes[0] = C_IN;
ctx->classes[1] = C_HS;
/* Try to open the configuration file. */
fp = fopen(filename, "r");
if (!fp)
{
/* Use compiled in default domain names. */
ctx->lhs = malloc(strlen(DEF_LHS) + 1);
ctx->rhs = malloc(strlen(DEF_RHS) + 1);
if (ctx->lhs && ctx->rhs)
{
strcpy(ctx->lhs, DEF_LHS);
strcpy(ctx->rhs, DEF_RHS);
return 0;
}
else
{
__set_errno (ENOMEM);
return -1;
}
}
ctx->lhs = NULL;
ctx->rhs = NULL;
while (fgets(buf, sizeof(buf), fp) != NULL)
{
p = buf;
if (*p == '#' || *p == '\n' || *p == '\r')
continue;
while(*p == ' ' || *p == '\t')
p++;
key = p;
while(*p != ' ' && *p != '\t' && *p != '=')
p++;
*p++ = 0;
while(isspace(*p) || *p == '=')
p++;
data = p;
while(!isspace(*p))
p++;
*p = 0;
if (cistrcmp(key, "lhs") == 0 || cistrcmp(key, "rhs") == 0)
{
which = (strcmp(key, "lhs") == 0) ? &ctx->lhs : &ctx->rhs;
*which = malloc(strlen(data) + 1);
if (!*which)
{
__set_errno (ENOMEM);
return -1;
}
strcpy(*which, data);
}
else if (cistrcmp(key, "classes") == 0)
{
n = 0;
while (*data && n < 2)
{
p = data;
while (*p && *p != ',')
p++;
if (*p)
*p++ = 0;
if (cistrcmp(data, "IN") == 0)
ctx->classes[n++] = C_IN;
else if (cistrcmp(data, "HS") == 0)
ctx->classes[n++] = C_HS;
data = p;
}
while (n < 2)
ctx->classes[n++] = 0;
}
}
fclose(fp);
if (!ctx->rhs || ctx->classes[0] == 0 || ctx->classes[0] == ctx->classes[1])
{
__set_errno (ENOEXEC);
return -1;
}
return 0;
}
/* 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 qclass,
const char *name)
{
HEADER *hp;
unsigned char qbuf[PACKETSZ], abuf[MAX_HESRESP], *p, *eom, *eor;
char *dst, **list;
int ancount, qdcount, i, j, n, skip, type, class, len;
/* Make sure the resolver is initialized. */
if ((_res.options & RES_INIT) == 0 && res_init() == -1)
return NULL;
/* Construct the query. */
n = res_mkquery(QUERY, name, qclass, T_TXT, NULL, 0,
NULL, qbuf, PACKETSZ);
if (n < 0)
return NULL;
/* Send the query. */
n = res_send(qbuf, n, abuf, MAX_HESRESP);
if (n < 0)
{
__set_errno (ECONNREFUSED);
return NULL;
}
/* Parse the header of the result. */
hp = (HEADER *) abuf;
ancount = ntohs(hp->ancount);
qdcount = ntohs(hp->qdcount);
p = abuf + sizeof(HEADER);
eom = abuf + n;
/* Skip questions, trying to get to the answer section which follows. */
for (i = 0; i < qdcount; i++)
{
skip = dn_skipname(p, eom);
if (skip < 0 || p + skip + QFIXEDSZ > eom)
{
__set_errno (EMSGSIZE);
return NULL;
}
p += skip + QFIXEDSZ;
}
/* Allocate space for the text record answers. */
list = malloc((ancount + 1) * sizeof(char *));
if (!list)
{
__set_errno (ENOMEM);
return NULL;
}
/* Parse the answers. */
j = 0;
for (i = 0; i < ancount; i++)
{
/* Parse the header of this answer. */
skip = dn_skipname(p, eom);
if (skip < 0 || p + skip + 10 > eom)
break;
type = p[skip + 0] << 8 | p[skip + 1];
class = p[skip + 2] << 8 | p[skip + 3];
len = p[skip + 8] << 8 | p[skip + 9];
p += skip + 10;
if (p + len > eom)
{
__set_errno (EMSGSIZE);
break;
}
/* Skip entries of the wrong class and type. */
if (class != qclass || type != T_TXT)
{
p += len;
continue;
}
/* Allocate space for this answer. */
list[j] = malloc(len);
if (!list[j])
{
__set_errno (ENOMEM);
break;
}
dst = list[j++];
/* Copy answer data into the allocated area. */
eor = p + len;
while (p < eor)
{
n = (unsigned char) *p++;
if (p + n > eor)
{
__set_errno (EMSGSIZE);
break;
}
memcpy(dst, p, n);
p += n;
dst += n;
}
if (p < eor)
{
__set_errno (EMSGSIZE);
break;
}
*dst = 0;
}
/* If we didn't terminate the loop normally, something went wrong. */
if (i < ancount)
{
for (i = 0; i < j; i++)
free(list[i]);
free(list);
return NULL;
}
if (j == 0)
{
__set_errno (ENOENT);
free(list);
return NULL;
}
list[j] = NULL;
return list;
}
static int cistrcmp(const char *s1, const char *s2)
{
while (*s1 && tolower(*s1) == tolower(*s2))
{
s1++;
s2++;
}
return tolower(*s1) - tolower(*s2);
}
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