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NetBSD/lib/libresolv/ns_verify.c

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/* $NetBSD: ns_verify.c,v 1.4 2022/04/19 20:32:17 rillig Exp $ */
/*
* Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
* Copyright (c) 1999 by Internet Software Consortium, Inc.
*
* 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 ISC DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC 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.
*/
#include <sys/cdefs.h>
__RCSID("Id: ns_verify.c,v 1.5 2006/03/09 23:57:56 marka Exp ");
/* Import. */
#include "port_before.h"
#include "fd_setsize.h"
#include <sys/types.h>
#include <sys/param.h>
#include <netinet/in.h>
#include <arpa/nameser.h>
#include <arpa/inet.h>
#include <errno.h>
#include <netdb.h>
#include <resolv.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <isc/dst.h>
#include "port_after.h"
/* Private. */
#define BOUNDS_CHECK(ptr, count) \
do { \
if ((ptr) + (count) > eom) { \
return (NS_TSIG_ERROR_FORMERR); \
} \
} while (0)
/* Public. */
u_char *
ns_find_tsig(u_char *msg, u_char *eom) {
HEADER *hp = (void *)msg;
int n, type;
u_char *cp = msg, *start;
if (msg == NULL || eom == NULL || msg > eom)
return (NULL);
if (cp + HFIXEDSZ >= eom)
return (NULL);
if (hp->arcount == 0)
return (NULL);
cp += HFIXEDSZ;
n = ns_skiprr(cp, eom, ns_s_qd, ntohs(hp->qdcount));
if (n < 0)
return (NULL);
cp += n;
n = ns_skiprr(cp, eom, ns_s_an, ntohs(hp->ancount));
if (n < 0)
return (NULL);
cp += n;
n = ns_skiprr(cp, eom, ns_s_ns, ntohs(hp->nscount));
if (n < 0)
return (NULL);
cp += n;
n = ns_skiprr(cp, eom, ns_s_ar, ntohs(hp->arcount) - 1);
if (n < 0)
return (NULL);
cp += n;
start = cp;
n = dn_skipname(cp, eom);
if (n < 0)
return (NULL);
cp += n;
if (cp + INT16SZ >= eom)
return (NULL);
GETSHORT(type, cp);
if (type != ns_t_tsig)
return (NULL);
return (start);
}
/* ns_verify
*
* Parameters:
*\li statp res stuff
*\li msg received message
*\li msglen length of message
*\li key tsig key used for verifying.
*\li querysig (response), the signature in the query
*\li querysiglen (response), the length of the signature in the query
*\li sig (query), a buffer to hold the signature
*\li siglen (query), input - length of signature buffer
* output - length of signature
*
* Errors:
*\li - bad input (-1)
*\li - invalid dns message (NS_TSIG_ERROR_FORMERR)
*\li - TSIG is not present (NS_TSIG_ERROR_NO_TSIG)
*\li - key doesn't match (-ns_r_badkey)
*\li - TSIG verification fails with BADKEY (-ns_r_badkey)
*\li - TSIG verification fails with BADSIG (-ns_r_badsig)
*\li - TSIG verification fails with BADTIME (-ns_r_badtime)
*\li - TSIG verification succeeds, error set to BAKEY (ns_r_badkey)
*\li - TSIG verification succeeds, error set to BADSIG (ns_r_badsig)
*\li - TSIG verification succeeds, error set to BADTIME (ns_r_badtime)
*/
int
ns_verify(u_char *msg, int *msglen, void *k,
const u_char *querysig, int querysiglen, u_char *sig, int *siglen,
time_t *timesigned, int nostrip)
{
HEADER *hp = (void *)msg;
DST_KEY *key = (DST_KEY *)k;
u_char *cp = msg, *eom;
char name[MAXDNAME], alg[MAXDNAME];
u_char *recstart, *rdatastart;
u_char *sigstart, *otherstart;
int n;
int error;
u_int16_t type, length;
u_int16_t fudge, sigfieldlen, otherfieldlen;
dst_init();
if (msg == NULL || msglen == NULL || *msglen < 0)
return (-1);
eom = msg + *msglen;
recstart = ns_find_tsig(msg, eom);
if (recstart == NULL)
return (NS_TSIG_ERROR_NO_TSIG);
cp = recstart;
/* Read the key name. */
n = dn_expand(msg, eom, cp, name, MAXDNAME);
if (n < 0)
return (NS_TSIG_ERROR_FORMERR);
cp += n;
/* Read the type. */
BOUNDS_CHECK(cp, 2*INT16SZ + INT32SZ + INT16SZ);
GETSHORT(type, cp);
if (type != ns_t_tsig)
return (NS_TSIG_ERROR_NO_TSIG);
/* Skip the class and TTL, save the length. */
cp += INT16SZ + INT32SZ;
GETSHORT(length, cp);
if (eom - cp != length)
return (NS_TSIG_ERROR_FORMERR);
/* Read the algorithm name. */
rdatastart = cp;
n = dn_expand(msg, eom, cp, alg, MAXDNAME);
if (n < 0)
return (NS_TSIG_ERROR_FORMERR);
if (ns_samename(alg, NS_TSIG_ALG_HMAC_MD5) != 1)
return (-ns_r_badkey);
cp += n;
/* Read the time signed and fudge. */
BOUNDS_CHECK(cp, INT16SZ + INT32SZ + INT16SZ);
cp += INT16SZ;
GETLONG((*timesigned), cp);
GETSHORT(fudge, cp);
/* Read the signature. */
BOUNDS_CHECK(cp, INT16SZ);
GETSHORT(sigfieldlen, cp);
BOUNDS_CHECK(cp, sigfieldlen);
sigstart = cp;
cp += sigfieldlen;
/* Skip id and read error. */
BOUNDS_CHECK(cp, 2*INT16SZ);
cp += INT16SZ;
GETSHORT(error, cp);
/* Parse the other data. */
BOUNDS_CHECK(cp, INT16SZ);
GETSHORT(otherfieldlen, cp);
BOUNDS_CHECK(cp, otherfieldlen);
otherstart = cp;
cp += otherfieldlen;
if (cp != eom)
return (NS_TSIG_ERROR_FORMERR);
/* Verify that the key used is OK. */
if (key != NULL) {
if (key->dk_alg != KEY_HMAC_MD5)
return (-ns_r_badkey);
if (error != ns_r_badsig && error != ns_r_badkey) {
if (ns_samename(key->dk_key_name, name) != 1)
return (-ns_r_badkey);
}
}
hp->arcount = htons(ntohs(hp->arcount) - 1);
/*
* Do the verification.
*/
if (key != NULL && error != ns_r_badsig && error != ns_r_badkey) {
void *ctx;
u_char buf[MAXDNAME];
u_char buf2[MAXDNAME];
/* Digest the query signature, if this is a response. */
dst_verify_data(SIG_MODE_INIT, key, &ctx, NULL, 0, NULL, 0);
if (querysiglen > 0 && querysig != NULL) {
u_int16_t len_n = htons(querysiglen);
dst_verify_data(SIG_MODE_UPDATE, key, &ctx,
(void *)&len_n, INT16SZ, NULL, 0);
dst_verify_data(SIG_MODE_UPDATE, key, &ctx,
querysig, querysiglen, NULL, 0);
}
/* Digest the message. */
dst_verify_data(SIG_MODE_UPDATE, key, &ctx, msg,
(int)(recstart - msg), NULL, 0);
/* Digest the key name. */
n = ns_name_pton(name, buf2, sizeof(buf2));
if (n < 0)
return (-1);
n = ns_name_ntol(buf2, buf, sizeof(buf));
if (n < 0)
return (-1);
dst_verify_data(SIG_MODE_UPDATE, key, &ctx, buf, n, NULL, 0);
/* Digest the class and TTL. */
dst_verify_data(SIG_MODE_UPDATE, key, &ctx,
recstart + dn_skipname(recstart, eom) + INT16SZ,
INT16SZ + INT32SZ, NULL, 0);
/* Digest the algorithm. */
n = ns_name_pton(alg, buf2, sizeof(buf2));
if (n < 0)
return (-1);
n = ns_name_ntol(buf2, buf, sizeof(buf));
if (n < 0)
return (-1);
dst_verify_data(SIG_MODE_UPDATE, key, &ctx, buf, n, NULL, 0);
/* Digest the time signed and fudge. */
dst_verify_data(SIG_MODE_UPDATE, key, &ctx,
rdatastart + dn_skipname(rdatastart, eom),
INT16SZ + INT32SZ + INT16SZ, NULL, 0);
/* Digest the error and other data. */
dst_verify_data(SIG_MODE_UPDATE, key, &ctx,
otherstart - INT16SZ - INT16SZ,
otherfieldlen + INT16SZ + INT16SZ, NULL, 0);
n = dst_verify_data(SIG_MODE_FINAL, key, &ctx, NULL, 0,
sigstart, sigfieldlen);
if (n < 0)
return (-ns_r_badsig);
if (sig != NULL && siglen != NULL) {
if (*siglen < sigfieldlen)
return (NS_TSIG_ERROR_NO_SPACE);
memcpy(sig, sigstart, sigfieldlen);
*siglen = sigfieldlen;
}
} else {
if (sigfieldlen > 0)
return (NS_TSIG_ERROR_FORMERR);
if (sig != NULL && siglen != NULL)
*siglen = 0;
}
/* Reset the counter, since we still need to check for badtime. */
hp->arcount = htons(ntohs(hp->arcount) + 1);
/* Verify the time. */
if (abs((int)((*timesigned) - time(NULL))) > fudge)
return (-ns_r_badtime);
if (nostrip == 0) {
*msglen = (int)(recstart - msg);
hp->arcount = htons(ntohs(hp->arcount) - 1);
}
if (error != NOERROR)
return (error);
return (0);
}
int
ns_verify_tcp_init(void *k, const u_char *querysig, int querysiglen,
ns_tcp_tsig_state *state)
{
dst_init();
if (state == NULL || k == NULL || querysig == NULL || querysiglen < 0)
return (-1);
state->counter = -1;
state->key = k;
if (state->key->dk_alg != KEY_HMAC_MD5)
return (-ns_r_badkey);
if (querysiglen > (int)sizeof(state->sig))
return (-1);
memcpy(state->sig, querysig, querysiglen);
state->siglen = querysiglen;
return (0);
}
int
ns_verify_tcp(u_char *msg, int *msglen, ns_tcp_tsig_state *state,
int required)
{
HEADER *hp = (void *)msg;
u_char *recstart, *sigstart;
unsigned int sigfieldlen, otherfieldlen;
u_char *cp, *eom, *cp2;
char name[MAXDNAME], alg[MAXDNAME];
u_char buf[MAXDNAME];
int n, type, length, fudge, error;
time_t timesigned;
if (msg == NULL || msglen == NULL || state == NULL)
return (-1);
eom = msg + *msglen;
state->counter++;
if (state->counter == 0)
return (ns_verify(msg, msglen, state->key,
state->sig, state->siglen,
state->sig, &state->siglen, &timesigned, 0));
if (state->siglen > 0) {
u_int16_t siglen_n = htons(state->siglen);
dst_verify_data(SIG_MODE_INIT, state->key, &state->ctx,
NULL, 0, NULL, 0);
dst_verify_data(SIG_MODE_UPDATE, state->key, &state->ctx,
(void *)&siglen_n, INT16SZ, NULL, 0);
dst_verify_data(SIG_MODE_UPDATE, state->key, &state->ctx,
state->sig, state->siglen, NULL, 0);
state->siglen = 0;
}
cp = recstart = ns_find_tsig(msg, eom);
if (recstart == NULL) {
if (required)
return (NS_TSIG_ERROR_NO_TSIG);
dst_verify_data(SIG_MODE_UPDATE, state->key, &state->ctx,
msg, *msglen, NULL, 0);
return (0);
}
hp->arcount = htons(ntohs(hp->arcount) - 1);
dst_verify_data(SIG_MODE_UPDATE, state->key, &state->ctx,
msg, (int)(recstart - msg), NULL, 0);
/* Read the key name. */
n = dn_expand(msg, eom, cp, name, MAXDNAME);
if (n < 0)
return (NS_TSIG_ERROR_FORMERR);
cp += n;
/* Read the type. */
BOUNDS_CHECK(cp, 2*INT16SZ + INT32SZ + INT16SZ);
GETSHORT(type, cp);
if (type != ns_t_tsig)
return (NS_TSIG_ERROR_NO_TSIG);
/* Skip the class and TTL, save the length. */
cp += INT16SZ + INT32SZ;
GETSHORT(length, cp);
if (eom - cp != length)
return (NS_TSIG_ERROR_FORMERR);
/* Read the algorithm name. */
n = dn_expand(msg, eom, cp, alg, MAXDNAME);
if (n < 0)
return (NS_TSIG_ERROR_FORMERR);
if (ns_samename(alg, NS_TSIG_ALG_HMAC_MD5) != 1)
return (-ns_r_badkey);
cp += n;
/* Verify that the key used is OK. */
if ((ns_samename(state->key->dk_key_name, name) != 1 ||
state->key->dk_alg != KEY_HMAC_MD5))
return (-ns_r_badkey);
/* Read the time signed and fudge. */
BOUNDS_CHECK(cp, INT16SZ + INT32SZ + INT16SZ);
cp += INT16SZ;
GETLONG(timesigned, cp);
GETSHORT(fudge, cp);
/* Read the signature. */
BOUNDS_CHECK(cp, INT16SZ);
GETSHORT(sigfieldlen, cp);
BOUNDS_CHECK(cp, sigfieldlen);
sigstart = cp;
cp += sigfieldlen;
/* Skip id and read error. */
BOUNDS_CHECK(cp, 2*INT16SZ);
cp += INT16SZ;
GETSHORT(error, cp);
/* Parse the other data. */
BOUNDS_CHECK(cp, INT16SZ);
GETSHORT(otherfieldlen, cp);
BOUNDS_CHECK(cp, otherfieldlen);
cp += otherfieldlen;
if (cp != eom)
return (NS_TSIG_ERROR_FORMERR);
/*
* Do the verification.
*/
/* Digest the time signed and fudge. */
cp2 = buf;
PUTSHORT(0, cp2); /*%< Top 16 bits of time. */
PUTLONG(timesigned, cp2);
PUTSHORT(NS_TSIG_FUDGE, cp2);
dst_verify_data(SIG_MODE_UPDATE, state->key, &state->ctx,
buf, (int)(cp2 - buf), NULL, 0);
n = dst_verify_data(SIG_MODE_FINAL, state->key, &state->ctx, NULL, 0,
sigstart, (int)sigfieldlen);
if (n < 0)
return (-ns_r_badsig);
if (sigfieldlen > sizeof(state->sig))
return (NS_TSIG_ERROR_NO_SPACE);
memcpy(state->sig, sigstart, sigfieldlen);
state->siglen = sigfieldlen;
/* Verify the time. */
if (abs((int)(timesigned - time(NULL))) > fudge)
return (-ns_r_badtime);
*msglen = (int)(recstart - msg);
if (error != NOERROR)
return (error);
return (0);
}
/*! \file */
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