xref: /src/lib/libresolv/ns_sign.c

/*	$NetBSD: ns_sign.c,v 1.2 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>
#if 0
static const char rcsid[] = "Id: ns_sign.c,v 1.6 2006/03/09 23:57:56 marka Exp ";
#else
__RCSID("$NetBSD: ns_sign.c,v 1.2 2022/04/19 20:32:17 rillig Exp $");
#endif

/* 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 <isc/assertions.h>

#include "port_after.h"

#define BOUNDS_CHECK(ptr, count) \
	do { \
		if ((ptr) + (count) > eob) { \
			errno = EMSGSIZE; \
			return(NS_TSIG_ERROR_NO_SPACE); \
		} \
	} while (0)

/*%
 *  ns_sign
 *
 * Parameters:
 *\li	msg		message to be sent
 *\li	msglen		input - length of message
 *			output - length of signed message
 *\li	msgsize		length of buffer containing message
 *\li	error		value to put in the error field
 *\li	key		tsig key used for signing
 *\li	querysig	(response), the signature in the query
 *\li	querysiglen	(response), the length of the signature in the query
 *\li	sig		a buffer to hold the generated signature
 *\li	siglen		input - length of signature buffer
 *			output - length of signature
 *
 * Errors:
 *\li	- bad input data (-1)
 *\li	- bad key / sign failed (-BADKEY)
 *\li	- not enough space (NS_TSIG_ERROR_NO_SPACE)
 */
int
ns_sign(u_char *msg, int *msglen, int msgsize, int error, void *k,
	const u_char *querysig, int querysiglen, u_char *sig, int *siglen,
	time_t in_timesigned)
{
	return(ns_sign2(msg, msglen, msgsize, error, k,
			querysig, querysiglen, sig, siglen,
			in_timesigned, NULL, NULL));
}

int
ns_sign2(u_char *msg, int *msglen, int msgsize, int error, void *k,
	 const u_char *querysig, int querysiglen, u_char *sig, int *siglen,
	 time_t in_timesigned, u_char **dnptrs, u_char **lastdnptr)
{
	HEADER *hp = (void *)msg;
	DST_KEY *key = (DST_KEY *)k;
	u_char *cp, *eob;
	u_char *lenp;
	u_char *alg;
	int n;
	time_t timesigned;
        u_char name[NS_MAXCDNAME];

	dst_init();
	if (msg == NULL || msglen == NULL || sig == NULL || siglen == NULL)
		return (-1);

	cp = msg + *msglen;
	eob = msg + msgsize;

	/* Name. */
	if (key != NULL && error != ns_r_badsig && error != ns_r_badkey) {
		n = ns_name_pton(key->dk_key_name, name, sizeof name);
		if (n != -1)
			n = ns_name_pack(name, cp, (int)(eob - cp),
					 (void *)dnptrs,
					 (void *)lastdnptr);

	} else {
		n = ns_name_pton("", name, sizeof name);
		if (n != -1)
			n = ns_name_pack(name, cp, (int)(eob - cp), NULL, NULL);
	}
	if (n < 0)
		return (NS_TSIG_ERROR_NO_SPACE);
	cp += n;

	/* Type, class, ttl, length (not filled in yet). */
	BOUNDS_CHECK(cp, INT16SZ + INT16SZ + INT32SZ + INT16SZ);
	PUTSHORT(ns_t_tsig, cp);
	PUTSHORT(ns_c_any, cp);
	PUTLONG(0, cp);		/*%< TTL */
	lenp = cp;
	cp += 2;

	/* Alg. */
	if (key != NULL && error != ns_r_badsig && error != ns_r_badkey) {
		if (key->dk_alg != KEY_HMAC_MD5)
			return (-ns_r_badkey);
		n = dn_comp(NS_TSIG_ALG_HMAC_MD5, cp, (int)(eob - cp), NULL,
		    NULL);
	}
	else
		n = dn_comp("", cp, (int)(eob - cp), NULL, NULL);
	if (n < 0)
		return (NS_TSIG_ERROR_NO_SPACE);
	alg = cp;
	cp += n;

	/* Time. */
	BOUNDS_CHECK(cp, INT16SZ + INT32SZ + INT16SZ);
	PUTSHORT(0, cp);
	timesigned = time(NULL);
	if (error != ns_r_badtime)
		PUTLONG(timesigned, cp);
	else
		PUTLONG(in_timesigned, cp);
	PUTSHORT(NS_TSIG_FUDGE, cp);

	/* Compute the signature. */
	if (key != NULL && error != ns_r_badsig && error != ns_r_badkey) {
		void *ctx;
		u_char buf[NS_MAXCDNAME], *cp2;
		int nn;

		dst_sign_data(SIG_MODE_INIT, key, &ctx, NULL, 0, NULL, 0);

		/* Digest the query signature, if this is a response. */
		if (querysiglen > 0 && querysig != NULL) {
			u_int16_t len_n = htons(querysiglen);
			dst_sign_data(SIG_MODE_UPDATE, key, &ctx,
				      (void *)&len_n, INT16SZ, NULL, 0);
			dst_sign_data(SIG_MODE_UPDATE, key, &ctx,
				      querysig, querysiglen, NULL, 0);
		}

		/* Digest the message. */
		dst_sign_data(SIG_MODE_UPDATE, key, &ctx, msg, *msglen,
			      NULL, 0);

		/* Digest the key name. */
		nn = ns_name_ntol(name, buf, sizeof(buf));
		INSIST(nn > 0);
		dst_sign_data(SIG_MODE_UPDATE, key, &ctx, buf, nn, NULL, 0);

		/* Digest the class and TTL. */
		cp2 = buf;
		PUTSHORT(ns_c_any, cp2);
		PUTLONG(0, cp2);
		dst_sign_data(SIG_MODE_UPDATE, key, &ctx, buf, (int)(cp2 - buf),
			      NULL, 0);

		/* Digest the algorithm. */
		nn = ns_name_ntol(alg, buf, sizeof(buf));
		INSIST(nn > 0);
		dst_sign_data(SIG_MODE_UPDATE, key, &ctx, buf, nn, NULL, 0);

		/* Digest the time signed, fudge, error, and other data */
		cp2 = buf;
		PUTSHORT(0, cp2);	/*%< Top 16 bits of time */
		if (error != ns_r_badtime)
			PUTLONG(timesigned, cp2);
		else
			PUTLONG(in_timesigned, cp2);
		PUTSHORT(NS_TSIG_FUDGE, cp2);
		PUTSHORT(error, cp2);	/*%< Error */
		if (error != ns_r_badtime)
			PUTSHORT(0, cp2);	/*%< Other data length */
		else {
			PUTSHORT(INT16SZ+INT32SZ, cp2);	/*%< Other data length */
			PUTSHORT(0, cp2);	/*%< Top 16 bits of time */
			PUTLONG(timesigned, cp2);
		}
		dst_sign_data(SIG_MODE_UPDATE, key, &ctx, buf, (int)(cp2 - buf),
			      NULL, 0);

		nn = dst_sign_data(SIG_MODE_FINAL, key, &ctx, NULL, 0,
				  sig, *siglen);
		if (nn < 0)
			return (-ns_r_badkey);
		*siglen = nn;
	} else
		*siglen = 0;

	/* Add the signature. */
	BOUNDS_CHECK(cp, INT16SZ + (*siglen));
	PUTSHORT(*siglen, cp);
	memcpy(cp, sig, *siglen);
	cp += (*siglen);

	/* The original message ID & error. */
	BOUNDS_CHECK(cp, INT16SZ + INT16SZ);
	PUTSHORT(ntohs(hp->id), cp);	/*%< already in network order */
	PUTSHORT(error, cp);

	/* Other data. */
	BOUNDS_CHECK(cp, INT16SZ);
	if (error != ns_r_badtime)
		PUTSHORT(0, cp);	/*%< Other data length */
	else {
		PUTSHORT(INT16SZ+INT32SZ, cp);	/*%< Other data length */
		BOUNDS_CHECK(cp, INT32SZ+INT16SZ);
		PUTSHORT(0, cp);	/*%< Top 16 bits of time */
		PUTLONG(timesigned, cp);
	}

	/* Go back and fill in the length. */
	PUTSHORT(cp - lenp - INT16SZ, lenp);

	hp->arcount = htons(ntohs(hp->arcount) + 1);
	*msglen = (int)(cp - msg);
	return (0);
}

int
ns_sign_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_sign_tcp(u_char *msg, int *msglen, int msgsize, int error,
	    ns_tcp_tsig_state *state, int done)
{
	return (ns_sign_tcp2(msg, msglen, msgsize, error, state,
			     done, NULL, NULL));
}

int
ns_sign_tcp2(u_char *msg, int *msglen, int msgsize, int error,
	     ns_tcp_tsig_state *state, int done,
	     u_char **dnptrs, u_char **lastdnptr)
{
	u_char *cp, *eob, *lenp;
	u_char buf[MAXDNAME], *cp2;
	HEADER *hp = (void *)msg;
	time_t timesigned;
	int n;

	if (msg == NULL || msglen == NULL || state == NULL)
		return (-1);

	state->counter++;
	if (state->counter == 0)
		return (ns_sign2(msg, msglen, msgsize, error, state->key,
				 state->sig, state->siglen,
				 state->sig, &state->siglen, 0,
				 dnptrs, lastdnptr));

	if (state->siglen > 0) {
		u_int16_t siglen_n = htons(state->siglen);
		dst_sign_data(SIG_MODE_INIT, state->key, &state->ctx,
			      NULL, 0, NULL, 0);
		dst_sign_data(SIG_MODE_UPDATE, state->key, &state->ctx,
			      (void *)&siglen_n, INT16SZ, NULL, 0);
		dst_sign_data(SIG_MODE_UPDATE, state->key, &state->ctx,
			      state->sig, state->siglen, NULL, 0);
		state->siglen = 0;
	}

	dst_sign_data(SIG_MODE_UPDATE, state->key, &state->ctx, msg, *msglen,
		      NULL, 0);

	if (done == 0 && (state->counter % 100 != 0))
		return (0);

	cp = msg + *msglen;
	eob = msg + msgsize;

	/* Name. */
	n = dn_comp(state->key->dk_key_name, cp, (int)(eob - cp), dnptrs,
	    lastdnptr);
	if (n < 0)
		return (NS_TSIG_ERROR_NO_SPACE);
	cp += n;

	/* Type, class, ttl, length (not filled in yet). */
	BOUNDS_CHECK(cp, INT16SZ + INT16SZ + INT32SZ + INT16SZ);
	PUTSHORT(ns_t_tsig, cp);
	PUTSHORT(ns_c_any, cp);
	PUTLONG(0, cp);		/*%< TTL */
	lenp = cp;
	cp += 2;

	/* Alg. */
	n = dn_comp(NS_TSIG_ALG_HMAC_MD5, cp, (int)(eob - cp), NULL, NULL);
	if (n < 0)
		return (NS_TSIG_ERROR_NO_SPACE);
	cp += n;

	/* Time. */
	BOUNDS_CHECK(cp, INT16SZ + INT32SZ + INT16SZ);
	PUTSHORT(0, cp);
	timesigned = time(NULL);
	PUTLONG(timesigned, cp);
	PUTSHORT(NS_TSIG_FUDGE, cp);

	/*
	 * Compute the signature.
	 */

	/* 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_sign_data(SIG_MODE_UPDATE, state->key, &state->ctx,
		      buf, (int)(cp2 - buf), NULL, 0);

	n = dst_sign_data(SIG_MODE_FINAL, state->key, &state->ctx, NULL, 0,
			  state->sig, (int)sizeof(state->sig));
	if (n < 0)
		return (-ns_r_badkey);
	state->siglen = n;

	/* Add the signature. */
	BOUNDS_CHECK(cp, INT16SZ + state->siglen);
	PUTSHORT(state->siglen, cp);
	memcpy(cp, state->sig, state->siglen);
	cp += state->siglen;

	/* The original message ID & error. */
	BOUNDS_CHECK(cp, INT16SZ + INT16SZ);
	PUTSHORT(ntohs(hp->id), cp);	/*%< already in network order */
	PUTSHORT(error, cp);

	/* Other data. */
	BOUNDS_CHECK(cp, INT16SZ);
	PUTSHORT(0, cp);

	/* Go back and fill in the length. */
	PUTSHORT(cp - lenp - INT16SZ, lenp);

	hp->arcount = htons(ntohs(hp->arcount) + 1);
	*msglen = (int)(cp - msg);
	return (0);
}

/*! \file */