/*      $NetBSD: ns_verify.c,v 1.1.1.2 2012/09/09 16:08:04 christos 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.
*/

#ifndef lint
static const char rcsid[] = "Id: ns_verify.c,v 1.5 2006/03/09 23:57:56 marka 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 "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 = (HEADER *)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 = (HEADER *)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,
                                       (u_char *)&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, 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((*timesigned) - time(NULL)) > fudge)
               return (-ns_r_badtime);

       if (nostrip == 0) {
               *msglen = 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 = (HEADER *)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,
                               (u_char *)&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, 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, cp2 - buf, NULL, 0);

       n = dst_verify_data(SIG_MODE_FINAL, state->key, &state->ctx, NULL, 0,
                           sigstart, 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(timesigned - time(NULL)) > fudge)
               return (-ns_r_badtime);

       *msglen = recstart - msg;

       if (error != NOERROR)
               return (error);

       return (0);
}

/*! \file */

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