/* dnssec.c is Copyright (c) 2012 Giovanni Bajo <rasky@develer.com>
           and Copyright (c) 2012-2014 Simon Kelley

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 dated June, 1991, or
   (at your option) version 3 dated 29 June, 2007.

   This program 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 General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
*/

#include "dnsmasq.h"

#ifdef HAVE_DNSSEC

#include <nettle/rsa.h>
#include <nettle/dsa.h>
#include <nettle/nettle-meta.h>
#include <gmp.h>

#define SERIAL_UNDEF  -100
#define SERIAL_EQ        0
#define SERIAL_LT       -1
#define SERIAL_GT        1

/* http://www.iana.org/assignments/ds-rr-types/ds-rr-types.xhtml */
static char *ds_digest_name(int digest)
{
  switch (digest)
    {
    case 1: return "sha1";
    case 2: return "sha256";
    case 3: return "gosthash94";
    case 4: return "sha384";
    default: return NULL;
    }
}
 
/* http://www.iana.org/assignments/dns-sec-alg-numbers/dns-sec-alg-numbers.xhtml */
static char *algo_digest_name(int algo)
{
  switch (algo)
    {
    case 1: return "md5";
    case 3: return "sha1";
    case 5: return "sha1";
    case 6: return "sha1";
    case 7: return "sha1";
    case 8: return "sha256";
    case 10: return "sha512";
    case 12: return "gosthash94";
    case 13: return "sha256";
    case 14: return "sha384";
    default: return NULL;
    }
}
      
/* Find pointer to correct hash function in nettle library */
static const struct nettle_hash *hash_find(char *name)
{
  int i;
  
  if (!name)
    return NULL;
  
  for (i = 0; nettle_hashes[i]; i++)
    {
      if (strcmp(nettle_hashes[i]->name, name) == 0)
	return nettle_hashes[i];
    }

  return NULL;
}

/* expand ctx and digest memory allocations if necessary and init hash function */
static int hash_init(const struct nettle_hash *hash, void **ctxp, unsigned char **digestp)
{
  static void *ctx = NULL;
  static unsigned char *digest = NULL;
  static unsigned int ctx_sz = 0;
  static unsigned int digest_sz = 0;

  void *new;

  if (ctx_sz < hash->context_size)
    {
      if (!(new = whine_malloc(hash->context_size)))
	return 0;
      if (ctx)
	free(ctx);
      ctx = new;
      ctx_sz = hash->context_size;
    }
  
  if (digest_sz < hash->digest_size)
    {
      if (!(new = whine_malloc(hash->digest_size)))
	return 0;
      if (digest)
	free(digest);
      digest = new;
      digest_sz = hash->digest_size;
    }

  *ctxp = ctx;
  *digestp = digest;

  hash->init(ctx);

  return 1;
}
  
static int rsa_verify(struct blockdata *key_data, unsigned int key_len, unsigned char *sig, size_t sig_len,
		      unsigned char *digest, int algo)
{
  unsigned char *p;
  size_t exp_len;
  
  static struct rsa_public_key *key = NULL;
  static mpz_t sig_mpz;
  
  if (key == NULL)
    {
      if (!(key = whine_malloc(sizeof(struct rsa_public_key))))
	return 0;
      
      nettle_rsa_public_key_init(key);
      mpz_init(sig_mpz);
    }
  
  if ((key_len < 3) || !(p = blockdata_retrieve(key_data, key_len, NULL)))
    return 0;
  
  key_len--;
  if ((exp_len = *p++) == 0)
    {
      GETSHORT(exp_len, p);
      key_len -= 2;
    }
  
  if (exp_len >= key_len)
    return 0;
  
  key->size =  key_len - exp_len;
  mpz_import(key->e, exp_len, 1, 1, 0, 0, p);
  mpz_import(key->n, key->size, 1, 1, 0, 0, p + exp_len);

  mpz_import(sig_mpz, sig_len, 1, 1, 0, 0, sig);
  
  switch (algo)
    {
    case 1:
      return nettle_rsa_md5_verify_digest(key, digest, sig_mpz);
    case 5: case 7:
      return nettle_rsa_sha1_verify_digest(key, digest, sig_mpz);
    case 8:
      return nettle_rsa_sha256_verify_digest(key, digest, sig_mpz);
    case 10:
      return nettle_rsa_sha512_verify_digest(key, digest, sig_mpz);
    }

  return 0;
}  

static int dsa_verify(struct blockdata *key_data, unsigned int key_len, unsigned char *sig, size_t sig_len,
		      unsigned char *digest, int algo)
{
  unsigned char *p;
  unsigned int t;
  
  static struct dsa_public_key *key = NULL;
  static struct dsa_signature *sig_struct;
  
  if (key == NULL)
    {
      if (!(sig_struct = whine_malloc(sizeof(struct dsa_signature))) || 
	  !(key = whine_malloc(sizeof(struct dsa_public_key)))) 
	return 0;
      
      nettle_dsa_public_key_init(key);
      nettle_dsa_signature_init(sig_struct);
    }
  
  if ((sig_len < 41) || !(p = blockdata_retrieve(key_data, key_len, NULL)))
    return 0;
  
  t = *p++;
  
  if (key_len < (213 + (t * 24)))
    return 0;

  mpz_import(key->q, 20, 1, 1, 0, 0, p); p += 20;
  mpz_import(key->p, 64 + (t*8), 1, 1, 0, 0, p); p += 64 + (t*8);
  mpz_import(key->g, 64 + (t*8), 1, 1, 0, 0, p); p += 64 + (t*8);
  mpz_import(key->y, 64 + (t*8), 1, 1, 0, 0, p); p += 64 + (t*8);
  
  mpz_import(sig_struct->r, 20, 1, 1, 0, 0, sig+1);
  mpz_import(sig_struct->s, 20, 1, 1, 0, 0, sig+21);
  
  (void)algo;

  return nettle_dsa_sha1_verify_digest(key, digest, sig_struct);
} 
 
static int verify(struct blockdata *key_data, unsigned int key_len, unsigned char *sig, size_t sig_len,
		  unsigned char *digest, int algo)
{
  switch (algo)
    {
    case 1: case 5: case 7: case 8: case 10:
      return rsa_verify(key_data, key_len, sig, sig_len, digest, algo);
      
    case 3: case 6: 
      return dsa_verify(key_data, key_len, sig, sig_len, digest, algo);
    }
  
  return 0;
}

/* Convert from presentation format to wire format, in place.
   Also map UC -> LC.
   Note that using extract_name to get presentation format
   then calling to_wire() removes compression and maps case,
   thus generating names in canonical form.
   Calling to_wire followed by from_wire is almost an identity,
   except that the UC remains mapped to LC. 
*/
static int to_wire(char *name)
{
  unsigned char *l, *p, term;
  int len;

  for (l = (unsigned char*)name; *l != 0; l = p)
    {
      for (p = l; *p != '.' && *p != 0; p++)
	if (*p >= 'A' && *p <= 'Z')
	  *p = *p - 'A' + 'a';
      
      term = *p;
      
      if ((len = p - l) != 0)
	memmove(l+1, l, len);
      *l = len;
      
      p++;
      
      if (term == 0)
	*p = 0;
    }
  
  return l + 1 - (unsigned char *)name;
}

/* Note: no compression  allowed in input. */
static void from_wire(char *name)
{
  unsigned char *l;
  int len;

  for (l = (unsigned char *)name; *l != 0; l += len+1)
    {
      len = *l;
      memmove(l, l+1, len);
      l[len] = '.';
    }

  *(l-1) = 0;
}

/* Input in presentation format */
static int count_labels(char *name)
{
  int i;

  if (*name == 0)
    return 0;

  for (i = 0; *name; name++)
    if (*name == '.')
      i++;

  return i+1;
}

/* Implement RFC1982 wrapped compare for 32-bit numbers */
static int serial_compare_32(unsigned long s1, unsigned long s2)
{
  if (s1 == s2)
    return SERIAL_EQ;

  if ((s1 < s2 && (s2 - s1) < (1UL<<31)) ||
      (s1 > s2 && (s1 - s2) > (1UL<<31)))
    return SERIAL_LT;
  if ((s1 < s2 && (s2 - s1) > (1UL<<31)) ||
      (s1 > s2 && (s1 - s2) < (1UL<<31)))
    return SERIAL_GT;
  return SERIAL_UNDEF;
}

/* Check whether today/now is between date_start and date_end */
static int check_date_range(unsigned long date_start, unsigned long date_end)
{
  unsigned long curtime = time(0);
  
  /* We must explicitly check against wanted values, because of SERIAL_UNDEF */
  return serial_compare_32(curtime, date_start) == SERIAL_GT
    && serial_compare_32(curtime, date_end) == SERIAL_LT;
}

static u16 *get_desc(int type)
{
  /* List of RRtypes which include domains in the data.
     0 -> domain
     integer -> no of plain bytes
     -1 -> end

     zero is not a valid RRtype, so the final entry is returned for
     anything which needs no mangling.
  */
  
  static u16 rr_desc[] = 
    { 
      T_NS, 0, -1, 
      T_MD, 0, -1,
      T_MF, 0, -1,
      T_CNAME, 0, -1,
      T_SOA, 0, 0, -1,
      T_MB, 0, -1,
      T_MG, 0, -1,
      T_MR, 0, -1,
      T_PTR, 0, -1,
      T_MINFO, 0, 0, -1,
      T_MX, 2, 0, -1,
      T_RP, 0, 0, -1,
      T_AFSDB, 2, 0, -1,
      T_RT, 2, 0, -1,
      T_SIG, 18, 0, -1,
      T_PX, 2, 0, 0, -1,
      T_NXT, 0, -1,
      T_KX, 2, 0, -1,
      T_SRV, 6, 0, -1,
      T_DNAME, 0, -1,
      0, -1 /* wildcard/catchall */
    }; 
  
  u16 *p = rr_desc;
  
  while (*p != type && *p != 0)
    while (*p++ != (u16)-1);

  return p+1;
}

/* Return bytes of canonicalised rdata, when the return value is zero, the remaining 
   data, pointed to by *p, should be used raw. */
static int get_rdata(struct dns_header *header, size_t plen, unsigned char *end, char *buff, 
		     unsigned char **p, u16 **desc)
{
  int d = **desc;
  
  (*desc)++;
  
  /* No more data needs mangling */
  if (d == (u16)-1)
    return 0;
  
  if (d == 0 && extract_name(header, plen, p, buff, 1, 0))
    /* domain-name, canonicalise */
    return to_wire(buff);
  else
    { 
      /* plain data preceding a domain-name, don't run off the end of the data */
      if ((end - *p) < d)
	d = end - *p;
      
      if (d != 0)
	{
	  memcpy(buff, *p, d);
	  *p += d;
	}
      
      return d;
    }
}

/* Bubble sort the RRset into the canonical order. 
   Note that the byte-streams from two RRs may get unsynced: consider 
   RRs which have two domain-names at the start and then other data.
   The domain-names may have different lengths in each RR, but sort equal

   ------------
   |abcde|fghi|
   ------------
   |abcd|efghi|
   ------------

   leaving the following bytes as deciding the order. Hence the nasty left1 and left2 variables.
*/

static void sort_rrset(struct dns_header *header, size_t plen, u16 *rr_desc, int rrsetidx, 
		       unsigned char **rrset, char *buff1, char *buff2)
{
  int swap, quit, i;
  
  do
    {
      for (swap = 0, i = 0; i < rrsetidx-1; i++)
	{
	  int rdlen1, rdlen2, left1, left2, len1, len2, len, rc;
	  u16 *dp1, *dp2;
	  unsigned char *end1, *end2;
	  unsigned char *p1 = skip_name(rrset[i], header, plen, 10);
	  unsigned char *p2 = skip_name(rrset[i+1], header, plen, 10);
	  
	  p1 += 8; /* skip class, type, ttl */
	  GETSHORT(rdlen1, p1);
	  end1 = p1 + rdlen1;
	  
	  p2 += 8; /* skip class, type, ttl */
	  GETSHORT(rdlen2, p2);
	  end2 = p2 + rdlen2; 
	  
	  dp1 = dp2 = rr_desc;
	  
	  for (quit = 0, left1 = 0, left2 = 0, len1 = 0, len2 = 0; !quit;)
	    {
	      if (left1 != 0)
		memmove(buff1, buff1 + len1 - left1, left1);
	      
	      if ((len1 = get_rdata(header, plen, end1, buff1 + left1, &p1, &dp1)) == 0)
		{
		  quit = 1;
		  len1 = end1 - p1;
		  memcpy(buff1 + left1, p1, len1);
		}
	      len1 += left1;
	      
	      if (left2 != 0)
		memmove(buff2, buff2 + len2 - left2, left2);
	      
	      if ((len2 = get_rdata(header, plen, end2, buff2 + left2, &p2, &dp2)) == 0)
		{
		  quit = 1;
		  len2 = end2 - p2;
		  memcpy(buff2 + left2, p2, len2);
		}
	      len2 += left2;
	       
	      if (len1 > len2)
		left1 = len1 - len2, left2 = 0, len = len2;
	      else
		left2 = len2 - len1, left1 = 0, len = len1;
	      
	      rc = (len == 0) ? 0 : memcmp(buff1, buff2, len);
	      
	      if (rc > 0 || (rc == 0 && quit && len1 > len2))
		{
		  unsigned char *tmp = rrset[i+1];
		  rrset[i+1] = rrset[i];
		  rrset[i] = tmp;
		  swap = quit = 1;
		}
	      else if (rc < 0)
		quit = 1;
	    }
	}
    } while (swap);
}

/* Validate a single RRset (class, type, name) in the supplied DNS reply 
   Return code:
   STAT_SECURE   if it validates.
   STAT_INSECURE can't validate (no RRSIG, bad packet).
   STAT_BOGUS    signature is wrong.
   STAT_NEED_KEY need DNSKEY to complete validation (name is returned in keyname)

   if key is non-NULL, use that key, which has the algo and tag given in the params of those names,
   otherwise find the key in the cache.
*/
static int validate_rrset(time_t now, struct dns_header *header, size_t plen, int class, 
			  int type, char *name, char *keyname, struct blockdata *key, int keylen, int algo_in, int keytag_in)
{
  static unsigned char **rrset = NULL, **sigs = NULL;
  static int rrset_sz = 0, sig_sz = 0;
  
  unsigned char *p;
  int rrsetidx, sigidx, res, rdlen, j, name_labels;
  struct crec *crecp = NULL;
  int type_covered, algo, labels, orig_ttl, sig_expiration, sig_inception, key_tag;
  u16 *rr_desc = get_desc(type);

  if (!(p = skip_questions(header, plen)))
    return STAT_INSECURE;

  name_labels = count_labels(name); /* For 4035 5.3.2 check */

  cache_start_insert(); /* RRSIGS */

  /* look for RRSIGs for this RRset and get pointers to each RR in the set. */
  for (rrsetidx = 0, sigidx = 0, j = ntohs(header->ancount) + ntohs(header->nscount); 
       j != 0; j--) 
    {
      unsigned char *pstart, *pdata;
      int stype, sclass, ttl;

      pstart = p;
      
      if (!(res = extract_name(header, plen, &p, name, 0, 10)))
	return STAT_INSECURE; /* bad packet */
      
      GETSHORT(stype, p);
      GETSHORT(sclass, p);
      GETLONG(ttl, p);
      
      pdata = p;

      GETSHORT(rdlen, p);
      
      if (!CHECK_LEN(header, p, plen, rdlen))
	return STAT_INSECURE; 
      
      if (res == 1 && sclass == class)
	{
	  if (stype == type)
	    {
	      if (rrsetidx == rrset_sz)
		{
		  unsigned char **new;

		  /* expand */
		  if (!(new = whine_malloc((rrset_sz + 5) * sizeof(unsigned char **))))
		    return STAT_INSECURE;
		  
		  if (rrset)
		    {
		      memcpy(new, rrset, rrset_sz * sizeof(unsigned char **));
		      free(rrset);
		    }
		  
		  rrset = new;
		  rrset_sz += 5;
		}
	      rrset[rrsetidx++] = pstart;
	    }
	  
	  if (stype == T_RRSIG)
	    {
	       if (rdlen < 18)
		 return STAT_INSECURE; /* bad packet */ 
	         
	       GETSHORT(type_covered, p);
	       
	       if (type_covered == type)
		 {
		   if (sigidx == sig_sz)
		     {
		       unsigned char **new;
		       
		       /* expand */
		       if (!(new = whine_malloc((sig_sz + 5) * sizeof(unsigned char **))))
			 return STAT_INSECURE;
		       
		       if (sigs)
			 {
			   memcpy(new, sigs, sig_sz * sizeof(unsigned char **));
			   free(sigs);
			 }
		       
		       sigs = new;
		       sig_sz += 5;
		     }
		   
		   sigs[sigidx++] = pdata;

		   /* If it's a type we're going to cache, cache the RRISG too */
		   if (type_covered == T_A || type_covered == T_AAAA ||
		       type_covered == T_CNAME || type_covered == T_DS || 
		       type_covered == T_DNSKEY || type_covered == T_PTR) 
		     {
		       struct all_addr a;
		       struct blockdata *block;
		       a.addr.dnssec.class = class;
		       a.addr.dnssec.type = type_covered;
		       
		       algo = *p++;
		       p += 13; /* labels, orig_ttl, expiration, inception */
		       GETSHORT(key_tag, p);	
		       if ((block = blockdata_alloc((char*)pdata + 2, rdlen)) &&
			   (crecp = cache_insert(name, &a, now, ttl,  F_FORWARD | F_DNSKEY | F_DS)))
			 {
			   crecp->uid = class;
			   crecp->addr.sig.keydata = block;
			   crecp->addr.sig.keylen = rdlen;
			   crecp->addr.sig.keytag = key_tag;
			   crecp->addr.sig.type_covered = type_covered;
			   crecp->addr.sig.algo = algo;
			 }
		     }
		 } 
	       
	       p = pdata + 2; /* restore for ADD_RDLEN */
	    }
	}
     
      if (!ADD_RDLEN(header, p, plen, rdlen))
	return STAT_INSECURE;
    }
  
  cache_end_insert(); /* RRSIGS */
  
  /* RRset empty, no RRSIGs */
  if (rrsetidx == 0 || sigidx == 0)
    return STAT_INSECURE; 
  
  /* Sort RRset records into canonical order. 
     Note that at this point keyname and name buffs are
     unused, and used as workspace by the sort. */
  sort_rrset(header, plen, rr_desc, rrsetidx, rrset, name, keyname);
         
  /* Now try all the sigs to try and find one which validates */
  for (j = 0; j <sigidx; j++)
    {
      unsigned char *psav, *sig;
      int i, wire_len, sig_len;
      const struct nettle_hash *hash;
      void *ctx;
      unsigned char *digest;
      u32 nsigttl;
      
      p = sigs[j];
      GETSHORT(rdlen, p); /* rdlen >= 18 checked previously */
      psav = p;
      
      p += 2; /* type_covered - already checked */
      algo = *p++;
      labels = *p++;
      GETLONG(orig_ttl, p);
      GETLONG(sig_expiration, p);
      GETLONG(sig_inception, p);
      GETSHORT(key_tag, p);
      
      if (!extract_name(header, plen, &p, keyname, 1, 0))
	return STAT_INSECURE;
      
      if (!check_date_range(sig_inception, sig_expiration) ||
	  labels > name_labels ||
	  !(hash = hash_find(algo_digest_name(algo))) ||
	  !hash_init(hash, &ctx, &digest))
	continue;
	
      /* OK, we have the signature record, see if the relevant DNSKEY is in the cache. */
      if (!key && !(crecp = cache_find_by_name(NULL, keyname, now, F_DNSKEY)))
	return STAT_NEED_KEY;
      
      sig = p;
      sig_len = rdlen - (p - psav);
              
      nsigttl = htonl(orig_ttl);
      
      hash->update(ctx, 18, psav);
      wire_len = to_wire(keyname);
      hash->update(ctx, (unsigned int)wire_len, (unsigned char*)keyname);
      from_wire(keyname);
      
      for (i = 0; i < rrsetidx; ++i)
	{
	  int seg;
	  unsigned char *end, *cp;
	  char *name_start = name;
	  u16 len, *dp;

	  p = rrset[i];
	  if (!extract_name(header, plen, &p, name, 1, 10)) 
	    return STAT_INSECURE;

	  /* if more labels than in RRsig name, hash *.<no labels in rrsig labels field>  4035 5.3.2 */
	  if (labels < name_labels)
	    {
	      int k;
	      for (k = name_labels - labels; k != 0; k--)
		while (*name_start != '.' && *name_start != 0)
		  name_start++;
	      name_start--;
	      *name_start = '*';
	    }
	  
	  wire_len = to_wire(name_start);
	  hash->update(ctx, (unsigned int)wire_len, (unsigned char *)name_start);
	  hash->update(ctx, 4, p); /* class and type */
	  hash->update(ctx, 4, (unsigned char *)&nsigttl);
	  
	  p += 8; /* skip class, type, ttl */
	  GETSHORT(rdlen, p);
	  if (!CHECK_LEN(header, p, plen, rdlen))
	    return STAT_INSECURE; 
	  
	  end = p + rdlen;
	  
	  /* canonicalise rdata and calculate length of same, use name buffer as workspace */
	  cp = p;
	  dp = rr_desc;
	  for (len = 0; (seg = get_rdata(header, plen, end, name, &cp, &dp)) != 0; len += seg);
	  len += end - cp;
	  len = htons(len);
	  hash->update(ctx, 2, (unsigned char *)&len); 
	  
	  /* Now canonicalise again and digest. */
	  cp = p;
	  dp = rr_desc;
	  while ((seg = get_rdata(header, plen, end, name, &cp, &dp)))
	    hash->update(ctx, seg, (unsigned char *)name);
	  if (cp != end)
	    hash->update(ctx, end - cp, cp);
	}
     
      hash->digest(ctx, hash->digest_size, digest);
      
      /* namebuff used for workspace above, restore to leave unchanged on exit */
      p = (unsigned char*)(rrset[0]);
      extract_name(header, plen, &p, name, 1, 0);

      if (key)
	{
	  if (algo_in == algo && keytag_in == key_tag &&
	      verify(key, keylen, sig, sig_len, digest, algo))
	    return STAT_SECURE;
	}
      else
	{
	  /* iterate through all possible keys 4035 5.3.1 */
	  for (; crecp; crecp = cache_find_by_name(crecp, keyname, now, F_DNSKEY))
	    if (crecp->addr.key.algo == algo && 
		crecp->addr.key.keytag == key_tag &&
		crecp->uid == class &&
		verify(crecp->addr.key.keydata, crecp->addr.key.keylen, sig, sig_len, digest, algo))
	      return STAT_SECURE;
	}
    }

  return STAT_BOGUS;
}
 
/* The DNS packet is expected to contain the answer to a DNSKEY query.
   Leave name of query in name.
   Put all DNSKEYs in the answer which are valid into the cache.
   return codes:
         STAT_INSECURE bad packet, no DNSKEYs in reply.
	 STAT_SECURE   At least one valid DNSKEY found and in cache.
	 STAT_BOGUS    No DNSKEYs found, which  can be validated with DS,
	               or self-sign for DNSKEY RRset is not valid.
	 STAT_NEED_DS  DS records to validate a key not found, name in keyname 
*/
int dnssec_validate_by_ds(time_t now, struct dns_header *header, size_t plen, char *name, char *keyname, int class)
{
  unsigned char *psave, *p = (unsigned char *)(header+1);
  struct crec *crecp, *recp1;
  int rc, j, qtype, qclass, ttl, rdlen, flags, algo, valid, keytag;
  struct blockdata *key;
  struct all_addr a;

  if (ntohs(header->qdcount) != 1 ||
      !extract_name(header, plen, &p, name, 1, 4))
    {
      strcpy(name, "<none>");
      return STAT_INSECURE;
    }

  GETSHORT(qtype, p);
  GETSHORT(qclass, p);
  
  if (qtype != T_DNSKEY || qclass != class || ntohs(header->ancount) == 0)
    return STAT_INSECURE;

   /* See if we have cached a DS record which validates this key */
  if (!(crecp = cache_find_by_name(NULL, name, now, F_DS)))
    {
      strcpy(keyname, name);
      return STAT_NEED_DS;
    }

  /* NOTE, we need to find ONE DNSKEY which matches the DS */
  for (valid = 0, j = ntohs(header->ancount); j != 0 && !valid; j--) 
    {
      /* Ensure we have type, class  TTL and length */
      if (!(rc = extract_name(header, plen, &p, name, 0, 10)))
	return STAT_INSECURE; /* bad packet */
  
      GETSHORT(qtype, p); 
      GETSHORT(qclass, p);
      GETLONG(ttl, p);
      GETSHORT(rdlen, p);
 
      if (!CHECK_LEN(header, p, plen, rdlen) || rdlen < 4)
	return STAT_INSECURE; /* bad packet */
      
      if (qclass != class || qtype != T_DNSKEY || rc == 2)
	{
	  p += rdlen;
	  continue;
	}
            
      psave = p;
      
      GETSHORT(flags, p);
      if (*p++ != 3)
	return STAT_INSECURE;
      algo = *p++;
      keytag = dnskey_keytag(algo, flags, p, rdlen - 4);
      key = NULL;
      
      /* key must have zone key flag set */
      if (flags & 0x100)
	key = blockdata_alloc((char*)p, rdlen - 4);
      
      p = psave;
      
      if (!ADD_RDLEN(header, p, plen, rdlen))
	return STAT_INSECURE; /* bad packet */
      
      /* No zone key flag or malloc failure */
      if (!key)
	continue;
      
      for (recp1 = crecp; recp1; recp1 = cache_find_by_name(recp1, name, now, F_DS))
	{
	  void *ctx;
	  unsigned char *digest, *ds_digest;
	  const struct nettle_hash *hash;
	  
	  if (recp1->addr.ds.algo == algo && 
	      recp1->addr.ds.keytag == keytag &&
	      recp1->uid == class &&
	      (hash = hash_find(ds_digest_name(recp1->addr.ds.digest))) &&
	      hash_init(hash, &ctx, &digest))
	    
	    {
	      int wire_len = to_wire(name);
	      
	      /* Note that digest may be different between DSs, so 
		 we can't move this outside the loop. */
	      hash->update(ctx, (unsigned int)wire_len, (unsigned char *)name);
	      hash->update(ctx, (unsigned int)rdlen, psave);
	      hash->digest(ctx, hash->digest_size, digest);
	      
	      from_wire(name);
	      
	      if (recp1->addr.ds.keylen == (int)hash->digest_size &&
		  (ds_digest = blockdata_retrieve(recp1->addr.key.keydata, recp1->addr.ds.keylen, NULL)) &&
		  memcmp(ds_digest, digest, recp1->addr.ds.keylen) == 0 &&
		  validate_rrset(now, header, plen, class, T_DNSKEY, name, keyname, key, rdlen - 4, algo, keytag))
		{
		  valid = 1;
		  break;
		}
	    }
	}
      blockdata_free(key);
    }

  if (valid)
    {
      /* DNSKEY RRset determined to be OK, now cache it. */
      cache_start_insert();
      
      p = skip_questions(header, plen);

      for (j = ntohs(header->ancount); j != 0; j--) 
	{
	  /* Ensure we have type, class  TTL and length */
	  if (!(rc = extract_name(header, plen, &p, name, 0, 10)))
	    return STAT_INSECURE; /* bad packet */
	  
	  GETSHORT(qtype, p); 
	  GETSHORT(qclass, p);
	  GETLONG(ttl, p);
	  GETSHORT(rdlen, p);
	  
	  if (qclass != class || qtype != T_DNSKEY || rc == 2)
	    {
	      if (ADD_RDLEN(header, p, plen, rdlen))
		continue;
	      
	      return STAT_INSECURE; /* bad packet */
	    }
	  
	  if (!CHECK_LEN(header, p, plen, rdlen) || rdlen < 4)
	    return STAT_INSECURE; /* bad packet */
      
	  psave = p;
	  
	  GETSHORT(flags, p);
	  if (*p++ != 3)
	    return STAT_INSECURE;
	  algo = *p++;
	  keytag = dnskey_keytag(algo, flags, p, rdlen - 4);
      
	  /* Cache needs to known class for DNSSEC stuff */
	  a.addr.dnssec.class = class;
	  
	  if ((key = blockdata_alloc((char*)p, rdlen - 4)) &&
	      (recp1 = cache_insert(name, &a, now, ttl, F_FORWARD | F_DNSKEY | F_DNSSECOK)))
	    {
	      struct all_addr a;
	      
	      a.addr.keytag = keytag;
	      log_query(F_KEYTAG | F_UPSTREAM, name, &a, "DNSKEY keytag %u");
	      
	      recp1->addr.key.keylen = rdlen - 4;
	      recp1->addr.key.keydata = key;
	      recp1->addr.key.algo = algo;
	      recp1->addr.key.keytag = keytag;
	      recp1->addr.key.flags = flags;
	      recp1->uid = class;
	    }
	  
	  p = psave;
	  if (!ADD_RDLEN(header, p, plen, rdlen))
	    return STAT_INSECURE; /* bad packet */
	}
      
      /* commit cache insert. */
      cache_end_insert();
      return STAT_SECURE;
    }

  log_query(F_UPSTREAM, name, NULL, "BOGUS DNSKEY");
  return STAT_BOGUS;
}

/* The DNS packet is expected to contain the answer to a DS query
   Leave name of DS query in name.
   Put all DSs in the answer which are valid into the cache.
   return codes:
   STAT_INSECURE    bad packet, no DS in reply.
   STAT_SECURE      At least one valid DS found and in cache.
   STAT_BOGUS       At least one DS found, which fails validation.
   STAT_NEED_DNSKEY DNSKEY records to validate a DS not found, name in keyname
*/

int dnssec_validate_ds(time_t now, struct dns_header *header, size_t plen, char *name, char *keyname, int class)
{
  unsigned char *p = (unsigned char *)(header+1);
  int qtype, qclass, val;

  if (ntohs(header->qdcount) != 1 ||
      !extract_name(header, plen, &p, name, 1, 4))
    {
      strcpy(name, "<none>");
      return STAT_INSECURE;
    }

  GETSHORT(qtype, p);
  GETSHORT(qclass, p);

  if (qtype != T_DS || qclass != class || ntohs(header->ancount) == 0)
    return STAT_INSECURE;
  
  val = dnssec_validate_reply(now, header, plen, name, keyname, NULL);
  
  if (val == STAT_BOGUS)
    log_query(F_UPSTREAM, name, NULL, "BOGUS DS");

  return val;
}

/* 4034 6.1 */
static int hostname_cmp(const char *a, const char *b)
{
  char *sa, *ea, *ca, *sb, *eb, *cb;
  unsigned char ac, bc;
  
  sa = ea = (char *)a + strlen(a);
  sb = eb = (char *)b + strlen(b);
 
  while (1)
    {
      while (sa != a && *(sa-1) != '.')
	sa--;
      
      while (sb != b && *(sb-1) != '.')
	sb--;

      ca = sa;
      cb = sb;

      while (1) 
	{
	  if (ca == ea)
	    {
	      if (cb == eb)
		break;
	      
	      return -1;
	    }
	  
	  if (cb == eb)
	    return 1;
	  
	  ac = (unsigned char) *ca++;
	  bc = (unsigned char) *cb++;
	  
	  if (ac >= 'A' && ac <= 'Z')
	    ac += 'a' - 'A';
	  if (bc >= 'A' && bc <= 'Z')
	    bc += 'a' - 'A';
	  
	  if (ac < bc)
	    return -1;
	  else if (ac != bc)
	    return 1;
	}

     
      if (sa == a)
	{
	  if (sb == b)
	    return 0;
	  
	  return -1;
	}
      
      if (sb == b)
	return 1;
      
      ea = sa--;
      eb = sb--;
    }
}


/* Validate all the RRsets in the answer and authority sections of the reply (4035:3.2.3) */
/* Returns are the same as validate_rrset, plus the class if the missing key is in *class */
int dnssec_validate_reply(time_t now, struct dns_header *header, size_t plen, char *name, char *keyname, int *class)
{
  unsigned char *ans_start, *p1, *p2;
  int type1, class1, rdlen1, type2, class2, rdlen2;
  int i, j, rc, have_nsec, have_nsec_equal, cname_count = 5;

  if ((RCODE(header) != NXDOMAIN && RCODE(header) != NOERROR) || ntohs(header->qdcount) != 1)
    return STAT_INSECURE;
  
  if (!(ans_start = skip_questions(header, plen)))
    return STAT_INSECURE;
   
  for (p1 = ans_start, i = 0; i < ntohs(header->ancount) + ntohs(header->nscount); i++)
    {
      if (!extract_name(header, plen, &p1, name, 1, 10))
	return STAT_INSECURE; /* bad packet */
      
      GETSHORT(type1, p1);
      GETSHORT(class1, p1);
      p1 += 4; /* TTL */
      GETSHORT(rdlen1, p1);
      
      /* Don't try and validate RRSIGs! */
      if (type1 != T_RRSIG)
	{
	  /* Check if we've done this RRset already */
	  for (p2 = ans_start, j = 0; j < i; j++)
	    {
	      if (!(rc = extract_name(header, plen, &p2, name, 0, 10)))
		return STAT_INSECURE; /* bad packet */
	      
	      GETSHORT(type2, p2);
	      GETSHORT(class2, p2);
	      p2 += 4; /* TTL */
	      GETSHORT(rdlen2, p2);
	      
	      if (type2 == type1 && class2 == class1 && rc == 1)
		break; /* Done it before: name, type, class all match. */
	      
	      if (!ADD_RDLEN(header, p2, plen, rdlen2))
		return STAT_INSECURE;
	    }
	  
	  /* Not done, validate now */
	  if (j == i)
	    {
	      if ((rc = validate_rrset(now, header, plen, class1, type1, name, keyname, NULL, 0, 0, 0)) != STAT_SECURE)
		{
		  if (class)
		    *class = class1; /* Class for DS or DNSKEY */
		  return rc;
		}

	      /* If we just validated a DS RRset, cache it */
	      if (type1 == T_DS)
		{
		  int ttl, keytag, algo, digest;
		  unsigned char *psave;
		  struct all_addr a;
		  struct blockdata *key;
		  struct crec *crecp;

		  cache_start_insert();
		  
		  for (p2 = ans_start, j = 0; j < ntohs(header->ancount) + ntohs(header->nscount); j++)
		    {
		      if (!(rc = extract_name(header, plen, &p2, name, 0, 10)))
			return STAT_INSECURE; /* bad packet */
		      
		      GETSHORT(type2, p2);
		      GETSHORT(class2, p2);
		      GETLONG(ttl, p2);
		      GETSHORT(rdlen2, p2);
		      
		      if (type2 == T_DS && class2 == class1 && rc == 1)
			{
			  psave = p2;
			  GETSHORT(keytag, p2);
			  algo = *p2++;
			  digest = *p2++;
			  
			  /* Cache needs to known class for DNSSEC stuff */
			  a.addr.dnssec.class = class2;
			  
			  if ((key = blockdata_alloc((char*)p2, rdlen2 - 4)) &&
			      (crecp = cache_insert(name, &a, now, ttl, F_FORWARD | F_DS | F_DNSSECOK)))
			    {
			      a.addr.keytag = keytag;
			      log_query(F_KEYTAG | F_UPSTREAM, name, &a, "DS keytag %u");
			      crecp->addr.ds.digest = digest;
			      crecp->addr.ds.keydata = key;
			      crecp->addr.ds.algo = algo;
			      crecp->addr.ds.keytag = keytag;
			      crecp->uid = class2;
			      crecp->addr.ds.keylen = rdlen2 - 4; 
			    } 
			  
			  p2 = psave;
			}
		      
		      if (!ADD_RDLEN(header, p2, plen, rdlen2))
			return STAT_INSECURE; /* bad packet */
		    }
		  
		  cache_end_insert();
		}
	    }
	}

      if (!ADD_RDLEN(header, p1, plen, rdlen1))
	return STAT_INSECURE;
    }

  /* OK, all the RRsets validate, now see if we have a NODATA or NXDOMAIN reply */

  p1 = (unsigned char *)(header+1);
  
  if (!extract_name(header, plen, &p1, name, 1, 4))
    return STAT_INSECURE;

  GETSHORT(type1, p1);
  GETSHORT(class1, p1);

  /* Can't validate RRSIG query */
  if (type1 == T_RRSIG)
    return STAT_INSECURE;

 cname_loop:
  for (j = ntohs(header->ancount); j != 0; j--) 
    {
      if (!(rc = extract_name(header, plen, &p1, name, 0, 10)))
	return STAT_INSECURE; /* bad packet */
      
      GETSHORT(type2, p1); 
      GETSHORT(class2, p1);
      p1 += 4; /* TTL */
      GETSHORT(rdlen2, p1);

      if (rc == 1 && class1 == class2)
	{
	  /* Do we have an answer for the question? */
	  if (type1 == type2)
	    return RCODE(header) == NXDOMAIN ? STAT_INSECURE : STAT_SECURE;
	  else if (type2 == T_CNAME)
	    {
	      /* looped CNAMES */
	      if (!cname_count-- || 
		  !extract_name(header, plen, &p1, name, 1, 0) ||
		  !(p1 = skip_questions(header, plen)))
		return STAT_INSECURE;
	      
	      goto cname_loop;
	    }
	} 

      if (!ADD_RDLEN(header, p1, plen, rdlen2))
	return STAT_INSECURE;
    }

  /* NXDOMAIN or NODATA reply, look for NSEC records to support that.
     At this point, p1 points to the start of the auth section.
     Use keyname as workspace */
  for (have_nsec = 0, have_nsec_equal = 0, p2 = NULL, rdlen2 = 0, j = ntohs(header->nscount); j != 0; j--) 
    {
      unsigned char *nsec_start = p1;
      if (!extract_name(header, plen, &p1, keyname, 1, 10))
	return STAT_INSECURE; /* bad packet */
      
      GETSHORT(type2, p1); 
      GETSHORT(class2, p1);
      p1 += 4; /* TTL */
      GETSHORT(rdlen1, p1);
      
      if (class1 == class2 && type2 == T_NSEC)
	{
	  have_nsec = 1;
	  rc = hostname_cmp(name, keyname);

	  if (rc >= 0)
	    {
	      if (p2)
		{
		  unsigned char *psave = p2;
		  /* new NSEC is smaller than name,
		     is it bigger than previous one? */
		  
		  /* get previous one into name buffer */
		  if (!extract_name(header, plen, &psave, name, 1, 0))
		    return STAT_INSECURE; /* bad packet */

		  if (hostname_cmp(name, keyname) < 0)
		    {
		      p2 = nsec_start;
		      rdlen2 = rdlen1;
		    }
		  
		  /* restore query name */
		  psave = (unsigned char *)(header+1);
		  if (!extract_name(header, plen, &psave, name, 1, 0))
		    return STAT_INSECURE;
		}
	      else
		{
		  /* There was no previous best candidate */
		  p2 = nsec_start;
		  rdlen2 = rdlen1; 
		}
	    }
	  
	  if (rc == 0)
	    have_nsec_equal = 1;
	}
	  
      if (!ADD_RDLEN(header, p1, plen, rdlen1))
	return STAT_INSECURE;
    }
     
  
  if (p2)
    {
      unsigned char *psave;
      p2 = skip_name(p2, header, plen, 0);
      p2 += 10; /* type, class, ttl, rdlen */
      psave = p2;
      extract_name(header, plen, &p2, keyname, 1, 0);
      rdlen2 -= p2 - psave;
    }

  /* At this point, have_nsec is set if there's at least one NSEC
     have_nsec_equal is set if there's an NSEC with the same name as the query;
     p2 points to the type bit maps of the biggest NSEC smaller than or equal to the query
     or NULL if the query is smaller than all of them.
     Keyname holds the next domain name for that NSEC.
     rdlen2 is the length of the bitmap field */
  

  if (RCODE(header) == NOERROR && have_nsec_equal)
    {
      int offset = (type1 & 0xff) >> 3;
      int mask = 0x80 >> (type1 & 0x07);
      
      while (rdlen2 >= 2)
	{
	  if (p2[0] == type1 >> 8)
	    {
	      /* Does the NSEC say our type exists? */
	      if (offset < p2[1] &&
		  (p2[offset+2] & mask) != 0)
		return STAT_INSECURE;
	      
	      break; /* finshed checking */
	    }
	  
	  rdlen2 -= p2[1];
	  p2 +=  p2[1];
	}
      
      return STAT_SECURE;
    }

  if (RCODE(header) == NXDOMAIN && have_nsec)
    {
      if (!p2 || hostname_cmp(name, keyname) < 0)
	return STAT_SECURE; /* Before the first, or in a proven gap */
    }

  return STAT_INSECURE;
}


/* Compute keytag (checksum to quickly index a key). See RFC4034 */
int dnskey_keytag(int alg, int flags, unsigned char *key, int keylen)
{
  if (alg == 1)
    {
      /* Algorithm 1 (RSAMD5) has a different (older) keytag calculation algorithm.
         See RFC4034, Appendix B.1 */
      return key[keylen-4] * 256 + key[keylen-3];
    }
  else
    {
      unsigned long ac;
      int i;

      ac = ((htons(flags) >> 8) | ((htons(flags) << 8) & 0xff00)) + 0x300 + alg;
      for (i = 0; i < keylen; ++i)
        ac += (i & 1) ? key[i] : key[i] << 8;
      ac += (ac >> 16) & 0xffff;
      return ac & 0xffff;
    }
}

size_t dnssec_generate_query(struct dns_header *header, char *end, char *name, int class, int type, union mysockaddr *addr)
{
  unsigned char *p;
  char types[20];
  
  querystr("dnssec-query", types, type);

  if (addr->sa.sa_family == AF_INET) 
    log_query(F_DNSSEC | F_IPV4, name, (struct all_addr *)&addr->in.sin_addr, types);
#ifdef HAVE_IPV6
  else
    log_query(F_DNSSEC | F_IPV6, name, (struct all_addr *)&addr->in6.sin6_addr, types);
#endif
  
  header->qdcount = htons(1);
  header->ancount = htons(0);
  header->nscount = htons(0);
  header->arcount = htons(0);

  header->hb3 = HB3_RD; 
  SET_OPCODE(header, QUERY);
  /* For debugging, set Checking Disabled, otherwise, have the upstream check too,
     this allows it to select auth servers when one is returning bad data. */
  header->hb4 = option_bool(OPT_DNSSEC_DEBUG) ? HB4_CD : 0;

  /* ID filled in later */

  p = (unsigned char *)(header+1);
	
  p = do_rfc1035_name(p, name);
  *p++ = 0;
  PUTSHORT(type, p);
  PUTSHORT(class, p);

  return add_do_bit(header, p - (unsigned char *)header, end);
}

unsigned char* hash_questions(struct dns_header *header, size_t plen, char *name)
{
  int q;
  unsigned int len;
  unsigned char *p = (unsigned char *)(header+1);
  const struct nettle_hash *hash;
  void *ctx;
  unsigned char *digest;
  
  if (!(hash = hash_find("sha1")) || !hash_init(hash, &ctx, &digest))
    return NULL;
  
  for (q = ntohs(header->qdcount); q != 0; q--) 
    {
      if (!extract_name(header, plen, &p, name, 1, 4))
	break; /* bad packet */
      
      len = to_wire(name);
      hash->update(ctx, len, (unsigned char *)name);
      /* CRC the class and type as well */
      hash->update(ctx, 4, p);

      p += 4;
      if (!CHECK_LEN(header, p, plen, 0))
	break; /* bad packet */
    }
  
  hash->digest(ctx, hash->digest_size, digest);
  return digest;
}

#endif /* HAVE_DNSSEC */