/src/unbound/util/data/msgencode.c

Source
/*
 * util/data/msgencode.c - Encode DNS messages, queries and replies.
 *
 * Copyright (c) 2007, NLnet Labs. All rights reserved.
 *
 * This software is open source.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 
 * Redistributions of source code must retain the above copyright notice,
 * this list of conditions and the following disclaimer.
 * 
 * Redistributions in binary form must reproduce the above copyright notice,
 * this list of conditions and the following disclaimer in the documentation
 * and/or other materials provided with the distribution.
 * 
 * Neither the name of the NLNET LABS nor the names of its contributors may
 * be used to endorse or promote products derived from this software without
 * specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/**
 * \file
 *
 * This file contains a routines to encode DNS messages.
 */

#include "config.h"
#include "util/data/msgencode.h"
#include "util/data/msgreply.h"
#include "util/data/msgparse.h"
#include "util/data/dname.h"
#include "util/log.h"
#include "util/regional.h"
#include "util/net_help.h"
#include "sldns/sbuffer.h"
#include "services/localzone.h"

#ifdef HAVE_TIME_H
#include <time.h>
#endif
#include <sys/time.h>

/** return code that means the function ran out of memory. negative so it does
 * not conflict with DNS rcodes. */
#define RETVAL_OUTMEM -2
/** return code that means the data did not fit (completely) in the packet */
#define RETVAL_TRUNC  -4
/** return code that means all is peachy keen. Equal to DNS rcode NOERROR */
#define RETVAL_OK 0
/** Max compressions we are willing to perform; more than that will result
 *  in semi-compressed messages, or truncated even on TCP for huge messages, to
 *  avoid locking the CPU for long */
#define MAX_COMPRESSION_PER_MESSAGE 120

/**
 * Data structure to help domain name compression in outgoing messages.
 * A tree of dnames and their offsets in the packet is kept.
 * It is kept sorted, not canonical, but by label at least, so that after
 * a lookup of a name you know its closest match, and the parent from that
 * closest match. These are possible compression targets.
 *
 * It is a binary tree, not a rbtree or balanced tree, as the effort
 * of keeping it balanced probably outweighs usefulness (given typical
 * DNS packet size).
 */
struct compress_tree_node {
  /** left node in tree, all smaller to this */
  struct compress_tree_node* left;
  /** right node in tree, all larger than this */
  struct compress_tree_node* right;

  /** the parent node - not for tree, but zone parent. One less label */
  struct compress_tree_node* parent;
  /** the domain name for this node. Pointer to uncompressed memory. */
  uint8_t* dname;
  /** number of labels in domain name, kept to help compare func. */
  int labs;
  /** offset in packet that points to this dname */
  size_t offset;
};

/**
 * Find domain name in tree, returns exact and closest match.
 * @param tree: root of tree.
 * @param dname: pointer to uncompressed dname.
 * @param labs: number of labels in domain name.
 * @param match: closest or exact match.
 *  guaranteed to be smaller or equal to the sought dname.
 *  can be null if the tree is empty.
 * @param matchlabels: number of labels that match with closest match.
 *  can be zero is there is no match.
 * @param insertpt: insert location for dname, if not found.
 * @return: 0 if no exact match.
 */
static int
compress_tree_search(struct compress_tree_node** tree, uint8_t* dname,
  int labs, struct compress_tree_node** match, int* matchlabels,
  struct compress_tree_node*** insertpt)
{
  int c, n, closen=0;
  struct compress_tree_node* p = *tree;
  struct compress_tree_node* close = 0;
  struct compress_tree_node** prev = tree;
  while(p) {
    if((c = dname_lab_cmp(dname, labs, p->dname, p->labs, &n)) 
      == 0) {
      *matchlabels = n;
      *match = p;
      return 1;
    }
    if(c<0) {
      prev = &p->left;
      p = p->left;
    } else {
      closen = n;
      close = p; /* p->dname is smaller than dname */
      prev = &p->right;
      p = p->right;
    }
  }
  *insertpt = prev;
  *matchlabels = closen;
  *match = close;
  return 0;
}

/**
 * Lookup a domain name in compression tree.
 * @param tree: root of tree (not the node with '.').
 * @param dname: pointer to uncompressed dname.
 * @param labs: number of labels in domain name.
 * @param insertpt: insert location for dname, if not found.
 * @return: 0 if not found or compress treenode with best compression.
 */
static struct compress_tree_node*
compress_tree_lookup(struct compress_tree_node** tree, uint8_t* dname,
  int labs, struct compress_tree_node*** insertpt)
{
  struct compress_tree_node* p;
  int m;
  if(labs <= 1)
    return 0; /* do not compress root node */
  if(compress_tree_search(tree, dname, labs, &p, &m, insertpt)) {
    /* exact match */
    return p;
  }
  /* return some ancestor of p that compresses well. */
  if(m>1) {
    /* www.example.com. (labs=4) matched foo.example.com.(labs=4)
     * then matchcount = 3. need to go up. */
    while(p && p->labs > m)
      p = p->parent;
    return p;
  }
  return 0;
}

/**
 * Create node for domain name compression tree.
 * @param dname: pointer to uncompressed dname (stored in tree).
 * @param labs: number of labels in dname.
 * @param offset: offset into packet for dname.
 * @param region: how to allocate memory for new node.
 * @return new node or 0 on malloc failure.
 */
static struct compress_tree_node*
compress_tree_newnode(uint8_t* dname, int labs, size_t offset, 
  struct regional* region)
{
  struct compress_tree_node* n = (struct compress_tree_node*)
    regional_alloc(region, sizeof(struct compress_tree_node));
  if(!n) return 0;
  n->left = 0;
  n->right = 0;
  n->parent = 0;
  n->dname = dname;
  n->labs = labs;
  n->offset = offset;
  return n;
}

/**
 * Store domain name and ancestors into compression tree.
 * @param dname: pointer to uncompressed dname (stored in tree).
 * @param labs: number of labels in dname.
 * @param offset: offset into packet for dname.
 * @param region: how to allocate memory for new node.
 * @param closest: match from previous lookup, used to compress dname.
 *  may be NULL if no previous match.
 *  if the tree has an ancestor of dname already, this must be it.
 * @param insertpt: where to insert the dname in tree. 
 * @return: 0 on memory error.
 */
static int
compress_tree_store(uint8_t* dname, int labs, size_t offset, 
  struct regional* region, struct compress_tree_node* closest, 
  struct compress_tree_node** insertpt)
{
  uint8_t lablen;
  struct compress_tree_node* newnode;
  struct compress_tree_node* prevnode = NULL;
  int uplabs = labs-1; /* does not store root in tree */
  if(closest) uplabs = labs - closest->labs;
  log_assert(uplabs >= 0);
  /* algorithms builds up a vine of dname-labels to hang into tree */
  while(uplabs--) {
    if(offset > PTR_MAX_OFFSET) {
      /* insertion failed, drop vine */
      return 1; /* compression pointer no longer useful */
    }
    if(!(newnode = compress_tree_newnode(dname, labs, offset, 
      region))) {
      /* insertion failed, drop vine */
      return 0;
    }

    if(prevnode) {
      /* chain nodes together, last one has one label more,
       * so is larger than newnode, thus goes right. */
      newnode->right = prevnode;
      prevnode->parent = newnode;
    }

    /* next label */
    lablen = *dname++;
    dname += lablen;
    offset += lablen+1;
    prevnode = newnode;
    labs--;
  }
  /* if we have a vine, hang the vine into the tree */
  if(prevnode) {
    *insertpt = prevnode;
    prevnode->parent = closest;
  }
  return 1;
}

/** compress a domain name */
static int
write_compressed_dname(sldns_buffer* pkt, uint8_t* dname, int labs,
  struct compress_tree_node* p)
{
  /* compress it */
  int labcopy = labs - p->labs;
  uint8_t lablen;
  uint16_t ptr;

  if(labs == 1) {
    /* write root label */
    if(sldns_buffer_remaining(pkt) < 1)
      return 0;
    sldns_buffer_write_u8(pkt, 0);
    return 1;
  }

  /* copy the first couple of labels */
  while(labcopy--) {
    lablen = *dname++;
    if(sldns_buffer_remaining(pkt) < (size_t)lablen+1)
      return 0;
    sldns_buffer_write_u8(pkt, lablen);
    sldns_buffer_write(pkt, dname, lablen);
    dname += lablen;
  }
  /* insert compression ptr */
  if(sldns_buffer_remaining(pkt) < 2)
    return 0;
  ptr = PTR_CREATE(p->offset);
  sldns_buffer_write_u16(pkt, ptr);
  return 1;
}

/** compress owner name of RR, return RETVAL_OUTMEM RETVAL_TRUNC */
static int
compress_owner(struct ub_packed_rrset_key* key, sldns_buffer* pkt,
  struct regional* region, struct compress_tree_node** tree,
  size_t owner_pos, uint16_t* owner_ptr, int owner_labs,
  size_t* compress_count)
{
  struct compress_tree_node* p;
  struct compress_tree_node** insertpt = NULL;
  if(!*owner_ptr) {
    /* compress first time dname */
    if(*compress_count < MAX_COMPRESSION_PER_MESSAGE &&
      (p = compress_tree_lookup(tree, key->rk.dname,
      owner_labs, &insertpt))) {
      if(p->labs == owner_labs) 
        /* avoid ptr chains, since some software is
         * not capable of decoding ptr after a ptr. */
        *owner_ptr = htons(PTR_CREATE(p->offset));
      if(!write_compressed_dname(pkt, key->rk.dname, 
        owner_labs, p))
        return RETVAL_TRUNC;
      (*compress_count)++;
      /* check if typeclass+4 ttl + rdatalen is available */
      if(sldns_buffer_remaining(pkt) < 4+4+2)
        return RETVAL_TRUNC;
    } else {
      /* no compress */
      if(sldns_buffer_remaining(pkt) < key->rk.dname_len+4+4+2)
        return RETVAL_TRUNC;
      sldns_buffer_write(pkt, key->rk.dname, 
        key->rk.dname_len);
      if(owner_pos <= PTR_MAX_OFFSET)
        *owner_ptr = htons(PTR_CREATE(owner_pos));
    }
    if(*compress_count < MAX_COMPRESSION_PER_MESSAGE &&
      !compress_tree_store(key->rk.dname, owner_labs,
      owner_pos, region, p, insertpt))
      return RETVAL_OUTMEM;
  } else {
    /* always compress 2nd-further RRs in RRset */
    if(owner_labs == 1) {
      if(sldns_buffer_remaining(pkt) < 1+4+4+2) 
        return RETVAL_TRUNC;
      sldns_buffer_write_u8(pkt, 0);
    } else {
      if(sldns_buffer_remaining(pkt) < 2+4+4+2) 
        return RETVAL_TRUNC;
      sldns_buffer_write(pkt, owner_ptr, 2);
    }
  }
  return RETVAL_OK;
}

/** compress any domain name to the packet, return RETVAL_* */
static int
compress_any_dname(uint8_t* dname, sldns_buffer* pkt, int labs,
  struct regional* region, struct compress_tree_node** tree,
  size_t* compress_count)
{
  struct compress_tree_node* p;
  struct compress_tree_node** insertpt = NULL;
  size_t pos = sldns_buffer_position(pkt);
  if(*compress_count < MAX_COMPRESSION_PER_MESSAGE &&
    (p = compress_tree_lookup(tree, dname, labs, &insertpt))) {
    if(!write_compressed_dname(pkt, dname, labs, p))
      return RETVAL_TRUNC;
    (*compress_count)++;
  } else {
    if(!dname_buffer_write(pkt, dname))
      return RETVAL_TRUNC;
  }
  if(*compress_count < MAX_COMPRESSION_PER_MESSAGE &&
    !compress_tree_store(dname, labs, pos, region, p, insertpt))
    return RETVAL_OUTMEM;
  return RETVAL_OK;
}

/** return true if type needs domain name compression in rdata */
static const sldns_rr_descriptor*
type_rdata_compressible(struct ub_packed_rrset_key* key)
{
  uint16_t t = ntohs(key->rk.type);
  if(sldns_rr_descript(t) && 
    sldns_rr_descript(t)->_compress == LDNS_RR_COMPRESS)
    return sldns_rr_descript(t);
  return 0;
}

/** compress domain names in rdata, return RETVAL_* */
static int
compress_rdata(sldns_buffer* pkt, uint8_t* rdata, size_t todolen,
  struct regional* region, struct compress_tree_node** tree,
  const sldns_rr_descriptor* desc, size_t* compress_count)
{
  int labs, r, rdf = 0;
  size_t dname_len, len, pos = sldns_buffer_position(pkt);
  uint8_t count = desc->_dname_count;

  sldns_buffer_skip(pkt, 2); /* rdata len fill in later */
  /* space for rdatalen checked for already */
  rdata += 2;
  todolen -= 2;
  while(todolen > 0 && count) {
    switch(desc->_wireformat[rdf]) {
    case LDNS_RDF_TYPE_DNAME:
      labs = dname_count_size_labels(rdata, &dname_len);
      if((r=compress_any_dname(rdata, pkt, labs, region,
        tree, compress_count)) != RETVAL_OK)
        return r;
      rdata += dname_len;
      todolen -= dname_len;
      count--;
      len = 0;
      break;
    case LDNS_RDF_TYPE_STR:
      len = *rdata + 1;
      break;
    default:
      len = get_rdf_size(desc->_wireformat[rdf]);
    }
    if(len) {
      /* copy over */
      if(sldns_buffer_remaining(pkt) < len)
        return RETVAL_TRUNC;
      sldns_buffer_write(pkt, rdata, len);
      todolen -= len;
      rdata += len;
    }
    rdf++;
  }
  /* copy remainder */
  if(todolen > 0) {
    if(sldns_buffer_remaining(pkt) < todolen)
      return RETVAL_TRUNC;
    sldns_buffer_write(pkt, rdata, todolen);
  }

  /* set rdata len */
  sldns_buffer_write_u16_at(pkt, pos, sldns_buffer_position(pkt)-pos-2);
  return RETVAL_OK;
}

/** Returns true if RR type should be included */
static int
rrset_belongs_in_reply(sldns_pkt_section s, uint16_t rrtype, uint16_t qtype, 
  int dnssec)
{
  if(dnssec)
    return 1;
  /* skip non DNSSEC types, except if directly queried for */
  if(s == LDNS_SECTION_ANSWER) {
    if(qtype == LDNS_RR_TYPE_ANY || qtype == rrtype)
      return 1;
  }
  /* check DNSSEC-ness */
  switch(rrtype) {
    case LDNS_RR_TYPE_SIG:
    case LDNS_RR_TYPE_KEY:
    case LDNS_RR_TYPE_NXT:
    case LDNS_RR_TYPE_DS:
    case LDNS_RR_TYPE_RRSIG:
    case LDNS_RR_TYPE_NSEC:
    case LDNS_RR_TYPE_DNSKEY:
    case LDNS_RR_TYPE_NSEC3:
    case LDNS_RR_TYPE_NSEC3PARAMS:
      return 0;
  }
  return 1;
}

/** store rrset in buffer in wireformat, return RETVAL_* */
static int
packed_rrset_encode(struct ub_packed_rrset_key* key, sldns_buffer* pkt, 
  uint16_t* num_rrs, time_t timenow, struct regional* region,
  int do_data, int do_sig, struct compress_tree_node** tree,
  sldns_pkt_section s, uint16_t qtype, int dnssec, size_t rr_offset,
  size_t* compress_count)
{
  size_t i, j, owner_pos;
  int r, owner_labs;
  uint16_t owner_ptr = 0;
  time_t adjust = 0;
  struct packed_rrset_data* data = (struct packed_rrset_data*)
    key->entry.data;
  
  /* does this RR type belong in the answer? */
  if(!rrset_belongs_in_reply(s, ntohs(key->rk.type), qtype, dnssec))
    return RETVAL_OK;

  owner_labs = dname_count_labels(key->rk.dname);
  owner_pos = sldns_buffer_position(pkt);

  /** Determine relative time adjustment for TTL values.
   * For an rrset with a fixed TTL, use the rrset's TTL as given. */
  if((key->rk.flags & PACKED_RRSET_FIXEDTTL) != 0)
    adjust = 0;
  else
    adjust = SERVE_ORIGINAL_TTL ? data->ttl_add : timenow;

  if(do_data) {
    const sldns_rr_descriptor* c = type_rdata_compressible(key);
    for(i=0; i<data->count; i++) {
      /* rrset roundrobin */
      j = (i + rr_offset) % data->count;
      if((r=compress_owner(key, pkt, region, tree,
        owner_pos, &owner_ptr, owner_labs,
        compress_count)) != RETVAL_OK)
        return r;
      sldns_buffer_write(pkt, &key->rk.type, 2);
      sldns_buffer_write(pkt, &key->rk.rrset_class, 2);
      if(key->rk.flags & PACKED_RRSET_UPSTREAM_0TTL) {
        sldns_buffer_write_u32(pkt, 0);
      } else if(adjust == 0) {
        sldns_buffer_write_u32(pkt, data->rr_ttl[j]);
      } else if(TTL_IS_EXPIRED(data->rr_ttl[j], adjust)) {
        sldns_buffer_write_u32(pkt,
          EXPIRED_REPLY_TTL_CALC(
              data->rr_ttl[j], data->ttl_add));
      } else {
        sldns_buffer_write_u32(pkt,
          data->rr_ttl[j] - adjust);
      }
      if(c) {
        if((r=compress_rdata(pkt, data->rr_data[j],
          data->rr_len[j], region, tree, c,
          compress_count)) != RETVAL_OK)
          return r;
      } else {
        if(sldns_buffer_remaining(pkt) < data->rr_len[j])
          return RETVAL_TRUNC;
        sldns_buffer_write(pkt, data->rr_data[j],
          data->rr_len[j]);
      }
    }
  }
  /* insert rrsigs */
  if(do_sig && dnssec) {
    size_t total = data->count+data->rrsig_count;
    for(i=data->count; i<total; i++) {
      if(owner_ptr && owner_labs != 1) {
        if(sldns_buffer_remaining(pkt) <
          2+4+4+data->rr_len[i]) 
          return RETVAL_TRUNC;
        sldns_buffer_write(pkt, &owner_ptr, 2);
      } else {
        if((r=compress_any_dname(key->rk.dname,
          pkt, owner_labs, region, tree,
          compress_count)) != RETVAL_OK)
          return r;
        if(sldns_buffer_remaining(pkt) < 
          4+4+data->rr_len[i])
          return RETVAL_TRUNC;
      }
      sldns_buffer_write_u16(pkt, LDNS_RR_TYPE_RRSIG);
      sldns_buffer_write(pkt, &key->rk.rrset_class, 2);
      if(key->rk.flags & PACKED_RRSET_UPSTREAM_0TTL) {
        sldns_buffer_write_u32(pkt, 0);
      } else if(adjust == 0) {
        sldns_buffer_write_u32(pkt, data->rr_ttl[i]);
      } else if(TTL_IS_EXPIRED(data->rr_ttl[i], adjust)) {
        sldns_buffer_write_u32(pkt,
          EXPIRED_REPLY_TTL_CALC(
              data->rr_ttl[i], data->ttl_add));
      } else {
        sldns_buffer_write_u32(pkt,
          data->rr_ttl[i] - adjust);
      }
      /* rrsig rdata cannot be compressed, perform 100+ byte
       * memcopy. */
      sldns_buffer_write(pkt, data->rr_data[i],
        data->rr_len[i]);
    }
  }
  /* change rrnum only after we are sure it fits */
  if(do_data)
    *num_rrs += data->count;
  if(do_sig && dnssec)
    *num_rrs += data->rrsig_count;

  return RETVAL_OK;
}

/** store msg section in wireformat buffer, return RETVAL_* */
static int
insert_section(struct reply_info* rep, size_t num_rrsets, uint16_t* num_rrs,
  sldns_buffer* pkt, size_t rrsets_before, time_t timenow, 
  struct regional* region, struct compress_tree_node** tree,
  sldns_pkt_section s, uint16_t qtype, int dnssec, size_t rr_offset,
  size_t* compress_count)
{
  int r;
  size_t i, setstart;
  /* we now allow this function to be called multiple times for the
   * same section, incrementally updating num_rrs.  The caller is
   * responsible for initializing it (which is the case in the current
   * implementation). */

  if(s != LDNS_SECTION_ADDITIONAL) {
    if(s == LDNS_SECTION_ANSWER && qtype == LDNS_RR_TYPE_ANY)
      dnssec = 1; /* include all types in ANY answer */
      for(i=0; i<num_rrsets; i++) {
      setstart = sldns_buffer_position(pkt);
      if((r=packed_rrset_encode(rep->rrsets[rrsets_before+i], 
        pkt, num_rrs, timenow, region, 1, 1, tree,
        s, qtype, dnssec, rr_offset, compress_count))
        != RETVAL_OK) {
        /* Bad, but if due to size must set TC bit */
        /* trim off the rrset neatly. */
        sldns_buffer_set_position(pkt, setstart);
        return r;
      }
    }
  } else {
      for(i=0; i<num_rrsets; i++) {
      setstart = sldns_buffer_position(pkt);
      if((r=packed_rrset_encode(rep->rrsets[rrsets_before+i], 
        pkt, num_rrs, timenow, region, 1, 0, tree,
        s, qtype, dnssec, rr_offset, compress_count))
        != RETVAL_OK) {
        sldns_buffer_set_position(pkt, setstart);
        return r;
      }
    }
    if(dnssec)
        for(i=0; i<num_rrsets; i++) {
      setstart = sldns_buffer_position(pkt);
      if((r=packed_rrset_encode(rep->rrsets[rrsets_before+i], 
        pkt, num_rrs, timenow, region, 0, 1, tree,
        s, qtype, dnssec, rr_offset, compress_count))
        != RETVAL_OK) {
        sldns_buffer_set_position(pkt, setstart);
        return r;
      }
      }
  }
  return RETVAL_OK;
}

/** store query section in wireformat buffer, return RETVAL */
static int
insert_query(struct query_info* qinfo, struct compress_tree_node** tree, 
  sldns_buffer* buffer, struct regional* region)
{
  uint8_t* qname = qinfo->local_alias ?
    qinfo->local_alias->rrset->rk.dname : qinfo->qname;
  size_t qname_len = qinfo->local_alias ?
    qinfo->local_alias->rrset->rk.dname_len : qinfo->qname_len;
  if(sldns_buffer_remaining(buffer) < 
    qinfo->qname_len+sizeof(uint16_t)*2)
    return RETVAL_TRUNC; /* buffer too small */
  /* the query is the first name inserted into the tree */
  if(!compress_tree_store(qname, dname_count_labels(qname),
    sldns_buffer_position(buffer), region, NULL, tree))
    return RETVAL_OUTMEM;
  if(sldns_buffer_current(buffer) == qname)
    sldns_buffer_skip(buffer, (ssize_t)qname_len);
  else  sldns_buffer_write(buffer, qname, qname_len);
  sldns_buffer_write_u16(buffer, qinfo->qtype);
  sldns_buffer_write_u16(buffer, qinfo->qclass);
  return RETVAL_OK;
}

static int
positive_answer(struct reply_info* rep, uint16_t qtype) {
  size_t i;
  if (FLAGS_GET_RCODE(rep->flags) != LDNS_RCODE_NOERROR)
    return 0;

  for(i=0;i<rep->an_numrrsets; i++) {
    if(ntohs(rep->rrsets[i]->rk.type) == qtype) {
      /* for priming queries, type NS, include addresses */
      if(qtype == LDNS_RR_TYPE_NS)
        return 0;
      /* in case it is a wildcard with DNSSEC, there will
       * be NSEC/NSEC3 records in the authority section
       * that we cannot remove */
      for(i=rep->an_numrrsets; i<rep->an_numrrsets+
        rep->ns_numrrsets; i++) {
        if(ntohs(rep->rrsets[i]->rk.type) ==
          LDNS_RR_TYPE_NSEC ||
           ntohs(rep->rrsets[i]->rk.type) ==
            LDNS_RR_TYPE_NSEC3)
          return 0;
      }
      return 1;
    }
  }
  return 0;
}

static int
negative_answer(struct reply_info* rep) {
  size_t i;
  int ns_seen = 0;
  if(FLAGS_GET_RCODE(rep->flags) == LDNS_RCODE_NXDOMAIN)
    return 1;
  if(FLAGS_GET_RCODE(rep->flags) == LDNS_RCODE_NOERROR &&
    rep->an_numrrsets != 0)
    return 0; /* positive */
  if(FLAGS_GET_RCODE(rep->flags) != LDNS_RCODE_NOERROR &&
    FLAGS_GET_RCODE(rep->flags) != LDNS_RCODE_NXDOMAIN)
    return 0;
  for(i=rep->an_numrrsets; i<rep->an_numrrsets+rep->ns_numrrsets; i++){
    if(ntohs(rep->rrsets[i]->rk.type) == LDNS_RR_TYPE_SOA)
      return 1;
    if(ntohs(rep->rrsets[i]->rk.type) == LDNS_RR_TYPE_NS)
      ns_seen = 1;
  }
  if(ns_seen) return 0; /* could be referral, NS, but no SOA */
  return 1;
}

int
reply_info_encode(struct query_info* qinfo, struct reply_info* rep,
  uint16_t id, uint16_t flags, sldns_buffer* buffer, time_t timenow,
  struct regional* region, uint16_t udpsize, int dnssec, int minimise)
{
  uint16_t ancount=0, nscount=0, arcount=0;
  struct compress_tree_node* tree = 0;
  int r;
  size_t rr_offset;
  size_t compress_count=0;

  sldns_buffer_clear(buffer);
  if(udpsize < sldns_buffer_limit(buffer))
    sldns_buffer_set_limit(buffer, udpsize);
  if(sldns_buffer_remaining(buffer) < LDNS_HEADER_SIZE)
    return 0;

  sldns_buffer_write(buffer, &id, sizeof(uint16_t));
  sldns_buffer_write_u16(buffer, flags);
  sldns_buffer_write_u16(buffer, rep->qdcount);
  /* set an, ns, ar counts to zero in case of small packets */
  sldns_buffer_write(buffer, "\000\000\000\000\000\000", 6);

  /* insert query section */
  if(rep->qdcount) {
    if((r=insert_query(qinfo, &tree, buffer, region)) !=
      RETVAL_OK) {
      if(r == RETVAL_TRUNC) {
        /* create truncated message */
        sldns_buffer_write_u16_at(buffer, 4, 0);
        LDNS_TC_SET(sldns_buffer_begin(buffer));
        sldns_buffer_flip(buffer);
        return 1;
      }
      return 0;
    }
  }
  /* roundrobin offset. using query id for random number.  With ntohs
   * for different roundrobins for sequential id client senders. */
  rr_offset = RRSET_ROUNDROBIN?ntohs(id)+(timenow?timenow:time(NULL)):0;

  /* "prepend" any local alias records in the answer section if this
   * response is supposed to be authoritative.  Currently it should
   * be a single CNAME record (sanity-checked in worker_handle_request())
   * but it can be extended if and when we support more variations of
   * aliases. */
  if(qinfo->local_alias && (flags & BIT_AA)) {
    struct reply_info arep;
    time_t timezero = 0; /* to use the 'authoritative' TTL */
    memset(&arep, 0, sizeof(arep));
    arep.flags = rep->flags;
    arep.an_numrrsets = 1;
    arep.rrset_count = 1;
    arep.rrsets = &qinfo->local_alias->rrset;
    if((r=insert_section(&arep, 1, &ancount, buffer, 0,
      timezero, region, &tree, LDNS_SECTION_ANSWER,
      qinfo->qtype, dnssec, rr_offset, &compress_count)) != RETVAL_OK) {
      if(r == RETVAL_TRUNC) {
        /* create truncated message */
        sldns_buffer_write_u16_at(buffer, 6, ancount);
        LDNS_TC_SET(sldns_buffer_begin(buffer));
        sldns_buffer_flip(buffer);
        return 1;
      }
      return 0;
    }
  }

  /* insert answer section */
  if((r=insert_section(rep, rep->an_numrrsets, &ancount, buffer,
    0, timenow, region, &tree, LDNS_SECTION_ANSWER, qinfo->qtype,
    dnssec, rr_offset, &compress_count)) != RETVAL_OK) {
    if(r == RETVAL_TRUNC) {
      /* create truncated message */
      sldns_buffer_write_u16_at(buffer, 6, ancount);
      LDNS_TC_SET(sldns_buffer_begin(buffer));
      sldns_buffer_flip(buffer);
      return 1;
    }
    return 0;
  }
  sldns_buffer_write_u16_at(buffer, 6, ancount);

  /* if response is positive answer, auth/add sections are not required */
  if( ! (minimise && positive_answer(rep, qinfo->qtype)) ) {
    /* insert auth section */
    if((r=insert_section(rep, rep->ns_numrrsets, &nscount, buffer,
      rep->an_numrrsets, timenow, region, &tree,
      LDNS_SECTION_AUTHORITY, qinfo->qtype,
      dnssec, rr_offset, &compress_count)) != RETVAL_OK) {
      if(r == RETVAL_TRUNC) {
        /* create truncated message */
        sldns_buffer_write_u16_at(buffer, 8, nscount);
        LDNS_TC_SET(sldns_buffer_begin(buffer));
        sldns_buffer_flip(buffer);
        return 1;
      }
      return 0;
    }
    sldns_buffer_write_u16_at(buffer, 8, nscount);

    if(! (minimise && negative_answer(rep))) {
      /* insert add section */
      if((r=insert_section(rep, rep->ar_numrrsets, &arcount, buffer,
        rep->an_numrrsets + rep->ns_numrrsets, timenow, region,
        &tree, LDNS_SECTION_ADDITIONAL, qinfo->qtype,
        dnssec, rr_offset, &compress_count)) != RETVAL_OK) {
        if(r == RETVAL_TRUNC) {
          /* no need to set TC bit, this is the additional */
          sldns_buffer_write_u16_at(buffer, 10, arcount);
          sldns_buffer_flip(buffer);
          return 1;
        }
        return 0;
      }
      sldns_buffer_write_u16_at(buffer, 10, arcount);
    }
  }
  sldns_buffer_flip(buffer);
  return 1;
}

uint16_t
calc_edns_field_size(struct edns_data* edns)
{
  size_t rdatalen = 0;
  struct edns_option* opt;
  if(!edns || !edns->edns_present)
    return 0;
  for(opt = edns->opt_list_inplace_cb_out; opt; opt = opt->next) {
    rdatalen += 4 + opt->opt_len;
  }
  for(opt = edns->opt_list_out; opt; opt = opt->next) {
    rdatalen += 4 + opt->opt_len;
  }
  /* domain root '.' + type + class + ttl + rdatalen */
  return 1 + 2 + 2 + 4 + 2 + rdatalen;
}

uint16_t
calc_edns_option_size(struct edns_data* edns, uint16_t code)
{
  size_t rdatalen = 0;
  struct edns_option* opt;
  if(!edns || !edns->edns_present)
    return 0;
  for(opt = edns->opt_list_inplace_cb_out; opt; opt = opt->next) {
    if(opt->opt_code == code)
      rdatalen += 4 + opt->opt_len;
  }
  for(opt = edns->opt_list_out; opt; opt = opt->next) {
    if(opt->opt_code == code)
      rdatalen += 4 + opt->opt_len;
  }
  return rdatalen;
}

uint16_t
calc_ede_option_size(struct edns_data* edns, uint16_t* txt_size)
{
  size_t rdatalen = 0;
  struct edns_option* opt;
  *txt_size = 0;
  if(!edns || !edns->edns_present)
    return 0;
  for(opt = edns->opt_list_inplace_cb_out; opt; opt = opt->next) {
    if(opt->opt_code == LDNS_EDNS_EDE) {
      rdatalen += 4 + opt->opt_len;
      if(opt->opt_len > 2) *txt_size += opt->opt_len - 2;
      if(opt->opt_len >= 2 && sldns_read_uint16(
        opt->opt_data) == LDNS_EDE_OTHER) {
        *txt_size += 4 + 2;
      }
    }
  }
  for(opt = edns->opt_list_out; opt; opt = opt->next) {
    if(opt->opt_code == LDNS_EDNS_EDE) {
      rdatalen += 4 + opt->opt_len;
      if(opt->opt_len > 2) *txt_size += opt->opt_len - 2;
      if(opt->opt_len >= 2 && sldns_read_uint16(
        opt->opt_data) == LDNS_EDE_OTHER) {
        *txt_size += 4 + 2;
      }
    }
  }
  return rdatalen;
}

/* Trims the EDE OPTION-DATA to not include any EXTRA-TEXT data.
 * Also removes any LDNS_EDE_OTHER options from the list since they are useless
 * without the extra text. */
static void
ede_trim_text(struct edns_option** list)
{
  struct edns_option* curr, *prev = NULL;
  if(!list || !(*list)) return;
  /* Unlink and repoint if LDNS_EDE_OTHER are first in list */
  while(list && *list && (*list)->opt_code == LDNS_EDNS_EDE
    && (*list)->opt_len >= 2
    && sldns_read_uint16((*list)->opt_data) == LDNS_EDE_OTHER ) {
    *list = (*list)->next;
  }
  if(!list || !(*list)) return;
  curr = *list;
  while(curr) {
    if(curr->opt_code == LDNS_EDNS_EDE) {
      if(curr->opt_len >= 2 && sldns_read_uint16(
        curr->opt_data) == LDNS_EDE_OTHER) {
        /* LDNS_EDE_OTHER cannot be the first option in
         * this while, so prev is always initialized at
         * this point from the other branches;
         * cut this option off */
        prev->next = curr->next;
        curr = curr->next;
      } else if(curr->opt_len > 2) {
        /* trim this option's EXTRA-TEXT */
        curr->opt_len = 2;
        prev = curr;
        curr = curr->next;
      } else {
        prev = curr;
        curr = curr->next;
      }
    } else {
      /* continue */
      prev = curr;
      curr = curr->next;
    }
  }
}

static void
attach_edns_record_max_msg_sz(sldns_buffer* pkt, struct edns_data* edns,
  uint16_t max_msg_sz)
{
  size_t len;
  size_t rdatapos;
  struct edns_option* opt;
  struct edns_option* padding_option = NULL;
  /* inc additional count */
  sldns_buffer_write_u16_at(pkt, 10,
    sldns_buffer_read_u16_at(pkt, 10) + 1);
  len = sldns_buffer_limit(pkt);
  sldns_buffer_clear(pkt);
  sldns_buffer_set_position(pkt, len);
  /* write EDNS record */
  sldns_buffer_write_u8(pkt, 0); /* '.' label */
  sldns_buffer_write_u16(pkt, LDNS_RR_TYPE_OPT); /* type */
  sldns_buffer_write_u16(pkt, edns->udp_size); /* class */
  sldns_buffer_write_u8(pkt, edns->ext_rcode); /* ttl */
  sldns_buffer_write_u8(pkt, edns->edns_version);
  sldns_buffer_write_u16(pkt, edns->bits);
  rdatapos = sldns_buffer_position(pkt);
  sldns_buffer_write_u16(pkt, 0); /* rdatalen */
  /* write rdata */
  for(opt=edns->opt_list_inplace_cb_out; opt; opt=opt->next) {
    if (opt->opt_code == LDNS_EDNS_PADDING) {
      padding_option = opt;
      continue;
    }
    sldns_buffer_write_u16(pkt, opt->opt_code);
    sldns_buffer_write_u16(pkt, opt->opt_len);
    if(opt->opt_len != 0)
      sldns_buffer_write(pkt, opt->opt_data, opt->opt_len);
  }
  for(opt=edns->opt_list_out; opt; opt=opt->next) {
    if (opt->opt_code == LDNS_EDNS_PADDING) {
      padding_option = opt;
      continue;
    }
    sldns_buffer_write_u16(pkt, opt->opt_code);
    sldns_buffer_write_u16(pkt, opt->opt_len);
    if(opt->opt_len != 0)
      sldns_buffer_write(pkt, opt->opt_data, opt->opt_len);
  }
  if (padding_option && edns->padding_block_size ) {
    size_t pad_pos = sldns_buffer_position(pkt);
    size_t msg_sz = ((pad_pos + 3) / edns->padding_block_size + 1)
                                   * edns->padding_block_size;
    size_t pad_sz;
    
    if (msg_sz > max_msg_sz)
      msg_sz = max_msg_sz;

    /* By use of calc_edns_field_size, calling functions should
     * have made sure that there is enough space for at least a
     * zero sized padding option.
     */
    log_assert(pad_pos + 4 <= msg_sz);

    pad_sz = msg_sz - pad_pos - 4;
    sldns_buffer_write_u16(pkt, LDNS_EDNS_PADDING);
    sldns_buffer_write_u16(pkt, pad_sz);
    if (pad_sz) {
      memset(sldns_buffer_current(pkt), 0, pad_sz);
      sldns_buffer_skip(pkt, pad_sz);
    }
  }
  sldns_buffer_write_u16_at(pkt, rdatapos, 
      sldns_buffer_position(pkt)-rdatapos-2);
  sldns_buffer_flip(pkt);
}

void
attach_edns_record(sldns_buffer* pkt, struct edns_data* edns)
{
  if(!edns || !edns->edns_present)
    return;
  attach_edns_record_max_msg_sz(pkt, edns, edns->udp_size);
}

int
reply_info_answer_encode(struct query_info* qinf, struct reply_info* rep,
  uint16_t id, uint16_t qflags, sldns_buffer* pkt, time_t timenow,
  int cached, struct regional* region, uint16_t udpsize,
  struct edns_data* edns, int dnssec, int secure)
{
  uint16_t flags;
  unsigned int attach_edns = 0;
  uint16_t edns_field_size, ede_size, ede_txt_size;

  if(!cached || rep->authoritative) {
    /* original flags, copy RD and CD bits from query. */
    flags = rep->flags | (qflags & (BIT_RD|BIT_CD)); 
  } else {
    /* remove AA bit, copy RD and CD bits from query. */
    flags = (rep->flags & ~BIT_AA) | (qflags & (BIT_RD|BIT_CD)); 
  }
  if(secure && (dnssec || (qflags&BIT_AD)))
    flags |= BIT_AD;
  /* restore AA bit if we have a local alias and the response can be
   * authoritative.  Also clear AD bit if set as the local data is the
   * primary answer. */
  if(qinf->local_alias &&
    (FLAGS_GET_RCODE(rep->flags) == LDNS_RCODE_NOERROR ||
    FLAGS_GET_RCODE(rep->flags) == LDNS_RCODE_NXDOMAIN)) {
    flags |= BIT_AA;
    flags &= ~BIT_AD;
  }
  log_assert((flags & BIT_QR)); /* QR bit must be on in our replies */
  if(udpsize < LDNS_HEADER_SIZE)
    return 0;
  /* currently edns does not change during calculations;
   * calculate sizes once here */
  edns_field_size = calc_edns_field_size(edns);
  ede_size = calc_ede_option_size(edns, &ede_txt_size);
  if(sldns_buffer_capacity(pkt) < udpsize)
    udpsize = sldns_buffer_capacity(pkt);
  if(!edns || !edns->edns_present) {
    attach_edns = 0;
  /* EDEs are optional, try to fit anything else before them */
  } else if(udpsize < LDNS_HEADER_SIZE + edns_field_size - ede_size) {
    /* packet too small to contain edns, omit it. */
    attach_edns = 0;
  } else {
    /* reserve space for edns record */
    attach_edns = (unsigned int)edns_field_size - ede_size;
  }

  if(!reply_info_encode(qinf, rep, id, flags, pkt, timenow, region,
    udpsize - attach_edns, dnssec, MINIMAL_RESPONSES)) {
    log_err("reply encode: out of memory");
    return 0;
  }
  if(attach_edns) {
    if(udpsize >= sldns_buffer_limit(pkt) + edns_field_size)
      attach_edns_record_max_msg_sz(pkt, edns, udpsize);
    else if(udpsize >= sldns_buffer_limit(pkt) + edns_field_size - ede_txt_size) {
      ede_trim_text(&edns->opt_list_inplace_cb_out);
      ede_trim_text(&edns->opt_list_out);
      attach_edns_record_max_msg_sz(pkt, edns, udpsize);
    } else if(udpsize >= sldns_buffer_limit(pkt) + edns_field_size - ede_size) {
      edns_opt_list_remove(&edns->opt_list_inplace_cb_out, LDNS_EDNS_EDE);
      edns_opt_list_remove(&edns->opt_list_out, LDNS_EDNS_EDE);
      attach_edns_record_max_msg_sz(pkt, edns, udpsize);
    }
  }
  return 1;
}

void 
qinfo_query_encode(sldns_buffer* pkt, struct query_info* qinfo)
{
  uint16_t flags = 0; /* QUERY, NOERROR */
  const uint8_t* qname = qinfo->local_alias ?
    qinfo->local_alias->rrset->rk.dname : qinfo->qname;
  size_t qname_len = qinfo->local_alias ?
    qinfo->local_alias->rrset->rk.dname_len : qinfo->qname_len;
  sldns_buffer_clear(pkt);
  log_assert(sldns_buffer_remaining(pkt) >= 12+255+4/*max query*/);
  sldns_buffer_skip(pkt, 2); /* id done later */
  sldns_buffer_write_u16(pkt, flags);
  sldns_buffer_write_u16(pkt, 1); /* query count */
  sldns_buffer_write(pkt, "\000\000\000\000\000\000", 6); /* counts */
  sldns_buffer_write(pkt, qname, qname_len);
  sldns_buffer_write_u16(pkt, qinfo->qtype);
  sldns_buffer_write_u16(pkt, qinfo->qclass);
  sldns_buffer_flip(pkt);
}

void
extended_error_encode(sldns_buffer* buf, uint16_t rcode,
  struct query_info* qinfo, uint16_t qid, uint16_t qflags,
  uint16_t xflags, struct edns_data* edns)
{
  uint16_t flags;

  sldns_buffer_clear(buf);
  sldns_buffer_write(buf, &qid, sizeof(uint16_t));
  flags = (uint16_t)(BIT_QR | BIT_RA | (rcode & 0xF)); /* QR and retcode*/
  flags |= xflags;
  flags |= (qflags & (BIT_RD|BIT_CD)); /* copy RD and CD bit */
  sldns_buffer_write_u16(buf, flags);
  if(qinfo) flags = 1;
  else  flags = 0;
  sldns_buffer_write_u16(buf, flags);
  flags = 0;
  sldns_buffer_write(buf, &flags, sizeof(uint16_t));
  sldns_buffer_write(buf, &flags, sizeof(uint16_t));
  sldns_buffer_write(buf, &flags, sizeof(uint16_t));
  if(qinfo) {
    const uint8_t* qname = qinfo->local_alias ?
      qinfo->local_alias->rrset->rk.dname : qinfo->qname;
    size_t qname_len = qinfo->local_alias ?
      qinfo->local_alias->rrset->rk.dname_len :
      qinfo->qname_len;
    if(sldns_buffer_current(buf) == qname)
      sldns_buffer_skip(buf, (ssize_t)qname_len);
    else  sldns_buffer_write(buf, qname, qname_len);
    sldns_buffer_write_u16(buf, qinfo->qtype);
    sldns_buffer_write_u16(buf, qinfo->qclass);
  }
  sldns_buffer_flip(buf);
  if(edns) {
    struct edns_data es = *edns;
    es.edns_version = EDNS_ADVERTISED_VERSION;
    es.udp_size = EDNS_ADVERTISED_SIZE;
    es.ext_rcode = (uint8_t)(rcode >> 4);
    es.bits &= EDNS_DO;
    if(sldns_buffer_limit(buf) + calc_edns_field_size(&es) >
      edns->udp_size) {
      edns_opt_list_remove(&es.opt_list_inplace_cb_out, LDNS_EDNS_EDE);
      edns_opt_list_remove(&es.opt_list_out, LDNS_EDNS_EDE);
      if(sldns_buffer_limit(buf) + calc_edns_field_size(&es) >
        edns->udp_size) {
        return;
      }
    }
    attach_edns_record(buf, &es);
  }
}

void
error_encode(sldns_buffer* buf, int r, struct query_info* qinfo,
  uint16_t qid, uint16_t qflags, struct edns_data* edns)
{
  extended_error_encode(buf, (r & 0x000F), qinfo, qid, qflags,
    (r & 0xFFF0), edns);
}

Coverage Report

Created: 2025-10-13 06:52