1 /*
2 * util/data/msgencode.c - Encode DNS messages, queries and replies.
3 *
4 * Copyright (c) 2007, NLnet Labs. All rights reserved.
5 *
6 * This software is open source.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 *
12 * Redistributions of source code must retain the above copyright notice,
13 * this list of conditions and the following disclaimer.
14 *
15 * Redistributions in binary form must reproduce the above copyright notice,
16 * this list of conditions and the following disclaimer in the documentation
17 * and/or other materials provided with the distribution.
18 *
19 * Neither the name of the NLNET LABS nor the names of its contributors may
20 * be used to endorse or promote products derived from this software without
21 * specific prior written permission.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
24 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
25 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
26 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
27 * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
28 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
29 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
30 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
31 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
32 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
33 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
34 */
35
36 /**
37 * \file
38 *
39 * This file contains a routines to encode DNS messages.
40 */
41
42 #include "config.h"
43 #include "util/data/msgencode.h"
44 #include "util/data/msgreply.h"
45 #include "util/data/msgparse.h"
46 #include "util/data/dname.h"
47 #include "util/log.h"
48 #include "util/regional.h"
49 #include "util/net_help.h"
50 #include "sldns/sbuffer.h"
51 #include "services/localzone.h"
52
53 #ifdef HAVE_TIME_H
54 #include <time.h>
55 #endif
56 #include <sys/time.h>
57
58 /** return code that means the function ran out of memory. negative so it does
59 * not conflict with DNS rcodes. */
60 #define RETVAL_OUTMEM -2
61 /** return code that means the data did not fit (completely) in the packet */
62 #define RETVAL_TRUNC -4
63 /** return code that means all is peachy keen. Equal to DNS rcode NOERROR */
64 #define RETVAL_OK 0
65
66 /**
67 * Data structure to help domain name compression in outgoing messages.
68 * A tree of dnames and their offsets in the packet is kept.
69 * It is kept sorted, not canonical, but by label at least, so that after
70 * a lookup of a name you know its closest match, and the parent from that
71 * closest match. These are possible compression targets.
72 *
73 * It is a binary tree, not a rbtree or balanced tree, as the effort
74 * of keeping it balanced probably outweighs usefulness (given typical
75 * DNS packet size).
76 */
77 struct compress_tree_node {
78 /** left node in tree, all smaller to this */
79 struct compress_tree_node* left;
80 /** right node in tree, all larger than this */
81 struct compress_tree_node* right;
82
83 /** the parent node - not for tree, but zone parent. One less label */
84 struct compress_tree_node* parent;
85 /** the domain name for this node. Pointer to uncompressed memory. */
86 uint8_t* dname;
87 /** number of labels in domain name, kept to help compare func. */
88 int labs;
89 /** offset in packet that points to this dname */
90 size_t offset;
91 };
92
93 /**
94 * Find domain name in tree, returns exact and closest match.
95 * @param tree: root of tree.
96 * @param dname: pointer to uncompressed dname.
97 * @param labs: number of labels in domain name.
98 * @param match: closest or exact match.
99 * guaranteed to be smaller or equal to the sought dname.
100 * can be null if the tree is empty.
101 * @param matchlabels: number of labels that match with closest match.
102 * can be zero is there is no match.
103 * @param insertpt: insert location for dname, if not found.
104 * @return: 0 if no exact match.
105 */
106 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)107 compress_tree_search(struct compress_tree_node** tree, uint8_t* dname,
108 int labs, struct compress_tree_node** match, int* matchlabels,
109 struct compress_tree_node*** insertpt)
110 {
111 int c, n, closen=0;
112 struct compress_tree_node* p = *tree;
113 struct compress_tree_node* close = 0;
114 struct compress_tree_node** prev = tree;
115 while(p) {
116 if((c = dname_lab_cmp(dname, labs, p->dname, p->labs, &n))
117 == 0) {
118 *matchlabels = n;
119 *match = p;
120 return 1;
121 }
122 if(c<0) {
123 prev = &p->left;
124 p = p->left;
125 } else {
126 closen = n;
127 close = p; /* p->dname is smaller than dname */
128 prev = &p->right;
129 p = p->right;
130 }
131 }
132 *insertpt = prev;
133 *matchlabels = closen;
134 *match = close;
135 return 0;
136 }
137
138 /**
139 * Lookup a domain name in compression tree.
140 * @param tree: root of tree (not the node with '.').
141 * @param dname: pointer to uncompressed dname.
142 * @param labs: number of labels in domain name.
143 * @param insertpt: insert location for dname, if not found.
144 * @return: 0 if not found or compress treenode with best compression.
145 */
146 static struct compress_tree_node*
compress_tree_lookup(struct compress_tree_node ** tree,uint8_t * dname,int labs,struct compress_tree_node *** insertpt)147 compress_tree_lookup(struct compress_tree_node** tree, uint8_t* dname,
148 int labs, struct compress_tree_node*** insertpt)
149 {
150 struct compress_tree_node* p;
151 int m;
152 if(labs <= 1)
153 return 0; /* do not compress root node */
154 if(compress_tree_search(tree, dname, labs, &p, &m, insertpt)) {
155 /* exact match */
156 return p;
157 }
158 /* return some ancestor of p that compresses well. */
159 if(m>1) {
160 /* www.example.com. (labs=4) matched foo.example.com.(labs=4)
161 * then matchcount = 3. need to go up. */
162 while(p && p->labs > m)
163 p = p->parent;
164 return p;
165 }
166 return 0;
167 }
168
169 /**
170 * Create node for domain name compression tree.
171 * @param dname: pointer to uncompressed dname (stored in tree).
172 * @param labs: number of labels in dname.
173 * @param offset: offset into packet for dname.
174 * @param region: how to allocate memory for new node.
175 * @return new node or 0 on malloc failure.
176 */
177 static struct compress_tree_node*
compress_tree_newnode(uint8_t * dname,int labs,size_t offset,struct regional * region)178 compress_tree_newnode(uint8_t* dname, int labs, size_t offset,
179 struct regional* region)
180 {
181 struct compress_tree_node* n = (struct compress_tree_node*)
182 regional_alloc(region, sizeof(struct compress_tree_node));
183 if(!n) return 0;
184 n->left = 0;
185 n->right = 0;
186 n->parent = 0;
187 n->dname = dname;
188 n->labs = labs;
189 n->offset = offset;
190 return n;
191 }
192
193 /**
194 * Store domain name and ancestors into compression tree.
195 * @param dname: pointer to uncompressed dname (stored in tree).
196 * @param labs: number of labels in dname.
197 * @param offset: offset into packet for dname.
198 * @param region: how to allocate memory for new node.
199 * @param closest: match from previous lookup, used to compress dname.
200 * may be NULL if no previous match.
201 * if the tree has an ancestor of dname already, this must be it.
202 * @param insertpt: where to insert the dname in tree.
203 * @return: 0 on memory error.
204 */
205 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)206 compress_tree_store(uint8_t* dname, int labs, size_t offset,
207 struct regional* region, struct compress_tree_node* closest,
208 struct compress_tree_node** insertpt)
209 {
210 uint8_t lablen;
211 struct compress_tree_node* newnode;
212 struct compress_tree_node* prevnode = NULL;
213 int uplabs = labs-1; /* does not store root in tree */
214 if(closest) uplabs = labs - closest->labs;
215 log_assert(uplabs >= 0);
216 /* algorithms builds up a vine of dname-labels to hang into tree */
217 while(uplabs--) {
218 if(offset > PTR_MAX_OFFSET) {
219 /* insertion failed, drop vine */
220 return 1; /* compression pointer no longer useful */
221 }
222 if(!(newnode = compress_tree_newnode(dname, labs, offset,
223 region))) {
224 /* insertion failed, drop vine */
225 return 0;
226 }
227
228 if(prevnode) {
229 /* chain nodes together, last one has one label more,
230 * so is larger than newnode, thus goes right. */
231 newnode->right = prevnode;
232 prevnode->parent = newnode;
233 }
234
235 /* next label */
236 lablen = *dname++;
237 dname += lablen;
238 offset += lablen+1;
239 prevnode = newnode;
240 labs--;
241 }
242 /* if we have a vine, hang the vine into the tree */
243 if(prevnode) {
244 *insertpt = prevnode;
245 prevnode->parent = closest;
246 }
247 return 1;
248 }
249
250 /** compress a domain name */
251 static int
write_compressed_dname(sldns_buffer * pkt,uint8_t * dname,int labs,struct compress_tree_node * p)252 write_compressed_dname(sldns_buffer* pkt, uint8_t* dname, int labs,
253 struct compress_tree_node* p)
254 {
255 /* compress it */
256 int labcopy = labs - p->labs;
257 uint8_t lablen;
258 uint16_t ptr;
259
260 if(labs == 1) {
261 /* write root label */
262 if(sldns_buffer_remaining(pkt) < 1)
263 return 0;
264 sldns_buffer_write_u8(pkt, 0);
265 return 1;
266 }
267
268 /* copy the first couple of labels */
269 while(labcopy--) {
270 lablen = *dname++;
271 if(sldns_buffer_remaining(pkt) < (size_t)lablen+1)
272 return 0;
273 sldns_buffer_write_u8(pkt, lablen);
274 sldns_buffer_write(pkt, dname, lablen);
275 dname += lablen;
276 }
277 /* insert compression ptr */
278 if(sldns_buffer_remaining(pkt) < 2)
279 return 0;
280 ptr = PTR_CREATE(p->offset);
281 sldns_buffer_write_u16(pkt, ptr);
282 return 1;
283 }
284
285 /** compress owner name of RR, return RETVAL_OUTMEM RETVAL_TRUNC */
286 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)287 compress_owner(struct ub_packed_rrset_key* key, sldns_buffer* pkt,
288 struct regional* region, struct compress_tree_node** tree,
289 size_t owner_pos, uint16_t* owner_ptr, int owner_labs)
290 {
291 struct compress_tree_node* p;
292 struct compress_tree_node** insertpt = NULL;
293 if(!*owner_ptr) {
294 /* compress first time dname */
295 if((p = compress_tree_lookup(tree, key->rk.dname,
296 owner_labs, &insertpt))) {
297 if(p->labs == owner_labs)
298 /* avoid ptr chains, since some software is
299 * not capable of decoding ptr after a ptr. */
300 *owner_ptr = htons(PTR_CREATE(p->offset));
301 if(!write_compressed_dname(pkt, key->rk.dname,
302 owner_labs, p))
303 return RETVAL_TRUNC;
304 /* check if typeclass+4 ttl + rdatalen is available */
305 if(sldns_buffer_remaining(pkt) < 4+4+2)
306 return RETVAL_TRUNC;
307 } else {
308 /* no compress */
309 if(sldns_buffer_remaining(pkt) < key->rk.dname_len+4+4+2)
310 return RETVAL_TRUNC;
311 sldns_buffer_write(pkt, key->rk.dname,
312 key->rk.dname_len);
313 if(owner_pos <= PTR_MAX_OFFSET)
314 *owner_ptr = htons(PTR_CREATE(owner_pos));
315 }
316 if(!compress_tree_store(key->rk.dname, owner_labs,
317 owner_pos, region, p, insertpt))
318 return RETVAL_OUTMEM;
319 } else {
320 /* always compress 2nd-further RRs in RRset */
321 if(owner_labs == 1) {
322 if(sldns_buffer_remaining(pkt) < 1+4+4+2)
323 return RETVAL_TRUNC;
324 sldns_buffer_write_u8(pkt, 0);
325 } else {
326 if(sldns_buffer_remaining(pkt) < 2+4+4+2)
327 return RETVAL_TRUNC;
328 sldns_buffer_write(pkt, owner_ptr, 2);
329 }
330 }
331 return RETVAL_OK;
332 }
333
334 /** compress any domain name to the packet, return RETVAL_* */
335 static int
compress_any_dname(uint8_t * dname,sldns_buffer * pkt,int labs,struct regional * region,struct compress_tree_node ** tree)336 compress_any_dname(uint8_t* dname, sldns_buffer* pkt, int labs,
337 struct regional* region, struct compress_tree_node** tree)
338 {
339 struct compress_tree_node* p;
340 struct compress_tree_node** insertpt = NULL;
341 size_t pos = sldns_buffer_position(pkt);
342 if((p = compress_tree_lookup(tree, dname, labs, &insertpt))) {
343 if(!write_compressed_dname(pkt, dname, labs, p))
344 return RETVAL_TRUNC;
345 } else {
346 if(!dname_buffer_write(pkt, dname))
347 return RETVAL_TRUNC;
348 }
349 if(!compress_tree_store(dname, labs, pos, region, p, insertpt))
350 return RETVAL_OUTMEM;
351 return RETVAL_OK;
352 }
353
354 /** return true if type needs domain name compression in rdata */
355 static const sldns_rr_descriptor*
type_rdata_compressable(struct ub_packed_rrset_key * key)356 type_rdata_compressable(struct ub_packed_rrset_key* key)
357 {
358 uint16_t t = ntohs(key->rk.type);
359 if(sldns_rr_descript(t) &&
360 sldns_rr_descript(t)->_compress == LDNS_RR_COMPRESS)
361 return sldns_rr_descript(t);
362 return 0;
363 }
364
365 /** compress domain names in rdata, return RETVAL_* */
366 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)367 compress_rdata(sldns_buffer* pkt, uint8_t* rdata, size_t todolen,
368 struct regional* region, struct compress_tree_node** tree,
369 const sldns_rr_descriptor* desc)
370 {
371 int labs, r, rdf = 0;
372 size_t dname_len, len, pos = sldns_buffer_position(pkt);
373 uint8_t count = desc->_dname_count;
374
375 sldns_buffer_skip(pkt, 2); /* rdata len fill in later */
376 /* space for rdatalen checked for already */
377 rdata += 2;
378 todolen -= 2;
379 while(todolen > 0 && count) {
380 switch(desc->_wireformat[rdf]) {
381 case LDNS_RDF_TYPE_DNAME:
382 labs = dname_count_size_labels(rdata, &dname_len);
383 if((r=compress_any_dname(rdata, pkt, labs, region,
384 tree)) != RETVAL_OK)
385 return r;
386 rdata += dname_len;
387 todolen -= dname_len;
388 count--;
389 len = 0;
390 break;
391 case LDNS_RDF_TYPE_STR:
392 len = *rdata + 1;
393 break;
394 default:
395 len = get_rdf_size(desc->_wireformat[rdf]);
396 }
397 if(len) {
398 /* copy over */
399 if(sldns_buffer_remaining(pkt) < len)
400 return RETVAL_TRUNC;
401 sldns_buffer_write(pkt, rdata, len);
402 todolen -= len;
403 rdata += len;
404 }
405 rdf++;
406 }
407 /* copy remainder */
408 if(todolen > 0) {
409 if(sldns_buffer_remaining(pkt) < todolen)
410 return RETVAL_TRUNC;
411 sldns_buffer_write(pkt, rdata, todolen);
412 }
413
414 /* set rdata len */
415 sldns_buffer_write_u16_at(pkt, pos, sldns_buffer_position(pkt)-pos-2);
416 return RETVAL_OK;
417 }
418
419 /** Returns true if RR type should be included */
420 static int
rrset_belongs_in_reply(sldns_pkt_section s,uint16_t rrtype,uint16_t qtype,int dnssec)421 rrset_belongs_in_reply(sldns_pkt_section s, uint16_t rrtype, uint16_t qtype,
422 int dnssec)
423 {
424 if(dnssec)
425 return 1;
426 /* skip non DNSSEC types, except if directly queried for */
427 if(s == LDNS_SECTION_ANSWER) {
428 if(qtype == LDNS_RR_TYPE_ANY || qtype == rrtype)
429 return 1;
430 }
431 /* check DNSSEC-ness */
432 switch(rrtype) {
433 case LDNS_RR_TYPE_SIG:
434 case LDNS_RR_TYPE_KEY:
435 case LDNS_RR_TYPE_NXT:
436 case LDNS_RR_TYPE_DS:
437 case LDNS_RR_TYPE_RRSIG:
438 case LDNS_RR_TYPE_NSEC:
439 case LDNS_RR_TYPE_DNSKEY:
440 case LDNS_RR_TYPE_NSEC3:
441 case LDNS_RR_TYPE_NSEC3PARAMS:
442 return 0;
443 }
444 return 1;
445 }
446
447 /** store rrset in buffer in wireformat, return RETVAL_* */
448 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)449 packed_rrset_encode(struct ub_packed_rrset_key* key, sldns_buffer* pkt,
450 uint16_t* num_rrs, time_t timenow, struct regional* region,
451 int do_data, int do_sig, struct compress_tree_node** tree,
452 sldns_pkt_section s, uint16_t qtype, int dnssec, size_t rr_offset)
453 {
454 size_t i, j, owner_pos;
455 int r, owner_labs;
456 uint16_t owner_ptr = 0;
457 time_t adjust = 0;
458 struct packed_rrset_data* data = (struct packed_rrset_data*)
459 key->entry.data;
460
461 /* does this RR type belong in the answer? */
462 if(!rrset_belongs_in_reply(s, ntohs(key->rk.type), qtype, dnssec))
463 return RETVAL_OK;
464
465 owner_labs = dname_count_labels(key->rk.dname);
466 owner_pos = sldns_buffer_position(pkt);
467
468 /** Determine relative time adjustment for TTL values.
469 * For an rrset with a fixed TTL, use the rrset's TTL as given. */
470 if((key->rk.flags & PACKED_RRSET_FIXEDTTL) != 0)
471 adjust = 0;
472 else
473 adjust = SERVE_ORIGINAL_TTL ? data->ttl_add : timenow;
474
475 if(do_data) {
476 const sldns_rr_descriptor* c = type_rdata_compressable(key);
477 for(i=0; i<data->count; i++) {
478 /* rrset roundrobin */
479 j = (i + rr_offset) % data->count;
480 if((r=compress_owner(key, pkt, region, tree,
481 owner_pos, &owner_ptr, owner_labs))
482 != RETVAL_OK)
483 return r;
484 sldns_buffer_write(pkt, &key->rk.type, 2);
485 sldns_buffer_write(pkt, &key->rk.rrset_class, 2);
486 if(data->rr_ttl[j] < adjust)
487 sldns_buffer_write_u32(pkt,
488 SERVE_EXPIRED?SERVE_EXPIRED_REPLY_TTL:0);
489 else sldns_buffer_write_u32(pkt, data->rr_ttl[j]-adjust);
490 if(c) {
491 if((r=compress_rdata(pkt, data->rr_data[j],
492 data->rr_len[j], region, tree, c))
493 != RETVAL_OK)
494 return r;
495 } else {
496 if(sldns_buffer_remaining(pkt) < data->rr_len[j])
497 return RETVAL_TRUNC;
498 sldns_buffer_write(pkt, data->rr_data[j],
499 data->rr_len[j]);
500 }
501 }
502 }
503 /* insert rrsigs */
504 if(do_sig && dnssec) {
505 size_t total = data->count+data->rrsig_count;
506 for(i=data->count; i<total; i++) {
507 if(owner_ptr && owner_labs != 1) {
508 if(sldns_buffer_remaining(pkt) <
509 2+4+4+data->rr_len[i])
510 return RETVAL_TRUNC;
511 sldns_buffer_write(pkt, &owner_ptr, 2);
512 } else {
513 if((r=compress_any_dname(key->rk.dname,
514 pkt, owner_labs, region, tree))
515 != RETVAL_OK)
516 return r;
517 if(sldns_buffer_remaining(pkt) <
518 4+4+data->rr_len[i])
519 return RETVAL_TRUNC;
520 }
521 sldns_buffer_write_u16(pkt, LDNS_RR_TYPE_RRSIG);
522 sldns_buffer_write(pkt, &key->rk.rrset_class, 2);
523 if(data->rr_ttl[i] < adjust)
524 sldns_buffer_write_u32(pkt,
525 SERVE_EXPIRED?SERVE_EXPIRED_REPLY_TTL:0);
526 else sldns_buffer_write_u32(pkt, data->rr_ttl[i]-adjust);
527 /* rrsig rdata cannot be compressed, perform 100+ byte
528 * memcopy. */
529 sldns_buffer_write(pkt, data->rr_data[i],
530 data->rr_len[i]);
531 }
532 }
533 /* change rrnum only after we are sure it fits */
534 if(do_data)
535 *num_rrs += data->count;
536 if(do_sig && dnssec)
537 *num_rrs += data->rrsig_count;
538
539 return RETVAL_OK;
540 }
541
542 /** store msg section in wireformat buffer, return RETVAL_* */
543 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)544 insert_section(struct reply_info* rep, size_t num_rrsets, uint16_t* num_rrs,
545 sldns_buffer* pkt, size_t rrsets_before, time_t timenow,
546 struct regional* region, struct compress_tree_node** tree,
547 sldns_pkt_section s, uint16_t qtype, int dnssec, size_t rr_offset)
548 {
549 int r;
550 size_t i, setstart;
551 /* we now allow this function to be called multiple times for the
552 * same section, incrementally updating num_rrs. The caller is
553 * responsible for initializing it (which is the case in the current
554 * implementation). */
555
556 if(s != LDNS_SECTION_ADDITIONAL) {
557 if(s == LDNS_SECTION_ANSWER && qtype == LDNS_RR_TYPE_ANY)
558 dnssec = 1; /* include all types in ANY answer */
559 for(i=0; i<num_rrsets; i++) {
560 setstart = sldns_buffer_position(pkt);
561 if((r=packed_rrset_encode(rep->rrsets[rrsets_before+i],
562 pkt, num_rrs, timenow, region, 1, 1, tree,
563 s, qtype, dnssec, rr_offset))
564 != RETVAL_OK) {
565 /* Bad, but if due to size must set TC bit */
566 /* trim off the rrset neatly. */
567 sldns_buffer_set_position(pkt, setstart);
568 return r;
569 }
570 }
571 } else {
572 for(i=0; i<num_rrsets; i++) {
573 setstart = sldns_buffer_position(pkt);
574 if((r=packed_rrset_encode(rep->rrsets[rrsets_before+i],
575 pkt, num_rrs, timenow, region, 1, 0, tree,
576 s, qtype, dnssec, rr_offset))
577 != RETVAL_OK) {
578 sldns_buffer_set_position(pkt, setstart);
579 return r;
580 }
581 }
582 if(dnssec)
583 for(i=0; i<num_rrsets; i++) {
584 setstart = sldns_buffer_position(pkt);
585 if((r=packed_rrset_encode(rep->rrsets[rrsets_before+i],
586 pkt, num_rrs, timenow, region, 0, 1, tree,
587 s, qtype, dnssec, rr_offset))
588 != RETVAL_OK) {
589 sldns_buffer_set_position(pkt, setstart);
590 return r;
591 }
592 }
593 }
594 return RETVAL_OK;
595 }
596
597 /** store query section in wireformat buffer, return RETVAL */
598 static int
insert_query(struct query_info * qinfo,struct compress_tree_node ** tree,sldns_buffer * buffer,struct regional * region)599 insert_query(struct query_info* qinfo, struct compress_tree_node** tree,
600 sldns_buffer* buffer, struct regional* region)
601 {
602 uint8_t* qname = qinfo->local_alias ?
603 qinfo->local_alias->rrset->rk.dname : qinfo->qname;
604 size_t qname_len = qinfo->local_alias ?
605 qinfo->local_alias->rrset->rk.dname_len : qinfo->qname_len;
606 if(sldns_buffer_remaining(buffer) <
607 qinfo->qname_len+sizeof(uint16_t)*2)
608 return RETVAL_TRUNC; /* buffer too small */
609 /* the query is the first name inserted into the tree */
610 if(!compress_tree_store(qname, dname_count_labels(qname),
611 sldns_buffer_position(buffer), region, NULL, tree))
612 return RETVAL_OUTMEM;
613 if(sldns_buffer_current(buffer) == qname)
614 sldns_buffer_skip(buffer, (ssize_t)qname_len);
615 else sldns_buffer_write(buffer, qname, qname_len);
616 sldns_buffer_write_u16(buffer, qinfo->qtype);
617 sldns_buffer_write_u16(buffer, qinfo->qclass);
618 return RETVAL_OK;
619 }
620
621 static int
positive_answer(struct reply_info * rep,uint16_t qtype)622 positive_answer(struct reply_info* rep, uint16_t qtype) {
623 size_t i;
624 if (FLAGS_GET_RCODE(rep->flags) != LDNS_RCODE_NOERROR)
625 return 0;
626
627 for(i=0;i<rep->an_numrrsets; i++) {
628 if(ntohs(rep->rrsets[i]->rk.type) == qtype) {
629 /* for priming queries, type NS, include addresses */
630 if(qtype == LDNS_RR_TYPE_NS)
631 return 0;
632 /* in case it is a wildcard with DNSSEC, there will
633 * be NSEC/NSEC3 records in the authority section
634 * that we cannot remove */
635 for(i=rep->an_numrrsets; i<rep->an_numrrsets+
636 rep->ns_numrrsets; i++) {
637 if(ntohs(rep->rrsets[i]->rk.type) ==
638 LDNS_RR_TYPE_NSEC ||
639 ntohs(rep->rrsets[i]->rk.type) ==
640 LDNS_RR_TYPE_NSEC3)
641 return 0;
642 }
643 return 1;
644 }
645 }
646 return 0;
647 }
648
649 static int
negative_answer(struct reply_info * rep)650 negative_answer(struct reply_info* rep) {
651 size_t i;
652 int ns_seen = 0;
653 if(FLAGS_GET_RCODE(rep->flags) == LDNS_RCODE_NXDOMAIN)
654 return 1;
655 if(FLAGS_GET_RCODE(rep->flags) == LDNS_RCODE_NOERROR &&
656 rep->an_numrrsets != 0)
657 return 0; /* positive */
658 if(FLAGS_GET_RCODE(rep->flags) != LDNS_RCODE_NOERROR &&
659 FLAGS_GET_RCODE(rep->flags) != LDNS_RCODE_NXDOMAIN)
660 return 0;
661 for(i=rep->an_numrrsets; i<rep->an_numrrsets+rep->ns_numrrsets; i++){
662 if(ntohs(rep->rrsets[i]->rk.type) == LDNS_RR_TYPE_SOA)
663 return 1;
664 if(ntohs(rep->rrsets[i]->rk.type) == LDNS_RR_TYPE_NS)
665 ns_seen = 1;
666 }
667 if(ns_seen) return 0; /* could be referral, NS, but no SOA */
668 return 1;
669 }
670
671 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)672 reply_info_encode(struct query_info* qinfo, struct reply_info* rep,
673 uint16_t id, uint16_t flags, sldns_buffer* buffer, time_t timenow,
674 struct regional* region, uint16_t udpsize, int dnssec, int minimise)
675 {
676 uint16_t ancount=0, nscount=0, arcount=0;
677 struct compress_tree_node* tree = 0;
678 int r;
679 size_t rr_offset;
680
681 sldns_buffer_clear(buffer);
682 if(udpsize < sldns_buffer_limit(buffer))
683 sldns_buffer_set_limit(buffer, udpsize);
684 if(sldns_buffer_remaining(buffer) < LDNS_HEADER_SIZE)
685 return 0;
686
687 sldns_buffer_write(buffer, &id, sizeof(uint16_t));
688 sldns_buffer_write_u16(buffer, flags);
689 sldns_buffer_write_u16(buffer, rep->qdcount);
690 /* set an, ns, ar counts to zero in case of small packets */
691 sldns_buffer_write(buffer, "\000\000\000\000\000\000", 6);
692
693 /* insert query section */
694 if(rep->qdcount) {
695 if((r=insert_query(qinfo, &tree, buffer, region)) !=
696 RETVAL_OK) {
697 if(r == RETVAL_TRUNC) {
698 /* create truncated message */
699 sldns_buffer_write_u16_at(buffer, 4, 0);
700 LDNS_TC_SET(sldns_buffer_begin(buffer));
701 sldns_buffer_flip(buffer);
702 return 1;
703 }
704 return 0;
705 }
706 }
707 /* roundrobin offset. using query id for random number. With ntohs
708 * for different roundrobins for sequential id client senders. */
709 rr_offset = RRSET_ROUNDROBIN?ntohs(id)+(timenow?timenow:time(NULL)):0;
710
711 /* "prepend" any local alias records in the answer section if this
712 * response is supposed to be authoritative. Currently it should
713 * be a single CNAME record (sanity-checked in worker_handle_request())
714 * but it can be extended if and when we support more variations of
715 * aliases. */
716 if(qinfo->local_alias && (flags & BIT_AA)) {
717 struct reply_info arep;
718 time_t timezero = 0; /* to use the 'authoritative' TTL */
719 memset(&arep, 0, sizeof(arep));
720 arep.flags = rep->flags;
721 arep.an_numrrsets = 1;
722 arep.rrset_count = 1;
723 arep.rrsets = &qinfo->local_alias->rrset;
724 if((r=insert_section(&arep, 1, &ancount, buffer, 0,
725 timezero, region, &tree, LDNS_SECTION_ANSWER,
726 qinfo->qtype, dnssec, rr_offset)) != RETVAL_OK) {
727 if(r == RETVAL_TRUNC) {
728 /* create truncated message */
729 sldns_buffer_write_u16_at(buffer, 6, ancount);
730 LDNS_TC_SET(sldns_buffer_begin(buffer));
731 sldns_buffer_flip(buffer);
732 return 1;
733 }
734 return 0;
735 }
736 }
737
738 /* insert answer section */
739 if((r=insert_section(rep, rep->an_numrrsets, &ancount, buffer,
740 0, timenow, region, &tree, LDNS_SECTION_ANSWER, qinfo->qtype,
741 dnssec, rr_offset)) != RETVAL_OK) {
742 if(r == RETVAL_TRUNC) {
743 /* create truncated message */
744 sldns_buffer_write_u16_at(buffer, 6, ancount);
745 LDNS_TC_SET(sldns_buffer_begin(buffer));
746 sldns_buffer_flip(buffer);
747 return 1;
748 }
749 return 0;
750 }
751 sldns_buffer_write_u16_at(buffer, 6, ancount);
752
753 /* if response is positive answer, auth/add sections are not required */
754 if( ! (minimise && positive_answer(rep, qinfo->qtype)) ) {
755 /* insert auth section */
756 if((r=insert_section(rep, rep->ns_numrrsets, &nscount, buffer,
757 rep->an_numrrsets, timenow, region, &tree,
758 LDNS_SECTION_AUTHORITY, qinfo->qtype,
759 dnssec, rr_offset)) != RETVAL_OK) {
760 if(r == RETVAL_TRUNC) {
761 /* create truncated message */
762 sldns_buffer_write_u16_at(buffer, 8, nscount);
763 LDNS_TC_SET(sldns_buffer_begin(buffer));
764 sldns_buffer_flip(buffer);
765 return 1;
766 }
767 return 0;
768 }
769 sldns_buffer_write_u16_at(buffer, 8, nscount);
770
771 if(! (minimise && negative_answer(rep))) {
772 /* insert add section */
773 if((r=insert_section(rep, rep->ar_numrrsets, &arcount, buffer,
774 rep->an_numrrsets + rep->ns_numrrsets, timenow, region,
775 &tree, LDNS_SECTION_ADDITIONAL, qinfo->qtype,
776 dnssec, rr_offset)) != RETVAL_OK) {
777 if(r == RETVAL_TRUNC) {
778 /* no need to set TC bit, this is the additional */
779 sldns_buffer_write_u16_at(buffer, 10, arcount);
780 sldns_buffer_flip(buffer);
781 return 1;
782 }
783 return 0;
784 }
785 sldns_buffer_write_u16_at(buffer, 10, arcount);
786 }
787 }
788 sldns_buffer_flip(buffer);
789 return 1;
790 }
791
792 uint16_t
calc_edns_field_size(struct edns_data * edns)793 calc_edns_field_size(struct edns_data* edns)
794 {
795 size_t rdatalen = 0;
796 struct edns_option* opt;
797 if(!edns || !edns->edns_present)
798 return 0;
799 for(opt = edns->opt_list_inplace_cb_out; opt; opt = opt->next) {
800 rdatalen += 4 + opt->opt_len;
801 }
802 for(opt = edns->opt_list_out; opt; opt = opt->next) {
803 rdatalen += 4 + opt->opt_len;
804 }
805 /* domain root '.' + type + class + ttl + rdatalen */
806 return 1 + 2 + 2 + 4 + 2 + rdatalen;
807 }
808
809 static void
attach_edns_record_max_msg_sz(sldns_buffer * pkt,struct edns_data * edns,uint16_t max_msg_sz)810 attach_edns_record_max_msg_sz(sldns_buffer* pkt, struct edns_data* edns,
811 uint16_t max_msg_sz)
812 {
813 size_t len;
814 size_t rdatapos;
815 struct edns_option* opt;
816 struct edns_option* padding_option = NULL;
817 /* inc additional count */
818 sldns_buffer_write_u16_at(pkt, 10,
819 sldns_buffer_read_u16_at(pkt, 10) + 1);
820 len = sldns_buffer_limit(pkt);
821 sldns_buffer_clear(pkt);
822 sldns_buffer_set_position(pkt, len);
823 /* write EDNS record */
824 sldns_buffer_write_u8(pkt, 0); /* '.' label */
825 sldns_buffer_write_u16(pkt, LDNS_RR_TYPE_OPT); /* type */
826 sldns_buffer_write_u16(pkt, edns->udp_size); /* class */
827 sldns_buffer_write_u8(pkt, edns->ext_rcode); /* ttl */
828 sldns_buffer_write_u8(pkt, edns->edns_version);
829 sldns_buffer_write_u16(pkt, edns->bits);
830 rdatapos = sldns_buffer_position(pkt);
831 sldns_buffer_write_u16(pkt, 0); /* rdatalen */
832 /* write rdata */
833 for(opt=edns->opt_list_inplace_cb_out; opt; opt=opt->next) {
834 if (opt->opt_code == LDNS_EDNS_PADDING) {
835 padding_option = opt;
836 continue;
837 }
838 sldns_buffer_write_u16(pkt, opt->opt_code);
839 sldns_buffer_write_u16(pkt, opt->opt_len);
840 if(opt->opt_len != 0)
841 sldns_buffer_write(pkt, opt->opt_data, opt->opt_len);
842 }
843 for(opt=edns->opt_list_out; opt; opt=opt->next) {
844 if (opt->opt_code == LDNS_EDNS_PADDING) {
845 padding_option = opt;
846 continue;
847 }
848 sldns_buffer_write_u16(pkt, opt->opt_code);
849 sldns_buffer_write_u16(pkt, opt->opt_len);
850 if(opt->opt_len != 0)
851 sldns_buffer_write(pkt, opt->opt_data, opt->opt_len);
852 }
853 if (padding_option && edns->padding_block_size ) {
854 size_t pad_pos = sldns_buffer_position(pkt);
855 size_t msg_sz = ((pad_pos + 3) / edns->padding_block_size + 1)
856 * edns->padding_block_size;
857 size_t pad_sz;
858
859 if (msg_sz > max_msg_sz)
860 msg_sz = max_msg_sz;
861
862 /* By use of calc_edns_field_size, calling functions should
863 * have made sure that there is enough space for at least a
864 * zero sized padding option.
865 */
866 log_assert(pad_pos + 4 <= msg_sz);
867
868 pad_sz = msg_sz - pad_pos - 4;
869 sldns_buffer_write_u16(pkt, LDNS_EDNS_PADDING);
870 sldns_buffer_write_u16(pkt, pad_sz);
871 if (pad_sz) {
872 memset(sldns_buffer_current(pkt), 0, pad_sz);
873 sldns_buffer_skip(pkt, pad_sz);
874 }
875 }
876 sldns_buffer_write_u16_at(pkt, rdatapos,
877 sldns_buffer_position(pkt)-rdatapos-2);
878 sldns_buffer_flip(pkt);
879 }
880
881 void
attach_edns_record(sldns_buffer * pkt,struct edns_data * edns)882 attach_edns_record(sldns_buffer* pkt, struct edns_data* edns)
883 {
884 if(!edns || !edns->edns_present)
885 return;
886 attach_edns_record_max_msg_sz(pkt, edns, edns->udp_size);
887 }
888
889 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)890 reply_info_answer_encode(struct query_info* qinf, struct reply_info* rep,
891 uint16_t id, uint16_t qflags, sldns_buffer* pkt, time_t timenow,
892 int cached, struct regional* region, uint16_t udpsize,
893 struct edns_data* edns, int dnssec, int secure)
894 {
895 uint16_t flags;
896 unsigned int attach_edns = 0;
897
898 if(!cached || rep->authoritative) {
899 /* original flags, copy RD and CD bits from query. */
900 flags = rep->flags | (qflags & (BIT_RD|BIT_CD));
901 } else {
902 /* remove AA bit, copy RD and CD bits from query. */
903 flags = (rep->flags & ~BIT_AA) | (qflags & (BIT_RD|BIT_CD));
904 }
905 if(secure && (dnssec || (qflags&BIT_AD)))
906 flags |= BIT_AD;
907 /* restore AA bit if we have a local alias and the response can be
908 * authoritative. Also clear AD bit if set as the local data is the
909 * primary answer. */
910 if(qinf->local_alias &&
911 (FLAGS_GET_RCODE(rep->flags) == LDNS_RCODE_NOERROR ||
912 FLAGS_GET_RCODE(rep->flags) == LDNS_RCODE_NXDOMAIN)) {
913 flags |= BIT_AA;
914 flags &= ~BIT_AD;
915 }
916 log_assert(flags & BIT_QR); /* QR bit must be on in our replies */
917 if(udpsize < LDNS_HEADER_SIZE)
918 return 0;
919 if(sldns_buffer_capacity(pkt) < udpsize)
920 udpsize = sldns_buffer_capacity(pkt);
921 if(udpsize < LDNS_HEADER_SIZE + calc_edns_field_size(edns)) {
922 /* packet too small to contain edns, omit it. */
923 attach_edns = 0;
924 } else {
925 /* reserve space for edns record */
926 attach_edns = (unsigned int)calc_edns_field_size(edns);
927 udpsize -= attach_edns;
928 }
929
930 if(!reply_info_encode(qinf, rep, id, flags, pkt, timenow, region,
931 udpsize, dnssec, MINIMAL_RESPONSES)) {
932 log_err("reply encode: out of memory");
933 return 0;
934 }
935 if(attach_edns && sldns_buffer_capacity(pkt) >=
936 sldns_buffer_limit(pkt)+attach_edns)
937 attach_edns_record_max_msg_sz(pkt, edns, udpsize+attach_edns);
938 return 1;
939 }
940
941 void
qinfo_query_encode(sldns_buffer * pkt,struct query_info * qinfo)942 qinfo_query_encode(sldns_buffer* pkt, struct query_info* qinfo)
943 {
944 uint16_t flags = 0; /* QUERY, NOERROR */
945 const uint8_t* qname = qinfo->local_alias ?
946 qinfo->local_alias->rrset->rk.dname : qinfo->qname;
947 size_t qname_len = qinfo->local_alias ?
948 qinfo->local_alias->rrset->rk.dname_len : qinfo->qname_len;
949 sldns_buffer_clear(pkt);
950 log_assert(sldns_buffer_remaining(pkt) >= 12+255+4/*max query*/);
951 sldns_buffer_skip(pkt, 2); /* id done later */
952 sldns_buffer_write_u16(pkt, flags);
953 sldns_buffer_write_u16(pkt, 1); /* query count */
954 sldns_buffer_write(pkt, "\000\000\000\000\000\000", 6); /* counts */
955 sldns_buffer_write(pkt, qname, qname_len);
956 sldns_buffer_write_u16(pkt, qinfo->qtype);
957 sldns_buffer_write_u16(pkt, qinfo->qclass);
958 sldns_buffer_flip(pkt);
959 }
960
961 void
error_encode(sldns_buffer * buf,int r,struct query_info * qinfo,uint16_t qid,uint16_t qflags,struct edns_data * edns)962 error_encode(sldns_buffer* buf, int r, struct query_info* qinfo,
963 uint16_t qid, uint16_t qflags, struct edns_data* edns)
964 {
965 uint16_t flags;
966
967 sldns_buffer_clear(buf);
968 sldns_buffer_write(buf, &qid, sizeof(uint16_t));
969 flags = (uint16_t)(BIT_QR | BIT_RA | r); /* QR and retcode*/
970 flags |= (qflags & (BIT_RD|BIT_CD)); /* copy RD and CD bit */
971 sldns_buffer_write_u16(buf, flags);
972 if(qinfo) flags = 1;
973 else flags = 0;
974 sldns_buffer_write_u16(buf, flags);
975 flags = 0;
976 sldns_buffer_write(buf, &flags, sizeof(uint16_t));
977 sldns_buffer_write(buf, &flags, sizeof(uint16_t));
978 sldns_buffer_write(buf, &flags, sizeof(uint16_t));
979 if(qinfo) {
980 const uint8_t* qname = qinfo->local_alias ?
981 qinfo->local_alias->rrset->rk.dname : qinfo->qname;
982 size_t qname_len = qinfo->local_alias ?
983 qinfo->local_alias->rrset->rk.dname_len :
984 qinfo->qname_len;
985 if(sldns_buffer_current(buf) == qname)
986 sldns_buffer_skip(buf, (ssize_t)qname_len);
987 else sldns_buffer_write(buf, qname, qname_len);
988 sldns_buffer_write_u16(buf, qinfo->qtype);
989 sldns_buffer_write_u16(buf, qinfo->qclass);
990 }
991 sldns_buffer_flip(buf);
992 if(edns) {
993 struct edns_data es = *edns;
994 es.edns_version = EDNS_ADVERTISED_VERSION;
995 es.udp_size = EDNS_ADVERTISED_SIZE;
996 es.ext_rcode = 0;
997 es.bits &= EDNS_DO;
998 if(sldns_buffer_limit(buf) + calc_edns_field_size(&es) >
999 edns->udp_size)
1000 return;
1001 attach_edns_record(buf, &es);
1002 }
1003 }
1004