1 #include <u.h>
2 #include <libc.h>
3 #include <ip.h>
4 #include <bio.h>
5 #include <ndb.h>
6 #include "dns.h"
7
8 /*
9 * a dictionary of domain names for packing messages
10 */
11 enum
12 {
13 Ndict= 64
14 };
15 typedef struct Dict Dict;
16 struct Dict
17 {
18 struct {
19 ushort offset; /* pointer to packed name in message */
20 char *name; /* pointer to unpacked name in buf */
21 } x[Ndict];
22 int n; /* size of dictionary */
23 uchar *start; /* start of packed message */
24 char buf[4*1024]; /* buffer for unpacked names */
25 char *ep; /* first free char in buf */
26 };
27
28 #define NAME(x) p = pname(p, ep, x, dp)
29 #define SYMBOL(x) p = psym(p, ep, x)
30 #define STRING(x) p = pstr(p, ep, x)
31 #define BYTES(x, n) p = pbytes(p, ep, x, n)
32 #define USHORT(x) p = pushort(p, ep, x)
33 #define UCHAR(x) p = puchar(p, ep, x)
34 #define ULONG(x) p = pulong(p, ep, x)
35 #define V4ADDR(x) p = pv4addr(p, ep, x)
36 #define V6ADDR(x) p = pv6addr(p, ep, x)
37
38 static uchar*
psym(uchar * p,uchar * ep,char * np)39 psym(uchar *p, uchar *ep, char *np)
40 {
41 int n;
42
43 n = strlen(np);
44 if(n >= Strlen) /* DNS maximum length string */
45 n = Strlen - 1;
46 if(ep - p < n+1) /* see if it fits in the buffer */
47 return ep+1;
48 *p++ = n;
49 memcpy(p, np, n);
50 return p + n;
51 }
52
53 static uchar*
pstr(uchar * p,uchar * ep,char * np)54 pstr(uchar *p, uchar *ep, char *np)
55 {
56 int n;
57
58 n = strlen(np);
59 if(n >= Strlen) /* DNS maximum length string */
60 n = Strlen - 1;
61 if(ep - p < n+1) /* see if it fits in the buffer */
62 return ep+1;
63 *p++ = n;
64 memcpy(p, np, n);
65 return p + n;
66 }
67
68 static uchar*
pbytes(uchar * p,uchar * ep,uchar * np,int n)69 pbytes(uchar *p, uchar *ep, uchar *np, int n)
70 {
71 if(ep - p < n)
72 return ep+1;
73 memcpy(p, np, n);
74 return p + n;
75 }
76
77 static uchar*
puchar(uchar * p,uchar * ep,int val)78 puchar(uchar *p, uchar *ep, int val)
79 {
80 if(ep - p < 1)
81 return ep+1;
82 *p++ = val;
83 return p;
84 }
85
86 static uchar*
pushort(uchar * p,uchar * ep,int val)87 pushort(uchar *p, uchar *ep, int val)
88 {
89 if(ep - p < 2)
90 return ep+1;
91 *p++ = val>>8;
92 *p++ = val;
93 return p;
94 }
95
96 static uchar*
pulong(uchar * p,uchar * ep,int val)97 pulong(uchar *p, uchar *ep, int val)
98 {
99 if(ep - p < 4)
100 return ep+1;
101 *p++ = val>>24;
102 *p++ = val>>16;
103 *p++ = val>>8;
104 *p++ = val;
105 return p;
106 }
107
108 static uchar*
pv4addr(uchar * p,uchar * ep,char * name)109 pv4addr(uchar *p, uchar *ep, char *name)
110 {
111 uchar ip[IPaddrlen];
112
113 if(ep - p < 4)
114 return ep+1;
115 parseip(ip, name);
116 v6tov4(p, ip);
117 return p + 4;
118
119 }
120
121 static uchar*
pv6addr(uchar * p,uchar * ep,char * name)122 pv6addr(uchar *p, uchar *ep, char *name)
123 {
124 if(ep - p < IPaddrlen)
125 return ep+1;
126 parseip(p, name);
127 return p + IPaddrlen;
128
129 }
130
131 static uchar*
pname(uchar * p,uchar * ep,char * np,Dict * dp)132 pname(uchar *p, uchar *ep, char *np, Dict *dp)
133 {
134 char *cp;
135 int i;
136 char *last; /* last component packed */
137
138 if(strlen(np) >= Domlen) /* make sure we don't exceed DNS limits */
139 return ep+1;
140
141 last = 0;
142 while(*np){
143 /* look through every component in the dictionary for a match */
144 for(i = 0; i < dp->n; i++){
145 if(strcmp(np, dp->x[i].name) == 0){
146 if(ep - p < 2)
147 return ep+1;
148 *p++ = (dp->x[i].offset>>8) | 0xc0;
149 *p++ = dp->x[i].offset;
150 return p;
151 }
152 }
153
154 /* if there's room, enter this name in dictionary */
155 if(dp->n < Ndict){
156 if(last){
157 /* the whole name is already in dp->buf */
158 last = strchr(last, '.') + 1;
159 dp->x[dp->n].name = last;
160 dp->x[dp->n].offset = p - dp->start;
161 dp->n++;
162 } else {
163 /* add to dp->buf */
164 i = strlen(np);
165 if(dp->ep + i + 1 < &dp->buf[sizeof(dp->buf)]){
166 strcpy(dp->ep, np);
167 dp->x[dp->n].name = dp->ep;
168 last = dp->ep;
169 dp->x[dp->n].offset = p - dp->start;
170 dp->ep += i + 1;
171 dp->n++;
172 }
173 }
174 }
175
176 /* put next component into message */
177 cp = strchr(np, '.');
178 if(cp == 0){
179 i = strlen(np);
180 cp = np + i; /* point to null terminator */
181 } else {
182 i = cp - np;
183 cp++; /* point past '.' */
184 }
185 if(ep-p < i+1)
186 return ep+1;
187 *p++ = i; /* count of chars in label */
188 memcpy(p, np, i);
189 np = cp;
190 p += i;
191 }
192
193 if(p >= ep)
194 return ep+1;
195 *p++ = 0; /* add top level domain */
196
197 return p;
198 }
199
200 static uchar*
convRR2M(RR * rp,uchar * p,uchar * ep,Dict * dp)201 convRR2M(RR *rp, uchar *p, uchar *ep, Dict *dp)
202 {
203 uchar *lp, *data;
204 int len, ttl;
205 Txt *t;
206
207 NAME(rp->owner->name);
208 USHORT(rp->type);
209 USHORT(rp->owner->class);
210
211 /* egregious overuse of ttl (it's absolute time in the cache) */
212 if(rp->db)
213 ttl = rp->ttl;
214 else
215 ttl = rp->ttl - now;
216 if(ttl < 0)
217 ttl = 0;
218 ULONG(ttl);
219
220 lp = p; /* leave room for the rdata length */
221 p += 2;
222 data = p;
223
224 if(data >= ep)
225 return p+1;
226
227 switch(rp->type){
228 case Thinfo:
229 SYMBOL(rp->cpu->name);
230 SYMBOL(rp->os->name);
231 break;
232 case Tcname:
233 case Tmb:
234 case Tmd:
235 case Tmf:
236 case Tns:
237 NAME(rp->host->name);
238 break;
239 case Tmg:
240 case Tmr:
241 NAME(rp->mb->name);
242 break;
243 case Tminfo:
244 NAME(rp->rmb->name);
245 NAME(rp->mb->name);
246 break;
247 case Tmx:
248 USHORT(rp->pref);
249 NAME(rp->host->name);
250 break;
251 case Ta:
252 V4ADDR(rp->ip->name);
253 break;
254 case Taaaa:
255 V6ADDR(rp->ip->name);
256 break;
257 case Tptr:
258 NAME(rp->ptr->name);
259 break;
260 case Tsoa:
261 NAME(rp->host->name);
262 NAME(rp->rmb->name);
263 ULONG(rp->soa->serial);
264 ULONG(rp->soa->refresh);
265 ULONG(rp->soa->retry);
266 ULONG(rp->soa->expire);
267 ULONG(rp->soa->minttl);
268 break;
269 case Ttxt:
270 for(t = rp->txt; t != nil; t = t->next)
271 STRING(t->p);
272 break;
273 case Tnull:
274 BYTES(rp->null->data, rp->null->dlen);
275 break;
276 case Trp:
277 NAME(rp->rmb->name);
278 NAME(rp->rp->name);
279 break;
280 case Tkey:
281 USHORT(rp->key->flags);
282 UCHAR(rp->key->proto);
283 UCHAR(rp->key->alg);
284 BYTES(rp->key->data, rp->key->dlen);
285 break;
286 case Tsig:
287 USHORT(rp->sig->type);
288 UCHAR(rp->sig->alg);
289 UCHAR(rp->sig->labels);
290 ULONG(rp->sig->ttl);
291 ULONG(rp->sig->exp);
292 ULONG(rp->sig->incep);
293 USHORT(rp->sig->tag);
294 NAME(rp->sig->signer->name);
295 BYTES(rp->sig->data, rp->sig->dlen);
296 break;
297 case Tcert:
298 USHORT(rp->cert->type);
299 USHORT(rp->cert->tag);
300 UCHAR(rp->cert->alg);
301 BYTES(rp->cert->data, rp->cert->dlen);
302 break;
303 }
304
305 /* stuff in the rdata section length */
306 len = p - data;
307 *lp++ = len >> 8;
308 *lp = len;
309
310 return p;
311 }
312
313 static uchar*
convQ2M(RR * rp,uchar * p,uchar * ep,Dict * dp)314 convQ2M(RR *rp, uchar *p, uchar *ep, Dict *dp)
315 {
316 NAME(rp->owner->name);
317 USHORT(rp->type);
318 USHORT(rp->owner->class);
319 return p;
320 }
321
322 static uchar*
rrloop(RR * rp,int * countp,uchar * p,uchar * ep,Dict * dp,int quest)323 rrloop(RR *rp, int *countp, uchar *p, uchar *ep, Dict *dp, int quest)
324 {
325 uchar *np;
326
327 *countp = 0;
328 for(; rp && p < ep; rp = rp->next){
329 if(quest)
330 np = convQ2M(rp, p, ep, dp);
331 else
332 np = convRR2M(rp, p, ep, dp);
333 if(np > ep)
334 break;
335 p = np;
336 (*countp)++;
337 }
338 return p;
339 }
340
341 /*
342 * convert into a message
343 */
344 int
convDNS2M(DNSmsg * m,uchar * buf,int len)345 convDNS2M(DNSmsg *m, uchar *buf, int len)
346 {
347 uchar *p, *ep, *np;
348 Dict d;
349
350 d.n = 0;
351 d.start = buf;
352 d.ep = d.buf;
353 memset(buf, 0, len);
354 m->qdcount = m->ancount = m->nscount = m->arcount = 0;
355
356 /* first pack in the RR's so we can get real counts */
357 p = buf + 12;
358 ep = buf + len;
359 p = rrloop(m->qd, &m->qdcount, p, ep, &d, 1);
360 p = rrloop(m->an, &m->ancount, p, ep, &d, 0);
361 p = rrloop(m->ns, &m->nscount, p, ep, &d, 0);
362 p = rrloop(m->ar, &m->arcount, p, ep, &d, 0);
363 if(p > ep)
364 return -1;
365
366 /* now pack the rest */
367 np = p;
368 p = buf;
369 ep = buf + len;
370 USHORT(m->id);
371 USHORT(m->flags);
372 USHORT(m->qdcount);
373 USHORT(m->ancount);
374 USHORT(m->nscount);
375 USHORT(m->arcount);
376 if(p > ep)
377 return -1;
378
379 return np - buf;
380 }
381