1 /*	$NetBSD: ns_parse.c,v 1.9 2012/03/13 21:13:39 christos Exp $	*/
2 
3 /*
4  * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
5  * Copyright (c) 1996,1999 by Internet Software Consortium.
6  *
7  * Permission to use, copy, modify, and distribute this software for any
8  * purpose with or without fee is hereby granted, provided that the above
9  * copyright notice and this permission notice appear in all copies.
10  *
11  * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
12  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
13  * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
14  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
15  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
16  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
17  * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
18  */
19 
20 #include <sys/cdefs.h>
21 #ifndef lint
22 #ifdef notdef
23 static const char rcsid[] = "Id: ns_parse.c,v 1.10 2009/01/23 19:59:16 each Exp";
24 #else
25 __RCSID("$NetBSD: ns_parse.c,v 1.9 2012/03/13 21:13:39 christos Exp $");
26 #endif
27 #endif
28 
29 /* Import. */
30 
31 #include <sys/types.h>
32 
33 #include <netinet/in.h>
34 #include <arpa/nameser.h>
35 
36 #include <assert.h>
37 #include <errno.h>
38 #ifdef ANDROID_CHANGES
39 #include "resolv_private.h"
40 #else
41 #include <resolv.h>
42 #endif
43 #include <string.h>
44 
45 /* Forward. */
46 
47 static void	setsection(ns_msg *msg, ns_sect sect);
48 
49 /* Macros. */
50 
51 #define RETERR(err) do { errno = (err); return (-1); } while (/*NOTREACHED*//*CONSTCOND*/0)
52 
53 /* Public. */
54 
55 struct _ns_flagdata {  int mask, shift;  };
56 
57 /* These need to be in the same order as the nres.h:ns_flag enum. */
58 const struct _ns_flagdata _ns_flagdata[16] = {
59 	{ 0x8000, 15 },		/* qr. */
60 	{ 0x7800, 11 },		/* opcode. */
61 	{ 0x0400, 10 },		/* aa. */
62 	{ 0x0200, 9 },		/* tc. */
63 	{ 0x0100, 8 },		/* rd. */
64 	{ 0x0080, 7 },		/* ra. */
65 	{ 0x0040, 6 },		/* z. */
66 	{ 0x0020, 5 },		/* ad. */
67 	{ 0x0010, 4 },		/* cd. */
68 	{ 0x000f, 0 },		/* rcode. */
69 	{ 0x0000, 0 },		/* expansion (1/6). */
70 	{ 0x0000, 0 },		/* expansion (2/6). */
71 	{ 0x0000, 0 },		/* expansion (3/6). */
72 	{ 0x0000, 0 },		/* expansion (4/6). */
73 	{ 0x0000, 0 },		/* expansion (5/6). */
74 	{ 0x0000, 0 },		/* expansion (6/6). */
75 };
76 
ns_msg_getflag(ns_msg handle,int flag)77 int ns_msg_getflag(ns_msg handle, int flag) {
78 	return((u_int32_t)((handle)._flags & _ns_flagdata[flag].mask) >> _ns_flagdata[flag].shift);
79 }
80 
81 int
ns_skiprr(const u_char * ptr,const u_char * eom,ns_sect section,int count)82 ns_skiprr(const u_char *ptr, const u_char *eom, ns_sect section, int count) {
83 	const u_char *optr = ptr;
84 
85 	for (; count > 0; count--) {
86 		int b, rdlength;
87 
88 		b = dn_skipname(ptr, eom);
89 		if (b < 0)
90 			RETERR(EMSGSIZE);
91 		ptr += b/*Name*/ + NS_INT16SZ/*Type*/ + NS_INT16SZ/*Class*/;
92 		if (section != ns_s_qd) {
93 			if (ptr + NS_INT32SZ + NS_INT16SZ > eom)
94 				RETERR(EMSGSIZE);
95 			ptr += NS_INT32SZ/*TTL*/;
96 			NS_GET16(rdlength, ptr);
97 			ptr += rdlength/*RData*/;
98 		}
99 	}
100 	if (ptr > eom)
101 		RETERR(EMSGSIZE);
102 	_DIAGASSERT(__type_fit(int, ptr - optr));
103 	return (int)(ptr - optr);
104 }
105 
106 int
ns_initparse(const u_char * msg,int msglen,ns_msg * handle)107 ns_initparse(const u_char *msg, int msglen, ns_msg *handle) {
108 	const u_char *eom = msg + msglen;
109 	int i;
110 
111 	handle->_msg = msg;
112 	handle->_eom = eom;
113 	if (msg + NS_INT16SZ > eom)
114 		RETERR(EMSGSIZE);
115 	NS_GET16(handle->_id, msg);
116 	if (msg + NS_INT16SZ > eom)
117 		RETERR(EMSGSIZE);
118 	NS_GET16(handle->_flags, msg);
119 	for (i = 0; i < ns_s_max; i++) {
120 		if (msg + NS_INT16SZ > eom)
121 			RETERR(EMSGSIZE);
122 		NS_GET16(handle->_counts[i], msg);
123 	}
124 	for (i = 0; i < ns_s_max; i++)
125 		if (handle->_counts[i] == 0)
126 			handle->_sections[i] = NULL;
127 		else {
128 			int b = ns_skiprr(msg, eom, (ns_sect)i,
129 					  handle->_counts[i]);
130 
131 			if (b < 0)
132 				return (-1);
133 			handle->_sections[i] = msg;
134 			msg += b;
135 		}
136 	if (msg != eom)
137 		RETERR(EMSGSIZE);
138 	setsection(handle, ns_s_max);
139 	return (0);
140 }
141 
142 int
ns_parserr(ns_msg * handle,ns_sect section,int rrnum,ns_rr * rr)143 ns_parserr(ns_msg *handle, ns_sect section, int rrnum, ns_rr *rr) {
144 	int b;
145 	int tmp;
146 
147 	/* Make section right. */
148 	tmp = section;
149 	if (tmp < 0 || section >= ns_s_max)
150 		RETERR(ENODEV);
151 	if (section != handle->_sect)
152 		setsection(handle, section);
153 
154 	/* Make rrnum right. */
155 	if (rrnum == -1)
156 		rrnum = handle->_rrnum;
157 	if (rrnum < 0 || rrnum >= handle->_counts[(int)section])
158 		RETERR(ENODEV);
159 	if (rrnum < handle->_rrnum)
160 		setsection(handle, section);
161 	if (rrnum > handle->_rrnum) {
162 		b = ns_skiprr(handle->_msg_ptr, handle->_eom, section,
163 			      rrnum - handle->_rrnum);
164 
165 		if (b < 0)
166 			return (-1);
167 		handle->_msg_ptr += b;
168 		handle->_rrnum = rrnum;
169 	}
170 
171 	/* Do the parse. */
172 	b = dn_expand(handle->_msg, handle->_eom,
173 		      handle->_msg_ptr, rr->name, NS_MAXDNAME);
174 	if (b < 0)
175 		return (-1);
176 	handle->_msg_ptr += b;
177 	if (handle->_msg_ptr + NS_INT16SZ + NS_INT16SZ > handle->_eom)
178 		RETERR(EMSGSIZE);
179 	NS_GET16(rr->type, handle->_msg_ptr);
180 	NS_GET16(rr->rr_class, handle->_msg_ptr);
181 	if (section == ns_s_qd) {
182 		rr->ttl = 0;
183 		rr->rdlength = 0;
184 		rr->rdata = NULL;
185 	} else {
186 		if (handle->_msg_ptr + NS_INT32SZ + NS_INT16SZ > handle->_eom)
187 			RETERR(EMSGSIZE);
188 		NS_GET32(rr->ttl, handle->_msg_ptr);
189 		NS_GET16(rr->rdlength, handle->_msg_ptr);
190 		if (handle->_msg_ptr + rr->rdlength > handle->_eom)
191 			RETERR(EMSGSIZE);
192 		rr->rdata = handle->_msg_ptr;
193 		handle->_msg_ptr += rr->rdlength;
194 	}
195 	if (++handle->_rrnum > handle->_counts[(int)section])
196 		setsection(handle, (ns_sect)((int)section + 1));
197 
198 	/* All done. */
199 	return (0);
200 }
201 
202 /*
203  * This is identical to the above but uses network-format (uncompressed) names.
204  */
205 int
ns_parserr2(ns_msg * handle,ns_sect section,int rrnum,ns_rr2 * rr)206 ns_parserr2(ns_msg *handle, ns_sect section, int rrnum, ns_rr2 *rr) {
207 	int b;
208 	int tmp;
209 
210 	/* Make section right. */
211 	tmp = section;
212 	if (tmp < 0 || section >= ns_s_max)
213 		RETERR(ENODEV);
214 	if (section != handle->_sect)
215 		setsection(handle, section);
216 
217 	/* Make rrnum right. */
218 	if (rrnum == -1)
219 		rrnum = handle->_rrnum;
220 	if (rrnum < 0 || rrnum >= handle->_counts[(int)section])
221 		RETERR(ENODEV);
222 	if (rrnum < handle->_rrnum)
223 		setsection(handle, section);
224 	if (rrnum > handle->_rrnum) {
225 		b = ns_skiprr(handle->_msg_ptr, handle->_eom, section,
226 			      rrnum - handle->_rrnum);
227 
228 		if (b < 0)
229 			return (-1);
230 		handle->_msg_ptr += b;
231 		handle->_rrnum = rrnum;
232 	}
233 
234 	/* Do the parse. */
235 	b = ns_name_unpack2(handle->_msg, handle->_eom, handle->_msg_ptr,
236 			    rr->nname, NS_MAXNNAME, &rr->nnamel);
237 	if (b < 0)
238 		return (-1);
239 	handle->_msg_ptr += b;
240 	if (handle->_msg_ptr + NS_INT16SZ + NS_INT16SZ > handle->_eom)
241 		RETERR(EMSGSIZE);
242 	NS_GET16(rr->type, handle->_msg_ptr);
243 	NS_GET16(rr->rr_class, handle->_msg_ptr);
244 	if (section == ns_s_qd) {
245 		rr->ttl = 0;
246 		rr->rdlength = 0;
247 		rr->rdata = NULL;
248 	} else {
249 		if (handle->_msg_ptr + NS_INT32SZ + NS_INT16SZ > handle->_eom)
250 			RETERR(EMSGSIZE);
251 		NS_GET32(rr->ttl, handle->_msg_ptr);
252 		NS_GET16(rr->rdlength, handle->_msg_ptr);
253 		if (handle->_msg_ptr + rr->rdlength > handle->_eom)
254 			RETERR(EMSGSIZE);
255 		rr->rdata = handle->_msg_ptr;
256 		handle->_msg_ptr += rr->rdlength;
257 	}
258 	if (++handle->_rrnum > handle->_counts[(int)section])
259 		setsection(handle, (ns_sect)((int)section + 1));
260 
261 	/* All done. */
262 	return (0);
263 }
264 
265 /* Private. */
266 
267 static void
setsection(ns_msg * msg,ns_sect sect)268 setsection(ns_msg *msg, ns_sect sect) {
269 	msg->_sect = sect;
270 	if (sect == ns_s_max) {
271 		msg->_rrnum = -1;
272 		msg->_msg_ptr = NULL;
273 	} else {
274 		msg->_rrnum = 0;
275 		msg->_msg_ptr = msg->_sections[(int)sect];
276 	}
277 }
278