1/* Compression of DNS domain names.
2 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
3 * Copyright (c) 1996,1999 by Internet Software Consortium.
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
15 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17
18#include <arpa/nameser.h>
19#include <errno.h>
20#include <string.h>
21#include <shlib-compat.h>
22
23/* Thinking in noninternationalized USASCII (per the DNS spec),
24 convert this character to lower case if it's upper case. */
25static int
26mklower (int ch)
27{
28 if (ch >= 'A' && ch <= 'Z')
29 return ch - 'A' + 'a';
30 return ch;
31}
32
33/* Search for the counted-label name in an array of compressed names.
34 Returns the offset from MSG if found, or -1.
35
36 DNPTRS is the pointer to the first name on the list, not the
37 pointer to the start of the message. */
38static int
39dn_find (const unsigned char *domain, const unsigned char *msg,
40 const unsigned char **dnptrs,
41 const unsigned char **lastdnptr)
42{
43 const unsigned char *dn, *cp, *sp;
44 const unsigned char **cpp;
45 unsigned int n;
46
47 for (cpp = dnptrs; cpp < lastdnptr; cpp++)
48 {
49 sp = *cpp;
50 /* Terminate search on: root label, compression pointer, unusable
51 offset. */
52 while (*sp != 0 && (*sp & NS_CMPRSFLGS) == 0 && (sp - msg) < 0x4000)
53 {
54 dn = domain;
55 cp = sp;
56 while ((n = *cp++) != 0)
57 {
58 /* Check for indirection. */
59 switch (n & NS_CMPRSFLGS)
60 {
61 case 0: /* Normal case, n == len. */
62 if (n != *dn++)
63 goto next;
64
65 for (; n > 0; n--)
66 if (mklower (*dn++) != mklower (*cp++))
67 goto next;
68 /* Is next root for both? */
69 if (*dn == '\0' && *cp == '\0')
70 return sp - msg;
71 if (*dn)
72 continue;
73 goto next;
74 case NS_CMPRSFLGS: /* Indirection. */
75 cp = msg + (((n & 0x3f) << 8) | *cp);
76 break;
77
78 default: /* Illegal type. */
79 __set_errno (EMSGSIZE);
80 return -1;
81 }
82 }
83 next: ;
84 sp += *sp + 1;
85 }
86 }
87 __set_errno (ENOENT);
88 return -1;
89}
90
91/* Packs domain name SRC into DST. Returns size of the compressed
92 name, or -1.
93
94 DNPTRS is an array of pointers to previous compressed names.
95 DNPTRS[0] is a pointer to the beginning of the message. The array
96 ends with NULL. LASTDNPTR is a pointer to the end of the array
97 pointed to by 'dnptrs'.
98
99 The list of pointers in DNPTRS is updated for labels inserted into
100 the message as we compress the name. If DNPTRS is NULL, we don't
101 try to compress names. If LASTDNPTR is NULL, we don't update the
102 list. */
103int
104___ns_name_pack (const unsigned char *src, unsigned char *dst, int dstsiz,
105 const unsigned char **dnptrs, const unsigned char **lastdnptr)
106{
107 unsigned char *dstp;
108 const unsigned char **cpp, **lpp, *eob, *msg;
109 const unsigned char *srcp;
110 int n, l, first = 1;
111
112 srcp = src;
113 dstp = dst;
114 eob = dstp + dstsiz;
115 lpp = cpp = NULL;
116 if (dnptrs != NULL)
117 {
118 if ((msg = *dnptrs++) != NULL)
119 {
120 for (cpp = dnptrs; *cpp != NULL; cpp++)
121 ;
122 lpp = cpp; /* End of list to search. */
123 }
124 }
125 else
126 msg = NULL;
127
128 /* Make sure the domain we are about to add is legal. */
129 l = 0;
130 do
131 {
132 n = *srcp;
133 if (n >= 64)
134 {
135 __set_errno (EMSGSIZE);
136 return -1;
137 }
138 l += n + 1;
139 if (l > MAXCDNAME)
140 {
141 __set_errno (EMSGSIZE);
142 return -1;
143 }
144 srcp += n + 1;
145 }
146 while (n != 0);
147
148 /* from here on we need to reset compression pointer array on error */
149 srcp = src;
150 do
151 {
152 /* Look to see if we can use pointers. */
153 n = *srcp;
154 if (n != 0 && msg != NULL)
155 {
156 l = dn_find (srcp, msg, dnptrs, lpp);
157 if (l >= 0)
158 {
159 if (eob - dstp <= 1)
160 goto cleanup;
161 *dstp++ = (l >> 8) | NS_CMPRSFLGS;
162 *dstp++ = l % 256;
163 return dstp - dst;
164 }
165 /* Not found, save it. */
166 if (lastdnptr != NULL && cpp < lastdnptr - 1
167 && (dstp - msg) < 0x4000 && first)
168 {
169 *cpp++ = dstp;
170 *cpp = NULL;
171 first = 0;
172 }
173 }
174 /* Copy label to buffer. */
175 if (n >= 64)
176 /* Should not happen. */
177 goto cleanup;
178 if (n + 1 > eob - dstp)
179 goto cleanup;
180 memcpy (dstp, srcp, n + 1);
181 srcp += n + 1;
182 dstp += n + 1;
183 }
184 while (n != 0);
185
186 if (dstp > eob)
187 {
188 cleanup:
189 if (msg != NULL)
190 *lpp = NULL;
191 __set_errno (EMSGSIZE);
192 return -1;
193 }
194 return dstp - dst;
195}
196versioned_symbol (libc, ___ns_name_pack, ns_name_pack, GLIBC_2_34);
197versioned_symbol (libc, ___ns_name_pack, __ns_name_pack, GLIBC_PRIVATE);
198libc_hidden_ver (___ns_name_pack, __ns_name_pack)
199
200#if OTHER_SHLIB_COMPAT (libresolv, GLIBC_2_9, GLIBC_2_34)
201compat_symbol (libresolv, ___ns_name_pack, ns_name_pack, GLIBC_2_9);
202#endif
203