1/* De-compressing DNS domain names into binary-encoded uncompressed name.
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 <shlib-compat.h>
21#include <stddef.h>
22#include <string.h>
23
24/* Unpack a domain name from a message, source may be compressed.
25 Returns -1 if it fails, or consumed octets if it succeeds. */
26int
27___ns_name_unpack (const unsigned char *msg, const unsigned char *eom,
28 const unsigned char *src, unsigned char *dst, size_t dstsiz)
29{
30 const unsigned char *srcp, *dstlim;
31 unsigned char *dstp;
32 int n, len, checked;
33
34 len = -1;
35 checked = 0;
36 dstp = dst;
37 srcp = src;
38 dstlim = dst + dstsiz;
39 if (srcp < msg || srcp >= eom)
40 {
41 __set_errno (EMSGSIZE);
42 return -1;
43 }
44 /* Fetch next label in domain name. */
45 while ((n = *srcp++) != 0)
46 {
47 /* Check for indirection. */
48 switch (n & NS_CMPRSFLGS)
49 {
50 case 0:
51 /* Limit checks. */
52 if (n >= 64)
53 {
54 __set_errno (EMSGSIZE);
55 return -1;
56 }
57 /* NB: n + 1 and >= to cover the *dstp = '\0' assignment
58 below. */
59 if (n + 1 >= dstlim - dstp || n >= eom - srcp)
60 {
61 __set_errno (EMSGSIZE);
62 return -1;
63 }
64 checked += n + 1;
65 *dstp++ = n;
66 memcpy (dstp, srcp, n);
67 dstp += n;
68 srcp += n;
69 break;
70
71 case NS_CMPRSFLGS:
72 if (srcp >= eom)
73 {
74 __set_errno (EMSGSIZE);
75 return -1;
76 }
77 if (len < 0)
78 len = srcp - src + 1;
79 {
80 int target = ((n & 0x3f) << 8) | *srcp;
81 if (target >= eom - msg)
82 {
83 /* Out of range. */
84 __set_errno (EMSGSIZE);
85 return -1;
86 }
87 srcp = msg + target;
88 }
89 checked += 2;
90 /* Check for loops in the compressed name; if we've looked
91 at the whole message, there must be a loop. */
92 if (checked >= eom - msg)
93 {
94 __set_errno (EMSGSIZE);
95 return -1;
96 }
97 break;
98
99 default:
100 __set_errno (EMSGSIZE);
101 return -1;
102 }
103 }
104 *dstp = '\0';
105 if (len < 0)
106 len = srcp - src;
107 return len;
108}
109versioned_symbol (libc, ___ns_name_unpack, ns_name_unpack, GLIBC_2_34);
110versioned_symbol (libc, ___ns_name_unpack, __ns_name_unpack, GLIBC_PRIVATE);
111libc_hidden_ver (___ns_name_unpack, __ns_name_unpack)
112
113#if OTHER_SHLIB_COMPAT (libresolv, GLIBC_2_9, GLIBC_2_34)
114compat_symbol (libresolv, ___ns_name_unpack, ns_name_unpack, GLIBC_2_9);
115#endif
116