3 /* Copyright 1998 by the Massachusetts Institute of Technology.
5 * Permission to use, copy, modify, and distribute this
6 * software and its documentation for any purpose and without
7 * fee is hereby granted, provided that the above copyright
8 * notice appear in all copies and that both that copyright
9 * notice and this permission notice appear in supporting
10 * documentation, and that the name of M.I.T. not be used in
11 * advertising or publicity pertaining to distribution of the
12 * software without specific, written prior permission.
13 * M.I.T. makes no representations about the suitability of
14 * this software for any purpose. It is provided "as is"
15 * without express or implied warranty.
20 #if defined(WIN32) && !defined(WATT32)
23 #include <netinet/in.h>
24 #include <arpa/nameser.h>
25 #ifdef HAVE_ARPA_NAMESER_COMPAT_H
26 #include <arpa/nameser_compat.h>
32 #include "ares_private.h" /* for the memdebug */
34 static int name_length(const unsigned char *encoded, const unsigned char *abuf,
37 /* Expand an RFC1035-encoded domain name given by encoded. The
38 * containing message is given by abuf and alen. The result given by
39 * *s, which is set to a NUL-terminated allocated buffer. *enclen is
40 * set to the length of the encoded name (not the length of the
41 * expanded name; the goal is to tell the caller how many bytes to
42 * move forward to get past the encoded name).
44 * In the simple case, an encoded name is a series of labels, each
45 * composed of a one-byte length (limited to values between 0 and 63
46 * inclusive) followed by the label contents. The name is terminated
47 * by a zero-length label.
49 * In the more complicated case, a label may be terminated by an
50 * indirection pointer, specified by two bytes with the high bits of
51 * the first byte (corresponding to INDIR_MASK) set to 11. With the
52 * two high bits of the first byte stripped off, the indirection
53 * pointer gives an offset from the beginning of the containing
54 * message with more labels to decode. Indirection can happen an
55 * arbitrary number of times, so we have to detect loops.
57 * Since the expanded name uses '.' as a label separator, we use
58 * backslashes to escape periods or backslashes in the expanded name.
61 int ares_expand_name(const unsigned char *encoded, const unsigned char *abuf,
62 int alen, char **s, long *enclen)
66 const unsigned char *p;
68 len = name_length(encoded, abuf, alen);
78 /* RFC2181 says this should be ".": the root of the DNS tree.
79 * Since this function strips trailing dots though, it becomes ""
82 *enclen = 1; /* the caller should move one byte to get past this */
86 /* No error-checking necessary; it was all done by name_length(). */
90 if ((*p & INDIR_MASK) == INDIR_MASK)
94 *enclen = p + 2 - encoded;
97 p = abuf + ((*p & ~INDIR_MASK) << 8 | *(p + 1));
105 if (*p == '.' || *p == '\\')
114 *enclen = p + 1 - encoded;
116 /* Nuke the trailing period if we wrote one. */
120 *q = 0; /* zero terminate */
125 /* Return the length of the expansion of an encoded domain name, or
126 * -1 if the encoding is invalid.
128 static int name_length(const unsigned char *encoded, const unsigned char *abuf,
131 int n = 0, offset, indir = 0;
133 /* Allow the caller to pass us abuf + alen and have us check for it. */
134 if (encoded == abuf + alen)
139 if ((*encoded & INDIR_MASK) == INDIR_MASK)
141 /* Check the offset and go there. */
142 if (encoded + 1 >= abuf + alen)
144 offset = (*encoded & ~INDIR_MASK) << 8 | *(encoded + 1);
147 encoded = abuf + offset;
149 /* If we've seen more indirects than the message length,
150 * then there's a loop.
158 if (encoded + offset + 1 >= abuf + alen)
163 n += (*encoded == '.' || *encoded == '\\') ? 2 : 1;
170 /* If there were any labels at all, then the number of dots is one
171 * less than the number of labels, so subtract one.
173 return (n) ? n - 1 : n;