1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
|
/* Copyright (C) 2004-2018 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@redhat.com>, 2004.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <errno.h>
#include <netdb.h>
#include <resolv.h>
#include <stdlib.h>
#include <stdint.h>
#include <arpa/nameser.h>
#include <nsswitch.h>
#include <resolv/resolv_context.h>
#include <resolv/resolv-internal.h>
#if PACKETSZ > 65536
# define MAXPACKET PACKETSZ
#else
# define MAXPACKET 65536
#endif
/* We need this time later. */
typedef union querybuf
{
HEADER hdr;
unsigned char buf[MAXPACKET];
} querybuf;
static const short int qtypes[] = { ns_t_a, ns_t_aaaa };
#define nqtypes (sizeof (qtypes) / sizeof (qtypes[0]))
enum nss_status
_nss_dns_getcanonname_r (const char *name, char *buffer, size_t buflen,
char **result,int *errnop, int *h_errnop)
{
/* Just an alibi buffer, res_nquery will allocate a real buffer for
us. */
unsigned char buf[20];
union
{
querybuf *buf;
unsigned char *ptr;
} ansp = { .ptr = buf };
enum nss_status status = NSS_STATUS_UNAVAIL;
struct resolv_context *ctx = __resolv_context_get ();
if (ctx == NULL)
{
*errnop = errno;
*h_errnop = NETDB_INTERNAL;
return NSS_STATUS_UNAVAIL;
}
for (int i = 0; i < nqtypes; ++i)
{
int r = __res_context_query (ctx, name, ns_c_in, qtypes[i],
buf, sizeof (buf), &ansp.ptr, NULL, NULL,
NULL, NULL);
if (r > 0)
{
/* We need to decode the response. Just one question record.
And if we got no answers we bail out, too. */
if (ansp.buf->hdr.qdcount != htons (1))
continue;
/* Number of answers. */
unsigned int ancount = ntohs (ansp.buf->hdr.ancount);
/* Beginning and end of the buffer with query, answer, and the
rest. */
unsigned char *ptr = &ansp.buf->buf[sizeof (HEADER)];
unsigned char *endptr = ansp.ptr + r;
/* Skip over the query. This is the name, type, and class. */
int s = __dn_skipname (ptr, endptr);
if (s < 0)
{
unavail:
status = NSS_STATUS_UNAVAIL;
break;
}
/* Skip over the name and the two 16-bit values containing type
and class. */
ptr += s + 2 * sizeof (uint16_t);
while (ancount-- > 0)
{
/* Now the reply. First again the name from the query,
then type, class, TTL, and the length of the RDATA.
We remember the name start. */
unsigned char *namestart = ptr;
s = __dn_skipname (ptr, endptr);
if (s < 0)
goto unavail;
ptr += s;
/* Check that there are enough bytes for the RR
metadata. */
if (endptr - ptr < 10)
goto unavail;
/* Check whether type and class match. */
uint_fast16_t type;
NS_GET16 (type, ptr);
if (type == qtypes[i])
{
/* We found the record. */
s = __dn_expand (ansp.buf->buf, endptr, namestart,
buffer, buflen);
if (s < 0)
{
if (errno != EMSGSIZE)
goto unavail;
/* The buffer is too small. */
*errnop = ERANGE;
status = NSS_STATUS_TRYAGAIN;
h_errno = NETDB_INTERNAL;
}
else
{
/* Success. */
*result = buffer;
status = NSS_STATUS_SUCCESS;
}
goto out;
}
if (type != ns_t_cname)
goto unavail;
if (__ns_get16 (ptr) != ns_c_in)
goto unavail;
/* Also skip over class and TTL. */
ptr += sizeof (uint16_t) + sizeof (uint32_t);
/* Skip over RDATA length and RDATA itself. */
uint16_t rdatalen = __ns_get16 (ptr);
ptr += sizeof (uint16_t);
/* Not enough room for RDATA. */
if (endptr - ptr < rdatalen)
goto unavail;
ptr += rdatalen;
}
}
/* Restore original buffer before retry. */
if (ansp.ptr != buf)
{
free (ansp.ptr);
ansp.ptr = buf;
}
}
out:
*h_errnop = h_errno;
if (ansp.ptr != buf)
free (ansp.ptr);
__resolv_context_put (ctx);
return status;
}
|
GitWeb