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2b778ceb | 1 | /* Copyright (C) 2004-2021 Free Software Foundation, Inc. |
28977c2c UD |
2 | This file is part of the GNU C Library. |
3 | Contributed by Ulrich Drepper <drepper@redhat.com>, 2004. | |
4 | ||
5 | The GNU C Library is free software; you can redistribute it and/or | |
6 | modify it under the terms of the GNU Lesser General Public | |
7 | License as published by the Free Software Foundation; either | |
8 | version 2.1 of the License, or (at your option) any later version. | |
9 | ||
10 | The GNU C Library is distributed in the hope that it will be useful, | |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
13 | Lesser General Public License for more details. | |
14 | ||
15 | You should have received a copy of the GNU Lesser General Public | |
59ba27a6 | 16 | License along with the GNU C Library; if not, see |
5a82c748 | 17 | <https://www.gnu.org/licenses/>. */ |
28977c2c UD |
18 | |
19 | #include <errno.h> | |
20 | #include <netdb.h> | |
21 | #include <resolv.h> | |
22 | #include <stdlib.h> | |
e054f494 | 23 | #include <stdint.h> |
28977c2c UD |
24 | #include <arpa/nameser.h> |
25 | #include <nsswitch.h> | |
352f4ff9 FW |
26 | #include <resolv/resolv_context.h> |
27 | #include <resolv/resolv-internal.h> | |
28977c2c | 28 | |
bd65a52a FW |
29 | NSS_DECLARE_MODULE_FUNCTIONS (dns) |
30 | ||
28977c2c UD |
31 | #if PACKETSZ > 65536 |
32 | # define MAXPACKET PACKETSZ | |
33 | #else | |
34 | # define MAXPACKET 65536 | |
35 | #endif | |
36 | ||
37 | ||
38 | /* We need this time later. */ | |
39 | typedef union querybuf | |
40 | { | |
41 | HEADER hdr; | |
42 | unsigned char buf[MAXPACKET]; | |
43 | } querybuf; | |
44 | ||
45 | ||
acb98cb5 UD |
46 | static const short int qtypes[] = { ns_t_a, ns_t_aaaa }; |
47 | #define nqtypes (sizeof (qtypes) / sizeof (qtypes[0])) | |
48 | ||
49 | ||
28977c2c UD |
50 | enum nss_status |
51 | _nss_dns_getcanonname_r (const char *name, char *buffer, size_t buflen, | |
52 | char **result,int *errnop, int *h_errnop) | |
53 | { | |
54 | /* Just an alibi buffer, res_nquery will allocate a real buffer for | |
55 | us. */ | |
56 | unsigned char buf[20]; | |
57 | union | |
58 | { | |
59 | querybuf *buf; | |
60 | unsigned char *ptr; | |
61 | } ansp = { .ptr = buf }; | |
10b71c3d | 62 | enum nss_status status = NSS_STATUS_UNAVAIL; |
28977c2c | 63 | |
352f4ff9 FW |
64 | struct resolv_context *ctx = __resolv_context_get (); |
65 | if (ctx == NULL) | |
66 | { | |
67 | *errnop = errno; | |
68 | *h_errnop = NETDB_INTERNAL; | |
69 | return NSS_STATUS_UNAVAIL; | |
70 | } | |
71 | ||
3207d436 | 72 | for (int i = 0; i < nqtypes; ++i) |
28977c2c | 73 | { |
352f4ff9 FW |
74 | int r = __res_context_query (ctx, name, ns_c_in, qtypes[i], |
75 | buf, sizeof (buf), &ansp.ptr, NULL, NULL, | |
76 | NULL, NULL); | |
3207d436 | 77 | if (r > 0) |
28977c2c | 78 | { |
3207d436 UD |
79 | /* We need to decode the response. Just one question record. |
80 | And if we got no answers we bail out, too. */ | |
81 | if (ansp.buf->hdr.qdcount != htons (1)) | |
82 | continue; | |
83 | ||
84 | /* Number of answers. */ | |
85 | unsigned int ancount = ntohs (ansp.buf->hdr.ancount); | |
86 | ||
87 | /* Beginning and end of the buffer with query, answer, and the | |
88 | rest. */ | |
89 | unsigned char *ptr = &ansp.buf->buf[sizeof (HEADER)]; | |
90 | unsigned char *endptr = ansp.ptr + r; | |
91 | ||
92 | /* Skip over the query. This is the name, type, and class. */ | |
93 | int s = __dn_skipname (ptr, endptr); | |
94 | if (s < 0) | |
95 | { | |
96 | unavail: | |
97 | status = NSS_STATUS_UNAVAIL; | |
98 | break; | |
99 | } | |
100 | ||
101 | /* Skip over the name and the two 16-bit values containing type | |
102 | and class. */ | |
103 | ptr += s + 2 * sizeof (uint16_t); | |
104 | ||
105 | while (ancount-- > 0) | |
106 | { | |
107 | /* Now the reply. First again the name from the query, | |
108 | then type, class, TTL, and the length of the RDATA. | |
109 | We remember the name start. */ | |
110 | unsigned char *namestart = ptr; | |
111 | s = __dn_skipname (ptr, endptr); | |
112 | if (s < 0) | |
113 | goto unavail; | |
114 | ||
115 | ptr += s; | |
116 | ||
f749498f FW |
117 | /* Check that there are enough bytes for the RR |
118 | metadata. */ | |
119 | if (endptr - ptr < 10) | |
120 | goto unavail; | |
121 | ||
3207d436 | 122 | /* Check whether type and class match. */ |
acb98cb5 UD |
123 | uint_fast16_t type; |
124 | NS_GET16 (type, ptr); | |
3207d436 UD |
125 | if (type == qtypes[i]) |
126 | { | |
127 | /* We found the record. */ | |
128 | s = __dn_expand (ansp.buf->buf, endptr, namestart, | |
129 | buffer, buflen); | |
130 | if (s < 0) | |
131 | { | |
132 | if (errno != EMSGSIZE) | |
133 | goto unavail; | |
134 | ||
135 | /* The buffer is too small. */ | |
136 | *errnop = ERANGE; | |
137 | status = NSS_STATUS_TRYAGAIN; | |
138 | h_errno = NETDB_INTERNAL; | |
139 | } | |
140 | else | |
141 | { | |
142 | /* Success. */ | |
143 | *result = buffer; | |
144 | status = NSS_STATUS_SUCCESS; | |
145 | } | |
146 | ||
147 | goto out; | |
148 | } | |
149 | ||
150 | if (type != ns_t_cname) | |
151 | goto unavail; | |
152 | ||
cd5743fd | 153 | if (__ns_get16 (ptr) != ns_c_in) |
3207d436 UD |
154 | goto unavail; |
155 | ||
f749498f | 156 | /* Also skip over class and TTL. */ |
3207d436 UD |
157 | ptr += sizeof (uint16_t) + sizeof (uint32_t); |
158 | ||
f749498f FW |
159 | /* Skip over RDATA length and RDATA itself. */ |
160 | uint16_t rdatalen = __ns_get16 (ptr); | |
161 | ptr += sizeof (uint16_t); | |
162 | /* Not enough room for RDATA. */ | |
163 | if (endptr - ptr < rdatalen) | |
164 | goto unavail; | |
165 | ptr += rdatalen; | |
3207d436 | 166 | } |
28977c2c | 167 | } |
d29fb41f FW |
168 | |
169 | /* Restore original buffer before retry. */ | |
170 | if (ansp.ptr != buf) | |
171 | { | |
172 | free (ansp.ptr); | |
173 | ansp.ptr = buf; | |
174 | } | |
28977c2c | 175 | } |
3207d436 UD |
176 | |
177 | out: | |
28977c2c UD |
178 | *h_errnop = h_errno; |
179 | ||
180 | if (ansp.ptr != buf) | |
181 | free (ansp.ptr); | |
352f4ff9 | 182 | __resolv_context_put (ctx); |
28977c2c UD |
183 | return status; |
184 | } |