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
|
#include "stralloc.h"
#include "uint_t.h"
#include "byte.h"
#include "dnsresolv.h"
/**
* @file dns_txt.c
* @authors djb, fefe, feh
* @ref ucspi-tcp
* @brief DNS text query (txt)
*/
int dns_txt_packet(stralloc *out,const char *buf,unsigned int len)
{
unsigned int pos;
char header[12];
uint16 numanswers;
uint16 datalen;
char ch;
unsigned int txtlen;
int i;
int ranswers = 0;
if (!stralloc_copys(out,"")) return DNS_MEM;
pos = dns_packet_copy(buf,len,0,header,12); if (!pos) return DNS_ERR;
uint16_unpack_big(header + 6,&numanswers);
pos = dns_packet_skipname(buf,len,pos); if (!pos) return DNS_ERR;
pos += 4;
while (numanswers--) {
pos = dns_packet_skipname(buf,len,pos); if (!pos) return DNS_ERR;
pos = dns_packet_copy(buf,len,pos,header,10); if (!pos) return DNS_ERR;
uint16_unpack_big(header + 8,&datalen);
if (byte_equal(header,2,DNS_T_TXT))
if (byte_equal(header + 2,2,DNS_C_IN)) {
if (pos + datalen > len) return DNS_ERR;
txtlen = (unsigned char) buf[pos];
for (i = 1; i < datalen; ++i) {
ch = buf[pos + i];
if (i == txtlen + 1) // next label
txtlen += (unsigned char) ch + 1;
else {
if (ch < 32) ch = '?';
if (ch > 126) ch = '?';
if (!stralloc_append(out,&ch)) return DNS_MEM;
}
}
}
pos += datalen;
++ranswers;
if (numanswers) if (!stralloc_append(out,"\n")) return DNS_MEM;
}
return ranswers;
}
static char *q = 0;
int dns_txt(stralloc *out,const stralloc *fqdn)
{
int rc;
if (dns_domain_fromdot(&q,fqdn->s,fqdn->len) <= 0) return DNS_ERR;
if (dns_resolve(q,DNS_T_TXT) < 0) return DNS_ERR;
if ((rc = dns_txt_packet(out,dns_resolve_tx.packet,dns_resolve_tx.packetlen)) < 0) return DNS_ERR;
dns_transmit_free(&dns_resolve_tx);
dns_domain_free(&q);
return rc;
}
|
