1 #include "stralloc.h"
2 #include "uint16.h"
3 #include "byte.h"
4 #include "dns.h"
5
dns_txt_packet(stralloc * out,const char * buf,unsigned int len)6 int dns_txt_packet(stralloc *out,const char *buf,unsigned int len)
7 {
8 unsigned int pos;
9 char header[12];
10 uint16 numanswers;
11 uint16 datalen;
12 char ch;
13 unsigned int txtlen;
14 int i;
15
16 if (!stralloc_copys(out,"")) return -1;
17
18 pos = dns_packet_copy(buf,len,0,header,12); if (!pos) return -1;
19 uint16_unpack_big(header + 6,&numanswers);
20 pos = dns_packet_skipname(buf,len,pos); if (!pos) return -1;
21 pos += 4;
22
23 while (numanswers--) {
24 pos = dns_packet_skipname(buf,len,pos); if (!pos) return -1;
25 pos = dns_packet_copy(buf,len,pos,header,10); if (!pos) return -1;
26 uint16_unpack_big(header + 8,&datalen);
27 if (byte_equal(header,2,DNS_T_TXT))
28 if (byte_equal(header + 2,2,DNS_C_IN)) {
29 if (pos + datalen > len) return -1;
30 txtlen = 0;
31 for (i = 0;i < datalen;++i) {
32 ch = buf[pos + i];
33 if (!txtlen)
34 txtlen = (unsigned char) ch;
35 else {
36 --txtlen;
37 if (ch < 32) ch = '?';
38 if (ch > 126) ch = '?';
39 if (!stralloc_append(out,&ch)) return -1;
40 }
41 }
42 }
43 pos += datalen;
44 }
45
46 return 0;
47 }
48
49 static char *q = 0;
50
dns_txt(stralloc * out,const stralloc * fqdn)51 int dns_txt(stralloc *out,const stralloc *fqdn)
52 {
53 if (!dns_domain_fromdot(&q,fqdn->s,fqdn->len)) return -1;
54 if (dns_resolve(q,DNS_T_TXT) == -1) return -1;
55 if (dns_txt_packet(out,dns_resolve_tx.packet,dns_resolve_tx.packetlen) == -1) return -1;
56 dns_transmit_free(&dns_resolve_tx);
57 dns_domain_free(&q);
58 return 0;
59 }
60