1 /* host.c - DNS lookup utility
2  *
3  * Copyright 2014 Rich Felker <dalias@aerifal.cx>
4  *
5  * No standard, but there's a version in bind9
6 
7 USE_HOST(NEWTOY(host, "<1>2avt:", TOYFLAG_USR|TOYFLAG_BIN))
8 
9 config HOST
10   bool "host"
11   default n
12   help
13     usage: host [-av] [-t TYPE] NAME [SERVER]
14 
15     Perform DNS lookup on NAME, which can be a domain name to lookup,
16     or an IPv4 dotted or IPv6 colon-separated address to reverse lookup.
17     SERVER (if present) is the DNS server to use.
18 
19     -a	no idea
20     -t	not a clue
21     -v	verbose
22 */
23 
24 #define FOR_host
25 #include "toys.h"
26 
27 GLOBALS(
28   char *type_str;
29 )
30 
31 #include <resolv.h>
32 
33 #define PL_IP 1
34 #define PL_NAME 2
35 #define PL_DATA 3
36 #define PL_TEXT 4
37 #define PL_SOA 5
38 #define PL_MX 6
39 #define PL_SRV 7
40 
41 static const struct rrt {
42   const char *name;
43   const char *msg;
44   int pl;
45   int af;
46 } rrt[] = {
47   [1] = { "A", "has address", PL_IP, AF_INET },
48   [28] = { "AAAA", "has address", PL_IP, AF_INET6 },
49   [2] = { "NS", "name server", PL_NAME },
50   [5] = { "CNAME", "is a nickname for", PL_NAME },
51   [16] = { "TXT", "descriptive text", PL_TEXT },
52   [6] = { "SOA", "start of authority", PL_SOA },
53   [12] = { "PTR", "domain name pointer", PL_NAME },
54   [15] = { "MX", "mail is handled", PL_MX },
55   [33] = { "SRV", "mail is handled", PL_SRV },
56   [255] = { "*", 0, 0 },
57 };
58 
59 static const char rct[16][32] = {
60   "Success",
61   "Format error",
62   "Server failure",
63   "Non-existant domain",
64   "Not implemented",
65   "Refused",
66 };
67 
host_main(void)68 void host_main(void)
69 {
70   int verbose=(toys.optflags & (FLAG_a|FLAG_v)), type,
71       i, j, ret, sec, count, rcode, qlen, alen, pllen = 0;
72   unsigned ttl, pri, v[5];
73   unsigned char qbuf[280], abuf[512], *p;
74   char *name, *nsname, rrname[256], plname[640], ptrbuf[128];
75   struct addrinfo *ai, iplit_hints = { .ai_flags = AI_NUMERICHOST };
76 
77   name = *toys.optargs;
78   nsname = toys.optargs[1];
79 
80   if (!TT.type_str && (toys.optflags & FLAG_a)) TT.type_str = "255";
81   if (!getaddrinfo(name, 0, &iplit_hints, &ai)) {
82     unsigned char *a;
83     static const char xdigits[] = "0123456789abcdef";
84 
85     if (ai->ai_family == AF_INET) {
86       a = (void *)&((struct sockaddr_in *)ai->ai_addr)->sin_addr;
87       snprintf(ptrbuf, sizeof(ptrbuf), "%d.%d.%d.%d.in-addr.arpa",
88         a[3], a[2], a[1], a[0]);
89     } else if (ai->ai_family == AF_INET6) {
90       a = (void *)&((struct sockaddr_in6 *)ai->ai_addr)->sin6_addr;
91       for (j=0, i=15; i>=0; i--) {
92         ptrbuf[j++] = xdigits[a[i]&15];
93         ptrbuf[j++] = '.';
94         ptrbuf[j++] = xdigits[a[i]>>4];
95         ptrbuf[j++] = '.';
96       }
97       strcpy(ptrbuf+j, "ip6.arpa");
98     }
99     name = ptrbuf;
100     if (!TT.type_str) TT.type_str="12";
101   } else if (!TT.type_str) TT.type_str="1";
102 
103   if (TT.type_str[0]-'0' < 10u) type = atoi(TT.type_str);
104   else {
105     type = -1;
106     for (i=0; i<ARRAY_LEN(rrt); i++) {
107       if (rrt[i].name && !strcasecmp(TT.type_str, rrt[i].name)) {
108         type = i;
109         break;
110       }
111     }
112     if (!strcasecmp(TT.type_str, "any")) type = 255;
113     if (type < 0) error_exit("Invalid query type: %s", TT.type_str);
114   }
115 
116   qlen = res_mkquery(0, name, 1, type, 0, 0, 0, qbuf, sizeof qbuf);
117   if (qlen < 0) error_exit("Invalid query parameters: %s", name);
118 
119   if (nsname) {
120     struct addrinfo ns_hints = { .ai_socktype = SOCK_DGRAM };
121 
122     if ((ret = getaddrinfo(nsname, "53", &ns_hints, &ai)) < 0)
123       error_exit("Error looking up server name: %s", gai_strerror(ret));
124     int s = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
125     if (s < 0 || connect(s, ai->ai_addr, ai->ai_addrlen) < 0)
126       perror_exit("Socket error");
127     setsockopt(s, SOL_SOCKET, SO_RCVTIMEO, &(struct timeval){ .tv_sec = 5 },
128       sizeof(struct timeval));
129     printf("Using domain server %s:\n", nsname);
130     send(s, qbuf, qlen, 0);
131     alen = recv(s, abuf, sizeof abuf, 0);
132   } else alen = res_send(qbuf, qlen, abuf, sizeof abuf);
133 
134   if (alen < 12) error_exit("Host not found.");
135 
136   rcode = abuf[3] & 15;
137 
138   if (verbose) {
139     printf("rcode = %d (%s), ancount = %d\n",
140       rcode, rct[rcode], 256*abuf[6] + abuf[7]);
141     if (!(abuf[2] & 4)) printf("The following answer is not authoritative:\n");
142   }
143 
144   if (rcode) error_exit("Host not found.");
145 
146   p = abuf + 12;
147   for (sec=0; sec<4; sec++) {
148     count = 256*abuf[4+2*sec] + abuf[5+2*sec];
149     if (verbose && count>0 && sec>1)
150       puts(sec==2 ? "For authoritative answers, see:"
151         : "Additional information:");
152 
153     for (; count--; p += pllen) {
154       p += dn_expand(abuf, abuf+alen, p, rrname, sizeof(rrname));
155       type = (p[0]<<8) + p[1];
156       p += 4;
157       if (!sec) continue;
158       ttl = (p[0]<<24)+(p[1]<<16)+(p[2]<<8)+p[3];
159       p += 4;
160       pllen = (p[0]<<8) + p[1];
161       p += 2;
162 
163       switch (type<sizeof(rrt)/sizeof(*rrt) ? rrt[type].pl : 0) {
164       case PL_IP:
165         inet_ntop(rrt[type].af, p, plname, sizeof plname);
166         break;
167       case PL_NAME:
168         dn_expand(abuf, abuf+alen, p, plname, sizeof plname);
169         break;
170       case PL_TEXT:
171         snprintf(plname, sizeof plname, "\"%.*s\"", pllen, p);
172         break;
173       case PL_SOA:
174         i = dn_expand(abuf, abuf+alen, p, plname, sizeof plname - 1);
175         strcat(plname, " ");
176         i += dn_expand(abuf, abuf+alen, p+i, plname+strlen(plname),
177           sizeof(plname)-strlen(plname));
178         for (j=0; j<5; j++)
179           v[j] = (p[i+4*j]<<24)+(p[1+i+4*j]<<16)+(p[2+i+4*j]<<8)+p[3+i+4*j];
180         snprintf(plname+strlen(plname), sizeof(plname)-strlen(plname),
181           "(\n\t\t%u\t;serial (version)\n"
182           "\t\t%u\t;refresh period\n"
183           "\t\t%u\t;retry interval\n"
184           "\t\t%u\t;expire time\n"
185           "\t\t%u\t;default ttl\n"
186           "\t\t)", v[0], v[1], v[2], v[3], v[4]);
187         break;
188       case PL_MX:
189         pri = (p[0]<<8)+p[1];
190         snprintf(plname, sizeof(plname), verbose ? "%d " : "(pri=%d) by ", pri);
191         dn_expand(abuf, abuf+alen, p+2, plname+strlen(plname),
192           sizeof plname - strlen(plname));
193         break;
194       case PL_SRV:
195         for (j=0; j<3; j++) v[j] = (p[2*j]<<8) + p[1+2*j];
196         snprintf(plname, sizeof(plname), "%u %u %u ", v[0], v[1], v[2]);
197         dn_expand(abuf, abuf+alen, p+6, plname+strlen(plname),
198           sizeof plname - strlen(plname));
199         break;
200       default:
201         printf("%s unsupported RR type %u\n", rrname, type);
202         continue;
203       }
204 
205       if (verbose)
206         printf("%s\t%u\tIN %s\t%s\n", rrname, ttl, rrt[type].name, plname);
207       else if (rrt[type].msg)
208         printf("%s %s %s\n", rrname, rrt[type].msg, plname);
209     }
210     if (!verbose && sec==1) break;
211   }
212 
213   toys.exitval = rcode;
214 }
215