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
7USE_HOST(NEWTOY(host, "<1>2avt:", TOYFLAG_USR|TOYFLAG_BIN))
8
9config 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 seprated 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
27GLOBALS(
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
41static 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
59static const char rct[16][32] = {
60  "Success",
61  "Format error",
62  "Server failure",
63  "Non-existant domain",
64  "Not implemented",
65  "Refused",
66};
67
68void 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[64];
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 < sizeof rrt / sizeof *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