/* vi: set sw=4 ts=4: */ //config:config NSLOOKUP //config: bool "nslookup (4.5 kb)" //config: default y //config: help //config: nslookup is a tool to query Internet name servers. //config: //config:config NSLOOKUP_BIG //config: bool "Use internal resolver code instead of libc" //config: depends on NSLOOKUP //config: default y //config: //config:config FEATURE_NSLOOKUP_LONG_OPTIONS //config: bool "Enable long options" //config: default y //config: depends on NSLOOKUP_BIG && LONG_OPTS //applet:IF_NSLOOKUP(APPLET(nslookup, BB_DIR_USR_BIN, BB_SUID_DROP)) //kbuild:lib-$(CONFIG_NSLOOKUP) += nslookup.o //usage:#define nslookup_trivial_usage //usage: "[HOST] [SERVER]" //usage:#define nslookup_full_usage "\n\n" //usage: "Query the nameserver for the IP address of the given HOST\n" //usage: "optionally using a specified DNS server" //usage: //usage:#define nslookup_example_usage //usage: "$ nslookup localhost\n" //usage: "Server: default\n" //usage: "Address: default\n" //usage: "\n" //usage: "Name: debian\n" //usage: "Address: 127.0.0.1\n" #include #include /* for IFNAMSIZ */ //#include //#include #include "libbb.h" #include "common_bufsiz.h" #if !ENABLE_NSLOOKUP_BIG /* * Mini nslookup implementation for busybox * * Copyright (C) 1999,2000 by Lineo, inc. and John Beppu * Copyright (C) 1999,2000,2001 by John Beppu * * Correct default name server display and explicit name server option * added by Ben Zeckel June 2001 * * Licensed under GPLv2 or later, see file LICENSE in this source tree. */ /* * I'm only implementing non-interactive mode; * I totally forgot nslookup even had an interactive mode. * * This applet is the only user of res_init(). Without it, * you may avoid pulling in _res global from libc. */ /* Examples of 'standard' nslookup output * $ nslookup yahoo.com * Server: 128.193.0.10 * Address: 128.193.0.10#53 * * Non-authoritative answer: * Name: yahoo.com * Address: 216.109.112.135 * Name: yahoo.com * Address: 66.94.234.13 * * $ nslookup 204.152.191.37 * Server: 128.193.4.20 * Address: 128.193.4.20#53 * * Non-authoritative answer: * 37.191.152.204.in-addr.arpa canonical name = 37.32-27.191.152.204.in-addr.arpa. * 37.32-27.191.152.204.in-addr.arpa name = zeus-pub2.kernel.org. * * Authoritative answers can be found from: * 32-27.191.152.204.in-addr.arpa nameserver = ns1.kernel.org. * 32-27.191.152.204.in-addr.arpa nameserver = ns2.kernel.org. * 32-27.191.152.204.in-addr.arpa nameserver = ns3.kernel.org. * ns1.kernel.org internet address = 140.211.167.34 * ns2.kernel.org internet address = 204.152.191.4 * ns3.kernel.org internet address = 204.152.191.36 */ static int print_host(const char *hostname, const char *header) { /* We can't use xhost2sockaddr() - we want to get ALL addresses, * not just one */ struct addrinfo *result = NULL; int rc; struct addrinfo hint; memset(&hint, 0 , sizeof(hint)); /* hint.ai_family = AF_UNSPEC; - zero anyway */ /* Needed. Or else we will get each address thrice (or more) * for each possible socket type (tcp,udp,raw...): */ hint.ai_socktype = SOCK_STREAM; // hint.ai_flags = AI_CANONNAME; rc = getaddrinfo(hostname, NULL /*service*/, &hint, &result); if (rc == 0) { struct addrinfo *cur = result; unsigned cnt = 0; printf("%-10s %s\n", header, hostname); // puts(cur->ai_canonname); ? while (cur) { char *dotted, *revhost; dotted = xmalloc_sockaddr2dotted_noport(cur->ai_addr); revhost = xmalloc_sockaddr2hostonly_noport(cur->ai_addr); printf("Address %u: %s%c", ++cnt, dotted, revhost ? ' ' : '\n'); if (revhost) { puts(revhost); if (ENABLE_FEATURE_CLEAN_UP) free(revhost); } if (ENABLE_FEATURE_CLEAN_UP) free(dotted); cur = cur->ai_next; } } else { #if ENABLE_VERBOSE_RESOLUTION_ERRORS bb_error_msg("can't resolve '%s': %s", hostname, gai_strerror(rc)); #else bb_error_msg("can't resolve '%s'", hostname); #endif } if (ENABLE_FEATURE_CLEAN_UP && result) freeaddrinfo(result); return (rc != 0); } /* lookup the default nameserver and display it */ static void server_print(void) { char *server; struct sockaddr *sa; #if ENABLE_FEATURE_IPV6 sa = (struct sockaddr*)_res._u._ext.nsaddrs[0]; if (!sa) #endif sa = (struct sockaddr*)&_res.nsaddr_list[0]; server = xmalloc_sockaddr2dotted_noport(sa); print_host(server, "Server:"); if (ENABLE_FEATURE_CLEAN_UP) free(server); bb_putchar('\n'); } /* alter the global _res nameserver structure to use an explicit dns server instead of what is in /etc/resolv.conf */ static void set_default_dns(const char *server) { len_and_sockaddr *lsa; if (!server) return; /* NB: this works even with, say, "[::1]:5353"! :) */ lsa = xhost2sockaddr(server, 53); if (lsa->u.sa.sa_family == AF_INET) { _res.nscount = 1; /* struct copy */ _res.nsaddr_list[0] = lsa->u.sin; } #if ENABLE_FEATURE_IPV6 /* Hoped libc can cope with IPv4 address there too. * No such luck, glibc 2.4 segfaults even with IPv6, * maybe I misunderstand how to make glibc use IPv6 addr? * (uclibc 0.9.31+ should work) */ if (lsa->u.sa.sa_family == AF_INET6) { // glibc neither SEGVs nor sends any dgrams with this // (strace shows no socket ops): //_res.nscount = 0; _res._u._ext.nscount = 1; /* store a pointer to part of malloc'ed lsa */ _res._u._ext.nsaddrs[0] = &lsa->u.sin6; /* must not free(lsa)! */ } #endif } int nslookup_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; int nslookup_main(int argc, char **argv) { /* We allow 1 or 2 arguments. * The first is the name to be looked up and the second is an * optional DNS server with which to do the lookup. * More than 3 arguments is an error to follow the pattern of the * standard nslookup */ if (!argv[1] || argv[1][0] == '-' || argc > 3) bb_show_usage(); /* initialize DNS structure _res used in printing the default * name server and in the explicit name server option feature. */ res_init(); /* rfc2133 says this enables IPv6 lookups */ /* (but it also says "may be enabled in /etc/resolv.conf") */ /*_res.options |= RES_USE_INET6;*/ set_default_dns(argv[2]); server_print(); /* getaddrinfo and friends are free to request a resolver * reinitialization. Just in case, set_default_dns() again * after getaddrinfo (in server_print). This reportedly helps * with bug 675 "nslookup does not properly use second argument" * at least on Debian Wheezy and Openwrt AA (eglibc based). */ set_default_dns(argv[2]); return print_host(argv[1], "Name:"); } #else /****** A version from LEDE / OpenWRT ******/ /* * musl compatible nslookup * * Copyright (C) 2017 Jo-Philipp Wich * * Permission to use, copy, modify, and/or distribute this software for any * purpose with or without fee is hereby granted, provided that the above * copyright notice and this permission notice appear in all copies. * * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ #if 0 # define dbg(...) fprintf(stderr, __VA_ARGS__) #else # define dbg(...) ((void)0) #endif struct ns { const char *name; len_and_sockaddr *lsa; int failures; int replies; }; struct query { const char *name; unsigned qlen, rlen; unsigned latency; uint8_t rcode; unsigned char query[512], reply[512]; }; static const struct { int type; const char *name; } qtypes[] = { { ns_t_soa, "SOA" }, { ns_t_ns, "NS" }, { ns_t_a, "A" }, #if ENABLE_FEATURE_IPV6 { ns_t_aaaa, "AAAA" }, #endif { ns_t_cname, "CNAME" }, { ns_t_mx, "MX" }, { ns_t_txt, "TXT" }, { ns_t_ptr, "PTR" }, { ns_t_any, "ANY" }, { } }; static const char *const rcodes[] = { "NOERROR", // 0 "FORMERR", // 1 "SERVFAIL", // 2 "NXDOMAIN", // 3 "NOTIMP", // 4 "REFUSED", // 5 "YXDOMAIN", // 6 "YXRRSET", // 7 "NXRRSET", // 8 "NOTAUTH", // 9 "NOTZONE", // 10 "11", // 11 not assigned "12", // 12 not assigned "13", // 13 not assigned "14", // 14 not assigned "15", // 15 not assigned }; #if ENABLE_FEATURE_IPV6 static const char v4_mapped[] = { 0,0,0,0,0,0,0,0,0,0,0xff,0xff }; #endif struct globals { unsigned default_port; unsigned default_retry; unsigned default_timeout; unsigned serv_count; struct ns *server; } FIX_ALIASING; #define G (*(struct globals*)bb_common_bufsiz1) #define INIT_G() do { \ setup_common_bufsiz(); \ G.default_port = 53; \ G.default_retry = 2; \ G.default_timeout = 5; \ } while (0) static int parse_reply(const unsigned char *msg, size_t len) { ns_msg handle; ns_rr rr; int i, n, rdlen; const char *format = NULL; char astr[INET6_ADDRSTRLEN], dname[MAXDNAME]; const unsigned char *cp; if (ns_initparse(msg, len, &handle) != 0) { //fprintf(stderr, "Unable to parse reply: %s\n", strerror(errno)); return -1; } for (i = 0; i < ns_msg_count(handle, ns_s_an); i++) { if (ns_parserr(&handle, ns_s_an, i, &rr) != 0) { //fprintf(stderr, "Unable to parse resource record: %s\n", strerror(errno)); return -1; } rdlen = ns_rr_rdlen(rr); switch (ns_rr_type(rr)) { case ns_t_a: if (rdlen != 4) { dbg("unexpected A record length %d\n", rdlen); return -1; } inet_ntop(AF_INET, ns_rr_rdata(rr), astr, sizeof(astr)); printf("Name:\t%s\nAddress: %s\n", ns_rr_name(rr), astr); break; #if ENABLE_FEATURE_IPV6 case ns_t_aaaa: if (rdlen != 16) { dbg("unexpected AAAA record length %d\n", rdlen); return -1; } inet_ntop(AF_INET6, ns_rr_rdata(rr), astr, sizeof(astr)); /* bind-utils-9.11.3 uses the same format for A and AAAA answers */ printf("Name:\t%s\nAddress: %s\n", ns_rr_name(rr), astr); break; #endif case ns_t_ns: if (!format) format = "%s\tnameserver = %s\n"; /* fall through */ case ns_t_cname: if (!format) format = "%s\tcanonical name = %s\n"; /* fall through */ case ns_t_ptr: if (!format) format = "%s\tname = %s\n"; if (ns_name_uncompress(ns_msg_base(handle), ns_msg_end(handle), ns_rr_rdata(rr), dname, sizeof(dname)) < 0 ) { //fprintf(stderr, "Unable to uncompress domain: %s\n", strerror(errno)); return -1; } printf(format, ns_rr_name(rr), dname); break; case ns_t_mx: if (rdlen < 2) { fprintf(stderr, "MX record too short\n"); return -1; } n = ns_get16(ns_rr_rdata(rr)); if (ns_name_uncompress(ns_msg_base(handle), ns_msg_end(handle), ns_rr_rdata(rr) + 2, dname, sizeof(dname)) < 0 ) { //fprintf(stderr, "Cannot uncompress MX domain: %s\n", strerror(errno)); return -1; } printf("%s\tmail exchanger = %d %s\n", ns_rr_name(rr), n, dname); break; case ns_t_txt: if (rdlen < 1) { //fprintf(stderr, "TXT record too short\n"); return -1; } n = *(unsigned char *)ns_rr_rdata(rr); if (n > 0) { memset(dname, 0, sizeof(dname)); memcpy(dname, ns_rr_rdata(rr) + 1, n); printf("%s\ttext = \"%s\"\n", ns_rr_name(rr), dname); } break; case ns_t_soa: if (rdlen < 20) { dbg("SOA record too short:%d\n", rdlen); return -1; } printf("%s\n", ns_rr_name(rr)); cp = ns_rr_rdata(rr); n = ns_name_uncompress(ns_msg_base(handle), ns_msg_end(handle), cp, dname, sizeof(dname)); if (n < 0) { //fprintf(stderr, "Unable to uncompress domain: %s\n", strerror(errno)); return -1; } printf("\torigin = %s\n", dname); cp += n; n = ns_name_uncompress(ns_msg_base(handle), ns_msg_end(handle), cp, dname, sizeof(dname)); if (n < 0) { //fprintf(stderr, "Unable to uncompress domain: %s\n", strerror(errno)); return -1; } printf("\tmail addr = %s\n", dname); cp += n; printf("\tserial = %lu\n", ns_get32(cp)); cp += 4; printf("\trefresh = %lu\n", ns_get32(cp)); cp += 4; printf("\tretry = %lu\n", ns_get32(cp)); cp += 4; printf("\texpire = %lu\n", ns_get32(cp)); cp += 4; printf("\tminimum = %lu\n", ns_get32(cp)); break; default: break; } } return i; } static char *make_ptr(char resbuf[80], const char *addrstr) { unsigned char addr[16]; int i; #if ENABLE_FEATURE_IPV6 if (inet_pton(AF_INET6, addrstr, addr)) { if (memcmp(addr, v4_mapped, 12) != 0) { char *ptr = resbuf; for (i = 0; i < 16; i++) { *ptr++ = 0x20 | bb_hexdigits_upcase[(unsigned char)addr[15 - i] & 0xf]; *ptr++ = '.'; *ptr++ = 0x20 | bb_hexdigits_upcase[(unsigned char)addr[15 - i] >> 4]; *ptr++ = '.'; } strcpy(ptr, "ip6.arpa"); } else { sprintf(resbuf, "%u.%u.%u.%u.in-addr.arpa", addr[15], addr[14], addr[13], addr[12]); } return resbuf; } #endif if (inet_pton(AF_INET, addrstr, addr)) { sprintf(resbuf, "%u.%u.%u.%u.in-addr.arpa", addr[3], addr[2], addr[1], addr[0]); return resbuf; } return NULL; } /* * Function logic borrowed & modified from musl libc, res_msend.c * n_queries is always > 0. */ static int send_queries(struct ns *ns, struct query *query, int n_queries) { len_and_sockaddr *local_lsa; struct pollfd pfd; int servfail_retry = 0; int n_replies = 0; int save_idx = 0; unsigned retry_interval; unsigned timeout = G.default_timeout * 1000; unsigned tstart, tsent, tcur; pfd.events = POLLIN; pfd.fd = xsocket_type(&local_lsa, ns->lsa->u.sa.sa_family, SOCK_DGRAM); /* * local_lsa has "null" address and port 0 now. * bind() ensures we have a *particular port* selected by kernel * and remembered in fd, thus later recv(fd) * receives only packets sent to this port. */ xbind(pfd.fd, &local_lsa->u.sa, local_lsa->len); free(local_lsa); /* Make read/writes know the destination */ xconnect(pfd.fd, &ns->lsa->u.sa, ns->lsa->len); ndelay_on(pfd.fd); retry_interval = timeout / G.default_retry; tstart = tcur = monotonic_ms(); goto send; while (tcur - tstart < timeout) { int qn; int recvlen; if (tcur - tsent >= retry_interval) { send: for (qn = 0; qn < n_queries; qn++) { if (query[qn].rlen) continue; if (write(pfd.fd, query[qn].query, query[qn].qlen) < 0) { bb_perror_msg("write to '%s'", ns->name); n_replies = -1; /* "no go, try next server" */ goto ret; } dbg("query %u sent\n", qn); } tsent = tcur; servfail_retry = 2 * n_queries; } /* Wait for a response, or until time to retry */ if (poll(&pfd, 1, retry_interval - (tcur - tsent)) <= 0) goto next; recvlen = read(pfd.fd, query[save_idx].reply, sizeof(query[0].reply)); /* Error/non-identifiable packet */ if (recvlen < 4) { dbg("read is too short:%d\n", recvlen); goto next; } /* Find which query this answer goes with, if any */ qn = save_idx; for (;;) { if (memcmp(query[save_idx].reply, query[qn].query, 2) == 0) { dbg("response matches query %u\n", qn); break; } if (++qn >= n_queries) { dbg("response does not match any query\n"); goto next; } } if (query[qn].rlen) { dbg("dropped duplicate response to query %u\n", qn); goto next; } ns->replies++; query[qn].rcode = query[save_idx].reply[3] & 15; dbg("query %u rcode:%s\n", qn, rcodes[query[qn].rcode]); /* Only accept positive or negative responses; * retry immediately on server failure, and ignore * all other codes such as refusal. */ switch (query[qn].rcode) { case 0: case 3: break; case 2: if (servfail_retry) { servfail_retry--; ns->failures++; write(pfd.fd, query[qn].query, query[qn].qlen); dbg("query %u resent\n", qn); } /* fall through */ default: next: tcur = monotonic_ms(); continue; } /* Store answer */ n_replies++; query[qn].rlen = recvlen; tcur = monotonic_ms(); query[qn].latency = tcur - tstart; if (qn != save_idx) { /* "wrong" receive buffer, move to correct one */ memcpy(query[qn].reply, query[save_idx].reply, recvlen); continue; } /* query[0..save_idx] have replies, move to next one, if exists */ for (;;) { save_idx++; if (save_idx >= n_queries) goto ret; /* all are full: we have all results */ if (!query[save_idx].rlen) break; /* this one is empty */ } } /* while() */ ret: close(pfd.fd); return n_replies; } static void add_ns(const char *addr) { struct ns *ns; unsigned count; dbg("%s: addr:'%s'\n", __func__, addr); count = G.serv_count++; G.server = xrealloc_vector(G.server, /*8=2^3:*/ 3, count); ns = &G.server[count]; ns->name = addr; ns->lsa = xhost2sockaddr(addr, 53); /*ns->replies = 0; - already is */ /*ns->failures = 0; - already is */ } static void parse_resolvconf(void) { FILE *resolv; resolv = fopen("/etc/resolv.conf", "r"); if (resolv) { char line[128], *p; while (fgets(line, sizeof(line), resolv)) { p = strtok(line, " \t\n"); if (!p || strcmp(p, "nameserver") != 0) continue; p = strtok(NULL, " \t\n"); if (!p) continue; add_ns(xstrdup(p)); } fclose(resolv); } } static struct query *add_query(struct query **queries, int *n_queries, int type, const char *dname) { struct query *new_q; int pos; ssize_t qlen; pos = *n_queries; *n_queries = pos + 1; *queries = new_q = xrealloc(*queries, sizeof(**queries) * (pos + 1)); dbg("new query#%u type %u for '%s'\n", pos, type, dname); new_q += pos; memset(new_q, 0, sizeof(*new_q)); qlen = res_mkquery(QUERY, dname, C_IN, type, NULL, 0, NULL, new_q->query, sizeof(new_q->query)); new_q->qlen = qlen; new_q->name = dname; return new_q; } int nslookup_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; int nslookup_main(int argc UNUSED_PARAM, char **argv) { struct ns *ns; struct query *queries; llist_t *type_strings; int n_queries; unsigned types; int rc; int opts; enum { OPT_stats = (1 << 4), }; INIT_G(); type_strings = NULL; #if ENABLE_FEATURE_NSLOOKUP_LONG_OPTIONS opts = getopt32long(argv, "^" "+" /* '+': stop at first non-option (why?) */ "q:*p:+r:+t:+s" "\0" "-1:q::", /* minimum 1 arg, -q is a list */ "type\0" Required_argument "q" "querytype\0" Required_argument "q" "port\0" Required_argument "p" "retry\0" Required_argument "r" "timeout\0" Required_argument "t" "stats\0" No_argument "s", &type_strings, &G.default_port, &G.default_retry, &G.default_timeout ); #else opts = getopt32(argv, "^" "+" /* '+': stop at first non-option (why?) */ "q:*p:+r:+t:+s" "\0" "-1:q::", /* minimum 1 arg, -q is a list */ &type_strings, &G.default_port, &G.default_retry, &G.default_timeout ); #endif if (G.default_port > 65535) bb_error_msg_and_die("invalid server port"); if (G.default_retry == 0) bb_error_msg_and_die("invalid retry value"); if (G.default_timeout == 0) bb_error_msg_and_die("invalid timeout value"); types = 0; while (type_strings) { int c; char *ptr, *chr; ptr = llist_pop(&type_strings); /* skip leading text, e.g. when invoked with -querytype=AAAA */ chr = strchr(ptr, '='); if (chr) ptr = chr + 1; for (c = 0;; c++) { if (!qtypes[c].name) bb_error_msg_and_die("invalid query type \"%s\"", ptr); if (strcmp(qtypes[c].name, ptr) == 0) break; } types |= (1 << c); } argv += optind; n_queries = 0; queries = NULL; do { if (types == 0) { /* No explicit type given, guess query type. * If we can convert the domain argument into a ptr (means that * inet_pton() could read it) we assume a PTR request, else * we issue A+AAAA queries and switch to an output format * mimicking the one of the traditional nslookup applet. */ char *ptr; char buf80[80]; ptr = make_ptr(buf80, *argv); if (ptr) { add_query(&queries, &n_queries, T_PTR, ptr); } else { add_query(&queries, &n_queries, T_A, *argv); #if ENABLE_FEATURE_IPV6 add_query(&queries, &n_queries, T_AAAA, *argv); #endif } } else { int c; for (c = 0; qtypes[c].name; c++) { if (types & (1 << c)) add_query(&queries, &n_queries, qtypes[c].type, *argv); } } argv++; } while (argv[0] && argv[1]); /* Use given DNS server if present */ if (argv[0]) { add_ns(argv[0]); } else { parse_resolvconf(); /* Fall back to localhost if we could not find NS in resolv.conf */ if (G.serv_count == 0) add_ns("127.0.0.1"); } for (rc = 0; rc < G.serv_count; rc++) { int c = send_queries(&G.server[rc], queries, n_queries); if (c > 0) break; /* c = 0: timed out waiting for replies */ /* c < 0: error (message already printed) */ rc++; if (rc >= G.serv_count) { fprintf(stderr, ";; connection timed out; no servers could be reached\n\n"); return EXIT_FAILURE; } } printf("Server:\t\t%s\n", G.server[rc].name); printf("Address:\t%s\n", xmalloc_sockaddr2dotted(&G.server[rc].lsa->u.sa)); /* In "Address", bind-utils-9.11.3 show port after a hash: "1.2.3.4#53" */ /* Should we do the same? */ if (opts & OPT_stats) { printf("Replies:\t%d\n", G.server[rc].replies); printf("Failures:\t%d\n", G.server[rc].failures); } printf("\n"); for (rc = 0; rc < n_queries; rc++) { int c; if (opts & OPT_stats) { printf("Query #%d completed in %ums:\n", rc, queries[rc].latency); } if (queries[rc].rcode != 0) { printf("** server can't find %s: %s\n", queries[rc].name, rcodes[queries[rc].rcode]); continue; } c = 0; if (queries[rc].rlen) { HEADER *header; header = (HEADER *)queries[rc].reply; if (!header->aa) printf("Non-authoritative answer:\n"); c = parse_reply(queries[rc].reply, queries[rc].rlen); } if (c == 0) printf("*** Can't find %s: No answer\n", queries[rc].name); else if (c < 0) printf("*** Can't find %s: Parse error\n", queries[rc].name); bb_putchar('\n'); } if (ENABLE_FEATURE_CLEAN_UP) { free(ns); if (n_queries) free(queries); } return EXIT_SUCCESS; } #endif