/* * A rewrite of Darren Reeds original res.c As there is nothing * left of Darrens original code, this is now licensed by the hybrid group. * (Well, some of the function names are the same, and bits of the structs..) * You can use it where it is useful, free even. Buy us a beer and stuff. * * The authors takes no responsibility for any damage or loss * of property which results from the use of this software. * * $Id: res.c 3301 2007-03-28 15:04:06Z jilles $ * from Hybrid Id: res.c 459 2006-02-12 22:21:37Z db $ * * July 1999 - Rewrote a bunch of stuff here. Change hostent builder code, * added callbacks and reference counting of returned hostents. * --Bleep (Thomas Helvey ) * * This was all needlessly complicated for irc. Simplified. No more hostent * All we really care about is the IP -> hostname mappings. Thats all. * * Apr 28, 2003 --cryogen and Dianora * * DNS server flooding lessened, AAAA-or-A lookup removed, ip6.int support * removed, various robustness fixes * * 2006 --jilles and nenolod * * Resend queries to other servers if the DNS server replies with an error or * an invalid response. Also, avoid servers that return errors or invalid * responses. * * October 2012 --mr_flea */ #include "stdinc.h" #include "ircd_defs.h" #include "common.h" #include "ircd.h" #include "res.h" #include "reslib.h" #include "match.h" #include "numeric.h" #include "client.h" /* SNO_* */ #include "s_assert.h" #include "logger.h" #include "send.h" #if (CHAR_BIT != 8) #error this code needs to be able to address individual octets #endif static PF res_readreply; #define MAXPACKET 1024 /* rfc sez 512 but we expand names so ... */ #define RES_MAXALIASES 35 /* maximum aliases allowed */ #define RES_MAXADDRS 35 /* maximum addresses allowed */ #define AR_TTL 600 /* TTL in seconds for dns cache entries */ /* RFC 1104/1105 wasn't very helpful about what these fields * should be named, so for now, we'll just name them this way. * we probably should look at what named calls them or something. */ #define TYPE_SIZE (size_t)2 #define CLASS_SIZE (size_t)2 #define TTL_SIZE (size_t)4 #define RDLENGTH_SIZE (size_t)2 #define ANSWER_FIXED_SIZE (TYPE_SIZE + CLASS_SIZE + TTL_SIZE + RDLENGTH_SIZE) struct reslist { rb_dlink_node node; int id; time_t ttl; char type; char queryname[IRCD_RES_HOSTLEN + 1]; /* name currently being queried */ char retries; /* retry counter */ char sends; /* number of sends (>1 means resent) */ time_t sentat; time_t timeout; unsigned int lastns; /* index of last server sent to */ struct rb_sockaddr_storage addr; char *name; struct DNSQuery *query; /* query callback for this request */ }; static rb_fde_t *res_fd; static rb_dlink_list request_list = { NULL, NULL, 0 }; static int ns_failure_count[IRCD_MAXNS]; /* timeouts and invalid/failed replies */ static void rem_request(struct reslist *request); static struct reslist *make_request(struct DNSQuery *query); static void do_query_name(struct DNSQuery *query, const char *name, struct reslist *request, int); static void do_query_number(struct DNSQuery *query, const struct rb_sockaddr_storage *, struct reslist *request); static void query_name(struct reslist *request); static int send_res_msg(const char *buf, int len, int count); static void resend_query(struct reslist *request); static int check_question(struct reslist *request, HEADER * header, char *buf, char *eob); static int proc_answer(struct reslist *request, HEADER * header, char *, char *); static struct reslist *find_id(int id); static struct DNSReply *make_dnsreply(struct reslist *request); /* * int * res_ourserver(inp) * looks up "inp" in irc_nsaddr_list[] * returns: * server ID or -1 for not found * author: * paul vixie, 29may94 * revised for ircd, cryogen(stu) may03 * slightly modified for charybdis, mr_flea oct12 */ static int res_ourserver(const struct rb_sockaddr_storage *inp) { #ifdef RB_IPV6 const struct sockaddr_in6 *v6; const struct sockaddr_in6 *v6in = (const struct sockaddr_in6 *)inp; #endif const struct sockaddr_in *v4; const struct sockaddr_in *v4in = (const struct sockaddr_in *)inp; int ns; for (ns = 0; ns < irc_nscount; ns++) { const struct rb_sockaddr_storage *srv = &irc_nsaddr_list[ns]; if (srv->ss_family != inp->ss_family) continue; #ifdef RB_IPV6 v6 = (const struct sockaddr_in6 *)srv; #endif v4 = (const struct sockaddr_in *)srv; /* could probably just memcmp(srv, inp, srv.ss_len) here * but we'll err on the side of caution - stu */ switch (srv->ss_family) { #ifdef RB_IPV6 case AF_INET6: if (v6->sin6_port == v6in->sin6_port) if ((memcmp(&v6->sin6_addr.s6_addr, &v6in->sin6_addr.s6_addr, sizeof(struct in6_addr)) == 0) || (memcmp(&v6->sin6_addr.s6_addr, &in6addr_any, sizeof(struct in6_addr)) == 0)) { return ns; } break; #endif case AF_INET: if (v4->sin_port == v4in->sin_port) if ((v4->sin_addr.s_addr == INADDR_ANY) || (v4->sin_addr.s_addr == v4in->sin_addr.s_addr)) { return ns; } break; default: break; } } return -1; } /* * timeout_query_list - Remove queries from the list which have been * there too long without being resolved. */ static time_t timeout_query_list(time_t now) { rb_dlink_node *ptr; rb_dlink_node *next_ptr; struct reslist *request; time_t next_time = 0; time_t timeout = 0; RB_DLINK_FOREACH_SAFE(ptr, next_ptr, request_list.head) { request = ptr->data; timeout = request->sentat + request->timeout; if (now >= timeout) { ns_failure_count[request->lastns]++; request->sentat = now; request->timeout += request->timeout; resend_query(request); } if ((next_time == 0) || timeout < next_time) { next_time = timeout; } } return (next_time > now) ? next_time : (now + AR_TTL); } /* * timeout_resolver - check request list */ static void timeout_resolver(void *notused) { timeout_query_list(rb_current_time()); } static struct ev_entry *timeout_resolver_ev = NULL; /* * start_resolver - do everything we need to read the resolv.conf file * and initialize the resolver file descriptor if needed */ static void start_resolver(void) { int i; irc_res_init(); for (i = 0; i < irc_nscount; i++) ns_failure_count[i] = 0; if (res_fd == NULL) { if ((res_fd = rb_socket(irc_nsaddr_list[0].ss_family, SOCK_DGRAM, 0, "UDP resolver socket")) == NULL) return; /* At the moment, the resolver FD data is global .. */ rb_setselect(res_fd, RB_SELECT_READ, res_readreply, NULL); timeout_resolver_ev = rb_event_add("timeout_resolver", timeout_resolver, NULL, 1); } } /* * init_resolver - initialize resolver and resolver library */ void init_resolver(void) { #ifdef HAVE_SRAND48 srand48(rb_current_time()); #endif start_resolver(); } /* * restart_resolver - reread resolv.conf, reopen socket */ void restart_resolver(void) { rb_close(res_fd); res_fd = NULL; rb_event_delete(timeout_resolver_ev); /* -ddosen */ start_resolver(); } /* * add_local_domain - Add the domain to hostname, if it is missing * (as suggested by eps@TOASTER.SFSU.EDU) */ void add_local_domain(char *hname, size_t size) { /* try to fix up unqualified names */ if (strchr(hname, '.') == NULL) { if (irc_domain[0]) { size_t len = strlen(hname); if ((strlen(irc_domain) + len + 2) < size) { hname[len++] = '.'; strcpy(hname + len, irc_domain); } } } } /* * rem_request - remove a request from the list. * This must also free any memory that has been allocated for * temporary storage of DNS results. */ static void rem_request(struct reslist *request) { rb_dlinkDelete(&request->node, &request_list); rb_free(request->name); rb_free(request); } /* * make_request - Create a DNS request record for the server. */ static struct reslist *make_request(struct DNSQuery *query) { struct reslist *request = rb_malloc(sizeof(struct reslist)); request->sentat = rb_current_time(); request->retries = 3; request->timeout = 4; /* start at 4 and exponential inc. */ request->query = query; /* * generate a unique id * NOTE: we don't have to worry about converting this to and from * network byte order, the nameserver does not interpret this value * and returns it unchanged * * we generate an id per request now (instead of per send) to allow * late replies to be used. */ #ifdef HAVE_LRAND48 do { request->id = (request->id + lrand48()) & 0xffff; } while (find_id(request->id)); #else int k = 0; struct timeval tv; gettimeofday(&tv, NULL); do { request->id = (request->id + k + tv.tv_usec) & 0xffff; k++; } while (find_id(request->id)); #endif /* HAVE_LRAND48 */ rb_dlinkAdd(request, &request->node, &request_list); return request; } /* * delete_resolver_queries - cleanup outstanding queries * for which there no longer exist clients or conf lines. */ void delete_resolver_queries(const struct DNSQuery *query) { rb_dlink_node *ptr; rb_dlink_node *next_ptr; struct reslist *request; RB_DLINK_FOREACH_SAFE(ptr, next_ptr, request_list.head) { if ((request = ptr->data) != NULL) { if (query == request->query) rem_request(request); } } } /* * retryfreq - determine how many queries to wait before resending * if there have been that many consecutive timeouts */ static int retryfreq(int timeouts) { switch (timeouts) { case 1: return 3; case 2: return 9; case 3: return 27; case 4: return 81; default: return 243; } } /* * send_res_msg - sends msg to a nameserver. * This should reflect /etc/resolv.conf. * Returns number of nameserver successfully sent to * or -1 if no successful sends. */ static int send_res_msg(const char *msg, int len, int rcount) { int i; int ns; static int retrycnt; retrycnt++; /* First try a nameserver that seems to work. * Every once in a while, try a possibly broken one to check * if it is working again. */ for (i = 0; i < irc_nscount; i++) { ns = (i + rcount - 1) % irc_nscount; if (ns_failure_count[ns] && retrycnt % retryfreq(ns_failure_count[ns])) continue; if (sendto(rb_get_fd(res_fd), msg, len, 0, (struct sockaddr *)&(irc_nsaddr_list[ns]), GET_SS_LEN(&irc_nsaddr_list[ns])) == len) return ns; } /* No known working nameservers, try some broken one. */ for (i = 0; i < irc_nscount; i++) { ns = (i + rcount - 1) % irc_nscount; if (!ns_failure_count[ns]) continue; if (sendto(rb_get_fd(res_fd), msg, len, 0, (struct sockaddr *)&(irc_nsaddr_list[ns]), GET_SS_LEN(&irc_nsaddr_list[ns])) == len) return ns; } return -1; } /* * find_id - find a dns request id (id is determined by dn_mkquery) */ static struct reslist *find_id(int id) { rb_dlink_node *ptr; struct reslist *request; RB_DLINK_FOREACH(ptr, request_list.head) { request = ptr->data; if (request->id == id) return (request); } return (NULL); } /* * gethost_byname_type - get host address from name * */ void gethost_byname_type(const char *name, struct DNSQuery *query, int type) { assert(name != 0); do_query_name(query, name, NULL, type); } /* * gethost_byaddr - get host name from address */ void gethost_byaddr(const struct rb_sockaddr_storage *addr, struct DNSQuery *query) { do_query_number(query, addr, NULL); } /* * do_query_name - nameserver lookup name */ static void do_query_name(struct DNSQuery *query, const char *name, struct reslist *request, int type) { char host_name[IRCD_RES_HOSTLEN + 1]; rb_strlcpy(host_name, name, IRCD_RES_HOSTLEN + 1); add_local_domain(host_name, IRCD_RES_HOSTLEN); if (request == NULL) { request = make_request(query); request->name = (char *)rb_malloc(strlen(host_name) + 1); strcpy(request->name, host_name); } rb_strlcpy(request->queryname, host_name, sizeof(request->queryname)); request->type = type; query_name(request); } /* * do_query_number - Use this to do reverse IP# lookups. */ static void do_query_number(struct DNSQuery *query, const struct rb_sockaddr_storage *addr, struct reslist *request) { const unsigned char *cp; if (request == NULL) { request = make_request(query); memcpy(&request->addr, addr, sizeof(struct rb_sockaddr_storage)); request->name = (char *)rb_malloc(IRCD_RES_HOSTLEN + 1); } if (addr->ss_family == AF_INET) { const struct sockaddr_in *v4 = (const struct sockaddr_in *)addr; cp = (const unsigned char *)&v4->sin_addr.s_addr; rb_sprintf(request->queryname, "%u.%u.%u.%u.in-addr.arpa", (unsigned int)(cp[3]), (unsigned int)(cp[2]), (unsigned int)(cp[1]), (unsigned int)(cp[0])); } #ifdef RB_IPV6 else if (addr->ss_family == AF_INET6) { const struct sockaddr_in6 *v6 = (const struct sockaddr_in6 *)addr; cp = (const unsigned char *)&v6->sin6_addr.s6_addr; (void)sprintf(request->queryname, "%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x." "%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.ip6.arpa", (unsigned int)(cp[15] & 0xf), (unsigned int)(cp[15] >> 4), (unsigned int)(cp[14] & 0xf), (unsigned int)(cp[14] >> 4), (unsigned int)(cp[13] & 0xf), (unsigned int)(cp[13] >> 4), (unsigned int)(cp[12] & 0xf), (unsigned int)(cp[12] >> 4), (unsigned int)(cp[11] & 0xf), (unsigned int)(cp[11] >> 4), (unsigned int)(cp[10] & 0xf), (unsigned int)(cp[10] >> 4), (unsigned int)(cp[9] & 0xf), (unsigned int)(cp[9] >> 4), (unsigned int)(cp[8] & 0xf), (unsigned int)(cp[8] >> 4), (unsigned int)(cp[7] & 0xf), (unsigned int)(cp[7] >> 4), (unsigned int)(cp[6] & 0xf), (unsigned int)(cp[6] >> 4), (unsigned int)(cp[5] & 0xf), (unsigned int)(cp[5] >> 4), (unsigned int)(cp[4] & 0xf), (unsigned int)(cp[4] >> 4), (unsigned int)(cp[3] & 0xf), (unsigned int)(cp[3] >> 4), (unsigned int)(cp[2] & 0xf), (unsigned int)(cp[2] >> 4), (unsigned int)(cp[1] & 0xf), (unsigned int)(cp[1] >> 4), (unsigned int)(cp[0] & 0xf), (unsigned int)(cp[0] >> 4)); } #endif request->type = T_PTR; query_name(request); } /* * query_name - generate a query based on class, type and name. */ static void query_name(struct reslist *request) { char buf[MAXPACKET]; int request_len = 0; int ns; memset(buf, 0, sizeof(buf)); if ((request_len = irc_res_mkquery(request->queryname, C_IN, request->type, (unsigned char *)buf, sizeof(buf))) > 0) { HEADER *header = (HEADER *) buf; header->id = request->id; ++request->sends; ns = send_res_msg(buf, request_len, request->sends); if (ns != -1) request->lastns = ns; } } static void resend_query(struct reslist *request) { if (--request->retries <= 0) { (*request->query->callback) (request->query->ptr, NULL); rem_request(request); return; } switch (request->type) { case T_PTR: do_query_number(NULL, &request->addr, request); break; case T_A: #ifdef RB_IPV6 case T_AAAA: #endif do_query_name(NULL, request->name, request, request->type); break; default: break; } } /* * check_question - check if the reply really belongs to the * name we queried (to guard against late replies from previous * queries with the same id). */ static int check_question(struct reslist *request, HEADER * header, char *buf, char *eob) { char hostbuf[IRCD_RES_HOSTLEN + 1]; /* working buffer */ unsigned char *current; /* current position in buf */ int n; /* temp count */ current = (unsigned char *)buf + sizeof(HEADER); if (header->qdcount != 1) return 0; n = irc_dn_expand((unsigned char *)buf, (unsigned char *)eob, current, hostbuf, sizeof(hostbuf)); if (n <= 0) return 0; if (strcasecmp(hostbuf, request->queryname)) return 0; return 1; } /* * proc_answer - process name server reply */ static int proc_answer(struct reslist *request, HEADER * header, char *buf, char *eob) { char hostbuf[IRCD_RES_HOSTLEN + 100]; /* working buffer */ unsigned char *current; /* current position in buf */ int query_class; /* answer class */ int type; /* answer type */ int n; /* temp count */ int rd_length; struct sockaddr_in *v4; /* conversion */ #ifdef RB_IPV6 struct sockaddr_in6 *v6; #endif current = (unsigned char *)buf + sizeof(HEADER); for (; header->qdcount > 0; --header->qdcount) { if ((n = irc_dn_skipname(current, (unsigned char *)eob)) < 0) return 0; current += (size_t) n + QFIXEDSZ; } /* * process each answer sent to us blech. */ while (header->ancount > 0 && (char *)current < eob) { header->ancount--; n = irc_dn_expand((unsigned char *)buf, (unsigned char *)eob, current, hostbuf, sizeof(hostbuf)); if (n < 0) { /* * broken message */ return (0); } else if (n == 0) { /* * no more answers left */ return (0); } hostbuf[IRCD_RES_HOSTLEN] = '\0'; /* With Address arithmetic you have to be very anal * this code was not working on alpha due to that * (spotted by rodder/jailbird/dianora) */ current += (size_t) n; if (!(((char *)current + ANSWER_FIXED_SIZE) < eob)) break; type = irc_ns_get16(current); current += TYPE_SIZE; query_class = irc_ns_get16(current); current += CLASS_SIZE; request->ttl = irc_ns_get32(current); current += TTL_SIZE; rd_length = irc_ns_get16(current); current += RDLENGTH_SIZE; /* * Wait to set request->type until we verify this structure */ switch (type) { case T_A: if (request->type != T_A) return (0); /* * check for invalid rd_length or too many addresses */ if (rd_length != sizeof(struct in_addr)) return (0); v4 = (struct sockaddr_in *)&request->addr; SET_SS_LEN(&request->addr, sizeof(struct sockaddr_in)); v4->sin_family = AF_INET; memcpy(&v4->sin_addr, current, sizeof(struct in_addr)); return (1); break; #ifdef RB_IPV6 case T_AAAA: if (request->type != T_AAAA) return (0); if (rd_length != sizeof(struct in6_addr)) return (0); SET_SS_LEN(&request->addr, sizeof(struct sockaddr_in6)); v6 = (struct sockaddr_in6 *)&request->addr; v6->sin6_family = AF_INET6; memcpy(&v6->sin6_addr, current, sizeof(struct in6_addr)); return (1); break; #endif case T_PTR: if (request->type != T_PTR) return (0); n = irc_dn_expand((unsigned char *)buf, (unsigned char *)eob, current, hostbuf, sizeof(hostbuf)); if (n < 0) return (0); /* broken message */ else if (n == 0) return (0); /* no more answers left */ rb_strlcpy(request->name, hostbuf, IRCD_RES_HOSTLEN + 1); return (1); break; case T_CNAME: /* real answer will follow */ current += rd_length; break; default: /* XXX I'd rather just throw away the entire bogus thing * but its possible its just a broken nameserver with still * valid answers. But lets do some rudimentary logging for now... */ ilog(L_MAIN, "irc_res.c bogus type %d", type); break; } } return (1); } /* * res_read_single_reply - read a dns reply from the nameserver and process it. * Return value: 1 if a packet was read, 0 otherwise */ static int res_read_single_reply(rb_fde_t *F, void *data) { char buf[sizeof(HEADER) + MAXPACKET] /* Sparc and alpha need 16bit-alignment for accessing header->id * (which is uint16_t). Because of the header = (HEADER*) buf; * lateron, this is neeeded. --FaUl */ #if defined(__sparc__) || defined(__alpha__) __attribute__ ((aligned(16))) #endif ; HEADER *header; struct reslist *request = NULL; struct DNSReply *reply = NULL; int rc; int answer_count; socklen_t len = sizeof(struct rb_sockaddr_storage); struct rb_sockaddr_storage lsin; int ns; rc = recvfrom(rb_get_fd(F), buf, sizeof(buf), 0, (struct sockaddr *)&lsin, &len); /* No packet */ if (rc == 0 || rc == -1) return 0; /* Too small */ if (rc <= (int)(sizeof(HEADER))) return 1; /* * convert DNS reply reader from Network byte order to CPU byte order. */ header = (HEADER *) buf; header->ancount = ntohs(header->ancount); header->qdcount = ntohs(header->qdcount); header->nscount = ntohs(header->nscount); header->arcount = ntohs(header->arcount); /* * response for an id which we have already received an answer for * just ignore this response. */ if (0 == (request = find_id(header->id))) return 1; /* * check against possibly fake replies */ ns = res_ourserver(&lsin); if (ns == -1) return 1; if (ns != request->lastns) { /* * We'll accept the late reply, but penalize it a little more to make * sure a laggy server doesn't end up favored. */ ns_failure_count[ns] += 3; } if (!check_question(request, header, buf, buf + rc)) return 1; if ((header->rcode != NO_ERRORS) || (header->ancount == 0)) { /* * RFC 2136 states that in the event of a server returning SERVFAIL * or NOTIMP, the request should be resent to the next server. * Additionally, if the server refuses our query, resend it as well. * -- mr_flea */ if (SERVFAIL == header->rcode || NOTIMP == header->rcode || REFUSED == header->rcode) { ns_failure_count[ns]++; resend_query(request); } else { /* * Either a fatal error was returned or no answer. Cancel the * request. */ if (NXDOMAIN == header->rcode) { /* If the rcode is NXDOMAIN, treat it as a good response. */ ns_failure_count[ns] /= 4; } (*request->query->callback) (request->query->ptr, NULL); rem_request(request); } return 1; } /* * If this fails there was an error decoding the received packet. * -- jilles */ answer_count = proc_answer(request, header, buf, buf + rc); if (answer_count) { if (request->type == T_PTR) { if (request->name == NULL) { /* * Got a PTR response with no name, something strange is * happening. Try another DNS server. */ ns_failure_count[ns]++; resend_query(request); return 1; } /* * Lookup the 'authoritative' name that we were given for the * ip#. */ #ifdef RB_IPV6 if (request->addr.ss_family == AF_INET6) gethost_byname_type(request->name, request->query, T_AAAA); else #endif gethost_byname_type(request->name, request->query, T_A); rem_request(request); } else { /* * got a name and address response, client resolved */ reply = make_dnsreply(request); (*request->query->callback) (request->query->ptr, reply); rb_free(reply); rem_request(request); } ns_failure_count[ns] /= 4; } else { /* Invalid or corrupt reply - try another resolver. */ ns_failure_count[ns]++; resend_query(request); } return 1; } static void res_readreply(rb_fde_t *F, void *data) { while (res_read_single_reply(F, data)) ; rb_setselect(F, RB_SELECT_READ, res_readreply, NULL); } static struct DNSReply *make_dnsreply(struct reslist *request) { struct DNSReply *cp; s_assert(request != 0); cp = (struct DNSReply *)rb_malloc(sizeof(struct DNSReply)); cp->h_name = request->name; memcpy(&cp->addr, &request->addr, sizeof(cp->addr)); return (cp); } void report_dns_servers(struct Client *source_p) { int i; char ipaddr[128]; for (i = 0; i < irc_nscount; i++) { if (!rb_inet_ntop_sock((struct sockaddr *)&(irc_nsaddr_list[i]), ipaddr, sizeof ipaddr)) rb_strlcpy(ipaddr, "?", sizeof ipaddr); sendto_one_numeric(source_p, RPL_STATSDEBUG, "A %s %d", ipaddr, ns_failure_count[i]); } }