/* * ircd-hybrid: an advanced, lightweight Internet Relay Chat Daemon (ircd) * * Copyright (c) 1997-2014 ircd-hybrid development team * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 * USA */ /*! \file irc_res.c * \brief ircd resolver functions * \version $Id$ */ /* * 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. * * $Id$ * * 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 */ #include "stdinc.h" #include "list.h" #include "client.h" #include "event.h" #include "irc_string.h" #include "ircd.h" #include "numeric.h" #include "rng_mt.h" #include "fdlist.h" #include "s_bsd.h" #include "log.h" #include "s_misc.h" #include "send.h" #include "memory.h" #include "mempool.h" #include "irc_res.h" #include "irc_reslib.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) typedef enum { REQ_IDLE, /* We're doing not much at all */ REQ_PTR, /* Looking up a PTR */ REQ_A, /* Looking up an A, possibly because AAAA failed */ #ifdef IPV6 REQ_AAAA, /* Looking up an AAAA */ #endif REQ_CNAME /* We got a CNAME in response, we better get a real answer next */ } request_state; struct reslist { dlink_node node; int id; int sent; /* number of requests sent */ request_state state; /* State the resolver machine is in */ time_t ttl; char type; char retries; /* retry counter */ char sends; /* number of sends (>1 means resent) */ char resend; /* send flag. 0 == dont resend */ time_t sentat; time_t timeout; struct irc_ssaddr addr; char *name; dns_callback_fnc callback; void *callback_ctx; }; static fde_t ResolverFileDescriptor; static dlink_list request_list = { NULL, NULL, 0 }; static mp_pool_t *dns_pool = NULL; static void rem_request(struct reslist *); static struct reslist *make_request(dns_callback_fnc, void *); static void do_query_name(dns_callback_fnc, void *, const char *, struct reslist *, int); static void do_query_number(dns_callback_fnc, void *, const struct irc_ssaddr *, struct reslist *); static void query_name(const char *, int, int, struct reslist *); static int send_res_msg(const char *, int, int); static void resend_query(struct reslist *); static int proc_answer(struct reslist *, HEADER *, char *, char *); static struct reslist *find_id(int); /* * int * res_ourserver(inp) * looks up "inp" in irc_nsaddr_list[] * returns: * 0 : not found * >0 : found * author: * paul vixie, 29may94 * revised for ircd, cryogen(stu) may03 */ static int res_ourserver(const struct irc_ssaddr *inp) { #ifdef 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 irc_ssaddr *srv = &irc_nsaddr_list[ns]; #ifdef 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 air on the side of caution - stu * */ switch (srv->ss.ss_family) { #ifdef IPV6 case AF_INET6: if (srv->ss.ss_family == inp->ss.ss_family) if (v6->sin6_port == v6in->sin6_port) if (!memcmp(&v6->sin6_addr.s6_addr, &v6in->sin6_addr.s6_addr, sizeof(struct in6_addr))) return 1; break; #endif case AF_INET: if (srv->ss.ss_family == inp->ss.ss_family) if (v4->sin_port == v4in->sin_port) if (v4->sin_addr.s_addr == v4in->sin_addr.s_addr) return 1; break; default: break; } } return 0; } /* * 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) { dlink_node *ptr; dlink_node *next_ptr; struct reslist *request; time_t next_time = 0; time_t timeout = 0; DLINK_FOREACH_SAFE(ptr, next_ptr, request_list.head) { request = ptr->data; timeout = request->sentat + request->timeout; if (now >= timeout) { if (--request->retries <= 0) { (*request->callback)(request->callback_ctx, NULL, NULL); rem_request(request); continue; } else { 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(CurrentTime); } /* * 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) { irc_res_init(); if (!ResolverFileDescriptor.flags.open) { if (comm_open(&ResolverFileDescriptor, irc_nsaddr_list[0].ss.ss_family, SOCK_DGRAM, 0, "Resolver socket") == -1) return; /* At the moment, the resolver FD data is global .. */ comm_setselect(&ResolverFileDescriptor, COMM_SELECT_READ, res_readreply, NULL, 0); eventAdd("timeout_resolver", timeout_resolver, NULL, 1); } } /* * init_resolver - initialize resolver and resolver library */ void init_resolver(void) { dns_pool = mp_pool_new(sizeof(struct reslist), MP_CHUNK_SIZE_DNS); memset(&ResolverFileDescriptor, 0, sizeof(fde_t)); start_resolver(); } /* * restart_resolver - reread resolv.conf, reopen socket */ void restart_resolver(void) { fd_close(&ResolverFileDescriptor); eventDelete(timeout_resolver, NULL); /* -ddosen */ start_resolver(); } /* * 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) { dlinkDelete(&request->node, &request_list); MyFree(request->name); mp_pool_release(request); } /* * make_request - Create a DNS request record for the server. */ static struct reslist * make_request(dns_callback_fnc callback, void *ctx) { struct reslist *request = mp_pool_get(dns_pool); memset(request, 0, sizeof(*request)); request->sentat = CurrentTime; request->retries = 2; request->resend = 1; request->timeout = 4; /* start at 4 and exponential inc. */ request->state = REQ_IDLE; request->callback = callback; request->callback_ctx = ctx; 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 void *vptr) { dlink_node *ptr = NULL, *next_ptr = NULL; DLINK_FOREACH_SAFE(ptr, next_ptr, request_list.head) { struct reslist *request = ptr->data; if (request->callback_ctx == vptr) rem_request(request); } } /* * send_res_msg - sends msg to all nameservers found in the "_res" structure. * This should reflect /etc/resolv.conf. We will get responses * which arent needed but is easier than checking to see if nameserver * isnt present. Returns number of messages successfully sent to * nameservers or -1 if no successful sends. */ static int send_res_msg(const char *msg, int len, int rcount) { int i; int sent = 0; int max_queries = IRCD_MIN(irc_nscount, rcount); /* RES_PRIMARY option is not implemented * if (res.options & RES_PRIMARY || 0 == max_queries) */ if (max_queries == 0) max_queries = 1; for (i = 0; i < max_queries; i++) { if (sendto(ResolverFileDescriptor.fd, msg, len, 0, (struct sockaddr*)&(irc_nsaddr_list[i]), irc_nsaddr_list[i].ss_len) == len) ++sent; } return sent; } /* * find_id - find a dns request id (id is determined by dn_mkquery) */ static struct reslist * find_id(int id) { dlink_node *ptr = NULL; DLINK_FOREACH(ptr, request_list.head) { struct reslist *request = ptr->data; if (request->id == id) return request; } return NULL; } /* * gethost_byname_type - get host address from name * */ void gethost_byname_type(dns_callback_fnc callback, void *ctx, const char *name, int type) { assert(name != NULL); do_query_name(callback, ctx, name, NULL, type); } /* * gethost_byname - wrapper for _type - send T_AAAA first if IPV6 supported */ void gethost_byname(dns_callback_fnc callback, void *ctx, const char *name) { #ifdef IPV6 gethost_byname_type(callback, ctx, name, T_AAAA); #else gethost_byname_type(callback, ctx, name, T_A); #endif } /* * gethost_byaddr - get host name from address */ void gethost_byaddr(dns_callback_fnc callback, void *ctx, const struct irc_ssaddr *addr) { do_query_number(callback, ctx, addr, NULL); } /* * do_query_name - nameserver lookup name */ static void do_query_name(dns_callback_fnc callback, void *ctx, const char *name, struct reslist *request, int type) { char host_name[HOSTLEN + 1]; strlcpy(host_name, name, sizeof(host_name)); if (request == NULL) { request = make_request(callback, ctx); request->name = MyMalloc(strlen(host_name) + 1); request->type = type; strcpy(request->name, host_name); #ifdef IPV6 if (type != T_A) request->state = REQ_AAAA; else #endif request->state = REQ_A; } request->type = type; query_name(host_name, C_IN, type, request); } /* * do_query_number - Use this to do reverse IP# lookups. */ static void do_query_number(dns_callback_fnc callback, void *ctx, const struct irc_ssaddr *addr, struct reslist *request) { char ipbuf[128]; const unsigned char *cp; if (addr->ss.ss_family == AF_INET) { const struct sockaddr_in *v4 = (const struct sockaddr_in *)addr; cp = (const unsigned char *)&v4->sin_addr.s_addr; snprintf(ipbuf, sizeof(ipbuf), "%u.%u.%u.%u.in-addr.arpa.", (unsigned int)(cp[3]), (unsigned int)(cp[2]), (unsigned int)(cp[1]), (unsigned int)(cp[0])); } #ifdef IPV6 else if (addr->ss.ss_family == AF_INET6) { const struct sockaddr_in6 *v6 = (const struct sockaddr_in6 *)addr; cp = (const unsigned char *)&v6->sin6_addr.s6_addr; snprintf(ipbuf, sizeof(ipbuf), "%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 if (request == NULL) { request = make_request(callback, ctx); request->type = T_PTR; memcpy(&request->addr, addr, sizeof(struct irc_ssaddr)); request->name = MyMalloc(HOSTLEN + 1); } query_name(ipbuf, C_IN, T_PTR, request); } /* * query_name - generate a query based on class, type and name. */ static void query_name(const char *name, int query_class, int type, struct reslist *request) { char buf[MAXPACKET]; int request_len = 0; memset(buf, 0, sizeof(buf)); if ((request_len = irc_res_mkquery(name, query_class, type, (unsigned char *)buf, sizeof(buf))) > 0) { HEADER *header = (HEADER *)buf; /* * generate an 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 */ do header->id = (header->id + genrand_int32()) & 0xffff; while (find_id(header->id)); request->id = header->id; ++request->sends; request->sent += send_res_msg(buf, request_len, request->sends); } } static void resend_query(struct reslist *request) { if (request->resend == 0) return; switch (request->type) { case T_PTR: do_query_number(NULL, NULL, &request->addr, request); break; case T_A: do_query_name(NULL, NULL, request->name, request, request->type); break; #ifdef IPV6 case T_AAAA: /* didnt work, try A */ if (request->state == REQ_AAAA) do_query_name(NULL, NULL, request->name, request, T_A); #endif default: break; } } /* * proc_answer - process name server reply */ static int proc_answer(struct reslist *request, HEADER *header, char *buf, char *eob) { char hostbuf[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 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) break; 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 */ || n == 0 /* no more answers left */) return 0; hostbuf[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; request->addr.ss_len = sizeof(struct sockaddr_in); v4->sin_family = AF_INET; memcpy(&v4->sin_addr, current, sizeof(struct in_addr)); return 1; break; #ifdef IPV6 case T_AAAA: if (request->type != T_AAAA) return 0; if (rd_length != sizeof(struct in6_addr)) return 0; request->addr.ss_len = 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 /* broken message */ || n == 0 /* no more answers left */) return 0; strlcpy(request->name, hostbuf, HOSTLEN + 1); return 1; break; case T_CNAME: /* first check we already havent started looking into a cname */ if (request->type != T_PTR) return 0; if (request->state == REQ_CNAME) { n = irc_dn_expand((unsigned char *)buf, (unsigned char *)eob, current, hostbuf, sizeof(hostbuf)); if (n < 0) return 0; return 1; } request->state = REQ_CNAME; 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(LOG_TYPE_IRCD, "irc_res.c bogus type %d", type); break; } } return 1; } /* * res_readreply - read a dns reply from the nameserver and process it. */ static void res_readreply(fde_t *fd, 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; int rc; socklen_t len = sizeof(struct irc_ssaddr); struct irc_ssaddr lsin; rc = recvfrom(fd->fd, buf, sizeof(buf), 0, (struct sockaddr *)&lsin, &len); /* Re-schedule a read *after* recvfrom, or we'll be registering * interest where it'll instantly be ready for read :-) -- adrian */ comm_setselect(fd, COMM_SELECT_READ, res_readreply, NULL, 0); /* Better to cast the sizeof instead of rc */ if (rc <= (int)(sizeof(HEADER))) return; /* * 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); /* * check against possibly fake replies */ if (!res_ourserver(&lsin)) return; /* * response for an id which we have already received an answer for * just ignore this response. */ if (!(request = find_id(header->id))) return; if ((header->rcode != NO_ERRORS) || (header->ancount == 0)) { if (header->rcode == SERVFAIL || header->rcode == NXDOMAIN) { /* * If a bad error was returned, stop here and don't * send any more (no retries granted). */ (*request->callback)(request->callback_ctx, NULL, NULL); rem_request(request); } #ifdef IPV6 else { /* * If we havent already tried this, and we're looking up AAAA, try A * now */ if (request->state == REQ_AAAA && request->type == T_AAAA) { request->timeout += 4; resend_query(request); } } #endif return; } /* * If this fails there was an error decoding the received packet, * try it again and hope it works the next time. */ if (proc_answer(request, header, buf, buf + rc)) { if (request->type == T_PTR) { if (request->name == NULL) { /* * got a PTR response with no name, something bogus is happening * don't bother trying again, the client address doesn't resolve */ (*request->callback)(request->callback_ctx, NULL, NULL); rem_request(request); return; } /* * Lookup the 'authoritative' name that we were given for the * ip#. * */ #ifdef IPV6 if (request->addr.ss.ss_family == AF_INET6) gethost_byname_type(request->callback, request->callback_ctx, request->name, T_AAAA); else #endif gethost_byname_type(request->callback, request->callback_ctx, request->name, T_A); rem_request(request); } else { /* * got a name and address response, client resolved */ (*request->callback)(request->callback_ctx, &request->addr, request->name); rem_request(request); } } else if (!request->sent) { /* XXX - we got a response for a query we didn't send with a valid id? * this should never happen, bail here and leave the client unresolved */ assert(0); /* XXX don't leak it */ rem_request(request); } } void report_dns_servers(struct Client *source_p) { int i; char ipaddr[HOSTIPLEN + 1]; for (i = 0; i < irc_nscount; i++) { getnameinfo((struct sockaddr *)&(irc_nsaddr_list[i]), irc_nsaddr_list[i].ss_len, ipaddr, sizeof(ipaddr), NULL, 0, NI_NUMERICHOST); sendto_one(source_p, form_str(RPL_STATSALINE), me.name, source_p->name, ipaddr); } }