/* * res.c: resolver related code * * Portions are: * Copyright (C) 2008-2012 ircd-ratbox development team * Copyright (C) 2005,2008 Aaron Sethman * * $Id: res.c 29221 2015-12-10 19:54:15Z androsyn $ * * This is base on the resolver from charybdis, which in turn is based on the * resolver from hybrid. * * The original comments follow below: * * 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. * * from charybdis 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 * */ #include #include "setup.h" #include "res.h" #include "reslib.h" 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) #ifdef RB_IPV6 extern struct in6_addr ipv6_addr; #endif extern struct in_addr ipv4_addr; extern struct rb_sockaddr_storage irc_nsaddr_list[]; extern int irc_nscount; struct reslist { rb_dlink_node node; int id; int sent; /* number of requests sent */ time_t ttl; char type; char queryname[128]; /* name currently being queried */ char retries; /* retry counter */ char sends; /* number of sends (>1 means resent) */ time_t sentat; time_t timeout; struct rb_sockaddr_storage addr; char *name; struct DNSQuery *query; /* query callback for this request */ rb_fde_t *ipv4_F; /* socket to send request on */ rb_fde_t *ipv6_F; }; static rb_dlink_list request_list = { NULL, NULL, 0 }; 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(void *buf, int len, struct reslist *request); 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(uint16_t id); static struct DNSReply *make_dnsreply(struct reslist *request); static int generate_random_port(void); /* * 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 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]; #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 air on the side of caution - stu */ switch (GET_SS_FAMILY(srv)) { #ifdef RB_IPV6 case AF_INET6: if(GET_SS_FAMILY(srv) == GET_SS_FAMILY(inp)) 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 1; break; #endif case AF_INET: if(GET_SS_FAMILY(srv) == GET_SS_FAMILY(inp)) 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 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) { 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) { if(--request->retries <= 0) { (*request->query->callback) (request->query->ptr, 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(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) { irc_res_init(); timeout_resolver_ev = rb_event_add("timeout_resolver", timeout_resolver, NULL, 1); } /* * init_resolver - initialize resolver and resolver library */ void init_resolver(void) { start_resolver(); } /* * restart_resolver - reread resolv.conf, reopen socket */ void restart_resolver(void) { rb_event_delete(timeout_resolver_ev); /* -ddosen */ start_resolver(); } #if 0 /* * 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); } } } } #endif /* * 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); if(request->ipv4_F != NULL) rb_close(request->ipv4_F); #ifdef RB_IPV6 if(request->ipv6_F != NULL) rb_close(request->ipv6_F); #endif 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; 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. */ #if 0 static 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); } } } #endif #ifdef RES_MIN #undef RES_MIN #endif #define RES_MIN(a, b) ((a) < (b) ? (a) : (b)) static rb_fde_t * random_socket(int family) { rb_fde_t *F; int nport; int i; rb_socklen_t len; struct rb_sockaddr_storage sockaddr; F = rb_socket(family, SOCK_DGRAM, 0, "UDP resolver socket"); if(F == NULL) return NULL; memset(&sockaddr, 0, sizeof(sockaddr)); SET_SS_FAMILY(&sockaddr, family); #ifdef RB_IPV6 if(family == AF_INET6) { struct sockaddr_in6 *in6 = (struct sockaddr_in6 *)&sockaddr; memcpy(&in6->sin6_addr, &ipv6_addr, sizeof(struct in6_addr)); len = (rb_socklen_t) sizeof(struct sockaddr_in6); } else #endif { struct sockaddr_in *in = (struct sockaddr_in *)&sockaddr; in->sin_addr.s_addr = ipv4_addr.s_addr; len = (rb_socklen_t) sizeof(struct sockaddr_in); } for(i = 0; i < 10; i++) { nport = htons(generate_random_port()); if(family == AF_INET) ((struct sockaddr_in *)&sockaddr)->sin_port = nport; #ifdef RB_IPV6 else ((struct sockaddr_in6 *)&sockaddr)->sin6_port = nport; #endif if(bind(rb_get_fd(F), (struct sockaddr *)&sockaddr, len) == 0) return F; } rb_close(F); return NULL; } /* * 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(void *msg, int len, struct reslist *request) { int i; int sent = 0; rb_fde_t *F = NULL; int rcount = request->sends; int max_queries = RES_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; sent < max_queries && i < irc_nscount; i++) { if(GET_SS_FAMILY(&irc_nsaddr_list[i]) == AF_INET) { if(request->ipv4_F == NULL) { request->ipv4_F = random_socket(AF_INET); } F = request->ipv4_F; } #ifdef RB_IPV6 else { if(GET_SS_FAMILY(&irc_nsaddr_list[i]) == AF_INET6) { request->ipv6_F = random_socket(AF_INET6); } F = request->ipv6_F; } #endif if(F == NULL) continue; if(sendto(rb_get_fd(F), msg, len, 0, (struct sockaddr *)&(irc_nsaddr_list[i]), GET_SS_LEN(&irc_nsaddr_list[i])) == len) ++sent; rb_setselect(F, RB_SELECT_READ, res_readreply, NULL); } return (sent); } /* * find_id - find a dns request id (id is determined by dn_mkquery) */ static struct reslist * find_id(uint16_t 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); } static uint16_t generate_random_id(void) { uint16_t id; do { rb_get_pseudo_random(&id, sizeof(id)); if(id == 0xffff) continue; } while(find_id(id)); return id; } static int generate_random_port(void) { uint16_t port; while(1) { rb_get_pseudo_random(&port, sizeof(port)); if(port > 1024) break; } return (int)port; } /* * 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[HOSTLEN + 1]; rb_strlcpy(host_name, name, sizeof(host_name)); // add_local_domain(host_name, HOSTLEN); if(request == NULL) { request = make_request(query); request->name = rb_strdup(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(HOSTLEN + 1); } if(GET_SS_FAMILY(addr) == 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(GET_SS_FAMILY(addr) == AF_INET6) { const struct sockaddr_in6 *v6 = (const struct sockaddr_in6 *)addr; cp = (const unsigned char *)&v6->sin6_addr.s6_addr; rb_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) { void *buf = alloca(MAXPACKET); int request_len = 0; memset(buf, 0, MAXPACKET); if((request_len = irc_res_mkquery(request->queryname, C_IN, request->type, buf, MAXPACKET)) > 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 */ header->id = generate_random_id(); request->id = header->id; ++request->sends; request->sent += send_res_msg(buf, request_len, request); } } static void resend_query(struct reslist *request) { 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[128]; /* 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[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[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, 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) { int buflen = sizeof(HEADER) + MAXPACKET; void *buf = alloca(buflen); HEADER *header; struct reslist *request = NULL; struct DNSReply *reply = NULL; int rc; int answer_count; rb_socklen_t len = sizeof(struct rb_sockaddr_storage); struct rb_sockaddr_storage lsin; rc = recvfrom(rb_get_fd(F), buf, buflen, 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 */ if(!res_ourserver(&lsin)) return 1; if(!check_question(request, header, (char *)buf, ((char *)buf) + rc)) return 1; if((header->rcode != NO_ERRORS) || (header->ancount == 0)) { /* * If a bad error was returned, we stop here and dont send * send any more (no retries granted). */ (*request->query->callback) (request->query->ptr, NULL); rem_request(request); return -1; } /* * If this fails there was an error decoding the received packet, * give up. -- jilles */ answer_count = proc_answer(request, header, (char *)buf, ((char *)buf) + rc); if(answer_count) { 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->query->callback) (request->query->ptr, reply); rem_request(request); return -1; } /* * Lookup the 'authoritative' name that we were given for the * ip#. * */ #ifdef RB_IPV6 if(GET_SS_FAMILY(&request->addr) == 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); } } else { /* couldn't decode, give up -- jilles */ (*request->query->callback) (request->query->ptr, NULL); rem_request(request); } return -1; } static void res_readreply(rb_fde_t *F, void *data) { int rc; while((rc = res_read_single_reply(F, data)) > 0) ;; if(rc != -1) rb_setselect(F, RB_SELECT_READ, res_readreply, NULL); } static struct DNSReply * make_dnsreply(struct reslist *request) { struct DNSReply *cp; cp = (struct DNSReply *)rb_malloc(sizeof(struct DNSReply)); cp->h_name = request->name; memcpy(&cp->addr, &request->addr, sizeof(cp->addr)); return (cp); }