/* SPDX-License-Identifier: LGPL-2.1-or-later */ #include #include #include #include "fd-util.h" #include "fileio.h" #include "hostname-util.h" #include "resolved-dns-synthesize.h" #include "resolved-etc-hosts.h" #include "socket-netlink.h" #include "stat-util.h" #include "string-util.h" #include "strv.h" #include "time-util.h" /* Recheck /etc/hosts at most once every 2s */ #define ETC_HOSTS_RECHECK_USEC (2*USEC_PER_SEC) static void etc_hosts_item_free(EtcHostsItem *item) { strv_free(item->names); free(item); } static void etc_hosts_item_by_name_free(EtcHostsItemByName *item) { free(item->name); free(item->addresses); free(item); } void etc_hosts_free(EtcHosts *hosts) { hosts->by_address = hashmap_free_with_destructor(hosts->by_address, etc_hosts_item_free); hosts->by_name = hashmap_free_with_destructor(hosts->by_name, etc_hosts_item_by_name_free); hosts->no_address = set_free_free(hosts->no_address); } void manager_etc_hosts_flush(Manager *m) { etc_hosts_free(&m->etc_hosts); m->etc_hosts_stat = (struct stat) {}; } static int parse_line(EtcHosts *hosts, unsigned nr, const char *line) { _cleanup_free_ char *address_str = NULL; struct in_addr_data address = {}; bool found = false; EtcHostsItem *item; int r; assert(hosts); assert(line); r = extract_first_word(&line, &address_str, NULL, EXTRACT_RELAX); if (r < 0) return log_error_errno(r, "/etc/hosts:%u: failed to extract address: %m", nr); assert(r > 0); /* We already checked that the line is not empty, so it should contain *something* */ r = in_addr_ifindex_from_string_auto(address_str, &address.family, &address.address, NULL); if (r < 0) { log_warning_errno(r, "/etc/hosts:%u: address '%s' is invalid, ignoring: %m", nr, address_str); return 0; } r = in_addr_data_is_null(&address); if (r < 0) { log_warning_errno(r, "/etc/hosts:%u: address '%s' is invalid, ignoring: %m", nr, address_str); return 0; } if (r > 0) /* This is an 0.0.0.0 or :: item, which we assume means that we shall map the specified hostname to * nothing. */ item = NULL; else { /* If this is a normal address, then simply add entry mapping it to the specified names */ item = hashmap_get(hosts->by_address, &address); if (!item) { r = hashmap_ensure_allocated(&hosts->by_address, &in_addr_data_hash_ops); if (r < 0) return log_oom(); item = new(EtcHostsItem, 1); if (!item) return log_oom(); *item = (EtcHostsItem) { .address = address, }; r = hashmap_put(hosts->by_address, &item->address, item); if (r < 0) { free(item); return log_oom(); } } } for (;;) { _cleanup_free_ char *name = NULL; EtcHostsItemByName *bn; r = extract_first_word(&line, &name, NULL, EXTRACT_RELAX); if (r < 0) return log_error_errno(r, "/etc/hosts:%u: couldn't extract hostname: %m", nr); if (r == 0) break; found = true; r = dns_name_is_valid_ldh(name); if (r <= 0) { if (r < 0) log_warning_errno(r, "/etc/hosts:%u: Failed to check the validity of hostname \"%s\", ignoring: %m", nr, name); else log_warning("/etc/hosts:%u: hostname \"%s\" is not valid, ignoring.", nr, name); continue; } if (!item) { /* Optimize the case where we don't need to store any addresses, by storing * only the name in a dedicated Set instead of the hashmap */ r = set_ensure_consume(&hosts->no_address, &dns_name_hash_ops, TAKE_PTR(name)); if (r < 0) return r; continue; } r = strv_extend(&item->names, name); if (r < 0) return log_oom(); bn = hashmap_get(hosts->by_name, name); if (!bn) { r = hashmap_ensure_allocated(&hosts->by_name, &dns_name_hash_ops); if (r < 0) return log_oom(); bn = new0(EtcHostsItemByName, 1); if (!bn) return log_oom(); r = hashmap_put(hosts->by_name, name, bn); if (r < 0) { free(bn); return log_oom(); } bn->name = TAKE_PTR(name); } if (!GREEDY_REALLOC(bn->addresses, bn->n_addresses + 1)) return log_oom(); bn->addresses[bn->n_addresses++] = &item->address; } if (!found) log_warning("/etc/hosts:%u: line is missing any hostnames", nr); return 0; } static void strip_localhost(EtcHosts *hosts) { static const struct in_addr_data local_in_addrs[] = { { .family = AF_INET, #if __BYTE_ORDER == __LITTLE_ENDIAN /* We want constant expressions here, that's why we don't use htole32() here */ .address.in.s_addr = UINT32_C(0x0100007F), #else .address.in.s_addr = UINT32_C(0x7F000001), #endif }, { .family = AF_INET6, .address.in6 = IN6ADDR_LOOPBACK_INIT, }, }; EtcHostsItem *item; assert(hosts); /* Removes the 'localhost' entry from what we loaded. But only if the mapping is exclusively between * 127.0.0.1 and localhost (or aliases to that we recognize). If there's any other name assigned to * it, we leave the entry in. * * This way our regular synthesizing can take over, but only if it would result in the exact same * mappings. */ for (size_t j = 0; j < ELEMENTSOF(local_in_addrs); j++) { bool all_localhost, in_order; char **i; item = hashmap_get(hosts->by_address, local_in_addrs + j); if (!item) continue; /* Check whether all hostnames the loopback address points to are localhost ones */ all_localhost = true; STRV_FOREACH(i, item->names) if (!is_localhost(*i)) { all_localhost = false; break; } if (!all_localhost) /* Not all names are localhost, hence keep the entries for this address. */ continue; /* Now check if the names listed for this address actually all point back just to this * address (or the other loopback address). If not, let's stay away from this too. */ in_order = true; STRV_FOREACH(i, item->names) { EtcHostsItemByName *n; bool all_local_address; n = hashmap_get(hosts->by_name, *i); if (!n) /* No reverse entry? Then almost certainly the entry already got deleted from * the previous iteration of this loop, i.e. via the other protocol */ break; /* Now check if the addresses of this item are all localhost addresses */ all_local_address = true; for (size_t m = 0; m < n->n_addresses; m++) if (!in_addr_is_localhost(n->addresses[m]->family, &n->addresses[m]->address)) { all_local_address = false; break; } if (!all_local_address) { in_order = false; break; } } if (!in_order) continue; STRV_FOREACH(i, item->names) { EtcHostsItemByName *n; n = hashmap_remove(hosts->by_name, *i); if (n) etc_hosts_item_by_name_free(n); } assert_se(hashmap_remove(hosts->by_address, local_in_addrs + j) == item); etc_hosts_item_free(item); } } int etc_hosts_parse(EtcHosts *hosts, FILE *f) { _cleanup_(etc_hosts_free) EtcHosts t = {}; unsigned nr = 0; int r; for (;;) { _cleanup_free_ char *line = NULL; char *l; r = read_line(f, LONG_LINE_MAX, &line); if (r < 0) return log_error_errno(r, "Failed to read /etc/hosts: %m"); if (r == 0) break; nr++; l = strchr(line, '#'); if (l) *l = '\0'; l = strstrip(line); if (isempty(l)) continue; r = parse_line(&t, nr, l); if (r < 0) return r; } strip_localhost(&t); etc_hosts_free(hosts); *hosts = t; t = (EtcHosts) {}; /* prevent cleanup */ return 0; } static int manager_etc_hosts_read(Manager *m) { _cleanup_fclose_ FILE *f = NULL; struct stat st; usec_t ts; int r; assert_se(sd_event_now(m->event, clock_boottime_or_monotonic(), &ts) >= 0); /* See if we checked /etc/hosts recently already */ if (m->etc_hosts_last != USEC_INFINITY && m->etc_hosts_last + ETC_HOSTS_RECHECK_USEC > ts) return 0; m->etc_hosts_last = ts; if (m->etc_hosts_stat.st_mode != 0) { if (stat("/etc/hosts", &st) < 0) { if (errno != ENOENT) return log_error_errno(errno, "Failed to stat /etc/hosts: %m"); manager_etc_hosts_flush(m); return 0; } /* Did the mtime or ino/dev change? If not, there's no point in re-reading the file. */ if (stat_inode_unmodified(&m->etc_hosts_stat, &st)) return 0; } f = fopen("/etc/hosts", "re"); if (!f) { if (errno != ENOENT) return log_error_errno(errno, "Failed to open /etc/hosts: %m"); manager_etc_hosts_flush(m); return 0; } /* Take the timestamp at the beginning of processing, so that any changes made later are read on the next * invocation */ r = fstat(fileno(f), &st); if (r < 0) return log_error_errno(errno, "Failed to fstat() /etc/hosts: %m"); r = etc_hosts_parse(&m->etc_hosts, f); if (r < 0) return r; m->etc_hosts_stat = st; m->etc_hosts_last = ts; return 1; } int manager_etc_hosts_lookup(Manager *m, DnsQuestion* q, DnsAnswer **answer) { bool found_a = false, found_aaaa = false; struct in_addr_data k = {}; EtcHostsItemByName *bn; DnsResourceKey *t; const char *name; unsigned i; int r; assert(m); assert(q); assert(answer); if (!m->read_etc_hosts) return 0; (void) manager_etc_hosts_read(m); name = dns_question_first_name(q); if (!name) return 0; r = dns_name_address(name, &k.family, &k.address); if (r > 0) { EtcHostsItem *item; DnsResourceKey *found_ptr = NULL; item = hashmap_get(m->etc_hosts.by_address, &k); if (!item) return 0; /* We have an address in /etc/hosts that matches the queried name. Let's return successful. Actual data * we'll only return if the request was for PTR. */ DNS_QUESTION_FOREACH(t, q) { if (!IN_SET(t->type, DNS_TYPE_PTR, DNS_TYPE_ANY)) continue; if (!IN_SET(t->class, DNS_CLASS_IN, DNS_CLASS_ANY)) continue; r = dns_name_equal(dns_resource_key_name(t), name); if (r < 0) return r; if (r > 0) { found_ptr = t; break; } } if (found_ptr) { char **n; r = dns_answer_reserve(answer, strv_length(item->names)); if (r < 0) return r; STRV_FOREACH(n, item->names) { _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL; rr = dns_resource_record_new(found_ptr); if (!rr) return -ENOMEM; rr->ptr.name = strdup(*n); if (!rr->ptr.name) return -ENOMEM; r = dns_answer_add(*answer, rr, 0, DNS_ANSWER_AUTHENTICATED, NULL); if (r < 0) return r; } } return 1; } bn = hashmap_get(m->etc_hosts.by_name, name); if (bn) { r = dns_answer_reserve(answer, bn->n_addresses); if (r < 0) return r; } else { /* Check if name was listed with no address. If yes, continue to return an answer. */ if (!set_contains(m->etc_hosts.no_address, name)) return 0; } DNS_QUESTION_FOREACH(t, q) { if (!IN_SET(t->type, DNS_TYPE_A, DNS_TYPE_AAAA, DNS_TYPE_ANY)) continue; if (!IN_SET(t->class, DNS_CLASS_IN, DNS_CLASS_ANY)) continue; r = dns_name_equal(dns_resource_key_name(t), name); if (r < 0) return r; if (r == 0) continue; if (IN_SET(t->type, DNS_TYPE_A, DNS_TYPE_ANY)) found_a = true; if (IN_SET(t->type, DNS_TYPE_AAAA, DNS_TYPE_ANY)) found_aaaa = true; if (found_a && found_aaaa) break; } for (i = 0; bn && i < bn->n_addresses; i++) { _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL; if ((!found_a && bn->addresses[i]->family == AF_INET) || (!found_aaaa && bn->addresses[i]->family == AF_INET6)) continue; r = dns_resource_record_new_address(&rr, bn->addresses[i]->family, &bn->addresses[i]->address, bn->name); if (r < 0) return r; r = dns_answer_add(*answer, rr, 0, DNS_ANSWER_AUTHENTICATED, NULL); if (r < 0) return r; } return found_a || found_aaaa; }