/* 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 EtcHostsItemByAddress *etc_hosts_item_by_address_free(EtcHostsItemByAddress *item) { if (!item) return NULL; set_free(item->names); return mfree(item); } DEFINE_TRIVIAL_CLEANUP_FUNC(EtcHostsItemByAddress*, etc_hosts_item_by_address_free); DEFINE_PRIVATE_HASH_OPS_WITH_VALUE_DESTRUCTOR( by_address_hash_ops, struct in_addr_data, in_addr_data_hash_func, in_addr_data_compare_func, EtcHostsItemByAddress, etc_hosts_item_by_address_free); static EtcHostsItemByName *etc_hosts_item_by_name_free(EtcHostsItemByName *item) { if (!item) return NULL; free(item->name); set_free(item->addresses); return mfree(item); } DEFINE_TRIVIAL_CLEANUP_FUNC(EtcHostsItemByName*, etc_hosts_item_by_name_free); DEFINE_PRIVATE_HASH_OPS_WITH_VALUE_DESTRUCTOR( by_name_hash_ops, char, dns_name_hash_func, dns_name_compare_func, EtcHostsItemByName, etc_hosts_item_by_name_free); void etc_hosts_clear(EtcHosts *hosts) { assert(hosts); hosts->by_address = hashmap_free(hosts->by_address); hosts->by_name = hashmap_free(hosts->by_name); hosts->no_address = set_free(hosts->no_address); } void manager_etc_hosts_flush(Manager *m) { etc_hosts_clear(&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; EtcHostsItemByAddress *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) { _cleanup_(etc_hosts_item_by_address_freep) EtcHostsItemByAddress *new_item = NULL; new_item = new(EtcHostsItemByAddress, 1); if (!new_item) return log_oom(); *new_item = (EtcHostsItemByAddress) { .address = address, }; r = hashmap_ensure_put(&hosts->by_address, &by_address_hash_ops, &new_item->address, new_item); if (r < 0) return log_oom(); item = TAKE_PTR(new_item); } } 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; 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; } found = true; 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_free, TAKE_PTR(name)); if (r < 0) return log_oom(); continue; } bn = hashmap_get(hosts->by_name, name); if (!bn) { _cleanup_(etc_hosts_item_by_name_freep) EtcHostsItemByName *new_item = NULL; _cleanup_free_ char *name_copy = NULL; name_copy = strdup(name); if (!name_copy) return log_oom(); new_item = new(EtcHostsItemByName, 1); if (!new_item) return log_oom(); *new_item = (EtcHostsItemByName) { .name = TAKE_PTR(name_copy), }; r = hashmap_ensure_put(&hosts->by_name, &by_name_hash_ops, new_item->name, new_item); if (r < 0) return log_oom(); bn = TAKE_PTR(new_item); } if (!set_contains(bn->addresses, &address)) { _cleanup_free_ struct in_addr_data *address_copy = NULL; address_copy = newdup(struct in_addr_data, &address, 1); if (!address_copy) return log_oom(); r = set_ensure_consume(&bn->addresses, &in_addr_data_hash_ops_free, TAKE_PTR(address_copy)); if (r < 0) return log_oom(); } r = set_ensure_put(&item->names, &dns_name_hash_ops_free, name); if (r < 0) return log_oom(); if (r == 0) /* the name is already listed */ continue; /* * Keep track of the first name listed for this address. * This name will be used in responses as the canonical name. */ if (!item->canonical_name) item->canonical_name = name; TAKE_PTR(name); } if (!found) log_warning("/etc/hosts:%u: line is missing any valid 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, }, }; 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. */ FOREACH_ELEMENT(local_in_addr, local_in_addrs) { bool all_localhost, all_local_address; EtcHostsItemByAddress *item; const char *name; item = hashmap_get(hosts->by_address, local_in_addr); if (!item) continue; /* Check whether all hostnames the loopback address points to are localhost ones */ all_localhost = true; SET_FOREACH(name, item->names) if (!is_localhost(name)) { 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. */ all_local_address = true; SET_FOREACH(name, item->names) { EtcHostsItemByName *n; struct in_addr_data *a; n = hashmap_get(hosts->by_name, name); 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 */ SET_FOREACH(a, n->addresses) if (!in_addr_is_localhost(a->family, &a->address)) { all_local_address = false; break; } if (!all_local_address) break; } if (!all_local_address) continue; SET_FOREACH(name, item->names) etc_hosts_item_by_name_free(hashmap_remove(hosts->by_name, name)); assert_se(hashmap_remove(hosts->by_address, local_in_addr) == item); etc_hosts_item_by_address_free(item); } } int etc_hosts_parse(EtcHosts *hosts, FILE *f) { _cleanup_(etc_hosts_clear) EtcHosts t = {}; unsigned nr = 0; int r; assert(hosts); 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_clear(hosts); *hosts = TAKE_STRUCT(t); 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, &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 (stat_is_set(&m->etc_hosts_stat)) { 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; } static int answer_add_ptr(DnsAnswer *answer, DnsResourceKey *key, const char *name) { _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL; rr = dns_resource_record_new(key); if (!rr) return -ENOMEM; rr->ptr.name = strdup(name); if (!rr->ptr.name) return -ENOMEM; return dns_answer_add(answer, rr, 0, DNS_ANSWER_AUTHENTICATED, NULL); } static int answer_add_cname(DnsAnswer *answer, const char *name, const char *cname) { _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL; rr = dns_resource_record_new_full(DNS_CLASS_IN, DNS_TYPE_CNAME, name); if (!rr) return -ENOMEM; rr->cname.name = strdup(cname); if (!rr->cname.name) return -ENOMEM; return dns_answer_add(answer, rr, 0, DNS_ANSWER_AUTHENTICATED, NULL); } static int answer_add_addr(DnsAnswer *answer, const char *name, const struct in_addr_data *a) { _cleanup_(dns_resource_record_unrefp) DnsResourceRecord *rr = NULL; int r; r = dns_resource_record_new_address(&rr, a->family, &a->address, name); if (r < 0) return r; return dns_answer_add(answer, rr, 0, DNS_ANSWER_AUTHENTICATED, NULL); } static int etc_hosts_lookup_by_address( EtcHosts *hosts, DnsQuestion *q, const char *name, const struct in_addr_data *address, DnsAnswer **answer) { DnsResourceKey *t, *found_ptr = NULL; EtcHostsItemByAddress *item; int r; assert(hosts); assert(q); assert(name); assert(address); assert(answer); item = hashmap_get(hosts->by_address, address); 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) { const char *n; r = dns_answer_reserve(answer, set_size(item->names)); if (r < 0) return r; if (item->canonical_name) { r = answer_add_ptr(*answer, found_ptr, item->canonical_name); if (r < 0) return r; } SET_FOREACH(n, item->names) { if (n == item->canonical_name) continue; r = answer_add_ptr(*answer, found_ptr, n); if (r < 0) return r; } } return 1; } static int etc_hosts_lookup_by_name( EtcHosts *hosts, DnsQuestion *q, const char *name, DnsAnswer **answer) { bool question_for_a = false, question_for_aaaa = false; const struct in_addr_data *a; EtcHostsItemByName *item; DnsResourceKey *t; int r; assert(hosts); assert(q); assert(name); assert(answer); item = hashmap_get(hosts->by_name, name); if (item) { r = dns_answer_reserve(answer, set_size(item->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(hosts->no_address, name)) return 0; } /* Determine whether we are looking for A and/or AAAA RRs */ 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)) question_for_a = true; if (IN_SET(t->type, DNS_TYPE_AAAA, DNS_TYPE_ANY)) question_for_aaaa = true; if (question_for_a && question_for_aaaa) break; /* We are looking for both, no need to continue loop */ } SET_FOREACH(a, item ? item->addresses : NULL) { EtcHostsItemByAddress *item_by_addr; const char *canonical_name; if ((!question_for_a && a->family == AF_INET) || (!question_for_aaaa && a->family == AF_INET6)) continue; item_by_addr = hashmap_get(hosts->by_address, a); if (item_by_addr && item_by_addr->canonical_name) canonical_name = item_by_addr->canonical_name; else canonical_name = item->name; if (!streq(item->name, canonical_name)) { r = answer_add_cname(*answer, item->name, canonical_name); if (r < 0) return r; } r = answer_add_addr(*answer, canonical_name, a); if (r < 0) return r; } return true; /* We consider ourselves authoritative for the whole name, all RR types, not just A/AAAA */ } int manager_etc_hosts_lookup(Manager *m, DnsQuestion *q, DnsAnswer **answer) { struct in_addr_data k; const char *name; 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; if (dns_name_address(name, &k.family, &k.address) > 0) return etc_hosts_lookup_by_address(&m->etc_hosts, q, name, &k, answer); return etc_hosts_lookup_by_name(&m->etc_hosts, q, name, answer); }