From 55944e5e40b1be2afc4855d8d2baf4b73d1876b5 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Wed, 10 Apr 2024 22:49:52 +0200 Subject: Adding upstream version 255.4. Signed-off-by: Daniel Baumann --- src/resolve/resolved-etc-hosts.c | 586 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 586 insertions(+) create mode 100644 src/resolve/resolved-etc-hosts.c (limited to 'src/resolve/resolved-etc-hosts.c') diff --git a/src/resolve/resolved-etc-hosts.c b/src/resolve/resolved-etc-hosts.c new file mode 100644 index 0000000..6af160a --- /dev/null +++ b/src/resolve/resolved-etc-hosts.c @@ -0,0 +1,586 @@ +/* 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. */ + + for (size_t j = 0; j < ELEMENTSOF(local_in_addrs); j++) { + bool all_localhost, all_local_address; + EtcHostsItemByAddress *item; + const char *name; + + 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; + 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_addrs + j) == 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 (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; +} + +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 found_a = false, found_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; + } + + 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; + } + + SET_FOREACH(a, item ? item->addresses : NULL) { + EtcHostsItemByAddress *item_by_addr; + const char *canonical_name; + + if ((!found_a && a->family == AF_INET) || + (!found_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 found_a || found_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); +} -- cgit v1.2.3