From b750101eb236130cf056c675997decbac904cc49 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 17:35:18 +0200 Subject: Adding upstream version 252.22. Signed-off-by: Daniel Baumann --- src/resolve/resolved-etc-hosts.c | 467 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 467 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..8a58db4 --- /dev/null +++ b/src/resolve/resolved-etc-hosts.c @@ -0,0 +1,467 @@ +/* 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_with_size(&item->names, &item->n_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; + + 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, &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) { + r = dns_answer_reserve(answer, item->n_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; +} -- cgit v1.2.3