Adding upstream version 255.4.upstream/255.4

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 434 insertions, 0 deletions

diff --git a/src/resolve/resolved-resolv-conf.c b/src/resolve/resolved-resolv-conf.c
new file mode 100644
index 0000000..2071e08
--- /dev/null
+++ b/src/resolve/resolved-resolv-conf.c
@@ -0,0 +1,434 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <resolv.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "alloc-util.h"
+#include "dns-domain.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "fs-util.h"
+#include "label-util.h"
+#include "ordered-set.h"
+#include "path-util.h"
+#include "resolved-conf.h"
+#include "resolved-dns-server.h"
+#include "resolved-resolv-conf.h"
+#include "stat-util.h"
+#include "string-table.h"
+#include "string-util.h"
+#include "strv.h"
+#include "tmpfile-util-label.h"
+
+int manager_check_resolv_conf(const Manager *m) {
+        struct stat st, own;
+
+        assert(m);
+
+        /* This warns only when our stub listener is disabled and /etc/resolv.conf is a symlink to
+         * PRIVATE_STATIC_RESOLV_CONF. */
+
+        if (m->dns_stub_listener_mode != DNS_STUB_LISTENER_NO)
+                return 0;
+
+        if (stat("/etc/resolv.conf", &st) < 0) {
+                if (errno == ENOENT)
+                        return 0;
+
+                return log_warning_errno(errno, "Failed to stat /etc/resolv.conf: %m");
+        }
+
+        /* Is it symlinked to our own uplink file? */
+        if (stat(PRIVATE_STATIC_RESOLV_CONF, &own) >= 0 &&
+            stat_inode_same(&st, &own))
+                return log_warning_errno(SYNTHETIC_ERRNO(EOPNOTSUPP),
+                                         "DNSStubListener= is disabled, but /etc/resolv.conf is a symlink to "
+                                         PRIVATE_STATIC_RESOLV_CONF " which expects DNSStubListener= to be enabled.");
+
+        return 0;
+}
+
+static bool file_is_our_own(const struct stat *st) {
+        assert(st);
+
+        FOREACH_STRING(path,
+                       PRIVATE_UPLINK_RESOLV_CONF,
+                       PRIVATE_STUB_RESOLV_CONF,
+                       PRIVATE_STATIC_RESOLV_CONF) {
+
+                struct stat own;
+
+                /* Is it symlinked to our own uplink file? */
+                if (stat(path, &own) >= 0 &&
+                    stat_inode_same(st, &own))
+                        return true;
+        }
+
+        return false;
+}
+
+int manager_read_resolv_conf(Manager *m) {
+        _cleanup_fclose_ FILE *f = NULL;
+        struct stat st;
+        unsigned n = 0;
+        int r;
+
+        assert(m);
+
+        /* Reads the system /etc/resolv.conf, if it exists and is not
+         * symlinked to our own resolv.conf instance */
+
+        if (!m->read_resolv_conf)
+                return 0;
+
+        r = stat("/etc/resolv.conf", &st);
+        if (r < 0) {
+                if (errno == ENOENT)
+                        return 0;
+
+                r = log_warning_errno(errno, "Failed to stat /etc/resolv.conf: %m");
+                goto clear;
+        }
+
+        /* Have we already seen the file? */
+        if (stat_inode_unmodified(&st, &m->resolv_conf_stat))
+                return 0;
+
+        if (file_is_our_own(&st))
+                return 0;
+
+        f = fopen("/etc/resolv.conf", "re");
+        if (!f) {
+                if (errno == ENOENT)
+                        return 0;
+
+                r = log_warning_errno(errno, "Failed to open /etc/resolv.conf: %m");
+                goto clear;
+        }
+
+        if (fstat(fileno(f), &st) < 0) {
+                r = log_error_errno(errno, "Failed to stat open file: %m");
+                goto clear;
+        }
+
+        if (file_is_our_own(&st))
+                return 0;
+
+        dns_server_mark_all(m->dns_servers);
+        dns_search_domain_mark_all(m->search_domains);
+
+        for (;;) {
+                _cleanup_free_ char *line = NULL;
+                const char *a;
+
+                r = read_stripped_line(f, LONG_LINE_MAX, &line);
+                if (r < 0) {
+                        log_error_errno(r, "Failed to read /etc/resolv.conf: %m");
+                        goto clear;
+                }
+                if (r == 0)
+                        break;
+
+                n++;
+
+                if (IN_SET(*line, '#', ';', 0))
+                        continue;
+
+                a = first_word(line, "nameserver");
+                if (a) {
+                        r = manager_parse_dns_server_string_and_warn(m, DNS_SERVER_SYSTEM, a);
+                        if (r < 0)
+                                log_warning_errno(r, "Failed to parse DNS server address '%s', ignoring.", a);
+
+                        continue;
+                }
+
+                a = first_word(line, "domain");
+                if (!a) /* We treat "domain" lines, and "search" lines as equivalent, and add both to our list. */
+                        a = first_word(line, "search");
+                if (a) {
+                        r = manager_parse_search_domains_and_warn(m, a);
+                        if (r < 0)
+                                log_warning_errno(r, "Failed to parse search domain string '%s', ignoring.", a);
+
+                        continue;
+                }
+
+                log_syntax(NULL, LOG_DEBUG, "/etc/resolv.conf", n, 0, "Ignoring resolv.conf line: %s", line);
+        }
+
+        m->resolv_conf_stat = st;
+
+        /* Flush out all servers and search domains that are still
+         * marked. Those are then ones that didn't appear in the new
+         * /etc/resolv.conf */
+        dns_server_unlink_marked(m->dns_servers);
+        dns_search_domain_unlink_marked(m->search_domains);
+
+        /* Whenever /etc/resolv.conf changes, start using the first
+         * DNS server of it. This is useful to deal with broken
+         * network managing implementations (like NetworkManager),
+         * that when connecting to a VPN place both the VPN DNS
+         * servers and the local ones in /etc/resolv.conf. Without
+         * resetting the DNS server to use back to the first entry we
+         * will continue to use the local one thus being unable to
+         * resolve VPN domains. */
+        manager_set_dns_server(m, m->dns_servers);
+
+        /* Unconditionally flush the cache when /etc/resolv.conf is
+         * modified, even if the data it contained was completely
+         * identical to the previous version we used. We do this
+         * because altering /etc/resolv.conf is typically done when
+         * the network configuration changes, and that should be
+         * enough to flush the global unicast DNS cache. */
+        if (m->unicast_scope)
+                dns_cache_flush(&m->unicast_scope->cache);
+
+        /* If /etc/resolv.conf changed, make sure to forget everything we learned about the DNS servers. After all we
+         * might now talk to a very different DNS server that just happens to have the same IP address as an old one
+         * (think 192.168.1.1). */
+        dns_server_reset_features_all(m->dns_servers);
+
+        return 0;
+
+clear:
+        dns_server_unlink_all(m->dns_servers);
+        dns_search_domain_unlink_all(m->search_domains);
+        return r;
+}
+
+static void write_resolv_conf_server(DnsServer *s, FILE *f, unsigned *count) {
+        DnsScope *scope;
+
+        assert(s);
+        assert(f);
+        assert(count);
+
+        if (!dns_server_string(s)) {
+                log_warning("Out of memory, or invalid DNS address. Ignoring server.");
+                return;
+        }
+
+        /* resolv.conf simply doesn't support any other ports than 53, hence there's nothing much we can
+         * do — we have to suppress these entries */
+        if (dns_server_port(s) != 53) {
+                log_debug("DNS server %s with non-standard UDP port number, suppressing from generated resolv.conf.", dns_server_string(s));
+                return;
+        }
+
+        /* Check if the scope this DNS server belongs to is suitable as 'default' route for lookups; resolv.conf does
+         * not have a syntax to express that, so it must not appear as a global name server to avoid routing unrelated
+         * domains to it (which is a privacy violation, will most probably fail anyway, and adds unnecessary load) */
+        scope = dns_server_scope(s);
+        if (scope && !dns_scope_is_default_route(scope)) {
+                log_debug("Scope of DNS server %s has only route-only domains, not using as global name server", dns_server_string(s));
+                return;
+        }
+
+        if (*count == MAXNS)
+                fputs("# Too many DNS servers configured, the following entries may be ignored.\n", f);
+        (*count)++;
+
+        fprintf(f, "nameserver %s\n", dns_server_string(s));
+}
+
+static void write_resolv_conf_search(
+                OrderedSet *domains,
+                FILE *f) {
+        char *domain;
+
+        assert(domains);
+        assert(f);
+
+        fputs("search", f);
+
+        ORDERED_SET_FOREACH(domain, domains) {
+                fputc(' ', f);
+                fputs(domain, f);
+        }
+
+        fputs("\n", f);
+}
+
+static int write_uplink_resolv_conf_contents(FILE *f, OrderedSet *dns, OrderedSet *domains) {
+
+        fputs("# This is "PRIVATE_UPLINK_RESOLV_CONF" managed by man:systemd-resolved(8).\n"
+              "# Do not edit.\n"
+              "#\n"
+              "# This file might be symlinked as /etc/resolv.conf. If you're looking at\n"
+              "# /etc/resolv.conf and seeing this text, you have followed the symlink.\n"
+              "#\n"
+              "# This is a dynamic resolv.conf file for connecting local clients directly to\n"
+              "# all known uplink DNS servers. This file lists all configured search domains.\n"
+              "#\n"
+              "# Third party programs should typically not access this file directly, but only\n"
+              "# through the symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a\n"
+              "# different way, replace this symlink by a static file or a different symlink.\n"
+              "#\n"
+              "# See man:systemd-resolved.service(8) for details about the supported modes of\n"
+              "# operation for /etc/resolv.conf.\n"
+              "\n", f);
+
+        if (ordered_set_isempty(dns))
+                fputs("# No DNS servers known.\n", f);
+        else {
+                unsigned count = 0;
+                DnsServer *s;
+
+                ORDERED_SET_FOREACH(s, dns)
+                        write_resolv_conf_server(s, f, &count);
+        }
+
+        if (ordered_set_isempty(domains))
+                fputs("search .\n", f); /* Make sure that if the local hostname is chosen as fqdn this does not
+                                         * imply a search domain */
+        else
+                write_resolv_conf_search(domains, f);
+
+        return fflush_and_check(f);
+}
+
+static int write_stub_resolv_conf_contents(FILE *f, OrderedSet *dns, OrderedSet *domains) {
+        fputs("# This is "PRIVATE_STUB_RESOLV_CONF" managed by man:systemd-resolved(8).\n"
+              "# Do not edit.\n"
+              "#\n"
+              "# This file might be symlinked as /etc/resolv.conf. If you're looking at\n"
+              "# /etc/resolv.conf and seeing this text, you have followed the symlink.\n"
+              "#\n"
+              "# This is a dynamic resolv.conf file for connecting local clients to the\n"
+              "# internal DNS stub resolver of systemd-resolved. This file lists all\n"
+              "# configured search domains.\n"
+              "#\n"
+              "# Run \"resolvectl status\" to see details about the uplink DNS servers\n"
+              "# currently in use.\n"
+              "#\n"
+              "# Third party programs should typically not access this file directly, but only\n"
+              "# through the symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a\n"
+              "# different way, replace this symlink by a static file or a different symlink.\n"
+              "#\n"
+              "# See man:systemd-resolved.service(8) for details about the supported modes of\n"
+              "# operation for /etc/resolv.conf.\n"
+              "\n"
+              "nameserver 127.0.0.53\n"
+              "options edns0 trust-ad\n", f);
+
+        if (ordered_set_isempty(domains))
+                fputs("search .\n", f); /* Make sure that if the local hostname is chosen as fqdn this does not
+                                         * imply a search domain */
+        else
+                write_resolv_conf_search(domains, f);
+
+        return fflush_and_check(f);
+}
+
+int manager_write_resolv_conf(Manager *m) {
+        _cleanup_ordered_set_free_ OrderedSet *dns = NULL, *domains = NULL;
+        _cleanup_(unlink_and_freep) char *temp_path_uplink = NULL, *temp_path_stub = NULL;
+        _cleanup_fclose_ FILE *f_uplink = NULL, *f_stub = NULL;
+        int r;
+
+        assert(m);
+
+        /* Read the system /etc/resolv.conf first */
+        (void) manager_read_resolv_conf(m);
+
+        /* Add the full list to a set, to filter out duplicates */
+        r = manager_compile_dns_servers(m, &dns);
+        if (r < 0)
+                return log_warning_errno(r, "Failed to compile list of DNS servers, ignoring: %m");
+
+        r = manager_compile_search_domains(m, &domains, false);
+        if (r < 0)
+                return log_warning_errno(r, "Failed to compile list of search domains, ignoring: %m");
+
+        r = fopen_temporary_label(PRIVATE_UPLINK_RESOLV_CONF, PRIVATE_UPLINK_RESOLV_CONF, &f_uplink, &temp_path_uplink);
+        if (r < 0)
+                return log_warning_errno(r, "Failed to open new %s for writing, ignoring: %m", PRIVATE_UPLINK_RESOLV_CONF);
+
+        (void) fchmod(fileno(f_uplink), 0644);
+
+        r = write_uplink_resolv_conf_contents(f_uplink, dns, domains);
+        if (r < 0)
+                return log_warning_errno(r, "Failed to write new %s, ignoring: %m", PRIVATE_UPLINK_RESOLV_CONF);
+
+        if (m->dns_stub_listener_mode != DNS_STUB_LISTENER_NO) {
+                r = fopen_temporary_label(PRIVATE_STUB_RESOLV_CONF, PRIVATE_STUB_RESOLV_CONF, &f_stub, &temp_path_stub);
+                if (r < 0)
+                        return log_warning_errno(r, "Failed to open new %s for writing, ignoring: %m", PRIVATE_STUB_RESOLV_CONF);
+
+                (void) fchmod(fileno(f_stub), 0644);
+
+                r = write_stub_resolv_conf_contents(f_stub, dns, domains);
+                if (r < 0)
+                        return log_warning_errno(r, "Failed to write new %s, ignoring: %m", PRIVATE_STUB_RESOLV_CONF);
+
+                r = conservative_rename(temp_path_stub, PRIVATE_STUB_RESOLV_CONF);
+                if (r < 0)
+                        log_warning_errno(r, "Failed to move new %s into place, ignoring: %m", PRIVATE_STUB_RESOLV_CONF);
+
+                temp_path_stub = mfree(temp_path_stub); /* free the string explicitly, so that we don't unlink anymore */
+        } else {
+                _cleanup_free_ char *fname = NULL;
+                r = path_extract_filename(PRIVATE_UPLINK_RESOLV_CONF, &fname);
+                if (r < 0)
+                        return log_warning_errno(r, "Failed to extract filename from path '" PRIVATE_UPLINK_RESOLV_CONF "', ignoring: %m");
+
+                r = symlink_atomic_label(fname, PRIVATE_STUB_RESOLV_CONF);
+                if (r < 0)
+                        log_warning_errno(r, "Failed to symlink %s, ignoring: %m", PRIVATE_STUB_RESOLV_CONF);
+        }
+
+        r = conservative_rename(temp_path_uplink, PRIVATE_UPLINK_RESOLV_CONF);
+        if (r < 0)
+                log_warning_errno(r, "Failed to move new %s into place: %m", PRIVATE_UPLINK_RESOLV_CONF);
+
+        temp_path_uplink = mfree(temp_path_uplink); /* free the string explicitly, so that we don't unlink anymore */
+        return r;
+}
+
+int resolv_conf_mode(void) {
+        static const char * const table[_RESOLV_CONF_MODE_MAX] = {
+                [RESOLV_CONF_UPLINK] = PRIVATE_UPLINK_RESOLV_CONF,
+                [RESOLV_CONF_STUB] = PRIVATE_STUB_RESOLV_CONF,
+                [RESOLV_CONF_STATIC] = PRIVATE_STATIC_RESOLV_CONF,
+        };
+
+        struct stat system_st;
+
+        if (stat("/etc/resolv.conf", &system_st) < 0) {
+                if (errno == ENOENT)
+                        return RESOLV_CONF_MISSING;
+
+                return -errno;
+        }
+
+        for (ResolvConfMode m = 0; m < _RESOLV_CONF_MODE_MAX; m++) {
+                struct stat our_st;
+
+                if (!table[m])
+                        continue;
+
+                if (stat(table[m], &our_st) < 0) {
+                        if (errno != ENOENT)
+                                log_debug_errno(errno, "Failed to stat() %s, ignoring: %m", table[m]);
+
+                        continue;
+                }
+
+                if (stat_inode_same(&system_st, &our_st))
+                        return m;
+        }
+
+        return RESOLV_CONF_FOREIGN;
+}
+
+static const char* const resolv_conf_mode_table[_RESOLV_CONF_MODE_MAX] = {
+        [RESOLV_CONF_UPLINK] = "uplink",
+        [RESOLV_CONF_STUB] = "stub",
+        [RESOLV_CONF_STATIC] = "static",
+        [RESOLV_CONF_MISSING] = "missing",
+        [RESOLV_CONF_FOREIGN] = "foreign",
+};
+DEFINE_STRING_TABLE_LOOKUP(resolv_conf_mode, ResolvConfMode);