resolved: implement LLMNR uniqueness verification

1 files changed, 538 insertions, 0 deletions

diff --git a/src/resolve/resolved-dns-transaction.c b/src/resolve/resolved-dns-transaction.c
new file mode 100644
index 0000000000..92f7e4c5b1
--- /dev/null
+++ b/src/resolve/resolved-dns-transaction.c
@@ -0,0 +1,538 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2014 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include "af-list.h"
+
+#include "resolved-dns-transaction.h"
+
+DnsTransaction* dns_transaction_free(DnsTransaction *t) {
+        DnsQuery *q;
+        DnsZoneItem *i;
+
+        if (!t)
+                return NULL;
+
+        sd_event_source_unref(t->timeout_event_source);
+
+        dns_question_unref(t->question);
+        dns_packet_unref(t->sent);
+        dns_packet_unref(t->received);
+        dns_answer_unref(t->cached);
+
+        dns_stream_free(t->stream);
+
+        if (t->scope) {
+                LIST_REMOVE(transactions_by_scope, t->scope->transactions, t);
+
+                if (t->id != 0)
+                        hashmap_remove(t->scope->manager->dns_transactions, UINT_TO_PTR(t->id));
+        }
+
+        while ((q = set_steal_first(t->queries)))
+                set_remove(q->transactions, t);
+        set_free(t->queries);
+
+        while ((i = set_steal_first(t->zone_items)))
+                i->probe_transaction = NULL;
+        set_free(t->zone_items);
+
+        free(t);
+        return NULL;
+}
+
+DEFINE_TRIVIAL_CLEANUP_FUNC(DnsTransaction*, dns_transaction_free);
+
+void dns_transaction_gc(DnsTransaction *t) {
+        assert(t);
+
+        if (t->block_gc > 0)
+                return;
+
+        if (set_isempty(t->queries) && set_isempty(t->zone_items))
+                dns_transaction_free(t);
+}
+
+int dns_transaction_new(DnsTransaction **ret, DnsScope *s, DnsQuestion *q) {
+        _cleanup_(dns_transaction_freep) DnsTransaction *t = NULL;
+        int r;
+
+        assert(ret);
+        assert(s);
+        assert(q);
+
+        r = hashmap_ensure_allocated(&s->manager->dns_transactions, NULL, NULL);
+        if (r < 0)
+                return r;
+
+        t = new0(DnsTransaction, 1);
+        if (!t)
+                return -ENOMEM;
+
+        t->question = dns_question_ref(q);
+
+        do
+                random_bytes(&t->id, sizeof(t->id));
+        while (t->id == 0 ||
+               hashmap_get(s->manager->dns_transactions, UINT_TO_PTR(t->id)));
+
+        r = hashmap_put(s->manager->dns_transactions, UINT_TO_PTR(t->id), t);
+        if (r < 0) {
+                t->id = 0;
+                return r;
+        }
+
+        LIST_PREPEND(transactions_by_scope, s->transactions, t);
+        t->scope = s;
+
+        if (ret)
+                *ret = t;
+
+        t = NULL;
+
+        return 0;
+}
+
+static void dns_transaction_stop(DnsTransaction *t) {
+        assert(t);
+
+        t->timeout_event_source = sd_event_source_unref(t->timeout_event_source);
+        t->stream = dns_stream_free(t->stream);
+}
+
+static void dns_transaction_tentative(DnsTransaction *t, DnsPacket *p) {
+        DnsZoneItem *z;
+        Iterator i;
+
+        assert(t);
+        assert(p);
+
+        if (manager_our_packet(t->scope->manager, p) != 0)
+                return;
+
+        log_debug("Transaction on scope %s on %s/%s got tentative packet",
+                  dns_protocol_to_string(t->scope->protocol),
+                  t->scope->link ? t->scope->link->name : "*",
+                  t->scope->family == AF_UNSPEC ? "*" : af_to_name(t->scope->family));
+
+        t->block_gc++;
+        SET_FOREACH(z, t->zone_items, i)
+                dns_zone_item_conflict(z);
+        t->block_gc--;
+
+        dns_transaction_gc(t);
+}
+
+void dns_transaction_complete(DnsTransaction *t, DnsTransactionState state) {
+        DnsQuery *q;
+        DnsZoneItem *z;
+        Iterator i;
+
+        assert(t);
+        assert(!IN_SET(state, DNS_TRANSACTION_NULL, DNS_TRANSACTION_PENDING));
+        assert(IN_SET(t->state, DNS_TRANSACTION_NULL, DNS_TRANSACTION_PENDING));
+
+        /* Note that this call might invalidate the query. Callers
+         * should hence not attempt to access the query or transaction
+         * after calling this function. */
+
+        log_debug("Transaction on scope %s on %s/%s now complete with <%s>",
+                  dns_protocol_to_string(t->scope->protocol),
+                  t->scope->link ? t->scope->link->name : "*",
+                  t->scope->family == AF_UNSPEC ? "*" : af_to_name(t->scope->family),
+                  dns_transaction_state_to_string(state));
+
+        t->state = state;
+
+        dns_transaction_stop(t);
+
+        /* Notify all queries that are interested, but make sure the
+         * transaction isn't freed while we are still looking at it */
+        t->block_gc++;
+        SET_FOREACH(q, t->queries, i)
+                dns_query_ready(q);
+        SET_FOREACH(z, t->zone_items, i)
+                dns_zone_item_ready(z);
+        t->block_gc--;
+
+        dns_transaction_gc(t);
+}
+
+static int on_stream_complete(DnsStream *s, int error) {
+        _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
+        DnsTransaction *t;
+
+        assert(s);
+        assert(s->transaction);
+
+        /* Copy the data we care about out of the stream before we
+         * destroy it. */
+        t = s->transaction;
+        p = dns_packet_ref(s->read_packet);
+
+        t->stream = dns_stream_free(t->stream);
+
+        if (error != 0) {
+                dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
+                return 0;
+        }
+
+        t->block_gc++;
+        dns_transaction_process_reply(t, p);
+        t->block_gc--;
+
+        /* If the response wasn't useful, then complete the transition now */
+        if (t->state == DNS_TRANSACTION_PENDING)
+                dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
+
+        return 0;
+}
+
+static int dns_transaction_open_tcp(DnsTransaction *t) {
+        _cleanup_close_ int fd = -1;
+        int r;
+
+        assert(t);
+
+        if (t->stream)
+                return 0;
+
+        if (t->scope->protocol == DNS_PROTOCOL_DNS)
+                fd = dns_scope_tcp_socket(t->scope, AF_UNSPEC, NULL, 53);
+        else if (t->scope->protocol == DNS_PROTOCOL_LLMNR) {
+
+                /* When we already received a query to this (but it was truncated), send to its sender address */
+                if (t->received)
+                        fd = dns_scope_tcp_socket(t->scope, t->received->family, &t->received->sender, t->received->sender_port);
+                else {
+                        union in_addr_union address;
+                        int family;
+
+                        /* Otherwise, try to talk to the owner of a
+                         * the IP address, in case this is a reverse
+                         * PTR lookup */
+                        r = dns_question_extract_reverse_address(t->question, &family, &address);
+                        if (r < 0)
+                                return r;
+                        if (r == 0)
+                                return -EINVAL;
+
+                        fd = dns_scope_tcp_socket(t->scope, family, &address, 5355);
+                }
+        } else
+                return -EAFNOSUPPORT;
+
+        if (fd < 0)
+                return fd;
+
+        r = dns_stream_new(t->scope->manager, &t->stream, t->scope->protocol, fd);
+        if (r < 0)
+                return r;
+
+        fd = -1;
+
+        r = dns_stream_write_packet(t->stream, t->sent);
+        if (r < 0) {
+                t->stream = dns_stream_free(t->stream);
+                return r;
+        }
+
+        t->received = dns_packet_unref(t->received);
+        t->stream->complete = on_stream_complete;
+        t->stream->transaction = t;
+
+        /* The interface index is difficult to determine if we are
+         * connecting to the local host, hence fill this in right away
+         * instead of determining it from the socket */
+        if (t->scope->link)
+                t->stream->ifindex = t->scope->link->ifindex;
+
+        return 0;
+}
+
+void dns_transaction_process_reply(DnsTransaction *t, DnsPacket *p) {
+        int r;
+
+        assert(t);
+        assert(p);
+        assert(t->state == DNS_TRANSACTION_PENDING);
+
+        /* Note that this call might invalidate the query. Callers
+         * should hence not attempt to access the query or transaction
+         * after calling this function. */
+
+        if (t->scope->protocol == DNS_PROTOCOL_LLMNR) {
+                assert(t->scope->link);
+
+                /* For LLMNR we will not accept any packets from other
+                 * interfaces */
+
+                if (p->ifindex != t->scope->link->ifindex)
+                        return;
+
+                if (p->family != t->scope->family)
+                        return;
+
+                /* Tentative packets are not full responses but still
+                 * useful for identifying uniqueness conflicts during
+                 * probing. */
+                if (DNS_PACKET_T(p)) {
+                        dns_transaction_tentative(t, p);
+                        return;
+                }
+        }
+
+        if (t->scope->protocol == DNS_PROTOCOL_DNS) {
+
+                /* For DNS we are fine with accepting packets on any
+                 * interface, but the source IP address must be one of
+                 * a valid DNS server */
+
+                if (!dns_scope_good_dns_server(t->scope, p->family, &p->sender))
+                        return;
+
+                if (p->sender_port != 53)
+                        return;
+        }
+
+        if (t->received != p) {
+                dns_packet_unref(t->received);
+                t->received = dns_packet_ref(p);
+        }
+
+        if (p->ipproto == IPPROTO_TCP) {
+                if (DNS_PACKET_TC(p)) {
+                        /* Truncated via TCP? Somebody must be fucking with us */
+                        dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
+                        return;
+                }
+
+                if (DNS_PACKET_ID(p) != t->id) {
+                        /* Not the reply to our query? Somebody must be fucking with us */
+                        dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
+                        return;
+                }
+        }
+
+        if (DNS_PACKET_TC(p)) {
+                /* Response was truncated, let's try again with good old TCP */
+                r = dns_transaction_open_tcp(t);
+                if (r == -ESRCH) {
+                        /* No servers found? Damn! */
+                        dns_transaction_complete(t, DNS_TRANSACTION_NO_SERVERS);
+                        return;
+                }
+                if (r < 0) {
+                        /* On LLMNR, if we cannot connect to the host,
+                         * we immediately give up */
+                        if (t->scope->protocol == DNS_PROTOCOL_LLMNR) {
+                                dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
+                                return;
+                        }
+
+                        /* On DNS, couldn't send? Try immediately again, with a new server */
+                        dns_scope_next_dns_server(t->scope);
+
+                        r = dns_transaction_go(t);
+                        if (r < 0) {
+                                dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
+                                return;
+                        }
+
+                        return;
+                }
+        }
+
+        /* Parse and update the cache */
+        r = dns_packet_extract(p);
+        if (r < 0) {
+                dns_transaction_complete(t, DNS_TRANSACTION_INVALID_REPLY);
+                return;
+        }
+
+        /* According to RFC 4795, section 2.9. only the RRs from the answer section shall be cached */
+        dns_cache_put(&t->scope->cache, p->question, DNS_PACKET_RCODE(p), p->answer, DNS_PACKET_ANCOUNT(p), 0);
+
+        if (DNS_PACKET_RCODE(p) == DNS_RCODE_SUCCESS)
+                dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS);
+        else
+                dns_transaction_complete(t, DNS_TRANSACTION_FAILURE);
+}
+
+static int on_transaction_timeout(sd_event_source *s, usec_t usec, void *userdata) {
+        DnsTransaction *t = userdata;
+        int r;
+
+        assert(s);
+        assert(t);
+
+        /* Timeout reached? Try again, with a new server */
+        dns_scope_next_dns_server(t->scope);
+
+        r = dns_transaction_go(t);
+        if (r < 0)
+                dns_transaction_complete(t, DNS_TRANSACTION_RESOURCES);
+
+        return 0;
+}
+
+static int dns_transaction_make_packet(DnsTransaction *t) {
+        _cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
+        unsigned n, added = 0;
+        int r;
+
+        assert(t);
+
+        if (t->sent)
+                return 0;
+
+        r = dns_packet_new_query(&p, t->scope->protocol, 0);
+        if (r < 0)
+                return r;
+
+        for (n = 0; n < t->question->n_keys; n++) {
+                r = dns_scope_good_key(t->scope, t->question->keys[n]);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        continue;
+
+                r = dns_packet_append_key(p, t->question->keys[n], NULL);
+                if (r < 0)
+                        return r;
+
+                added++;
+        }
+
+        if (added <= 0)
+                return -EDOM;
+
+        DNS_PACKET_HEADER(p)->qdcount = htobe16(added);
+        DNS_PACKET_HEADER(p)->id = t->id;
+
+        t->sent = p;
+        p = NULL;
+
+        return 0;
+}
+
+int dns_transaction_go(DnsTransaction *t) {
+        bool had_stream;
+        int r;
+
+        assert(t);
+
+        had_stream = !!t->stream;
+
+        dns_transaction_stop(t);
+
+        log_debug("Beginning transaction on scope %s on %s/%s",
+                  dns_protocol_to_string(t->scope->protocol),
+                  t->scope->link ? t->scope->link->name : "*",
+                  t->scope->family == AF_UNSPEC ? "*" : af_to_name(t->scope->family));
+
+        if (t->n_attempts >= TRANSACTION_ATTEMPTS_MAX(t->scope->protocol)) {
+                dns_transaction_complete(t, DNS_TRANSACTION_ATTEMPTS_MAX_REACHED);
+                return 0;
+        }
+
+        if (t->scope->protocol == DNS_PROTOCOL_LLMNR && had_stream) {
+                /* If we already tried via a stream, then we don't
+                 * retry on LLMNR. See RFC 4795, Section 2.7. */
+                dns_transaction_complete(t, DNS_TRANSACTION_ATTEMPTS_MAX_REACHED);
+                return 0;
+        }
+
+        t->n_attempts++;
+        t->received = dns_packet_unref(t->received);
+        t->cached = dns_answer_unref(t->cached);
+        t->cached_rcode = 0;
+
+        /* First, let's try the cache */
+        dns_cache_prune(&t->scope->cache);
+        r = dns_cache_lookup(&t->scope->cache, t->question, &t->cached_rcode, &t->cached);
+        if (r < 0)
+                return r;
+        if (r > 0) {
+                if (t->cached_rcode == DNS_RCODE_SUCCESS)
+                        dns_transaction_complete(t, DNS_TRANSACTION_SUCCESS);
+                else
+                        dns_transaction_complete(t, DNS_TRANSACTION_FAILURE);
+                return 0;
+        }
+
+        /* Otherwise, we need to ask the network */
+        r = dns_transaction_make_packet(t);
+        if (r == -EDOM) {
+                /* Not the right request to make on this network?
+                 * (i.e. an A request made on IPv6 or an AAAA request
+                 * made on IPv4, on LLMNR or mDNS.) */
+                dns_transaction_complete(t, DNS_TRANSACTION_NO_SERVERS);
+                return 0;
+        }
+        if (r < 0)
+                return r;
+
+        if (t->scope->protocol == DNS_PROTOCOL_LLMNR &&
+            (dns_question_endswith(t->question, "in-addr.arpa") > 0 ||
+             dns_question_endswith(t->question, "ip6.arpa") > 0)) {
+
+                /* RFC 4795, Section 2.4. says reverse lookups shall
+                 * always be made via TCP on LLMNR */
+                r = dns_transaction_open_tcp(t);
+        } else {
+                /* Try via UDP, and if that fails due to large size try via TCP */
+                r = dns_scope_send(t->scope, t->sent);
+                if (r == -EMSGSIZE)
+                        r = dns_transaction_open_tcp(t);
+        }
+        if (r == -ESRCH) {
+                /* No servers to send this to? */
+                dns_transaction_complete(t, DNS_TRANSACTION_NO_SERVERS);
+                return 0;
+        }
+        if (r < 0) {
+                /* Couldn't send? Try immediately again, with a new server */
+                dns_scope_next_dns_server(t->scope);
+
+                return dns_transaction_go(t);
+        }
+
+        r = sd_event_add_time(t->scope->manager->event, &t->timeout_event_source, CLOCK_MONOTONIC, now(CLOCK_MONOTONIC) + TRANSACTION_TIMEOUT_USEC(t->scope->protocol), 0, on_transaction_timeout, t);
+        if (r < 0)
+                return r;
+
+        t->state = DNS_TRANSACTION_PENDING;
+        return 1;
+}
+
+static const char* const dns_transaction_state_table[_DNS_TRANSACTION_STATE_MAX] = {
+        [DNS_TRANSACTION_NULL] = "null",
+        [DNS_TRANSACTION_PENDING] = "pending",
+        [DNS_TRANSACTION_FAILURE] = "failure",
+        [DNS_TRANSACTION_SUCCESS] = "success",
+        [DNS_TRANSACTION_NO_SERVERS] = "no-servers",
+        [DNS_TRANSACTION_TIMEOUT] = "timeout",
+        [DNS_TRANSACTION_ATTEMPTS_MAX_REACHED] = "attempts-max-reached",
+        [DNS_TRANSACTION_INVALID_REPLY] = "invalid-reply",
+        [DNS_TRANSACTION_RESOURCES] = "resources",
+        [DNS_TRANSACTION_ABORTED] = "aborted",
+};
+DEFINE_STRING_TABLE_LOOKUP(dns_transaction_state, DnsTransactionState);