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Merge pull request #22132 from joanbm/main

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resolved: Fix DoT timeout on multiple answer records (for CloudFlare, Google, etc. DoT servers)
This commit is contained in:
Yu Watanabe
2022-01-28 04:23:34 +09:00
committed by GitHub
parent d5dd3c26eb 726bcd81b9
commit 33db66aa36
8 changed files with 497 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/resolve/meson.build
+10 -1
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@@ -70,7 +70,6 @@ systemd_resolved_sources = files('''
resolved-socket-graveyard.h
resolved-varlink.c
resolved-varlink.h
resolved.c
'''.split())
resolvectl_sources = files('''
@@ -200,6 +199,14 @@ tests += [
[lib_openssl_or_gcrypt,
libm]],
[files('test-resolved-stream.c')
+ basic_dns_sources + systemd_resolved_sources,
[libshared],
[lib_openssl_or_gcrypt,
libm]
+ systemd_resolved_dependencies,
resolve_includes],
[files('test-dnssec.c'),
[libsystemd_resolve_core,
libshared],
@@ -229,3 +236,5 @@ fuzzers += [
[lib_openssl_or_gcrypt,
libm]],
]
systemd_resolved_sources += files('resolved.c')
src/resolve/resolved-dns-stream.c
+43 -2
View File
@@ -6,6 +6,7 @@
#include "alloc-util.h"
#include "fd-util.h"
#include "io-util.h"
#include "macro.h"
#include "missing_network.h"
#include "resolved-dns-stream.h"
#include "resolved-manager.h"
@@ -280,13 +281,15 @@ static int on_stream_timeout(sd_event_source *es, usec_t usec, void *userdata) {
return dns_stream_complete(s, ETIMEDOUT);
}
static int on_stream_io(sd_event_source *es, int fd, uint32_t revents, void *userdata) {
_cleanup_(dns_stream_unrefp) DnsStream *s = dns_stream_ref(userdata); /* Protect stream while we process it */
static int on_stream_io_impl(DnsStream *s, uint32_t revents) {
bool progressed = false;
int r;
assert(s);
/* This returns 1 when possible remaining stream exists, 0 on completed
stream or recoverable error, and negative errno on failure. */
#if ENABLE_DNS_OVER_TLS
if (s->encrypted) {
r = dnstls_stream_on_io(s, revents);
@@ -441,6 +444,44 @@ static int on_stream_io(sd_event_source *es, int fd, uint32_t revents, void *use
log_warning_errno(errno, "Couldn't restart TCP connection timeout, ignoring: %m");
}
return 1;
}
static int on_stream_io(sd_event_source *es, int fd, uint32_t revents, void *userdata) {
_cleanup_(dns_stream_unrefp) DnsStream *s = dns_stream_ref(userdata); /* Protect stream while we process it */
int r;
assert(s);
r = on_stream_io_impl(s, revents);
if (r <= 0)
return r;
#if ENABLE_DNS_OVER_TLS
if (!s->encrypted)
return 0;
/* When using DNS-over-TLS, the underlying TLS library may read the entire TLS record
and buffer it internally. If this happens, we will not receive further EPOLLIN events,
and unless there's some unrelated activity on the socket, we will hang until time out.
To avoid this, if there's buffered TLS data, generate a "fake" EPOLLIN event.
This is hacky, but it makes this case transparent to the rest of the IO code. */
while (dnstls_stream_has_buffered_data(s)) {
uint32_t events;
/* Make sure the stream still wants to process more data... */
r = sd_event_source_get_io_events(s->io_event_source, &events);
if (r < 0)
return r;
if (!FLAGS_SET(events, EPOLLIN))
break;
r = on_stream_io_impl(s, EPOLLIN);
if (r <= 0)
return r;
}
#endif
return 0;
}
src/resolve/resolved-dnstls-gnutls.c
+8
View File
@@ -211,6 +211,14 @@ ssize_t dnstls_stream_read(DnsStream *stream, void *buf, size_t count) {
return ss;
}
bool dnstls_stream_has_buffered_data(DnsStream *stream) {
assert(stream);
assert(stream->encrypted);
assert(stream->dnstls_data.session);
return gnutls_record_check_pending(stream->dnstls_data.session) > 0;
}
void dnstls_server_free(DnsServer *server) {
assert(server);
src/resolve/resolved-dnstls-openssl.c
+8
View File
@@ -367,6 +367,14 @@ ssize_t dnstls_stream_read(DnsStream *stream, void *buf, size_t count) {
return ss;
}
bool dnstls_stream_has_buffered_data(DnsStream *stream) {
assert(stream);
assert(stream->encrypted);
assert(stream->dnstls_data.ssl);
return SSL_has_pending(stream->dnstls_data.ssl) > 0;
}
void dnstls_server_free(DnsServer *server) {
assert(server);
src/resolve/resolved-dnstls.h
+2
View File
@@ -3,6 +3,7 @@
#if ENABLE_DNS_OVER_TLS
#include <stdbool.h>
#include <stdint.h>
typedef struct DnsServer DnsServer;
@@ -28,6 +29,7 @@ int dnstls_stream_on_io(DnsStream *stream, uint32_t revents);
int dnstls_stream_shutdown(DnsStream *stream, int error);
ssize_t dnstls_stream_write(DnsStream *stream, const char *buf, size_t count);
ssize_t dnstls_stream_read(DnsStream *stream, void *buf, size_t count);
bool dnstls_stream_has_buffered_data(DnsStream *stream);
void dnstls_server_free(DnsServer *server);
src/resolve/test-resolved-stream.c
+342
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@@ -0,0 +1,342 @@
/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <arpa/inet.h>
#include <fcntl.h>
#include <pthread.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <sys/prctl.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <unistd.h>
#include "fd-util.h"
#include "log.h"
#include "process-util.h"
#include "resolved-dns-packet.h"
#include "resolved-dns-question.h"
#include "resolved-dns-rr.h"
#if ENABLE_DNS_OVER_TLS
#include "resolved-dnstls.h"
#endif
#include "resolved-dns-server.h"
#include "resolved-dns-stream.h"
#include "resolved-manager.h"
#include "sd-event.h"
#include "sparse-endian.h"
#include "tests.h"
static struct sockaddr_in SERVER_ADDRESS;
/* Bytes of the questions & answers used in the test, including TCP DNS 2-byte length prefix */
static const uint8_t QUESTION_A[] = {
0x00, 0x1D, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 'e',
'x' , 'a' , 'm' , 'p' , 'l' , 'e' , 0x03, 'c' , 'o' , 'm' , 0x00, 0x00, 0x01, 0x00, 0x01
};
static const uint8_t QUESTION_AAAA[] = {
0x00, 0x1D, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x07, 'e',
'x' , 'a' , 'm' , 'p' , 'l' , 'e' , 0x03, 'c' , 'o' , 'm' , 0x00, 0x00, 0x1C, 0x00, 0x01
};
static const uint8_t ANSWER_A[] = {
0x00, 0x2D, 0x00, 0x00, 0x81, 0x80, 0x00, 0x01, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x07, 'e',
'x' , 'a' , 'm' , 'p' , 'l' , 'e' , 0x03, 'c' , 'o' , 'm' , 0x00, 0x00, 0x01, 0x00, 0x01, 0xC0,
0x0C, 0x00, 0x01, 0x00, 0x01, 0x00, 0x00, 0x52, 0x8D, 0x00, 0x04, 0x5D, 0xB8, 0xD8, 0x22,
};
static const uint8_t ANSWER_AAAA[] = {
0x00, 0x39, 0x00, 0x00, 0x81, 0x80, 0x00, 0x01, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x07, 'e',
'x' , 'a' , 'm' , 'p' , 'l' , 'e' , 0x03, 'c' , 'o' , 'm' , 0x00, 0x00, 0x1C, 0x00, 0x01, 0xC0,
0x0C, 0x00, 0x1C, 0x00, 0x01, 0x00, 0x00, 0x54, 0x4B, 0x00, 0x10, 0x26, 0x06, 0x28, 0x00, 0x02,
0x20, 0x00, 0x01, 0x02, 0x48, 0x18, 0x93, 0x25, 0xC8, 0x19, 0x46,
};
/**
* A mock TCP DNS server that asserts certain questions are received
* and replies with the same answer every time.
*/
static void receive_and_check_question(int fd, const uint8_t *expected_question,
size_t question_size) {
uint8_t *actual_question;
size_t n_read = 0;
actual_question = newa(uint8_t, question_size);
while (n_read < question_size) {
ssize_t r = read(fd, actual_question + n_read, question_size - n_read);
assert_se(r >= 0);
n_read += (size_t)r;
}
assert_se(n_read == question_size);
assert_se(memcmp(expected_question, actual_question, question_size) == 0);
}
static void send_answer(int fd, const uint8_t *answer, size_t answer_size) {
assert_se(write(fd, answer, answer_size) == (ssize_t)answer_size);
}
/* Sends two answers together in a single write operation,
* so they hopefully end up in a single TCP packet / TLS record */
static void send_answers_together(int fd,
const uint8_t *answer1, size_t answer1_size,
const uint8_t *answer2, size_t answer2_size) {
uint8_t *answer;
size_t answer_size = answer1_size + answer2_size;
answer = newa(uint8_t, answer_size);
memcpy(answer, answer1, answer1_size);
memcpy(answer + answer1_size, answer2, answer2_size);
assert_se(write(fd, answer, answer_size) == (ssize_t)answer_size);
}
static void server_handle(int fd) {
receive_and_check_question(fd, QUESTION_A, sizeof(QUESTION_A));
send_answer(fd, ANSWER_A, sizeof(ANSWER_A));
receive_and_check_question(fd, QUESTION_AAAA, sizeof(QUESTION_AAAA));
send_answer(fd, ANSWER_AAAA, sizeof(ANSWER_AAAA));
receive_and_check_question(fd, QUESTION_A, sizeof(QUESTION_A));
receive_and_check_question(fd, QUESTION_AAAA, sizeof(QUESTION_AAAA));
send_answers_together(fd, ANSWER_A, sizeof(ANSWER_A),
ANSWER_AAAA, sizeof(ANSWER_AAAA));
}
static void *tcp_dns_server(void *p) {
_cleanup_close_ int bindfd = -1, acceptfd = -1;
assert_se((bindfd = socket(AF_INET, SOCK_STREAM | SOCK_CLOEXEC, 0)) >= 0);
assert_se(setsockopt(bindfd, SOL_SOCKET, SO_REUSEADDR, &(int){1}, sizeof(int)) >= 0);
assert_se(bind(bindfd, &SERVER_ADDRESS, sizeof(SERVER_ADDRESS)) >= 0);
assert_se(listen(bindfd, 1) >= 0);
assert_se((acceptfd = accept(bindfd, NULL, NULL)) >= 0);
server_handle(acceptfd);
return NULL;
}
#if ENABLE_DNS_OVER_TLS
/*
* Spawns a DNS TLS server using the command line "openssl s_server" tool.
*/
static void *tls_dns_server(void *p) {
pid_t openssl_pid;
int r;
_cleanup_close_ int fd_server = -1, fd_tls = -1;
_cleanup_free_ char *cert_path = NULL, *key_path = NULL;
_cleanup_free_ char *ip_str = NULL, *bind_str = NULL;
assert_se(get_testdata_dir("test-resolve/selfsigned.cert", &cert_path) >= 0);
assert_se(get_testdata_dir("test-resolve/selfsigned.key", &key_path) >= 0);
assert_se(in_addr_to_string(SERVER_ADDRESS.sin_family,
&(union in_addr_union){.in = SERVER_ADDRESS.sin_addr},
&ip_str) >= 0);
asprintf(&bind_str, "%s:%d", ip_str, be16toh(SERVER_ADDRESS.sin_port));
/* We will hook one of the socketpair ends to OpenSSL's TLS server
* stdin/stdout, so we will be able to read and write plaintext
* from the other end's file descriptor like an usual TCP server */
{
int fd[2];
assert_se(socketpair(AF_UNIX, SOCK_STREAM, 0, fd) >= 0);
fd_server = fd[0];
fd_tls = fd[1];
}
r = safe_fork_full("(test-resolved-stream-tls-openssl)", (int[]) { fd_server, fd_tls }, 2,
FORK_RESET_SIGNALS|FORK_CLOSE_ALL_FDS|FORK_DEATHSIG|FORK_LOG|FORK_REOPEN_LOG, &openssl_pid);
assert(r >= 0);
if (r == 0) {
/* Child */
assert_se(dup2(fd_tls, STDIN_FILENO) >= 0);
assert_se(dup2(fd_tls, STDOUT_FILENO) >= 0);
close(TAKE_FD(fd_server));
close(TAKE_FD(fd_tls));
execlp("openssl", "openssl", "s_server", "-accept", bind_str,
"-key", key_path, "-cert", cert_path,
"-quiet", "-naccept", "1", NULL);
log_error("exec failed, is something wrong with the 'openssl' command?");
_exit(EXIT_FAILURE);
} else {
pthread_mutex_t *server_lock = (pthread_mutex_t *)p;
server_handle(fd_server);
/* Once the test is done kill the TLS server to release the port */
assert_se(pthread_mutex_lock(server_lock) == 0);
assert_se(kill(openssl_pid, SIGTERM) >= 0);
assert_se(waitpid(openssl_pid, NULL, 0) >= 0);
assert_se(pthread_mutex_unlock(server_lock) == 0);
}
return NULL;
}
#endif
static const char *TEST_DOMAIN = "example.com";
static const uint64_t EVENT_TIMEOUT_USEC = 5 * 1000 * 1000;
static void send_simple_question(DnsStream *stream, uint16_t type) {
_cleanup_(dns_packet_unrefp) DnsPacket *p = NULL;
_cleanup_(dns_resource_key_unrefp) DnsResourceKey *key = NULL;
_cleanup_(dns_question_unrefp) DnsQuestion *question = NULL;
assert_se(dns_packet_new(&p, DNS_PROTOCOL_DNS, 0, DNS_PACKET_SIZE_MAX) >= 0);
assert_se(question = dns_question_new(1));
assert_se(key = dns_resource_key_new(DNS_CLASS_IN, type, TEST_DOMAIN));
assert_se(dns_question_add(question, key, 0) >= 0);
assert_se(dns_packet_append_question(p, question) >= 0);
DNS_PACKET_HEADER(p)->qdcount = htobe16(dns_question_size(question));
assert_se(dns_stream_write_packet(stream, p) >= 0);
}
static const size_t MAX_RECEIVED_PACKETS = 2;
static DnsPacket *received_packets[2] = {};
static size_t n_received_packets = 0;
static int on_stream_packet(DnsStream *stream) {
assert_se(n_received_packets < MAX_RECEIVED_PACKETS);
assert_se(received_packets[n_received_packets++] = dns_stream_take_read_packet(stream));
return 0;
}
static void test_dns_stream(bool tls) {
Manager manager = {};
_cleanup_(dns_stream_unrefp) DnsStream *stream = NULL;
_cleanup_(sd_event_unrefp) sd_event *event = NULL;
_cleanup_close_ int clientfd = -1;
int r;
void *(*server_entrypoint)(void *);
pthread_t server_thread;
pthread_mutex_t server_lock;
log_info("test-resolved-stream: Started %s test", tls ? "TLS" : "TCP");
#if ENABLE_DNS_OVER_TLS
if (tls) {
/* For TLS mode, use DNS_OVER_TLS_OPPORTUNISTIC instead of
* DNS_OVER_TLS_YES, just to make certificate validation more
* lenient, allowing us to use self-signed certificates.
* We never downgrade, everything we test always goes over TLS */
manager.dns_over_tls_mode = DNS_OVER_TLS_OPPORTUNISTIC;
}
#endif
assert_se(sd_event_new(&event) >= 0);
manager.event = event;
/* Set up a mock DNS (over TCP or TLS) server */
server_entrypoint = tcp_dns_server;
#if ENABLE_DNS_OVER_TLS
if (tls)
server_entrypoint = tls_dns_server;
#endif
assert_se(pthread_mutex_init(&server_lock, NULL) == 0);
assert_se(pthread_mutex_lock(&server_lock) == 0);
assert_se(pthread_create(&server_thread, NULL, server_entrypoint, &server_lock) == 0);
/* Create a socket client and connect to the TCP or TLS server
* The server may not be up immediately, so try to connect a few times before failing */
assert_se((clientfd = socket(AF_INET, SOCK_STREAM | SOCK_CLOEXEC, 0)) >= 0);
for (int i = 0; i < 100; i++) {
r = connect(clientfd, &SERVER_ADDRESS, sizeof(SERVER_ADDRESS));
if (r >= 0)
break;
usleep(EVENT_TIMEOUT_USEC / 100);
}
assert_se(r >= 0);
/* systemd-resolved uses (and requires) the socket to be in nonblocking mode */
assert_se(fcntl(clientfd, F_SETFL, O_NONBLOCK) >= 0);
/* Initialize DNS stream */
assert_se(dns_stream_new(&manager, &stream, DNS_STREAM_LOOKUP, DNS_PROTOCOL_DNS,
TAKE_FD(clientfd), NULL, DNS_STREAM_DEFAULT_TIMEOUT_USEC) >= 0);
stream->on_packet = on_stream_packet;
#if ENABLE_DNS_OVER_TLS
if (tls) {
DnsServer server = {
.manager = &manager,
.family = SERVER_ADDRESS.sin_family,
.address.in = SERVER_ADDRESS.sin_addr
};
assert_se(dnstls_manager_init(&manager) >= 0);
assert_se(dnstls_stream_connect_tls(stream, &server) >= 0);
}
#endif
/* Test: Question of type A and associated answer */
log_info("test-resolved-stream: A record");
send_simple_question(stream, DNS_TYPE_A);
while (n_received_packets != 1)
assert_se(sd_event_run(event, EVENT_TIMEOUT_USEC) >= 1);
assert_se(DNS_PACKET_DATA(received_packets[0]));
assert_se(memcmp(DNS_PACKET_DATA(received_packets[0]),
ANSWER_A + 2, sizeof(ANSWER_A) - 2) == 0);
dns_packet_unref(TAKE_PTR(received_packets[0]));
n_received_packets = 0;
/* Test: Question of type AAAA and associated answer */
log_info("test-resolved-stream: AAAA record");
send_simple_question(stream, DNS_TYPE_AAAA);
while (n_received_packets != 1)
assert_se(sd_event_run(event, EVENT_TIMEOUT_USEC) >= 1);
assert_se(DNS_PACKET_DATA(received_packets[0]));
assert_se(memcmp(DNS_PACKET_DATA(received_packets[0]),
ANSWER_AAAA + 2, sizeof(ANSWER_AAAA) - 2) == 0);
dns_packet_unref(TAKE_PTR(received_packets[0]));
n_received_packets = 0;
/* Test: Question of type A and AAAA and associated answers
* Both answers are sent back in a single packet or TLS record
* (tests the fix of PR #22132: "Fix DoT timeout on multiple answer records") */
log_info("test-resolved-stream: A + AAAA record");
send_simple_question(stream, DNS_TYPE_A);
send_simple_question(stream, DNS_TYPE_AAAA);
while (n_received_packets != 2)
assert_se(sd_event_run(event, EVENT_TIMEOUT_USEC) >= 1);
assert_se(DNS_PACKET_DATA(received_packets[0]));
assert_se(DNS_PACKET_DATA(received_packets[1]));
assert_se(memcmp(DNS_PACKET_DATA(received_packets[0]),
ANSWER_A + 2, sizeof(ANSWER_A) - 2) == 0);
assert_se(memcmp(DNS_PACKET_DATA(received_packets[1]),
ANSWER_AAAA + 2, sizeof(ANSWER_AAAA) - 2) == 0);
dns_packet_unref(TAKE_PTR(received_packets[0]));
dns_packet_unref(TAKE_PTR(received_packets[1]));
n_received_packets = 0;
#if ENABLE_DNS_OVER_TLS
if (tls)
dnstls_manager_free(&manager);
#endif
/* Stop the DNS server */
assert_se(pthread_mutex_unlock(&server_lock) == 0);
assert_se(pthread_join(server_thread, NULL) == 0);
assert_se(pthread_mutex_destroy(&server_lock) == 0);
log_info("test-resolved-stream: Finished %s test", tls ? "TLS" : "TCP");
}
int main(int argc, char **argv) {
SERVER_ADDRESS = (struct sockaddr_in) {
.sin_family = AF_INET,
.sin_port = htobe16(12345),
.sin_addr.s_addr = htobe32(INADDR_LOOPBACK)
};
test_setup_logging(LOG_DEBUG);
test_dns_stream(false);
#if ENABLE_DNS_OVER_TLS
if (system("openssl version >/dev/null 2>&1") != 0)
return log_tests_skipped("Skipping TLS test since the 'openssl' command does not seem to be available");
test_dns_stream(true);
#endif
return 0;
}