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systemd/src/resolve/test-resolved-stream.c
Lennart Poettering e9ccae3135 process-util: add new FORK_DEATHSIG_SIGKILL flag, rename FORK_DEATHSIG → FORK_DEATHSIG_SIGTERM 
Sometimes it makes sense to hard kill a client if we die. Let's hence
add a third FORK_DEATHSIG flag for this purpose: FORK_DEATHSIG_SIGKILL.

To make things less confusing this also renames FORK_DEATHSIG to
FORK_DEATHSIG_SIGTERM to make clear it sends SIGTERM. We already had
FORK_DEATHSIG_SIGINT, hence this makes things nicely symmetric.

A bunch of users are switched over for FORK_DEATHSIG_SIGKILL where we
know it's safe to abort things abruptly. This should make some kernel
cases more robust, since we cannot get confused by signal masks or such.

While we are at it, also fix a bunch of bugs where we didn't take
FORK_DEATHSIG_SIGINT into account in safe_fork()
2023-11-02 14:09:23 +01:00

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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#include <arpa/inet.h>
#include <fcntl.h>
#include <net/if.h>
#include <net/if_arp.h>
#include <pthread.h>
#include <signal.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/prctl.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <unistd.h>
#include "fd-util.h"
#include "log.h"
#include "macro.h"
#include "path-util.h"
#include "process-util.h"
#include "random-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 union sockaddr_union 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 = -EBADF, acceptfd = -EBADF;
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.sa, SOCKADDR_LEN(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 = -EBADF, fd_tls = -EBADF;
_cleanup_free_ char *cert_path = NULL, *key_path = NULL;
_cleanup_free_ char *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(asprintf(&bind_str, "%s:%d",
IN_ADDR_TO_STRING(server_address.in.sin_family,
sockaddr_in_addr(&server_address.sa)),
be16toh(server_address.in.sin_port)) >= 0);
/* 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_tls, fd_tls, STDOUT_FILENO },
NULL, 0,
FORK_RESET_SIGNALS|FORK_CLOSE_ALL_FDS|FORK_DEATHSIG_SIGTERM|FORK_REARRANGE_STDIO|FORK_LOG|FORK_REOPEN_LOG,
&openssl_pid);
assert_se(r >= 0);
if (r == 0) {
/* Child */
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, DnsPacket *p) {
assert_se(n_received_packets < MAX_RECEIVED_PACKETS);
assert_se(received_packets[n_received_packets++] = dns_packet_ref(p));
return 0;
}
static int on_stream_complete_do_nothing(DnsStream *s, int error) {
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 = -EBADF;
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.sa, SOCKADDR_LEN(server_address));
if (r >= 0)
break;
usleep_safe(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 (disabling the default self-destruction
behaviour when no complete callback is set) */
assert_se(dns_stream_new(&manager, &stream, DNS_STREAM_LOOKUP, DNS_PROTOCOL_DNS,
TAKE_FD(clientfd), NULL, on_stream_packet, on_stream_complete_do_nothing,
DNS_STREAM_DEFAULT_TIMEOUT_USEC) >= 0);
#if ENABLE_DNS_OVER_TLS
if (tls) {
DnsServer server = {
.manager = &manager,
.family = server_address.sa.sa_family,
.address = *sockaddr_in_addr(&server_address.sa),
};
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");
}
static void try_isolate_network(void) {
_cleanup_close_ int socket_fd = -EBADF;
int r;
/* First test if CLONE_NEWUSER/CLONE_NEWNET can actually work for us, i.e. we can open the namespaces
* and then still access the build dir we are run from. We do that in a child process since it's
* nasty if we have to go back from the namespace once we entered it and realized it cannot work. */
r = safe_fork("(usernstest)", FORK_DEATHSIG_SIGKILL|FORK_LOG|FORK_WAIT, NULL);
if (r == 0) { /* child */
_cleanup_free_ char *rt = NULL, *d = NULL;
if (unshare(CLONE_NEWUSER | CLONE_NEWNET) < 0) {
log_warning_errno(errno, "test-resolved-stream: Can't create user and network ns, running on host: %m");
_exit(EXIT_FAILURE);
}
assert_se(get_process_exe(0, &rt) >= 0);
assert_se(path_extract_directory(rt, &d) >= 0);
if (access(d, F_OK) < 0) {
log_warning_errno(errno, "test-resolved-stream: Can't access /proc/self/exe from user/network ns, running on host: %m");
_exit(EXIT_FAILURE);
}
_exit(EXIT_SUCCESS);
}
if (r == -EPROTO) /* EPROTO means nonzero exit code of child, i.e. the tests in the child failed */
return;
assert_se(r > 0);
/* Now that we know that the unshare() is safe, let's actually do it */
assert_se(unshare(CLONE_NEWUSER | CLONE_NEWNET) >= 0);
/* Bring up the loopback interfaceon the newly created network namespace */
struct ifreq req = { .ifr_ifindex = 1 };
assert_se((socket_fd = socket(AF_INET, SOCK_STREAM | SOCK_CLOEXEC, 0)) >= 0);
assert_se(ioctl(socket_fd, SIOCGIFNAME, &req) >= 0);
assert_se(ioctl(socket_fd, SIOCGIFFLAGS, &req) >= 0);
assert_se(FLAGS_SET(req.ifr_flags, IFF_LOOPBACK));
req.ifr_flags |= IFF_UP;
assert_se(ioctl(socket_fd, SIOCSIFFLAGS, &req) >= 0);
}
int main(int argc, char **argv) {
server_address = (union sockaddr_union) {
.in.sin_family = AF_INET,
.in.sin_port = htobe16(random_u64_range(UINT16_MAX - 1024) + 1024),
.in.sin_addr.s_addr = htobe32(INADDR_LOOPBACK)
};
test_setup_logging(LOG_DEBUG);
try_isolate_network();
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;
}
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