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/* SPDX-License-Identifier: LGPL-2.1-or-later */
#if !ENABLE_DNS_OVER_TLS || !DNS_OVER_TLS_USE_GNUTLS
#error This source file requires DNS-over-TLS to be enabled and GnuTLS to be available.
#endif
#include <gnutls/socket.h>
#include "resolved-dns-stream.h"
#include "resolved-dnstls.h"
#include "resolved-manager.h"
#define TLS_PROTOCOL_PRIORITY "NORMAL:-VERS-ALL:+VERS-TLS1.3:+VERS-TLS1.2"
DEFINE_TRIVIAL_CLEANUP_FUNC(gnutls_session_t, gnutls_deinit);
static ssize_t dnstls_stream_writev(gnutls_transport_ptr_t p, const giovec_t *iov, int iovcnt) {
int r;
assert(p);
r = dns_stream_writev((DnsStream*) p, (const struct iovec*) iov, iovcnt, DNS_STREAM_WRITE_TLS_DATA);
if (r < 0) {
errno = -r;
return -1;
}
return r;
}
int dnstls_stream_connect_tls(DnsStream *stream, DnsServer *server) {
_cleanup_(gnutls_deinitp) gnutls_session_t gs = NULL;
int r;
assert(stream);
assert(server);
r = gnutls_init(&gs, GNUTLS_CLIENT | GNUTLS_ENABLE_FALSE_START | GNUTLS_NONBLOCK);
if (r < 0)
return r;
/* As DNS-over-TLS is a recent protocol, older TLS versions can be disabled */
r = gnutls_priority_set_direct(gs, TLS_PROTOCOL_PRIORITY, NULL);
if (r < 0)
return r;
r = gnutls_credentials_set(gs, GNUTLS_CRD_CERTIFICATE, stream->manager->dnstls_data.cert_cred);
if (r < 0)
return r;
if (server->dnstls_data.session_data.size > 0) {
gnutls_session_set_data(gs, server->dnstls_data.session_data.data, server->dnstls_data.session_data.size);
// Clear old session ticket
gnutls_free(server->dnstls_data.session_data.data);
server->dnstls_data.session_data.data = NULL;
server->dnstls_data.session_data.size = 0;
}
if (server->manager->dns_over_tls_mode == DNS_OVER_TLS_YES) {
if (server->server_name)
gnutls_session_set_verify_cert(gs, server->server_name, 0);
else {
stream->dnstls_data.validation.type = GNUTLS_DT_IP_ADDRESS;
if (server->family == AF_INET) {
stream->dnstls_data.validation.data = (unsigned char*) &server->address.in.s_addr;
stream->dnstls_data.validation.size = 4;
} else {
stream->dnstls_data.validation.data = server->address.in6.s6_addr;
stream->dnstls_data.validation.size = 16;
}
gnutls_session_set_verify_cert2(gs, &stream->dnstls_data.validation, 1, 0);
}
}
if (server->server_name) {
r = gnutls_server_name_set(gs, GNUTLS_NAME_DNS, server->server_name, strlen(server->server_name));
if (r < 0)
return log_debug_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to set server name: %s", gnutls_strerror(r));
}
gnutls_handshake_set_timeout(gs, GNUTLS_DEFAULT_HANDSHAKE_TIMEOUT);
gnutls_transport_set_ptr2(gs, (gnutls_transport_ptr_t) (long) stream->fd, stream);
gnutls_transport_set_vec_push_function(gs, &dnstls_stream_writev);
stream->encrypted = true;
stream->dnstls_data.handshake = gnutls_handshake(gs);
if (stream->dnstls_data.handshake < 0 && gnutls_error_is_fatal(stream->dnstls_data.handshake))
return -ECONNREFUSED;
stream->dnstls_data.session = TAKE_PTR(gs);
return 0;
}
void dnstls_stream_free(DnsStream *stream) {
assert(stream);
assert(stream->encrypted);
if (stream->dnstls_data.session)
gnutls_deinit(stream->dnstls_data.session);
}
int dnstls_stream_on_io(DnsStream *stream, uint32_t revents) {
int r;
assert(stream);
assert(stream->encrypted);
assert(stream->dnstls_data.session);
if (stream->dnstls_data.shutdown) {
r = gnutls_bye(stream->dnstls_data.session, GNUTLS_SHUT_RDWR);
if (r == GNUTLS_E_AGAIN) {
stream->dnstls_events = gnutls_record_get_direction(stream->dnstls_data.session) == 1 ? EPOLLOUT : EPOLLIN;
return -EAGAIN;
} else if (r < 0)
log_debug("Failed to invoke gnutls_bye: %s", gnutls_strerror(r));
stream->dnstls_events = 0;
stream->dnstls_data.shutdown = false;
dns_stream_unref(stream);
return DNSTLS_STREAM_CLOSED;
} else if (stream->dnstls_data.handshake < 0) {
stream->dnstls_data.handshake = gnutls_handshake(stream->dnstls_data.session);
if (stream->dnstls_data.handshake == GNUTLS_E_AGAIN) {
stream->dnstls_events = gnutls_record_get_direction(stream->dnstls_data.session) == 1 ? EPOLLOUT : EPOLLIN;
return -EAGAIN;
} else if (stream->dnstls_data.handshake < 0) {
log_debug("Failed to invoke gnutls_handshake: %s", gnutls_strerror(stream->dnstls_data.handshake));
if (gnutls_error_is_fatal(stream->dnstls_data.handshake))
return -ECONNREFUSED;
}
stream->dnstls_events = 0;
}
return 0;
}
int dnstls_stream_shutdown(DnsStream *stream, int error) {
int r;
assert(stream);
assert(stream->encrypted);
assert(stream->dnstls_data.session);
/* Store TLS Ticket for faster successive TLS handshakes */
if (stream->server && stream->server->dnstls_data.session_data.size == 0 && stream->dnstls_data.handshake == GNUTLS_E_SUCCESS)
gnutls_session_get_data2(stream->dnstls_data.session, &stream->server->dnstls_data.session_data);
if (IN_SET(error, ETIMEDOUT, 0)) {
r = gnutls_bye(stream->dnstls_data.session, GNUTLS_SHUT_RDWR);
if (r == GNUTLS_E_AGAIN) {
if (!stream->dnstls_data.shutdown) {
stream->dnstls_data.shutdown = true;
dns_stream_ref(stream);
return -EAGAIN;
}
} else if (r < 0)
log_debug("Failed to invoke gnutls_bye: %s", gnutls_strerror(r));
}
return 0;
}
ssize_t dnstls_stream_write(DnsStream *stream, const char *buf, size_t count) {
ssize_t ss;
assert(stream);
assert(stream->encrypted);
assert(stream->dnstls_data.session);
assert(buf);
ss = gnutls_record_send(stream->dnstls_data.session, buf, count);
if (ss < 0)
switch(ss) {
case GNUTLS_E_INTERRUPTED:
return -EINTR;
case GNUTLS_E_AGAIN:
return -EAGAIN;
default:
return log_debug_errno(SYNTHETIC_ERRNO(EPIPE),
"Failed to invoke gnutls_record_send: %s",
gnutls_strerror(ss));
}
return ss;
}
ssize_t dnstls_stream_read(DnsStream *stream, void *buf, size_t count) {
ssize_t ss;
assert(stream);
assert(stream->encrypted);
assert(stream->dnstls_data.session);
assert(buf);
ss = gnutls_record_recv(stream->dnstls_data.session, buf, count);
if (ss < 0)
switch(ss) {
case GNUTLS_E_INTERRUPTED:
return -EINTR;
case GNUTLS_E_AGAIN:
return -EAGAIN;
default:
return log_debug_errno(SYNTHETIC_ERRNO(EPIPE),
"Failed to invoke gnutls_record_recv: %s",
gnutls_strerror(ss));
}
return ss;
}
void dnstls_server_free(DnsServer *server) {
assert(server);
if (server->dnstls_data.session_data.data)
gnutls_free(server->dnstls_data.session_data.data);
}
int dnstls_manager_init(Manager *manager) {
int r;
assert(manager);
r = gnutls_certificate_allocate_credentials(&manager->dnstls_data.cert_cred);
if (r < 0)
return -ENOMEM;
r = gnutls_certificate_set_x509_system_trust(manager->dnstls_data.cert_cred);
if (r < 0)
log_warning("Failed to load system trust store: %s", gnutls_strerror(r));
return 0;
}
void dnstls_manager_free(Manager *manager) {
assert(manager);
if (manager->dnstls_data.cert_cred)
gnutls_certificate_free_credentials(manager->dnstls_data.cert_cred);
}
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