src/resolve/resolved-dnstls-gnutls.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #if !ENABLE_DNS_OVER_TLS || !DNS_OVER_TLS_USE_GNUTLS
   4 #error This source file requires DNS-over-TLS to be enabled and GnuTLS to be available.
   5 #endif
   6
   7 #include <gnutls/socket.h>
   8
   9 #include "resolved-dns-stream.h"
  10 #include "resolved-dnstls.h"
  11
  12 #define TLS_PROTOCOL_PRIORITY "NORMAL:-VERS-ALL:+VERS-TLS1.3:+VERS-TLS1.2"
  13 DEFINE_TRIVIAL_CLEANUP_FUNC(gnutls_session_t, gnutls_deinit);
  14
  15 static ssize_t dnstls_stream_writev(gnutls_transport_ptr_t p, const giovec_t *iov, int iovcnt) {
  16         int r;
  17
  18         assert(p);
  19
  20         r = dns_stream_writev((DnsStream*) p, (const struct iovec*) iov, iovcnt, DNS_STREAM_WRITE_TLS_DATA);
  21         if (r < 0) {
  22                 errno = -r;
  23                 return -1;
  24         }
  25
  26         return r;
  27 }
  28
  29 int dnstls_stream_connect_tls(DnsStream *stream, DnsServer *server) {
  30         _cleanup_(gnutls_deinitp) gnutls_session_t gs;
  31         int r;
  32
  33         assert(stream);
  34         assert(server);
  35
  36         r = gnutls_init(&gs, GNUTLS_CLIENT | GNUTLS_ENABLE_FALSE_START | GNUTLS_NONBLOCK);
  37         if (r < 0)
  38                 return r;
  39
  40         /* As DNS-over-TLS is a recent protocol, older TLS versions can be disabled */
  41         r = gnutls_priority_set_direct(gs, TLS_PROTOCOL_PRIORITY, NULL);
  42         if (r < 0)
  43                 return r;
  44
  45         r = gnutls_credentials_set(gs, GNUTLS_CRD_CERTIFICATE, stream->manager->dnstls_data.cert_cred);
  46         if (r < 0)
  47                 return r;
  48
  49         if (server->dnstls_data.session_data.size > 0) {
  50                 gnutls_session_set_data(gs, server->dnstls_data.session_data.data, server->dnstls_data.session_data.size);
  51
  52                 // Clear old session ticket
  53                 gnutls_free(server->dnstls_data.session_data.data);
  54                 server->dnstls_data.session_data.data = NULL;
  55                 server->dnstls_data.session_data.size = 0;
  56         }
  57
  58         if (server->manager->dns_over_tls_mode == DNS_OVER_TLS_YES) {
  59                 stream->dnstls_data.validation.type = GNUTLS_DT_IP_ADDRESS;
  60                 if (server->family == AF_INET) {
  61                         stream->dnstls_data.validation.data = (unsigned char*) &server->address.in.s_addr;
  62                         stream->dnstls_data.validation.size = 4;
  63                 } else {
  64                         stream->dnstls_data.validation.data = server->address.in6.s6_addr;
  65                         stream->dnstls_data.validation.size = 16;
  66                 }
  67                 gnutls_session_set_verify_cert2(gs, &stream->dnstls_data.validation, 1, 0);
  68         }
  69
  70         if (server->server_name) {
  71                 r = gnutls_server_name_set(gs, GNUTLS_NAME_DNS, server->server_name, strlen(server->server_name));
  72                 if (r < 0)
  73                         return log_debug_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to set server name: %s", gnutls_strerror(r));
  74         }
  75
  76         gnutls_handshake_set_timeout(gs, GNUTLS_DEFAULT_HANDSHAKE_TIMEOUT);
  77
  78         gnutls_transport_set_ptr2(gs, (gnutls_transport_ptr_t) (long) stream->fd, stream);
  79         gnutls_transport_set_vec_push_function(gs, &dnstls_stream_writev);
  80
  81         stream->encrypted = true;
  82         stream->dnstls_data.handshake = gnutls_handshake(gs);
  83         if (stream->dnstls_data.handshake < 0 && gnutls_error_is_fatal(stream->dnstls_data.handshake))
  84                 return -ECONNREFUSED;
  85
  86         stream->dnstls_data.session = TAKE_PTR(gs);
  87
  88         return 0;
  89 }
  90
  91 void dnstls_stream_free(DnsStream *stream) {
  92         assert(stream);
  93         assert(stream->encrypted);
  94
  95         if (stream->dnstls_data.session)
  96                 gnutls_deinit(stream->dnstls_data.session);
  97 }
  98
  99 int dnstls_stream_on_io(DnsStream *stream, uint32_t revents) {
 100         int r;
 101
 102         assert(stream);
 103         assert(stream->encrypted);
 104         assert(stream->dnstls_data.session);
 105
 106         if (stream->dnstls_data.shutdown) {
 107                 r = gnutls_bye(stream->dnstls_data.session, GNUTLS_SHUT_RDWR);
 108                 if (r == GNUTLS_E_AGAIN) {
 109                         stream->dnstls_events = gnutls_record_get_direction(stream->dnstls_data.session) == 1 ? EPOLLOUT : EPOLLIN;
 110                         return -EAGAIN;
 111                 } else if (r < 0)
 112                         log_debug("Failed to invoke gnutls_bye: %s", gnutls_strerror(r));
 113
 114                 stream->dnstls_events = 0;
 115                 stream->dnstls_data.shutdown = false;
 116                 dns_stream_unref(stream);
 117                 return DNSTLS_STREAM_CLOSED;
 118         } else if (stream->dnstls_data.handshake < 0) {
 119                 stream->dnstls_data.handshake = gnutls_handshake(stream->dnstls_data.session);
 120                 if (stream->dnstls_data.handshake == GNUTLS_E_AGAIN) {
 121                         stream->dnstls_events = gnutls_record_get_direction(stream->dnstls_data.session) == 1 ? EPOLLOUT : EPOLLIN;
 122                         return -EAGAIN;
 123                 } else if (stream->dnstls_data.handshake < 0) {
 124                         log_debug("Failed to invoke gnutls_handshake: %s", gnutls_strerror(stream->dnstls_data.handshake));
 125                         if (gnutls_error_is_fatal(stream->dnstls_data.handshake))
 126                                 return -ECONNREFUSED;
 127                 }
 128
 129                 stream->dnstls_events = 0;
 130         }
 131
 132         return 0;
 133 }
 134
 135 int dnstls_stream_shutdown(DnsStream *stream, int error) {
 136         int r;
 137
 138         assert(stream);
 139         assert(stream->encrypted);
 140         assert(stream->dnstls_data.session);
 141
 142         /* Store TLS Ticket for faster successive TLS handshakes */
 143         if (stream->server && stream->server->dnstls_data.session_data.size == 0 && stream->dnstls_data.handshake == GNUTLS_E_SUCCESS)
 144                 gnutls_session_get_data2(stream->dnstls_data.session, &stream->server->dnstls_data.session_data);
 145
 146         if (IN_SET(error, ETIMEDOUT, 0)) {
 147                 r = gnutls_bye(stream->dnstls_data.session, GNUTLS_SHUT_RDWR);
 148                 if (r == GNUTLS_E_AGAIN) {
 149                         if (!stream->dnstls_data.shutdown) {
 150                                 stream->dnstls_data.shutdown = true;
 151                                 dns_stream_ref(stream);
 152                                 return -EAGAIN;
 153                         }
 154                 } else if (r < 0)
 155                         log_debug("Failed to invoke gnutls_bye: %s", gnutls_strerror(r));
 156         }
 157
 158         return 0;
 159 }
 160
 161 ssize_t dnstls_stream_write(DnsStream *stream, const char *buf, size_t count) {
 162         ssize_t ss;
 163
 164         assert(stream);
 165         assert(stream->encrypted);
 166         assert(stream->dnstls_data.session);
 167         assert(buf);
 168
 169         ss = gnutls_record_send(stream->dnstls_data.session, buf, count);
 170         if (ss < 0)
 171                 switch(ss) {
 172                 case GNUTLS_E_INTERRUPTED:
 173                         return -EINTR;
 174                 case GNUTLS_E_AGAIN:
 175                         return -EAGAIN;
 176                 default:
 177                         return log_debug_errno(SYNTHETIC_ERRNO(EPIPE),
 178                                                "Failed to invoke gnutls_record_send: %s",
 179                                                gnutls_strerror(ss));
 180                 }
 181
 182         return ss;
 183 }
 184
 185 ssize_t dnstls_stream_read(DnsStream *stream, void *buf, size_t count) {
 186         ssize_t ss;
 187
 188         assert(stream);
 189         assert(stream->encrypted);
 190         assert(stream->dnstls_data.session);
 191         assert(buf);
 192
 193         ss = gnutls_record_recv(stream->dnstls_data.session, buf, count);
 194         if (ss < 0)
 195                 switch(ss) {
 196                 case GNUTLS_E_INTERRUPTED:
 197                         return -EINTR;
 198                 case GNUTLS_E_AGAIN:
 199                         return -EAGAIN;
 200                 default:
 201                         return log_debug_errno(SYNTHETIC_ERRNO(EPIPE),
 202                                                "Failed to invoke gnutls_record_recv: %s",
 203                                                gnutls_strerror(ss));
 204                 }
 205
 206         return ss;
 207 }
 208
 209 void dnstls_server_free(DnsServer *server) {
 210         assert(server);
 211
 212         if (server->dnstls_data.session_data.data)
 213                 gnutls_free(server->dnstls_data.session_data.data);
 214 }
 215
 216 int dnstls_manager_init(Manager *manager) {
 217         int r;
 218         assert(manager);
 219
 220         r = gnutls_certificate_allocate_credentials(&manager->dnstls_data.cert_cred);
 221         if (r < 0)
 222                 return -ENOMEM;
 223
 224         r = gnutls_certificate_set_x509_system_trust(manager->dnstls_data.cert_cred);
 225         if (r < 0)
 226                 log_warning("Failed to load system trust store: %s", gnutls_strerror(r));
 227
 228         return 0;
 229 }
 230
 231 void dnstls_manager_free(Manager *manager) {
 232         assert(manager);
 233
 234         if (manager->dnstls_data.cert_cred)
 235                 gnutls_certificate_free_credentials(manager->dnstls_data.cert_cred);
 236 }