src/resolve/resolved-dnstls-gnutls.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #if !ENABLE_DNS_OVER_TLS || !HAVE_GNUTLS
   4 #error This source file requires DNS-over-TLS to be enabled and GnuTLS to be available.
   5 #endif
   6
   7 #include "resolved-dnstls.h"
   8 #include "resolved-dns-stream.h"
   9
  10 #include <gnutls/socket.h>
  11
  12 DEFINE_TRIVIAL_CLEANUP_FUNC(gnutls_session_t, gnutls_deinit);
  13
  14 static ssize_t dnstls_stream_writev(gnutls_transport_ptr_t p, const giovec_t *iov, int iovcnt) {
  15         int r;
  16
  17         assert(p);
  18
  19         r = dns_stream_writev((DnsStream*) p, (const struct iovec*) iov, iovcnt, DNS_STREAM_WRITE_TLS_DATA);
  20         if (r < 0) {
  21                 errno = -r;
  22                 return -1;
  23         }
  24
  25         return r;
  26 }
  27
  28 int dnstls_stream_connect_tls(DnsStream *stream, DnsServer *server) {
  29         _cleanup_(gnutls_deinitp) gnutls_session_t gs;
  30         int r;
  31
  32         assert(stream);
  33         assert(server);
  34
  35         r = gnutls_init(&gs, GNUTLS_CLIENT | GNUTLS_ENABLE_FALSE_START | GNUTLS_NONBLOCK);
  36         if (r < 0)
  37                 return r;
  38
  39         /* As DNS-over-TLS is a recent protocol, older TLS versions can be disabled */
  40         r = gnutls_priority_set_direct(gs, "NORMAL:-VERS-ALL:+VERS-TLS1.2", NULL);
  41         if (r < 0)
  42                 return r;
  43
  44         r = gnutls_credentials_set(gs, GNUTLS_CRD_CERTIFICATE, server->dnstls_data.cert_cred);
  45         if (r < 0)
  46                 return r;
  47
  48         if (server->dnstls_data.session_data.size > 0) {
  49                 gnutls_session_set_data(gs, server->dnstls_data.session_data.data, server->dnstls_data.session_data.size);
  50
  51                 // Clear old session ticket
  52                 gnutls_free(server->dnstls_data.session_data.data);
  53                 server->dnstls_data.session_data.data = NULL;
  54                 server->dnstls_data.session_data.size = 0;
  55         }
  56
  57         gnutls_handshake_set_timeout(gs, GNUTLS_DEFAULT_HANDSHAKE_TIMEOUT);
  58
  59         gnutls_transport_set_ptr2(gs, (gnutls_transport_ptr_t) (long) stream->fd, stream);
  60         gnutls_transport_set_vec_push_function(gs, &dnstls_stream_writev);
  61
  62         stream->encrypted = true;
  63         stream->dnstls_data.handshake = gnutls_handshake(gs);
  64         if (stream->dnstls_data.handshake < 0 && gnutls_error_is_fatal(stream->dnstls_data.handshake))
  65                 return -ECONNREFUSED;
  66
  67         stream->dnstls_data.session = TAKE_PTR(gs);
  68
  69         return 0;
  70 }
  71
  72 void dnstls_stream_free(DnsStream *stream) {
  73         assert(stream);
  74         assert(stream->encrypted);
  75
  76         if (stream->dnstls_data.session)
  77                 gnutls_deinit(stream->dnstls_data.session);
  78 }
  79
  80 int dnstls_stream_on_io(DnsStream *stream) {
  81         int r;
  82
  83         assert(stream);
  84         assert(stream->encrypted);
  85         assert(stream->dnstls_data.session);
  86
  87         if (stream->dnstls_data.shutdown) {
  88                 r = gnutls_bye(stream->dnstls_data.session, GNUTLS_SHUT_RDWR);
  89                 if (r == GNUTLS_E_AGAIN)
  90                         return -EAGAIN;
  91                 else if (r < 0)
  92                         log_debug("Failed to invoke gnutls_bye: %s", gnutls_strerror(r));
  93
  94                 stream->dnstls_data.shutdown = false;
  95                 dns_stream_unref(stream);
  96                 return DNSTLS_STREAM_CLOSED;
  97         } else if (stream->dnstls_data.handshake < 0) {
  98                 stream->dnstls_data.handshake = gnutls_handshake(stream->dnstls_data.session);
  99                 if (stream->dnstls_data.handshake == GNUTLS_E_AGAIN)
 100                         return -EAGAIN;
 101                 else if (stream->dnstls_data.handshake < 0) {
 102                         log_debug("Failed to invoke gnutls_handshake: %s", gnutls_strerror(stream->dnstls_data.handshake));
 103                         if (gnutls_error_is_fatal(stream->dnstls_data.handshake))
 104                                 return -ECONNREFUSED;
 105                 }
 106         }
 107
 108         return 0;
 109 }
 110
 111 int dnstls_stream_shutdown(DnsStream *stream, int error) {
 112         int r;
 113
 114         assert(stream);
 115         assert(stream->encrypted);
 116         assert(stream->dnstls_data.session);
 117
 118         /* Store TLS Ticket for faster succesive TLS handshakes */
 119         if (stream->server && stream->server->dnstls_data.session_data.size == 0 && stream->dnstls_data.handshake == GNUTLS_E_SUCCESS)
 120                 gnutls_session_get_data2(stream->dnstls_data.session, &stream->server->dnstls_data.session_data);
 121
 122         if (IN_SET(error, ETIMEDOUT, 0)) {
 123                 r = gnutls_bye(stream->dnstls_data.session, GNUTLS_SHUT_RDWR);
 124                 if (r == GNUTLS_E_AGAIN) {
 125                         if (!stream->dnstls_data.shutdown) {
 126                                 stream->dnstls_data.shutdown = true;
 127                                 dns_stream_ref(stream);
 128                                 return -EAGAIN;
 129                         }
 130                 } else if (r < 0)
 131                         log_debug("Failed to invoke gnutls_bye: %s", gnutls_strerror(r));
 132         }
 133
 134         return 0;
 135 }
 136
 137 ssize_t dnstls_stream_write(DnsStream *stream, const char *buf, size_t count) {
 138         ssize_t ss;
 139
 140         assert(stream);
 141         assert(stream->encrypted);
 142         assert(stream->dnstls_data.session);
 143         assert(buf);
 144
 145         ss = gnutls_record_send(stream->dnstls_data.session, buf, count);
 146         if (ss < 0)
 147                 switch(ss) {
 148                 case GNUTLS_E_INTERRUPTED:
 149                         return -EINTR;
 150                 case GNUTLS_E_AGAIN:
 151                         return -EAGAIN;
 152                 default:
 153                         log_debug("Failed to invoke gnutls_record_send: %s", gnutls_strerror(ss));
 154                         return -EPIPE;
 155                 }
 156
 157         return ss;
 158 }
 159
 160 ssize_t dnstls_stream_read(DnsStream *stream, void *buf, size_t count) {
 161         ssize_t ss;
 162
 163         assert(stream);
 164         assert(stream->encrypted);
 165         assert(stream->dnstls_data.session);
 166         assert(buf);
 167
 168         ss = gnutls_record_recv(stream->dnstls_data.session, buf, count);
 169         if (ss < 0)
 170                 switch(ss) {
 171                 case GNUTLS_E_INTERRUPTED:
 172                         return -EINTR;
 173                 case GNUTLS_E_AGAIN:
 174                         return -EAGAIN;
 175                 default:
 176                         log_debug("Failed to invoke gnutls_record_recv: %s", gnutls_strerror(ss));
 177                         return -EPIPE;
 178                 }
 179
 180         return ss;
 181 }
 182
 183 void dnstls_server_init(DnsServer *server) {
 184         assert(server);
 185
 186         /* Do not verify cerificate */
 187         gnutls_certificate_allocate_credentials(&server->dnstls_data.cert_cred);
 188 }
 189
 190 void dnstls_server_free(DnsServer *server) {
 191         assert(server);
 192
 193         if (server->dnstls_data.cert_cred)
 194                 gnutls_certificate_free_credentials(server->dnstls_data.cert_cred);
 195
 196         if (server->dnstls_data.session_data.data)
 197                 gnutls_free(server->dnstls_data.session_data.data);
 198 }