src/resolve/resolved-dnstls-openssl.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #if !ENABLE_DNS_OVER_TLS || !DNS_OVER_TLS_USE_OPENSSL
   4 #error This source file requires DNS-over-TLS to be enabled and OpenSSL to be available.
   5 #endif
   6
   7 #include "resolved-dnstls.h"
   8 #include "resolved-dns-stream.h"
   9
  10 #include <openssl/bio.h>
  11 #include <openssl/err.h>
  12
  13 DEFINE_TRIVIAL_CLEANUP_FUNC(SSL*, SSL_free);
  14 DEFINE_TRIVIAL_CLEANUP_FUNC(BIO*, BIO_free);
  15
  16 static int dnstls_flush_write_buffer(DnsStream *stream) {
  17         ssize_t ss;
  18
  19         assert(stream);
  20         assert(stream->encrypted);
  21
  22         if (stream->dnstls_data.write_buffer->length > 0) {
  23                 assert(stream->dnstls_data.write_buffer->data);
  24
  25                 struct iovec iov[1];
  26                 iov[0].iov_base = stream->dnstls_data.write_buffer->data;
  27                 iov[0].iov_len = stream->dnstls_data.write_buffer->length;
  28                 ss = dns_stream_writev(stream, iov, 1, DNS_STREAM_WRITE_TLS_DATA);
  29                 if (ss < 0) {
  30                         if (ss == -EAGAIN)
  31                                 stream->dnstls_events |= EPOLLOUT;
  32
  33                         return ss;
  34                 } else {
  35                         stream->dnstls_data.write_buffer->length -= ss;
  36                         stream->dnstls_data.write_buffer->data += ss;
  37
  38                         if (stream->dnstls_data.write_buffer->length > 0) {
  39                                 stream->dnstls_events |= EPOLLOUT;
  40                                 return -EAGAIN;
  41                         }
  42                 }
  43         }
  44
  45         return 0;
  46 }
  47
  48 int dnstls_stream_connect_tls(DnsStream *stream, DnsServer *server) {
  49         _cleanup_(BIO_freep) BIO *rb = NULL, *wb = NULL;
  50         _cleanup_(SSL_freep) SSL *s = NULL;
  51         int error, r;
  52
  53         assert(stream);
  54         assert(server);
  55
  56         rb = BIO_new_socket(stream->fd, 0);
  57         if (!rb)
  58                 return -ENOMEM;
  59
  60         wb = BIO_new(BIO_s_mem());
  61         if (!wb)
  62                 return -ENOMEM;
  63
  64         BIO_get_mem_ptr(wb, &stream->dnstls_data.write_buffer);
  65
  66         s = SSL_new(server->dnstls_data.ctx);
  67         if (!s)
  68                 return -ENOMEM;
  69
  70         SSL_set_connect_state(s);
  71         SSL_set_session(s, server->dnstls_data.session);
  72         SSL_set_bio(s, TAKE_PTR(rb), TAKE_PTR(wb));
  73
  74         ERR_clear_error();
  75         stream->dnstls_data.handshake = SSL_do_handshake(s);
  76         if (stream->dnstls_data.handshake <= 0) {
  77                 error = SSL_get_error(s, stream->dnstls_data.handshake);
  78                 if (!IN_SET(error, SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE)) {
  79                         char errbuf[256];
  80
  81                         ERR_error_string_n(error, errbuf, sizeof(errbuf));
  82                         log_debug("Failed to invoke SSL_do_handshake: %s", errbuf);
  83                         return -ECONNREFUSED;
  84                 }
  85         }
  86
  87         stream->encrypted = true;
  88
  89         r = dnstls_flush_write_buffer(stream);
  90         if (r < 0 && r != -EAGAIN)
  91                 return r;
  92
  93         stream->dnstls_data.ssl = TAKE_PTR(s);
  94
  95         return 0;
  96 }
  97
  98 void dnstls_stream_free(DnsStream *stream) {
  99         assert(stream);
 100         assert(stream->encrypted);
 101
 102         if (stream->dnstls_data.ssl)
 103                 SSL_free(stream->dnstls_data.ssl);
 104 }
 105
 106 int dnstls_stream_on_io(DnsStream *stream, uint32_t revents) {
 107         int error, r;
 108
 109         assert(stream);
 110         assert(stream->encrypted);
 111         assert(stream->dnstls_data.ssl);
 112
 113         /* Flush write buffer when requested by OpenSSL */
 114         if ((revents & EPOLLOUT) && (stream->dnstls_events & EPOLLOUT)) {
 115                 r = dnstls_flush_write_buffer(stream);
 116                 if (r < 0)
 117                         return r;
 118         }
 119
 120         if (stream->dnstls_data.shutdown) {
 121                 ERR_clear_error();
 122                 r = SSL_shutdown(stream->dnstls_data.ssl);
 123                 if (r == 0) {
 124                         stream->dnstls_events = 0;
 125
 126                         r = dnstls_flush_write_buffer(stream);
 127                         if (r < 0)
 128                                 return r;
 129
 130                         return -EAGAIN;
 131                 } else if (r < 0) {
 132                         error = SSL_get_error(stream->dnstls_data.ssl, r);
 133                         if (IN_SET(error, SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE)) {
 134                                 stream->dnstls_events = error == SSL_ERROR_WANT_READ ? EPOLLIN : EPOLLOUT;
 135
 136                                 r = dnstls_flush_write_buffer(stream);
 137                                 if (r < 0)
 138                                         return r;
 139
 140                                 return -EAGAIN;
 141                         } else if (error == SSL_ERROR_SYSCALL) {
 142                                 if (errno > 0)
 143                                         log_debug_errno(errno, "Failed to invoke SSL_shutdown, ignoring: %m");
 144                         } else {
 145                                 char errbuf[256];
 146
 147                                 ERR_error_string_n(error, errbuf, sizeof(errbuf));
 148                                 log_debug("Failed to invoke SSL_shutdown, ignoring: %s", errbuf);
 149                         }
 150                 }
 151
 152                 stream->dnstls_events = 0;
 153                 stream->dnstls_data.shutdown = false;
 154
 155                 r = dnstls_flush_write_buffer(stream);
 156                 if (r < 0)
 157                         return r;
 158
 159                 dns_stream_unref(stream);
 160                 return DNSTLS_STREAM_CLOSED;
 161         } else if (stream->dnstls_data.handshake <= 0) {
 162                 ERR_clear_error();
 163                 stream->dnstls_data.handshake = SSL_do_handshake(stream->dnstls_data.ssl);
 164                 if (stream->dnstls_data.handshake <= 0) {
 165                         error = SSL_get_error(stream->dnstls_data.ssl, stream->dnstls_data.handshake);
 166                         if (IN_SET(error, SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE)) {
 167                                 stream->dnstls_events = error == SSL_ERROR_WANT_READ ? EPOLLIN : EPOLLOUT;
 168                                 r = dnstls_flush_write_buffer(stream);
 169                                 if (r < 0)
 170                                         return r;
 171
 172                                 return -EAGAIN;
 173                         } else {
 174                                 char errbuf[256];
 175
 176                                 ERR_error_string_n(error, errbuf, sizeof(errbuf));
 177                                 log_debug("Failed to invoke SSL_do_handshake: %s", errbuf);
 178                                 return -ECONNREFUSED;
 179                         }
 180                 }
 181
 182                 stream->dnstls_events = 0;
 183                 r = dnstls_flush_write_buffer(stream);
 184                 if (r < 0)
 185                         return r;
 186         }
 187
 188         return 0;
 189 }
 190
 191 int dnstls_stream_shutdown(DnsStream *stream, int error) {
 192         int ssl_error, r;
 193         SSL_SESSION *s;
 194
 195         assert(stream);
 196         assert(stream->encrypted);
 197         assert(stream->dnstls_data.ssl);
 198
 199         if (stream->server) {
 200                 s = SSL_get1_session(stream->dnstls_data.ssl);
 201                 if (s) {
 202                         if (stream->server->dnstls_data.session)
 203                                 SSL_SESSION_free(stream->server->dnstls_data.session);
 204
 205                         stream->server->dnstls_data.session = s;
 206                 }
 207         }
 208
 209         if (error == ETIMEDOUT) {
 210                 ERR_clear_error();
 211                 r = SSL_shutdown(stream->dnstls_data.ssl);
 212                 if (r == 0) {
 213                         if (!stream->dnstls_data.shutdown) {
 214                                 stream->dnstls_data.shutdown = true;
 215                                 dns_stream_ref(stream);
 216                         }
 217
 218                         stream->dnstls_events = 0;
 219
 220                         r = dnstls_flush_write_buffer(stream);
 221                         if (r < 0)
 222                                 return r;
 223
 224                         return -EAGAIN;
 225                 } else if (r < 0) {
 226                         ssl_error = SSL_get_error(stream->dnstls_data.ssl, r);
 227                         if (IN_SET(ssl_error, SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE)) {
 228                                 stream->dnstls_events = ssl_error == SSL_ERROR_WANT_READ ? EPOLLIN : EPOLLOUT;
 229                                 r = dnstls_flush_write_buffer(stream);
 230                                 if (r < 0 && r != -EAGAIN)
 231                                         return r;
 232
 233                                 if (!stream->dnstls_data.shutdown) {
 234                                         stream->dnstls_data.shutdown = true;
 235                                         dns_stream_ref(stream);
 236                                 }
 237                                 return -EAGAIN;
 238                         } else if (ssl_error == SSL_ERROR_SYSCALL) {
 239                                 if (errno > 0)
 240                                         log_debug_errno(errno, "Failed to invoke SSL_shutdown, ignoring: %m");
 241                         } else {
 242                                 char errbuf[256];
 243
 244                                 ERR_error_string_n(ssl_error, errbuf, sizeof(errbuf));
 245                                 log_debug("Failed to invoke SSL_shutdown, ignoring: %s", errbuf);
 246                         }
 247                 }
 248
 249                 stream->dnstls_events = 0;
 250                 r = dnstls_flush_write_buffer(stream);
 251                 if (r < 0)
 252                         return r;
 253         }
 254
 255         return 0;
 256 }
 257
 258 ssize_t dnstls_stream_write(DnsStream *stream, const char *buf, size_t count) {
 259         int error, r;
 260         ssize_t ss;
 261
 262         assert(stream);
 263         assert(stream->encrypted);
 264         assert(stream->dnstls_data.ssl);
 265         assert(buf);
 266
 267         ERR_clear_error();
 268         ss = r = SSL_write(stream->dnstls_data.ssl, buf, count);
 269         if (r <= 0) {
 270                 error = SSL_get_error(stream->dnstls_data.ssl, r);
 271                 if (IN_SET(error, SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE)) {
 272                         stream->dnstls_events = error == SSL_ERROR_WANT_READ ? EPOLLIN : EPOLLOUT;
 273                         ss = -EAGAIN;
 274                 } else if (error == SSL_ERROR_ZERO_RETURN) {
 275                         stream->dnstls_events = 0;
 276                         ss = 0;
 277                 } else {
 278                         char errbuf[256];
 279
 280                         ERR_error_string_n(error, errbuf, sizeof(errbuf));
 281                         log_debug("Failed to invoke SSL_write: %s", errbuf);
 282                         stream->dnstls_events = 0;
 283                         ss = -EPIPE;
 284                 }
 285         } else
 286                 stream->dnstls_events = 0;
 287
 288         r = dnstls_flush_write_buffer(stream);
 289         if (r < 0)
 290                 return r;
 291
 292         return ss;
 293 }
 294
 295 ssize_t dnstls_stream_read(DnsStream *stream, void *buf, size_t count) {
 296         int error, r;
 297         ssize_t ss;
 298
 299         assert(stream);
 300         assert(stream->encrypted);
 301         assert(stream->dnstls_data.ssl);
 302         assert(buf);
 303
 304         ERR_clear_error();
 305         ss = r = SSL_read(stream->dnstls_data.ssl, buf, count);
 306         if (r <= 0) {
 307                 error = SSL_get_error(stream->dnstls_data.ssl, r);
 308                 if (IN_SET(error, SSL_ERROR_WANT_READ, SSL_ERROR_WANT_WRITE)) {
 309                         stream->dnstls_events = error == SSL_ERROR_WANT_READ ? EPOLLIN : EPOLLOUT;
 310                         ss = -EAGAIN;
 311                 } else if (error == SSL_ERROR_ZERO_RETURN) {
 312                         stream->dnstls_events = 0;
 313                         ss = 0;
 314                 } else {
 315                         char errbuf[256];
 316
 317                         ERR_error_string_n(error, errbuf, sizeof(errbuf));
 318                         log_debug("Failed to invoke SSL_read: %s", errbuf);
 319                         stream->dnstls_events = 0;
 320                         ss = -EPIPE;
 321                 }
 322         } else
 323                 stream->dnstls_events = 0;
 324
 325         /* flush write buffer in cache of renegotiation */
 326         r = dnstls_flush_write_buffer(stream);
 327         if (r < 0)
 328                 return r;
 329
 330         return ss;
 331 }
 332
 333 void dnstls_server_init(DnsServer *server) {
 334         assert(server);
 335
 336         server->dnstls_data.ctx = SSL_CTX_new(TLS_client_method());
 337         if (server->dnstls_data.ctx) {
 338                 SSL_CTX_set_min_proto_version(server->dnstls_data.ctx, TLS1_2_VERSION);
 339                 SSL_CTX_set_options(server->dnstls_data.ctx, SSL_OP_NO_COMPRESSION);
 340         }
 341 }
 342
 343 void dnstls_server_free(DnsServer *server) {
 344         assert(server);
 345
 346         if (server->dnstls_data.ctx)
 347                 SSL_CTX_free(server->dnstls_data.ctx);
 348
 349         if (server->dnstls_data.session)
 350                 SSL_SESSION_free(server->dnstls_data.session);
 351 }