vnc-tls.c

   1 /*
   2  * QEMU VNC display driver: TLS helpers
   3  *
   4  * Copyright (C) 2006 Anthony Liguori <anthony@codemonkey.ws>
   5  * Copyright (C) 2006 Fabrice Bellard
   6  * Copyright (C) 2009 Red Hat, Inc
   7  *
   8  * Permission is hereby granted, free of charge, to any person obtaining a copy
   9  * of this software and associated documentation files (the "Software"), to deal
  10  * in the Software without restriction, including without limitation the rights
  11  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  12  * copies of the Software, and to permit persons to whom the Software is
  13  * furnished to do so, subject to the following conditions:
  14  *
  15  * The above copyright notice and this permission notice shall be included in
  16  * all copies or substantial portions of the Software.
  17  *
  18  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  19  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  20  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  21  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  22  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  23  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  24  * THE SOFTWARE.
  25  */
  26
  27 #include "vnc.h"
  28 #include "qemu_socket.h"
  29
  30 #if defined(_VNC_DEBUG) && _VNC_DEBUG >= 2
  31 /* Very verbose, so only enabled for _VNC_DEBUG >= 2 */
  32 static void vnc_debug_gnutls_log(int level, const char* str) {
  33     VNC_DEBUG("%d %s", level, str);
  34 }
  35 #endif /* defined(_VNC_DEBUG) && _VNC_DEBUG >= 2 */
  36
  37
  38 #define DH_BITS 1024
  39 static gnutls_dh_params_t dh_params;
  40
  41 static int vnc_tls_initialize(void)
  42 {
  43     static int tlsinitialized = 0;
  44
  45     if (tlsinitialized)
  46         return 1;
  47
  48     if (gnutls_global_init () < 0)
  49         return 0;
  50
  51     /* XXX ought to re-generate diffie-hellmen params periodically */
  52     if (gnutls_dh_params_init (&dh_params) < 0)
  53         return 0;
  54     if (gnutls_dh_params_generate2 (dh_params, DH_BITS) < 0)
  55         return 0;
  56
  57 #if defined(_VNC_DEBUG) && _VNC_DEBUG >= 2
  58     gnutls_global_set_log_level(10);
  59     gnutls_global_set_log_function(vnc_debug_gnutls_log);
  60 #endif
  61
  62     tlsinitialized = 1;
  63
  64     return 1;
  65 }
  66
  67 static ssize_t vnc_tls_push(gnutls_transport_ptr_t transport,
  68                             const void *data,
  69                             size_t len) {
  70     struct VncState *vs = (struct VncState *)transport;
  71     int ret;
  72
  73  retry:
  74     ret = send(vs->csock, data, len, 0);
  75     if (ret < 0) {
  76         if (errno == EINTR)
  77             goto retry;
  78         return -1;
  79     }
  80     return ret;
  81 }
  82
  83
  84 static ssize_t vnc_tls_pull(gnutls_transport_ptr_t transport,
  85                             void *data,
  86                             size_t len) {
  87     struct VncState *vs = (struct VncState *)transport;
  88     int ret;
  89
  90  retry:
  91     ret = recv(vs->csock, data, len, 0);
  92     if (ret < 0) {
  93         if (errno == EINTR)
  94             goto retry;
  95         return -1;
  96     }
  97     return ret;
  98 }
  99
 100
 101 static gnutls_anon_server_credentials vnc_tls_initialize_anon_cred(void)
 102 {
 103     gnutls_anon_server_credentials anon_cred;
 104     int ret;
 105
 106     if ((ret = gnutls_anon_allocate_server_credentials(&anon_cred)) < 0) {
 107         VNC_DEBUG("Cannot allocate credentials %s\n", gnutls_strerror(ret));
 108         return NULL;
 109     }
 110
 111     gnutls_anon_set_server_dh_params(anon_cred, dh_params);
 112
 113     return anon_cred;
 114 }
 115
 116
 117 static gnutls_certificate_credentials_t vnc_tls_initialize_x509_cred(VncDisplay *vd)
 118 {
 119     gnutls_certificate_credentials_t x509_cred;
 120     int ret;
 121
 122     if (!vd->tls.x509cacert) {
 123         VNC_DEBUG("No CA x509 certificate specified\n");
 124         return NULL;
 125     }
 126     if (!vd->tls.x509cert) {
 127         VNC_DEBUG("No server x509 certificate specified\n");
 128         return NULL;
 129     }
 130     if (!vd->tls.x509key) {
 131         VNC_DEBUG("No server private key specified\n");
 132         return NULL;
 133     }
 134
 135     if ((ret = gnutls_certificate_allocate_credentials(&x509_cred)) < 0) {
 136         VNC_DEBUG("Cannot allocate credentials %s\n", gnutls_strerror(ret));
 137         return NULL;
 138     }
 139     if ((ret = gnutls_certificate_set_x509_trust_file(x509_cred,
 140                                                       vd->tls.x509cacert,
 141                                                       GNUTLS_X509_FMT_PEM)) < 0) {
 142         VNC_DEBUG("Cannot load CA certificate %s\n", gnutls_strerror(ret));
 143         gnutls_certificate_free_credentials(x509_cred);
 144         return NULL;
 145     }
 146
 147     if ((ret = gnutls_certificate_set_x509_key_file (x509_cred,
 148                                                      vd->tls.x509cert,
 149                                                      vd->tls.x509key,
 150                                                      GNUTLS_X509_FMT_PEM)) < 0) {
 151         VNC_DEBUG("Cannot load certificate & key %s\n", gnutls_strerror(ret));
 152         gnutls_certificate_free_credentials(x509_cred);
 153         return NULL;
 154     }
 155
 156     if (vd->tls.x509cacrl) {
 157         if ((ret = gnutls_certificate_set_x509_crl_file(x509_cred,
 158                                                         vd->tls.x509cacrl,
 159                                                         GNUTLS_X509_FMT_PEM)) < 0) {
 160             VNC_DEBUG("Cannot load CRL %s\n", gnutls_strerror(ret));
 161             gnutls_certificate_free_credentials(x509_cred);
 162             return NULL;
 163         }
 164     }
 165
 166     gnutls_certificate_set_dh_params (x509_cred, dh_params);
 167
 168     return x509_cred;
 169 }
 170
 171
 172 int vnc_tls_validate_certificate(struct VncState *vs)
 173 {
 174     int ret;
 175     unsigned int status;
 176     const gnutls_datum_t *certs;
 177     unsigned int nCerts, i;
 178     time_t now;
 179
 180     VNC_DEBUG("Validating client certificate\n");
 181     if ((ret = gnutls_certificate_verify_peers2 (vs->tls.session, &status)) < 0) {
 182         VNC_DEBUG("Verify failed %s\n", gnutls_strerror(ret));
 183         return -1;
 184     }
 185
 186     if ((now = time(NULL)) == ((time_t)-1)) {
 187         return -1;
 188     }
 189
 190     if (status != 0) {
 191         if (status & GNUTLS_CERT_INVALID)
 192             VNC_DEBUG("The certificate is not trusted.\n");
 193
 194         if (status & GNUTLS_CERT_SIGNER_NOT_FOUND)
 195             VNC_DEBUG("The certificate hasn't got a known issuer.\n");
 196
 197         if (status & GNUTLS_CERT_REVOKED)
 198             VNC_DEBUG("The certificate has been revoked.\n");
 199
 200         if (status & GNUTLS_CERT_INSECURE_ALGORITHM)
 201             VNC_DEBUG("The certificate uses an insecure algorithm\n");
 202
 203         return -1;
 204     } else {
 205         VNC_DEBUG("Certificate is valid!\n");
 206     }
 207
 208     /* Only support x509 for now */
 209     if (gnutls_certificate_type_get(vs->tls.session) != GNUTLS_CRT_X509)
 210         return -1;
 211
 212     if (!(certs = gnutls_certificate_get_peers(vs->tls.session, &nCerts)))
 213         return -1;
 214
 215     for (i = 0 ; i < nCerts ; i++) {
 216         gnutls_x509_crt_t cert;
 217         VNC_DEBUG ("Checking certificate chain %d\n", i);
 218         if (gnutls_x509_crt_init (&cert) < 0)
 219             return -1;
 220
 221         if (gnutls_x509_crt_import(cert, &certs[i], GNUTLS_X509_FMT_DER) < 0) {
 222             gnutls_x509_crt_deinit (cert);
 223             return -1;
 224         }
 225
 226         if (gnutls_x509_crt_get_expiration_time (cert) < now) {
 227             VNC_DEBUG("The certificate has expired\n");
 228             gnutls_x509_crt_deinit (cert);
 229             return -1;
 230         }
 231
 232         if (gnutls_x509_crt_get_activation_time (cert) > now) {
 233             VNC_DEBUG("The certificate is not yet activated\n");
 234             gnutls_x509_crt_deinit (cert);
 235             return -1;
 236         }
 237
 238         if (gnutls_x509_crt_get_activation_time (cert) > now) {
 239             VNC_DEBUG("The certificate is not yet activated\n");
 240             gnutls_x509_crt_deinit (cert);
 241             return -1;
 242         }
 243
 244         if (i == 0) {
 245             size_t dnameSize = 1024;
 246             vs->tls.dname = qemu_malloc(dnameSize);
 247         requery:
 248             if ((ret = gnutls_x509_crt_get_dn (cert, vs->tls.dname, &dnameSize)) != 0) {
 249                 if (ret == GNUTLS_E_SHORT_MEMORY_BUFFER) {
 250                     vs->tls.dname = qemu_realloc(vs->tls.dname, dnameSize);
 251                     goto requery;
 252                 }
 253                 gnutls_x509_crt_deinit (cert);
 254                 VNC_DEBUG("Cannot get client distinguished name: %s",
 255                           gnutls_strerror (ret));
 256                 return -1;
 257             }
 258
 259             if (vs->vd->tls.x509verify) {
 260                 int allow;
 261                 if (!vs->vd->tls.acl) {
 262                     VNC_DEBUG("no ACL activated, allowing access");
 263                     gnutls_x509_crt_deinit (cert);
 264                     continue;
 265                 }
 266
 267                 allow = qemu_acl_party_is_allowed(vs->vd->tls.acl,
 268                                                   vs->tls.dname);
 269
 270                 VNC_DEBUG("TLS x509 ACL check for %s is %s\n",
 271                           vs->tls.dname, allow ? "allowed" : "denied");
 272                 if (!allow) {
 273                     gnutls_x509_crt_deinit (cert);
 274                     return -1;
 275                 }
 276             }
 277         }
 278
 279         gnutls_x509_crt_deinit (cert);
 280     }
 281
 282     return 0;
 283 }
 284
 285
 286 int vnc_tls_client_setup(struct VncState *vs,
 287                          int needX509Creds) {
 288     static const int cert_type_priority[] = { GNUTLS_CRT_X509, 0 };
 289     static const int protocol_priority[]= { GNUTLS_TLS1_1, GNUTLS_TLS1_0, GNUTLS_SSL3, 0 };
 290     static const int kx_anon[] = {GNUTLS_KX_ANON_DH, 0};
 291     static const int kx_x509[] = {GNUTLS_KX_DHE_DSS, GNUTLS_KX_RSA, GNUTLS_KX_DHE_RSA, GNUTLS_KX_SRP, 0};
 292
 293     VNC_DEBUG("Do TLS setup\n");
 294     if (vnc_tls_initialize() < 0) {
 295         VNC_DEBUG("Failed to init TLS\n");
 296         vnc_client_error(vs);
 297         return -1;
 298     }
 299     if (vs->tls.session == NULL) {
 300         if (gnutls_init(&vs->tls.session, GNUTLS_SERVER) < 0) {
 301             vnc_client_error(vs);
 302             return -1;
 303         }
 304
 305         if (gnutls_set_default_priority(vs->tls.session) < 0) {
 306             gnutls_deinit(vs->tls.session);
 307             vs->tls.session = NULL;
 308             vnc_client_error(vs);
 309             return -1;
 310         }
 311
 312         if (gnutls_kx_set_priority(vs->tls.session, needX509Creds ? kx_x509 : kx_anon) < 0) {
 313             gnutls_deinit(vs->tls.session);
 314             vs->tls.session = NULL;
 315             vnc_client_error(vs);
 316             return -1;
 317         }
 318
 319         if (gnutls_certificate_type_set_priority(vs->tls.session, cert_type_priority) < 0) {
 320             gnutls_deinit(vs->tls.session);
 321             vs->tls.session = NULL;
 322             vnc_client_error(vs);
 323             return -1;
 324         }
 325
 326         if (gnutls_protocol_set_priority(vs->tls.session, protocol_priority) < 0) {
 327             gnutls_deinit(vs->tls.session);
 328             vs->tls.session = NULL;
 329             vnc_client_error(vs);
 330             return -1;
 331         }
 332
 333         if (needX509Creds) {
 334             gnutls_certificate_server_credentials x509_cred = vnc_tls_initialize_x509_cred(vs->vd);
 335             if (!x509_cred) {
 336                 gnutls_deinit(vs->tls.session);
 337                 vs->tls.session = NULL;
 338                 vnc_client_error(vs);
 339                 return -1;
 340             }
 341             if (gnutls_credentials_set(vs->tls.session, GNUTLS_CRD_CERTIFICATE, x509_cred) < 0) {
 342                 gnutls_deinit(vs->tls.session);
 343                 vs->tls.session = NULL;
 344                 gnutls_certificate_free_credentials(x509_cred);
 345                 vnc_client_error(vs);
 346                 return -1;
 347             }
 348             if (vs->vd->tls.x509verify) {
 349                 VNC_DEBUG("Requesting a client certificate\n");
 350                 gnutls_certificate_server_set_request (vs->tls.session, GNUTLS_CERT_REQUEST);
 351             }
 352
 353         } else {
 354             gnutls_anon_server_credentials anon_cred = vnc_tls_initialize_anon_cred();
 355             if (!anon_cred) {
 356                 gnutls_deinit(vs->tls.session);
 357                 vs->tls.session = NULL;
 358                 vnc_client_error(vs);
 359                 return -1;
 360             }
 361             if (gnutls_credentials_set(vs->tls.session, GNUTLS_CRD_ANON, anon_cred) < 0) {
 362                 gnutls_deinit(vs->tls.session);
 363                 vs->tls.session = NULL;
 364                 gnutls_anon_free_server_credentials(anon_cred);
 365                 vnc_client_error(vs);
 366                 return -1;
 367             }
 368         }
 369
 370         gnutls_transport_set_ptr(vs->tls.session, (gnutls_transport_ptr_t)vs);
 371         gnutls_transport_set_push_function(vs->tls.session, vnc_tls_push);
 372         gnutls_transport_set_pull_function(vs->tls.session, vnc_tls_pull);
 373     }
 374     return 0;
 375 }
 376
 377
 378 void vnc_tls_client_cleanup(struct VncState *vs)
 379 {
 380     if (vs->tls.session) {
 381         gnutls_deinit(vs->tls.session);
 382         vs->tls.session = NULL;
 383     }
 384     vs->tls.wiremode = VNC_WIREMODE_CLEAR;
 385     free(vs->tls.dname);
 386 }
 387
 388
 389
 390 static int vnc_set_x509_credential(VncDisplay *vd,
 391                                    const char *certdir,
 392                                    const char *filename,
 393                                    char **cred,
 394                                    int ignoreMissing)
 395 {
 396     struct stat sb;
 397
 398     if (*cred) {
 399         qemu_free(*cred);
 400         *cred = NULL;
 401     }
 402
 403     *cred = qemu_malloc(strlen(certdir) + strlen(filename) + 2);
 404
 405     strcpy(*cred, certdir);
 406     strcat(*cred, "/");
 407     strcat(*cred, filename);
 408
 409     VNC_DEBUG("Check %s\n", *cred);
 410     if (stat(*cred, &sb) < 0) {
 411         qemu_free(*cred);
 412         *cred = NULL;
 413         if (ignoreMissing && errno == ENOENT)
 414             return 0;
 415         return -1;
 416     }
 417
 418     return 0;
 419 }
 420
 421
 422 #define X509_CA_CERT_FILE "ca-cert.pem"
 423 #define X509_CA_CRL_FILE "ca-crl.pem"
 424 #define X509_SERVER_KEY_FILE "server-key.pem"
 425 #define X509_SERVER_CERT_FILE "server-cert.pem"
 426
 427
 428 int vnc_tls_set_x509_creds_dir(VncDisplay *vd,
 429                                const char *certdir)
 430 {
 431     if (vnc_set_x509_credential(vd, certdir, X509_CA_CERT_FILE, &vd->tls.x509cacert, 0) < 0)
 432         goto cleanup;
 433     if (vnc_set_x509_credential(vd, certdir, X509_CA_CRL_FILE, &vd->tls.x509cacrl, 1) < 0)
 434         goto cleanup;
 435     if (vnc_set_x509_credential(vd, certdir, X509_SERVER_CERT_FILE, &vd->tls.x509cert, 0) < 0)
 436         goto cleanup;
 437     if (vnc_set_x509_credential(vd, certdir, X509_SERVER_KEY_FILE, &vd->tls.x509key, 0) < 0)
 438         goto cleanup;
 439
 440     return 0;
 441
 442  cleanup:
 443     qemu_free(vd->tls.x509cacert);
 444     qemu_free(vd->tls.x509cacrl);
 445     qemu_free(vd->tls.x509cert);
 446     qemu_free(vd->tls.x509key);
 447     vd->tls.x509cacert = vd->tls.x509cacrl = vd->tls.x509cert = vd->tls.x509key = NULL;
 448     return -1;
 449 }
 450