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