- /*
- * Copyright (C) 2004 Red Hat Inc.
- * Copyright (C) 2005 Martin Koegler
- * Copyright (C) 2010 TigerVNC Team
- * Copyright (C) 2010 m-privacy GmbH
- * Copyright (C) 2012-2021 Pierre Ossman for Cendio AB
- *
- * This is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This software is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this software; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
- * USA.
- */
-
- #ifdef HAVE_CONFIG_H
- #include <config.h>
- #endif
-
- #ifndef HAVE_GNUTLS
- #error "This header should not be compiled without HAVE_GNUTLS defined"
- #endif
-
- #include <stdlib.h>
- #ifndef WIN32
- #include <unistd.h>
- #endif
-
- #include <rfb/CSecurityTLS.h>
- #include <rfb/CConnection.h>
- #include <rfb/LogWriter.h>
- #include <rfb/Exception.h>
- #include <rfb/UserMsgBox.h>
- #include <rdr/TLSInStream.h>
- #include <rdr/TLSOutStream.h>
- #include <os/os.h>
-
- #include <gnutls/x509.h>
-
- /*
- * GNUTLS 2.6.5 and older didn't have some variables defined so don't use them.
- * GNUTLS 1.X.X defined LIBGNUTLS_VERSION_NUMBER so treat it as "old" gnutls as
- * well
- */
- #if (defined(GNUTLS_VERSION_NUMBER) && GNUTLS_VERSION_NUMBER < 0x020606) || \
- defined(LIBGNUTLS_VERSION_NUMBER)
- #define WITHOUT_X509_TIMES
- #endif
-
- /* Ancient GNUTLS... */
- #if !defined(GNUTLS_VERSION_NUMBER) && !defined(LIBGNUTLS_VERSION_NUMBER)
- #define WITHOUT_X509_TIMES
- #endif
-
- using namespace rfb;
-
- static const char* homedirfn(const char* fn);
-
- StringParameter CSecurityTLS::X509CA("X509CA", "X509 CA certificate",
- homedirfn("x509_ca.pem"),
- ConfViewer);
- StringParameter CSecurityTLS::X509CRL("X509CRL", "X509 CRL file",
- homedirfn("x509_crl.pem"),
- ConfViewer);
-
- static LogWriter vlog("TLS");
-
- static const char* homedirfn(const char* fn)
- {
- static char full_path[PATH_MAX];
- char* homedir = NULL;
-
- if (getvnchomedir(&homedir) == -1)
- return "";
-
- snprintf(full_path, sizeof(full_path), "%s%s", homedir, fn);
-
- delete [] homedir;
-
- return full_path;
- }
-
- CSecurityTLS::CSecurityTLS(CConnection* cc, bool _anon)
- : CSecurity(cc), session(NULL), anon_cred(NULL), cert_cred(NULL),
- anon(_anon), tlsis(NULL), tlsos(NULL), rawis(NULL), rawos(NULL)
- {
- cafile = X509CA.getData();
- crlfile = X509CRL.getData();
-
- if (gnutls_global_init() != GNUTLS_E_SUCCESS)
- throw AuthFailureException("gnutls_global_init failed");
- }
-
- void CSecurityTLS::shutdown()
- {
- if (session) {
- int ret;
- // FIXME: We can't currently wait for the response, so we only send
- // our close and hope for the best
- ret = gnutls_bye(session, GNUTLS_SHUT_WR);
- if ((ret != GNUTLS_E_SUCCESS) && (ret != GNUTLS_E_INVALID_SESSION))
- vlog.error("TLS shutdown failed: %s", gnutls_strerror(ret));
- }
-
- if (anon_cred) {
- gnutls_anon_free_client_credentials(anon_cred);
- anon_cred = 0;
- }
-
- if (cert_cred) {
- gnutls_certificate_free_credentials(cert_cred);
- cert_cred = 0;
- }
-
- if (rawis && rawos) {
- cc->setStreams(rawis, rawos);
- rawis = NULL;
- rawos = NULL;
- }
-
- if (tlsis) {
- delete tlsis;
- tlsis = NULL;
- }
- if (tlsos) {
- delete tlsos;
- tlsos = NULL;
- }
-
- if (session) {
- gnutls_deinit(session);
- session = 0;
- }
- }
-
-
- CSecurityTLS::~CSecurityTLS()
- {
- shutdown();
-
- delete[] cafile;
- delete[] crlfile;
-
- gnutls_global_deinit();
- }
-
- bool CSecurityTLS::processMsg()
- {
- rdr::InStream* is = cc->getInStream();
- rdr::OutStream* os = cc->getOutStream();
- client = cc;
-
- if (!session) {
- if (!is->hasData(1))
- return false;
-
- if (is->readU8() == 0)
- throw AuthFailureException("Server failed to initialize TLS session");
-
- if (gnutls_init(&session, GNUTLS_CLIENT) != GNUTLS_E_SUCCESS)
- throw AuthFailureException("gnutls_init failed");
-
- if (gnutls_set_default_priority(session) != GNUTLS_E_SUCCESS)
- throw AuthFailureException("gnutls_set_default_priority failed");
-
- setParam();
-
- // Create these early as they set up the push/pull functions
- // for GnuTLS
- tlsis = new rdr::TLSInStream(is, session);
- tlsos = new rdr::TLSOutStream(os, session);
-
- rawis = is;
- rawos = os;
- }
-
- int err;
- err = gnutls_handshake(session);
- if (err != GNUTLS_E_SUCCESS) {
- if (!gnutls_error_is_fatal(err)) {
- vlog.debug("Deferring completion of TLS handshake: %s", gnutls_strerror(err));
- return false;
- }
-
- vlog.error("TLS Handshake failed: %s\n", gnutls_strerror (err));
- shutdown();
- throw AuthFailureException("TLS Handshake failed");
- }
-
- vlog.debug("TLS handshake completed with %s",
- gnutls_session_get_desc(session));
-
- checkSession();
-
- cc->setStreams(tlsis, tlsos);
-
- return true;
- }
-
- void CSecurityTLS::setParam()
- {
- static const char kx_anon_priority[] = ":+ANON-ECDH:+ANON-DH";
-
- int ret;
-
- // Custom priority string specified?
- if (strcmp(Security::GnuTLSPriority, "") != 0) {
- char *prio;
- const char *err;
-
- prio = (char*)malloc(strlen(Security::GnuTLSPriority) +
- strlen(kx_anon_priority) + 1);
- if (prio == NULL)
- throw AuthFailureException("Not enough memory for GnuTLS priority string");
-
- strcpy(prio, Security::GnuTLSPriority);
- if (anon)
- strcat(prio, kx_anon_priority);
-
- ret = gnutls_priority_set_direct(session, prio, &err);
-
- free(prio);
-
- if (ret != GNUTLS_E_SUCCESS) {
- if (ret == GNUTLS_E_INVALID_REQUEST)
- vlog.error("GnuTLS priority syntax error at: %s", err);
- throw AuthFailureException("gnutls_set_priority_direct failed");
- }
- } else if (anon) {
- const char *err;
-
- #if GNUTLS_VERSION_NUMBER >= 0x030603
- // gnutls_set_default_priority_appends() expects a normal priority string that
- // doesn't start with ":".
- ret = gnutls_set_default_priority_append(session, kx_anon_priority + 1, &err, 0);
- if (ret != GNUTLS_E_SUCCESS) {
- if (ret == GNUTLS_E_INVALID_REQUEST)
- vlog.error("GnuTLS priority syntax error at: %s", err);
- throw AuthFailureException("gnutls_set_default_priority_append failed");
- }
- #else
- // We don't know what the system default priority is, so we guess
- // it's what upstream GnuTLS has
- static const char gnutls_default_priority[] = "NORMAL";
- char *prio;
-
- prio = (char*)malloc(strlen(gnutls_default_priority) +
- strlen(kx_anon_priority) + 1);
- if (prio == NULL)
- throw AuthFailureException("Not enough memory for GnuTLS priority string");
-
- strcpy(prio, gnutls_default_priority);
- strcat(prio, kx_anon_priority);
-
- ret = gnutls_priority_set_direct(session, prio, &err);
-
- free(prio);
-
- if (ret != GNUTLS_E_SUCCESS) {
- if (ret == GNUTLS_E_INVALID_REQUEST)
- vlog.error("GnuTLS priority syntax error at: %s", err);
- throw AuthFailureException("gnutls_set_priority_direct failed");
- }
- #endif
- }
-
- if (anon) {
- if (gnutls_anon_allocate_client_credentials(&anon_cred) != GNUTLS_E_SUCCESS)
- throw AuthFailureException("gnutls_anon_allocate_client_credentials failed");
-
- if (gnutls_credentials_set(session, GNUTLS_CRD_ANON, anon_cred) != GNUTLS_E_SUCCESS)
- throw AuthFailureException("gnutls_credentials_set failed");
-
- vlog.debug("Anonymous session has been set");
- } else {
- if (gnutls_certificate_allocate_credentials(&cert_cred) != GNUTLS_E_SUCCESS)
- throw AuthFailureException("gnutls_certificate_allocate_credentials failed");
-
- if (gnutls_certificate_set_x509_system_trust(cert_cred) < 1)
- vlog.error("Could not load system certificate trust store");
-
- if (*cafile && gnutls_certificate_set_x509_trust_file(cert_cred,cafile,GNUTLS_X509_FMT_PEM) < 0)
- vlog.error("Could not load user specified certificate authority");
-
- if (*crlfile && gnutls_certificate_set_x509_crl_file(cert_cred,crlfile,GNUTLS_X509_FMT_PEM) < 0)
- vlog.error("Could not load user specified certificate revocation list");
-
- if (gnutls_credentials_set(session, GNUTLS_CRD_CERTIFICATE, cert_cred) != GNUTLS_E_SUCCESS)
- throw AuthFailureException("gnutls_credentials_set failed");
-
- if (gnutls_server_name_set(session, GNUTLS_NAME_DNS,
- client->getServerName(),
- strlen(client->getServerName())) != GNUTLS_E_SUCCESS)
- vlog.error("Failed to configure the server name for TLS handshake");
-
- vlog.debug("X509 session has been set");
- }
- }
-
- void CSecurityTLS::checkSession()
- {
- const unsigned allowed_errors = GNUTLS_CERT_INVALID |
- GNUTLS_CERT_SIGNER_NOT_FOUND |
- GNUTLS_CERT_SIGNER_NOT_CA;
- unsigned int status;
- const gnutls_datum_t *cert_list;
- unsigned int cert_list_size = 0;
- int err;
-
- char *homeDir;
- gnutls_datum_t info;
- size_t len;
-
- if (anon)
- return;
-
- if (gnutls_certificate_type_get(session) != GNUTLS_CRT_X509)
- throw AuthFailureException("unsupported certificate type");
-
- err = gnutls_certificate_verify_peers2(session, &status);
- if (err != 0) {
- vlog.error("server certificate verification failed: %s", gnutls_strerror(err));
- throw AuthFailureException("server certificate verification failed");
- }
-
- if (status & GNUTLS_CERT_REVOKED)
- throw AuthFailureException("server certificate has been revoked");
-
- #ifndef WITHOUT_X509_TIMES
- if (status & GNUTLS_CERT_NOT_ACTIVATED)
- throw AuthFailureException("server certificate has not been activated");
-
- if (status & GNUTLS_CERT_EXPIRED) {
- vlog.debug("server certificate has expired");
- if (!msg->showMsgBox(UserMsgBox::M_YESNO, "certificate has expired",
- "The certificate of the server has expired, "
- "do you want to continue?"))
- throw AuthFailureException("server certificate has expired");
- }
- #endif
- /* Process other errors later */
-
- cert_list = gnutls_certificate_get_peers(session, &cert_list_size);
- if (!cert_list_size)
- throw AuthFailureException("empty certificate chain");
-
- /* Process only server's certificate, not issuer's certificate */
- gnutls_x509_crt_t crt;
- gnutls_x509_crt_init(&crt);
-
- if (gnutls_x509_crt_import(crt, &cert_list[0], GNUTLS_X509_FMT_DER) < 0)
- throw AuthFailureException("decoding of certificate failed");
-
- if (gnutls_x509_crt_check_hostname(crt, client->getServerName()) == 0) {
- CharArray text;
- vlog.debug("hostname mismatch");
- text.format("Hostname (%s) does not match the server certificate, "
- "do you want to continue?", client->getServerName());
- if (!msg->showMsgBox(UserMsgBox::M_YESNO,
- "Certificate hostname mismatch", text.buf))
- throw AuthFailureException("Certificate hostname mismatch");
- }
-
- if (status == 0) {
- /* Everything is fine (hostname + verification) */
- gnutls_x509_crt_deinit(crt);
- return;
- }
-
- if (status & GNUTLS_CERT_INVALID)
- vlog.debug("server certificate invalid");
- if (status & GNUTLS_CERT_SIGNER_NOT_FOUND)
- vlog.debug("server cert signer not found");
- if (status & GNUTLS_CERT_SIGNER_NOT_CA)
- vlog.debug("server cert signer not CA");
-
- if (status & GNUTLS_CERT_INSECURE_ALGORITHM)
- throw AuthFailureException("The server certificate uses an insecure algorithm");
-
- if ((status & (~allowed_errors)) != 0) {
- /* No other errors are allowed */
- vlog.debug("GNUTLS status of certificate verification: %u", status);
- throw AuthFailureException("Invalid status of server certificate verification");
- }
-
- /* Certificate is fine, except we don't know the issuer, so TOFU time */
-
- homeDir = NULL;
- if (getvnchomedir(&homeDir) == -1) {
- throw AuthFailureException("Could not obtain VNC home directory "
- "path for known hosts storage");
- }
-
- CharArray dbPath(strlen(homeDir) + 16 + 1);
- sprintf(dbPath.buf, "%sx509_known_hosts", homeDir);
- delete [] homeDir;
-
- err = gnutls_verify_stored_pubkey(dbPath.buf, NULL,
- client->getServerName(), NULL,
- GNUTLS_CRT_X509, &cert_list[0], 0);
-
- /* Previously known? */
- if (err == GNUTLS_E_SUCCESS) {
- vlog.debug("Server certificate found in known hosts file");
- gnutls_x509_crt_deinit(crt);
- return;
- }
-
- if ((err != GNUTLS_E_NO_CERTIFICATE_FOUND) &&
- (err != GNUTLS_E_CERTIFICATE_KEY_MISMATCH)) {
- throw AuthFailureException("Could not load known hosts database");
- }
-
- if (gnutls_x509_crt_print(crt, GNUTLS_CRT_PRINT_ONELINE, &info))
- throw AuthFailureException("Could not find certificate to display");
-
- len = strlen((char*)info.data);
- for (size_t i = 0; i < len - 1; i++) {
- if (info.data[i] == ',' && info.data[i + 1] == ' ')
- info.data[i] = '\n';
- }
-
- /* New host */
- if (err == GNUTLS_E_NO_CERTIFICATE_FOUND) {
- CharArray text;
-
- vlog.debug("Server host not previously known");
- vlog.debug("%s", info.data);
-
- text.format("This certificate has been signed by an unknown "
- "authority:\n\n%s\n\nSomeone could be trying to "
- "impersonate the site and you should not "
- "continue.\n\nDo you want to make an exception "
- "for this server?", info.data);
-
- if (!msg->showMsgBox(UserMsgBox::M_YESNO,
- "Unknown certificate issuer",
- text.buf))
- throw AuthFailureException("Unknown certificate issuer");
- } else if (err == GNUTLS_E_CERTIFICATE_KEY_MISMATCH) {
- CharArray text;
-
- vlog.debug("Server host key mismatch");
- vlog.debug("%s", info.data);
-
- text.format("This host is previously known with a different "
- "certificate, and the new certificate has been "
- "signed by an unknown authority:\n\n%s\n\nSomeone "
- "could be trying to impersonate the site and you "
- "should not continue.\n\nDo you want to make an "
- "exception for this server?", info.data);
-
- if (!msg->showMsgBox(UserMsgBox::M_YESNO,
- "Unexpected server certificate",
- text.buf))
- throw AuthFailureException("Unexpected server certificate");
- }
-
- if (gnutls_store_pubkey(dbPath.buf, NULL, client->getServerName(),
- NULL, GNUTLS_CRT_X509, &cert_list[0], 0, 0))
- vlog.error("Failed to store server certificate to known hosts database");
-
- gnutls_x509_crt_deinit(crt);
- /*
- * GNUTLS doesn't correctly export gnutls_free symbol which is
- * a function pointer. Linking with Visual Studio 2008 Express will
- * fail when you call gnutls_free().
- */
- #if WIN32
- free(info.data);
- #else
- gnutls_free(info.data);
- #endif
- }
-
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