Shared TDE VNC library sources
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libtdevnc/libvncclient/tls_gnutls.c

651 lines
18 KiB

/*
* Copyright (C) 2009 Vic Lee.
*
* 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.
*/
#include <gnutls/gnutls.h>
#include <gnutls/x509.h>
#include <rfb/rfbclient.h>
#include <errno.h>
#ifdef WIN32
#undef SOCKET
#include <windows.h> /* for Sleep() */
#define sleep(X) Sleep(1000*X) /* MinGW32 has no sleep() */
#include <winsock2.h>
#define read(sock,buf,len) recv(sock,buf,len,0)
#define write(sock,buf,len) send(sock,buf,len,0)
#endif
#include "tls.h"
static const char *rfbTLSPriority = "NORMAL:+DHE-DSS:+RSA:+DHE-RSA:+SRP";
static const char *rfbAnonTLSPriority= "NORMAL:+ANON-DH";
#define DH_BITS 1024
static gnutls_dh_params_t rfbDHParams;
static rfbBool rfbTLSInitialized = FALSE;
static int
verify_certificate_callback (gnutls_session_t session)
{
unsigned int status;
const gnutls_datum_t *cert_list;
unsigned int cert_list_size;
int ret;
gnutls_x509_crt_t cert;
rfbClient *sptr;
char *hostname;
sptr = (rfbClient *)gnutls_session_get_ptr(session);
if (!sptr) {
rfbClientLog("Failed to validate certificate - missing client data\n");
return GNUTLS_E_CERTIFICATE_ERROR;
}
hostname = sptr->serverHost;
if (!hostname) {
rfbClientLog("No server hostname found for client\n");
return GNUTLS_E_CERTIFICATE_ERROR;
}
/* This verification function uses the trusted CAs in the credentials
* structure. So you must have installed one or more CA certificates.
*/
ret = gnutls_certificate_verify_peers2 (session, &status);
if (ret < 0)
{
rfbClientLog ("Certificate validation call failed\n");
return GNUTLS_E_CERTIFICATE_ERROR;
}
if (status & GNUTLS_CERT_INVALID)
rfbClientLog("The certificate is not trusted.\n");
if (status & GNUTLS_CERT_SIGNER_NOT_FOUND)
rfbClientLog("The certificate hasn't got a known issuer.\n");
if (status & GNUTLS_CERT_REVOKED)
rfbClientLog("The certificate has been revoked.\n");
if (status & GNUTLS_CERT_EXPIRED)
rfbClientLog("The certificate has expired\n");
if (status & GNUTLS_CERT_NOT_ACTIVATED)
rfbClientLog("The certificate is not yet activated\n");
if (status)
return GNUTLS_E_CERTIFICATE_ERROR;
/* Up to here the process is the same for X.509 certificates and
* OpenPGP keys. From now on X.509 certificates are assumed. This can
* be easily extended to work with openpgp keys as well.
*/
if (gnutls_certificate_type_get (session) != GNUTLS_CRT_X509) {
rfbClientLog("The certificate was not X509\n");
return GNUTLS_E_CERTIFICATE_ERROR;
}
if (gnutls_x509_crt_init (&cert) < 0)
{
rfbClientLog("Error initialising certificate structure\n");
return GNUTLS_E_CERTIFICATE_ERROR;
}
cert_list = gnutls_certificate_get_peers (session, &cert_list_size);
if (cert_list == NULL)
{
rfbClientLog("No certificate was found!\n");
return GNUTLS_E_CERTIFICATE_ERROR;
}
if (gnutls_x509_crt_import (cert, &cert_list[0], GNUTLS_X509_FMT_DER) < 0)
{
rfbClientLog("Error parsing certificate\n");
return GNUTLS_E_CERTIFICATE_ERROR;
}
if (!gnutls_x509_crt_check_hostname (cert, hostname))
{
rfbClientLog("The certificate's owner does not match hostname '%s'\n",
hostname);
return GNUTLS_E_CERTIFICATE_ERROR;
}
gnutls_x509_crt_deinit (cert);
/* notify gnutls to continue handshake normally */
return 0;
}
static rfbBool
InitializeTLS(void)
{
int ret;
if (rfbTLSInitialized) return TRUE;
if ((ret = gnutls_global_init()) < 0 ||
(ret = gnutls_dh_params_init(&rfbDHParams)) < 0 ||
(ret = gnutls_dh_params_generate2(rfbDHParams, DH_BITS)) < 0)
{
rfbClientLog("Failed to initialized GnuTLS: %s.\n", gnutls_strerror(ret));
return FALSE;
}
rfbClientLog("GnuTLS version %s initialized.\n", gnutls_check_version(NULL));
rfbTLSInitialized = TRUE;
return TRUE;
}
/*
* On Windows, translate WSAGetLastError() to errno values as GNU TLS does it
* internally too. This is necessary because send() and recv() on Windows
* don't set errno when they fail but GNUTLS expects a proper errno value.
*
* Use gnutls_transport_set_global_errno() like the GNU TLS documentation
* suggests to avoid problems with different errno variables when GNU TLS and
* libvncclient are linked to different versions of msvcrt.dll.
*/
#ifdef WIN32
static void WSAtoTLSErrno(gnutls_session_t* session)
{
switch(WSAGetLastError()) {
#if (GNUTLS_VERSION_NUMBER >= 0x029901)
case WSAEWOULDBLOCK:
gnutls_transport_set_errno(session, EAGAIN);
break;
case WSAEINTR:
gnutls_transport_set_errno(session, EINTR);
break;
default:
gnutls_transport_set_errno(session, EIO);
break;
#else
case WSAEWOULDBLOCK:
gnutls_transport_set_global_errno(EAGAIN);
break;
case WSAEINTR:
gnutls_transport_set_global_errno(EINTR);
break;
default:
gnutls_transport_set_global_errno(EIO);
break;
#endif
}
}
#endif
static ssize_t
PushTLS(gnutls_transport_ptr_t transport, const void *data, size_t len)
{
rfbClient *client = (rfbClient*)transport;
int ret;
while (1)
{
ret = write(client->sock, data, len);
if (ret < 0)
{
#ifdef WIN32
WSAtoTLSErrno((gnutls_session_t*)&client->tlsSession);
#endif
if (errno == EINTR) continue;
return -1;
}
return ret;
}
}
static ssize_t
PullTLS(gnutls_transport_ptr_t transport, void *data, size_t len)
{
rfbClient *client = (rfbClient*)transport;
int ret;
while (1)
{
ret = read(client->sock, data, len);
if (ret < 0)
{
#ifdef WIN32
WSAtoTLSErrno((gnutls_session_t*)&client->tlsSession);
#endif
if (errno == EINTR) continue;
return -1;
}
return ret;
}
}
static rfbBool
InitializeTLSSession(rfbClient* client, rfbBool anonTLS)
{
int ret;
const char *p;
if (client->tlsSession) return TRUE;
if ((ret = gnutls_init((gnutls_session_t*)&client->tlsSession, GNUTLS_CLIENT)) < 0)
{
rfbClientLog("Failed to initialized TLS session: %s.\n", gnutls_strerror(ret));
return FALSE;
}
if ((ret = gnutls_priority_set_direct((gnutls_session_t)client->tlsSession,
anonTLS ? rfbAnonTLSPriority : rfbTLSPriority, &p)) < 0)
{
rfbClientLog("Warning: Failed to set TLS priority: %s (%s).\n", gnutls_strerror(ret), p);
}
gnutls_transport_set_ptr((gnutls_session_t)client->tlsSession, (gnutls_transport_ptr_t)client);
gnutls_transport_set_push_function((gnutls_session_t)client->tlsSession, PushTLS);
gnutls_transport_set_pull_function((gnutls_session_t)client->tlsSession, PullTLS);
rfbClientLog("TLS session initialized.\n");
return TRUE;
}
static rfbBool
SetTLSAnonCredential(rfbClient* client)
{
gnutls_anon_client_credentials_t anonCred;
int ret;
if ((ret = gnutls_anon_allocate_client_credentials(&anonCred)) < 0 ||
(ret = gnutls_credentials_set((gnutls_session_t)client->tlsSession, GNUTLS_CRD_ANON, anonCred)) < 0)
{
FreeTLS(client);
rfbClientLog("Failed to create anonymous credentials: %s", gnutls_strerror(ret));
return FALSE;
}
rfbClientLog("TLS anonymous credential created.\n");
return TRUE;
}
static rfbBool
HandshakeTLS(rfbClient* client)
{
int timeout = 15;
int ret;
while (timeout > 0 && (ret = gnutls_handshake((gnutls_session_t)client->tlsSession)) < 0)
{
if (!gnutls_error_is_fatal(ret))
{
rfbClientLog("TLS handshake blocking.\n");
sleep(1);
timeout--;
continue;
}
rfbClientLog("TLS handshake failed: %s.\n", gnutls_strerror(ret));
FreeTLS(client);
return FALSE;
}
if (timeout <= 0)
{
rfbClientLog("TLS handshake timeout.\n");
FreeTLS(client);
return FALSE;
}
rfbClientLog("TLS handshake done.\n");
return TRUE;
}
/* VeNCrypt sub auth. 1 byte auth count, followed by count * 4 byte integers */
static rfbBool
ReadVeNCryptSecurityType(rfbClient* client, uint32_t *result)
{
uint8_t count=0;
uint8_t loop=0;
uint8_t flag=0;
uint32_t tAuth[256], t;
char buf1[500],buf2[10];
uint32_t authScheme;
if (!ReadFromRFBServer(client, (char *)&count, 1)) return FALSE;
if (count==0)
{
rfbClientLog("List of security types is ZERO. Giving up.\n");
return FALSE;
}
if (count>sizeof(tAuth))
{
rfbClientLog("%d security types are too many; maximum is %d\n", count, sizeof(tAuth));
return FALSE;
}
rfbClientLog("We have %d security types to read\n", count);
authScheme=0;
/* now, we have a list of available security types to read ( uint8_t[] ) */
for (loop=0;loop<count;loop++)
{
if (!ReadFromRFBServer(client, (char *)&tAuth[loop], 4)) return FALSE;
t=rfbClientSwap32IfLE(tAuth[loop]);
rfbClientLog("%d) Received security type %d\n", loop, t);
if (flag) continue;
if (t==rfbVeNCryptTLSNone ||
t==rfbVeNCryptTLSVNC ||
t==rfbVeNCryptTLSPlain ||
#ifdef LIBVNCSERVER_HAVE_SASL
t==rfbVeNCryptTLSSASL ||
t==rfbVeNCryptX509SASL ||
#endif /*LIBVNCSERVER_HAVE_SASL */
t==rfbVeNCryptX509None ||
t==rfbVeNCryptX509VNC ||
t==rfbVeNCryptX509Plain)
{
flag++;
authScheme=t;
rfbClientLog("Selecting security type %d (%d/%d in the list)\n", authScheme, loop, count);
/* send back 4 bytes (in original byte order!) indicating which security type to use */
if (!WriteToRFBServer(client, (char *)&tAuth[loop], 4)) return FALSE;
}
tAuth[loop]=t;
}
if (authScheme==0)
{
memset(buf1, 0, sizeof(buf1));
for (loop=0;loop<count;loop++)
{
if (strlen(buf1)>=sizeof(buf1)-1) break;
snprintf(buf2, sizeof(buf2), (loop>0 ? ", %d" : "%d"), (int)tAuth[loop]);
strncat(buf1, buf2, sizeof(buf1)-strlen(buf1)-1);
}
rfbClientLog("Unknown VeNCrypt authentication scheme from VNC server: %s\n",
buf1);
return FALSE;
}
*result = authScheme;
return TRUE;
}
static void
FreeX509Credential(rfbCredential *cred)
{
if (cred->x509Credential.x509CACertFile) free(cred->x509Credential.x509CACertFile);
if (cred->x509Credential.x509CACrlFile) free(cred->x509Credential.x509CACrlFile);
if (cred->x509Credential.x509ClientCertFile) free(cred->x509Credential.x509ClientCertFile);
if (cred->x509Credential.x509ClientKeyFile) free(cred->x509Credential.x509ClientKeyFile);
free(cred);
}
static gnutls_certificate_credentials_t
CreateX509CertCredential(rfbCredential *cred)
{
gnutls_certificate_credentials_t x509_cred;
int ret;
if (!cred->x509Credential.x509CACertFile)
{
rfbClientLog("No CA certificate provided.\n");
return NULL;
}
if ((ret = gnutls_certificate_allocate_credentials(&x509_cred)) < 0)
{
rfbClientLog("Cannot allocate credentials: %s.\n", gnutls_strerror(ret));
return NULL;
}
if ((ret = gnutls_certificate_set_x509_trust_file(x509_cred,
cred->x509Credential.x509CACertFile, GNUTLS_X509_FMT_PEM)) < 0)
{
rfbClientLog("Cannot load CA credentials: %s.\n", gnutls_strerror(ret));
gnutls_certificate_free_credentials (x509_cred);
return NULL;
}
if (cred->x509Credential.x509ClientCertFile && cred->x509Credential.x509ClientKeyFile)
{
if ((ret = gnutls_certificate_set_x509_key_file(x509_cred,
cred->x509Credential.x509ClientCertFile, cred->x509Credential.x509ClientKeyFile,
GNUTLS_X509_FMT_PEM)) < 0)
{
rfbClientLog("Cannot load client certificate or key: %s.\n", gnutls_strerror(ret));
gnutls_certificate_free_credentials (x509_cred);
return NULL;
}
} else
{
rfbClientLog("No client certificate or key provided.\n");
}
if (cred->x509Credential.x509CACrlFile)
{
if ((ret = gnutls_certificate_set_x509_crl_file(x509_cred,
cred->x509Credential.x509CACrlFile, GNUTLS_X509_FMT_PEM)) < 0)
{
rfbClientLog("Cannot load CRL: %s.\n", gnutls_strerror(ret));
gnutls_certificate_free_credentials (x509_cred);
return NULL;
}
} else
{
rfbClientLog("No CRL provided.\n");
}
gnutls_certificate_set_dh_params (x509_cred, rfbDHParams);
return x509_cred;
}
rfbBool
HandleAnonTLSAuth(rfbClient* client)
{
if (!InitializeTLS() || !InitializeTLSSession(client, TRUE)) return FALSE;
if (!SetTLSAnonCredential(client)) return FALSE;
if (!HandshakeTLS(client)) return FALSE;
return TRUE;
}
rfbBool
HandleVeNCryptAuth(rfbClient* client)
{
uint8_t major, minor, status;
uint32_t authScheme;
rfbBool anonTLS;
gnutls_certificate_credentials_t x509_cred = NULL;
int ret;
if (!InitializeTLS()) return FALSE;
/* Read VeNCrypt version */
if (!ReadFromRFBServer(client, (char *)&major, 1) ||
!ReadFromRFBServer(client, (char *)&minor, 1))
{
return FALSE;
}
rfbClientLog("Got VeNCrypt version %d.%d from server.\n", (int)major, (int)minor);
if (major != 0 && minor != 2)
{
rfbClientLog("Unsupported VeNCrypt version.\n");
return FALSE;
}
if (!WriteToRFBServer(client, (char *)&major, 1) ||
!WriteToRFBServer(client, (char *)&minor, 1) ||
!ReadFromRFBServer(client, (char *)&status, 1))
{
return FALSE;
}
if (status != 0)
{
rfbClientLog("Server refused VeNCrypt version %d.%d.\n", (int)major, (int)minor);
return FALSE;
}
if (!ReadVeNCryptSecurityType(client, &authScheme)) return FALSE;
if (!ReadFromRFBServer(client, (char *)&status, 1) || status != 1)
{
rfbClientLog("Server refused VeNCrypt authentication %d (%d).\n", authScheme, (int)status);
return FALSE;
}
client->subAuthScheme = authScheme;
/* Some VeNCrypt security types are anonymous TLS, others are X509 */
switch (authScheme)
{
case rfbVeNCryptTLSNone:
case rfbVeNCryptTLSVNC:
case rfbVeNCryptTLSPlain:
#ifdef LIBVNCSERVER_HAVE_SASL
case rfbVeNCryptTLSSASL:
#endif /* LIBVNCSERVER_HAVE_SASL */
anonTLS = TRUE;
break;
default:
anonTLS = FALSE;
break;
}
/* Get X509 Credentials if it's not anonymous */
if (!anonTLS)
{
rfbCredential *cred;
if (!client->GetCredential)
{
rfbClientLog("GetCredential callback is not set.\n");
return FALSE;
}
cred = client->GetCredential(client, rfbCredentialTypeX509);
if (!cred)
{
rfbClientLog("Reading credential failed\n");
return FALSE;
}
x509_cred = CreateX509CertCredential(cred);
FreeX509Credential(cred);
if (!x509_cred) return FALSE;
}
/* Start up the TLS session */
if (!InitializeTLSSession(client, anonTLS)) return FALSE;
if (anonTLS)
{
if (!SetTLSAnonCredential(client)) return FALSE;
}
else
{
/* Set the certificate verification callback. */
gnutls_certificate_set_verify_function (x509_cred, verify_certificate_callback);
gnutls_session_set_ptr ((gnutls_session_t)client->tlsSession, (void *)client);
if ((ret = gnutls_credentials_set((gnutls_session_t)client->tlsSession, GNUTLS_CRD_CERTIFICATE, x509_cred)) < 0)
{
rfbClientLog("Cannot set x509 credential: %s.\n", gnutls_strerror(ret));
FreeTLS(client);
return FALSE;
}
}
if (!HandshakeTLS(client)) return FALSE;
/* We are done here. The caller should continue with client->subAuthScheme
* to do actual sub authentication.
*/
return TRUE;
}
int
ReadFromTLS(rfbClient* client, char *out, unsigned int n)
{
ssize_t ret;
ret = gnutls_record_recv((gnutls_session_t)client->tlsSession, out, n);
if (ret >= 0) return ret;
if (ret == GNUTLS_E_REHANDSHAKE || ret == GNUTLS_E_AGAIN)
{
errno = EAGAIN;
} else
{
rfbClientLog("Error reading from TLS: %s.\n", gnutls_strerror(ret));
errno = EINTR;
}
return -1;
}
int
WriteToTLS(rfbClient* client, const char *buf, unsigned int n)
{
unsigned int offset = 0;
ssize_t ret;
if (client->LockWriteToTLS)
{
if (!client->LockWriteToTLS(client))
{
rfbClientLog("Callback to get lock in WriteToTLS() failed\n");
return -1;
}
}
while (offset < n)
{
ret = gnutls_record_send((gnutls_session_t)client->tlsSession, buf+offset, (size_t)(n-offset));
if (ret == 0) continue;
if (ret < 0)
{
if (ret == GNUTLS_E_AGAIN || ret == GNUTLS_E_INTERRUPTED) continue;
rfbClientLog("Error writing to TLS: %s.\n", gnutls_strerror(ret));
if (client->UnlockWriteToTLS)
{
if (!client->UnlockWriteToTLS(client))
rfbClientLog("Callback to unlock WriteToTLS() failed\n");
}
return -1;
}
offset += (unsigned int)ret;
}
if (client->UnlockWriteToTLS)
{
if (!client->UnlockWriteToTLS(client))
{
rfbClientLog("Callback to unlock WriteToTLS() failed\n");
return -1;
}
}
return offset;
}
void FreeTLS(rfbClient* client)
{
if (client->tlsSession)
{
gnutls_deinit((gnutls_session_t)client->tlsSession);
client->tlsSession = NULL;
}
}
#ifdef LIBVNCSERVER_HAVE_SASL
int
GetTLSCipherBits(rfbClient* client)
{
gnutls_cipher_algorithm_t cipher = gnutls_cipher_get((gnutls_session_t)client->tlsSession);
return gnutls_cipher_get_key_size(cipher) * 8;
}
#endif /* LIBVNCSERVER_HAVE_SASL */