/*
* The software in this file is derived from the vncconnection.c source file
* from the GTK VNC Widget with modifications by S. Waterman <simon.waterman@zynstra.com>
* for compatibility with libvncserver. The copyright and license
* statements below apply only to this source file and to no other parts of the
* libvncserver library.
*
* GTK VNC Widget
*
* Copyright (C) 2006 Anthony Liguori <anthony@codemonkey.ws>
* Copyright (C) 2009-2010 Daniel P. Berrange <dan@berrange.com>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.0 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/*
* sasl.c - functions to deal with client side of the SASL protocol.
*/
#ifdef __STRICT_ANSI__
#define _BSD_SOURCE
#define _POSIX_SOURCE
#define _XOPEN_SOURCE 600
#endif
#include <errno.h>
#include <rfb/rfbclient.h>
#ifdef WIN32
#undef SOCKET
#include <winsock2.h>
#ifdef EWOULDBLOCK
#undef EWOULDBLOCK
#endif
#define EWOULDBLOCK WSAEWOULDBLOCK
#define socklen_t int
#define close closesocket
#define read(sock,buf,len) recv(sock,buf,len,0)
#define write(sock,buf,len) send(sock,buf,len,0)
#ifdef LIBVNCSERVER_HAVE_WS2TCPIP_H
#undef socklen_t
#include <ws2tcpip.h>
#endif /* LIBVNCSERVER_HAVE_WS2TCPIP_H */
#else /* WIN32 */
#include <arpa/inet.h>
#endif /* WIN32 */
#include "sasl.h"
#include "tls.h"
#ifdef _MSC_VER
# define snprintf _snprintf /* MSVC went straight to the underscored syntax */
#endif
/*
* NB, keep in sync with similar method in qemud/remote.c
*/
static char *vnc_connection_addr_to_string(char *host, int port)
{
char * buf = (char *)malloc(strlen(host) + 7);
sprintf(buf, "%s;%hu", host, port);
return buf;
}
static int log_func(void *context,
int level,
const char *message)
{
rfbClientLog("SASL: %s\n", message);
return SASL_OK;
}
static int user_callback_adapt(void *context,
int id,
const char **result,
unsigned *len)
{
rfbClient* client = (rfbClient *)context;
if (id != SASL_CB_AUTHNAME) {
rfbClientLog("Unrecognized SASL callback ID %d\n", id);
return SASL_FAIL;
}
if (!client->GetUser) {
rfbClientLog("Client user callback not found\n");
return SASL_FAIL;
}
*result = client->GetUser(client);
if (! *result) return SASL_FAIL;
/**len = strlen(*result);*/
return SASL_OK;
}
static int password_callback_adapt(sasl_conn_t *conn,
void * context,
int id,
sasl_secret_t **secret)
{
rfbClient* client = (rfbClient *)context;
char * password;
if (id != SASL_CB_PASS) {
rfbClientLog("Unrecognized SASL callback ID %d\n", id);
return SASL_FAIL;
}
if (client->saslSecret) { /* If we've already got it just return it. */
*secret = client->saslSecret;
return SASL_OK;
}
if (!client->GetPassword) {
rfbClientLog("Client password callback not found\n");
return SASL_FAIL;
}
password = client->GetPassword(client);
if (! password) return SASL_FAIL;
sasl_secret_t *lsec = (sasl_secret_t *)malloc(sizeof(sasl_secret_t) + strlen(password));
if (!lsec) {
rfbClientLog("Could not allocate sasl_secret_t\n");
return SASL_FAIL;
}
strcpy(lsec->data, password);
lsec->len = strlen(password);
client->saslSecret = lsec;
*secret = lsec;
/* Clear client password */
size_t i;
for (i = 0; i < lsec->len; i++) {
password[i] = '\0';
}
free(password);
return SASL_OK;
}
#define SASL_MAX_MECHLIST_LEN 300
#define SASL_MAX_DATA_LEN (1024 * 1024)
/* Perform the SASL authentication process
*/
rfbBool
HandleSASLAuth(rfbClient *client)
{
sasl_conn_t *saslconn = NULL;
sasl_security_properties_t secprops;
const char *clientout;
char *serverin = NULL;
unsigned int clientoutlen, serverinlen;
int err, complete = 0;
char *localAddr = NULL, *remoteAddr = NULL;
const void *val;
sasl_ssf_t ssf;
sasl_callback_t saslcb[] = {
{SASL_CB_LOG, (void *)log_func, NULL},
{SASL_CB_AUTHNAME, client->GetUser ? (void *)user_callback_adapt : NULL, client},
{SASL_CB_PASS, client->GetPassword ? (void *)password_callback_adapt : NULL, client},
{ .id = 0 },
};
sasl_interact_t *interact = NULL;
uint32_t mechlistlen;
char *mechlist;
char *wantmech;
const char *mechname;
rfbBool ret;
client->saslconn = NULL;
/* Sets up the SASL library as a whole */
err = sasl_client_init(NULL);
rfbClientLog("Client initialize SASL authentication %d\n", err);
if (err != SASL_OK) {
rfbClientLog("failed to initialize SASL library: %d (%s)\n",
err, sasl_errstring(err, NULL, NULL));
goto error;
}
/* Get local address in form IPADDR:PORT */
struct sockaddr_storage localAddress;
socklen_t addressLength = sizeof(localAddress);
char buf[INET6_ADDRSTRLEN];
int port;
if (getsockname(client->sock, (struct sockaddr*)&localAddress, &addressLength)) {
rfbClientLog("failed to get local address\n");
goto error;
}
if (localAddress.ss_family == AF_INET) {
struct sockaddr_in *sa_in = (struct sockaddr_in*)&localAddress;
inet_ntop(AF_INET, &(sa_in->sin_addr), buf, INET_ADDRSTRLEN);
port = ntohs(sa_in->sin_port);
localAddr = vnc_connection_addr_to_string(buf, port);
} else if (localAddress.ss_family == AF_INET6) {
struct sockaddr_in6 *sa_in = (struct sockaddr_in6*)&localAddress;
inet_ntop(AF_INET6, &(sa_in->sin6_addr), buf, INET6_ADDRSTRLEN);
port = ntohs(sa_in->sin6_port);
localAddr = vnc_connection_addr_to_string(buf, port);
} else {
rfbClientLog("failed to get local address\n");
goto error;
}
/* Get remote address in form IPADDR:PORT */
remoteAddr = vnc_connection_addr_to_string(client->serverHost, client->serverPort);
rfbClientLog("Client SASL new host:'%s' local:'%s' remote:'%s'\n", client->serverHost, localAddr, remoteAddr);
/* Setup a handle for being a client */
err = sasl_client_new("vnc",
client->serverHost,
localAddr,
remoteAddr,
saslcb,
SASL_SUCCESS_DATA,
&saslconn);
free(localAddr);
free(remoteAddr);
if (err != SASL_OK) {
rfbClientLog("Failed to create SASL client context: %d (%s)\n",
err, sasl_errstring(err, NULL, NULL));
goto error;
}
/* Initialize some connection props we care about */
if (client->tlsSession) {
if (!(ssf = (sasl_ssf_t)GetTLSCipherBits(client))) {
rfbClientLog("%s", "invalid cipher size for TLS session\n");
goto error;
}
rfbClientLog("Setting external SSF %d\n", ssf);
err = sasl_setprop(saslconn, SASL_SSF_EXTERNAL, &ssf);
if (err != SASL_OK) {
rfbClientLog("cannot set external SSF %d (%s)\n",
err, sasl_errstring(err, NULL, NULL));
goto error;
}
}
memset (&secprops, 0, sizeof secprops);
/* If we've got TLS, we don't care about SSF */
secprops.min_ssf = client->tlsSession ? 0 : 56; /* Equiv to DES supported by all Kerberos */
secprops.max_ssf = client->tlsSession ? 0 : 100000; /* Very strong ! AES == 256 */
secprops.maxbufsize = 100000;
/* If we're not TLS, then forbid any anonymous or trivially crackable auth */
secprops.security_flags = client->tlsSession ? 0 :
SASL_SEC_NOANONYMOUS | SASL_SEC_NOPLAINTEXT;
err = sasl_setprop(saslconn, SASL_SEC_PROPS, &secprops);
if (err != SASL_OK) {
rfbClientLog("cannot set security props %d (%s)\n",
err, sasl_errstring(err, NULL, NULL));
goto error;
}
/* Get the supported mechanisms from the server */
if (!ReadFromRFBServer(client, (char *)&mechlistlen, 4)) {
rfbClientLog("failed to read mechlistlen\n");
goto error;
}
mechlistlen = rfbClientSwap32IfLE(mechlistlen);
rfbClientLog("mechlistlen is %d\n", mechlistlen);
if (mechlistlen > SASL_MAX_MECHLIST_LEN) {
rfbClientLog("mechlistlen %d too long\n", mechlistlen);
goto error;
}
mechlist = malloc(mechlistlen+1);
if (!ReadFromRFBServer(client, mechlist, mechlistlen)) {
free(mechlist);
goto error;
}
mechlist[mechlistlen] = '\0';
/* Allow the client to influence the mechanism selected. */
if (client->GetSASLMechanism) {
wantmech = client->GetSASLMechanism(client, mechlist);
if (wantmech && *wantmech != 0) {
if (strstr(mechlist, wantmech) == NULL) {
rfbClientLog("Client requested SASL mechanism %s not supported by server\n",
wantmech);
free(mechlist);
free(wantmech);
goto error;
} else {
free(mechlist);
mechlist = wantmech;
}
}
}
rfbClientLog("Client start negotiation mechlist '%s'\n", mechlist);
restart:
/* Start the auth negotiation on the client end first */
err = sasl_client_start(saslconn,
mechlist,
&interact,
&clientout,
&clientoutlen,
&mechname);
if (err != SASL_OK && err != SASL_CONTINUE && err != SASL_INTERACT) {
rfbClientLog("Failed to start SASL negotiation: %d (%s)\n",
err, sasl_errdetail(saslconn));
free(mechlist);
mechlist = NULL;
goto error;
}
/* Need to gather some credentials from the client */
if (err == SASL_INTERACT) {
rfbClientLog("User interaction required but not currently supported\n");
goto error;
}
rfbClientLog("Server start negotiation with mech %s. Data %d bytes %p '%s'\n",
mechname, clientoutlen, clientout, clientout);
if (clientoutlen > SASL_MAX_DATA_LEN) {
rfbClientLog("SASL negotiation data too long: %d bytes\n",
clientoutlen);
goto error;
}
/* Send back the chosen mechname */
uint32_t mechnamelen = rfbClientSwap32IfLE(strlen(mechname));
if (!WriteToRFBServer(client, (char *)&mechnamelen, 4)) goto error;
if (!WriteToRFBServer(client, (char *)mechname, strlen(mechname))) goto error;
/* NB, distinction of NULL vs "" is *critical* in SASL */
if (clientout) {
uint32_t colsw = rfbClientSwap32IfLE(clientoutlen + 1);
if (!WriteToRFBServer(client, (char *)&colsw, 4)) goto error;
if (!WriteToRFBServer(client, (char *)clientout, clientoutlen + 1)) goto error;
} else {
uint32_t temp = 0;
if (!WriteToRFBServer(client, (char *)&temp, 4)) goto error;
}
rfbClientLog("%s", "Getting sever start negotiation reply\n");
/* Read the 'START' message reply from server */
if (!ReadFromRFBServer(client, (char *)&serverinlen, 4)) goto error;
serverinlen = rfbClientSwap32IfLE(serverinlen);
if (serverinlen > SASL_MAX_DATA_LEN) {
rfbClientLog("SASL negotiation data too long: %d bytes\n",
serverinlen);
goto error;
}
/* NB, distinction of NULL vs "" is *critical* in SASL */
if (serverinlen) {
serverin = malloc(serverinlen);
if (!ReadFromRFBServer(client, serverin, serverinlen)) goto error;
serverin[serverinlen-1] = '\0';
serverinlen--;
} else {
serverin = NULL;
}
if (!ReadFromRFBServer(client, (char *)&complete, 1)) goto error;
rfbClientLog("Client start result complete: %d. Data %d bytes %p '%s'\n",
complete, serverinlen, serverin, serverin);
/* Loop-the-loop...
* Even if the server has completed, the client must *always* do at least one step
* in this loop to verify the server isn't lying about something. Mutual auth */
for (;;) {
restep:
err = sasl_client_step(saslconn,
serverin,
serverinlen,
&interact,
&clientout,
&clientoutlen);
if (err != SASL_OK && err != SASL_CONTINUE && err != SASL_INTERACT) {
rfbClientLog("Failed SASL step: %d (%s)\n",
err, sasl_errdetail(saslconn));
goto error;
}
/* Need to gather some credentials from the client */
if (err == SASL_INTERACT) {
rfbClientLog("User interaction required but not currently supported\n");
goto error;
}
if (serverin) {
free(serverin);
serverin = NULL;
}
rfbClientLog("Client step result %d. Data %d bytes %p '%s'\n", err, clientoutlen, clientout, clientout);
/* Previous server call showed completion & we're now locally complete too */
if (complete && err == SASL_OK)
break;
/* Not done, prepare to talk with the server for another iteration */
/* NB, distinction of NULL vs "" is *critical* in SASL */
if (clientout) {
uint32_t colsw = rfbClientSwap32IfLE(clientoutlen + 1);
if (!WriteToRFBServer(client, (char *)&colsw, 4)) goto error;
if (!WriteToRFBServer(client, (char *)clientout, clientoutlen + 1)) goto error;
} else {
uint32_t temp = 0;
if (!WriteToRFBServer(client, (char *)&temp, 4)) goto error;
}
rfbClientLog("Server step with %d bytes %p\n", clientoutlen, clientout);
if (!ReadFromRFBServer(client, (char *)&serverinlen, 4)) goto error;
serverinlen = rfbClientSwap32IfLE(serverinlen);
if (serverinlen > SASL_MAX_DATA_LEN) {
rfbClientLog("SASL negotiation data too long: %d bytes\n",
serverinlen);
goto error;
}
/* NB, distinction of NULL vs "" is *critical* in SASL */
if (serverinlen) {
serverin = malloc(serverinlen);
if (!ReadFromRFBServer(client, serverin, serverinlen)) goto error;
serverin[serverinlen-1] = '\0';
serverinlen--;
} else {
serverin = NULL;
}
if (!ReadFromRFBServer(client, (char *)&complete, 1)) goto error;
rfbClientLog("Client step result complete: %d. Data %d bytes %p '%s'\n",
complete, serverinlen, serverin, serverin);
/* This server call shows complete, and earlier client step was OK */
if (complete && err == SASL_OK) {
free(serverin);
serverin = NULL;
break;
}
}
/* Check for suitable SSF if non-TLS */
if (!client->tlsSession) {
err = sasl_getprop(saslconn, SASL_SSF, &val);
if (err != SASL_OK) {
rfbClientLog("cannot query SASL ssf on connection %d (%s)\n",
err, sasl_errstring(err, NULL, NULL));
goto error;
}
ssf = *(const int *)val;
rfbClientLog("SASL SSF value %d\n", ssf);
if (ssf < 56) { /* 56 == DES level, good for Kerberos */
rfbClientLog("negotiation SSF %d was not strong enough\n", ssf);
goto error;
}
}
rfbClientLog("%s", "SASL authentication complete\n");
uint32_t result;
if (!ReadFromRFBServer(client, (char *)&result, 4)) {
rfbClientLog("Failed to read authentication result\n");
goto error;
}
result = rfbClientSwap32IfLE(result);
if (result != 0) {
rfbClientLog("Authentication failure\n");
goto error;
}
rfbClientLog("Authentication successful - switching to SSF\n");
/* This must come *after* check-auth-result, because the former
* is defined to be sent unencrypted, and setting saslconn turns
* on the SSF layer encryption processing */
client->saslconn = saslconn;
/* Clear SASL secret from memory if set - it'll be free'd on dispose */
if (client->saslSecret) {
size_t i;
for (i = 0; i < client->saslSecret->len; i++)
client->saslSecret->data[i] = '\0';
client->saslSecret->len = 0;
}
return TRUE;
error:
if (client->saslSecret) {
size_t i;
for (i = 0; i < client->saslSecret->len; i++)
client->saslSecret->data[i] = '\0';
client->saslSecret->len = 0;
}
if (saslconn)
sasl_dispose(&saslconn);
return FALSE;
}
int
ReadFromSASL(rfbClient* client, char *out, unsigned int n)
{
size_t want;
if (client->saslDecoded == NULL) {
char *encoded;
int encodedLen;
int err, ret;
encodedLen = 8192;
encoded = (char *)malloc(encodedLen);
ret = read(client->sock, encoded, encodedLen);
if (ret < 0) {
free(encoded);
return ret;
}
if (ret == 0) {
free(encoded);
errno = EIO;
return -EIO;
}
err = sasl_decode(client->saslconn, encoded, ret,
&client->saslDecoded, &client->saslDecodedLength);
free(encoded);
if (err != SASL_OK) {
rfbClientLog("Failed to decode SASL data %s\n",
sasl_errstring(err, NULL, NULL));
return -EINVAL;
}
client->saslDecodedOffset = 0;
}
want = client->saslDecodedLength - client->saslDecodedOffset;
if (want > n)
want = n;
memcpy(out,
client->saslDecoded + client->saslDecodedOffset,
want);
client->saslDecodedOffset += want;
if (client->saslDecodedOffset == client->saslDecodedLength) {
client->saslDecodedLength = client->saslDecodedOffset = 0;
client->saslDecoded = NULL;
}
if (!want) {
errno = EAGAIN;
return -EAGAIN;
}
return want;
}