Add SASL authentication support ("Daniel P. Berrange")

This patch adds the new SASL authentication protocol to the VNC server.

It is enabled by setting the 'sasl' flag when launching VNC. SASL can
optionally provide encryption via its SSF layer, if a suitable mechanism
is configured (eg, GSSAPI/Kerberos, or Digest-MD5).  If an SSF layer is
not available, then it should be combined with the x509 VNC authentication
protocol which provides encryption.

eg, if using GSSAPI

   qemu -vnc localhost:1,sasl

eg if using  TLS/x509 for encryption

   qemu -vnc localhost:1,sasl,tls,x509


By default the Cyrus SASL library will look for its configuration in
the file /etc/sasl2/qemu.conf.  For non-root users, this can be overridden
by setting the SASL_CONF_PATH environment variable, eg to make it look in
$HOME/.sasl2.  NB unprivileged users may not have access to the full range
of SASL mechanisms, since some of them require some administrative privileges
to configure. The patch includes an example SASL configuration file which
illustrates config for GSSAPI and Digest-MD5, though it should be noted that
the latter is not really considered secure any more.

Most of the SASL authentication code is located in a separate source file,
vnc-auth-sasl.c.  The main vnc.c file only contains minimal integration
glue, specifically parsing of command line flags / setup, and calls to
start the SASL auth process, to do encoding/decoding for data.

There are several possible stacks for reading & writing of data, depending
on the combo of VNC authentication methods in use

 - Clear.    read/write straight to socket
 - TLS.      read/write via GNUTLS helpers
 - SASL.     encode/decode via SASL SSF layer, then read/write to socket
 - SASL+TLS. encode/decode via SASL SSF layer, then read/write via GNUTLS

Hence, the vnc_client_read & vnc_client_write methods have been refactored
a little.

   vnc_client_read:  main entry point for reading, calls either

       - vnc_client_read_plain   reading, with no intermediate decoding
       - vnc_client_read_sasl    reading, with SASL SSF decoding

   These two methods, then call vnc_client_read_buf(). This decides
   whether to write to the socket directly or write via GNUTLS.

The situation is the same for writing data. More extensive comments
have been added in the code / patch. The vnc_client_read_sasl and
vnc_client_write_sasl method implementations live in the separate
vnc-auth-sasl.c file.

The state required for the SASL auth mechanism is kept in a separate
VncStateSASL struct, defined in vnc-auth-sasl.h and included in the
main VncState.

The configure script probes for SASL and automatically enables it
if found, unless --disable-vnc-sasl was given to override it.


 Makefile            |    7 
 Makefile.target     |    5 
 b/qemu.sasl         |   34 ++
 b/vnc-auth-sasl.c   |  626 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 b/vnc-auth-sasl.h   |   67 +++++
 configure           |   34 ++
 qemu-doc.texi       |   97 ++++++++
 vnc-auth-vencrypt.c |   12 
 vnc.c               |  249 ++++++++++++++++++--
 vnc.h               |   31 ++
 10 files changed, 1129 insertions(+), 33 deletions(-)

   Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>


git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6724 c046a42c-6fe2-441c-8c8c-71466251a162

9 files changed, 1119 insertions, 31 deletions

diff --git a/Makefile b/Makefile
index e8d1a5cdc..e9a75c422 100644
--- a/Makefile
+++ b/Makefile
@@ -148,6 +148,9 @@ OBJS+=vnc.o d3des.o
 ifdef CONFIG_VNC_TLS
 OBJS+=vnc-tls.o vnc-auth-vencrypt.o
 endif
+ifdef CONFIG_VNC_SASL
+OBJS+=vnc-auth-sasl.o
+endif
 
 ifdef CONFIG_COCOA
 OBJS+=cocoa.o
@@ -171,7 +174,7 @@ sdl.o: sdl.c keymaps.h sdl_keysym.h
 
 sdl.o audio/sdlaudio.o: CFLAGS += $(SDL_CFLAGS)
 
-vnc.h: vnc-tls.h vnc-auth-vencrypt.h keymaps.h
+vnc.h: vnc-tls.h vnc-auth-vencrypt.h vnc-auth-sasl.h keymaps.h
 
 vnc.o: vnc.c vnc.h vnc_keysym.h vnchextile.h d3des.c d3des.h
 
@@ -181,6 +184,8 @@ vnc-tls.o: vnc-tls.c vnc.h
 
 vnc-auth-vencrypt.o: vnc-auth-vencrypt.c vnc.h
 
+vnc-auth-sasl.o: vnc-auth-sasl.c vnc.h
+
 curses.o: curses.c keymaps.h curses_keys.h
 
 bt-host.o: CFLAGS += $(CONFIG_BLUEZ_CFLAGS)
diff --git a/Makefile.target b/Makefile.target
index f33f7621f..9a2f123d3 100644
--- a/Makefile.target
+++ b/Makefile.target
@@ -554,6 +554,11 @@ CPPFLAGS += $(CONFIG_VNC_TLS_CFLAGS)
 LIBS += $(CONFIG_VNC_TLS_LIBS)
 endif
 
+ifdef CONFIG_VNC_SASL
+CPPFLAGS += $(CONFIG_VNC_SASL_CFLAGS)
+LIBS += $(CONFIG_VNC_SASL_LIBS)
+endif
+
 ifdef CONFIG_BLUEZ
 LIBS += $(CONFIG_BLUEZ_LIBS)
 endif
diff --git a/configure b/configure
index faacb8de0..5c2b15447 100755
--- a/configure
+++ b/configure
@@ -164,6 +164,7 @@ fmod_lib=""
 fmod_inc=""
 oss_lib=""
 vnc_tls="yes"
+vnc_sasl="yes"
 bsd="no"
 linux="no"
 solaris="no"
@@ -388,6 +389,8 @@ for opt do
   ;;
   --disable-vnc-tls) vnc_tls="no"
   ;;
+  --disable-vnc-sasl) vnc_sasl="no"
+  ;;
   --disable-slirp) slirp="no"
   ;;
   --disable-vde) vde="no"
@@ -545,6 +548,7 @@ echo "                           Available cards: $audio_possible_cards"
 echo "  --enable-mixemu          enable mixer emulation"
 echo "  --disable-brlapi         disable BrlAPI"
 echo "  --disable-vnc-tls        disable TLS encryption for VNC server"
+echo "  --disable-vnc-sasl       disable SASL encryption for VNC server"
 echo "  --disable-curses         disable curses output"
 echo "  --disable-bluez          disable bluez stack connectivity"
 echo "  --disable-kvm            disable KVM acceleration support"
@@ -839,6 +843,25 @@ EOF
 fi
 
 ##########################################
+# VNC SASL detection
+if test "$vnc_sasl" = "yes" ; then
+cat > $TMPC <<EOF
+#include <sasl/sasl.h>
+#include <stdio.h>
+int main(void) { sasl_server_init(NULL, "qemu"); return 0; }
+EOF
+    # Assuming Cyrus-SASL installed in /usr prefix
+    vnc_sasl_cflags=""
+    vnc_sasl_libs="-lsasl2"
+    if $cc $ARCH_CFLAGS -o $TMPE ${OS_CFLAGS} $vnc_sasl_cflags $TMPC \
+           $vnc_sasl_libs 2> /dev/null ; then
+	:
+    else
+	vnc_sasl="no"
+    fi
+fi
+
+##########################################
 # vde libraries probe
 if test "$vde" = "yes" ; then
   cat > $TMPC << EOF
@@ -1146,6 +1169,11 @@ if test "$vnc_tls" = "yes" ; then
     echo "    TLS CFLAGS    $vnc_tls_cflags"
     echo "    TLS LIBS      $vnc_tls_libs"
 fi
+echo "VNC SASL support  $vnc_sasl"
+if test "$vnc_sasl" = "yes" ; then
+    echo "    SASL CFLAGS    $vnc_sasl_cflags"
+    echo "    SASL LIBS      $vnc_sasl_libs"
+fi
 if test -n "$sparc_cpu"; then
     echo "Target Sparc Arch $sparc_cpu"
 fi
@@ -1387,6 +1415,12 @@ if test "$vnc_tls" = "yes" ; then
   echo "CONFIG_VNC_TLS_LIBS=$vnc_tls_libs" >> $config_mak
   echo "#define CONFIG_VNC_TLS 1" >> $config_h
 fi
+if test "$vnc_sasl" = "yes" ; then
+  echo "CONFIG_VNC_SASL=yes" >> $config_mak
+  echo "CONFIG_VNC_SASL_CFLAGS=$vnc_sasl_cflags" >> $config_mak
+  echo "CONFIG_VNC_SASL_LIBS=$vnc_sasl_libs" >> $config_mak
+  echo "#define CONFIG_VNC_SASL 1" >> $config_h
+fi
 qemu_version=`head $source_path/VERSION`
 echo "VERSION=$qemu_version" >>$config_mak
 echo "#define QEMU_VERSION \"$qemu_version\"" >> $config_h
diff --git a/qemu-doc.texi b/qemu-doc.texi
index 616de48c0..1528f39cf 100644
--- a/qemu-doc.texi
+++ b/qemu-doc.texi
@@ -616,6 +616,21 @@ path following this option specifies where the x509 certificates are to
 be loaded from. See the @ref{vnc_security} section for details on generating
 certificates.
 
+@item sasl
+
+Require that the client use SASL to authenticate with the VNC server.
+The exact choice of authentication method used is controlled from the
+system / user's SASL configuration file for the 'qemu' service. This
+is typically found in /etc/sasl2/qemu.conf. If running QEMU as an
+unprivileged user, an environment variable SASL_CONF_PATH can be used
+to make it search alternate locations for the service config.
+While some SASL auth methods can also provide data encryption (eg GSSAPI),
+it is recommended that SASL always be combined with the 'tls' and
+'x509' settings to enable use of SSL and server certificates. This
+ensures a data encryption preventing compromise of authentication
+credentials. See the @ref{vnc_security} section for details on using
+SASL authentication.
+
 @end table
 
 @end table
@@ -2061,7 +2076,10 @@ considerations depending on the deployment scenarios.
 * vnc_sec_certificate::
 * vnc_sec_certificate_verify::
 * vnc_sec_certificate_pw::
+* vnc_sec_sasl::
+* vnc_sec_certificate_sasl::
 * vnc_generate_cert::
+* vnc_setup_sasl::
 @end menu
 @node vnc_sec_none
 @subsection Without passwords
@@ -2144,6 +2162,41 @@ Password: ********
 (qemu)
 @end example
 
+
+@node vnc_sec_sasl
+@subsection With SASL authentication
+
+The SASL authentication method is a VNC extension, that provides an
+easily extendable, pluggable authentication method. This allows for
+integration with a wide range of authentication mechanisms, such as
+PAM, GSSAPI/Kerberos, LDAP, SQL databases, one-time keys and more.
+The strength of the authentication depends on the exact mechanism
+configured. If the chosen mechanism also provides a SSF layer, then
+it will encrypt the datastream as well.
+
+Refer to the later docs on how to choose the exact SASL mechanism
+used for authentication, but assuming use of one supporting SSF,
+then QEMU can be launched with:
+
+@example
+qemu [...OPTIONS...] -vnc :1,sasl -monitor stdio
+@end example
+
+@node vnc_sec_certificate_sasl
+@subsection With x509 certificates and SASL authentication
+
+If the desired SASL authentication mechanism does not supported
+SSF layers, then it is strongly advised to run it in combination
+with TLS and x509 certificates. This provides securely encrypted
+data stream, avoiding risk of compromising of the security
+credentials. This can be enabled, by combining the 'sasl' option
+with the aforementioned TLS + x509 options:
+
+@example
+qemu [...OPTIONS...] -vnc :1,tls,x509,sasl -monitor stdio
+@end example
+
+
 @node vnc_generate_cert
 @subsection Generating certificates for VNC
 
@@ -2255,6 +2308,50 @@ EOF
 The @code{client-key.pem} and @code{client-cert.pem} files should now be securely
 copied to the client for which they were generated.
 
+
+@node vnc_setup_sasl
+
+@subsection Configuring SASL mechanisms
+
+The following documentation assumes use of the Cyrus SASL implementation on a
+Linux host, but the principals should apply to any other SASL impl. When SASL
+is enabled, the mechanism configuration will be loaded from system default
+SASL service config /etc/sasl2/qemu.conf. If running QEMU as an
+unprivileged user, an environment variable SASL_CONF_PATH can be used
+to make it search alternate locations for the service config.
+
+The default configuration might contain
+
+@example
+mech_list: digest-md5
+sasldb_path: /etc/qemu/passwd.db
+@end example
+
+This says to use the 'Digest MD5' mechanism, which is similar to the HTTP
+Digest-MD5 mechanism. The list of valid usernames & passwords is maintained
+in the /etc/qemu/passwd.db file, and can be updated using the saslpasswd2
+command. While this mechanism is easy to configure and use, it is not
+considered secure by modern standards, so only suitable for developers /
+ad-hoc testing.
+
+A more serious deployment might use Kerberos, which is done with the 'gssapi'
+mechanism
+
+@example
+mech_list: gssapi
+keytab: /etc/qemu/krb5.tab
+@end example
+
+For this to work the administrator of your KDC must generate a Kerberos
+principal for the server, with a name of  'qemu/somehost.example.com@@EXAMPLE.COM'
+replacing 'somehost.example.com' with the fully qualified host name of the
+machine running QEMU, and 'EXAMPLE.COM' with the Keberos Realm.
+
+Other configurations will be left as an exercise for the reader. It should
+be noted that only Digest-MD5 and GSSAPI provides a SSF layer for data
+encryption. For all other mechanisms, VNC should always be configured to
+use TLS and x509 certificates to protect security credentials from snooping.
+
 @node gdb_usage
 @section GDB usage
 
diff --git a/qemu.sasl b/qemu.sasl
new file mode 100644
index 000000000..cf19cf8d0
--- /dev/null
+++ b/qemu.sasl
@@ -0,0 +1,34 @@
+# If you want to use the non-TLS socket, then you *must* include
+# the GSSAPI or DIGEST-MD5 mechanisms, because they are the only
+# ones that can offer session encryption as well as authentication.
+#
+# If you're only using TLS, then you can turn on any mechanisms
+# you like for authentication, because TLS provides the encryption
+#
+# Default to a simple username+password mechanism
+# NB digest-md5 is no longer considered secure by current standards
+mech_list: digest-md5
+
+# Before you can use GSSAPI, you need a service principle on the
+# KDC server for libvirt, and that to be exported to the keytab
+# file listed below
+#mech_list: gssapi
+#
+# You can also list many mechanisms at once, then the user can choose
+# by adding  '?auth=sasl.gssapi' to their libvirt URI, eg
+#   qemu+tcp://hostname/system?auth=sasl.gssapi
+#mech_list: digest-md5 gssapi
+
+# Some older builds of MIT kerberos on Linux ignore this option &
+# instead need KRB5_KTNAME env var.
+# For modern Linux, and other OS, this should be sufficient
+keytab: /etc/qemu/krb5.tab
+
+# If using digest-md5 for username/passwds, then this is the file
+# containing the passwds. Use 'saslpasswd2 -a qemu [username]'
+# to add entries, and 'sasldblistusers2 -a qemu' to browse it
+sasldb_path: /etc/qemu/passwd.db
+
+
+auxprop_plugin: sasldb
+
diff --git a/vnc-auth-sasl.c b/vnc-auth-sasl.c
new file mode 100644
index 000000000..2882a357d
--- /dev/null
+++ b/vnc-auth-sasl.c
@@ -0,0 +1,626 @@
+/*
+ * QEMU VNC display driver: SASL auth protocol
+ *
+ * Copyright (C) 2009 Red Hat, Inc
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "vnc.h"
+
+/* Max amount of data we send/recv for SASL steps to prevent DOS */
+#define SASL_DATA_MAX_LEN (1024 * 1024)
+
+
+void vnc_sasl_client_cleanup(VncState *vs)
+{
+    if (vs->sasl.conn) {
+	vs->sasl.runSSF = vs->sasl.waitWriteSSF = vs->sasl.wantSSF = 0;
+	vs->sasl.encodedLength = vs->sasl.encodedOffset = 0;
+	vs->sasl.encoded = NULL;
+	free(vs->sasl.username);
+	free(vs->sasl.mechlist);
+	vs->sasl.username = vs->sasl.mechlist = NULL;
+	sasl_dispose(&vs->sasl.conn);
+	vs->sasl.conn = NULL;
+    }
+}
+
+
+long vnc_client_write_sasl(VncState *vs)
+{
+    long ret;
+
+    VNC_DEBUG("Write SASL: Pending output %p size %d offset %d Encoded: %p size %d offset %d\n",
+	      vs->output.buffer, vs->output.capacity, vs->output.offset,
+	      vs->sasl.encoded, vs->sasl.encodedLength, vs->sasl.encodedOffset);
+
+    if (!vs->sasl.encoded) {
+	int err;
+	err = sasl_encode(vs->sasl.conn,
+			  (char *)vs->output.buffer,
+			  vs->output.offset,
+			  (const char **)&vs->sasl.encoded,
+			  &vs->sasl.encodedLength);
+	if (err != SASL_OK)
+	    return vnc_client_io_error(vs, -1, EIO);
+
+	vs->sasl.encodedOffset = 0;
+    }
+
+    ret = vnc_client_write_buf(vs,
+			       vs->sasl.encoded + vs->sasl.encodedOffset,
+			       vs->sasl.encodedLength - vs->sasl.encodedOffset);
+    if (!ret)
+	return 0;
+
+    vs->sasl.encodedOffset += ret;
+    if (vs->sasl.encodedOffset == vs->sasl.encodedLength) {
+	vs->output.offset = 0;
+	vs->sasl.encoded = NULL;
+	vs->sasl.encodedOffset = vs->sasl.encodedLength = 0;
+    }
+
+    /* Can't merge this block with one above, because
+     * someone might have written more unencrypted
+     * data in vs->output while we were processing
+     * SASL encoded output
+     */
+    if (vs->output.offset == 0) {
+	qemu_set_fd_handler2(vs->csock, NULL, vnc_client_read, NULL, vs);
+    }
+
+    return ret;
+}
+
+
+long vnc_client_read_sasl(VncState *vs)
+{
+    long ret;
+    uint8_t encoded[4096];
+    const char *decoded;
+    unsigned int decodedLen;
+    int err;
+
+    ret = vnc_client_read_buf(vs, encoded, sizeof(encoded));
+    if (!ret)
+	return 0;
+
+    err = sasl_decode(vs->sasl.conn,
+		      (char *)encoded, ret,
+		      &decoded, &decodedLen);
+
+    if (err != SASL_OK)
+	return vnc_client_io_error(vs, -1, -EIO);
+    VNC_DEBUG("Read SASL Encoded %p size %ld Decoded %p size %d\n",
+	      encoded, ret, decoded, decodedLen);
+    buffer_reserve(&vs->input, decodedLen);
+    buffer_append(&vs->input, decoded, decodedLen);
+    return decodedLen;
+}
+
+
+static int vnc_auth_sasl_check_access(VncState *vs)
+{
+    const void *val;
+    int err;
+
+    err = sasl_getprop(vs->sasl.conn, SASL_USERNAME, &val);
+    if (err != SASL_OK) {
+	VNC_DEBUG("cannot query SASL username on connection %d (%s)\n",
+		  err, sasl_errstring(err, NULL, NULL));
+	return -1;
+    }
+    if (val == NULL) {
+	VNC_DEBUG("no client username was found\n");
+	return -1;
+    }
+    VNC_DEBUG("SASL client username %s\n", (const char *)val);
+
+    vs->sasl.username = qemu_strdup((const char*)val);
+
+    return 0;
+}
+
+static int vnc_auth_sasl_check_ssf(VncState *vs)
+{
+    const void *val;
+    int err, ssf;
+
+    if (!vs->sasl.wantSSF)
+	return 1;
+
+    err = sasl_getprop(vs->sasl.conn, SASL_SSF, &val);
+    if (err != SASL_OK)
+	return 0;
+
+    ssf = *(const int *)val;
+    VNC_DEBUG("negotiated an SSF of %d\n", ssf);
+    if (ssf < 56)
+	return 0; /* 56 is good for Kerberos */
+
+    /* Only setup for read initially, because we're about to send an RPC
+     * reply which must be in plain text. When the next incoming RPC
+     * arrives, we'll switch on writes too
+     *
+     * cf qemudClientReadSASL  in qemud.c
+     */
+    vs->sasl.runSSF = 1;
+
+    /* We have a SSF that's good enough */
+    return 1;
+}
+
+/*
+ * Step Msg
+ *
+ * Input from client:
+ *
+ * u32 clientin-length
+ * u8-array clientin-string
+ *
+ * Output to client:
+ *
+ * u32 serverout-length
+ * u8-array serverout-strin
+ * u8 continue
+ */
+
+static int protocol_client_auth_sasl_step_len(VncState *vs, uint8_t *data, size_t len);
+
+static int protocol_client_auth_sasl_step(VncState *vs, uint8_t *data, size_t len)
+{
+    uint32_t datalen = len;
+    const char *serverout;
+    unsigned int serveroutlen;
+    int err;
+    char *clientdata = NULL;
+
+    /* NB, distinction of NULL vs "" is *critical* in SASL */
+    if (datalen) {
+	clientdata = (char*)data;
+	clientdata[datalen-1] = '\0'; /* Wire includes '\0', but make sure */
+	datalen--; /* Don't count NULL byte when passing to _start() */
+    }
+
+    VNC_DEBUG("Step using SASL Data %p (%d bytes)\n",
+	      clientdata, datalen);
+    err = sasl_server_step(vs->sasl.conn,
+			   clientdata,
+			   datalen,
+			   &serverout,
+			   &serveroutlen);
+    if (err != SASL_OK &&
+	err != SASL_CONTINUE) {
+	VNC_DEBUG("sasl step failed %d (%s)\n",
+		  err, sasl_errdetail(vs->sasl.conn));
+	sasl_dispose(&vs->sasl.conn);
+	vs->sasl.conn = NULL;
+	goto authabort;
+    }
+
+    if (serveroutlen > SASL_DATA_MAX_LEN) {
+	VNC_DEBUG("sasl step reply data too long %d\n",
+		  serveroutlen);
+	sasl_dispose(&vs->sasl.conn);
+	vs->sasl.conn = NULL;
+	goto authabort;
+    }
+
+    VNC_DEBUG("SASL return data %d bytes, nil; %d\n",
+	      serveroutlen, serverout ? 0 : 1);
+
+    if (serveroutlen) {
+	vnc_write_u32(vs, serveroutlen + 1);
+	vnc_write(vs, serverout, serveroutlen + 1);
+    } else {
+	vnc_write_u32(vs, 0);
+    }
+
+    /* Whether auth is complete */
+    vnc_write_u8(vs, err == SASL_CONTINUE ? 0 : 1);
+
+    if (err == SASL_CONTINUE) {
+	VNC_DEBUG("%s", "Authentication must continue\n");
+	/* Wait for step length */
+	vnc_read_when(vs, protocol_client_auth_sasl_step_len, 4);
+    } else {
+	if (!vnc_auth_sasl_check_ssf(vs)) {
+	    VNC_DEBUG("Authentication rejected for weak SSF %d\n", vs->csock);
+	    goto authreject;
+	}
+
+	/* Check username whitelist ACL */
+	if (vnc_auth_sasl_check_access(vs) < 0) {
+	    VNC_DEBUG("Authentication rejected for ACL %d\n", vs->csock);
+	    goto authreject;
+	}
+
+	VNC_DEBUG("Authentication successful %d\n", vs->csock);
+	vnc_write_u32(vs, 0); /* Accept auth */
+	/*
+	 * Delay writing in SSF encoded mode until pending output
+	 * buffer is written
+	 */
+	if (vs->sasl.runSSF)
+	    vs->sasl.waitWriteSSF = vs->output.offset;
+	start_client_init(vs);
+    }
+
+    return 0;
+
+ authreject:
+    vnc_write_u32(vs, 1); /* Reject auth */
+    vnc_write_u32(vs, sizeof("Authentication failed"));
+    vnc_write(vs, "Authentication failed", sizeof("Authentication failed"));
+    vnc_flush(vs);
+    vnc_client_error(vs);
+    return -1;
+
+ authabort:
+    vnc_client_error(vs);
+    return -1;
+}
+
+static int protocol_client_auth_sasl_step_len(VncState *vs, uint8_t *data, size_t len)
+{
+    uint32_t steplen = read_u32(data, 0);
+    VNC_DEBUG("Got client step len %d\n", steplen);
+    if (steplen > SASL_DATA_MAX_LEN) {
+	VNC_DEBUG("Too much SASL data %d\n", steplen);
+	vnc_client_error(vs);
+	return -1;
+    }
+
+    if (steplen == 0)
+	return protocol_client_auth_sasl_step(vs, NULL, 0);
+    else
+	vnc_read_when(vs, protocol_client_auth_sasl_step, steplen);
+    return 0;
+}
+
+/*
+ * Start Msg
+ *
+ * Input from client:
+ *
+ * u32 clientin-length
+ * u8-array clientin-string
+ *
+ * Output to client:
+ *
+ * u32 serverout-length
+ * u8-array serverout-strin
+ * u8 continue
+ */
+
+#define SASL_DATA_MAX_LEN (1024 * 1024)
+
+static int protocol_client_auth_sasl_start(VncState *vs, uint8_t *data, size_t len)
+{
+    uint32_t datalen = len;
+    const char *serverout;
+    unsigned int serveroutlen;
+    int err;
+    char *clientdata = NULL;
+
+    /* NB, distinction of NULL vs "" is *critical* in SASL */
+    if (datalen) {
+	clientdata = (char*)data;
+	clientdata[datalen-1] = '\0'; /* Should be on wire, but make sure */
+	datalen--; /* Don't count NULL byte when passing to _start() */
+    }
+
+    VNC_DEBUG("Start SASL auth with mechanism %s. Data %p (%d bytes)\n",
+	      vs->sasl.mechlist, clientdata, datalen);
+    err = sasl_server_start(vs->sasl.conn,
+			    vs->sasl.mechlist,
+			    clientdata,
+			    datalen,
+			    &serverout,
+			    &serveroutlen);
+    if (err != SASL_OK &&
+	err != SASL_CONTINUE) {
+	VNC_DEBUG("sasl start failed %d (%s)\n",
+		  err, sasl_errdetail(vs->sasl.conn));
+	sasl_dispose(&vs->sasl.conn);
+	vs->sasl.conn = NULL;
+	goto authabort;
+    }
+    if (serveroutlen > SASL_DATA_MAX_LEN) {
+	VNC_DEBUG("sasl start reply data too long %d\n",
+		  serveroutlen);
+	sasl_dispose(&vs->sasl.conn);
+	vs->sasl.conn = NULL;
+	goto authabort;
+    }
+
+    VNC_DEBUG("SASL return data %d bytes, nil; %d\n",
+	      serveroutlen, serverout ? 0 : 1);
+
+    if (serveroutlen) {
+	vnc_write_u32(vs, serveroutlen + 1);
+	vnc_write(vs, serverout, serveroutlen + 1);
+    } else {
+	vnc_write_u32(vs, 0);
+    }
+
+    /* Whether auth is complete */
+    vnc_write_u8(vs, err == SASL_CONTINUE ? 0 : 1);
+
+    if (err == SASL_CONTINUE) {
+	VNC_DEBUG("%s", "Authentication must continue\n");
+	/* Wait for step length */
+	vnc_read_when(vs, protocol_client_auth_sasl_step_len, 4);
+    } else {
+	if (!vnc_auth_sasl_check_ssf(vs)) {
+	    VNC_DEBUG("Authentication rejected for weak SSF %d\n", vs->csock);
+	    goto authreject;
+	}
+
+	/* Check username whitelist ACL */
+	if (vnc_auth_sasl_check_access(vs) < 0) {
+	    VNC_DEBUG("Authentication rejected for ACL %d\n", vs->csock);
+	    goto authreject;
+	}
+
+	VNC_DEBUG("Authentication successful %d\n", vs->csock);
+	vnc_write_u32(vs, 0); /* Accept auth */
+	start_client_init(vs);
+    }
+
+    return 0;
+
+ authreject:
+    vnc_write_u32(vs, 1); /* Reject auth */
+    vnc_write_u32(vs, sizeof("Authentication failed"));
+    vnc_write(vs, "Authentication failed", sizeof("Authentication failed"));
+    vnc_flush(vs);
+    vnc_client_error(vs);
+    return -1;
+
+ authabort:
+    vnc_client_error(vs);
+    return -1;
+}
+
+static int protocol_client_auth_sasl_start_len(VncState *vs, uint8_t *data, size_t len)
+{
+    uint32_t startlen = read_u32(data, 0);
+    VNC_DEBUG("Got client start len %d\n", startlen);
+    if (startlen > SASL_DATA_MAX_LEN) {
+	VNC_DEBUG("Too much SASL data %d\n", startlen);
+	vnc_client_error(vs);
+	return -1;
+    }
+
+    if (startlen == 0)
+	return protocol_client_auth_sasl_start(vs, NULL, 0);
+
+    vnc_read_when(vs, protocol_client_auth_sasl_start, startlen);
+    return 0;
+}
+
+static int protocol_client_auth_sasl_mechname(VncState *vs, uint8_t *data, size_t len)
+{
+    char *mechname = malloc(len + 1);
+    if (!mechname) {
+	VNC_DEBUG("Out of memory reading mechname\n");
+	vnc_client_error(vs);
+    }
+    strncpy(mechname, (char*)data, len);
+    mechname[len] = '\0';
+    VNC_DEBUG("Got client mechname '%s' check against '%s'\n",
+	      mechname, vs->sasl.mechlist);
+
+    if (strncmp(vs->sasl.mechlist, mechname, len) == 0) {
+	if (vs->sasl.mechlist[len] != '\0' &&
+	    vs->sasl.mechlist[len] != ',') {
+	    VNC_DEBUG("One %d", vs->sasl.mechlist[len]);
+	    vnc_client_error(vs);
+	    return -1;
+	}
+    } else {
+	char *offset = strstr(vs->sasl.mechlist, mechname);
+	VNC_DEBUG("Two %p\n", offset);
+	if (!offset) {
+	    vnc_client_error(vs);
+	    return -1;
+	}
+	VNC_DEBUG("Two '%s'\n", offset);
+	if (offset[-1] != ',' ||
+	    (offset[len] != '\0'&&
+	     offset[len] != ',')) {
+	    vnc_client_error(vs);
+	    return -1;
+	}
+    }
+
+    free(vs->sasl.mechlist);
+    vs->sasl.mechlist = mechname;
+
+    VNC_DEBUG("Validated mechname '%s'\n", mechname);
+    vnc_read_when(vs, protocol_client_auth_sasl_start_len, 4);
+    return 0;
+}
+
+static int protocol_client_auth_sasl_mechname_len(VncState *vs, uint8_t *data, size_t len)
+{
+    uint32_t mechlen = read_u32(data, 0);
+    VNC_DEBUG("Got client mechname len %d\n", mechlen);
+    if (mechlen > 100) {
+	VNC_DEBUG("Too long SASL mechname data %d\n", mechlen);
+	vnc_client_error(vs);
+	return -1;
+    }
+    if (mechlen < 1) {
+	VNC_DEBUG("Too short SASL mechname %d\n", mechlen);
+	vnc_client_error(vs);
+	return -1;
+    }
+    vnc_read_when(vs, protocol_client_auth_sasl_mechname,mechlen);
+    return 0;
+}
+
+#define USES_X509_AUTH(vs)			      \
+    ((vs)->subauth == VNC_AUTH_VENCRYPT_X509NONE ||   \
+     (vs)->subauth == VNC_AUTH_VENCRYPT_X509VNC ||    \
+     (vs)->subauth == VNC_AUTH_VENCRYPT_X509PLAIN ||  \
+     (vs)->subauth == VNC_AUTH_VENCRYPT_X509SASL)
+
+
+void start_auth_sasl(VncState *vs)
+{
+    const char *mechlist = NULL;
+    sasl_security_properties_t secprops;
+    int err;
+    char *localAddr, *remoteAddr;
+    int mechlistlen;
+
+    VNC_DEBUG("Initialize SASL auth %d\n", vs->csock);
+
+    /* Get local & remote client addresses in form  IPADDR;PORT */
+    if (!(localAddr = vnc_socket_local_addr("%s;%s", vs->csock)))
+	goto authabort;
+
+    if (!(remoteAddr = vnc_socket_remote_addr("%s;%s", vs->csock))) {
+	free(localAddr);
+	goto authabort;
+    }
+
+    err = sasl_server_new("vnc",
+			  NULL, /* FQDN - just delegates to gethostname */
+			  NULL, /* User realm */
+			  localAddr,
+			  remoteAddr,
+			  NULL, /* Callbacks, not needed */
+			  SASL_SUCCESS_DATA,
+			  &vs->sasl.conn);
+    free(localAddr);
+    free(remoteAddr);
+    localAddr = remoteAddr = NULL;
+
+    if (err != SASL_OK) {
+	VNC_DEBUG("sasl context setup failed %d (%s)",
+		  err, sasl_errstring(err, NULL, NULL));
+	vs->sasl.conn = NULL;
+	goto authabort;
+    }
+
+#ifdef CONFIG_VNC_TLS
+    /* Inform SASL that we've got an external SSF layer from TLS/x509 */
+    if (vs->vd->auth == VNC_AUTH_VENCRYPT &&
+	vs->vd->subauth == VNC_AUTH_VENCRYPT_X509SASL) {
+	gnutls_cipher_algorithm_t cipher;
+	sasl_ssf_t ssf;
+
+	cipher = gnutls_cipher_get(vs->tls.session);
+	if (!(ssf = (sasl_ssf_t)gnutls_cipher_get_key_size(cipher))) {
+	    VNC_DEBUG("%s", "cannot TLS get cipher size\n");
+	    sasl_dispose(&vs->sasl.conn);
+	    vs->sasl.conn = NULL;
+	    goto authabort;
+	}
+	ssf *= 8; /* tls key size is bytes, sasl wants bits */
+
+	err = sasl_setprop(vs->sasl.conn, SASL_SSF_EXTERNAL, &ssf);
+	if (err != SASL_OK) {
+	    VNC_DEBUG("cannot set SASL external SSF %d (%s)\n",
+		      err, sasl_errstring(err, NULL, NULL));
+	    sasl_dispose(&vs->sasl.conn);
+	    vs->sasl.conn = NULL;
+	    goto authabort;
+	}
+    } else
+#endif /* CONFIG_VNC_TLS */
+	vs->sasl.wantSSF = 1;
+
+    memset (&secprops, 0, sizeof secprops);
+    /* Inform SASL that we've got an external SSF layer from TLS */
+    if (strncmp(vs->vd->display, "unix:", 5) == 0
+#ifdef CONFIG_VNC_TLS
+	/* Disable SSF, if using TLS+x509+SASL only. TLS without x509
+	   is not sufficiently strong */
+	|| (vs->vd->auth == VNC_AUTH_VENCRYPT &&
+	    vs->vd->subauth == VNC_AUTH_VENCRYPT_X509SASL)
+#endif /* CONFIG_VNC_TLS */
+	) {
+	/* If we've got TLS or UNIX domain sock, we don't care about SSF */
+	secprops.min_ssf = 0;
+	secprops.max_ssf = 0;
+	secprops.maxbufsize = 8192;
+	secprops.security_flags = 0;
+    } else {
+	/* Plain TCP, better get an SSF layer */
+	secprops.min_ssf = 56; /* Good enough to require kerberos */
+	secprops.max_ssf = 100000; /* Arbitrary big number */
+	secprops.maxbufsize = 8192;
+	/* Forbid any anonymous or trivially crackable auth */
+	secprops.security_flags =
+	    SASL_SEC_NOANONYMOUS | SASL_SEC_NOPLAINTEXT;
+    }
+
+    err = sasl_setprop(vs->sasl.conn, SASL_SEC_PROPS, &secprops);
+    if (err != SASL_OK) {
+	VNC_DEBUG("cannot set SASL security props %d (%s)\n",
+		  err, sasl_errstring(err, NULL, NULL));
+	sasl_dispose(&vs->sasl.conn);
+	vs->sasl.conn = NULL;
+	goto authabort;
+    }
+
+    err = sasl_listmech(vs->sasl.conn,
+			NULL, /* Don't need to set user */
+			"", /* Prefix */
+			",", /* Separator */
+			"", /* Suffix */
+			&mechlist,
+			NULL,
+			NULL);
+    if (err != SASL_OK) {
+	VNC_DEBUG("cannot list SASL mechanisms %d (%s)\n",
+		  err, sasl_errdetail(vs->sasl.conn));
+	sasl_dispose(&vs->sasl.conn);
+	vs->sasl.conn = NULL;
+	goto authabort;
+    }
+    VNC_DEBUG("Available mechanisms for client: '%s'\n", mechlist);
+
+    if (!(vs->sasl.mechlist = strdup(mechlist))) {
+	VNC_DEBUG("Out of memory");
+	sasl_dispose(&vs->sasl.conn);
+	vs->sasl.conn = NULL;
+	goto authabort;
+    }
+    mechlistlen = strlen(mechlist);
+    vnc_write_u32(vs, mechlistlen);
+    vnc_write(vs, mechlist, mechlistlen);
+    vnc_flush(vs);
+
+    VNC_DEBUG("Wait for client mechname length\n");
+    vnc_read_when(vs, protocol_client_auth_sasl_mechname_len, 4);
+
+    return;
+
+ authabort:
+    vnc_client_error(vs);
+    return;
+}
+
+
diff --git a/vnc-auth-sasl.h b/vnc-auth-sasl.h
new file mode 100644
index 000000000..a72973a26
--- /dev/null
+++ b/vnc-auth-sasl.h
@@ -0,0 +1,67 @@
+/*
+ * QEMU VNC display driver: SASL auth protocol
+ *
+ * Copyright (C) 2009 Red Hat, Inc
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+
+#ifndef __QEMU_VNC_AUTH_SASL_H__
+#define __QEMU_VNC_AUTH_SASL_H__
+
+
+#include <sasl/sasl.h>
+
+typedef struct VncStateSASL VncStateSASL;
+
+struct VncStateSASL {
+    sasl_conn_t *conn;
+    /* If we want to negotiate an SSF layer with client */
+    int wantSSF :1;
+    /* If we are now running the SSF layer */
+    int runSSF :1;
+    /*
+     * If this is non-zero, then wait for that many bytes
+     * to be written plain, before switching to SSF encoding
+     * This allows the VNC auth result to finish being
+     * written in plain.
+     */
+    unsigned int waitWriteSSF;
+
+    /*
+     * Buffering encoded data to allow more clear data
+     * to be stuffed onto the output buffer
+     */
+    const uint8_t *encoded;
+    unsigned int encodedLength;
+    unsigned int encodedOffset;
+    char *username;
+    char *mechlist;
+};
+
+void vnc_sasl_client_cleanup(VncState *vs);
+
+long vnc_client_read_sasl(VncState *vs);
+long vnc_client_write_sasl(VncState *vs);
+
+void start_auth_sasl(VncState *vs);
+
+#endif /* __QEMU_VNC_AUTH_SASL_H__ */
+
diff --git a/vnc.c b/vnc.c
index f4d8fe60e..074238790 100644
--- a/vnc.c
+++ b/vnc.c
@@ -68,7 +68,8 @@ static char *addr_to_string(const char *format,
     return addr;
 }
 
-static char *vnc_socket_local_addr(const char *format, int fd) {
+
+char *vnc_socket_local_addr(const char *format, int fd) {
     struct sockaddr_storage sa;
     socklen_t salen;
 
@@ -79,7 +80,8 @@ static char *vnc_socket_local_addr(const char *format, int fd) {
     return addr_to_string(format, &sa, salen);
 }
 
-static char *vnc_socket_remote_addr(const char *format, int fd) {
+
+char *vnc_socket_remote_addr(const char *format, int fd) {
     struct sockaddr_storage sa;
     socklen_t salen;
 
@@ -125,12 +127,18 @@ static const char *vnc_auth_name(VncDisplay *vd) {
             return "vencrypt+x509+vnc";
         case VNC_AUTH_VENCRYPT_X509PLAIN:
             return "vencrypt+x509+plain";
+	case VNC_AUTH_VENCRYPT_TLSSASL:
+	    return "vencrypt+tls+sasl";
+	case VNC_AUTH_VENCRYPT_X509SASL:
+	    return "vencrypt+x509+sasl";
         default:
             return "vencrypt";
         }
 #else
         return "vencrypt";
 #endif
+    case VNC_AUTH_SASL:
+	return "sasl";
     }
     return "unknown";
 }
@@ -278,7 +286,7 @@ static void vnc_framebuffer_update(VncState *vs, int x, int y, int w, int h,
     vnc_write_s32(vs, encoding);
 }
 
-static void buffer_reserve(Buffer *buffer, size_t len)
+void buffer_reserve(Buffer *buffer, size_t len)
 {
     if ((buffer->capacity - buffer->offset) < len) {
 	buffer->capacity += (len + 1024);
@@ -290,22 +298,22 @@ static void buffer_reserve(Buffer *buffer, size_t len)
     }
 }
 
-static int buffer_empty(Buffer *buffer)
+int buffer_empty(Buffer *buffer)
 {
     return buffer->offset == 0;
 }
 
-static uint8_t *buffer_end(Buffer *buffer)
+uint8_t *buffer_end(Buffer *buffer)
 {
     return buffer->buffer + buffer->offset;
 }
 
-static void buffer_reset(Buffer *buffer)
+void buffer_reset(Buffer *buffer)
 {
 	buffer->offset = 0;
 }
 
-static void buffer_append(Buffer *buffer, const void *data, size_t len)
+void buffer_append(Buffer *buffer, const void *data, size_t len)
 {
     memcpy(buffer->buffer + buffer->offset, data, len);
     buffer->offset += len;
@@ -822,7 +830,8 @@ static void audio_del(VncState *vs)
     }
 }
 
-static int vnc_client_io_error(VncState *vs, int ret, int last_errno)
+
+int vnc_client_io_error(VncState *vs, int ret, int last_errno)
 {
     if (ret == 0 || ret == -1) {
         if (ret == -1) {
@@ -848,6 +857,9 @@ static int vnc_client_io_error(VncState *vs, int ret, int last_errno)
 #ifdef CONFIG_VNC_TLS
 	vnc_tls_client_cleanup(vs);
 #endif /* CONFIG_VNC_TLS */
+#ifdef CONFIG_VNC_SASL
+        vnc_sasl_client_cleanup(vs);
+#endif /* CONFIG_VNC_SASL */
         audio_del(vs);
 
         VncState *p, *parent = NULL;
@@ -878,14 +890,28 @@ void vnc_client_error(VncState *vs)
     vnc_client_io_error(vs, -1, EINVAL);
 }
 
-void vnc_client_write(void *opaque)
+
+/*
+ * Called to write a chunk of data to the client socket. The data may
+ * be the raw data, or may have already been encoded by SASL.
+ * The data will be written either straight onto the socket, or
+ * written via the GNUTLS wrappers, if TLS/SSL encryption is enabled
+ *
+ * NB, it is theoretically possible to have 2 layers of encryption,
+ * both SASL, and this TLS layer. It is highly unlikely in practice
+ * though, since SASL encryption will typically be a no-op if TLS
+ * is active
+ *
+ * Returns the number of bytes written, which may be less than
+ * the requested 'datalen' if the socket would block. Returns
+ * -1 on error, and disconnects the client socket.
+ */
+long vnc_client_write_buf(VncState *vs, const uint8_t *data, size_t datalen)
 {
     long ret;
-    VncState *vs = opaque;
-
 #ifdef CONFIG_VNC_TLS
     if (vs->tls.session) {
-	ret = gnutls_write(vs->tls.session, vs->output.buffer, vs->output.offset);
+	ret = gnutls_write(vs->tls.session, data, datalen);
 	if (ret < 0) {
 	    if (ret == GNUTLS_E_AGAIN)
 		errno = EAGAIN;
@@ -895,10 +921,42 @@ void vnc_client_write(void *opaque)
 	}
     } else
 #endif /* CONFIG_VNC_TLS */
-	ret = send(vs->csock, vs->output.buffer, vs->output.offset, 0);
-    ret = vnc_client_io_error(vs, ret, socket_error());
+	ret = send(vs->csock, data, datalen, 0);
+    VNC_DEBUG("Wrote wire %p %d -> %ld\n", data, datalen, ret);
+    return vnc_client_io_error(vs, ret, socket_error());
+}
+
+
+/*
+ * Called to write buffered data to the client socket, when not
+ * using any SASL SSF encryption layers. Will write as much data
+ * as possible without blocking. If all buffered data is written,
+ * will switch the FD poll() handler back to read monitoring.
+ *
+ * Returns the number of bytes written, which may be less than
+ * the buffered output data if the socket would block. Returns
+ * -1 on error, and disconnects the client socket.
+ */
+static long vnc_client_write_plain(VncState *vs)
+{
+    long ret;
+
+#ifdef CONFIG_VNC_SASL
+    VNC_DEBUG("Write Plain: Pending output %p size %d offset %d. Wait SSF %d\n",
+              vs->output.buffer, vs->output.capacity, vs->output.offset,
+              vs->sasl.waitWriteSSF);
+
+    if (vs->sasl.conn &&
+        vs->sasl.runSSF &&
+        vs->sasl.waitWriteSSF) {
+        ret = vnc_client_write_buf(vs, vs->output.buffer, vs->sasl.waitWriteSSF);
+        if (ret)
+            vs->sasl.waitWriteSSF -= ret;
+    } else
+#endif /* CONFIG_VNC_SASL */
+        ret = vnc_client_write_buf(vs, vs->output.buffer, vs->output.offset);
     if (!ret)
-	return;
+        return 0;
 
     memmove(vs->output.buffer, vs->output.buffer + ret, (vs->output.offset - ret));
     vs->output.offset -= ret;
@@ -906,6 +964,29 @@ void vnc_client_write(void *opaque)
     if (vs->output.offset == 0) {
 	qemu_set_fd_handler2(vs->csock, NULL, vnc_client_read, NULL, vs);
     }
+
+    return ret;
+}
+
+
+/*
+ * First function called whenever there is data to be written to
+ * the client socket. Will delegate actual work according to whether
+ * SASL SSF layers are enabled (thus requiring encryption calls)
+ */
+void vnc_client_write(void *opaque)
+{
+    long ret;
+    VncState *vs = opaque;
+
+#ifdef CONFIG_VNC_SASL
+    if (vs->sasl.conn &&
+        vs->sasl.runSSF &&
+        !vs->sasl.waitWriteSSF)
+        ret = vnc_client_write_sasl(vs);
+    else
+#endif /* CONFIG_VNC_SASL */
+        ret = vnc_client_write_plain(vs);
 }
 
 void vnc_read_when(VncState *vs, VncReadEvent *func, size_t expecting)
@@ -914,16 +995,28 @@ void vnc_read_when(VncState *vs, VncReadEvent *func, size_t expecting)
     vs->read_handler_expect = expecting;
 }
 
-void vnc_client_read(void *opaque)
+
+/*
+ * Called to read a chunk of data from the client socket. The data may
+ * be the raw data, or may need to be further decoded by SASL.
+ * The data will be read either straight from to the socket, or
+ * read via the GNUTLS wrappers, if TLS/SSL encryption is enabled
+ *
+ * NB, it is theoretically possible to have 2 layers of encryption,
+ * both SASL, and this TLS layer. It is highly unlikely in practice
+ * though, since SASL encryption will typically be a no-op if TLS
+ * is active
+ *
+ * Returns the number of bytes read, which may be less than
+ * the requested 'datalen' if the socket would block. Returns
+ * -1 on error, and disconnects the client socket.
+ */
+long vnc_client_read_buf(VncState *vs, uint8_t *data, size_t datalen)
 {
-    VncState *vs = opaque;
     long ret;
-
-    buffer_reserve(&vs->input, 4096);
-
 #ifdef CONFIG_VNC_TLS
     if (vs->tls.session) {
-	ret = gnutls_read(vs->tls.session, buffer_end(&vs->input), 4096);
+	ret = gnutls_read(vs->tls.session, data, datalen);
 	if (ret < 0) {
 	    if (ret == GNUTLS_E_AGAIN)
 		errno = EAGAIN;
@@ -933,12 +1026,52 @@ void vnc_client_read(void *opaque)
 	}
     } else
 #endif /* CONFIG_VNC_TLS */
-	ret = recv(vs->csock, buffer_end(&vs->input), 4096, 0);
-    ret = vnc_client_io_error(vs, ret, socket_error());
-    if (!ret)
-	return;
+	ret = recv(vs->csock, data, datalen, 0);
+    VNC_DEBUG("Read wire %p %d -> %ld\n", data, datalen, ret);
+    return vnc_client_io_error(vs, ret, socket_error());
+}
 
+
+/*
+ * Called to read data from the client socket to the input buffer,
+ * when not using any SASL SSF encryption layers. Will read as much
+ * data as possible without blocking.
+ *
+ * Returns the number of bytes read. Returns -1 on error, and
+ * disconnects the client socket.
+ */
+static long vnc_client_read_plain(VncState *vs)
+{
+    int ret;
+    VNC_DEBUG("Read plain %p size %d offset %d\n",
+              vs->input.buffer, vs->input.capacity, vs->input.offset);
+    buffer_reserve(&vs->input, 4096);
+    ret = vnc_client_read_buf(vs, buffer_end(&vs->input), 4096);
+    if (!ret)
+        return 0;
     vs->input.offset += ret;
+    return ret;
+}
+
+
+/*
+ * First function called whenever there is more data to be read from
+ * the client socket. Will delegate actual work according to whether
+ * SASL SSF layers are enabled (thus requiring decryption calls)
+ */
+void vnc_client_read(void *opaque)
+{
+    VncState *vs = opaque;
+    long ret;
+
+#ifdef CONFIG_VNC_SASL
+    if (vs->sasl.conn && vs->sasl.runSSF)
+        ret = vnc_client_read_sasl(vs);
+    else
+#endif /* CONFIG_VNC_SASL */
+        ret = vnc_client_read_plain(vs);
+    if (!ret)
+	return;
 
     while (vs->read_handler && vs->input.offset >= vs->read_handler_expect) {
 	size_t len = vs->read_handler_expect;
@@ -1723,6 +1856,13 @@ static int protocol_client_auth(VncState *vs, uint8_t *data, size_t len)
            break;
 #endif /* CONFIG_VNC_TLS */
 
+#ifdef CONFIG_VNC_SASL
+       case VNC_AUTH_SASL:
+           VNC_DEBUG("Accept SASL auth\n");
+           start_auth_sasl(vs);
+           break;
+#endif /* CONFIG_VNC_SASL */
+
        default: /* Should not be possible, but just in case */
            VNC_DEBUG("Reject auth %d\n", vs->vd->auth);
            vnc_write_u8(vs, 1);
@@ -1924,6 +2064,10 @@ int vnc_display_open(DisplayState *ds, const char *display)
 #ifdef CONFIG_VNC_TLS
     int tls = 0, x509 = 0;
 #endif
+#ifdef CONFIG_VNC_SASL
+    int sasl = 0;
+    int saslErr;
+#endif
 
     if (!vnc_display)
         return -1;
@@ -1943,6 +2087,10 @@ int vnc_display_open(DisplayState *ds, const char *display)
 	    reverse = 1;
 	} else if (strncmp(options, "to=", 3) == 0) {
             to_port = atoi(options+3) + 5900;
+#ifdef CONFIG_VNC_SASL
+	} else if (strncmp(options, "sasl", 4) == 0) {
+	    sasl = 1; /* Require SASL auth */
+#endif
 #ifdef CONFIG_VNC_TLS
 	} else if (strncmp(options, "tls", 3) == 0) {
 	    tls = 1; /* Require TLS */
@@ -1979,6 +2127,22 @@ int vnc_display_open(DisplayState *ds, const char *display)
 	}
     }
 
+    /*
+     * Combinations we support here:
+     *
+     *  - no-auth                (clear text, no auth)
+     *  - password               (clear text, weak auth)
+     *  - sasl                   (encrypt, good auth *IF* using Kerberos via GSSAPI)
+     *  - tls                    (encrypt, weak anonymous creds, no auth)
+     *  - tls + password         (encrypt, weak anonymous creds, weak auth)
+     *  - tls + sasl             (encrypt, weak anonymous creds, good auth)
+     *  - tls + x509             (encrypt, good x509 creds, no auth)
+     *  - tls + x509 + password  (encrypt, good x509 creds, weak auth)
+     *  - tls + x509 + sasl      (encrypt, good x509 creds, good auth)
+     *
+     * NB1. TLS is a stackable auth scheme.
+     * NB2. the x509 schemes have option to validate a client cert dname
+     */
     if (password) {
 #ifdef CONFIG_VNC_TLS
 	if (tls) {
@@ -1991,13 +2155,34 @@ int vnc_display_open(DisplayState *ds, const char *display)
 		vs->subauth = VNC_AUTH_VENCRYPT_TLSVNC;
 	    }
 	} else {
-#endif
+#endif /* CONFIG_VNC_TLS */
 	    VNC_DEBUG("Initializing VNC server with password auth\n");
 	    vs->auth = VNC_AUTH_VNC;
 #ifdef CONFIG_VNC_TLS
 	    vs->subauth = VNC_AUTH_INVALID;
 	}
-#endif
+#endif /* CONFIG_VNC_TLS */
+#ifdef CONFIG_VNC_SASL
+    } else if (sasl) {
+#ifdef CONFIG_VNC_TLS
+        if (tls) {
+            vs->auth = VNC_AUTH_VENCRYPT;
+            if (x509) {
+		VNC_DEBUG("Initializing VNC server with x509 SASL auth\n");
+                vs->subauth = VNC_AUTH_VENCRYPT_X509SASL;
+            } else {
+		VNC_DEBUG("Initializing VNC server with TLS SASL auth\n");
+                vs->subauth = VNC_AUTH_VENCRYPT_TLSSASL;
+            }
+        } else {
+#endif /* CONFIG_VNC_TLS */
+	    VNC_DEBUG("Initializing VNC server with SASL auth\n");
+            vs->auth = VNC_AUTH_SASL;
+#ifdef CONFIG_VNC_TLS
+            vs->subauth = VNC_AUTH_INVALID;
+        }
+#endif /* CONFIG_VNC_TLS */
+#endif /* CONFIG_VNC_SASL */
     } else {
 #ifdef CONFIG_VNC_TLS
 	if (tls) {
@@ -2019,6 +2204,16 @@ int vnc_display_open(DisplayState *ds, const char *display)
 #endif
     }
 
+#ifdef CONFIG_VNC_SASL
+    if ((saslErr = sasl_server_init(NULL, "qemu")) != SASL_OK) {
+        fprintf(stderr, "Failed to initialize SASL auth %s",
+                sasl_errstring(saslErr, NULL, NULL));
+        free(vs->display);
+        vs->display = NULL;
+        return -1;
+    }
+#endif
+
     if (reverse) {
         /* connect to viewer */
         if (strncmp(display, "unix:", 5) == 0)
diff --git a/vnc.h b/vnc.h
index b5ae1f951..59a1b4ab9 100644
--- a/vnc.h
+++ b/vnc.h
@@ -80,6 +80,10 @@ typedef struct VncDisplay VncDisplay;
 #include "vnc-tls.h"
 #include "vnc-auth-vencrypt.h"
 #endif
+#ifdef CONFIG_VNC_SASL
+#include "vnc-auth-sasl.h"
+#endif
+
 
 struct VncDisplay
 {
@@ -119,10 +123,12 @@ struct VncState
     int minor;
 
     char challenge[VNC_AUTH_CHALLENGE_SIZE];
-
 #ifdef CONFIG_VNC_TLS
     VncStateTLS tls;
 #endif
+#ifdef CONFIG_VNC_SASL
+    VncStateSASL sasl;
+#endif
 
     Buffer output;
     Buffer input;
@@ -161,8 +167,9 @@ enum {
     VNC_AUTH_RA2NE = 6,
     VNC_AUTH_TIGHT = 16,
     VNC_AUTH_ULTRA = 17,
-    VNC_AUTH_TLS = 18,
-    VNC_AUTH_VENCRYPT = 19
+    VNC_AUTH_TLS = 18,      /* Supported in GTK-VNC & VINO */
+    VNC_AUTH_VENCRYPT = 19, /* Supported in GTK-VNC & VeNCrypt */
+    VNC_AUTH_SASL = 20,     /* Supported in GTK-VNC & VINO */
 };
 
 enum {
@@ -173,6 +180,8 @@ enum {
     VNC_AUTH_VENCRYPT_X509NONE = 260,
     VNC_AUTH_VENCRYPT_X509VNC = 261,
     VNC_AUTH_VENCRYPT_X509PLAIN = 262,
+    VNC_AUTH_VENCRYPT_X509SASL = 263,
+    VNC_AUTH_VENCRYPT_TLSSASL = 264,
 };
 
 
@@ -256,6 +265,8 @@ enum {
 void vnc_client_read(void *opaque);
 void vnc_client_write(void *opaque);
 
+long vnc_client_read_buf(VncState *vs, uint8_t *data, size_t datalen);
+long vnc_client_write_buf(VncState *vs, const uint8_t *data, size_t datalen);
 
 /* Protocol I/O functions */
 void vnc_write(VncState *vs, const void *data, size_t len);
@@ -275,8 +286,22 @@ uint32_t read_u32(uint8_t *data, size_t offset);
 
 /* Protocol stage functions */
 void vnc_client_error(VncState *vs);
+int vnc_client_io_error(VncState *vs, int ret, int last_errno);
 
 void start_client_init(VncState *vs);
 void start_auth_vnc(VncState *vs);
 
+/* Buffer management */
+void buffer_reserve(Buffer *buffer, size_t len);
+int buffer_empty(Buffer *buffer);
+uint8_t *buffer_end(Buffer *buffer);
+void buffer_reset(Buffer *buffer);
+void buffer_append(Buffer *buffer, const void *data, size_t len);
+
+
+/* Misc helpers */
+
+char *vnc_socket_local_addr(const char *format, int fd);
+char *vnc_socket_remote_addr(const char *format, int fd);
+
 #endif /* __QEMU_VNC_H */