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

1 files changed, 67 insertions, 0 deletions

diff --git a/vnc-auth-sasl.h b/vnc-auth-sasl.h
new file mode 100644
index 0000000..a72973a
--- /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__ */
+