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, 34 insertions, 0 deletions

diff --git a/qemu.sasl b/qemu.sasl
new file mode 100644
index 0000000000..cf19cf8d07
--- /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
+