Support ACLs for controlling VNC access ("Daniel P. Berrange")

This patch introduces a generic internal API for access control lists
to be used by network servers in QEMU. It adds support for checking
these ACL in the VNC server, in two places. The first ACL is for the
SASL authentication mechanism, checking the SASL username. This ACL
is called 'vnc.username'. The second is for the TLS authentication
mechanism, when x509 client certificates are turned on, checking against
the Distinguished Name of the client. This ACL is called 'vnc.x509dname'

The internal API provides for an ACL with the following characteristics

 - A unique name, eg  vnc.username, and vnc.x509dname.
 - A default policy, allow or deny
 - An ordered series of match rules, with allow or deny policy

If none of the match rules apply, then the default policy is
used.

There is a monitor API to manipulate the ACLs, which I'll describe via
examples

  (qemu) acl show vnc.username
  policy: allow
  (qemu) acl policy vnc.username denya
  acl: policy set to 'deny'
  (qemu) acl allow vnc.username fred
  acl: added rule at position 1
  (qemu) acl allow vnc.username bob
  acl: added rule at position 2
  (qemu) acl allow vnc.username joe 1
  acl: added rule at position 1
  (qemu) acl show vnc.username
  policy: deny
  0: allow fred
  1: allow joe
  2: allow bob


  (qemu) acl show vnc.x509dname
  policy: allow
  (qemu) acl policy vnc.x509dname deny
  acl: policy set to 'deny'
  (qemu) acl allow vnc.x509dname C=GB,O=ACME,L=London,CN=*
  acl: added rule at position 1
  (qemu) acl allow vnc.x509dname C=GB,O=ACME,L=Boston,CN=bob
  acl: added rule at position 2
  (qemu) acl show vnc.x509dname
  policy: deny
  0: allow C=GB,O=ACME,L=London,CN=*
  1: allow C=GB,O=ACME,L=Boston,CN=bob

By default the VNC server will not use any ACLs, allowing access to
the server if the user successfully authenticates. To enable use of
ACLs to restrict user access, the ',acl' flag should be given when
starting QEMU. The initial ACL activated will be a 'deny all' policy
and should be customized using monitor commands.

eg enable SASL auth and ACLs

    qemu ....  -vnc localhost:1,sasl,acl

The next patch will provide a way to load a pre-defined ACL when
starting up


 Makefile        |    6 +
 b/acl.c         |  185 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 b/acl.h         |   74 ++++++++++++++++++++++
 configure       |   18 +++++
 monitor.c       |   95 ++++++++++++++++++++++++++++
 qemu-doc.texi   |   49 ++++++++++++++
 vnc-auth-sasl.c |   16 +++-
 vnc-auth-sasl.h |    7 ++
 vnc-tls.c       |   19 +++++
 vnc-tls.h       |    3 
 vnc.c           |   21 ++++++
 vnc.h           |    3 
 12 files changed, 491 insertions(+), 5 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@6726 c046a42c-6fe2-441c-8c8c-71466251a162

1 files changed, 13 insertions, 3 deletions

diff --git a/vnc-auth-sasl.c b/vnc-auth-sasl.c
index 2882a35..4b4aca9 100644
--- a/vnc-auth-sasl.c
+++ b/vnc-auth-sasl.c
@@ -120,22 +120,32 @@ static int vnc_auth_sasl_check_access(VncState *vs)
 {
     const void *val;
     int err;
+    int allow;
 
     err = sasl_getprop(vs->sasl.conn, SASL_USERNAME, &val);
     if (err != SASL_OK) {
-	VNC_DEBUG("cannot query SASL username on connection %d (%s)\n",
+	VNC_DEBUG("cannot query SASL username on connection %d (%s), denying access\n",
 		  err, sasl_errstring(err, NULL, NULL));
 	return -1;
     }
     if (val == NULL) {
-	VNC_DEBUG("no client username was found\n");
+	VNC_DEBUG("no client username was found, denying access\n");
 	return -1;
     }
     VNC_DEBUG("SASL client username %s\n", (const char *)val);
 
     vs->sasl.username = qemu_strdup((const char*)val);
 
-    return 0;
+    if (vs->vd->sasl.acl == NULL) {
+	VNC_DEBUG("no ACL activated, allowing access\n");
+	return 0;
+    }
+
+    allow = qemu_acl_party_is_allowed(vs->vd->sasl.acl, vs->sasl.username);
+
+    VNC_DEBUG("SASL client %s %s by ACL\n", vs->sasl.username,
+	      allow ? "allowed" : "denied");
+    return allow ? 0 : -1;
 }
 
 static int vnc_auth_sasl_check_ssf(VncState *vs)