[Qemu-devel] [PATCH v4 10/10] vnc: allow specifying a custom ACL object name

["Daniel P. Berrange" <berrange@redhat.com>]

The VNC server has historically had support for ACLs to check
both the SASL username and the TLS x509 distinguished name.
The VNC server was responsible for creating the initial ACL,
and the client app was then responsible for populating it with
rules using the HMP 'acl_add' command.

This is not satisfactory for a variety of reasons. There is
no way to populate the ACLs from the command line, users are
forced to use the HMP. With multiple network services all
supporting TLS and ACLs now, it is desirable to be able to
define a single ACL that is referenced by all services.

To address these limitations, two new options are added to the
VNC server CLI. The 'tls-acl' option takes the ID of a QAuthZ
object to use for checking TLS x509 distinguished names, and
the 'sasl-acl' option takes the ID of another object to use for
checking SASL usernames.

In this example, we setup two ACLs. The first allows any client
with a certificate issued by the 'RedHat' organization in the
'London' locality. The second ACL allows clients with either
the 'joe@REDHAT.COM' or  'fred@REDHAT.COM' kerberos usernames.
Both ACLs must pass for the user to be allowed.

    $QEMU -object tls-creds-x509,id=tls0,dir=/home/berrange/qemutls,\
                  endpoint=server,verify-peer=yes \
          -object authz-simple,id=tlsacl0,policy=deny,\
                  rules.0.match=O=RedHat,,L=London,rules.0.policy=allow \
          -object authz-simple,id=saslacl0,policy=deny,\
                  rules.0.match=fred@REDHAT.COM,rules.0.policy=allow \
                  rules.0.match=joe@REDHAT.COM,rules.0.policy=allow \
          -vnc 0.0.0.0:1,tls-creds=tls0,tls-acl=tlsacl0,
	       sasl,sasl-acl=saslacl0 \
          ...other QEMU args...

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
---
 ui/vnc.c | 77 +++++++++++++++++++++++++++++++++++++++++++++++++++++-----------
 1 file changed, 64 insertions(+), 13 deletions(-)

diff --git a/ui/vnc.c b/ui/vnc.c
index ba07715..939c3d3 100644
--- a/ui/vnc.c
+++ b/ui/vnc.c
@@ -3263,6 +3263,12 @@ static QemuOptsList qemu_vnc_opts = {
             .name = "acl",
             .type = QEMU_OPT_BOOL,
         },{
+            .name = "tls-acl",
+            .type = QEMU_OPT_STRING,
+        },{
+            .name = "sasl-acl",
+            .type = QEMU_OPT_STRING,
+        },{
             .name = "lossy",
             .type = QEMU_OPT_BOOL,
         },{
@@ -3485,6 +3491,8 @@ void vnc_display_open(const char *id, Error **errp)
     int saslErr;
 #endif
     int acl = 0;
+    const char *tlsacl;
+    const char *saslacl;
     int lock_key_sync = 1;
 
     if (!vs) {
@@ -3672,6 +3680,27 @@ void vnc_display_open(const char *id, Error **errp)
         }
     }
     acl = qemu_opt_get_bool(opts, "acl", false);
+    tlsacl = qemu_opt_get(opts, "tls-acl");
+    if (acl && tlsacl) {
+        error_setg(errp, "'acl' option is mutually exclusive with the "
+                   "'tls-acl' options");
+        goto fail;
+    }
+    if (tlsacl && !vs->tlscreds) {
+        error_setg(errp, "'tls-acl' provided but TLS is not enabled");
+        goto fail;
+    }
+
+    saslacl = qemu_opt_get(opts, "sasl-acl");
+    if (acl && saslacl) {
+        error_setg(errp, "'acl' option is mutually exclusive with the "
+                   "'sasl-acl' options");
+        goto fail;
+    }
+    if (saslacl && !sasl) {
+        error_setg(errp, "'sasl-acl' provided but SASL auth is not enabled");
+        goto fail;
+    }
 
     share = qemu_opt_get(opts, "share");
     if (share) {
@@ -3701,7 +3730,9 @@ void vnc_display_open(const char *id, Error **errp)
         vs->non_adaptive = true;
     }
 
-    if (acl) {
+    if (tlsacl) {
+        vs->tlsaclname = g_strdup(tlsacl);
+    } else if (acl) {
         if (strcmp(vs->id, "default") == 0) {
             vs->tlsaclname = g_strdup("vnc.x509dname");
         } else {
@@ -3712,19 +3743,39 @@ void vnc_display_open(const char *id, Error **errp)
                           &error_abort);
     }
 #ifdef CONFIG_VNC_SASL
-    if (acl && sasl) {
-        char *aclname;
+    if (sasl) {
+        if (saslacl) {
+            Object *container, *acl;
+            container = object_get_objects_root();
+            acl = object_resolve_path_component(container, saslacl);
+            if (!acl) {
+                error_setg(errp, "Cannot find ACL %s", saslacl);
+                goto fail;
+            }
 
-        if (strcmp(vs->id, "default") == 0) {
-            aclname = g_strdup("vnc.username");
-        } else {
-            aclname = g_strdup_printf("vnc.%s.username", vs->id);
-        }
-        vs->sasl.acl =
-            QAUTHZ(qauthz_simple_new(aclname,
-                                     QAUTHZ_SIMPLE_POLICY_DENY,
-                                     &error_abort));
-        g_free(aclname);
+            if (!object_dynamic_cast(acl, TYPE_QAUTHZ)) {
+                error_setg(errp, "Object '%s' is not a QAuthZ subclass",
+                           saslacl);
+                goto fail;
+            }
+            vs->sasl.acl = QAUTHZ(acl);
+        } else if (acl) {
+            char *aclname;
+
+            if (strcmp(vs->id, "default") == 0) {
+                aclname = g_strdup("vnc.username");
+            } else {
+                aclname = g_strdup_printf("vnc.%s.username", vs->id);
+            }
+            vs->sasl.acl =
+                QAUTHZ(qauthz_simple_new(aclname,
+                                         QAUTHZ_SIMPLE_POLICY_DENY,
+                                         &error_abort));
+            g_free(aclname);
+        }
+    } else if (saslacl) {
+        error_setg(errp, "SASL ACL provided when SASL is disabled");
+        goto fail;
     }
 #endif
 
-- 
2.5.5