Re: [Qemu-devel] [PATCH v3 10/10] vnc: allow specifying a custom ACL object name

[Eric Blake <eblake@redhat.com>]

[-- Attachment #1: Type: text/plain, Size: 5342 bytes --]

On 03/10/2016 11:59 AM, Daniel P. Berrange wrote:
> 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=acl0,policy=deny,\
>                   rules.0.match=O=RedHat,,L=London,rules.0.policy=allow \
>           -object authz-simple,id=acl0,policy=deny,\

Umm, you can't reuse 'acl0' as the id.

>                   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 \

And this fails because the ids don't exist.  I think you meant
authz-simple,id=tlsacl0 in the first instance, and
authz-simple,id=saslacl0 in the second instance.

>           ...other QEMU args...
> 
> Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
> ---
>  ui/vnc.c | 73 ++++++++++++++++++++++++++++++++++++++++++++++++++++------------
>  1 file changed, 60 insertions(+), 13 deletions(-)
> 
> @@ -3670,6 +3680,21 @@ 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;
> +    }
> +
> +#ifdef CONFIG_VNC_SASL
> +    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;
> +    }
> +#endif

Do we explicitly fail if sasl-acl was provided but CONFIG_VNC_SASL is
not defined?  It looks here like you silently ignore it, which would not
be good.

> @@ -3710,19 +3737,39 @@ 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
>  

Again, the saslacl check is only mentioned inside the #if; what happens
when the #if is not compiled?

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 604 bytes --]