commit fd4a5fd4639bb1bfd04144fca85856d825e00ab4
author Daniel P. Berrange <berrange@redhat.com> Fri Mar 08 15:21:50 2019 +0000
committer Paolo Bonzini <pbonzini@redhat.com> Mon Mar 11 16:55:52 2019 +0100
tree a1fa2d9bd117b40e406a8bf1f8c476be5838b287
parent 611dbe46093d901cf01c1b252dd39441b95d1c35

chardev: add support for authorization for TLS clients

Currently any client which can complete the TLS handshake is able to use
a chardev server. The server admin can turn on the 'verify-peer' option
for the x509 creds to require the client to provide a x509
certificate. This means the client will have to acquire a certificate
from the CA before they are permitted to use the chardev server. This is
still a fairly low bar.

This adds a 'tls-authz=OBJECT-ID' option to the socket chardev backend
which takes the ID of a previously added 'QAuthZ' object instance. This
will be used to validate the client's x509 distinguished name. Clients
failing the check will not be permitted to use the chardev server.

For example to setup authorization that only allows connection from a
client whose x509 certificate distinguished name contains 'CN=fred', you
would use:

  $QEMU -object tls-creds-x509,id=tls0,dir=/home/berrange/qemutls,\
                endpoint=server,verify-peer=yes \
        -object authz-simple,id=authz0,identity=CN=laptop.example.com,,\
                O=Example Org,,L=London,,ST=London,,C=GB \
        -chardev socket,host=127.0.0.1,port=9000,server,\
	         tls-creds=tls0,tls-authz=authz0 \
        ...other qemu args...

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>

chardev/char-socket.c

diff --git a/chardev/char-socket.c b/chardev/char-socket.c
index 6d287ba..3916505 100644
--- a/chardev/char-socket.c
+++ b/chardev/char-socket.c
@@ -59,6 +59,7 @@
     QIONetListener *listener;
     GSource *hup_source;
     QCryptoTLSCreds *tls_creds;
+    char *tls_authz;
     TCPChardevState state;
     int max_size;
     int do_telnetopt;
@@ -807,7 +808,7 @@
     if (s->is_listen) {
         tioc = qio_channel_tls_new_server(
             s->ioc, s->tls_creds,
-            NULL, /* XXX Use an ACL */
+            s->tls_authz,
             &err);
     } else {
         tioc = qio_channel_tls_new_client(
@@ -1055,6 +1056,7 @@
     if (s->tls_creds) {
         object_unref(OBJECT(s->tls_creds));
     }
+    g_free(s->tls_authz);
 
     qemu_chr_be_event(chr, CHR_EVENT_CLOSED);
 }
@@ -1242,6 +1244,11 @@
         break;
     }
 
+    if (sock->has_tls_authz && !sock->has_tls_creds) {
+        error_setg(errp, "'tls_authz' option requires 'tls_creds' option");
+        return false;
+    }
+
     /* Validate any options which have a dependancy on client vs server */
     if (!sock->has_server || sock->server) {
         if (sock->has_reconnect) {
@@ -1320,6 +1327,7 @@
             }
         }
     }
+    s->tls_authz = g_strdup(sock->tls_authz);
 
     s->addr = addr = socket_address_flatten(sock->addr);
 
@@ -1399,6 +1407,8 @@
     sock->reconnect = qemu_opt_get_number(opts, "reconnect", 0);
     sock->has_tls_creds = qemu_opt_get(opts, "tls-creds");
     sock->tls_creds = g_strdup(qemu_opt_get(opts, "tls-creds"));
+    sock->has_tls_authz = qemu_opt_get(opts, "tls-authz");
+    sock->tls_authz = g_strdup(qemu_opt_get(opts, "tls-authz"));
 
     addr = g_new0(SocketAddressLegacy, 1);
     if (path) {