nbd: enable use of TLS with NBD block driver

This modifies the NBD driver so that it is possible to request
use of TLS. This is done by providing the 'tls-creds' parameter
with the ID of a previously created QCryptoTLSCreds object.

For example

  $QEMU -object tls-creds-x509,id=tls0,endpoint=client,\
                dir=/home/berrange/security/qemutls \
        -drive driver=nbd,host=localhost,port=9000,tls-creds=tls0

The client will drop the connection if the NBD server does not
provide TLS.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>
Message-Id: <1455129674-17255-15-git-send-email-berrange@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

block/nbd-client.c

@@ -394,8 +394,12 @@ void nbd_client_close(BlockDriverState *bs)
     nbd_teardown_connection(bs);
 }
 
-int nbd_client_init(BlockDriverState *bs, QIOChannelSocket *sioc,
-                    const char *export, Error **errp)
+int nbd_client_init(BlockDriverState *bs,
+                    QIOChannelSocket *sioc,
+                    const char *export,
+                    QCryptoTLSCreds *tlscreds,
+                    const char *hostname,
+                    Error **errp)
 {
     NbdClientSession *client = nbd_get_client_session(bs);
     int ret;
@@ -406,7 +410,7 @@ int nbd_client_init(BlockDriverState *bs, QIOChannelSocket *sioc,
 
     ret = nbd_receive_negotiate(QIO_CHANNEL(sioc), export,
                                 &client->nbdflags,
-                                NULL, NULL,
+                                tlscreds, hostname,
                                 &client->ioc,
                                 &client->size, errp);
     if (ret < 0) {

block/nbd-client.h

@@ -39,6 +39,8 @@ NbdClientSession *nbd_get_client_session(BlockDriverState *bs);
 int nbd_client_init(BlockDriverState *bs,
                     QIOChannelSocket *sock,
                     const char *export_name,
+                    QCryptoTLSCreds *tlscreds,
+                    const char *hostname,
                     Error **errp);
 void nbd_client_close(BlockDriverState *bs);
 

block/nbd.c

@@ -258,36 +258,92 @@ static QIOChannelSocket *nbd_establish_connection(SocketAddress *saddr,
     return sioc;
 }
 
+
+static QCryptoTLSCreds *nbd_get_tls_creds(const char *id, Error **errp)
+{
+    Object *obj;
+    QCryptoTLSCreds *creds;
+
+    obj = object_resolve_path_component(
+        object_get_objects_root(), id);
+    if (!obj) {
+        error_setg(errp, "No TLS credentials with id '%s'",
+                   id);
+        return NULL;
+    }
+    creds = (QCryptoTLSCreds *)
+        object_dynamic_cast(obj, TYPE_QCRYPTO_TLS_CREDS);
+    if (!creds) {
+        error_setg(errp, "Object with id '%s' is not TLS credentials",
+                   id);
+        return NULL;
+    }
+
+    if (creds->endpoint != QCRYPTO_TLS_CREDS_ENDPOINT_CLIENT) {
+        error_setg(errp,
+                   "Expecting TLS credentials with a client endpoint");
+        return NULL;
+    }
+    object_ref(obj);
+    return creds;
+}
+
+
 static int nbd_open(BlockDriverState *bs, QDict *options, int flags,
                     Error **errp)
 {
     BDRVNBDState *s = bs->opaque;
     char *export = NULL;
-    int result;
-    QIOChannelSocket *sioc;
+    QIOChannelSocket *sioc = NULL;
     SocketAddress *saddr;
+    const char *tlscredsid;
+    QCryptoTLSCreds *tlscreds = NULL;
+    const char *hostname = NULL;
+    int ret = -EINVAL;
 
     /* Pop the config into our state object. Exit if invalid. */
     saddr = nbd_config(s, options, &export, errp);
     if (!saddr) {
-        return -EINVAL;
+        goto error;
+    }
+
+    tlscredsid = g_strdup(qdict_get_try_str(options, "tls-creds"));
+    if (tlscredsid) {
+        qdict_del(options, "tls-creds");
+        tlscreds = nbd_get_tls_creds(tlscredsid, errp);
+        if (!tlscreds) {
+            goto error;
+        }
+
+        if (saddr->type != SOCKET_ADDRESS_KIND_INET) {
+            error_setg(errp, "TLS only supported over IP sockets");
+            goto error;
+        }
+        hostname = saddr->u.inet->host;
     }
 
     /* establish TCP connection, return error if it fails
      * TODO: Configurable retry-until-timeout behaviour.
      */
     sioc = nbd_establish_connection(saddr, errp);
-    qapi_free_SocketAddress(saddr);
     if (!sioc) {
-        g_free(export);
-        return -ECONNREFUSED;
+        ret = -ECONNREFUSED;
+        goto error;
     }
 
     /* NBD handshake */
-    result = nbd_client_init(bs, sioc, export, errp);
-    object_unref(OBJECT(sioc));
+    ret = nbd_client_init(bs, sioc, export,
+                          tlscreds, hostname, errp);
+ error:
+    if (sioc) {
+        object_unref(OBJECT(sioc));
+    }
+    if (tlscreds) {
+        object_unref(OBJECT(tlscreds));
+    }
+    qapi_free_SocketAddress(saddr);
     g_free(export);
-    return result;
+    return ret;
 }
 
 static int nbd_co_readv(BlockDriverState *bs, int64_t sector_num,
@@ -349,6 +405,7 @@ static void nbd_refresh_filename(BlockDriverState *bs, QDict *options)
     const char *host   = qdict_get_try_str(options, "host");
     const char *port   = qdict_get_try_str(options, "port");
     const char *export = qdict_get_try_str(options, "export");
+    const char *tlscreds = qdict_get_try_str(options, "tls-creds");
 
     qdict_put_obj(opts, "driver", QOBJECT(qstring_from_str("nbd")));
 
@@ -383,6 +440,9 @@ static void nbd_refresh_filename(BlockDriverState *bs, QDict *options)
     if (export) {
         qdict_put_obj(opts, "export", QOBJECT(qstring_from_str(export)));
     }
+    if (tlscreds) {
+        qdict_put_obj(opts, "tls-creds", QOBJECT(qstring_from_str(tlscreds)));
+    }
 
     bs->full_open_options = opts;
 }