gupnp/CVE-2021-33516.patch

From 697ab5b579debf4b9e0f39143b352877e8af3aad Mon Sep 17 00:00:00 2001
From: Jens Georg <mail@jensge.org>
Date: Mon, 10 May 2021 10:34:36 +0200
Subject: [PATCH] service: Validate host header

Make sure that the host header matches the ip:port of the context.

This is in line with UDA (Host header is required and must match the
location url) and DLNA 7.2.24.1 (All communication has to use ip
addresses and not names)

Prevents DNS rebinding attacs against agains UPnP services
---
 libgupnp/gupnp-context-private.h |  3 ++
 libgupnp/gupnp-context.c         | 51 ++++++++++++++++++++++++++++++++
 libgupnp/gupnp-service.c         | 13 ++++++++
 3 files changed, 67 insertions(+)

diff --git a/libgupnp/gupnp-context-private.h b/libgupnp/gupnp-context-private.h
index 6aa1acd..2657c71 100644
--- a/libgupnp/gupnp-context-private.h
+++ b/libgupnp/gupnp-context-private.h
@@ -36,6 +36,9 @@ _gupnp_context_add_server_handler_with_data (GUPnPContext *context,
                                              const char *path,
                                              AclServerHandler *data);
 
+G_GNUC_INTERNAL gboolean
+gupnp_context_validate_host_header (GUPnPContext *context, const char *host);
+
 G_GNUC_INTERNAL SoupURI *
 gupnp_context_rewrite_uri_to_uri (GUPnPContext *context,
                                   const char   *uri);
diff --git a/libgupnp/gupnp-context.c b/libgupnp/gupnp-context.c
index 460179e..1901798 100644
--- a/libgupnp/gupnp-context.c
+++ b/libgupnp/gupnp-context.c
@@ -1609,6 +1609,57 @@ gupnp_context_remove_server_handler (GUPnPContext *context, const char *path)
         soup_server_remove_handler (priv->server, path);
 }
 
+gboolean
+gupnp_context_validate_host_header (GUPnPContext *context,
+                                    const char *host_header)
+{
+        gboolean retval = FALSE;
+        // Be lazy and let GUri do the heavy lifting here, such as stripping the
+        // [] from v6 addresses, splitting of the port etc.
+        char *uri_from_host = g_strconcat ("http://", host_header, NULL);
+
+        char *host = NULL;
+        int port = 0;
+        GError *error = NULL;
+
+        g_uri_split_network (uri_from_host,
+                             G_URI_FLAGS_NONE,
+                             NULL,
+                             &host,
+                             &port,
+                             &error);
+
+        if (error != NULL) {
+                g_debug ("Failed to parse HOST header from request: %s",
+                         error->message);
+                goto out;
+        }
+
+        const char *host_ip = gssdp_client_get_host_ip (GSSDP_CLIENT (context));
+        gint context_port = gupnp_context_get_port (context);
+
+        if (!g_str_equal (host, host_ip)) {
+                g_debug ("Mismatch between host header and host IP (%s, "
+                         "expected: %s)",
+                         host,
+                         host_ip);
+        }
+
+        if (port != context_port) {
+                g_debug ("Mismatch between host header and host port (%d, "
+                         "expected %d)",
+                         port,
+                         context_port);
+        }
+
+        retval = g_str_equal (host, host_ip) && port == context_port;
+
+out:
+        g_clear_error (&error);
+        g_free (uri_from_host);
+        return retval;
+}
+
 /**
  * gupnp_context_rewrite_uri:
  * @context: a #GUPnPContext
diff --git a/libgupnp/gupnp-service.c b/libgupnp/gupnp-service.c
index b061c34..ad9d40d 100644
--- a/libgupnp/gupnp-service.c
+++ b/libgupnp/gupnp-service.c
@@ -954,6 +954,19 @@ control_server_handler (SoupServer                      *server,
 
         context = gupnp_service_info_get_context (GUPNP_SERVICE_INFO (service));
 
+        const char *host_header =
+                soup_message_headers_get_one (msg->request_headers, "Host");
+
+        if (!gupnp_context_validate_host_header (context, host_header)) {
+                g_warning ("Host header mismatch, expected %s:%d, got %s",
+                           gssdp_client_get_host_ip (GSSDP_CLIENT (context)),
+                           gupnp_context_get_port (context),
+                           host_header);
+
+                soup_message_set_status (msg, SOUP_STATUS_PRECONDITION_FAILED);
+                return;
+        }
+
         /* Get action name */
         soap_action = soup_message_headers_get_one (msg->request_headers,
                                                     "SOAPAction");