[libgovirt] utils: Check for valid data before calling rest_xml_parser_parse_from_data()

[Eduardo de Barros Lima <eblima src gnome org>]

commit 56bdee0fc7a82ba15c9b3655a7ef1dbb6c03eb97
Author: Eduardo Lima (Etrunko) <etrunko redhat com>
Date:   Mon Feb 4 15:58:40 2019 -0200

    utils: Check for valid data before calling rest_xml_parser_parse_from_data()
    
    In the case of HTTP errors, such as a invalid TLS certificate, the
    returned data is NULL, and the code in librest does not check for the
    pointer being valid, causing a segfault.
    
    The users of this function have been updated to check for NULL return
    value.
    
    Signed-off-by: Eduardo Lima (Etrunko) <etrunko redhat com>

 govirt/ovirt-proxy.c    | 6 ++++++
 govirt/ovirt-resource.c | 9 ++++++++-
 govirt/ovirt-utils.c    | 7 +++++--
 3 files changed, 19 insertions(+), 3 deletions(-)
---
diff --git a/govirt/ovirt-proxy.c b/govirt/ovirt-proxy.c
index 739bb25..ad00b8c 100644
--- a/govirt/ovirt-proxy.c
+++ b/govirt/ovirt-proxy.c
@@ -361,6 +361,11 @@ static gboolean get_collection_xml_async_cb(OvirtProxy* proxy,
     data = (OvirtProxyGetCollectionAsyncData *)user_data;
 
     root = ovirt_rest_xml_node_from_call(call);
+    if (root == NULL) {
+        g_set_error_literal(error, OVIRT_ERROR, OVIRT_ERROR_PARSING_FAILED,
+                            _("Failed to parse response from collection"));
+        goto end;
+    }
 
     /* Do the parsing */
     g_warn_if_fail(data->parser != NULL);
@@ -370,6 +375,7 @@ static gboolean get_collection_xml_async_cb(OvirtProxy* proxy,
 
     rest_xml_node_unref(root);
 
+end:
     return parsed;
 }
 
diff --git a/govirt/ovirt-resource.c b/govirt/ovirt-resource.c
index 85c55a1..cc670db 100644
--- a/govirt/ovirt-resource.c
+++ b/govirt/ovirt-resource.c
@@ -864,17 +864,24 @@ static gboolean ovirt_resource_refresh_async_cb(OvirtProxy *proxy,
 {
     OvirtResource *resource;
     RestXmlNode *root;
-    gboolean refreshed;
+    gboolean refreshed = FALSE;
 
     g_return_val_if_fail(REST_IS_PROXY_CALL(call), FALSE);
     g_return_val_if_fail(OVIRT_IS_RESOURCE(user_data), FALSE);
 
     root = ovirt_rest_xml_node_from_call(call);
+    if (root == NULL) {
+        g_set_error_literal(error, OVIRT_ERROR, OVIRT_ERROR_PARSING_FAILED,
+                            _("Failed to parse response from resource"));
+        goto end;
+    }
+
     resource = OVIRT_RESOURCE(user_data);
     refreshed = ovirt_resource_init_from_xml(resource, root, error);
 
     rest_xml_node_unref(root);
 
+end:
     return refreshed;
 }
 
diff --git a/govirt/ovirt-utils.c b/govirt/ovirt-utils.c
index dfaf09d..56ce2e1 100644
--- a/govirt/ovirt-utils.c
+++ b/govirt/ovirt-utils.c
@@ -40,11 +40,14 @@ ovirt_rest_xml_node_from_call(RestProxyCall *call)
 {
     RestXmlParser *parser;
     RestXmlNode *node;
+    const char * data = rest_proxy_call_get_payload (call);
+
+    if (data == NULL)
+        return NULL;
 
     parser = rest_xml_parser_new ();
 
-    node = rest_xml_parser_parse_from_data (parser,
-            rest_proxy_call_get_payload (call),
+    node = rest_xml_parser_parse_from_data (parser, data,
             rest_proxy_call_get_payload_length (call));
 
     g_object_unref(G_OBJECT(parser));