caps_hash: don't crash if FORM_TYPE has no <value>

Previously there were a couple of ways this could crash:

* First, if you had a <field type='hidden' var='FORM_TYPE'> with no
  <value> child, field->default_value would be NULL so

      g_value_get_string (field->default_value)

  would critical and return NULL and then you'll be in undefined hell.

* Having fixed that, the code to sort data forms by FORM_TYPE would also
  crash because it happens before the FORM_TYPEs have been validated and
  used g_value_get_string() without checking and then strcmp()ed the
  possibly-NULL result.

I actually have a work-in-progress branch that makes this all a lot less
hairy by adding, among other things, a wocky_data_form_get_form_type()
function which can do the validation for us. But better to fix the
crashes before refactoring them away.

https://bugs.freedesktop.org/show_bug.cgi?id=61433

1 files changed, 22 insertions, 7 deletions

diff --git a/wocky/wocky-caps-hash.c b/wocky/wocky-caps-hash.c
index 7bd2c43..01006a7 100644
--- a/wocky/wocky-caps-hash.c
+++ b/wocky/wocky-caps-hash.c
@@ -80,8 +80,17 @@ dataforms_cmp (gconstpointer a,
   else if (left_type != NULL && right_type == NULL)
     return 1;
   else /* left_type != NULL && right_type != NULL */
-    return strcmp (g_value_get_string (left_type->default_value),
-        g_value_get_string (right_type->default_value));
+    {
+      const gchar *left_value = NULL, *right_value = NULL;
+
+      if (left_type->raw_value_contents != NULL)
+        left_value = left_type->raw_value_contents[0];
+
+      if (right_type->raw_value_contents != NULL)
+        right_value = right_type->raw_value_contents[0];
+
+      return g_strcmp0 (left_value, right_value);
+    }
 }
 
 static GPtrArray *
@@ -190,16 +199,22 @@ wocky_caps_hash_compute_from_lists (
           continue;
         }
 
-      form_name = g_value_get_string (field->default_value);
-
       if (field->type != WOCKY_DATA_FORM_FIELD_TYPE_HIDDEN)
         {
-          DEBUG ("FORM_TYPE field of form '%s' is not hidden; "
-              "ignoring form and moving onto next one",
-                 form_name);
+          DEBUG ("FORM_TYPE field is not hidden; "
+              "ignoring form and moving onto next one");
           continue;
         }
 
+      if (field->raw_value_contents == NULL ||
+          g_strv_length (field->raw_value_contents) != 1)
+        {
+          DEBUG ("FORM_TYPE field does not have exactly one value; failing");
+          goto cleanup;
+        }
+
+      form_name = field->raw_value_contents[0];
+
       if (g_hash_table_lookup (form_names, form_name) != NULL)
         {
           DEBUG ("error: there are multiple data forms with the "