[ruby/psych] Introduce `Psych.unsafe_load`

In future versions of Psych, the `load` method will be mostly the same
as the `safe_load` method.  In other words, the `load` method won't
allow arbitrary object deserialization (which can be used to escalate to
an RCE).  People that need to load *trusted* documents can use the
`unsafe_load` method.

This commit introduces the `unsafe_load` method so that people can
incrementally upgrade.  For example, if they try to upgrade to 4.0.0 and
something breaks, they can downgrade, audit callsites, change to
`safe_load` or `unsafe_load` as required, and then upgrade to 4.0.0
smoothly.

https://github.com/ruby/psych/commit/cb50aa8d3f

1 files changed, 21 insertions, 9 deletions

diff --git a/test/psych/helper.rb b/test/psych/helper.rb
index b118b31c46..0643139d8c 100644
--- a/test/psych/helper.rb
+++ b/test/psych/helper.rb
@@ -41,24 +41,30 @@ module Psych
     # Convert between Psych and the object to verify correct parsing and
     # emitting
     #
-    def assert_to_yaml( obj, yaml )
-      assert_equal( obj, Psych::load( yaml ) )
+    def assert_to_yaml( obj, yaml, loader = :load )
+      assert_equal( obj, Psych.send(loader, yaml) )
       assert_equal( obj, Psych::parse( yaml ).transform )
-      assert_equal( obj, Psych::load( obj.to_yaml ) )
+      assert_equal( obj, Psych.send(loader, obj.to_yaml) )
       assert_equal( obj, Psych::parse( obj.to_yaml ).transform )
-      assert_equal( obj, Psych::load(
+      assert_equal( obj, Psych.send(loader,
         obj.to_yaml(
           :UseVersion => true, :UseHeader => true, :SortKeys => true
         )
       ))
+    rescue Psych::DisallowedClass, Psych::BadAlias
+      assert_to_yaml obj, yaml, :unsafe_load
     end
 
     #
     # Test parser only
     #
     def assert_parse_only( obj, yaml )
-      assert_equal( obj, Psych::load( yaml ) )
-      assert_equal( obj, Psych::parse( yaml ).transform )
+      begin
+        assert_equal obj, Psych::load( yaml )
+      rescue Psych::DisallowedClass, Psych::BadAlias
+        assert_equal obj, Psych::unsafe_load( yaml )
+      end
+      assert_equal obj, Psych::parse( yaml ).transform
     end
 
     def assert_cycle( obj )
@@ -69,9 +75,15 @@ module Psych
         assert_nil Psych::load(Psych.dump(obj))
         assert_nil Psych::load(obj.to_yaml)
       else
-        assert_equal(obj, Psych.load(v.tree.yaml))
-        assert_equal(obj, Psych::load(Psych.dump(obj)))
-        assert_equal(obj, Psych::load(obj.to_yaml))
+        begin
+          assert_equal(obj, Psych.load(v.tree.yaml))
+          assert_equal(obj, Psych::load(Psych.dump(obj)))
+          assert_equal(obj, Psych::load(obj.to_yaml))
+        rescue Psych::DisallowedClass, Psych::BadAlias
+          assert_equal(obj, Psych.unsafe_load(v.tree.yaml))
+          assert_equal(obj, Psych::unsafe_load(Psych.dump(obj)))
+          assert_equal(obj, Psych::unsafe_load(obj.to_yaml))
+        end
       end
     end