[ruby/psych] Remove taint support

Ruby 2.7 deprecates taint and it no longer has an effect.
The lack of taint support should not cause a problem in
previous Ruby versions.

I'm not sure if the untaint calls in deduplicate are still needed
after the removal of tainting in the parser.  If they are not
needed, they should be removed.

https://github.com/ruby/psych/commit/73c1a2b4e0

3 files changed, 2 insertions, 151 deletions

diff --git a/ext/psych/lib/psych/visitors/to_ruby.rb b/ext/psych/lib/psych/visitors/to_ruby.rb
index 49447e124a..b72fb4a1dc 100644
--- a/ext/psych/lib/psych/visitors/to_ruby.rb
+++ b/ext/psych/lib/psych/visitors/to_ruby.rb
@@ -368,11 +368,9 @@ module Psych
         hash
       end
 
-      if String.method_defined?(:-@)
+      if RUBY_VERSION < '2.7'
         def deduplicate key
           if key.is_a?(String)
-            # It is important to untaint the string, otherwise it won't
-            # be deduplicated into and fstring, but simply frozen.
             -(key.untaint)
           else
             key
@@ -381,9 +379,7 @@ module Psych
       else
         def deduplicate key
           if key.is_a?(String)
-            # Deduplication is not supported by this implementation,
-            # but we emulate it's side effects
-            key.untaint.freeze
+            -key
           else
             key
           end
diff --git a/ext/psych/psych_parser.c b/ext/psych/psych_parser.c
index 0fef173729..fb1a917bb2 100644
--- a/ext/psych/psych_parser.c
+++ b/ext/psych/psych_parser.c
@@ -256,7 +256,6 @@ static VALUE parse(int argc, VALUE *argv, VALUE self)
     yaml_parser_t * parser;
     yaml_event_t event;
     int done = 0;
-    int tainted = 0;
     int state = 0;
     int parser_encoding = YAML_ANY_ENCODING;
     int encoding = rb_utf8_encindex();
@@ -275,13 +274,10 @@ static VALUE parse(int argc, VALUE *argv, VALUE self)
     yaml_parser_delete(parser);
     yaml_parser_initialize(parser);
 
-    if (OBJ_TAINTED(yaml)) tainted = 1;
-
     if (rb_respond_to(yaml, id_read)) {
 	yaml = transcode_io(yaml, &parser_encoding);
 	yaml_parser_set_encoding(parser, parser_encoding);
 	yaml_parser_set_input(parser, io_reader, (void *)yaml);
-	if (RTEST(rb_obj_is_kind_of(yaml, rb_cIO))) tainted = 1;
     } else {
 	StringValue(yaml);
 	yaml = transcode_string(yaml, &parser_encoding);
@@ -352,13 +348,11 @@ static VALUE parse(int argc, VALUE *argv, VALUE self)
 			VALUE prefix = Qnil;
 			if(start->handle) {
 			    handle = rb_str_new2((const char *)start->handle);
-			    if (tainted) OBJ_TAINT(handle);
 			    PSYCH_TRANSCODE(handle, encoding, internal_enc);
 			}
 
 			if(start->prefix) {
 			    prefix = rb_str_new2((const char *)start->prefix);
-			    if (tainted) OBJ_TAINT(prefix);
 			    PSYCH_TRANSCODE(prefix, encoding, internal_enc);
 			}
 
@@ -387,7 +381,6 @@ static VALUE parse(int argc, VALUE *argv, VALUE self)
 		VALUE alias = Qnil;
 		if(event.data.alias.anchor) {
 		    alias = rb_str_new2((const char *)event.data.alias.anchor);
-		    if (tainted) OBJ_TAINT(alias);
 		    PSYCH_TRANSCODE(alias, encoding, internal_enc);
 		}
 
@@ -406,19 +399,16 @@ static VALUE parse(int argc, VALUE *argv, VALUE self)
 		    (const char *)event.data.scalar.value,
 		    (long)event.data.scalar.length
 		    );
-		if (tainted) OBJ_TAINT(val);
 
 		PSYCH_TRANSCODE(val, encoding, internal_enc);
 
 		if(event.data.scalar.anchor) {
 		    anchor = rb_str_new2((const char *)event.data.scalar.anchor);
-		    if (tainted) OBJ_TAINT(anchor);
 		    PSYCH_TRANSCODE(anchor, encoding, internal_enc);
 		}
 
 		if(event.data.scalar.tag) {
 		    tag = rb_str_new2((const char *)event.data.scalar.tag);
-		    if (tainted) OBJ_TAINT(tag);
 		    PSYCH_TRANSCODE(tag, encoding, internal_enc);
 		}
 
@@ -448,14 +438,12 @@ static VALUE parse(int argc, VALUE *argv, VALUE self)
 		VALUE implicit, style;
 		if(event.data.sequence_start.anchor) {
 		    anchor = rb_str_new2((const char *)event.data.sequence_start.anchor);
-		    if (tainted) OBJ_TAINT(anchor);
 		    PSYCH_TRANSCODE(anchor, encoding, internal_enc);
 		}
 
 		tag = Qnil;
 		if(event.data.sequence_start.tag) {
 		    tag = rb_str_new2((const char *)event.data.sequence_start.tag);
-		    if (tainted) OBJ_TAINT(tag);
 		    PSYCH_TRANSCODE(tag, encoding, internal_enc);
 		}
 
@@ -484,13 +472,11 @@ static VALUE parse(int argc, VALUE *argv, VALUE self)
 		VALUE implicit, style;
 		if(event.data.mapping_start.anchor) {
 		    anchor = rb_str_new2((const char *)event.data.mapping_start.anchor);
-		    if (tainted) OBJ_TAINT(anchor);
 		    PSYCH_TRANSCODE(anchor, encoding, internal_enc);
 		}
 
 		if(event.data.mapping_start.tag) {
 		    tag = rb_str_new2((const char *)event.data.mapping_start.tag);
-		    if (tainted) OBJ_TAINT(tag);
 		    PSYCH_TRANSCODE(tag, encoding, internal_enc);
 		}
 
diff --git a/test/psych/test_tainted.rb b/test/psych/test_tainted.rb
deleted file mode 100644
index dcf150b138..0000000000
--- a/test/psych/test_tainted.rb
+++ /dev/null
@@ -1,131 +0,0 @@
-# frozen_string_literal: true
-require_relative 'helper'
-
-module Psych
-  class TestStringTainted < TestCase
-    class Tainted < Handler
-      attr_reader :tc
-
-      def initialize tc
-        @tc = tc
-      end
-
-      def start_document version, tags, implicit
-        tags.flatten.each do |tag|
-          assert_taintedness tag
-        end
-      end
-
-      def alias name
-        assert_taintedness name
-      end
-
-      def scalar value, anchor, tag, plain, quoted, style
-        assert_taintedness value
-        assert_taintedness tag if tag
-        assert_taintedness anchor if anchor
-      end
-
-      def start_sequence anchor, tag, implicit, style
-        assert_taintedness tag if tag
-        assert_taintedness anchor if anchor
-      end
-
-      def start_mapping anchor, tag, implicit, style
-        assert_taintedness tag if tag
-        assert_taintedness anchor if anchor
-      end
-
-      def assert_taintedness thing, message = "'#{thing}' should be tainted"
-        tc.assert thing.tainted?, message
-      end
-    end
-
-    class Untainted < Tainted
-      def assert_taintedness thing, message = "'#{thing}' should not be tainted"
-        tc.assert !thing.tainted?, message
-      end
-    end
-
-
-    def setup
-      handler = Tainted.new self
-      @parser = Psych::Parser.new handler
-    end
-
-    def test_tags_are_tainted
-      assert_taintedness "%TAG !yaml! tag:yaml.org,2002:\n---\n!yaml!str \"foo\""
-    end
-
-    def test_alias
-      assert_taintedness  "--- &ponies\n- foo\n- *ponies"
-    end
-
-    def test_scalar
-      assert_taintedness "--- ponies"
-    end
-
-    def test_anchor
-      assert_taintedness "--- &hi ponies"
-    end
-
-    def test_scalar_tag
-      assert_taintedness "--- !str ponies"
-    end
-
-    def test_seq_start_tag
-      assert_taintedness "--- !!seq [ a ]"
-    end
-
-    def test_seq_start_anchor
-      assert_taintedness "--- &zomg [ a ]"
-    end
-
-    def test_seq_mapping_tag
-      assert_taintedness "--- !!map { a: b }"
-    end
-
-    def test_seq_mapping_anchor
-      assert_taintedness "--- &himom { a: b }"
-    end
-
-    def assert_taintedness string
-      @parser.parse string.dup.taint
-    end
-  end
-
-  class TestStringUntainted < TestStringTainted
-    def setup
-      handler = Untainted.new self
-      @parser = Psych::Parser.new handler
-    end
-
-    def assert_taintedness string
-      @parser.parse string
-    end
-  end
-
-  class TestStringIOUntainted < TestStringTainted
-    def setup
-      handler = Untainted.new self
-      @parser = Psych::Parser.new handler
-    end
-
-    def assert_taintedness string
-      @parser.parse StringIO.new(string)
-    end
-  end
-
-  class TestIOTainted < TestStringTainted
-    def assert_taintedness string
-      Tempfile.create(['something', 'yml']) {|t|
-        t.binmode
-        t.write string
-        t.close
-        File.open(t.path, 'r:bom|utf-8') { |f|
-          @parser.parse f
-        }
-      }
-    end
-  end
-end