[Bug #20990] Reject escaped multibyte char with control/meta prefix

Merged: https://github.com/ruby/ruby/pull/12485

parse.y

@@ -8231,6 +8231,10 @@ read_escape(struct parser_params *p, int flags, const char *begin)
         return '\0';
 
       default:
+        if (!ISASCII(c)) {
+            tokskip_mbchar(p);
+            goto eof;
+        }
         return c;
     }
 }

prism/prism.c

@@ -9657,7 +9657,8 @@ escape_read_warn(pm_parser_t *parser, uint8_t flags, uint8_t flag, const char *t
  */
 static void
 escape_read(pm_parser_t *parser, pm_buffer_t *buffer, pm_buffer_t *regular_expression_buffer, uint8_t flags) {
-    switch (peek(parser)) {
+    uint8_t peeked = peek(parser);
+    switch (peeked) {
         case '\\': {
             parser->current.end++;
             escape_write_byte(parser, buffer, regular_expression_buffer, flags, escape_byte('\\', flags));
@@ -10054,6 +10055,11 @@ escape_read(pm_parser_t *parser, pm_buffer_t *buffer, pm_buffer_t *regular_expre
         }
         /* fallthrough */
         default: {
+            if ((flags & (PM_ESCAPE_FLAG_CONTROL | PM_ESCAPE_FLAG_META)) && !char_is_ascii_printable(peeked)) {
+                size_t width = parser->encoding->char_width(parser->current.end, parser->end - parser->current.end);
+                pm_parser_err(parser, parser->current.start, parser->current.end + width, PM_ERR_ESCAPE_INVALID_META);
+                return;
+            }
             if (parser->current.end < parser->end) {
                 escape_write_escape_encoded(parser, buffer, regular_expression_buffer, flags);
             } else {

test/ripper/test_lexer.rb

@@ -355,6 +355,15 @@ world"
     ]
 
     assert_lexer(expected, code)
+
+    code = %["\\C-\\\u{3042}"]
+    expected = [
+      [[1, 0], :on_tstring_beg, '"', state(:EXPR_BEG)],
+      [[1, 1], :on_tstring_content, "\\C-\\\u{3042}", state(:EXPR_BEG)],
+      [[1, 8], :on_tstring_end, '"', state(:EXPR_END)],
+    ]
+
+    assert_lexer(expected, code)
   end
 
   def test_invalid_escape_meta_mbchar
@@ -366,6 +375,15 @@ world"
     ]
 
     assert_lexer(expected, code)
+
+    code = %["\\M-\\\u{3042}"]
+    expected = [
+      [[1, 0], :on_tstring_beg, '"', state(:EXPR_BEG)],
+      [[1, 1], :on_tstring_content, "\\M-\\\u{3042}", state(:EXPR_BEG)],
+      [[1, 8], :on_tstring_end, '"', state(:EXPR_END)],
+    ]
+
+    assert_lexer(expected, code)
   end
 
   def test_invalid_escape_meta_ctrl_mbchar
@@ -377,6 +395,15 @@ world"
     ]
 
     assert_lexer(expected, code)
+
+    code = %["\\M-\\C-\\\u{3042}"]
+    expected = [
+      [[1, 0], :on_tstring_beg, '"', state(:EXPR_BEG)],
+      [[1, 1], :on_tstring_content, "\\M-\\C-\\\u{3042}", state(:EXPR_BEG)],
+      [[1, 11], :on_tstring_end, '"', state(:EXPR_END)],
+    ]
+
+    assert_lexer(expected, code)
   end
 
   def test_invalid_escape_ctrl_meta_mbchar
@@ -388,6 +415,15 @@ world"
     ]
 
     assert_lexer(expected, code)
+
+    code = %["\\C-\\M-\\\u{3042}"]
+    expected = [
+      [[1, 0], :on_tstring_beg, '"', state(:EXPR_BEG)],
+      [[1, 1], :on_tstring_content, "\\C-\\M-\\\u{3042}", state(:EXPR_BEG)],
+      [[1, 11], :on_tstring_end, '"', state(:EXPR_END)],
+    ]
+
+    assert_lexer(expected, code)
   end
 
   def test_invalid_escape_string

test/ruby/test_literal.rb

@@ -97,6 +97,10 @@ class TestRubyLiteral < Test::Unit::TestCase
     assert_equal "ab", eval("?a 'b'")
     assert_equal "a\nb", eval("<<A 'b'\na\nA")
 
+    assert_raise(SyntaxError) {eval('"\C-' "\u3042" '"')}
+    assert_raise(SyntaxError) {eval('"\C-\\' "\u3042" '"')}
+    assert_raise(SyntaxError) {eval('"\M-' "\u3042" '"')}
+    assert_raise(SyntaxError) {eval('"\M-\\' "\u3042" '"')}
   ensure
     $VERBOSE = verbose_bak
   end