Truncate summaries to 100,000 characters in the query command

This avoids a DOS vector where incredibly large summary strings would hang rubygems due to taking forever in Gem::Text.clean_text

Author: segiddins

lib/rubygems/commands/query_command.rb

@@ -353,7 +353,8 @@ def spec_platforms entry, platforms
   end
 
   def spec_summary entry, spec
-    entry << "\n\n" << format_text(spec.summary, 68, 4)
+    summary = truncate_text(spec.summary, "the summary for #{spec.full_name}")
+    entry << "\n\n" << format_text(summary, 68, 4)
   end
 
 end

lib/rubygems/text.rb

@@ -13,6 +13,12 @@ def clean_text(text)
     text.gsub(/[\000-\b\v-\f\016-\037\177]/, ".".freeze)
   end
 
+  def truncate_text(text, description, max_length = 100_000)
+    raise ArgumentError, "max_length must be positive" unless max_length > 0
+    return text if text.size <= max_length
+    "Truncating #{description} to #{max_length.to_s.reverse.gsub(/...(?=.)/,'\&,').reverse} characters:\n" + text[0, max_length]
+  end
+
   ##
   # Wraps +text+ to +wrap+ characters and optionally indents by +indent+
   # characters

test/rubygems/test_gem_commands_query_command.rb

@@ -156,6 +156,46 @@ def test_execute_details_cleans_text
     This is a lot of text. This is a lot of text. This is a lot of text.
     This is a lot of text.
 
+pl (1)
+    Platform: i386-linux
+    Author: A User
+    Homepage: http://example.com
+
+    this is a summary
+    EOF
+
+    assert_equal expected, @ui.output
+    assert_equal '', @ui.error
+  end
+
+  def test_execute_details_truncates_summary
+    spec_fetcher do |fetcher|
+      fetcher.spec 'a', 2 do |s|
+        s.summary = 'This is a lot of text. ' * 10_000
+        s.authors = ["Abraham Lincoln \x01", "\x02 Hirohito"]
+        s.homepage = "http://a.example.com/\x03"
+      end
+
+      fetcher.legacy_platform
+    end
+
+    @cmd.handle_options %w[-r -d]
+
+    use_ui @ui do
+      @cmd.execute
+    end
+
+    expected = <<-EOF
+
+*** REMOTE GEMS ***
+
+a (2)
+    Authors: Abraham Lincoln ., . Hirohito
+    Homepage: http://a.example.com/.
+
+    Truncating the summary for a-2 to 100,000 characters:
+#{"    This is a lot of text. This is a lot of text. This is a lot of text.\n" * 1449}    This is a lot of te
+
 pl (1)
     Platform: i386-linux
     Author: A User

test/rubygems/test_gem_text.rb

@@ -78,4 +78,11 @@ def test_levenshtein_distance_replace
     assert_equal 7, levenshtein_distance("xxxxxxx", "ZenTest")
     assert_equal 7, levenshtein_distance("zentest", "xxxxxxx")
   end
+
+  def test_truncate_text
+    assert_equal "abc", truncate_text("abc", "desc")
+    assert_equal "Truncating desc to 2 characters:\nab", truncate_text("abc", "desc", 2)
+    s = "ab" * 500_001
+    assert_equal "Truncating desc to 1,000,000 characters:\n#{s[0, 1_000_000]}", truncate_text(s, "desc", 1_000_000)
+  end
 end