Class: FAIRChampionHarvester::Extruct

Inherits:
Object
  • Object
show all
Defined in:
lib/extruct.rb

Constant Summary collapse

BINARY_CONTENT_TYPE = 
%r{
  application/pdf|application/octet-stream|
  image/|audio/|video/|
  application/zip|application/gzip|application/x-tar|
  application/msword|application/vnd\.
}ix
BINARY_MAGIC_BYTES = 
/\A(%PDF|PK\x03\x04|GIF8|\x89PNG|\xFF\xD8\xFF|\xD0\xCF|\x1F\x8B)/n
TIMEOUT_SECONDS =

Hard ceiling, in seconds, on how long the external extruct process may run. The content-type and magic-byte checks above catch most binary responses, but not all of them (unreliable/missing headers, formats outside BINARY_MAGIC_BYTES, or just very large/slow-to-parse HTML) — without this, a single such request blocks the calling thread (and leaks an orphaned Python process) indefinitely. Configurable via EXTRUCT_TIMEOUT_SECONDS.

ENV.fetch("EXTRUCT_TIMEOUT_SECONDS", 30).to_i

Class Method Summary collapse

Class Method Details

.do_extruct(meta, uri, content_type: nil, body_prefix: nil) ⇒ Object 



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# File 'lib/extruct.rb', line 20

def self.do_extruct(meta, uri, content_type: nil, body_prefix: nil)
  if content_type&.match?(BINARY_CONTENT_TYPE)
    meta.comments << "INFO: Skipping extruct for #{uri} — " \
                     "binary content-type '#{content_type}' is not HTML-parseable.\n"
    return
  end
  if body_prefix&.match?(BINARY_MAGIC_BYTES)
    meta.comments << "INFO: Skipping extruct for #{uri} — binary file signature detected in response body.\n"
    return
  end
  meta.comments << "INFO:  Using 'extruct' to try to extract metadata from return value (message body) of #{uri}.\n"
  warn "begin open3"
  # binding.pry
  # Pass argv as separate elements (not one interpolated string) so this
  # never goes through a shell — `uri` can be attacker/publisher-supplied
  # and must not be shell-interpolated — and prepend the `timeout`
  # coreutil so a hung/slow extruct process is forcibly killed (-k 5:
  # escalate to SIGKILL 5s after the initial SIGTERM if it's ignored)
  # instead of blocking this thread and leaking a child process forever.
  command_parts = Shellwords.split(FAIRChampionHarvester::Utils::ExtructCommand)
  stdout, stderr, status = Open3.capture3(
    "timeout", "-k", "5", TIMEOUT_SECONDS.to_s, *command_parts, uri
  )
  warn ""
  # sleep 5
  warn "open3 status: #{status} #{stdout}"

  if [124, 137].include?(status.exitstatus)
    meta.comments << "WARN: extruct timed out after #{TIMEOUT_SECONDS}s parsing #{uri} — skipping.\n"
    return
  end

  result = stderr # absurd that the output comes over stderr!  LOL!

  # result = %x{#{FAIRChampionHarvester::Utils::ExtructCommand} #{uri} 2>&1}
  # $stderr.puts "\n\n\n\n\n\n\n#{result.class}\n\n#{result.to_s}\n\n#{@extruct_command} #{uri} 2>&1\n\n"
  # need to do some error checking here!
  if result.to_s.match(/(Failed\sto\sextract.*?)\n/)
    meta.comments << "WARN: extruct threw an error #{::Regexp.last_match(1)} when attempting to parse return value (message body) of #{uri}.\n"
    if result.to_s.match(/(ValueError:.*?)\n/)
      meta.comments << "WARN: extruct error was #{::Regexp.last_match(1)}\n"
    end
  elsif result.to_s.match(/^\s+?\{/) or result.to_s.match(/^\s+\[/) # this is JSON
    begin
      json = JSON.parse result
    rescue StandardError
      warn "json parsing failed!  This is bad!\n"
      meta.comments << "INFO: the extruct tool found non-parseable data at #{uri}.  Aborting attempt to read it\n"
      return
    end
    # $stderr.puts "\n\n\n\nFOUND JSON\n\n\n"
    # $stderr.puts "\n\n\n\nFOUND JSON-LD\n#{json["json-ld"]} content\n\n\n"
    meta.comments << "INFO: the extruct tool found parseable data at #{uri}\n"

    Core.parse_rdf(meta, json["json-ld"].to_json, "application/ld+json") if json["json-ld"].any? # RDF
    meta.merge_hash(json["microdata"].first) if json["microdata"].any?
    meta.merge_hash(json["microformat"].first) if json["microformat"].any?
    meta.merge_hash(json["opengraph"].first) if json["opengraph"].any?
    Core.parse_rdf(meta, json["rdfa"].to_json, "application/ld+json") if json["rdfa"].any? # RDF

    meta.merge_hash(json.first) if json.first.is_a? Hash
  else
    meta.comments << "WARN: the extruct tool failed to find parseable data at #{uri}\n"
  end
end