verify

# File lib/rubygems/security/policy.rb, line 210
  def verify chain, key = nil, digests = {}, signatures = {},
             full_name = '(unknown)'
    if signatures.empty? then
      if @only_signed then
        raise Gem::Security::Exception,
          "unsigned gems are not allowed by the #{name} policy"
      elsif digests.empty? then
        # lack of signatures is irrelevant if there is nothing to check
        # against
      else
        alert_warning "#{full_name} is not signed"
        return
      end
    end

    opt       = @opt
    digester  = Gem::Security::DIGEST_ALGORITHM
    trust_dir = opt[:trust_dir]
    time      = Time.now

    _, signer_digests = digests.find do |algorithm, file_digests|
      file_digests.values.first.name == Gem::Security::DIGEST_NAME
    end

    if @verify_data then
      raise Gem::Security::Exception, 'no digests provided (probable bug)' if
        signer_digests.nil? or signer_digests.empty?
    else
      signer_digests = {}
    end

    signer = chain.last

    check_key signer, key if key

    check_cert signer, nil, time if @verify_signer

    check_chain chain, time if @verify_chain

    check_root chain, time if @verify_root

    if @only_trusted then
      check_trust chain, digester, trust_dir
    elsif signatures.empty? and digests.empty? then
      # trust is irrelevant if there's no signatures to verify
    else
      alert_warning "#{subject signer} is not trusted for #{full_name}"
    end

    signatures.each do |file, _|
      digest = signer_digests[file]

      raise Gem::Security::Exception, "missing digest for #{file}" unless
        digest
    end

    signer_digests.each do |file, digest|
      signature = signatures[file]

      raise Gem::Security::Exception, "missing signature for #{file}" unless
        signature

      check_data signer.public_key, digester, signature, digest if @verify_data
    end

    true
  end