From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS4713 221.184.0.0/13 X-Spam-Status: No, score=-3.9 required=3.0 tests=AWL,BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI, SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from neon.ruby-lang.org (neon.ruby-lang.org [221.186.184.75]) by dcvr.yhbt.net (Postfix) with ESMTP id B0EFA1F5AE for ; Thu, 29 Apr 2021 13:05:26 +0000 (UTC) Received: from neon.ruby-lang.org (localhost [IPv6:::1]) by neon.ruby-lang.org (Postfix) with ESMTP id CFCDE120EF1; Thu, 29 Apr 2021 22:04:09 +0900 (JST) Received: from o1678948x4.outbound-mail.sendgrid.net (o1678948x4.outbound-mail.sendgrid.net [167.89.48.4]) by neon.ruby-lang.org (Postfix) with ESMTPS id 7B1F3120EF2 for ; Thu, 29 Apr 2021 22:04:07 +0900 (JST) Received: by filterdrecv-canary-56666b5446-n8cv6 with SMTP id filterdrecv-canary-56666b5446-n8cv6-1-608AAEFE-126 2021-04-29 13:05:02.807681109 +0000 UTC m=+56795.417750231 Received: from herokuapp.com (unknown) by ismtpd0188p1mdw1.sendgrid.net (SG) with ESMTP id 2_upxiGERZ6ORrGcFa4ijw for ; Thu, 29 Apr 2021 13:05:02.695 +0000 (UTC) Date: Thu, 29 Apr 2021 13:05:02 +0000 (UTC) From: daniel@dan42.com Message-ID: References: Mime-Version: 1.0 X-Redmine-Project: ruby-master X-Redmine-Issue-Tracker: Feature X-Redmine-Issue-Id: 17837 X-Redmine-Issue-Author: sam.saffron X-Redmine-Sender: Dan0042 X-Mailer: Redmine X-Redmine-Host: bugs.ruby-lang.org X-Redmine-Site: Ruby Issue Tracking System X-Auto-Response-Suppress: All Auto-Submitted: auto-generated X-Redmine-MailingListIntegration-Message-Ids: 79702 X-SG-EID: =?us-ascii?Q?8sy4RigFvRTdBfCVJrT9zb2J88PC92TMQwdNgaWYaq6M9vb62aNV5j6hG6WI+Y?= =?us-ascii?Q?lpP5XwI8dWRi6=2FQXkH6juTBYtXCMcg7JmSEm3=2Fv?= =?us-ascii?Q?Sij6KTNqn+EqrB2RyxClRed=2F211FNrbp991g1Oh?= =?us-ascii?Q?XI9mKperSVjhz6drRJQEz6UQCtACdx4RaO5GH5s?= =?us-ascii?Q?=2FGAhmMjLHVqcvQEYp1WZ1oNj8etuf2BWIQzYUxb?= =?us-ascii?Q?AzsEcOpW0HWadwVuI=3D?= To: ruby-core@ruby-lang.org X-Entity-ID: b/2+PoftWZ6GuOu3b0IycA== X-ML-Name: ruby-core X-Mail-Count: 103655 Subject: [ruby-core:103655] [Ruby master Feature#17837] Add support for Regexp timeouts X-BeenThere: ruby-core@ruby-lang.org X-Mailman-Version: 2.1.15 Precedence: list Reply-To: Ruby developers List-Id: Ruby developers List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: ruby-core-bounces@ruby-lang.org Sender: "ruby-core" Issue #17837 has been updated by Dan0042 (Daniel DeLorme). +1 wonderful and useful idea Even without the DoS aspect, it's all too easy to create regexps with pathological performance that only manifests in certain edge cases, usually in production. It would be very useful if some kind of timeout exception was raised. Ideally that exception should have references (attr_reader) to both the regexp and string that caused the timeout. ---------------------------------------- Feature #17837: Add support for Regexp timeouts https://bugs.ruby-lang.org/issues/17837#change-91751 * Author: sam.saffron (Sam Saffron) * Status: Open * Priority: Normal ---------------------------------------- ### Background ReDoS are a very common security issue. At Discourse we have seen a few through the years. https://owasp.org/www-community/attacks/Regular_expression_Denial_of_Service_-_ReDoS In a nutshell there are 100s of ways this can happen in production apps, the key is for an attacker (or possibly innocent person) to supply either a problematic Regexp or a bad string to test it with. ``` /A(B|C+)+D/ =~ "A" + "C" * 100 + "X" ``` Having a problem Regexp somewhere in a large app is a universal constant, it will happen as long as you are using Regexps. Currently the only feasible way of supplying a consistent safeguard is by using `Thread.raise` and managing all execution. This kind of pattern requires usage of a third party implementation. There are possibly issues with jRuby and Truffle when taking approaches like this. ### Prior art .NET provides a `MatchTimeout` property per: https://docs.microsoft.com/en-us/dotnet/api/system.text.regularexpressions.regex.matchtimeout?view=net-5.0 Java has nothing built in as far as I can tell: https://stackoverflow.com/questions/910740/cancelling-a-long-running-regex-match Node has nothing built in as far as I can tell: https://stackoverflow.com/questions/38859506/cancel-regex-match-if-timeout Golang and Rust uses RE2 which is not vulnerable to DoS by limiting features (available in Ruby RE2 gem) ``` irb(main):003:0> r = RE2::Regexp.new('A(B|C+)+D') => # irb(main):004:0> r.match("A" + "C" * 100 + "X") => nil ``` ### Proposal Implement `Regexp.timeout` which allow us to specify a global timeout for all Regexp operations in Ruby. Per Regexp would require massive application changes, almost all web apps would do just fine with a 1 second Regexp timeout. If `timeout` is set to `nil` everything would work as it does today, when set to second a "monitor" thread would track running regexps and time them out according to the global value. ### Alternatives I recommend against a "per Regexp" API as this decision is at the application level. You want to apply it to all regular expressions in all the gems you are consuming. I recommend against a move to RE2 at the moment as way too much would break ### See also: https://people.cs.vt.edu/davisjam/downloads/publications/Davis-Dissertation-2020.pdf https://levelup.gitconnected.com/the-regular-expression-denial-of-service-redos-cheat-sheet-a78d0ed7d865 -- https://bugs.ruby-lang.org/