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=-2.5 required=3.0 tests=AWL,BAYES_00, DKIM_ADSP_CUSTOM_MED,FORGED_GMAIL_RCVD,FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY shortcircuit=no autolearn=no 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 8268F1F5AE for ; Tue, 27 Apr 2021 23:40:00 +0000 (UTC) Received: from neon.ruby-lang.org (localhost [IPv6:::1]) by neon.ruby-lang.org (Postfix) with ESMTP id 870BF120C42; Wed, 28 Apr 2021 08:38:56 +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 18B1E120C41 for ; Wed, 28 Apr 2021 08:38:53 +0900 (JST) Received: by filterdrecv-5c7f9fdd98-d2qfs with SMTP id filterdrecv-5c7f9fdd98-d2qfs-1-6088A0CA-2F 2021-04-27 23:39:54.611446782 +0000 UTC m=+433426.851547586 Received: from herokuapp.com (unknown) by ismtpd0150p1mdw1.sendgrid.net (SG) with ESMTP id nJBGeJ47QzWY0MMt0saDsw for ; Tue, 27 Apr 2021 23:39:54.490 +0000 (UTC) Date: Tue, 27 Apr 2021 23:39:54 +0000 (UTC) From: sam.saffron@gmail.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: sam.saffron 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: 79678 X-SG-EID: =?us-ascii?Q?GD31AXMrLYtZC3ZmvheLkg5nAqKYtjT=2Fa5aksj98ZWMfXd8G5TZCKR8hIIHkH8?= =?us-ascii?Q?PT8PhRPFaRx5jGnPL75p=2FV4cK3pAG9OH+Tjvg=2Ff?= =?us-ascii?Q?5Udf9AI0pztdNxNLwAuViliggvuLEPfIDgJ3YpM?= =?us-ascii?Q?+XgSULO9UC9RyDEklCkY24AW=2FQv+5qfuemBvv5s?= =?us-ascii?Q?PtFEHAinfWpAjc=2FF4P9pvfOgab3Bh0y39sA=3D=3D?= To: ruby-core@ruby-lang.org X-Entity-ID: b/2+PoftWZ6GuOu3b0IycA== X-ML-Name: ruby-core X-Mail-Count: 103631 Subject: [ruby-core:103631] [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 reported by sam.saffron (Sam Saffron). ---------------------------------------- Feature #17837: Add support for Regexp timeouts https://bugs.ruby-lang.org/issues/17837 * 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/