From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on starla X-Spam-Level: X-Spam-Status: No, score=0.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_BL_SPAMCOP_NET,SPF_HELO_PASS, SPF_PASS autolearn=no autolearn_force=no version=3.4.6 Received: from nue.mailmanlists.eu (nue.mailmanlists.eu [94.130.110.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits)) (No client certificate requested) by dcvr.yhbt.net (Postfix) with ESMTPS id 76B121F4BE for ; Mon, 21 Oct 2024 09:09:45 +0000 (UTC) Authentication-Results: dcvr.yhbt.net; dkim=pass (1024-bit key; unprotected) header.d=ml.ruby-lang.org header.i=@ml.ruby-lang.org header.a=rsa-sha256 header.s=mail header.b=pc+WA8J3; dkim=fail reason="signature verification failed" (2048-bit key; unprotected) header.d=ruby-lang.org header.i=@ruby-lang.org header.a=rsa-sha256 header.s=s1 header.b=BN+ezO/f; dkim-atps=neutral DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ml.ruby-lang.org; s=mail; t=1729501752; bh=Zy22Q7IXsdnHkdT+TY3zJ40Pn2E8lRoCwjgUXKtUEo4=; h=Date:References:To:Reply-To:Subject:List-Id:List-Archive: List-Help:List-Owner:List-Post:List-Subscribe:List-Unsubscribe: From:Cc:From; b=pc+WA8J3ULK38gewC1EkN4LN+KXexpeow54eLl/gd7wLJwpnehPZ6Cz+wTdVQVa3E XcD6gKaL+UoF1y99/MwcchcvlVpUeKJXOkLemSov8m/zFwbGVPo1V46qTMWWEgLMXt Moa8e3qvqFb8DVZv/VJ2HWp6Y/PyC5h07toDieLM= Received: from nue.mailmanlists.eu (localhost [IPv6:::1]) by nue.mailmanlists.eu (Postfix) with ESMTP id EAEFA4457C for ; Mon, 21 Oct 2024 09:09:12 +0000 (UTC) Authentication-Results: nue.mailmanlists.eu; dkim=pass (2048-bit key; unprotected) header.d=ruby-lang.org header.i=@ruby-lang.org header.a=rsa-sha256 header.s=s1 header.b=BN+ezO/f; dkim-atps=neutral Received: from s.wrqvtvvn.outbound-mail.sendgrid.net (s.wrqvtvvn.outbound-mail.sendgrid.net [149.72.120.130]) by nue.mailmanlists.eu (Postfix) with ESMTPS id 2966E44530 for ; Mon, 21 Oct 2024 08:50:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ruby-lang.org; h=from:references:subject:mime-version:content-type: content-transfer-encoding:list-id:to:cc:content-type:from:subject:to; s=s1; bh=7Fgnnv2MPvB58Cu+aTsTzbokVahhr5I3TIX80L4QaD0=; b=BN+ezO/fSDmiMWLwNr2ca7iG7TiYHV0qQVU9cHvrCRFG7i2Wlrge1j/ptMSJLnGPcC1u k58eSYn5T6QQzOjG/ueCNo9d2jnMkPXF8FWtT0Pwru8rzNxjNKo/edJIj7GmkuT9yetaoc AGKZQFV5130Z4O4tDT7UuKMc3T+jVFnCzqMpnxn5aGu6UzQBUTw+08NmpUUWvRTwuZ5aQl xNDJ4QxIlUcS1xzmWwBcK3urKGHkyAz+fVFkB8kYpCU6PqRh0W9asMzuJobNE05WbexC6g zha2JZb9RpG5DjaJqI29e5K4vdYC3MjR7e0XDwpeZsGevTyFfRX0T7l7eMv7Tc8Q== Received: by recvd-5577bcb48c-x6nqm with SMTP id recvd-5577bcb48c-x6nqm-1-671615CD-2 2024-10-21 08:50:21.145861168 +0000 UTC m=+3336859.967462362 Received: from herokuapp.com (unknown) by geopod-ismtpd-16 (SG) with ESMTP id j19CFuxoTzaHvyK5Bt3pMw for ; Mon, 21 Oct 2024 08:50:21.129 +0000 (UTC) Date: Mon, 21 Oct 2024 08:50:21 +0000 (UTC) Message-ID: References: Mime-Version: 1.0 X-Redmine-Project: ruby-master X-Redmine-Issue-Tracker: Bug X-Redmine-Issue-Id: 20693 X-Redmine-Issue-Author: kjtsanaktsidis X-Redmine-Issue-Assignee: akr X-Redmine-Issue-Priority: Normal X-Redmine-Sender: kjtsanaktsidis 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: 96189 X-SG-EID: =?us-ascii?Q?u001=2Ehtvb0C=2FfA7uJxza5ajJoGjWf7D35DJhKe7Y94xYuv7SZnqx0qbu=2F70+zV?= =?us-ascii?Q?XRgEUZlB2KACYgzrNXwJOFqD+GI4v+xLlProPhe?= =?us-ascii?Q?RqFaaJyjkovmU6JV7Kd+YBM+5C9o2WJk0n9ru9p?= =?us-ascii?Q?rvr9Pig0NWw1ffvOpXB0cdr5P3OGeLOI6kEZZOH?= =?us-ascii?Q?B4zGQP=2FHqtFevA4iAEJYP+kebyxW0=2FZzxoVWYvr?= =?us-ascii?Q?ciVdZTpfwzCs36to4FYtdlxw8uy5T7njzQncrK3?= =?us-ascii?Q?GrQPOydWx48Fb57G9eryPS1HGQ=3D=3D?= To: ruby-core@ml.ruby-lang.org X-Entity-ID: u001.I8uzylDtAfgbeCOeLBYDww== Message-ID-Hash: V4T6WLM7RO3HOFBFOSVJUIRQCDTGVEAR X-Message-ID-Hash: V4T6WLM7RO3HOFBFOSVJUIRQCDTGVEAR X-MailFrom: bounces+313651-b711-ruby-core=ml.ruby-lang.org@em5188.ruby-lang.org X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header X-Mailman-Version: 3.3.9 Precedence: list Reply-To: Ruby developers Subject: [ruby-core:119555] [Ruby master Bug#20693] Dir.tmpdir should perform a real access check before warning about writability List-Id: Ruby developers Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: From: "kjtsanaktsidis (KJ Tsanaktsidis) via ruby-core" Cc: "kjtsanaktsidis (KJ Tsanaktsidis)" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Issue #20693 has been updated by kjtsanaktsidis (KJ Tsanaktsidis). Sorry it took me so long to get back to you @akr . I've added a short comment about this - if you're OK with it I will commit it. Thanks! ---------------------------------------- Bug #20693: Dir.tmpdir should perform a real access check before warning about writability https://bugs.ruby-lang.org/issues/20693#change-110172 * Author: kjtsanaktsidis (KJ Tsanaktsidis) * Status: Open * Assignee: akr (Akira Tanaka) * Backport: 3.1: UNKNOWN, 3.2: UNKNOWN, 3.3: UNKNOWN ---------------------------------------- The code in `Dir.tmpdir` attempts to warn the user if their temp directory is deficient for some reason: ```ruby case when !stat.directory? warn "#{name} is not a directory: #{dir}" when !stat.writable? warn "#{name} is not writable: #{dir}" when stat.world_writable? && !stat.sticky? warn "#{name} is world-writable: #{dir}" else break dir end ``` This check for writability is looking at the user/group/world access bits on the stat output, and determining if the user running Ruby is allowed to write to the temp directory based on that. However, modern operating systems contain other mechanisms apart from the user/group/world bits which can grant access to a directory that would otherwise be denied, or vice versa. Things like: * Posix ACL's * Linux's capabilities like CAP_DAC_OVERRIDE * Linux Security Modules like SELinux or AppArmor * Syscall filters like Linux's seccomp * Granular capability systems like FreeBSD's Capsicum * OpenBSD's pledge and unveil * Windows too has a rich ACL system for controlling filesystem access To address this, we should call `File.writable?` instead of `stat.writable?`, which asks the system whether the file is writable using the `euidaccess()` function if available. On Linux/glibc, at least, this will issue an `access(2)` syscall, and the Kernel can take all of the above into account. n.b. if Ruby is running as suid, then glibc currently will NOT ask the kernel to perform the access check in `euidaccess()`, and instead does a similar thing to what `Stat#writable?` does (https://github.com/bminor/glibc/blob/7f04bb4e49413bd57ac3215f3480b09ae7131968/sysdeps/posix/euidaccess.c#L159-L162). This is because of the relatively new `faccessat2(2)` syscall is required to do this properly, and there is some ecosystem issues with leveraging this by default (e.g. https://bugzilla.redhat.com/show_bug.cgi?id=1900021). Since running Ruby as suid is probably a very bad idea anyway, and the glibc implementation isn't any worse than the `Stat#writable?` one, this seems OK though. -- https://bugs.ruby-lang.org/ ______________________________________________ ruby-core mailing list -- ruby-core@ml.ruby-lang.org To unsubscribe send an email to ruby-core-leave@ml.ruby-lang.org ruby-core info -- https://ml.ruby-lang.org/mailman3/lists/ruby-core.ml.ruby-lang.org/