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=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS, T_SCC_BODY_TEXT_LINE autolearn=ham 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 E687F1F47A for ; Fri, 23 Aug 2024 18:00:11 +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=FwIE0JfR; 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=cLWQcgFl; dkim-atps=neutral DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ml.ruby-lang.org; s=mail; t=1724436009; bh=ukDMZ3CRrSU3H7ncURQXNS61reiBintP4+mJkBol3pQ=; 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=FwIE0JfRD4YMPWJuImKBjqxmVe/vkniUO6MhFYi1un4qDvzyp2pPaY3IJ525SDnyg 7MIFcS2+gGv8D+Ec9D8riHWmcfoKu79hZ7hzhuzO51iDAF+dkOzYu9+49ie51MVvGG n3hmim4zGDlT9TNh4Q+PsIT9eUK6I2Xoo6e1aGH0= Received: from nue.mailmanlists.eu (localhost [IPv6:::1]) by nue.mailmanlists.eu (Postfix) with ESMTP id 46E4943CBF for ; Fri, 23 Aug 2024 18:00:09 +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=cLWQcgFl; dkim-atps=neutral Received: from s.wrqvwxzv.outbound-mail.sendgrid.net (s.wrqvwxzv.outbound-mail.sendgrid.net [149.72.154.232]) by nue.mailmanlists.eu (Postfix) with ESMTPS id 97EB643C71 for ; Fri, 23 Aug 2024 17:59:58 +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=fIwO4d8Ol4k64EyMMLfraKFq/tHx1cyTbXbTHtpPlYU=; b=cLWQcgFlaQZoCl/2myflaaBJgzzbBEqUyJrVUXI7oxiIZV0njudx5CLUltFcBpKJAZzq moVjg60+Jk58B6EHyq7EKB22H0GYqCzLoi8wt1SqzJXKrHzm8bPIg/8OLW5nzLMRCLcUB0 dV7CgVBtRsoQ4muo0r6CbbPnXhr6IhmqzPMw3/pV4IAXnJ/y2O1//pHem9IHjaY4cFiRyN prUDN8pXNGjAjM45gQQ0AIYvvleeasINDz+X6LvvBUQ/P7kPXO8vsHQobFMvn7IVhHL63W i+TMuFthTzTedk+a2W4D55Jy73Y7XlaRAglWH3xUyvWRScsLrt9f06y7Wh6exRwA== Received: by recvd-649fff897d-m4j2j with SMTP id recvd-649fff897d-m4j2j-1-66C8CE1C-4 2024-08-23 17:59:56.658875487 +0000 UTC m=+157058.653047508 Received: from herokuapp.com (unknown) by geopod-ismtpd-2 (SG) with ESMTP id fySHYJJ0S6-TBDp3R9pP6w for ; Fri, 23 Aug 2024 17:59:56.622 +0000 (UTC) Date: Fri, 23 Aug 2024 18:00:02 +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-Priority: Normal 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: 95574 X-SG-EID: =?us-ascii?Q?u001=2EHy4LB1bizMxDg=2Fk6r7dYDS9qUDe3jZN8DIPm4OS+F86l7XdLFEAVX=2F2lh?= =?us-ascii?Q?z0Jj=2Ft7J6DgKnq5Qaf6Ba4+egck=2FoKuUHMa9Cn6?= =?us-ascii?Q?7D+EQ8vUJVvfG9wPLOma61cr0aUGo=2FoVPZL0R3f?= =?us-ascii?Q?CEP79SZh2P8RwdPe0CheS6kxhiOrAahEWLvnAqB?= =?us-ascii?Q?b5abaIxf5Vq40JDsA3JgT4FLU8eJWl5VFkOf3Lz?= =?us-ascii?Q?5L8xYHJXNcQxgBwz6mAd11dc6boAYSPv0Gr5Ii1?= =?us-ascii?Q?0=2F=2Fey9w20x9JoiKiYrBcEb2adg=3D=3D?= To: ruby-core@ml.ruby-lang.org X-Entity-ID: u001.I8uzylDtAfgbeCOeLBYDww== Message-ID-Hash: 2GMZRYSSSVQEGJLEEERAGMOKTFB2UJAY X-Message-ID-Hash: 2GMZRYSSSVQEGJLEEERAGMOKTFB2UJAY 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:118938] [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: "Dan0042 (Daniel DeLorme) via ruby-core" Cc: "Dan0042 (Daniel DeLorme)" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Issue #20693 has been updated by Dan0042 (Daniel DeLorme). What about changing/fixing `stat.writable?` to behave like `File.writable?` It seems to me a source of confusion and subtle bugs that these two methods can return different values in edge cases. ---------------------------------------- Bug #20693: Dir.tmpdir should perform a real access check before warning about writability https://bugs.ruby-lang.org/issues/20693#change-109507 * Author: kjtsanaktsidis (KJ Tsanaktsidis) * Status: Open * 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/