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) server-digest SHA256) (No client certificate requested) by dcvr.yhbt.net (Postfix) with ESMTPS id CBA8D1F5CB for ; Thu, 3 Oct 2024 08:52:34 +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=I4SYbE4h; 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=CW4wtmRc; dkim-atps=neutral DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=ml.ruby-lang.org; s=mail; t=1727945552; bh=I/vpjkZ0TRkcjRkO8SuWCj42JWuj3vEu4atww4FhXp8=; 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=I4SYbE4h1BTK6IQYYd/oMccXAale/xgvCkDZ0MvHOJmjfHl7oLit9afAKL+wIzQ2L derBoif9w6np+4FF76MX9sY0vSAX3mTZgEV0+PvkvSOGN8rO6vY9AXMJydiWFETvv0 ExcAPDuUuXJC7QDSBLIqynMvOhr6IOIU0ocv1zNE= Received: from nue.mailmanlists.eu (localhost [IPv6:::1]) by nue.mailmanlists.eu (Postfix) with ESMTP id 9481C43F4B for ; Thu, 3 Oct 2024 08:52:32 +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=CW4wtmRc; 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 5397E43BE9 for ; Thu, 3 Oct 2024 08:52:21 +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=Dq8zpHpkXArAZ36a2Dim0d2sOdGtqO35vOdBaG5fkrk=; b=CW4wtmRc8OPhXPu144Rvmhzw9P/7pQvCOMeyNmT0Rb5dhJowsnpK39UsvN5sjHpjSwVW 8XeiZCWcha4TT0VhQknmxgvOHk4WJVAYN+VYPdWjACLEDnTn9OZgWGOvxwg3C8x/YAkF0w KtYlyFflVhDmdZteHE6H1gXDoKorJwrKd8Yv1SzwDT82oTyKUFW5nl/zO5AZyuvRsk+b6d MEScEkIhItqGXb76RHZKYeMlwCOUOmIkc1iazwSmmTUfvQ0qwxVhdWSc0VMSI1ivqLct9k 7l5tEBuFSDcb0AZZ+hxDHknfYwQB5B8r6RcUQn+Hg79+zSvMJHa+8f6oos0a0kXQ== Received: by recvd-5577bcb48c-xgt5g with SMTP id recvd-5577bcb48c-xgt5g-1-66FE5B43-15 2024-10-03 08:52:19.499265859 +0000 UTC m=+1781692.745779185 Received: from herokuapp.com (unknown) by geopod-ismtpd-20 (SG) with ESMTP id MEbQNRs6QtShRqHSSoRKow for ; Thu, 03 Oct 2024 08:52:19.474 +0000 (UTC) Date: Thu, 03 Oct 2024 08:52:19 +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: mame 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: 96061 X-SG-EID: =?us-ascii?Q?u001=2Ep+ckLDtT+4Y5c+H0YCkEnsuWiCQmn3OZA=2F9FzjoR6ZZlPaMv54M7EFoSM?= =?us-ascii?Q?CX5Trc79ep2R5F+0oYS4n23jq1cv55HQwjzBL7A?= =?us-ascii?Q?hrzoW=2F0JDmfaH65m5sKn6ba3onSq9MgbP2gIGvl?= =?us-ascii?Q?jWGwl99JYvAIt0nafPClNEj34qoXJk51nWbfB=2FE?= =?us-ascii?Q?dV+lCZwZx0zvVipj+6CeCNLKdYnARWQarLdAVo0?= =?us-ascii?Q?ItSnW6bQwYIO82R2LFvzeSfELnaQA6npa1FG3jV?= =?us-ascii?Q?zLxW?= To: ruby-core@ml.ruby-lang.org X-Entity-ID: u001.I8uzylDtAfgbeCOeLBYDww== Message-ID-Hash: C6ETFRGJPV7HJZVUCF4AYDCUPUX2NC5N X-Message-ID-Hash: C6ETFRGJPV7HJZVUCF4AYDCUPUX2NC5N 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:119425] [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: "mame (Yusuke Endoh) via ruby-core" Cc: "mame (Yusuke Endoh)" Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Issue #20693 has been updated by mame (Yusuke Endoh). Assignee set to akr (Akira Tanaka) ---------------------------------------- Bug #20693: Dir.tmpdir should perform a real access check before warning about writability https://bugs.ruby-lang.org/issues/20693#change-110039 * 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/