From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from firstgate.proxmox.com (firstgate.proxmox.com [IPv6:2a01:7e0:0:424::9]) by lore.proxmox.com (Postfix) with ESMTPS id 0D4C71FF394 for ; Mon, 3 Jun 2024 11:00:58 +0200 (CEST) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id 107A21E2D8; Mon, 3 Jun 2024 11:01:26 +0200 (CEST) Date: Mon, 3 Jun 2024 11:00:51 +0200 From: Wolfgang Bumiller To: Gabriel Goller Message-ID: <4jt24gf7mcf7mt4a6isoz3szpq5f3pqpflsj55ti2itprzwpyz@mie5xdspzcqb> References: <20240523112559.257547-1-s.sterz@proxmox.com> <20240523114647.g7tf64ins3hhh5e6@luna.proxmox.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20240523114647.g7tf64ins3hhh5e6@luna.proxmox.com> X-SPAM-LEVEL: Spam detection results: 0 AWL 0.090 Adjusted score from AWL reputation of From: address BAYES_00 -1.9 Bayes spam probability is 0 to 1% DMARC_MISSING 0.1 Missing DMARC policy KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record T_SCC_BODY_TEXT_LINE -0.01 - Subject: Re: [pbs-devel] [PATCH proxmox-backup] auth: add locking to `PbsAuthenticator` to avoid race conditions X-BeenThere: pbs-devel@lists.proxmox.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: Proxmox Backup Server development discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Proxmox Backup Server development discussion Cc: Proxmox Backup Server development discussion Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: pbs-devel-bounces@lists.proxmox.com Sender: "pbs-devel" On Thu, May 23, 2024 at 01:46:47PM GMT, Gabriel Goller wrote: > On 23.05.2024 13:25, Shannon Sterz wrote: > > currently we don't lock the shadow file when removing or storing a > > password. by adding locking here we avoid a situation where storing > > and/or removing a password concurrently could lead to a race > > condition. in this scenario it is possible that a password isn't > > persisted or a password isn't removed. we already do this for > > the "token.shadow" file, so just use the same mechanism here. > > > > Signed-off-by: Shannon Sterz > > Is there any reason why the store_password function does not lock the > shadow.json file? I'm assuming you mean this as an alternative to having a separate file for the locking. In this case the answer is yes: We use `repalce_file()` to store the new version to make sure the update is atomic (and a parallel `authenticat_user` does not read a *partial* file and fail). When you hold a lock on a file and you *replace* it, the new file is a separate thing with no lock on it. Old threads waiting for a lock on the old file will continue when the lock is free, new threads waiting on the lock on the new file will be able to acquire that simultaneously. Iow.: you can't lock something you're *replacing*. _______________________________________________ pbs-devel mailing list pbs-devel@lists.proxmox.com https://lists.proxmox.com/cgi-bin/mailman/listinfo/pbs-devel