From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from firstgate.proxmox.com (firstgate.proxmox.com [212.224.123.68]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by lists.proxmox.com (Postfix) with UTF8SMTPS id DFAA669861 for ; Wed, 3 Mar 2021 08:28:12 +0100 (CET) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with UTF8SMTP id CFC2F33150 for ; Wed, 3 Mar 2021 08:27:42 +0100 (CET) Received: from proxmox-new.maurer-it.com (proxmox-new.maurer-it.com [212.186.127.180]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by firstgate.proxmox.com (Proxmox) with UTF8SMTPS id A6D0933141 for ; Wed, 3 Mar 2021 08:27:41 +0100 (CET) Received: from proxmox-new.maurer-it.com (localhost.localdomain [127.0.0.1]) by proxmox-new.maurer-it.com (Proxmox) with UTF8SMTP id 6BAD342741 for ; Wed, 3 Mar 2021 08:27:41 +0100 (CET) Message-ID: Date: Wed, 3 Mar 2021 08:27:40 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:87.0) Gecko/20100101 Thunderbird/87.0 Content-Language: en-US To: Proxmox Backup Server development discussion References: <20210302153120.31213-1-d.csapak@proxmox.com> From: Dominik Csapak In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-SPAM-LEVEL: Spam detection results: 0 AWL 0.201 Adjusted score from AWL reputation of From: address KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment NICE_REPLY_A -0.001 Looks like a legit reply (A) RCVD_IN_DNSWL_MED -2.3 Sender listed at https://www.dnswl.org/, medium trust SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record Subject: Re: [pbs-devel] [RFC PATCH proxmox-backup] server/rest: disallow non-protected api calls in privileged environment 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: , X-List-Received-Date: Wed, 03 Mar 2021 07:28:12 -0000 On 3/3/21 08:07, Thomas Lamprecht wrote: > On 02.03.21 18:02, Thomas Lamprecht wrote: >> On 02.03.21 16:31, Dominik Csapak wrote: >>> to prevent potential abuse of non-protected api calls as root >>> >> >> this breaks important CLI tools using client::connect_to_localhost >> i.e., proxmox-backup-manager and proxmox-tape and maybe others which >> connect still manually. >> > > Ok, this is not true, I had in mind that we directly connect to :82, like > we did for pvesh way in the past. > >>> Signed-off-by: Dominik Csapak >>> --- >>> this is a rather theoretical security improvement, i am not sure if we >>> want this? it would only guard against an unprotected api call that somehow >> >> no, such stuff only tends to break things while not providing any value... >> lets keep theoretical security improvements also theoretical.. >> >>> allows code execution. this could then be abused to connect to the >>> daemon and reabuse the same api call, but with root permissions >> >> with magically generating a ticket and circumventing permission checks >> how exactly? >> > > Security wise I find this still nonsense, its way too constructed with no > single practical possible example state, and it effectively requires to have > a free-choose binary path or control of $PATH from the environment of that > process (if that is given you have other problems) plus local access to the > machine and a entry in PBS user config would be required. > > But, one thing this could help with is the issue that we sometimes had that > doing creating a config file as privileged user got us the wrong permissions, > making it inaccessible for the unprivileged code, which was a bug but not > always immediately found, we have all cases covered with chown+checks, IIRC, > but if a new config came in this could help detection (albeit such things > are quite visible, normally) > yeah as i admitted, the vector is rather theoretical, but just maybe to explain better: * i have access to an non-protected api call '/foo' (if thats unauthenticated or not does not matter) * that api call has a code execution vuln (e.g. in perl system('foo $param') * now i can execute code as backup user * with that i can now connect to localhost:82 and reuse the same api call with the same vuln again -> exec as root but yes, rather constructed scenario... thanks anyway for looking and commenting :)