From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from gate001.proxmox.com (gate001.proxmox.com [IPv6:2a0f:8001:1:32::40]) by lore.proxmox.com (Postfix) with ESMTPS id A770D1FF0AF for ; Fri, 06 Nov 2026 18:23:38 +0100 (CET) Received: from gate001.proxmox.com (localhost.localdomain [127.0.0.1]) by gate001.proxmox.com (Proxmox) with ESMTP id 8551C21603; Fri, 06 Nov 2026 18:23:12 +0100 (CET) From: Christian Ebner To: pbs-devel@lists.proxmox.com Subject: [PATCH proxmox-backup v2 16/43] api: backup: fix possible information leak in multi-tenant datastores Date: Fri, 6 Nov 2026 18:22:08 +0100 Message-ID: <20261106172235.890542-17-c.ebner@proxmox.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261106172235.890542-1-c.ebner@proxmox.com> References: <20261106172235.890542-1-c.ebner@proxmox.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Bm-Milter-Handled: 55990f41-d878-4baa-be0a-ee34c49e34d2 X-Bm-Transport-Timestamp: 1793985775692 X-SPAM-LEVEL: Spam detection results: 0 AWL 0.470 Adjusted score from AWL reputation of From: address DMARC_MISSING 0.1 Missing DMARC policy KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment (newer systems) 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 Message-ID-Hash: 5HVGZIWFVF7AU5WPMAWIVF55J7RSAYBC X-Message-ID-Hash: 5HVGZIWFVF7AU5WPMAWIVF55J7RSAYBC X-MailFrom: c.ebner@proxmox.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; loop; banned-address; emergency; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header X-Mailman-Version: 3.3.10 Precedence: list List-Id: Proxmox Backup Server development discussion List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: Do not leak the owner of the group in permission checks on backup, as a user with Datastore.Backup only permissions should never be able to see other users. This is especially of interest if users gained unintended access to a namespace they should not be allowed to, e.g. due to misconfiguration. Rather include the namespace and group information. Signed-off-by: Christian Ebner --- src/api2/backup/mod.rs | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/src/api2/backup/mod.rs b/src/api2/backup/mod.rs index a9b1ca5c2..ad8794f05 100644 --- a/src/api2/backup/mod.rs +++ b/src/api2/backup/mod.rs @@ -156,8 +156,13 @@ fn upgrade_to_backup_protocol( let correct_owner = owner == auth_id || (owner.is_token() && Authid::from(owner.user().clone()) == auth_id); if !correct_owner && worker_type != "benchmark" { + let namespace_and_group = if !backup_group.backup_ns().is_root() { + format!("[{}]:{}", backup_group.backup_ns(), backup_group.group()) + } else { + backup_group.group().to_string() + }; // only the owner is allowed to create additional snapshots - bail!("backup owner check failed ({} != {})", auth_id, owner); + bail!("backup owner check failed: {namespace_and_group} not owned by {auth_id}"); } let last_backup = { -- 2.47.3