From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from firstgate.proxmox.com (firstgate.proxmox.com [212.224.123.68]) by lore.proxmox.com (Postfix) with ESMTPS id 9C0AC1FF16B for ; Thu, 29 Aug 2024 14:09:51 +0200 (CEST) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id 39BD61B8A0; Thu, 29 Aug 2024 14:10:20 +0200 (CEST) Date: Thu, 29 Aug 2024 14:10:15 +0200 From: Gabriel Goller To: Wolfgang Bumiller Message-ID: <20240829121015.algd2p2b57bswkog@luna.proxmox.com> References: <20240823091215.124453-1-g.goller@proxmox.com> <20240829103122.ainqdg2k3ewqfd5y@luna.proxmox.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20220429 X-SPAM-LEVEL: Spam detection results: 0 AWL -0.042 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] proxy: check permissions on proxy.key and proxy.pem files 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: pbs-devel@lists.proxmox.com Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: pbs-devel-bounces@lists.proxmox.com Sender: "pbs-devel" On 29.08.2024 13:22, Wolfgang Bumiller wrote: >On Thu, Aug 29, 2024 at 12:31:22PM GMT, Gabriel Goller wrote: >> On 27.08.2024 11:37, Wolfgang Bumiller wrote: >> > NAK >> > >> > On Fri, Aug 23, 2024 at 11:12:15AM GMT, Gabriel Goller wrote: >> > > Check the owner and permission of the proxy.key and proxy.pem files. >> > > This avoids openssl's unhelpful error message and prints a nicer one. >> > > >> > > Motivation: https://forum.proxmox.com/threads/proxmox-backup-tailscale-proxmox-backup-proxy-service-wont-boot.153204 >> > > >> > > Signed-off-by: Gabriel Goller >> > > --- >> > > >> > > Note: not sure about the correct permissions, we currently default to >> > > 640, but maybe a minimum of 400 is enough? >> > > >> > > src/bin/proxmox-backup-proxy.rs | 27 +++++++++++++++++++++++++++ >> > > 1 file changed, 27 insertions(+) >> > > >> > > diff --git a/src/bin/proxmox-backup-proxy.rs b/src/bin/proxmox-backup-proxy.rs >> > > index 041f3aff999c..544196b8bc5d 100644 >> > > --- a/src/bin/proxmox-backup-proxy.rs >> > > +++ b/src/bin/proxmox-backup-proxy.rs >> > > @@ -367,6 +367,30 @@ async fn run() -> Result<(), Error> { >> > > Ok(()) >> > > } >> > > >> > > +/// Check permissions and owner of passed path. >> > > +fn check_permissions>(path: T, file_mode: u32) -> Result<(), Error> { >> > > + match nix::sys::stat::stat(path.as_ref()) { >> > > + Ok(stat) => { >> > > + if stat.st_uid != u32::from(pbs_config::backup_user()?.uid) >> > > + || stat.st_gid != u32::from(pbs_config::backup_group()?.gid) >> > > + || stat.st_mode & 0o770 < file_mode >> > >> > If you want to test whether you can open a file, you should either just >> > `open(2)` it, or, if you really want to avoid it, use `access(2)`. >> > You do not ever want to attempt to try to perform the kernel's >> > permission checks yourself. There could be ACLs, AppArmor profiles, ... >> > and while we can say that, for now, this is not supposed to be the case, >> > it's bad practice in general. >> > >> > Also note that this only covers the case at a point in time where the >> > certificate isn't actually loaded, and won't help with changes to the >> > permissions while a daemon is already running. >> > >> > A better approach to handle this specific case would be to adapt >> > `proxmox-rest-server`'s handling of `Tls::PemFiles` so that instead of >> > using `openssl`'s ".set_private_key_file()` convenience methods, it >> > loads the files, and handles `EPERM`/`ENOENT`/... with useful error >> > messags, and then uses >> > `acceptor.set_private_key(PKey::private_key_from_pem(data)?)` >> >> I agree. >> We can use the function you mentioned for the private key (and it >> works!), but not for the certificate. AFAICT (and I know nothing about >> openssl) there is no use_certificate_chain() function, so the >> certificate chain can only be loaded using a path [0]. This seems kinda >> weird, as all the other functions have path and file-content flavors, >> but this one hasn't. >> >> Nevertheless we could just forget about the certificate or we could do >> a open() and close() to check the permissions? > >That's unfortunate. However, I think it's usually only the key that gets >strict permissions, not the certificate, since it's meant to be public >anyway. > >In theory, I think `.set_certificate()` + `.add_extra_chain_cert()` >should work iterating through the certificates from >`X509::stack_from_pem()`, but this would need careful testing to make >sure the full chain is properly visible. Yes, this would be quite tricky to get right. >Simply doing an `open()+close()` before calling the >`set_certificate_chain_file()` is probably okay for now. Will do! 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