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[proxmox.com] Subject: Re: [pbs-devel] [RFC backup 0/6] Two factor authentication X-BeenThere: pbs-devel@lists.proxmox.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: Proxmox Backup Server development discussion <pbs-devel.lists.proxmox.com> List-Unsubscribe: <https://lists.proxmox.com/cgi-bin/mailman/options/pbs-devel>, <mailto:pbs-devel-request@lists.proxmox.com?subject=unsubscribe> List-Archive: <http://lists.proxmox.com/pipermail/pbs-devel/> List-Post: <mailto:pbs-devel@lists.proxmox.com> List-Help: <mailto:pbs-devel-request@lists.proxmox.com?subject=help> List-Subscribe: <https://lists.proxmox.com/cgi-bin/mailman/listinfo/pbs-devel>, <mailto:pbs-devel-request@lists.proxmox.com?subject=subscribe> X-List-Received-Date: Wed, 02 Dec 2020 13:09:56 -0000 On Wed, Dec 02, 2020 at 01:59:31PM +0100, Wolfgang Bumiller wrote: > > > On 12/02/2020 1:48 PM Oguz Bektas <o.bektas@proxmox.com> wrote: > > > > > > On Wed, Dec 02, 2020 at 01:34:25PM +0100, Thomas Lamprecht wrote: > > > On 02.12.20 13:27, Thomas Lamprecht wrote: > > > > - file could get leaked in a backup etc., giving everyone's tfa secrets > > > > and/or recovery keys to attackers (bypass everything) > > > > > > for the record, that does *not* "bypass everything", it's a *second* factor > > > after all. > > > > yes "bypass everything" was a bit of overstatement on my end.. :) > > > Further, if recovery keys are hashed they do not leak information. > > the totp secrets are stored without hashing or encryption so it'd bypass > > that one if file is leaked etc. > > > For others it varies, but I do not like that sort of blanket statement without > > > implying any reasonable vector at all, we and most unix system have such > > > information in one place /etc/shadow, our shadow in /etc/pve/ and consorts, > > > it needs clear documentation about what files are sensible (you should send a > > > patch for that) but that's it. > > > (and as said, splitting it up will not avoid leaking all of them in a backup vs. just > > > one of it). > > i was also thinking if it's a good idea to use a symmetric algorithm to > > encrypt the json file with that user's password. it would help in > > backup leak or similar cases, but could also be overhead (need to > > decrypt/encrypt the file everytime it's changed, need to re-encrypt if > > user changes password etc.) > > If you mean the hash we store, then I'm against it, simply because the key > is lying right next to it. > If you mean the user's *actual* password, then yes > * we'd need to query the user's password even to just list the current TFA entries > * a lost password automatically means you have to re-register your second factors. > (Not *much* of a problem, but kind of weird.) > * root could not read nor modify a user's tfa entries (also not a problem, but weird) yeah... > > A mixed approach would keep the description & metadata in plaintext and store the > secrets in an encrypted form with an AAD cipher. But the only thing benefiting from > this really would be the TOTP entries. WA uses asymmetric cryptography already, > and if we hash the recovery keys, those should be okay, too. but this actually would make sense, i like that approach as it would solve the issues you previously pointed out and keep it relatively secure (very much in comparison to just keeping the secrets in plaintext) > > > _______________________________________________ > pbs-devel mailing list > pbs-devel@lists.proxmox.com > https://lists.proxmox.com/cgi-bin/mailman/listinfo/pbs-devel > >