Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 42F83C43217 for ; Wed, 12 Jan 2022 20:15:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1357381AbiALUPz (ORCPT ); Wed, 12 Jan 2022 15:15:55 -0500 Received: from vps-vb.mhejs.net ([37.28.154.113]:55462 "EHLO vps-vb.mhejs.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1350686AbiALUPy (ORCPT ); Wed, 12 Jan 2022 15:15:54 -0500 Received: from MUA by vps-vb.mhejs.net with esmtps (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.94.2) (envelope-from ) id 1n7k24-0005Dj-Rb; Wed, 12 Jan 2022 21:15:44 +0100 Message-ID: Date: Wed, 12 Jan 2022 21:15:38 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.4.0 Content-Language: en-US To: Roberto Sassu Cc: "keyrings@vger.kernel.org" , "linux-crypto@vger.kernel.org" , "linux-integrity@vger.kernel.org" , "linux-fscrypt@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "zohar@linux.ibm.com" , "ebiggers@kernel.org" , "dhowells@redhat.com" , "dwmw2@infradead.org" , "herbert@gondor.apana.org.au" , "davem@davemloft.net" References: <20220111180318.591029-1-roberto.sassu@huawei.com> From: "Maciej S. Szmigiero" Subject: Re: [PATCH 00/14] KEYS: Add support for PGP keys and signatures In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12.01.2022 10:16, Roberto Sassu wrote: >> From: Maciej S. Szmigiero [mailto:mail@maciej.szmigiero.name] >> Sent: Tuesday, January 11, 2022 9:33 PM >> On 11.01.2022 19:03, Roberto Sassu wrote: >>> Support for PGP keys and signatures was proposed by David long time ago, >>> before the decision of using PKCS#7 for kernel modules signatures >>> verification was made. After that, there has been not enough interest to >>> support PGP too. >>> >>> Lately, when discussing a proposal of introducing fsverity signatures in >>> Fedora [1], developers expressed their preference on not having a separate >>> key for signing, which would complicate the management of the distribution. >>> They would be more in favor of using the same PGP key, currently used for >>> signing RPM headers, also for file-based signatures (not only fsverity, but >>> also IMA ones). >> >> Aren't PGP keys simply RSA / ECC / EdDSA keys with additional metadata? >> Can't they be unwrapped from their (complex) PGP format in userspace and >> loaded raw into the kernel, in a similar way as they are sometimes used >> for SSH authentication? > > Probably, this would be possible by introducing a new asymmetric > key subtype parsing PGP keys and signatures in a more simple format, > after conversion by user space. But still, a parser would be required. > To be honest, I would prefer to implement (actually David did) a > parser following an RFC, than developing a new one. A parser in userspace is preferred to one in kernel since if there is a bug somewhere its consequences are much less severe. And experience shows that parsers are especially prone to bugs. A userspace implementation can also be tightly sandboxed for extra security. There are many existing OpenPGP parsing libraries to choose from. >> This will save us from having to add complex parsers (a well-known source >> of bugs) into the kernel - I guess there aren't any plans to add an >> in-kernel PGP Web of Trust implementation. > > I extensively tested the implementation with an ad-hoc fault injector, > to see if the code can correctly handle errors. I also developed a > fuzzer to corrupt the data before it is read by the kernel. Finally, > I checked that there are not memory leaks. But I agree, there could > still be bugs. > > If you mean that a key can be added to the kernel if is vouched for > by another key in the built-in keyring, I actually implemented this > (was missing in the original implementation). Some keyrings, e.g. .ima, > have this restriction. > > The way this works is that, whenever you add a PGP key to the > kernel, the parser takes not only the public key and the user ID, > but also its signature by the same or another PGP key. > > The signature is verified when the key is added to the keyring > with that restriction, and only if the verification is successful > the key can be added. I understand but it would be great to make use as much as possible of the existing in-kernel signature verification mechanisms. > Roberto Thanks, Maciej