Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932406AbbESMrE (ORCPT ); Tue, 19 May 2015 08:47:04 -0400 Received: from casper.infradead.org ([85.118.1.10]:52740 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932335AbbESMrA (ORCPT ); Tue, 19 May 2015 08:47:00 -0400 Message-ID: <1432039613.29806.75.camel@infradead.org> Subject: Re: Should we automatically generate a module signing key at all? From: David Woodhouse To: David Howells Cc: Andy Lutomirski , Linus Torvalds , Michal Marek , Abelardo Ricart III , Linux Kernel Mailing List , Sedat Dilek , keyrings@linux-nfs.org, Rusty Russell , LSM List , Borislav Petkov , Jiri Kosina Date: Tue, 19 May 2015 13:46:53 +0100 In-Reply-To: <29742.1432025631@warthog.procyon.org.uk> References: <555A88FB.7000809@kernel.org> <31154.1431965087@warthog.procyon.org.uk> <29742.1432025631@warthog.procyon.org.uk> Content-Type: multipart/signed; micalg="sha-1"; protocol="application/x-pkcs7-signature"; boundary="=-P/Un3H9sNQdMDYDdutAw" X-Mailer: Evolution 3.16.2.1 (3.16.2.1-1.fc22) Mime-Version: 1.0 X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 9494 Lines: 157 --=-P/Un3H9sNQdMDYDdutAw Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Tue, 2015-05-19 at 09:53 +0100, David Howells wrote: >=20 > Just in Fedora 21: >=20 > warthog>rpm -ql kernel-modules | grep [.]ko | wc -l > 3604 > warthog>rpm -ql kernel-modules-extra | grep [.]ko | wc -l > 480 >=20 > So that's >4000 modules, each signed with a SHA256 sum (32 bytes). That'= s > more than 125K of unswappable memory. And it's uncompressible as Dave po= inted > out. And that doesn't include any metadata to match a module to a digest= , but > rather assumes we just scan through the entire list comparing against eac= h > SHA256 sum until we find one that matches. If you *really* wanted to do it, there might be ways round this explosion of data. Perhaps the kernel only contains *one* sha256 =E2=80=95 the sha256 of all t= he sha256's of all the modules. Then when one module is loaded, we also have to pass in a table containing all the other sha256's. The kernel checks the sha256 of what's b= eing loaded, checks it matches what's in the table that was=20 also loaded. And then validates the integrity of that table. I don't much like that idea, mind you. --=20 David Woodhouse Open Source Technology Centre David.Woodhouse@intel.com Intel Corporation --=-P/Un3H9sNQdMDYDdutAw Content-Type: application/x-pkcs7-signature; name="smime.p7s" Content-Disposition: attachment; filename="smime.p7s" Content-Transfer-Encoding: base64 MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAQAAoIISjjCCBicw ggUPoAMCAQICAw3vNzANBgkqhkiG9w0BAQUFADCBjDELMAkGA1UEBhMCSUwxFjAUBgNVBAoTDVN0 YXJ0Q29tIEx0ZC4xKzApBgNVBAsTIlNlY3VyZSBEaWdpdGFsIENlcnRpZmljYXRlIFNpZ25pbmcx ODA2BgNVBAMTL1N0YXJ0Q29tIENsYXNzIDEgUHJpbWFyeSBJbnRlcm1lZGlhdGUgQ2xpZW50IENB MB4XDTE1MDUwNTA5NDM0MVoXDTE2MDUwNTA5NTMzNlowQjEcMBoGA1UEAwwTZHdtdzJAaW5mcmFk ZWFkLm9yZzEiMCAGCSqGSIb3DQEJARYTZHdtdzJAaW5mcmFkZWFkLm9yZzCCASIwDQYJKoZIhvcN AQEBBQADggEPADCCAQoCggEBAMkbm9kPbx1j/X4RVyf/pPKSYwelcco69TvnQQbKM8m8xkWjXJI1 jpJ1jMaGUZGFToINMSZi7lZawUozudWbXSKy1SikENSTJHffsdRAIlsp+hR8vWvjsKUry6sEdqPG 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