From patchwork Tue Aug 20 00:17:40 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Garrett X-Patchwork-Id: 11102435 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 9092F1395 for ; Tue, 20 Aug 2019 00:20:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 664A922CF4 for ; Tue, 20 Aug 2019 00:20:32 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="S/h/Sfns" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728910AbfHTASW (ORCPT ); Mon, 19 Aug 2019 20:18:22 -0400 Received: from mail-vs1-f73.google.com ([209.85.217.73]:37717 "EHLO mail-vs1-f73.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728887AbfHTASW (ORCPT ); Mon, 19 Aug 2019 20:18:22 -0400 Received: by mail-vs1-f73.google.com with SMTP id r17so1392354vsp.4 for ; Mon, 19 Aug 2019 17:18:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=010QS9WoWtGoiC1ndkOQ/THJSGP3hTPvp7YVgOrBMsw=; b=S/h/SfnsgFfAPrl/AMQC0M7+bE6qZ2UhyS+NlB+ZHqJgnkxWzZCNeJz6TfFSHpI3b/ WNN4+TiYxCgDaDddsL95FRicBBIij+z1M9yenWIJ4HjBjTBspEIFA2vPk0Sz0ipY84t1 IlhTIsS429DAEC2qUVfOBOokIi/VJjAeeiiADtx2DDSt8luPO7dOH+jf9NwRpCG3BtFv eEmzOiqiMwwe9DpMtd7xo4xxUaPKi76MJqJqb5M4WQuRh5Hli/DB6P9BQgN8trWC1gL7 j4U7P2Yxxv9Ee3ddEPp/VQV1voaUNznzhDu3qaLAzTLpiVxRdQCI2vL/owBk6K3uOtCX wFIw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=010QS9WoWtGoiC1ndkOQ/THJSGP3hTPvp7YVgOrBMsw=; b=fL0eg6xX+FUn/UiZLpZqeyMXtO5TuiATgLH7otix8eA8gnE/NYa5exNz4BEUmsL/Fg eDOYydvilQYkWciXxmiQaUQqL/b3rQKJydQhPmDFPPwDrmr3Jh8I7uqdDhIdsrfSMq0S BVLUc28JKSpPwvqovAiVxXv5XSEBePKpbvLi614veuE2swrl8cvWz5FnBixb/ZzDUCHC Z2IFDtmRANex/E/cvkQ9GIS3Rl/mA/g597nTVldMg99FRGYfiA2Ujm463ILs/rzxLOaL v3Q8o2KMW0LnNqIRp2TuWIsevGmMQ708uPDlmhJ4z1YbvM0Hb3pdAqtVX1nsrVdQgSkD Iu/A== X-Gm-Message-State: APjAAAVZrlqJgEXDyds9kQvOmxkGJUcQx365FUk7jAgXk60QKpjz+JoT COY74pFBCnmB9p1s0Y0dL9WoSzwSH2MPXeaN3zak7w== X-Google-Smtp-Source: APXvYqxAssp7SU+dLaaXmcm2AenK7QOgvuf2jsiQEsQiaYrXPIys5VI0nS54KZNc5aFnofVRdbSADDB+iCNU76/o7QGAhg== X-Received: by 2002:a1f:ec41:: with SMTP id k62mr9132584vkh.32.1566260300517; Mon, 19 Aug 2019 17:18:20 -0700 (PDT) Date: Mon, 19 Aug 2019 17:17:40 -0700 In-Reply-To: <20190820001805.241928-1-matthewgarrett@google.com> Message-Id: <20190820001805.241928-5-matthewgarrett@google.com> Mime-Version: 1.0 References: <20190820001805.241928-1-matthewgarrett@google.com> X-Mailer: git-send-email 2.23.0.rc1.153.gdeed80330f-goog Subject: [PATCH V40 04/29] lockdown: Enforce module signatures if the kernel is locked down From: Matthew Garrett To: jmorris@namei.org Cc: linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, David Howells , Matthew Garrett , Kees Cook , Jessica Yu Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: From: David Howells If the kernel is locked down, require that all modules have valid signatures that we can verify. I have adjusted the errors generated: (1) If there's no signature (ENODATA) or we can't check it (ENOPKG, ENOKEY), then: (a) If signatures are enforced then EKEYREJECTED is returned. (b) If there's no signature or we can't check it, but the kernel is locked down then EPERM is returned (this is then consistent with other lockdown cases). (2) If the signature is unparseable (EBADMSG, EINVAL), the signature fails the check (EKEYREJECTED) or a system error occurs (eg. ENOMEM), we return the error we got. Note that the X.509 code doesn't check for key expiry as the RTC might not be valid or might not have been transferred to the kernel's clock yet. [Modified by Matthew Garrett to remove the IMA integration. This will be replaced with integration with the IMA architecture policy patchset.] Signed-off-by: David Howells Signed-off-by: Matthew Garrett Reviewed-by: Kees Cook Cc: Jessica Yu Signed-off-by: James Morris --- include/linux/security.h | 1 + init/Kconfig | 5 +++++ kernel/module.c | 37 +++++++++++++++++++++++++++++------- security/lockdown/Kconfig | 1 + security/lockdown/lockdown.c | 1 + 5 files changed, 38 insertions(+), 7 deletions(-) diff --git a/include/linux/security.h b/include/linux/security.h index 74787335d9ce..9e8abb60a99f 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -103,6 +103,7 @@ enum lsm_event { */ enum lockdown_reason { LOCKDOWN_NONE, + LOCKDOWN_MODULE_SIGNATURE, LOCKDOWN_INTEGRITY_MAX, LOCKDOWN_CONFIDENTIALITY_MAX, }; diff --git a/init/Kconfig b/init/Kconfig index 0e2344389501..e6069368f278 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1939,6 +1939,11 @@ config MODULE_SIG kernel build dependency so that the signing tool can use its crypto library. + You should enable this option if you wish to use either + CONFIG_SECURITY_LOCKDOWN_LSM or lockdown functionality imposed via + another LSM - otherwise unsigned modules will be loadable regardless + of the lockdown policy. + !!!WARNING!!! If you enable this option, you MUST make sure that the module DOES NOT get stripped after being signed. This includes the debuginfo strip done by some packagers (such as rpmbuild) and diff --git a/kernel/module.c b/kernel/module.c index 80c7c09584cf..2206c08a5e10 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -2753,8 +2753,9 @@ static inline void kmemleak_load_module(const struct module *mod, #ifdef CONFIG_MODULE_SIG static int module_sig_check(struct load_info *info, int flags) { - int err = -ENOKEY; + int err = -ENODATA; const unsigned long markerlen = sizeof(MODULE_SIG_STRING) - 1; + const char *reason; const void *mod = info->hdr; /* @@ -2769,16 +2770,38 @@ static int module_sig_check(struct load_info *info, int flags) err = mod_verify_sig(mod, info); } - if (!err) { + switch (err) { + case 0: info->sig_ok = true; return 0; - } - /* Not having a signature is only an error if we're strict. */ - if (err == -ENOKEY && !is_module_sig_enforced()) - err = 0; + /* We don't permit modules to be loaded into trusted kernels + * without a valid signature on them, but if we're not + * enforcing, certain errors are non-fatal. + */ + case -ENODATA: + reason = "Loading of unsigned module"; + goto decide; + case -ENOPKG: + reason = "Loading of module with unsupported crypto"; + goto decide; + case -ENOKEY: + reason = "Loading of module with unavailable key"; + decide: + if (is_module_sig_enforced()) { + pr_notice("%s is rejected\n", reason); + return -EKEYREJECTED; + } - return err; + return security_locked_down(LOCKDOWN_MODULE_SIGNATURE); + + /* All other errors are fatal, including nomem, unparseable + * signatures and signature check failures - even if signatures + * aren't required. + */ + default: + return err; + } } #else /* !CONFIG_MODULE_SIG */ static int module_sig_check(struct load_info *info, int flags) diff --git a/security/lockdown/Kconfig b/security/lockdown/Kconfig index 7a1d213227a4..e84ddf484010 100644 --- a/security/lockdown/Kconfig +++ b/security/lockdown/Kconfig @@ -1,6 +1,7 @@ config SECURITY_LOCKDOWN_LSM bool "Basic module for enforcing kernel lockdown" depends on SECURITY + select MODULE_SIG if MODULES help Build support for an LSM that enforces a coarse kernel lockdown behaviour. diff --git a/security/lockdown/lockdown.c b/security/lockdown/lockdown.c index 7172ad75496b..d8e42125a5dd 100644 --- a/security/lockdown/lockdown.c +++ b/security/lockdown/lockdown.c @@ -18,6 +18,7 @@ static enum lockdown_reason kernel_locked_down; static char *lockdown_reasons[LOCKDOWN_CONFIDENTIALITY_MAX+1] = { [LOCKDOWN_NONE] = "none", + [LOCKDOWN_MODULE_SIGNATURE] = "unsigned module loading", [LOCKDOWN_INTEGRITY_MAX] = "integrity", [LOCKDOWN_CONFIDENTIALITY_MAX] = "confidentiality", };