From patchwork Fri Aug 9 20:59:49 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Garrett X-Patchwork-Id: 11087599 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 9BD511399 for ; Fri, 9 Aug 2019 20:59:59 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 87857205F8 for ; Fri, 9 Aug 2019 20:59:59 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 79FF920881; Fri, 9 Aug 2019 20:59:59 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-14.5 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,RCVD_IN_DNSWL_HI,USER_IN_DEF_DKIM_WL autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id E3259205F8 for ; Fri, 9 Aug 2019 20:59:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727731AbfHIU76 (ORCPT ); Fri, 9 Aug 2019 16:59:58 -0400 Received: from mail-qt1-f202.google.com ([209.85.160.202]:52109 "EHLO mail-qt1-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726219AbfHIU76 (ORCPT ); Fri, 9 Aug 2019 16:59:58 -0400 Received: by mail-qt1-f202.google.com with SMTP id m25so89702576qtn.18 for ; Fri, 09 Aug 2019 13:59:57 -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=1dUG1NMCpkV2WkKZesUQVb6Dz7CzfhUj65K8G9Towq4=; b=T7WQoCZKX7Wq+UOhImXZEoVPZhkCpjMeQFTB9tRdBWSAF3obYVvznl50aJhWDlSS44 fi4dAIYKDDRWAWH0KxgLzbfaz3zBBcXkS6yVHh6srQvVY6UN2y63DBDlrPClVdmBea5K l/gs5qun2op7KvgFX4k1vbaSqzykPTVmmT6UCfQQu2LGBaez8GMBdlj+YBdkPkknYrj6 VmjoxwHa9gg+PsuAxhr/cBCAKr17GtEXMDK3MtU1JGhpAAdEpPJLlRuTG/91cPgpgvq0 iFgQ+7V6CCXu11U2SU6cUad0AWrsNXflNu7d1I95XoHK4GyIi5hxLA67j0bzpxuvNSkb 7I1A== 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=1dUG1NMCpkV2WkKZesUQVb6Dz7CzfhUj65K8G9Towq4=; b=cGEOB78iN8UqJ8C6mc6K8BnOyzR/fClaG68xNxLmVPwZhdo2fvb3WE9NT/Av+TrhAO usvYLDnA6PowqFJh8O2Hrp+mD6LQsdGt62f4iXJ46i0mDwms8j4xLxJH3iH7P+OIm31x PxRzyUAjNcIM6aWDOzM2liLa4YxBiDo7+VxbDIv+Zt+OHP0MEWUrYDablIerbiXB7mv3 ddLoZuHpALgIBbTObZHnQDZnmSFLCXA34LDS8tsLTfg460gqeRuKW06E2/kEtQqF/5mT wF7A3HQL5gBiXHTtdnQfH4Q5wTi3KDKEBdXRH+Ebg8Jjx0fWXC3FSMba0oR9SeuHvGfB HGRQ== X-Gm-Message-State: APjAAAWbYOKjdPuq78lPPobvDlUtxYXOfzfYHhb6qF8fkQ/IhWvRvUWu Vig5iG/YbedHlw1y8+2lIgHHBWUmshIvnLUXxAc8XQ== X-Google-Smtp-Source: APXvYqwLZr72bOnQwCmWG8+ZdkXoVNNSRD6ih433tgwJCH1YjGw4l2t+D/BDOflZ1Ia2cUyhpkOtAwiJPQ8IrHpqkGCbUw== X-Received: by 2002:a37:9fc1:: with SMTP id i184mr7769621qke.289.1565384396579; Fri, 09 Aug 2019 13:59:56 -0700 (PDT) Date: Fri, 9 Aug 2019 13:59:49 -0700 In-Reply-To: <20190808100059.GA30260@linux-8ccs> Message-Id: <20190809205949.111398-1-matthewgarrett@google.com> Mime-Version: 1.0 References: <20190808100059.GA30260@linux-8ccs> X-Mailer: git-send-email 2.23.0.rc1.153.gdeed80330f-goog Subject: [PATCH V39] 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: X-Virus-Scanned: ClamAV using ClamSMTP 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 --- 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 54a0532ec12f..8e70063074a1 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 bd7d650d4a99..1f0f53774c3e 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -2017,6 +2017,11 @@ 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 cd8df516666d..318209889e26 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -2771,8 +2771,9 @@ 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; /* @@ -2787,16 +2788,38 @@ 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 7374ba76d8eb..f9dd683261e9 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 d30c4d254b5f..2c53fd9f5c9b 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", };