From patchwork Thu Aug 8 00:06:56 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Garrett X-Patchwork-Id: 11082985 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 558991709 for ; Thu, 8 Aug 2019 00:09:45 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 4616128AAE for ; Thu, 8 Aug 2019 00:09:45 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 39BB228AC6; Thu, 8 Aug 2019 00:09:45 +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 BEB0028AAE for ; Thu, 8 Aug 2019 00:09:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730634AbfHHAHg (ORCPT ); Wed, 7 Aug 2019 20:07:36 -0400 Received: from mail-pg1-f201.google.com ([209.85.215.201]:36122 "EHLO mail-pg1-f201.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730635AbfHHAHf (ORCPT ); Wed, 7 Aug 2019 20:07:35 -0400 Received: by mail-pg1-f201.google.com with SMTP id y7so7474920pgq.3 for ; Wed, 07 Aug 2019 17:07:35 -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=u2905WeoBzsTcUqrWVSX7p6zMJ6qFdPBK2S0ptkFjO4=; b=VoR40voXGZ4r3EI7oQ5TJp8v2YX39brgb6d/zSs8ft4hklym8/Gt2a9+o//N9qLOFE lL6d+hjXYM0ZfhO+JnOxPtMKcWI9ufmjAi1pqwnizkXVz3zYxdkgQjIR1X0RkHyrspZ7 n+ULWEiaxWUUmkq6xJrie3FKlqw8wqf8m17SkFtTyX+bobwjSvbQl+w/6TWNvSUHZKqJ GAnEr/kt4WthH2MCiRcvNlAHaYXhmg0G4eRma/ptAee5bJusZYJnxdpEUf6wSgY/KjwJ AkJWag1ewJUIEDQXVqTbfGIG6/Y0zDemscTSwNyJCkT6GUOWGkukpVtf/FxaDBHt7M1e NSdQ== 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=u2905WeoBzsTcUqrWVSX7p6zMJ6qFdPBK2S0ptkFjO4=; b=fYTSYAFlz1NQXTiQW+HtYQMtgnQLKVsV3PHOBZ5JBgJdmk/pj/a6UGrVr7VlbAAqfC nr+F5rC9hi7uo9hQrAYOt1CW3ZdTAI4xVz3npvnbQTH/wC3bAwqJFYfx5mGjaEKnzEEn d6wzxuh834VoNcsBzNcWv6nDojRFHgW7OQdFmn2Vya85y/h2LPRYy+2NTEhKG32MPa/A nPSUN4IrWKO5QzIu8oa3dIhHcTuv/E0DVNDyZ/SezU1uAA+xzapEnO8X6CifGwylry+e iefdgjf6lYrnoyFs+Tu7Rtm3to20A1G5x4H33vYPQmTOtxi7UXl+GlC/pm9oLJH45vc7 RKmw== X-Gm-Message-State: APjAAAX0TxM0nZDpM6HbjAvqZZ9thl9cNA2CkU21tgHeuARTK9uIhUMe 1Pal2RBsMylDzbPIQvKDh2zoeebar60gmoOEkQHusg== X-Google-Smtp-Source: APXvYqyR4AfaEXJW2ENR7zwCKUIvKwO1QMtq0y+rmGIcu67Yrsi7oIJ0VRtdvsK+tFTLWpJIe/+Jj+iYyJyKasMUao2L5A== X-Received: by 2002:a63:9249:: with SMTP id s9mr9774501pgn.356.1565222854591; Wed, 07 Aug 2019 17:07:34 -0700 (PDT) Date: Wed, 7 Aug 2019 17:06:56 -0700 In-Reply-To: <20190808000721.124691-1-matthewgarrett@google.com> Message-Id: <20190808000721.124691-5-matthewgarrett@google.com> Mime-Version: 1.0 References: <20190808000721.124691-1-matthewgarrett@google.com> X-Mailer: git-send-email 2.22.0.770.g0f2c4a37fd-goog Subject: [PATCH V38 04/29] 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 + kernel/module.c | 37 +++++++++++++++++++++++++++++------- security/lockdown/lockdown.c | 1 + 3 files changed, 32 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/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/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", };