From patchwork Thu Feb 28 23:11:39 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Garrett X-Patchwork-Id: 10834231 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 534A4139A for ; Thu, 28 Feb 2019 23:12:15 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 40F062FC3B for ; Thu, 28 Feb 2019 23:12:15 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 31EF92FC45; Thu, 28 Feb 2019 23:12:15 +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 9A2ED2FC3B for ; Thu, 28 Feb 2019 23:12:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387507AbfB1XMN (ORCPT ); Thu, 28 Feb 2019 18:12:13 -0500 Received: from mail-pg1-f201.google.com ([209.85.215.201]:39495 "EHLO mail-pg1-f201.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387476AbfB1XMN (ORCPT ); Thu, 28 Feb 2019 18:12:13 -0500 Received: by mail-pg1-f201.google.com with SMTP id 202so16152936pgb.6 for ; Thu, 28 Feb 2019 15:12:12 -0800 (PST) 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=QtKsyYHiwCWU5yiWJciggoAD1nlqNR9ctuqeDCsYWKI=; b=rzfnYNTLJA1ZeFACBysiRXmHvQrizAgydUJTNEp1PKJ8dFuZNs5aYF6JbQjMRRcRYN oHDRL39qxkz+uZfepJbEY4U9l0frA6ZXMkZa0M0Xe4EQ0oYnw9XB6AmoBQTqqc4ZTwaJ veSnNaJ4T17FTfFup/RE83ghYUXl6JZvfzdRz8hWeMfN8swjSixWObHc8Dc64zFCo8b9 8uMbyjrYaKXIvsfxU5pr6KjJKfIj7pjXybNjMlogwX/2HfuslhAuluVTjvOXUmTJBfMe fcbiINkIL2McwoDvK4XpTKTShrAb9mASZmYeH7C3XrRC9coYp5oJ2WbZLv3IOEcuys0z DPtw== 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=QtKsyYHiwCWU5yiWJciggoAD1nlqNR9ctuqeDCsYWKI=; b=NticleZKNS1QbnrZ6tFUG3M+kkdNOP+sIZ4WCVThP9pt27tf0iXDIS3Ascf40IM+ih 91AgiS7n49qbAU68pgg+MxYoIaTNV4Ikq4dwkFrZInxPZ+XSqTXVLgMb3O1re2uBwI+I TpdJ8kchzuH03ipS26+azmEAKA4Pkt6XcrhdR0MJpv6W/x8szDjj7RwO098zUdHhbk+4 2MhyOXj7BrUosrnGcRJC3qy0OyUz5oL68WwFjRt2hzLHp9Usorgx+H/HEI2Hu6K6QHKG K1hT2XMm+h889rZ1fuJJeyRaFqAD2X8QT6ts/nMIPGX4qQcDYIfTJQZsMQ+5XLLtShEZ K3WA== X-Gm-Message-State: AHQUAuancHnGoWDMXcUa3YaLeILg7vLqf0c5vmuFF6aTDD6zsQjsKzDg I3EGQ1MV3wuG1YM/2gQZEXzjKOAMDskRErxcssY2tw== X-Google-Smtp-Source: APXvYqxTdLxxvHRUxrP6dBjOqmshkQpbu3yKcYUfKStvLjNRtJ1u9wNINweXDLZgeOP8DXPUtfKeahlCufSsmmEwMAmy6A== X-Received: by 2002:a62:ac0f:: with SMTP id v15mr973328pfe.148.1551395531818; Thu, 28 Feb 2019 15:12:11 -0800 (PST) Date: Thu, 28 Feb 2019 15:11:39 -0800 In-Reply-To: <20190228231203.212359-1-matthewgarrett@google.com> Message-Id: <20190228231203.212359-3-matthewgarrett@google.com> Mime-Version: 1.0 References: <20190228231203.212359-1-matthewgarrett@google.com> X-Mailer: git-send-email 2.21.0.352.gf09ad66450-goog Subject: [PATCH 03/27] 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, dhowells@redhat.com 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 or that IMA can validate the file. 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 IMA will have validated the image, return 0 (okay). (c) 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. Signed-off-by: David Howells Reviewed-by: Jiri Bohac cc: "Lee, Chun-Yi" cc: James Morris --- kernel/module.c | 56 +++++++++++++++++++++++++++++++++++++------------ 1 file changed, 43 insertions(+), 13 deletions(-) diff --git a/kernel/module.c b/kernel/module.c index 2ad1b5239910..afa5489be39f 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -64,6 +64,7 @@ #include #include #include +#include #include #include "module-internal.h" @@ -2765,10 +2766,12 @@ static inline void kmemleak_load_module(const struct module *mod, #endif #ifdef CONFIG_MODULE_SIG -static int module_sig_check(struct load_info *info, int flags) +static int module_sig_check(struct load_info *info, int flags, + bool can_do_ima_check) { - int err = -ENOKEY; + int err = -ENODATA; const unsigned long markerlen = sizeof(MODULE_SIG_STRING) - 1; + const char *reason; const void *mod = info->hdr; /* @@ -2783,19 +2786,46 @@ 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; + if (can_do_ima_check && is_ima_appraise_enabled()) + return 0; + if (kernel_is_locked_down(reason)) + return -EPERM; + return 0; + + /* 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) +static int module_sig_check(struct load_info *info, int flags, + bool can_do_ima_check) { return 0; } @@ -3658,7 +3688,7 @@ static int unknown_module_param_cb(char *param, char *val, const char *modname, /* Allocate and load the module: note that size of section 0 is always zero, and we rely on this for optional sections. */ static int load_module(struct load_info *info, const char __user *uargs, - int flags) + int flags, bool can_do_ima_check) { struct module *mod; long err = 0; @@ -3677,7 +3707,7 @@ static int load_module(struct load_info *info, const char __user *uargs, goto free_copy; } - err = module_sig_check(info, flags); + err = module_sig_check(info, flags, can_do_ima_check); if (err) goto free_copy; @@ -3872,7 +3902,7 @@ SYSCALL_DEFINE3(init_module, void __user *, umod, if (err) return err; - return load_module(&info, uargs, 0); + return load_module(&info, uargs, 0, false); } SYSCALL_DEFINE3(finit_module, int, fd, const char __user *, uargs, int, flags) @@ -3899,7 +3929,7 @@ SYSCALL_DEFINE3(finit_module, int, fd, const char __user *, uargs, int, flags) info.hdr = hdr; info.len = size; - return load_module(&info, uargs, flags); + return load_module(&info, uargs, flags, true); } static inline int within(unsigned long addr, void *start, unsigned long size)