From patchwork Thu Aug 8 00:07:00 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Garrett X-Patchwork-Id: 11082977 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 A674113B1 for ; Thu, 8 Aug 2019 00:09:33 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 957D728AAE for ; Thu, 8 Aug 2019 00:09:33 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 8971D28AC6; Thu, 8 Aug 2019 00:09:33 +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 E4C2428AAE for ; Thu, 8 Aug 2019 00:09:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2389567AbfHHAJb (ORCPT ); Wed, 7 Aug 2019 20:09:31 -0400 Received: from mail-pl1-f201.google.com ([209.85.214.201]:41166 "EHLO mail-pl1-f201.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389489AbfHHAHp (ORCPT ); Wed, 7 Aug 2019 20:07:45 -0400 Received: by mail-pl1-f201.google.com with SMTP id ci3so11813648plb.8 for ; Wed, 07 Aug 2019 17:07:45 -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=0e260YowI9CRqgpWSZnFK5vaM3jseidaVbkh9lNaqp8=; b=aQ4wn3P9fS1u1ewjS8eJttkaghjcu/R7h1tnuxyy/xeWvKDpKhjRvgSO7RrLNEHUMU LED5o+fo7q5eEFGAl73Pz60kkKwy/GrW8qw1oEV2SHeE2sI7LIQ4aAFc63hmJEjqA8m4 VT4HU+lTU2wrfeWBNWy8WDDHjMcqhXhNl83ARfBqIbLW0IPeWRAKV5IJJlCrz2yppmDS aULni2rAGpooCIwkn1sqHk0efejrXxf7Mr71tkaQJTJ1IG31RD4g4dKGErCCu1TQy4t9 qw8Ok6B7ti9N0+AqXpyBmDQcEx/zO20mRtWnibGRBhWH8hWl9LVRKnBMyU0RT5aVX/6n NSUg== 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=0e260YowI9CRqgpWSZnFK5vaM3jseidaVbkh9lNaqp8=; b=Zr3ZBimcES73hpkVESU+u0Dl442kAe2QdEec2GUUclPNZX31Nyfh2bYxxnlGK8Vi56 KR2+ot9qan6CjEV+pd+lOh6aQ2RAil+TnIOtQeWXix9rOvvvwgSkmwJ5+dNyvdhak18w eneXsAE4hm0vnKKNreyfEWn33UKDtsbhNbRCLchzA+pqds6CJzBtwKFBTBHWkNAY2BGd XX9de6LDCNfcxW8hI9abVaOb+GPVuNC6koP1oZycpkT6F+RKhxHnlDY4r3P5Ys0PkwR0 gEEhQ/Esle2NoB7xCqYcqFkcbko9VtjDMJgOTLtEAMIm88NicTuZ2TrV/1JBdLiRr13O WPhg== X-Gm-Message-State: APjAAAX/QV3XY2TPXP+B6uFMgJZP3bBSK89I1P/VbOvV/RzN7eRN77Ky mW5HuDjtjgiR2MnuF1Ljw6mgxWTTsvEfdMWZMNnPaA== X-Google-Smtp-Source: APXvYqwZ4ajQSAuE3qXrhA8Gc7seQj1zeG29UnjPxKFv05XUEhTP1zFNAl6GAxE4FJArwTQ46bx/Ulzzlgi1s4LMx+ZfwQ== X-Received: by 2002:a63:f926:: with SMTP id h38mr10014401pgi.80.1565222864875; Wed, 07 Aug 2019 17:07:44 -0700 (PDT) Date: Wed, 7 Aug 2019 17:07:00 -0700 In-Reply-To: <20190808000721.124691-1-matthewgarrett@google.com> Message-Id: <20190808000721.124691-9-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 08/29] kexec_file: split KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE From: Matthew Garrett To: jmorris@namei.org Cc: linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Jiri Bohac , David Howells , Matthew Garrett , Dave Young , kexec@lists.infradead.org Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: X-Virus-Scanned: ClamAV using ClamSMTP From: Jiri Bohac This is a preparatory patch for kexec_file_load() lockdown. A locked down kernel needs to prevent unsigned kernel images from being loaded with kexec_file_load(). Currently, the only way to force the signature verification is compiling with KEXEC_VERIFY_SIG. This prevents loading usigned images even when the kernel is not locked down at runtime. This patch splits KEXEC_VERIFY_SIG into KEXEC_SIG and KEXEC_SIG_FORCE. Analogous to the MODULE_SIG and MODULE_SIG_FORCE for modules, KEXEC_SIG turns on the signature verification but allows unsigned images to be loaded. KEXEC_SIG_FORCE disallows images without a valid signature. Signed-off-by: Jiri Bohac Signed-off-by: David Howells Signed-off-by: Matthew Garrett Reviewed-by: Jiri Bohac Reviewed-by: Dave Young cc: kexec@lists.infradead.org --- arch/x86/Kconfig | 20 +++++++++---- crypto/asymmetric_keys/verify_pefile.c | 4 ++- include/linux/kexec.h | 4 +-- kernel/kexec_file.c | 41 ++++++++++++++++++++++---- 4 files changed, 55 insertions(+), 14 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 05e78acb187c..fd2cd4f861cc 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2032,20 +2032,30 @@ config KEXEC_FILE config ARCH_HAS_KEXEC_PURGATORY def_bool KEXEC_FILE -config KEXEC_VERIFY_SIG +config KEXEC_SIG bool "Verify kernel signature during kexec_file_load() syscall" depends on KEXEC_FILE ---help--- - This option makes kernel signature verification mandatory for - the kexec_file_load() syscall. - In addition to that option, you need to enable signature + This option makes the kexec_file_load() syscall check for a valid + signature of the kernel image. The image can still be loaded without + a valid signature unless you also enable KEXEC_SIG_FORCE, though if + there's a signature that we can check, then it must be valid. + + In addition to this option, you need to enable signature verification for the corresponding kernel image type being loaded in order for this to work. +config KEXEC_SIG_FORCE + bool "Require a valid signature in kexec_file_load() syscall" + depends on KEXEC_SIG + ---help--- + This option makes kernel signature verification mandatory for + the kexec_file_load() syscall. + config KEXEC_BZIMAGE_VERIFY_SIG bool "Enable bzImage signature verification support" - depends on KEXEC_VERIFY_SIG + depends on KEXEC_SIG depends on SIGNED_PE_FILE_VERIFICATION select SYSTEM_TRUSTED_KEYRING ---help--- diff --git a/crypto/asymmetric_keys/verify_pefile.c b/crypto/asymmetric_keys/verify_pefile.c index 3b303fe2f061..cc9dbcecaaca 100644 --- a/crypto/asymmetric_keys/verify_pefile.c +++ b/crypto/asymmetric_keys/verify_pefile.c @@ -96,7 +96,7 @@ static int pefile_parse_binary(const void *pebuf, unsigned int pelen, if (!ddir->certs.virtual_address || !ddir->certs.size) { pr_debug("Unsigned PE binary\n"); - return -EKEYREJECTED; + return -ENODATA; } chkaddr(ctx->header_size, ddir->certs.virtual_address, @@ -403,6 +403,8 @@ static int pefile_digest_pe(const void *pebuf, unsigned int pelen, * (*) 0 if at least one signature chain intersects with the keys in the trust * keyring, or: * + * (*) -ENODATA if there is no signature present. + * * (*) -ENOPKG if a suitable crypto module couldn't be found for a check on a * chain. * diff --git a/include/linux/kexec.h b/include/linux/kexec.h index 305f6a5ca4fe..998f77c3a0e1 100644 --- a/include/linux/kexec.h +++ b/include/linux/kexec.h @@ -125,7 +125,7 @@ typedef void *(kexec_load_t)(struct kimage *image, char *kernel_buf, unsigned long cmdline_len); typedef int (kexec_cleanup_t)(void *loader_data); -#ifdef CONFIG_KEXEC_VERIFY_SIG +#ifdef CONFIG_KEXEC_SIG typedef int (kexec_verify_sig_t)(const char *kernel_buf, unsigned long kernel_len); #endif @@ -134,7 +134,7 @@ struct kexec_file_ops { kexec_probe_t *probe; kexec_load_t *load; kexec_cleanup_t *cleanup; -#ifdef CONFIG_KEXEC_VERIFY_SIG +#ifdef CONFIG_KEXEC_SIG kexec_verify_sig_t *verify_sig; #endif }; diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c index b8cc032d5620..875482c34154 100644 --- a/kernel/kexec_file.c +++ b/kernel/kexec_file.c @@ -88,7 +88,7 @@ int __weak arch_kimage_file_post_load_cleanup(struct kimage *image) return kexec_image_post_load_cleanup_default(image); } -#ifdef CONFIG_KEXEC_VERIFY_SIG +#ifdef CONFIG_KEXEC_SIG static int kexec_image_verify_sig_default(struct kimage *image, void *buf, unsigned long buf_len) { @@ -186,7 +186,8 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd, const char __user *cmdline_ptr, unsigned long cmdline_len, unsigned flags) { - int ret = 0; + const char *reason; + int ret; void *ldata; loff_t size; @@ -202,14 +203,42 @@ kimage_file_prepare_segments(struct kimage *image, int kernel_fd, int initrd_fd, if (ret) goto out; -#ifdef CONFIG_KEXEC_VERIFY_SIG +#ifdef CONFIG_KEXEC_SIG ret = arch_kexec_kernel_verify_sig(image, image->kernel_buf, image->kernel_buf_len); - if (ret) { - pr_debug("kernel signature verification failed.\n"); + switch (ret) { + case 0: + break; + + /* Certain verification errors are non-fatal if we're not + * checking errors, provided we aren't mandating that there + * must be a valid signature. + */ + case -ENODATA: + reason = "kexec of unsigned image"; + goto decide; + case -ENOPKG: + reason = "kexec of image with unsupported crypto"; + goto decide; + case -ENOKEY: + reason = "kexec of image with unavailable key"; + decide: + if (IS_ENABLED(CONFIG_KEXEC_SIG_FORCE)) { + pr_notice("%s rejected\n", reason); + goto out; + } + + ret = 0; + break; + + /* All other errors are fatal, including nomem, unparseable + * signatures and signature check failures - even if signatures + * aren't required. + */ + default: + pr_notice("kernel signature verification failed (%d).\n", ret); goto out; } - pr_debug("kernel signature verification successful.\n"); #endif /* It is possible that there no initramfs is being loaded */ if (!(flags & KEXEC_FILE_NO_INITRAMFS)) {