Received: by 2002:a25:4158:0:0:0:0:0 with SMTP id o85csp683827yba; Wed, 3 Apr 2019 17:34:21 -0700 (PDT) X-Google-Smtp-Source: APXvYqwva44Q1s9xXqmhi5ojuAzyhGO0LaE5l/EuSp1JTftQoSKvHgmgSbc4Ih65S152j3Bg38CG X-Received: by 2002:a17:902:d701:: with SMTP id w1mr3235062ply.124.1554338061599; Wed, 03 Apr 2019 17:34:21 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1554338061; cv=none; d=google.com; s=arc-20160816; b=fndwMSr5Q2EiSv7Axb/OxpYfiu53T/OsMGLwHwRmPuGQZGvRYnf05vSEfEeE5/kQHi It9Pzmw9WPI27OnNMajlbYMSr1S6/fG5xs7GSQMM0DhxgoKsR8Lr9cvfbNuQp4YQV/V5 18bTupNFu1HG0HQS3oJlzPUIIIBnDKhG0uhU8CFqwK5tcsNP+C4EMhF/DMxlu6bT3iz/ ots/AERjMw6vkrdQhyhDDFEkMxOR5ic6F2nF8WXzb9ag6yYRHRVbCYnLLk9T8jFs0GPA C6FhDxURTmHwyCM8ye90RW5M1VK1bBENB/VMLbQdb/LGEQu1AXYoIkdTrT9uXgTXyBhG 3LCg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:cc:to:from:subject:references :mime-version:message-id:in-reply-to:date:dkim-signature; bh=DR3rBb2V8Dk77n+84nIF0+Znm0UqE9/8zaxdQ5CO2lo=; b=y2kr9iLy8qWBNXnSDgR0R7cskcIfkwKsq4nZ6j87klY0Y6vEMGOIFEKwEofZSXV6RW x3kkfBjKaJYDYL06KIor4M0C6b8zNDr6HegNWoCuW2f5dtziKkPcHIgzPuRVMAym6j5x Tunxs7uerQaYNFW16EbWSo2KLt+1q+8v3IfiDh+aNAfLIgf4JCx2mjrlGaMzOM79Mv7B eRKwxJdnIEJoi5pPJ9YmiL3MYa+gOlYLpYUMGb0ZGbwhCQwFE0Nc0uGWTy5B8y9cifHG fyZxERnohVstDSlv5pMA+Yg/ffoPAfsT+lWPDG9aQd4DBbNMRRsdy4VUt1IOH4faLGu3 NhOA== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=k4T3Nw21; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id g75si15432741pfg.49.2019.04.03.17.34.06; Wed, 03 Apr 2019 17:34:21 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b=k4T3Nw21; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726761AbfDDAdN (ORCPT + 99 others); Wed, 3 Apr 2019 20:33:13 -0400 Received: from mail-vk1-f202.google.com ([209.85.221.202]:56398 "EHLO mail-vk1-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726671AbfDDAdK (ORCPT ); Wed, 3 Apr 2019 20:33:10 -0400 Received: by mail-vk1-f202.google.com with SMTP id m191so419389vka.23 for ; Wed, 03 Apr 2019 17:33:09 -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=DR3rBb2V8Dk77n+84nIF0+Znm0UqE9/8zaxdQ5CO2lo=; b=k4T3Nw21xOXEgT1+4ojRalZBG6PaMDr5iMtJUJF/zPD0JeOPZGN0RJlZ/WcxfZFEsI Q8CKYtYL2CinpCjBUEDha9kChTKJ6x12LBYqnfcvSa+IJuqhCoVYbd5TuQUcVH0SYqLN 8d1y72QUjsqto7fh2VHYanFOVji/MJkU4oLDvxHEkLXLcP6lhABR7dmt0lolrPlwnUSW tHB90LzrAFIiQ6VDnWVTW37yUCFvbnZv8PQ/zs6mi6I8QrKHAntN8c0lxFS8U5VRtBuu DfBYW+xcFZabEWqel4gNb2GrP8CFheQ3zDUCbnK1j4t/R5+n1lMm6NnAjdAMbmL/lzif W+HA== 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=DR3rBb2V8Dk77n+84nIF0+Znm0UqE9/8zaxdQ5CO2lo=; b=V0GkbamTxK1LzuEu6uzsPtWKWmPFFcsZ9rbW+Clw9FLX6XBwpTJCzPEdqK8NglRSMr iPqnSZB+HyYLcFCyOOA1zd3J2UyR/eF0Vwk7T5qV6dFf9KF8vog7wwzZdGp7iQRCKYSr VNone3jmO1tOkP26+jbLhZSNDcg3QGyzmz58TGhoeJQMqUeDps/uCf2GrBhFtwQiuO5t jhG8xXCpiFti13je6FOs75i5GchKBtrTsqDXiOMOQWiKzzJDHqkyerkJBIUuclk7hiF5 zdXcOhVNhptpANpQuYIp/2qwiQthUQui3Qt6DOpybf9dFkuuPFGMdYnLnrvntIGu45rx 6mvg== X-Gm-Message-State: APjAAAWqj7hjOR/8bYhVf/aeScmAIXr3jV/Lx01IXADVfyIWZQWAbDWJ 8Rs62Zm8V8EempX0Kzbgt+96QiySH494Cue77Dzpew== X-Received: by 2002:a1f:9d44:: with SMTP id g65mr372059vke.10.1554337989385; Wed, 03 Apr 2019 17:33:09 -0700 (PDT) Date: Wed, 3 Apr 2019 17:32:28 -0700 In-Reply-To: <20190404003249.14356-1-matthewgarrett@google.com> Message-Id: <20190404003249.14356-7-matthewgarrett@google.com> Mime-Version: 1.0 References: <20190404003249.14356-1-matthewgarrett@google.com> X-Mailer: git-send-email 2.21.0.392.gf8f6787159e-goog Subject: [PATCH V32 06/27] 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, dhowells@redhat.com, linux-api@vger.kernel.org, luto@kernel.org, Jiri Bohac , Matthew Garrett , kexec@lists.infradead.org Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. [Modified by David Howells such that: (1) verify_pefile_signature() differentiates between no-signature and sig-didn't-match in its returned errors. (2) kexec fails with EKEYREJECTED and logs an appropriate message if signature checking is enforced and an signature is not found, uses unsupported crypto or has no matching key. (3) kexec fails with EKEYREJECTED if there is a signature for which we have a key, but signature doesn't match - even if in non-forcing mode. (4) kexec fails with EBADMSG or some other error if there is a signature which cannot be parsed - even if in non-forcing mode. (5) kexec fails with ELIBBAD if the PE file cannot be parsed to extract the signature - even if in non-forcing mode. ] Signed-off-by: Jiri Bohac Signed-off-by: David Howells Signed-off-by: Matthew Garrett Reviewed-by: Jiri Bohac 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 | 48 ++++++++++++++++++++++---- 4 files changed, 61 insertions(+), 15 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 4b4a7f32b68e..735d04a4b18f 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2016,20 +2016,30 @@ 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 d178650fd524..4473cea1e877 100644 --- a/crypto/asymmetric_keys/verify_pefile.c +++ b/crypto/asymmetric_keys/verify_pefile.c @@ -100,7 +100,7 @@ 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, @@ -408,6 +408,8 @@ 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 b9b1bc5f9669..58b27c7bdc2b 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 f1d0e00a3971..67f3a866eabe 100644 --- a/kernel/kexec_file.c +++ b/kernel/kexec_file.c @@ -90,7 +90,7 @@ 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) { @@ -188,7 +188,8 @@ 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; @@ -207,15 +208,48 @@ 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"); +#else + ret = -ENODATA; +#endif + + 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); + ret = -EKEYREJECTED; + 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)) { ret = kernel_read_file_from_fd(initrd_fd, &image->initrd_buf, -- 2.21.0.392.gf8f6787159e-goog