From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 35C6ECA0ED3 for ; Mon, 11 Sep 2023 21:16:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243029AbjIKVHt (ORCPT ); Mon, 11 Sep 2023 17:07:49 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37890 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242327AbjIKP1v (ORCPT ); Mon, 11 Sep 2023 11:27:51 -0400 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 03675E4 for ; Mon, 11 Sep 2023 08:27:47 -0700 (PDT) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 217F1C433C8; Mon, 11 Sep 2023 15:27:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1694446066; bh=dxdGTXpkLoQnBg2zEGXBrkWdpMTVIp/F/DQbyHPN6hM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BhyO4+mbH7gUPnIHTS9KvOGLK77r3Y7WbvkJpjn8Kt6ooYH9cHiN0E6mtF/Y7r72x hk8+2uaNDoI5yVXy8SOTuxiWwhchSl/IN+mGBYZ9/V0hTFaHuQH/500kz6EHJACral U1EvOAmqHjLS1qWoZFtCjwuXkEF/2A/0O6hc0X4E= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jarkko Sakkinen , Eric Biggers Subject: [PATCH 6.1 569/600] fsverity: skip PKCS#7 parser when keyring is empty Date: Mon, 11 Sep 2023 15:50:02 +0200 Message-ID: <20230911134650.406257862@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20230911134633.619970489@linuxfoundation.org> References: <20230911134633.619970489@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Eric Biggers commit 919dc320956ea353a7fb2d84265195ad5ef525ac upstream. If an fsverity builtin signature is given for a file but the ".fs-verity" keyring is empty, there's no real reason to run the PKCS#7 parser. Skip this to avoid the PKCS#7 attack surface when builtin signature support is configured into the kernel but is not being used. This is a hardening improvement, not a fix per se, but I've added Fixes and Cc stable to get it out to more users. Fixes: 432434c9f8e1 ("fs-verity: support builtin file signatures") Cc: stable@vger.kernel.org Reviewed-by: Jarkko Sakkinen Link: https://lore.kernel.org/r/20230820173237.2579-1-ebiggers@kernel.org Signed-off-by: Eric Biggers Signed-off-by: Greg Kroah-Hartman --- fs/verity/signature.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) --- a/fs/verity/signature.c +++ b/fs/verity/signature.c @@ -54,6 +54,22 @@ int fsverity_verify_signature(const stru return 0; } + if (fsverity_keyring->keys.nr_leaves_on_tree == 0) { + /* + * The ".fs-verity" keyring is empty, due to builtin signatures + * being supported by the kernel but not actually being used. + * In this case, verify_pkcs7_signature() would always return an + * error, usually ENOKEY. It could also be EBADMSG if the + * PKCS#7 is malformed, but that isn't very important to + * distinguish. So, just skip to ENOKEY to avoid the attack + * surface of the PKCS#7 parser, which would otherwise be + * reachable by any task able to execute FS_IOC_ENABLE_VERITY. + */ + fsverity_err(inode, + "fs-verity keyring is empty, rejecting signed file!"); + return -ENOKEY; + } + d = kzalloc(sizeof(*d) + hash_alg->digest_size, GFP_KERNEL); if (!d) return -ENOMEM;