From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9B9676FB5 for ; Sun, 17 Sep 2023 20:33:06 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D02C8C433C7; Sun, 17 Sep 2023 20:33:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1694982786; bh=xiFftyu+Oc18rpCNVTWNd49TTDCIAON+ByVjudvIB5g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ULgF8M+VRJMOOLGgzW9jtEY/GJtHffViZ7G6ZvlURwn81rmcmtJJilTdhslQst7ol KAt4fvcXEGqSPpDGfJ7kl1K5hta36hvtRfpDt0GgOpE7Y0EB8OtZcF1uc1Jw+jATB3 wz0572tsB+t2Lvz+Oa24PInqobNWWOowBB/c+TWs= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jarkko Sakkinen , Eric Biggers Subject: [PATCH 5.15 353/511] fsverity: skip PKCS#7 parser when keyring is empty Date: Sun, 17 Sep 2023 21:13:00 +0200 Message-ID: <20230917191122.328146125@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20230917191113.831992765@linuxfoundation.org> References: <20230917191113.831992765@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-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;