From patchwork Thu Jan 21 15:55:09 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Micka=C3=ABl_Sala=C3=BCn?= X-Patchwork-Id: 12037067 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4C766C433E6 for ; Thu, 21 Jan 2021 16:51:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 04B2223A56 for ; Thu, 21 Jan 2021 16:51:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731953AbhAUQvA (ORCPT ); Thu, 21 Jan 2021 11:51:00 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43522 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731897AbhAUP6I (ORCPT ); Thu, 21 Jan 2021 10:58:08 -0500 Received: from smtp-190e.mail.infomaniak.ch (smtp-190e.mail.infomaniak.ch [IPv6:2001:1600:4:17::190e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DA4FFC0617AB for ; Thu, 21 Jan 2021 07:55:32 -0800 (PST) Received: from smtp-3-0000.mail.infomaniak.ch (unknown [10.4.36.107]) by smtp-3-3000.mail.infomaniak.ch (Postfix) with ESMTPS id 4DM6Rl18rszMpnPf; Thu, 21 Jan 2021 16:55:31 +0100 (CET) Received: from localhost (unknown [23.97.221.149]) by smtp-3-0000.mail.infomaniak.ch (Postfix) with ESMTPA id 4DM6Rk5yXDzlh8TW; Thu, 21 Jan 2021 16:55:30 +0100 (CET) From: =?utf-8?q?Micka=C3=ABl_Sala=C3=BCn?= To: David Howells , David Woodhouse , Jarkko Sakkinen Cc: =?utf-8?q?Micka=C3=ABl_Sala=C3=BCn?= , "David S . Miller" , Herbert Xu , James Morris , =?utf-8?q?Micka=C3=ABl_Sala=C3=BCn?= , Mimi Zohar , "Serge E . Hallyn" , Tyler Hicks , keyrings@vger.kernel.org, linux-crypto@vger.kernel.org, linux-integrity@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org Subject: [PATCH v4 06/10] certs: Make blacklist_vet_description() more strict Date: Thu, 21 Jan 2021 16:55:09 +0100 Message-Id: <20210121155513.539519-7-mic@digikod.net> X-Mailer: git-send-email 2.30.0 In-Reply-To: <20210121155513.539519-1-mic@digikod.net> References: <20210121155513.539519-1-mic@digikod.net> MIME-Version: 1.0 Precedence: bulk List-ID: From: Mickaël Salaün Before exposing this new key type to user space, make sure that only meaningful blacklisted hashes are accepted. This is also checked for builtin blacklisted hashes, but a following commit make sure that the user will notice (at built time) and will fix the configuration if it already included errors. Check that a blacklist key description starts with a valid prefix and then a valid hexadecimal string. Cc: David Howells Cc: David Woodhouse Signed-off-by: Mickaël Salaün Acked-by: Jarkko Sakkinen --- Changes since v2: * Fix typo in blacklist_vet_description() comment, spotted by Tyler Hicks. * Add Jarkko's Acked-by. Changes since v1: * Return ENOPKG (instead of EINVAL) when a hash is greater than the maximum currently known hash (suggested by David Howells). --- certs/blacklist.c | 46 ++++++++++++++++++++++++++++++++++++---------- 1 file changed, 36 insertions(+), 10 deletions(-) diff --git a/certs/blacklist.c b/certs/blacklist.c index 8a64b9e89cae..069050884bd2 100644 --- a/certs/blacklist.c +++ b/certs/blacklist.c @@ -18,6 +18,16 @@ #include #include "blacklist.h" +/* + * According to crypto/asymmetric_keys/x509_cert_parser.c:x509_note_pkey_algo(), + * the size of the currently longest supported hash algorithm is 512 bits, + * which translates into 128 hex characters. + */ +#define MAX_HASH_LEN 128 + +static const char tbs_prefix[] = "tbs"; +static const char bin_prefix[] = "bin"; + static struct key *blacklist_keyring; /* @@ -26,24 +36,40 @@ static struct key *blacklist_keyring; */ static int blacklist_vet_description(const char *desc) { - int n = 0; - - if (*desc == ':') - return -EINVAL; - for (; *desc; desc++) - if (*desc == ':') - goto found_colon; + int i, prefix_len, tbs_step = 0, bin_step = 0; + + /* The following algorithm only works if prefix lengths match. */ + BUILD_BUG_ON(sizeof(tbs_prefix) != sizeof(bin_prefix)); + prefix_len = sizeof(tbs_prefix) - 1; + for (i = 0; *desc; desc++, i++) { + if (*desc == ':') { + if (tbs_step == prefix_len) + goto found_colon; + if (bin_step == prefix_len) + goto found_colon; + return -EINVAL; + } + if (i >= prefix_len) + return -EINVAL; + if (*desc == tbs_prefix[i]) + tbs_step++; + if (*desc == bin_prefix[i]) + bin_step++; + } return -EINVAL; found_colon: desc++; - for (; *desc; desc++) { + for (i = 0; *desc && i < MAX_HASH_LEN; desc++, i++) { if (!isxdigit(*desc) || isupper(*desc)) return -EINVAL; - n++; } + if (*desc) + /* The hash is greater than MAX_HASH_LEN. */ + return -ENOPKG; - if (n == 0 || n & 1) + /* Checks for an even number of hexadecimal characters. */ + if (i == 0 || i & 1) return -EINVAL; return 0; }