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 X-Spam-Level: X-Spam-Status: No, score=-17.6 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_IN_DEF_DKIM_WL autolearn=ham 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 0EB36C433E3 for ; Thu, 6 Aug 2020 17:08:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3ACF923119 for ; Thu, 6 Aug 2020 17:08:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=linux.microsoft.com header.i=@linux.microsoft.com header.b="aXAMg6wc" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729587AbgHFRIW (ORCPT ); Thu, 6 Aug 2020 13:08:22 -0400 Received: from linux.microsoft.com ([13.77.154.182]:56788 "EHLO linux.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729357AbgHFRGf (ORCPT ); Thu, 6 Aug 2020 13:06:35 -0400 Received: from sequoia (162-237-133-238.lightspeed.rcsntx.sbcglobal.net [162.237.133.238]) by linux.microsoft.com (Postfix) with ESMTPSA id 05EBF20B4908; Thu, 6 Aug 2020 08:46:37 -0700 (PDT) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com 05EBF20B4908 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1596728798; bh=KG2C6RbvLQBgLP+0NWNVA/7hHclgHh703Y6EXT9pNkY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=aXAMg6wcqdwOoZdGIULELD41c4SAJhF4XYK8WNDNhmldx9W/PmQVnJb83CT/mqp4d ZDHRVzKvbhts3VJKMjZBX1Psyz0BOoN18dI37/BVFR2LwW3pQHbIZ6M7Z/hrydcRF4 OtV0jXI+OHmzpKsa8SVpRidB/XRbUFc2MJ9rhfhg= Date: Thu, 6 Aug 2020 10:46:36 -0500 From: Tyler Hicks To: Nayna Cc: Mimi Zohar , Dmitry Kasatkin , James Morris , "Serge E . Hallyn" , Lakshmi Ramasubramanian , Tushar Sugandhi , Nayna Jain , linux-kernel@vger.kernel.org, linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org Subject: Re: [PATCH 1/2] ima: Pre-parse the list of keyrings in a KEY_CHECK rule Message-ID: <20200806154636.GB55159@sequoia> References: <20200727140831.64251-1-tyhicks@linux.microsoft.com> <20200727140831.64251-2-tyhicks@linux.microsoft.com> <8f749594-1214-9f2d-4614-d360772a2ab6@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <8f749594-1214-9f2d-4614-d360772a2ab6@linux.vnet.ibm.com> Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: On 2020-08-06 11:34:43, Nayna wrote: > > On 7/27/20 10:08 AM, Tyler Hicks wrote: > > The ima_keyrings buffer was used as a work buffer for strsep()-based > > parsing of the "keyrings=" option of an IMA policy rule. This parsing > > was re-performed each time an asymmetric key was added to a kernel > > keyring for each loaded policy rule that contained a "keyrings=" option. > > > > An example rule specifying this option is: > > > > measure func=KEY_CHECK keyrings=a|b|c > > > > The rule says to measure asymmetric keys added to any of the kernel > > keyrings named "a", "b", or "c". The size of the buffer size was > > equal to the size of the largest "keyrings=" value seen in a previously > > loaded rule (5 + 1 for the NUL-terminator in the previous example) and > > the buffer was pre-allocated at the time of policy load. > > > > The pre-allocated buffer approach suffered from a couple bugs: > > > > 1) There was no locking around the use of the buffer so concurrent key > > add operations, to two different keyrings, would result in the > > strsep() loop of ima_match_keyring() to modify the buffer at the same > > time. This resulted in unexpected results from ima_match_keyring() > > and, therefore, could cause unintended keys to be measured or keys to > > not be measured when IMA policy intended for them to be measured. > > > > 2) If the kstrdup() that initialized entry->keyrings in ima_parse_rule() > > failed, the ima_keyrings buffer was freed and set to NULL even when a > > valid KEY_CHECK rule was previously loaded. The next KEY_CHECK event > > would trigger a call to strcpy() with a NULL destination pointer and > > crash the kernel. > > > > Remove the need for a pre-allocated global buffer by parsing the list of > > keyrings in a KEY_CHECK rule at the time of policy load. The > > ima_rule_entry will contain an array of string pointers which point to > > the name of each keyring specified in the rule. No string processing > > needs to happen at the time of asymmetric key add so iterating through > > the list and doing a string comparison is all that's required at the > > time of policy check. > > > > In the process of changing how the "keyrings=" policy option is handled, > > a couple additional bugs were fixed: > > > > 1) The rule parser accepted rules containing invalid "keyrings=" values > > such as "a|b||c", "a|b|", or simply "|". > > > > 2) The /sys/kernel/security/ima/policy file did not display the entire > > "keyrings=" value if the list of keyrings was longer than what could > > fit in the fixed size tbuf buffer in ima_policy_show(). > > > > Fixes: 5c7bac9fb2c5 ("IMA: pre-allocate buffer to hold keyrings string") > > Fixes: 2b60c0ecedf8 ("IMA: Read keyrings= option from the IMA policy") > > Signed-off-by: Tyler Hicks > > --- > > security/integrity/ima/ima_policy.c | 138 +++++++++++++++++++--------- > > 1 file changed, 93 insertions(+), 45 deletions(-) > > > > diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c > > index 07f033634b27..c328cfa0fc49 100644 > > --- a/security/integrity/ima/ima_policy.c > > +++ b/security/integrity/ima/ima_policy.c > > @@ -59,6 +59,11 @@ enum policy_types { ORIGINAL_TCB = 1, DEFAULT_TCB }; > > enum policy_rule_list { IMA_DEFAULT_POLICY = 1, IMA_CUSTOM_POLICY }; > > +struct ima_rule_opt_list { > > + size_t count; > > + char *items[]; > > +}; > > + > > struct ima_rule_entry { > > struct list_head list; > > int action; > > @@ -78,7 +83,7 @@ struct ima_rule_entry { > > int type; /* audit type */ > > } lsm[MAX_LSM_RULES]; > > char *fsname; > > - char *keyrings; /* Measure keys added to these keyrings */ > > + struct ima_rule_opt_list *keyrings; /* Measure keys added to these keyrings */ > > struct ima_template_desc *template; > > }; > > @@ -206,10 +211,6 @@ static LIST_HEAD(ima_policy_rules); > > static LIST_HEAD(ima_temp_rules); > > static struct list_head *ima_rules = &ima_default_rules; > > -/* Pre-allocated buffer used for matching keyrings. */ > > -static char *ima_keyrings; > > -static size_t ima_keyrings_len; > > - > > static int ima_policy __initdata; > > static int __init default_measure_policy_setup(char *str) > > @@ -253,6 +254,72 @@ static int __init default_appraise_policy_setup(char *str) > > } > > __setup("ima_appraise_tcb", default_appraise_policy_setup); > > +static struct ima_rule_opt_list *ima_alloc_rule_opt_list(const substring_t *src) > > +{ > > + struct ima_rule_opt_list *opt_list; > > + size_t count = 0; > > + char *src_copy; > > + char *cur, *next; > > + size_t i; > > + > > + src_copy = match_strdup(src); > > + if (!src_copy) > > + return NULL; > > The caller of this function checks for IS_ERR(..) and not > IS_ERR_OR_NULL(..). Shouldn't it return ERR_PTR(-EINVAL) instead of NULL ? Yes! Thank you for catching this. I switched this function to returning an ERR_PTR() towards the end of my development for this series and missed this particular return. I'll send out a v2 ASAP. Tyler > > Thanks & Regards, > >     - Nayna