From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [PATCH] ima: drop vla in ima_audit_measurement() From: Mimi Zohar Date: Thu, 08 Mar 2018 14:20:17 -0500 In-Reply-To: <20180308190431.5fstqsjmbpquzqii@smitten> References: <20180308171456.2597-1-tycho@tycho.ws> <20180308183721.mnsrmhekyfo2dbso@smitten> <1520535030.3605.64.camel@linux.vnet.ibm.com> <20180308190431.5fstqsjmbpquzqii@smitten> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Message-Id: <1520536817.3605.74.camel@linux.vnet.ibm.com> To: Tycho Andersen Cc: Andy Shevchenko , Dmitry Kasatkin , linux-integrity@vger.kernel.org, Linux Kernel Mailing List , kernel-hardening@lists.openwall.com, Richard Guy Briggs List-ID: On Thu, 2018-03-08 at 12:04 -0700, Tycho Andersen wrote: > On Thu, Mar 08, 2018 at 01:50:30PM -0500, Mimi Zohar wrote: > > On Thu, 2018-03-08 at 11:37 -0700, Tycho Andersen wrote: > > > On Thu, Mar 08, 2018 at 07:47:37PM +0200, Andy Shevchenko wrote: > > > > On Thu, Mar 8, 2018 at 7:14 PM, Tycho Andersen wrote: > > > > > In keeping with the directive to get rid of VLAs [1], let's drop the VLA > > > > > from ima_audit_measurement(). We need to adjust the return type of > > > > > ima_audit_measurement, because now this function can fail if an allocation > > > > > fails. > > > > > > > > > > > > > > > > > + algo_hash_len = hash_len + strlen(algo_name) + 2; > > > > > + algo_hash = kzalloc(algo_hash_len, GFP_KERNEL); > > > > > > > > > - snprintf(algo_hash, sizeof(algo_hash), "%s:%s", algo_name, hash); > > > > > + snprintf(algo_hash, algo_hash_len, "%s:%s", algo_name, hash); > > > > > > > > kasprintf() ? > > > > > > Sure, in fact I think we could just do: > > > > > > - snprintf(algo_hash, algo_hash_len, "%s:%s", algo_name, hash); > > > - audit_log_untrustedstring(ab, algo_hash); > > > + audit_log_untrustedstring(ab, algo_name); > > > + audit_log_format(ab, ":"); > > > + audit_log_untrustedstring(ab, hash); > > > > > > and get rid of the allocation entirely. I'll test and make sure it > > > works and then re-send. > > > > The hash algorithm name is an enumeration that comes from the kernel. > >  It's defined in crypto/hash_info.c: hash_algo_name.  Why do we need > > to use audit_log_untrustedstring()? > > Yes, I suppose we don't need it for the hash either, since we're > generating that and we know it's just hex digits and not any audit > control characters or "s or anything. > > It looks like we could get rid of the other allocation too by just > using audit_log_n_hex, but that uses hex_byte_pack_upper, vs. the > hex_byte_pack that's currently in use in this function. Is that too > much of a breakage? Based on the discussion with Richard Briggs, we need to differentiate between the ima_audit_measurement() and the ima_parse_rule() usage of AUDIT_INTEGRITY_RULE.  The ima_parse_rule() will continue to use AUDIT_INTEGRITY_RULE.  ima_audit_measurement() will need to define and use a new number.  Auidt name suggestions would be appreciated. When we make that sort of change, any other changes are insignificant. How different are the two formats? Mimi From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:43178 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1754547AbeCHTUY (ORCPT ); Thu, 8 Mar 2018 14:20:24 -0500 Received: from pps.filterd (m0098421.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w28JIc3U083789 for ; Thu, 8 Mar 2018 14:20:24 -0500 Received: from e06smtp11.uk.ibm.com (e06smtp11.uk.ibm.com [195.75.94.107]) by mx0a-001b2d01.pphosted.com with ESMTP id 2gk98s4ur0-1 (version=TLSv1.2 cipher=AES256-SHA256 bits=256 verify=NOT) for ; Thu, 08 Mar 2018 14:20:23 -0500 Received: from localhost by e06smtp11.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 8 Mar 2018 19:20:22 -0000 Subject: Re: [PATCH] ima: drop vla in ima_audit_measurement() From: Mimi Zohar To: Tycho Andersen Cc: Andy Shevchenko , Dmitry Kasatkin , linux-integrity@vger.kernel.org, Linux Kernel Mailing List , kernel-hardening@lists.openwall.com, Richard Guy Briggs Date: Thu, 08 Mar 2018 14:20:17 -0500 In-Reply-To: <20180308190431.5fstqsjmbpquzqii@smitten> References: <20180308171456.2597-1-tycho@tycho.ws> <20180308183721.mnsrmhekyfo2dbso@smitten> <1520535030.3605.64.camel@linux.vnet.ibm.com> <20180308190431.5fstqsjmbpquzqii@smitten> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Message-Id: <1520536817.3605.74.camel@linux.vnet.ibm.com> Sender: linux-integrity-owner@vger.kernel.org List-ID: On Thu, 2018-03-08 at 12:04 -0700, Tycho Andersen wrote: > On Thu, Mar 08, 2018 at 01:50:30PM -0500, Mimi Zohar wrote: > > On Thu, 2018-03-08 at 11:37 -0700, Tycho Andersen wrote: > > > On Thu, Mar 08, 2018 at 07:47:37PM +0200, Andy Shevchenko wrote: > > > > On Thu, Mar 8, 2018 at 7:14 PM, Tycho Andersen wrote: > > > > > In keeping with the directive to get rid of VLAs [1], let's drop the VLA > > > > > from ima_audit_measurement(). We need to adjust the return type of > > > > > ima_audit_measurement, because now this function can fail if an allocation > > > > > fails. > > > > > > > > > > > > > > > > > + algo_hash_len = hash_len + strlen(algo_name) + 2; > > > > > + algo_hash = kzalloc(algo_hash_len, GFP_KERNEL); > > > > > > > > > - snprintf(algo_hash, sizeof(algo_hash), "%s:%s", algo_name, hash); > > > > > + snprintf(algo_hash, algo_hash_len, "%s:%s", algo_name, hash); > > > > > > > > kasprintf() ? > > > > > > Sure, in fact I think we could just do: > > > > > > - snprintf(algo_hash, algo_hash_len, "%s:%s", algo_name, hash); > > > - audit_log_untrustedstring(ab, algo_hash); > > > + audit_log_untrustedstring(ab, algo_name); > > > + audit_log_format(ab, ":"); > > > + audit_log_untrustedstring(ab, hash); > > > > > > and get rid of the allocation entirely. I'll test and make sure it > > > works and then re-send. > > > > The hash algorithm name is an enumeration that comes from the kernel. > > It's defined in crypto/hash_info.c: hash_algo_name. Why do we need > > to use audit_log_untrustedstring()? > > Yes, I suppose we don't need it for the hash either, since we're > generating that and we know it's just hex digits and not any audit > control characters or "s or anything. > > It looks like we could get rid of the other allocation too by just > using audit_log_n_hex, but that uses hex_byte_pack_upper, vs. the > hex_byte_pack that's currently in use in this function. Is that too > much of a breakage? Based on the discussion with Richard Briggs, we need to differentiate between the ima_audit_measurement() and the ima_parse_rule() usage of AUDIT_INTEGRITY_RULE. The ima_parse_rule() will continue to use AUDIT_INTEGRITY_RULE. ima_audit_measurement() will need to define and use a new number. Auidt name suggestions would be appreciated. When we make that sort of change, any other changes are insignificant. How different are the two formats? Mimi