linux-kernel - Re: [PATCH v10 01/12] MODSIGN: Export module signature definitions

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <875zpu766k.fsf@morokweng.localdomain>
Date:   Tue, 28 May 2019 16:03:15 -0300
From:   Thiago Jung Bauermann <bauerman@...ux.ibm.com>
To:     Mimi Zohar <zohar@...ux.ibm.com>
Cc:     linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org, keyrings@...r.kernel.org,
        linux-crypto@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        David Howells <dhowells@...hat.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Jessica Yu <jeyu@...nel.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Jonathan Corbet <corbet@....net>,
        "AKASHI\, Takahiro" <takahiro.akashi@...aro.org>
Subject: Re: [PATCH v10 01/12] MODSIGN: Export module signature definitions


Mimi Zohar <zohar@...ux.ibm.com> writes:

> On Thu, 2019-04-18 at 00:51 -0300, Thiago Jung Bauermann wrote:
>> IMA will use the module_signature format for append signatures, so export
>> the relevant definitions and factor out the code which verifies that the
>> appended signature trailer is valid.
>> 
>> Also, create a CONFIG_MODULE_SIG_FORMAT option so that IMA can select it
>> and be able to use mod_check_sig() without having to depend on either
>> CONFIG_MODULE_SIG or CONFIG_MODULES.
>> 
>> Signed-off-by: Thiago Jung Bauermann <bauerman@...ux.ibm.com>
>> Cc: Jessica Yu <jeyu@...nel.org>
>
> Just a couple minor questions/comments below.
>
> Reviewed-by: Mimi Zohar <zohar@...ux.ibm.com>

Thanks for your review and your comments!

>> diff --git a/init/Kconfig b/init/Kconfig
>> index 4592bf7997c0..a71019553ee1 100644
>> --- a/init/Kconfig
>> +++ b/init/Kconfig
>> @@ -1906,7 +1906,7 @@ config MODULE_SRCVERSION_ALL
>>  config MODULE_SIG
>>  	bool "Module signature verification"
>>  	depends on MODULES
>> -	select SYSTEM_DATA_VERIFICATION
>> +	select MODULE_SIG_FORMAT
>>  	help
>>  	  Check modules for valid signatures upon load: the signature
>>  	  is simply appended to the module. For more information see
>> @@ -2036,6 +2036,10 @@ config TRIM_UNUSED_KSYMS
>>  
>>  endif # MODULES
>>  
>> +config MODULE_SIG_FORMAT
>> +	def_bool n
>> +	select SYSTEM_DATA_VERIFICATION
>
> Normally Kconfigs, in the same file, are defined before they are used.
>  I'm not sure if that is required or just a convention.

I think it's a convention, because it seemed to work in the current way.
For the next version I moved the config MODULE_SIG_FORMAT definition to
just before "menuconfig MODULES"

>> diff --git a/kernel/module_signature.c b/kernel/module_signature.c
>> new file mode 100644
>> index 000000000000..6d5e59f27f55
>> --- /dev/null
>> +++ b/kernel/module_signature.c
>> @@ -0,0 +1,45 @@
>> +// SPDX-License-Identifier: GPL-2.0+
>> +/*
>> + * Module signature checker
>> + *
>> + * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
>> + * Written by David Howells (dhowells@...hat.com)
>> + */
>> +
>> +#include <linux/errno.h>
>> +#include <linux/printk.h>
>> +#include <linux/module_signature.h>
>> +#include <asm/byteorder.h>
>> +
>> +/**
>> + * mod_check_sig - check that the given signature is sane
>> + *
>> + * @ms:		Signature to check.
>> + * @file_len:	Size of the file to which @ms is appended.
>
> "name" is missing.

Fixed.

-- 
Thiago Jung Bauermann
IBM Linux Technology Center