Received-SPF: pass (google.com: domain of linux-crypto-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Reply-To: crecklin@redhat.com
Subject: Re: [PATCH v4 1/1] use crc32 instead of md5 for hibernation e820
 integrity check
To:     David Laight <David.Laight@ACULAB.COM>,
        "ardb@kernel.org" <ardb@kernel.org>,
        "simo@redhat.com" <simo@redhat.com>,
        "rafael@kernel.org" <rafael@kernel.org>,
        "decui@microsoft.com" <decui@microsoft.com>,
        "linux-pm@vger.kernel.org" <linux-pm@vger.kernel.org>,
        "linux-crypto@vger.kernel.org" <linux-crypto@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
References: <20210408104629.31357-1-crecklin@redhat.com>
 <6be63531313d46caa7161697bf240dfc@AcuMS.aculab.com>
From:   Chris von Recklinghausen <crecklin@redhat.com>
Organization: Red Hat
Message-ID: <822eaebf-4ef9-d469-4238-54107c8ba6a6@redhat.com>
Date:   Fri, 9 Apr 2021 15:28:15 -0400
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101
 Thunderbird/78.8.0
MIME-Version: 1.0
In-Reply-To: <6be63531313d46caa7161697bf240dfc@AcuMS.aculab.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit
Content-Language: en-US
Precedence: bulk

On 4/9/21 12:56 PM, David Laight wrote:
> From: Chris von Recklinghausen
>> Sent: 08 April 2021 11:46
>>
>> Suspend fails on a system in fips mode because md5 is used for the e820
>> integrity check and is not available. Use crc32 instead.
>>
>> Prior to this patch, MD5 is used only to create a digest to ensure integrity of
>> the region, no actual encryption is done. This patch set changes the integrity
>> check to use crc32 instead of md5 since crc32 is available in both FIPS and
>> non-FIPS modes.
>>
>> Note that the digest is only used as an integrity check. No actual encryption
>> is done.
> If crc32 is good enough, would a 1's compliment sum be good enough?
> It is likely to be faster to calculate and not need special
> functions be built into the kernel at all.


Eric Biggers <ebiggers@kernel.org> suggested using crc32_le() which is 
in the library interface (lib/crc32.c) and will always be available 
without any special ifdefs. That's what my next version will be based on.

Thanks,

Chris


>
> 	David
>
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)
>