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Subject: Re: [PATCH 0/2] crypto: remove MD4 generic shash
To:     Steve French <smfrench@gmail.com>
Cc:     Ard Biesheuvel <ardb@kernel.org>,
        Linux Crypto Mailing List <linux-crypto@vger.kernel.org>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Eric Biggers <ebiggers@kernel.org>,
        ronnie sahlberg <ronniesahlberg@gmail.com>,
        linux-cifs <linux-cifs@vger.kernel.org>,
        Steve French <sfrench@samba.org>,
        David Howells <dhowells@redhat.com>, keyrings@vger.kernel.org
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From:   Denis Kenzior <denkenz@gmail.com>
Message-ID: <a2934f93-e4cf-4cd1-c9c4-fa68dbae9277@gmail.com>
Date:   Thu, 19 Aug 2021 11:56:20 -0500
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Hi Steve,

>> But the answer is yes.  Both PEAP and TTLS use MSCHAP or MSCHAPv2 in some form.
>>    These are commonly used for Username/Password based WPA(2|3)-Enterprise
>> authentication.  Think 'eduroam' for example.
> 
> Can you give some background here?  IIRC MS-CHAPv2 is much worse than
> the NTLMSSP case

What background are you looking for?  iwd [0] is a wifi management daemon, so we 
implement various EAP [1] and wifi authentication protocols.

> in cifs.ko (where RC4/MD5 is used narrowly).   Doesn't MS-CHAPv2 depend on DES?
> 

You are quite correct.  MSCHAPv2 also uses DES for generating the responses. 
EAP with TTLS+MSCHAPv2 and PEAP+MSCHAPv2 are two of the most deployed variants 
of WPA-Enterprise authentication using Username + Password.

Deprecating MD4, MD5, SHA1 or DES would be quite disruptive for us.  We are 
using these through AF_ALG userspace API, so if they're removed, some 
combination of kernel + iwd version will break.  We went through this with ARC4, 
and while that was justified, I don't think the same justification exists for MD4.

[0] https://git.kernel.org/pub/scm/network/wireless/iwd.git
[1] https://en.wikipedia.org/wiki/Extensible_Authentication_Protocol

Regards,
-Denis