MD5-CRYPT/CRAM-MD5 vs SHA512-CRYPT/PLAIN

[Jan Wideł]

On 12/06/2014 02:35 AM, Nick Edwards wrote:
> On 12/5/14, ML mail <mlnospam at yahoo.com> wrote:
>> Hello,
>>
>> I am wondering which variant is more secure for user authentication and
>> password scheme. Basically I am looking at both variants:
>>
>> 1) MD5-CRYPT password scheme storage with CRAM-MD5 auth mechanism
>> 2) SHA512-CRYPT password scheme storage with PLAIN auth mechanism
>>
>> In my opinion the option 2) should be safer although it is using PLAIN auth
>> mechanism. Of course I would always use STARTTLS and not allow unencrypted
>> connection.
> 
> Thats not exactly a true statement, if you offer STARTTLS you are
> optional on encryption, if you mean not allow unencrypted connections
> then you are forcing TLS, not STARTTLS since the latter is designed to
> accept unencrypted and then _try_ upgrade to encryption if possible,
> if not, stay unencrypted.

If you add disable_plaintext_auth=yes ssl=required settings, then
dovecot will drop authentication without STARTTLS. But damage will be
done, client will send unencrypted (or in this scenario MD5 or SHA512
hash) login/password.
http://wiki2.dovecot.org/SSL

>> What is your opinion?
>>
> Number 2  as the other poster said without hesitation and for reasons he said
+1


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Jan Wideł
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