[CentOS] login case sensitivity
hw
hw at gc-24.de
Fri Sep 8 11:24:22 UTC 2017
Stephen John Smoogen wrote:
> On 7 September 2017 at 16:07, Alexander Dalloz <ad+lists at uni-x.org> wrote:
>> Am 07.09.2017 um 20:07 schrieb hw:
>>>
>>> Gordon Messmer wrote:
>>>>
>>>> On 09/07/2017 08:11 AM, Stephen John Smoogen wrote:
>>>>>
>>>>> This was always
>>>>> problematic because DNS hostnames and email addresses in the RFC
>>>>> standards were case insensitive
>>>>
>>>>
>>>>
>>>> Not quite. SMTP is required to treat the "local-part" of the RCPT
>>>> argument as case-sensitive, and to preserve case when relaying mail. The
>>>> destination is allowed to treat addresses according to local policy, but in
>>>> general SMTP is case sensitive with regard to the user identifier.
>>>
>>>
>>> Last time I checked, RFCs said that local parts *should not* be case
>>> sensitive,
>>> and cyrus defaulted to treat them case sensitive, which is a default that
>>> usually
>>> needs to be changed because senders of messages tend to not pay any
>>> attention to
>>> the case sensitiveness of recipient addresses at all, which then confuses
>>> them like
>>> any other error.
>>
>>
>> The relevant part from the RFC:
>>
>> https://www.ietf.org/rfc/rfc5321.txt
>>
>> 2.4. General Syntax Principles and Transaction Model
>>
>> Verbs and argument values (e.g., "TO:" or "to:" in the RCPT command
>> and extension name keywords) are not case sensitive, with the sole
>> exception in this specification of a mailbox local-part (SMTP
>> Extensions may explicitly specify case-sensitive elements). That is,
>> a command verb, an argument value other than a mailbox local-part,
>> and free form text MAY be encoded in upper case, lower case, or any
>> mixture of upper and lower case with no impact on its meaning. The
>> local-part of a mailbox MUST BE treated as case sensitive.
>> Therefore, SMTP implementations MUST take care to preserve the case
>> of mailbox local-parts. In particular, for some hosts, the user
>> "smith" is different from the user "Smith". However, exploiting the
>> case sensitivity of mailbox local-parts impedes interoperability and
>> is discouraged. Mailbox domains follow normal DNS rules and are
>> hence not case sensitive.
>> for maximum interoperability, a host that expects to receive mail
SHOULD avoid defining mailboxes where the Local-part requires (or
uses) the Quoted-string form or where the Local-part is case-
sensitive.
>
> Thanks for the clarification to my original email. I misremembered
> RFC821 and thought it was for the entire part..
>
> Commands and replies are not case sensitive. That is, a command or
> reply word may be upper case, lower case, or any mixture of upper and
> lower case. Note that this is not true of mailbox user names. For
> some hosts the user name is case sensitive, and SMTP implementations
> must take case to preserve the case of user names as they appear in
> mailbox arguments. Host names are not case sensitive.
RFC2821, section 4.1.2:
" for maximum interoperability, a host that expects to receive mail
SHOULD avoid defining mailboxes where the Local-part requires (or
uses) the Quoted-string form or where the Local-part is case-
sensitive.
"
It comes down to that case-preservation is demanded from the implementations
of protocols while, pragmatically, local parts are encouraged to be case
insensitive.
More than a decade ago, I argued that the default used by cyrus be changed to
treat local parts case insensitve. About 2 years ago, that still hadn´t
changed.
So everyone deploying cyrus, be aware. Other than that, cyrus always worked
flawlessly, and I highly recommend it to everyone needing an IMAP server.
More information about the CentOS
mailing list