Re: Is KPOP used anywhere?

Hi Дилян,

That's an interesting find.  Looks like the KPOP support was added by this commit (in 1994!):
https://github.com/cyrusimap/cyrus-imapd/commit/3d4ec8f97dc8ea841add759070cd3391bdd79615

That commit contains comments like, "MIT's kpop authentication kludge", "MIT's kludge of a kpop protocol"...

It's not much to go on, but from those comments I'm inferring that it was added to Cyrus for compatibility with whatever MIT were using.  Perhaps MIT had a custom client/server, and having this feature in pop3d would allow users of the MIT client to also talk to Cyrus/CMU servers.

I'd never heard of it until today, so I don't have any more insight than this.

Cheers,

ellie

On Wed, 8 May 2024, at 4:50 AM, Дилян Палаузов wrote:
> Hello,
> 
> is somebody using MIT’s Kerberized Post Office Protocol offered by
> Cyrus IMAP (cmd="pop3d -k")?  This thing runs on a different port than
> POP3.  I cannot find in internet description of the protocol, or MUAs
> which support it.
> 
> This is the text I found in Internet for KPOP:
> 
> According to https://en.wikipedia.org/wiki/Post_Office_Protocol this is
> “In computing, local e-mail clients can use the Kerberized Post Office
> Protocol (KPOP), an application-layer Internet standard protocol, to
> retrieve e-mail from a remote server over a TCP/IP connection. The KPOP
> protocol is based on the POP3 protocol – differing in that it adds
> Kerberos security and that it runs by default over TCP port number 1109
> instead of 110. One mail server software implementation is found in the
> Cyrus
> IMAP server. ”
> 
> https://www.emailondeck.com/b/The-Development-and-Evolution-of-Post-Office-Protocol-POP-in-Email
> says for KPOP
> 
> The Kerberized Post Office Protocol (KPOP) is a modification of the
> Post Office Protocol (POP) that includes Kerberos authentication
> capability. Kerberos is a secure authentication mechanism that enables
> users to access network resources without disclosing their passwords in
> plaintext over the network.
> 
> Using KPOP, clients can authenticate to a mail server using Kerberos
> credentials instead of transmitting plaintext passwords over the
> network. This adds an additional layer of protection for POP
> connections, making it harder for an attacker to intercept and obtain
> credentials. KPOP is primarily utilized in situations where Kerberos is
> already deployed, and it enables single sign-on for email clients.
> 
> KPOP is an older protocol that is not as widely supported as current
> email protocols, such as IMAP and SMTP, which have built-in security
> improvements. Additionally, because KPOP is less prevalent than other
> email protocols, it is unlikely to be supported by the majority of
> email clients and servers.
> 
> Greetings
>   Дилян

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