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net/smtp: deprecate CRAMMD5Auth #61952

Open Neustradamus opened 1 year ago

Neustradamus commented 1 year ago

Dear @golang team,

Can you remove old unsecure CRAM-MD5 from the code?

It is unsecure:

Time to add SCRAM-SHA-*(-PLUS) supports.

Latest IMAP RFC speaks about:

Thanks in advance.

seankhliao commented 1 year ago

We cannot remove it as that would be a break in backwards compatibility maybe we can mark it deprecated @golang/security @bradfitz

drakkan commented 1 year ago

Hello, I have a WIP patch to add SCRAM-SHA-256 support. I tested it against Postfix with SMTP AUTH through Dovecot SASL.

The SCRAM algorithm requires pbkdf2 and according to RFC 5802 section 5.1 we have to apply the SASLprep profile [RFC4013] of the "stringprep" algorithm [RFC3454]. Since RFC 8265 obsoletes RFC 4013 I think we can use it instead. RFC 8265 is already implemented in golang.org/x/text/secure/precis.

So we need the following dependencies:

are they acceptable for net/smtp ?

Neustradamus commented 1 year ago

@drakkan: Nice :)

It is possible to support SCRAM-SHA-1/SCRAM-SHA-1-PLUS, SCRAM-SHA-256/SCRAM-SHA-256-PLUS, SCRAM-SHA-512/SCRAM-SHA-512-PLUS, SCRAM-SHA3-512/SCRAM-SHA3-512-PLUS? Not only 256.

For examples (more at the next link):

All details here:

drakkan commented 1 year ago

@drakkan: Nice :)

It is possible to support SCRAM-SHA-1/SCRAM-SHA-1-PLUS, SCRAM-SHA-256/SCRAM-SHA-256-PLUS, SCRAM-SHA-512/SCRAM-SHA-512-PLUS, SCRAM-SHA3-512/SCRAM-SHA3-512-PLUS? Not only 256.

I haven't looked at channel binding for the PLUS variants yet. The other variants can be added easily but I'm a little worried about SHA-1, nowadays it's not considered secure anymore.

Before completing this work and submitting a CL, I would like to get feedback on the x/crypto and x/text dependencies from the net/smtp maintainers. I would like to avoid working on something that can't be merged

For examples (more at the next link):

  • Exim uses GNU SASL and support TLS Channel Binding
  • Cyrus-SASL has more supports than Postfix/Dovecot

All details here:

Neustradamus commented 1 year ago

@drakkan: Thanks for your reply!

For example, SCRAM-SHA-1 and SCRAM-SHA-1-PLUS are used by default since a very long time by XMPP, you can see here:

To have a real compatibility with all products, it is needed to support SCRAM-SHA-*(-PLUS) included SHA-1. Of course, it is better to use SCRAM-SHA-1 than CRAM-MD5/DIGEST-MD5/LOGIN/PLAIN.

Some products which support SCRAM-SHA-*(-PLUS) and SCRAM-SHA3-512(-PLUS):

About Channel Bindings -> RFC 9266: Channel Bindings for TLS 1.3:

Little details, to know easily:

drakkan commented 1 week ago

Just a quick update on SCRAM support. From the net/smtp docs:

The smtp package is frozen and is not accepting new features. Some external packages provide more functionality.

So it is unlikely this feature will be implemented in net/smtp, however @wneessen is about to complete my WIP, see here