[courier-users] Zdkimfilter 3.18

[Alessandro V. <ve...@ta...>]

This version puts quotes around display names in some cases.  This is not 
extraordinarily clean, e.g. in case of escapes using backslashes, a.k.a. 
Quoted-string, in the address.  Recall the famous sentence of RFC 5321, where 
it defines the address syntax (Section 4.1.2), it says:

    While the above definition for Local-part is relatively permissive,
    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.

Yet, the new code can change From: should.be.quoted <us...@ex...> to the 
correct form From: "should.be.quoted" <us...@ex...>, before signing and 
before Courier carries out the same change thereby invalidating the signature. 
Good MUAs should have fixed the address much before then.

This rewriting won't work when noaddrrewrite is set in zdkimfilter.conf. 
Recall that this parameter is automatically set when zdkimfilter is invoked by 
zdkimsign.  That dates back to when the parameter was set, for wrapping long 
addresses, which Courier handles differently for local sendmail than SMTP 
submission.  So there is no way to add quotes for locally generated mail 
messages.  Perhaps this can be changed, now that it's easier to set up new 
config files that include the default one.


Another change in 3.18 is rejecting messages with no or many From: header 
fields.  I saw zdkimfilter choked trying to determine the domain, and ended up 
by temporarily rejecting the message with a 4xx code.  With this fix it rejects 
with a 550 those messages.  Again, there is a parameter (still_allow_no_from) 
to disable the feature.

https://www.tana.it/sw/zdkimfilter/

Sorry for being so prolix

Best
Ale
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