Technical Summary
This document describes a method for displaying downgraded messages
which originally contain internationalized E-mail addresses or
internationalized header fields.
Working Group Summary
The WG has consensus on publishing this document as Experimental.
Document Quality
The author's organization has indicated intent to implement.
Personnel
Harald Alvestrand is the document shepherd for this document.
Alexey Melnikov is the responsible AD.
RFC Editor Note
Add a new paragraph at the end of Section 3.1:
NEW:
In any case where reconstruction of a particular downgraded header
field fails, both header fields (the "downgraded-YYY" header field and
the "YYY" header field) SHOULD be left in the message as they are.
The MUA MAY choose to communicate the situation to the user (see
Security Considerations).
In Section Section 3.2.2, remove the step # 2 and renumber the remaining
steps (Please also update step numbers in section 4 as well).
REMOVE:
2. If the header field is one that can only appear once, according
to the table in [RFC5322] section 3.6 ("From", "Sender", "To",
"CC", "BCC", "Reply-To"), locate the corresponding field in the
message's headers, and skip to step 9. Otherwise, continue with
step 3.
Replace the last sentence in Section 3.2.3 with:
OLD:
An MUA with such knowledge MAY use the procedure in
Section 3.2.2, above, for those fields that it knows about.
NEW:
An MUA with such knowledge MAY use the procedure similar to
the procedure in Section 3.2.2, above, for those fields that
it knows about. (Note that the whitespace canonicalization
rule might not be applicable to some header fields.)
In the Security Considerations section:
OLD:
For example, an organization's boundary MTA can modify "From:" lines
so that messages arriving from outside the organization are easily
distinguishable from internal emails. As a result of that rewriting,
it might not be possible to reconstruct the "Downgraded-From" header
field.
NEW:
For example, an organization's boundary MTA can modify "From:" lines
so that messages arriving from outside the organization are easily
distinguishable from internal emails. As a result of that rewriting,
the "From:" header field might not match the "Downgraded-From" header
field.
In Section 4:
OLD:
See "Security considerations" section in [RFC5504] and [RFC4952] for
more discussion.
NEW:
We have focused, here, on issues with displaying downgraded messages.
For more discussion of downgraded and internationalized messages in
general, see the "Security considerations" sections in [RFC5504] and
[RFC4952].