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From "Stefano Bagnara (JIRA)" <mime4j-...@james.apache.org>
Subject [jira] Commented: (MIME4J-58) Lenient dealing with headless messages or malformed header/body separation
Date Thu, 31 Dec 2009 10:38:29 GMT

    [ https://issues.apache.org/jira/browse/MIME4J-58?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12795582#action_12795582
] 

Stefano Bagnara commented on MIME4J-58:
---------------------------------------

I did this mainly because of memory/performance reasons:
- the internal buffer can be much smaller than the field buffer. The internal buffer is usually
4096 or 2*boundarylength while the fieldBuffer could be much bigger (unlikely, but it could
be even 100kb.)
- to copy to the internal buffer I would have needed to move around bytes already in the buffer,
enlarge it to ensure fieldBuffer capacity and so on, after that the buffer would have been
permanently enlarged. (this would have probably led to write also a shrink method).
- currently I don't use 2 buffers: the temporary buffer used IS the byte array used in the
parseField method: calling unread you simply concede your buffer to the linestreamreader.
After the next "readLine" the temporary buffer won't be used anymore.

> Lenient dealing with headless messages or malformed header/body separation
> --------------------------------------------------------------------------
>
>                 Key: MIME4J-58
>                 URL: https://issues.apache.org/jira/browse/MIME4J-58
>             Project: JAMES Mime4j
>          Issue Type: Task
>    Affects Versions: 0.3
>            Reporter: Stefano Bagnara
>             Fix For: 0.8
>
>         Attachments: headerbody-nocrlfcrlf.msg, headerbody-noheader.msg
>
>
> Define how to deal with non canonical messages like this one:
> -----------------------
> This is a simple message not having headers.
> The whole text should be recognized as body.
> -----------------------
> or this one:
> -----------------------
> Subject: this is a subject
> This is an invalid header
> AnotherHeader: is this an header or the first part of the body?
> Body text
> -----------------------
> In the first case mime4j output twice an  "invalid header" error and a roundtrip write
result in an empty message.
> In the SMTP case this is unfortunate because sometimes it happens messages are sent without
header.
> In the second case mime4j currenlty take Subject and AnotherHeader as headers and "This
is an invalid header" raise a monitor for "invalid header" and "Body text" is considered the
body.
> A compromise we evaluated in past between compliance, leniency and performace was to
"alter" the requirement for CRLFCRLF between headers and body with a different rule: if during
parsing of the headers we find a line (not multiline) and not including an "HeaderName: something"
then we virtually add a CRLF *before* that line and consider that line the first line of the
body. This allow us to only buffer a single line (as opposite to parsing the whole message
in search of a CRLFCRLF and consider the full message a body if no CRLFCRLF is found) and
to be very lenient with input. The "side effect" (maybe not bad) is that a wrong header in
the middle of headers will result in some headers moved to the body.
> With this algorythm the above would be "virtually" parsed as it was:
> -----------------------
> This is a simple message not having headers.
> The whole text should be recognized as body.
> -----------------------
> or this one:
> -----------------------
> Subject: this is a subject
> This is an invalid header
> AnotherHeader: is this an header or the first part of the body?
> Body text
> -----------------------
> If we think about strict and lenient approaches I think that current mime4j result is
ok when using a strict parsing, while the one I propose is a good lenient alternative.
> Opinions? Alternatives?

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