p1: BWS

Mark Nottingham <mnot@mnot.net> Thu, 18 April 2013 01:19 UTC

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From: Mark Nottingham <mnot@mnot.net>
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Date: Thu, 18 Apr 2013 11:18:22 +1000
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Subject: p1: BWS
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p1 3.2.3 says:

>    BWS is used where the grammar allows optional whitespace, for
>    historical reasons, but senders SHOULD NOT generate it in messages;
>    recipients MUST accept such bad optional whitespace and remove it
>    before interpreting the field value or forwarding the message
>    downstream.


Throughout our specs, BWS is used at the end of header fields:
     header-field   = field-name ":" OWS field-value BWS

and in transfer-codings:
     transfer-parameter = attribute BWS "=" BWS value

and in Expect headers:
  expectation  = expect-name [ BWS "=" BWS expect-value]
                             *( OWS ";" [ OWS expect-param ] )
  expect-param = expect-name [ BWS "=" BWS expect-value ]

and, finally, in auth-params on challenges and credentials:
  auth-param     = token BWS "=" BWS ( token / quoted-string )

Is this whitespace really "bad" enough to MUST-require that intermediaries (including load balancers and other hardware!) remove it before forwarding the message?


Mark Nottingham   http://www.mnot.net/