• Tom Bergan's avatar
    net/textproto: reject all headers with a leading space · 1c69384d
    Tom Bergan authored
    Previously, golang.org/cl/75350 updated ReadMIMEHeader to ignore the
    first header line when it begins with a leading space, as in the
    following example:
    
    GET / HTTP/1.1
      Host: foo.com
    Accept-Encoding: gzip
    
    However, golang.org/cl/75350 changed ReadMIMEHeader's behavior for the
    following example: before the CL it returned an error, but after the
    CL it ignored the first line.
    
    GET / HTTP/1.1
      Host foo.com
    Accept-Encoding: gzip
    
    This change updates ReadMIMEHeader to always fail when the first header
    line starts with a space. During the discussion for golang.org/cl/75350,
    we realized we had three competing needs:
    
    1. HTTP clients should accept malformed response headers when possible
       (ignoring the malformed lines).
    
    2. HTTP servers should reject all malformed request headers.
    
    3. The net/textproto package is used by multiple protocols (most notably,
       HTTP and SMTP) which have slightly different parsing semantics. This
       complicates changes to net/textproto.
    
    We weren't sure how to best fix net/textproto without an API change, but
    it is too late for API changes in Go 1.10. We decided to ignore initial
    lines that begin with spaces, thinking that would have the least impact on
    existing users -- malformed headers would continue to parse, but the
    initial lines would be ignored. Instead, golang.org/cl/75350 actually
    changed ReadMIMEHeader to succeed in cases where it previously failed
    (as in the above example).
    
    Reconsidering the above two examples, there does not seem to be a good
    argument to silently ignore ` Host: foo.com` but fail on ` Host foo.com`.
    Hence, this change fails for *all* headers where the initial line begins
    with a space.
    
    Updates #22464
    
    Change-Id: I68d3d190489c350b0bc1549735bf6593fe11a94c
    Reviewed-on: https://go-review.googlesource.com/80055
    Run-TryBot: Tom Bergan <tombergan@google.com>
    TryBot-Result: Gobot Gobot <gobot@golang.org>
    Reviewed-by: 's avatarBrad Fitzpatrick <bradfitz@golang.org>
    1c69384d
reader_test.go 11.7 KB