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Require CRLF line endings in request line and headers #138

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Jul 2, 2024
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Require CRLF line endings in request line and headers #138

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4 changes: 2 additions & 2 deletions lib/webrick/httprequest.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -458,7 +458,7 @@ def read_request_line(socket)
end

@request_time = Time.now
if /^(\S+)\s+(\S++)(?:\s+HTTP\/(\d+\.\d+))?\r?\n/mo =~ @request_line
if /^(\S+) (\S++)(?: HTTP\/(\d+\.\d+))?\r\n/mo =~ @request_line
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I think the old behavior is technically RFC-compliant.

RFC 9112 section 3:

Although the request-line grammar rule requires that each of the component elements be separated by a single SP octet, recipients MAY instead parse on whitespace-delimited word boundaries and, aside from the CRLF terminator, treat any form of whitespace as the SP separator while ignoring preceding or trailing whitespace; such whitespace includes one or more of the following octets: SP, HTAB, VT (%x0B), FF (%x0C), or bare CR. However, lenient parsing can result in request smuggling security vulnerabilities if there are multiple recipients of the message and each has its own unique interpretation of robustness (see Section 11.2).

That said, this isn't a bad change. Apache rejects request lines that use whitespace other than a single SP octet, so I don't think you'll break compatibility with any clients by tightening this up.

@request_method = $1
@unparsed_uri = $2
@http_version = HTTPVersion.new($3 ? $3 : "0.9")
Expand All @@ -471,7 +471,7 @@ def read_request_line(socket)
def read_header(socket)
if socket
while line = read_line(socket)
break if /\A(#{CRLF}|#{LF})\z/om =~ line
break if /\A#{CRLF}\z/om =~ line
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Similarly, breaking lines on bare LF is allowed by the RFCs, so the old behavior was not a violation. From RFC 9112, section 2.2:

Although the line terminator for the start-line and fields is the sequence CRLF, a recipient MAY recognize a single LF as a line terminator and ignore any preceding CR.

Again, many popular servers (Apache, Lighttpd, Node.js, Passenger, Puma) require CRLF line endings, so you're unlikely to break compatibility by joining that club.

if (@request_bytes += line.bytesize) > MAX_HEADER_LENGTH
raise HTTPStatus::RequestEntityTooLarge, 'headers too large'
end
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10 changes: 6 additions & 4 deletions lib/webrick/httputils.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -173,16 +173,18 @@ def parse_header(raw)
field = nil
raw.each_line{|line|
case line
when /^([A-Za-z0-9!\#$%&'*+\-.^_`|~]+):(.*?)\z/om
field, value = $1, $2.strip
when /^([A-Za-z0-9!\#$%&'*+\-.^_`|~]+):([^\r\n\0]*?)\r\n\z/om
field, value = $1, $2
field.downcase!
header[field] = HEADER_CLASSES[field].new unless header.has_key?(field)
header[field] << value
when /^\s+(.*?)/om
value = line.strip
when /^\s+([^\r\n\0]*?)\r\n/om
unless field
raise HTTPStatus::BadRequest, "bad header '#{line}'."
end
value = line
value.lstrip!
value.slice!(-2..-1)
header[field][-1] << " " << value
else
raise HTTPStatus::BadRequest, "bad header '#{line}'."
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2 changes: 1 addition & 1 deletion test/webrick/test_filehandler.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -33,7 +33,7 @@ def make_range_request(range_spec)
Range: #{range_spec}
END_OF_REQUEST
return StringIO.new(msg.gsub(/^ {6}/, ""))
return StringIO.new(msg.gsub(/^ {6}/, "").gsub("\n", "\r\n"))
end

def make_range_response(file, range_spec)
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