133 lines
4.7 KiB
Python
133 lines
4.7 KiB
Python
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# We use native strings for all the re patterns, to take advantage of string
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# formatting, and then convert to bytestrings when compiling the final re
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# objects.
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# https://svn.tools.ietf.org/svn/wg/httpbis/specs/rfc7230.html#whitespace
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# OWS = *( SP / HTAB )
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# ; optional whitespace
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OWS = r"[ \t]*"
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# https://svn.tools.ietf.org/svn/wg/httpbis/specs/rfc7230.html#rule.token.separators
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# token = 1*tchar
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#
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# tchar = "!" / "#" / "$" / "%" / "&" / "'" / "*"
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# / "+" / "-" / "." / "^" / "_" / "`" / "|" / "~"
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# / DIGIT / ALPHA
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# ; any VCHAR, except delimiters
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token = r"[-!#$%&'*+.^_`|~0-9a-zA-Z]+"
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# https://svn.tools.ietf.org/svn/wg/httpbis/specs/rfc7230.html#header.fields
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# field-name = token
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field_name = token
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# The standard says:
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#
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# field-value = *( field-content / obs-fold )
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# field-content = field-vchar [ 1*( SP / HTAB ) field-vchar ]
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# field-vchar = VCHAR / obs-text
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# obs-fold = CRLF 1*( SP / HTAB )
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# ; obsolete line folding
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# ; see Section 3.2.4
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#
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# https://tools.ietf.org/html/rfc5234#appendix-B.1
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#
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# VCHAR = %x21-7E
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# ; visible (printing) characters
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#
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# https://svn.tools.ietf.org/svn/wg/httpbis/specs/rfc7230.html#rule.quoted-string
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# obs-text = %x80-FF
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#
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# However, the standard definition of field-content is WRONG! It disallows
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# fields containing a single visible character surrounded by whitespace,
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# e.g. "foo a bar".
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#
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# See: https://www.rfc-editor.org/errata_search.php?rfc=7230&eid=4189
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#
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# So our definition of field_content attempts to fix it up...
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#
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# Also, we allow lots of control characters, because apparently people assume
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# that they're legal in practice (e.g., google analytics makes cookies with
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# \x01 in them!):
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# https://github.com/python-hyper/h11/issues/57
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# We still don't allow NUL or whitespace, because those are often treated as
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# meta-characters and letting them through can lead to nasty issues like SSRF.
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vchar = r"[\x21-\x7e]"
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vchar_or_obs_text = r"[^\x00\s]"
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field_vchar = vchar_or_obs_text
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field_content = r"{field_vchar}+(?:[ \t]+{field_vchar}+)*".format(**globals())
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# We handle obs-fold at a different level, and our fixed-up field_content
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# already grows to swallow the whole value, so ? instead of *
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field_value = r"({field_content})?".format(**globals())
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# header-field = field-name ":" OWS field-value OWS
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header_field = (
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r"(?P<field_name>{field_name})"
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r":"
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r"{OWS}"
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r"(?P<field_value>{field_value})"
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r"{OWS}".format(**globals())
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)
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# https://svn.tools.ietf.org/svn/wg/httpbis/specs/rfc7230.html#request.line
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#
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# request-line = method SP request-target SP HTTP-version CRLF
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# method = token
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# HTTP-version = HTTP-name "/" DIGIT "." DIGIT
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# HTTP-name = %x48.54.54.50 ; "HTTP", case-sensitive
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#
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# request-target is complicated (see RFC 7230 sec 5.3) -- could be path, full
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# URL, host+port (for connect), or even "*", but in any case we are guaranteed
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# that it contists of the visible printing characters.
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method = token
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request_target = r"{vchar}+".format(**globals())
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http_version = r"HTTP/(?P<http_version>[0-9]\.[0-9])"
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request_line = (
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r"(?P<method>{method})"
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r" "
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r"(?P<target>{request_target})"
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r" "
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r"{http_version}".format(**globals())
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)
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# https://svn.tools.ietf.org/svn/wg/httpbis/specs/rfc7230.html#status.line
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#
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# status-line = HTTP-version SP status-code SP reason-phrase CRLF
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# status-code = 3DIGIT
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# reason-phrase = *( HTAB / SP / VCHAR / obs-text )
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status_code = r"[0-9]{3}"
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reason_phrase = r"([ \t]|{vchar_or_obs_text})*".format(**globals())
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status_line = (
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r"{http_version}"
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r" "
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r"(?P<status_code>{status_code})"
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# However, there are apparently a few too many servers out there that just
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# leave out the reason phrase:
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# https://github.com/scrapy/scrapy/issues/345#issuecomment-281756036
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# https://github.com/seanmonstar/httparse/issues/29
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# so make it optional. ?: is a non-capturing group.
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r"(?: (?P<reason>{reason_phrase}))?".format(**globals())
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)
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HEXDIG = r"[0-9A-Fa-f]"
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# Actually
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#
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# chunk-size = 1*HEXDIG
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#
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# but we impose an upper-limit to avoid ridiculosity. len(str(2**64)) == 20
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chunk_size = r"({HEXDIG}){{1,20}}".format(**globals())
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# Actually
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#
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# chunk-ext = *( ";" chunk-ext-name [ "=" chunk-ext-val ] )
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#
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# but we aren't parsing the things so we don't really care.
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chunk_ext = r";.*"
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chunk_header = (
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r"(?P<chunk_size>{chunk_size})"
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r"(?P<chunk_ext>{chunk_ext})?"
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r"{OWS}\r\n".format(
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**globals()
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) # Even though the specification does not allow for extra whitespaces,
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# we are lenient with trailing whitespaces because some servers on the wild use it.
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)
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