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Diffstat (limited to 'venv/lib/python3.11/site-packages/h11/_headers.py')
| -rw-r--r-- | venv/lib/python3.11/site-packages/h11/_headers.py | 278 |
1 files changed, 278 insertions, 0 deletions
diff --git a/venv/lib/python3.11/site-packages/h11/_headers.py b/venv/lib/python3.11/site-packages/h11/_headers.py new file mode 100644 index 0000000..b97d020 --- /dev/null +++ b/venv/lib/python3.11/site-packages/h11/_headers.py @@ -0,0 +1,278 @@ +import re +from typing import AnyStr, cast, List, overload, Sequence, Tuple, TYPE_CHECKING, Union + +from ._abnf import field_name, field_value +from ._util import bytesify, LocalProtocolError, validate + +if TYPE_CHECKING: + from ._events import Request + +try: + from typing import Literal +except ImportError: + from typing_extensions import Literal # type: ignore + + +# Facts +# ----- +# +# Headers are: +# keys: case-insensitive ascii +# values: mixture of ascii and raw bytes +# +# "Historically, HTTP has allowed field content with text in the ISO-8859-1 +# charset [ISO-8859-1], supporting other charsets only through use of +# [RFC2047] encoding. In practice, most HTTP header field values use only a +# subset of the US-ASCII charset [USASCII]. Newly defined header fields SHOULD +# limit their field values to US-ASCII octets. A recipient SHOULD treat other +# octets in field content (obs-text) as opaque data." +# And it deprecates all non-ascii values +# +# Leading/trailing whitespace in header names is forbidden +# +# Values get leading/trailing whitespace stripped +# +# Content-Disposition actually needs to contain unicode semantically; to +# accomplish this it has a terrifically weird way of encoding the filename +# itself as ascii (and even this still has lots of cross-browser +# incompatibilities) +# +# Order is important: +# "a proxy MUST NOT change the order of these field values when forwarding a +# message" +# (and there are several headers where the order indicates a preference) +# +# Multiple occurences of the same header: +# "A sender MUST NOT generate multiple header fields with the same field name +# in a message unless either the entire field value for that header field is +# defined as a comma-separated list [or the header is Set-Cookie which gets a +# special exception]" - RFC 7230. (cookies are in RFC 6265) +# +# So every header aside from Set-Cookie can be merged by b", ".join if it +# occurs repeatedly. But, of course, they can't necessarily be split by +# .split(b","), because quoting. +# +# Given all this mess (case insensitive, duplicates allowed, order is +# important, ...), there doesn't appear to be any standard way to handle +# headers in Python -- they're almost like dicts, but... actually just +# aren't. For now we punt and just use a super simple representation: headers +# are a list of pairs +# +# [(name1, value1), (name2, value2), ...] +# +# where all entries are bytestrings, names are lowercase and have no +# leading/trailing whitespace, and values are bytestrings with no +# leading/trailing whitespace. Searching and updating are done via naive O(n) +# methods. +# +# Maybe a dict-of-lists would be better? + +_content_length_re = re.compile(rb"[0-9]+") +_field_name_re = re.compile(field_name.encode("ascii")) +_field_value_re = re.compile(field_value.encode("ascii")) + + +class Headers(Sequence[Tuple[bytes, bytes]]): + """ + A list-like interface that allows iterating over headers as byte-pairs + of (lowercased-name, value). + + Internally we actually store the representation as three-tuples, + including both the raw original casing, in order to preserve casing + over-the-wire, and the lowercased name, for case-insensitive comparisions. + + r = Request( + method="GET", + target="/", + headers=[("Host", "example.org"), ("Connection", "keep-alive")], + http_version="1.1", + ) + assert r.headers == [ + (b"host", b"example.org"), + (b"connection", b"keep-alive") + ] + assert r.headers.raw_items() == [ + (b"Host", b"example.org"), + (b"Connection", b"keep-alive") + ] + """ + + __slots__ = "_full_items" + + def __init__(self, full_items: List[Tuple[bytes, bytes, bytes]]) -> None: + self._full_items = full_items + + def __bool__(self) -> bool: + return bool(self._full_items) + + def __eq__(self, other: object) -> bool: + return list(self) == list(other) # type: ignore + + def __len__(self) -> int: + return len(self._full_items) + + def __repr__(self) -> str: + return "<Headers(%s)>" % repr(list(self)) + + def __getitem__(self, idx: int) -> Tuple[bytes, bytes]: # type: ignore[override] + _, name, value = self._full_items[idx] + return (name, value) + + def raw_items(self) -> List[Tuple[bytes, bytes]]: + return [(raw_name, value) for raw_name, _, value in self._full_items] + + +HeaderTypes = Union[ + List[Tuple[bytes, bytes]], + List[Tuple[bytes, str]], + List[Tuple[str, bytes]], + List[Tuple[str, str]], +] + + +@overload +def normalize_and_validate(headers: Headers, _parsed: Literal[True]) -> Headers: + ... + + +@overload +def normalize_and_validate(headers: HeaderTypes, _parsed: Literal[False]) -> Headers: + ... + + +@overload +def normalize_and_validate( + headers: Union[Headers, HeaderTypes], _parsed: bool = False +) -> Headers: + ... + + +def normalize_and_validate( + headers: Union[Headers, HeaderTypes], _parsed: bool = False +) -> Headers: + new_headers = [] + seen_content_length = None + saw_transfer_encoding = False + for name, value in headers: + # For headers coming out of the parser, we can safely skip some steps, + # because it always returns bytes and has already run these regexes + # over the data: + if not _parsed: + name = bytesify(name) + value = bytesify(value) + validate(_field_name_re, name, "Illegal header name {!r}", name) + validate(_field_value_re, value, "Illegal header value {!r}", value) + assert isinstance(name, bytes) + assert isinstance(value, bytes) + + raw_name = name + name = name.lower() + if name == b"content-length": + lengths = {length.strip() for length in value.split(b",")} + if len(lengths) != 1: + raise LocalProtocolError("conflicting Content-Length headers") + value = lengths.pop() + validate(_content_length_re, value, "bad Content-Length") + if seen_content_length is None: + seen_content_length = value + new_headers.append((raw_name, name, value)) + elif seen_content_length != value: + raise LocalProtocolError("conflicting Content-Length headers") + elif name == b"transfer-encoding": + # "A server that receives a request message with a transfer coding + # it does not understand SHOULD respond with 501 (Not + # Implemented)." + # https://tools.ietf.org/html/rfc7230#section-3.3.1 + if saw_transfer_encoding: + raise LocalProtocolError( + "multiple Transfer-Encoding headers", error_status_hint=501 + ) + # "All transfer-coding names are case-insensitive" + # -- https://tools.ietf.org/html/rfc7230#section-4 + value = value.lower() + if value != b"chunked": + raise LocalProtocolError( + "Only Transfer-Encoding: chunked is supported", + error_status_hint=501, + ) + saw_transfer_encoding = True + new_headers.append((raw_name, name, value)) + else: + new_headers.append((raw_name, name, value)) + return Headers(new_headers) + + +def get_comma_header(headers: Headers, name: bytes) -> List[bytes]: + # Should only be used for headers whose value is a list of + # comma-separated, case-insensitive values. + # + # The header name `name` is expected to be lower-case bytes. + # + # Connection: meets these criteria (including cast insensitivity). + # + # Content-Length: technically is just a single value (1*DIGIT), but the + # standard makes reference to implementations that do multiple values, and + # using this doesn't hurt. Ditto, case insensitivity doesn't things either + # way. + # + # Transfer-Encoding: is more complex (allows for quoted strings), so + # splitting on , is actually wrong. For example, this is legal: + # + # Transfer-Encoding: foo; options="1,2", chunked + # + # and should be parsed as + # + # foo; options="1,2" + # chunked + # + # but this naive function will parse it as + # + # foo; options="1 + # 2" + # chunked + # + # However, this is okay because the only thing we are going to do with + # any Transfer-Encoding is reject ones that aren't just "chunked", so + # both of these will be treated the same anyway. + # + # Expect: the only legal value is the literal string + # "100-continue". Splitting on commas is harmless. Case insensitive. + # + out: List[bytes] = [] + for _, found_name, found_raw_value in headers._full_items: + if found_name == name: + found_raw_value = found_raw_value.lower() + for found_split_value in found_raw_value.split(b","): + found_split_value = found_split_value.strip() + if found_split_value: + out.append(found_split_value) + return out + + +def set_comma_header(headers: Headers, name: bytes, new_values: List[bytes]) -> Headers: + # The header name `name` is expected to be lower-case bytes. + # + # Note that when we store the header we use title casing for the header + # names, in order to match the conventional HTTP header style. + # + # Simply calling `.title()` is a blunt approach, but it's correct + # here given the cases where we're using `set_comma_header`... + # + # Connection, Content-Length, Transfer-Encoding. + new_headers: List[Tuple[bytes, bytes]] = [] + for found_raw_name, found_name, found_raw_value in headers._full_items: + if found_name != name: + new_headers.append((found_raw_name, found_raw_value)) + for new_value in new_values: + new_headers.append((name.title(), new_value)) + return normalize_and_validate(new_headers) + + +def has_expect_100_continue(request: "Request") -> bool: + # https://tools.ietf.org/html/rfc7231#section-5.1.1 + # "A server that receives a 100-continue expectation in an HTTP/1.0 request + # MUST ignore that expectation." + if request.http_version < b"1.1": + return False + expect = get_comma_header(request.headers, b"expect") + return b"100-continue" in expect |