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# SPDX-FileCopyrightText: 2015 Eric Larson
#
# SPDX-License-Identifier: Apache-2.0
"""
The httplib2 algorithms ported for use with requests.
"""
from __future__ import annotations
import calendar
import logging
import re
import time
from email.utils import parsedate_tz
from typing import TYPE_CHECKING, Collection, Mapping
from pip._vendor.requests.structures import CaseInsensitiveDict
from pip._vendor.cachecontrol.cache import DictCache, SeparateBodyBaseCache
from pip._vendor.cachecontrol.serialize import Serializer
if TYPE_CHECKING:
from typing import Literal
from pip._vendor.requests import PreparedRequest
from pip._vendor.urllib3 import HTTPResponse
from pip._vendor.cachecontrol.cache import BaseCache
logger = logging.getLogger(__name__)
URI = re.compile(r"^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*)(\?([^#]*))?(#(.*))?")
PERMANENT_REDIRECT_STATUSES = (301, 308)
def parse_uri(uri: str) -> tuple[str, str, str, str, str]:
"""Parses a URI using the regex given in Appendix B of RFC 3986.
(scheme, authority, path, query, fragment) = parse_uri(uri)
"""
match = URI.match(uri)
assert match is not None
groups = match.groups()
return (groups[1], groups[3], groups[4], groups[6], groups[8])
class CacheController:
"""An interface to see if request should cached or not."""
def __init__(
self,
cache: BaseCache | None = None,
cache_etags: bool = True,
serializer: Serializer | None = None,
status_codes: Collection[int] | None = None,
):
self.cache = DictCache() if cache is None else cache
self.cache_etags = cache_etags
self.serializer = serializer or Serializer()
self.cacheable_status_codes = status_codes or (200, 203, 300, 301, 308)
@classmethod
def _urlnorm(cls, uri: str) -> str:
"""Normalize the URL to create a safe key for the cache"""
(scheme, authority, path, query, fragment) = parse_uri(uri)
if not scheme or not authority:
raise Exception("Only absolute URIs are allowed. uri = %s" % uri)
scheme = scheme.lower()
authority = authority.lower()
if not path:
path = "/"
# Could do syntax based normalization of the URI before
# computing the digest. See Section 6.2.2 of Std 66.
request_uri = query and "?".join([path, query]) or path
defrag_uri = scheme + "://" + authority + request_uri
return defrag_uri
@classmethod
def cache_url(cls, uri: str) -> str:
return cls._urlnorm(uri)
def parse_cache_control(self, headers: Mapping[str, str]) -> dict[str, int | None]:
known_directives = {
# https://tools.ietf.org/html/rfc7234#section-5.2
"max-age": (int, True),
"max-stale": (int, False),
"min-fresh": (int, True),
"no-cache": (None, False),
"no-store": (None, False),
"no-transform": (None, False),
"only-if-cached": (None, False),
"must-revalidate": (None, False),
"public": (None, False),
"private": (None, False),
"proxy-revalidate": (None, False),
"s-maxage": (int, True),
}
cc_headers = headers.get("cache-control", headers.get("Cache-Control", ""))
retval: dict[str, int | None] = {}
for cc_directive in cc_headers.split(","):
if not cc_directive.strip():
continue
parts = cc_directive.split("=", 1)
directive = parts[0].strip()
try:
typ, required = known_directives[directive]
except KeyError:
logger.debug("Ignoring unknown cache-control directive: %s", directive)
continue
if not typ or not required:
retval[directive] = None
if typ:
try:
retval[directive] = typ(parts[1].strip())
except IndexError:
if required:
logger.debug(
"Missing value for cache-control " "directive: %s",
directive,
)
except ValueError:
logger.debug(
"Invalid value for cache-control directive " "%s, must be %s",
directive,
typ.__name__,
)
return retval
def _load_from_cache(self, request: PreparedRequest) -> HTTPResponse | None:
"""
Load a cached response, or return None if it's not available.
"""
cache_url = request.url
assert cache_url is not None
cache_data = self.cache.get(cache_url)
if cache_data is None:
logger.debug("No cache entry available")
return None
if isinstance(self.cache, SeparateBodyBaseCache):
body_file = self.cache.get_body(cache_url)
else:
body_file = None
result = self.serializer.loads(request, cache_data, body_file)
if result is None:
logger.warning("Cache entry deserialization failed, entry ignored")
return result
def cached_request(self, request: PreparedRequest) -> HTTPResponse | Literal[False]:
"""
Return a cached response if it exists in the cache, otherwise
return False.
"""
assert request.url is not None
cache_url = self.cache_url(request.url)
logger.debug('Looking up "%s" in the cache', cache_url)
cc = self.parse_cache_control(request.headers)
# Bail out if the request insists on fresh data
if "no-cache" in cc:
logger.debug('Request header has "no-cache", cache bypassed')
return False
if "max-age" in cc and cc["max-age"] == 0:
logger.debug('Request header has "max_age" as 0, cache bypassed')
return False
# Check whether we can load the response from the cache:
resp = self._load_from_cache(request)
if not resp:
return False
# If we have a cached permanent redirect, return it immediately. We
# don't need to test our response for other headers b/c it is
# intrinsically "cacheable" as it is Permanent.
#
# See:
# https://tools.ietf.org/html/rfc7231#section-6.4.2
#
# Client can try to refresh the value by repeating the request
# with cache busting headers as usual (ie no-cache).
if int(resp.status) in PERMANENT_REDIRECT_STATUSES:
msg = (
"Returning cached permanent redirect response "
"(ignoring date and etag information)"
)
logger.debug(msg)
return resp
headers: CaseInsensitiveDict[str] = CaseInsensitiveDict(resp.headers)
if not headers or "date" not in headers:
if "etag" not in headers:
# Without date or etag, the cached response can never be used
# and should be deleted.
logger.debug("Purging cached response: no date or etag")
self.cache.delete(cache_url)
logger.debug("Ignoring cached response: no date")
return False
now = time.time()
time_tuple = parsedate_tz(headers["date"])
assert time_tuple is not None
date = calendar.timegm(time_tuple[:6])
current_age = max(0, now - date)
logger.debug("Current age based on date: %i", current_age)
# TODO: There is an assumption that the result will be a
# urllib3 response object. This may not be best since we
# could probably avoid instantiating or constructing the
# response until we know we need it.
resp_cc = self.parse_cache_control(headers)
# determine freshness
freshness_lifetime = 0
# Check the max-age pragma in the cache control header
max_age = resp_cc.get("max-age")
if max_age is not None:
freshness_lifetime = max_age
logger.debug("Freshness lifetime from max-age: %i", freshness_lifetime)
# If there isn't a max-age, check for an expires header
elif "expires" in headers:
expires = parsedate_tz(headers["expires"])
if expires is not None:
expire_time = calendar.timegm(expires[:6]) - date
freshness_lifetime = max(0, expire_time)
logger.debug("Freshness lifetime from expires: %i", freshness_lifetime)
# Determine if we are setting freshness limit in the
# request. Note, this overrides what was in the response.
max_age = cc.get("max-age")
if max_age is not None:
freshness_lifetime = max_age
logger.debug(
"Freshness lifetime from request max-age: %i", freshness_lifetime
)
min_fresh = cc.get("min-fresh")
if min_fresh is not None:
# adjust our current age by our min fresh
current_age += min_fresh
logger.debug("Adjusted current age from min-fresh: %i", current_age)
# Return entry if it is fresh enough
if freshness_lifetime > current_age:
logger.debug('The response is "fresh", returning cached response')
logger.debug("%i > %i", freshness_lifetime, current_age)
return resp
# we're not fresh. If we don't have an Etag, clear it out
if "etag" not in headers:
logger.debug('The cached response is "stale" with no etag, purging')
self.cache.delete(cache_url)
# return the original handler
return False
def conditional_headers(self, request: PreparedRequest) -> dict[str, str]:
resp = self._load_from_cache(request)
new_headers = {}
if resp:
headers: CaseInsensitiveDict[str] = CaseInsensitiveDict(resp.headers)
if "etag" in headers:
new_headers["If-None-Match"] = headers["ETag"]
if "last-modified" in headers:
new_headers["If-Modified-Since"] = headers["Last-Modified"]
return new_headers
def _cache_set(
self,
cache_url: str,
request: PreparedRequest,
response: HTTPResponse,
body: bytes | None = None,
expires_time: int | None = None,
) -> None:
"""
Store the data in the cache.
"""
if isinstance(self.cache, SeparateBodyBaseCache):
# We pass in the body separately; just put a placeholder empty
# string in the metadata.
self.cache.set(
cache_url,
self.serializer.dumps(request, response, b""),
expires=expires_time,
)
# body is None can happen when, for example, we're only updating
# headers, as is the case in update_cached_response().
if body is not None:
self.cache.set_body(cache_url, body)
else:
self.cache.set(
cache_url,
self.serializer.dumps(request, response, body),
expires=expires_time,
)
def cache_response(
self,
request: PreparedRequest,
response: HTTPResponse,
body: bytes | None = None,
status_codes: Collection[int] | None = None,
) -> None:
"""
Algorithm for caching requests.
This assumes a requests Response object.
"""
# From httplib2: Don't cache 206's since we aren't going to
# handle byte range requests
cacheable_status_codes = status_codes or self.cacheable_status_codes
if response.status not in cacheable_status_codes:
logger.debug(
"Status code %s not in %s", response.status, cacheable_status_codes
)
return
response_headers: CaseInsensitiveDict[str] = CaseInsensitiveDict(
response.headers
)
if "date" in response_headers:
time_tuple = parsedate_tz(response_headers["date"])
assert time_tuple is not None
date = calendar.timegm(time_tuple[:6])
else:
date = 0
# If we've been given a body, our response has a Content-Length, that
# Content-Length is valid then we can check to see if the body we've
# been given matches the expected size, and if it doesn't we'll just
# skip trying to cache it.
if (
body is not None
and "content-length" in response_headers
and response_headers["content-length"].isdigit()
and int(response_headers["content-length"]) != len(body)
):
return
cc_req = self.parse_cache_control(request.headers)
cc = self.parse_cache_control(response_headers)
assert request.url is not None
cache_url = self.cache_url(request.url)
logger.debug('Updating cache with response from "%s"', cache_url)
# Delete it from the cache if we happen to have it stored there
no_store = False
if "no-store" in cc:
no_store = True
logger.debug('Response header has "no-store"')
if "no-store" in cc_req:
no_store = True
logger.debug('Request header has "no-store"')
if no_store and self.cache.get(cache_url):
logger.debug('Purging existing cache entry to honor "no-store"')
self.cache.delete(cache_url)
if no_store:
return
# https://tools.ietf.org/html/rfc7234#section-4.1:
# A Vary header field-value of "*" always fails to match.
# Storing such a response leads to a deserialization warning
# during cache lookup and is not allowed to ever be served,
# so storing it can be avoided.
if "*" in response_headers.get("vary", ""):
logger.debug('Response header has "Vary: *"')
return
# If we've been given an etag, then keep the response
if self.cache_etags and "etag" in response_headers:
expires_time = 0
if response_headers.get("expires"):
expires = parsedate_tz(response_headers["expires"])
if expires is not None:
expires_time = calendar.timegm(expires[:6]) - date
expires_time = max(expires_time, 14 * 86400)
logger.debug(f"etag object cached for {expires_time} seconds")
logger.debug("Caching due to etag")
self._cache_set(cache_url, request, response, body, expires_time)
# Add to the cache any permanent redirects. We do this before looking
# that the Date headers.
elif int(response.status) in PERMANENT_REDIRECT_STATUSES:
logger.debug("Caching permanent redirect")
self._cache_set(cache_url, request, response, b"")
# Add to the cache if the response headers demand it. If there
# is no date header then we can't do anything about expiring
# the cache.
elif "date" in response_headers:
time_tuple = parsedate_tz(response_headers["date"])
assert time_tuple is not None
date = calendar.timegm(time_tuple[:6])
# cache when there is a max-age > 0
max_age = cc.get("max-age")
if max_age is not None and max_age > 0:
logger.debug("Caching b/c date exists and max-age > 0")
expires_time = max_age
self._cache_set(
cache_url,
request,
response,
body,
expires_time,
)
# If the request can expire, it means we should cache it
# in the meantime.
elif "expires" in response_headers:
if response_headers["expires"]:
expires = parsedate_tz(response_headers["expires"])
if expires is not None:
expires_time = calendar.timegm(expires[:6]) - date
else:
expires_time = None
logger.debug(
"Caching b/c of expires header. expires in {} seconds".format(
expires_time
)
)
self._cache_set(
cache_url,
request,
response,
body,
expires_time,
)
def update_cached_response(
self, request: PreparedRequest, response: HTTPResponse
) -> HTTPResponse:
"""On a 304 we will get a new set of headers that we want to
update our cached value with, assuming we have one.
This should only ever be called when we've sent an ETag and
gotten a 304 as the response.
"""
assert request.url is not None
cache_url = self.cache_url(request.url)
cached_response = self._load_from_cache(request)
if not cached_response:
# we didn't have a cached response
return response
# Lets update our headers with the headers from the new request:
# http://tools.ietf.org/html/draft-ietf-httpbis-p4-conditional-26#section-4.1
#
# The server isn't supposed to send headers that would make
# the cached body invalid. But... just in case, we'll be sure
# to strip out ones we know that might be problmatic due to
# typical assumptions.
excluded_headers = ["content-length"]
cached_response.headers.update(
{
k: v
for k, v in response.headers.items() # type: ignore[no-untyped-call]
if k.lower() not in excluded_headers
}
)
# we want a 200 b/c we have content via the cache
cached_response.status = 200
# update our cache
self._cache_set(cache_url, request, cached_response)
return cached_response