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import hashlib
from typing import TYPE_CHECKING, BinaryIO, Dict, Iterator, List
from pip._internal.exceptions import HashMismatch, HashMissing, InstallationError
from pip._internal.utils.misc import read_chunks
if TYPE_CHECKING:
from hashlib import _Hash
# NoReturn introduced in 3.6.2; imported only for type checking to maintain
# pip compatibility with older patch versions of Python 3.6
from typing import NoReturn
# The recommended hash algo of the moment. Change this whenever the state of
# the art changes; it won't hurt backward compatibility.
FAVORITE_HASH = "sha256"
# Names of hashlib algorithms allowed by the --hash option and ``pip hash``
# Currently, those are the ones at least as collision-resistant as sha256.
STRONG_HASHES = ["sha256", "sha384", "sha512"]
class Hashes:
"""A wrapper that builds multiple hashes at once and checks them against
known-good values
"""
def __init__(self, hashes: Dict[str, List[str]] = None) -> None:
"""
:param hashes: A dict of algorithm names pointing to lists of allowed
hex digests
"""
allowed = {}
if hashes is not None:
for alg, keys in hashes.items():
# Make sure values are always sorted (to ease equality checks)
allowed[alg] = sorted(keys)
self._allowed = allowed
def __and__(self, other: "Hashes") -> "Hashes":
if not isinstance(other, Hashes):
return NotImplemented
# If either of the Hashes object is entirely empty (i.e. no hash
# specified at all), all hashes from the other object are allowed.
if not other:
return self
if not self:
return other
# Otherwise only hashes that present in both objects are allowed.
new = {}
for alg, values in other._allowed.items():
if alg not in self._allowed:
continue
new[alg] = [v for v in values if v in self._allowed[alg]]
return Hashes(new)
@property
def digest_count(self) -> int:
return sum(len(digests) for digests in self._allowed.values())
def is_hash_allowed(self, hash_name: str, hex_digest: str) -> bool:
"""Return whether the given hex digest is allowed."""
return hex_digest in self._allowed.get(hash_name, [])
def check_against_chunks(self, chunks: Iterator[bytes]) -> None:
"""Check good hashes against ones built from iterable of chunks of
data.
Raise HashMismatch if none match.
"""
gots = {}
for hash_name in self._allowed.keys():
try:
gots[hash_name] = hashlib.new(hash_name)
except (ValueError, TypeError):
raise InstallationError(f"Unknown hash name: {hash_name}")
for chunk in chunks:
for hash in gots.values():
hash.update(chunk)
for hash_name, got in gots.items():
if got.hexdigest() in self._allowed[hash_name]:
return
self._raise(gots)
def _raise(self, gots: Dict[str, "_Hash"]) -> "NoReturn":
raise HashMismatch(self._allowed, gots)
def check_against_file(self, file: BinaryIO) -> None:
"""Check good hashes against a file-like object
Raise HashMismatch if none match.
"""
return self.check_against_chunks(read_chunks(file))
def check_against_path(self, path: str) -> None:
with open(path, "rb") as file:
return self.check_against_file(file)
def __bool__(self) -> bool:
"""Return whether I know any known-good hashes."""
return bool(self._allowed)
def __eq__(self, other: object) -> bool:
if not isinstance(other, Hashes):
return NotImplemented
return self._allowed == other._allowed
def __hash__(self) -> int:
return hash(
",".join(
sorted(
":".join((alg, digest))
for alg, digest_list in self._allowed.items()
for digest in digest_list
)
)
)
class MissingHashes(Hashes):
"""A workalike for Hashes used when we're missing a hash for a requirement
It computes the actual hash of the requirement and raises a HashMissing
exception showing it to the user.
"""
def __init__(self) -> None:
"""Don't offer the ``hashes`` kwarg."""
# Pass our favorite hash in to generate a "gotten hash". With the
# empty list, it will never match, so an error will always raise.
super().__init__(hashes={FAVORITE_HASH: []})
def _raise(self, gots: Dict[str, "_Hash"]) -> "NoReturn":
raise HashMissing(gots[FAVORITE_HASH].hexdigest())
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