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#!/usr/bin/env nix-shell
#! nix-shell -i "python3 -I" -p "python3.withPackages(p: with p; [ rich structlog ])"
from abc import ABC, abstractclassmethod, abstractmethod
from contextlib import contextmanager
from pathlib import Path
from structlog.contextvars import bound_contextvars as log_context
from typing import ClassVar, List, Tuple
import hashlib, re, structlog
logger = structlog.getLogger("sha-to-SRI")
class Encoding(ABC):
alphabet: ClassVar[str]
@classmethod
@property
def name(cls) -> str:
return cls.__name__.lower()
def toSRI(self, s: str) -> str:
digest = self.decode(s)
assert len(digest) == self.n
from base64 import b64encode
return f"{self.hashName}-{b64encode(digest).decode()}"
@classmethod
def all(cls, h) -> 'List[Encoding]':
return [ c(h) for c in cls.__subclasses__() ]
def __init__(self, h):
self.n = h.digest_size
self.hashName = h.name
@property
@abstractmethod
def length(self) -> int:
...
@property
def regex(self) -> str:
return f"[{self.alphabet}]{{{self.length}}}"
@abstractmethod
def decode(self, s: str) -> bytes:
...
class Nix32(Encoding):
alphabet = "0123456789abcdfghijklmnpqrsvwxyz"
inverted = { c: i for i, c in enumerate(alphabet) }
@property
def length(self):
return 1 + (8 * self.n) // 5
def decode(self, s: str):
assert len(s) == self.length
out = [ 0 for _ in range(self.n) ]
# TODO: Do better than a list of byte-sized ints
for n, c in enumerate(reversed(s)):
digit = self.inverted[c]
i, j = divmod(5 * n, 8)
out[i] = out[i] | (digit << j) & 0xff
rem = digit >> (8 - j)
if rem == 0:
continue
elif i < self.n:
out[i+1] = rem
else:
raise ValueError(f"Invalid nix32 hash: '{s}'")
return bytes(out)
class Hex(Encoding):
alphabet = "0-9A-Fa-f"
@property
def length(self):
return 2 * self.n
def decode(self, s: str):
from binascii import unhexlify
return unhexlify(s)
class Base64(Encoding):
alphabet = "A-Za-z0-9+/"
@property
def format(self) -> Tuple[int, int]:
"""Number of characters in data and padding."""
i, k = divmod(self.n, 3)
return 4 * i + (0 if k == 0 else k + 1), (3 - k) % 3
@property
def length(self):
return sum(self.format)
@property
def regex(self):
data, padding = self.format
return f"[{self.alphabet}]{{{data}}}={{{padding}}}"
def decode(self, s):
from base64 import b64decode
return b64decode(s, validate = True)
_HASHES = (hashlib.new(n) for n in ('SHA-256', 'SHA-512'))
ENCODINGS = {
h.name: Encoding.all(h)
for h in _HASHES
}
RE = {
h: "|".join(
(f"({h}-)?" if e.name == 'base64' else '') +
f"(?P<{h}_{e.name}>{e.regex})"
for e in encodings
) for h, encodings in ENCODINGS.items()
}
_DEF_RE = re.compile("|".join(
f"(?P<{h}>{h} = (?P<{h}_quote>['\"])({re})(?P={h}_quote);)"
for h, re in RE.items()
))
def defToSRI(s: str) -> str:
def f(m: re.Match[str]) -> str:
try:
for h, encodings in ENCODINGS.items():
if m.group(h) is None:
continue
for e in encodings:
s = m.group(f"{h}_{e.name}")
if s is not None:
return f'hash = "{e.toSRI(s)}";'
raise ValueError(f"Match with '{h}' but no subgroup")
raise ValueError("Match with no hash")
except ValueError as exn:
logger.error(
"Skipping",
exc_info = exn,
)
return m.group()
return _DEF_RE.sub(f, s)
@contextmanager
def atomicFileUpdate(target: Path):
'''Atomically replace the contents of a file.
Guarantees that no temporary files are left behind, and `target` is either
left untouched, or overwritten with new content if no exception was raised.
Yields a pair `(original, new)` of open files.
`original` is the pre-existing file at `target`, open for reading;
`new` is an empty, temporary file in the same filder, open for writing.
Upon exiting the context, the files are closed; if no exception was
raised, `new` (atomically) replaces the `target`, otherwise it is deleted.
'''
# That's mostly copied from noto-emoji.py, should DRY it out
from tempfile import mkstemp
fd, _p = mkstemp(
dir = target.parent,
prefix = target.name,
)
tmpPath = Path(_p)
try:
with target.open() as original:
with tmpPath.open('w') as new:
yield (original, new)
tmpPath.replace(target)
except Exception:
tmpPath.unlink(missing_ok = True)
raise
def fileToSRI(p: Path):
with atomicFileUpdate(p) as (og, new):
for i, line in enumerate(og):
with log_context(line=i):
new.write(defToSRI(line))
_SKIP_RE = re.compile(
"(generated by)|(do not edit)",
re.IGNORECASE
)
if __name__ == "__main__":
from sys import argv, stderr
logger.info("Starting!")
for arg in argv[1:]:
p = Path(arg)
with log_context(path=str(p)):
try:
if p.name == "yarn.nix" or p.name.find("generated") != -1:
logger.warning("File looks autogenerated, skipping!")
continue
with p.open() as f:
for line in f:
if line.strip():
break
if _SKIP_RE.search(line):
logger.warning("File looks autogenerated, skipping!")
continue
fileToSRI(p)
except Exception as exn:
logger.error(
"Unhandled exception, skipping file!",
exc_info = exn,
)
else:
logger.info("Finished processing file")
|
