git.scottworley.com Git - pinch/blob - pinch.py

   1 import filecmp
   2 import functools
   3 import hashlib
   4 import operator
   5 import os
   6 import os.path
   7 import shutil
   8 import tempfile
   9 import types
  10 import urllib.parse
  11 import urllib.request
  12 import xml.dom.minidom
  13
  14 from typing import (
  15     Dict,
  16     Iterable,
  17     List,
  18     Sequence,
  19     Tuple,
  20 )
  21
  22
  23 class InfoTableEntry(types.SimpleNamespace):
  24     content: bytes
  25     digest: str
  26     file: str
  27     size: int
  28     url: str
  29
  30
  31 class Info(types.SimpleNamespace):
  32     channel_html: bytes
  33     forwarded_url: str
  34     git_revision: str
  35     table: Dict[str, InfoTableEntry]
  36     url: str
  37
  38
  39 class VerificationError(Exception):
  40     pass
  41
  42
  43 class Verification:
  44
  45     def __init__(self) -> None:
  46         self.line_length = 0
  47
  48     def status(self, s: str) -> None:
  49         print(s, end=' ', flush=True)
  50         self.line_length += 1 + len(s)  # Unicode??
  51
  52     @staticmethod
  53     def _color(s: str, c: int) -> str:
  54         return '\033[%2dm%s\033[00m' % (c, s)
  55
  56     def result(self, r: bool) -> None:
  57         message, color = {True: ('OK ', 92), False: ('FAIL', 91)}[r]
  58         length = len(message)
  59         cols = shutil.get_terminal_size().columns
  60         pad = (cols - (self.line_length + length)) % cols
  61         print(' ' * pad + self._color(message, color))
  62         self.line_length = 0
  63         if not r:
  64             raise VerificationError()
  65
  66     def check(self, s: str, r: bool) -> None:
  67         self.status(s)
  68         self.result(r)
  69
  70     def ok(self) -> None:
  71         self.result(True)
  72
  73
  74 def compare(a: str,
  75             b: str) -> Tuple[Sequence[str],
  76                              Sequence[str],
  77                              Sequence[str]]:
  78
  79     def throw(error: OSError) -> None:
  80         raise error
  81
  82     def join(x: str, y: str) -> str:
  83         return y if x == '.' else os.path.join(x, y)
  84
  85     def recursive_files(d: str) -> Iterable[str]:
  86         all_files: List[str] = []
  87         for path, dirs, files in os.walk(d, onerror=throw):
  88             rel = os.path.relpath(path, start=d)
  89             all_files.extend(join(rel, f) for f in files)
  90             for dir_or_link in dirs:
  91                 if os.path.islink(join(path, dir_or_link)):
  92                     all_files.append(join(rel, dir_or_link))
  93         return all_files
  94
  95     def exclude_dot_git(files: Iterable[str]) -> Iterable[str]:
  96         return (f for f in files if not f.startswith('.git/'))
  97
  98     files = functools.reduce(
  99         operator.or_, (set(
 100             exclude_dot_git(
 101                 recursive_files(x))) for x in [a, b]))
 102     return filecmp.cmpfiles(a, b, files, shallow=False)
 103
 104
 105 def fetch(v: Verification, channel_url: str) -> Info:
 106     info = Info()
 107     info.url = channel_url
 108     v.status('Fetching channel')
 109     request = urllib.request.urlopen(
 110         'https://channels.nixos.org/nixos-20.03', timeout=10)
 111     info.channel_html = request.read()
 112     info.forwarded_url = request.geturl()
 113     v.result(request.status == 200)
 114     v.check('Got forwarded', info.url != info.forwarded_url)
 115     return info
 116
 117
 118 def parse(v: Verification, info: Info) -> None:
 119     v.status('Parsing channel description as XML')
 120     d = xml.dom.minidom.parseString(info.channel_html)
 121     v.ok()
 122
 123     v.status('Extracting git commit')
 124     git_commit_node = d.getElementsByTagName('tt')[0]
 125     info.git_commit = git_commit_node.firstChild.nodeValue
 126     v.ok()
 127     v.status('Verifying git commit label')
 128     v.result(git_commit_node.previousSibling.nodeValue == 'Git commit ')
 129
 130     v.status('Parsing table')
 131     info.table = {}
 132     for row in d.getElementsByTagName('tr')[1:]:
 133         name = row.childNodes[0].firstChild.firstChild.nodeValue
 134         url = row.childNodes[0].firstChild.getAttribute('href')
 135         size = int(row.childNodes[1].firstChild.nodeValue)
 136         digest = row.childNodes[2].firstChild.firstChild.nodeValue
 137         info.table[name] = InfoTableEntry(url=url, digest=digest, size=size)
 138     v.ok()
 139
 140
 141 def fetch_resources(v: Verification, info: Info) -> None:
 142
 143     for resource in ['git-revision', 'nixexprs.tar.xz']:
 144         fields = info.table[resource]
 145         v.status('Fetching resource "%s"' % resource)
 146         url = urllib.parse.urljoin(info.forwarded_url, fields.url)
 147         request = urllib.request.urlopen(url, timeout=10)
 148         if fields.size < 4096:
 149             fields.content = request.read()
 150         else:
 151             with tempfile.NamedTemporaryFile(suffix='.nixexprs.tar.xz', delete=False) as tmp_file:
 152                 shutil.copyfileobj(request, tmp_file)
 153                 fields.file = tmp_file.name
 154         v.result(request.status == 200)
 155         v.status('Verifying digest for "%s"' % resource)
 156         if fields.size < 4096:
 157             actual_hash = hashlib.sha256(fields.content).hexdigest()
 158         else:
 159             hasher = hashlib.sha256()
 160             with open(fields.file, 'rb') as f:
 161                 # pylint: disable=cell-var-from-loop
 162                 for block in iter(lambda: f.read(4096), b''):
 163                     hasher.update(block)
 164             actual_hash = hasher.hexdigest()
 165         v.result(actual_hash == fields.digest)
 166     v.check('Verifying git commit on main page matches git commit in table',
 167             info.table['git-revision'].content.decode() == info.git_commit)
 168
 169
 170 def extract_channel(v: Verification, info: Info) -> None:
 171     with tempfile.TemporaryDirectory() as d:
 172         v.status('Extracting nixexprs.tar.xz')
 173         shutil.unpack_archive(info.table['nixexprs.tar.xz'].file, d)
 174         v.ok()
 175         v.status('Removing temporary directory')
 176     v.ok()
 177
 178
 179 def main() -> None:
 180     v = Verification()
 181     info = fetch(v, 'https://channels.nixos.org/nixos-20.03')
 182     parse(v, info)
 183     fetch_resources(v, info)
 184     extract_channel(v, info)
 185     print(info)
 186
 187
 188 main()