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 subprocess
   9 import tempfile
  10 import types
  11 import urllib.parse
  12 import urllib.request
  13 import xml.dom.minidom
  14
  15 from typing import (
  16     Dict,
  17     Iterable,
  18     List,
  19     NewType,
  20     Sequence,
  21     Tuple,
  22 )
  23
  24 Digest16 = NewType('Digest16', str)
  25 Digest32 = NewType('Digest32', str)
  26
  27
  28 class InfoTableEntry(types.SimpleNamespace):
  29     digest: Digest16
  30     file: str
  31     size: int
  32     url: str
  33
  34
  35 class Info(types.SimpleNamespace):
  36     channel_html: bytes
  37     forwarded_url: str
  38     git_revision: str
  39     table: Dict[str, InfoTableEntry]
  40     url: str
  41
  42
  43 class VerificationError(Exception):
  44     pass
  45
  46
  47 class Verification:
  48
  49     def __init__(self) -> None:
  50         self.line_length = 0
  51
  52     def status(self, s: str) -> None:
  53         print(s, end=' ', flush=True)
  54         self.line_length += 1 + len(s)  # Unicode??
  55
  56     @staticmethod
  57     def _color(s: str, c: int) -> str:
  58         return '\033[%2dm%s\033[00m' % (c, s)
  59
  60     def result(self, r: bool) -> None:
  61         message, color = {True: ('OK ', 92), False: ('FAIL', 91)}[r]
  62         length = len(message)
  63         cols = shutil.get_terminal_size().columns
  64         pad = (cols - (self.line_length + length)) % cols
  65         print(' ' * pad + self._color(message, color))
  66         self.line_length = 0
  67         if not r:
  68             raise VerificationError()
  69
  70     def check(self, s: str, r: bool) -> None:
  71         self.status(s)
  72         self.result(r)
  73
  74     def ok(self) -> None:
  75         self.result(True)
  76
  77
  78 def compare(a: str,
  79             b: str) -> Tuple[Sequence[str],
  80                              Sequence[str],
  81                              Sequence[str]]:
  82
  83     def throw(error: OSError) -> None:
  84         raise error
  85
  86     def join(x: str, y: str) -> str:
  87         return y if x == '.' else os.path.join(x, y)
  88
  89     def recursive_files(d: str) -> Iterable[str]:
  90         all_files: List[str] = []
  91         for path, dirs, files in os.walk(d, onerror=throw):
  92             rel = os.path.relpath(path, start=d)
  93             all_files.extend(join(rel, f) for f in files)
  94             for dir_or_link in dirs:
  95                 if os.path.islink(join(path, dir_or_link)):
  96                     all_files.append(join(rel, dir_or_link))
  97         return all_files
  98
  99     def exclude_dot_git(files: Iterable[str]) -> Iterable[str]:
 100         return (f for f in files if not f.startswith('.git/'))
 101
 102     files = functools.reduce(
 103         operator.or_, (set(
 104             exclude_dot_git(
 105                 recursive_files(x))) for x in [a, b]))
 106     return filecmp.cmpfiles(a, b, files, shallow=False)
 107
 108
 109 def fetch(v: Verification, channel_url: str) -> Info:
 110     info = Info()
 111     info.url = channel_url
 112     v.status('Fetching channel')
 113     request = urllib.request.urlopen(
 114         'https://channels.nixos.org/nixos-20.03', timeout=10)
 115     info.channel_html = request.read()
 116     info.forwarded_url = request.geturl()
 117     v.result(request.status == 200)
 118     v.check('Got forwarded', info.url != info.forwarded_url)
 119     return info
 120
 121
 122 def parse_table(v: Verification, info: Info) -> None:
 123     v.status('Parsing channel description as XML')
 124     d = xml.dom.minidom.parseString(info.channel_html)
 125     v.ok()
 126
 127     v.status('Extracting git commit')
 128     git_commit_node = d.getElementsByTagName('tt')[0]
 129     info.git_commit = git_commit_node.firstChild.nodeValue
 130     v.ok()
 131     v.status('Verifying git commit label')
 132     v.result(git_commit_node.previousSibling.nodeValue == 'Git commit ')
 133
 134     v.status('Parsing table')
 135     info.table = {}
 136     for row in d.getElementsByTagName('tr')[1:]:
 137         name = row.childNodes[0].firstChild.firstChild.nodeValue
 138         url = row.childNodes[0].firstChild.getAttribute('href')
 139         size = int(row.childNodes[1].firstChild.nodeValue)
 140         digest = Digest16(row.childNodes[2].firstChild.firstChild.nodeValue)
 141         info.table[name] = InfoTableEntry(url=url, digest=digest, size=size)
 142     v.ok()
 143
 144
 145 def digest_file(filename: str) -> Digest16:
 146     hasher = hashlib.sha256()
 147     with open(filename, 'rb') as f:
 148         # pylint: disable=cell-var-from-loop
 149         for block in iter(lambda: f.read(4096), b''):
 150             hasher.update(block)
 151     return Digest16(hasher.hexdigest())
 152
 153
 154 def to_Digest16(v: Verification, digest32: Digest32) -> Digest16:
 155     v.status('Converting digest to base16')
 156     process = subprocess.run(
 157         ['nix', 'to-base16', '--type', 'sha256', digest32], capture_output=True)
 158     v.result(process.returncode == 0)
 159     return Digest16(process.stdout.decode().strip())
 160
 161
 162 def to_Digest32(v: Verification, digest16: Digest16) -> Digest32:
 163     v.status('Converting digest to base32')
 164     process = subprocess.run(
 165         ['nix', 'to-base32', '--type', 'sha256', digest16], capture_output=True)
 166     v.result(process.returncode == 0)
 167     return Digest32(process.stdout.decode().strip())
 168
 169
 170 def fetch_with_nix_prefetch_url(
 171         v: Verification,
 172         url: str,
 173         digest: Digest16) -> str:
 174     v.status('Fetching %s' % url)
 175     process = subprocess.run(
 176         ['nix-prefetch-url', '--print-path', url, digest], capture_output=True)
 177     v.result(process.returncode == 0)
 178     prefetch_digest, path, empty = process.stdout.decode().split('\n')
 179     assert empty == ''
 180     v.check("Verifying nix-prefetch-url's digest",
 181             to_Digest16(v, Digest32(prefetch_digest)) == digest)
 182     v.status("Verifying file digest")
 183     file_digest = digest_file(path)
 184     v.result(file_digest == digest)
 185     return path
 186
 187
 188 def fetch_resources(v: Verification, info: Info) -> None:
 189     for resource in ['git-revision', 'nixexprs.tar.xz']:
 190         fields = info.table[resource]
 191         url = urllib.parse.urljoin(info.forwarded_url, fields.url)
 192         fields.file = fetch_with_nix_prefetch_url(v, url, fields.digest)
 193     v.status('Verifying git commit on main page matches git commit in table')
 194     v.result(
 195         open(
 196             info.table['git-revision'].file).read(999) == info.git_commit)
 197
 198
 199 def extract_channel(v: Verification, info: Info) -> None:
 200     with tempfile.TemporaryDirectory() as d:
 201         v.status('Extracting nixexprs.tar.xz')
 202         shutil.unpack_archive(info.table['nixexprs.tar.xz'].file, d)
 203         v.ok()
 204         v.status('Removing temporary directory')
 205     v.ok()
 206
 207
 208 def main() -> None:
 209     v = Verification()
 210     info = fetch(v, 'https://channels.nixos.org/nixos-20.03')
 211     parse_table(v, info)
 212     fetch_resources(v, info)
 213     extract_channel(v, info)
 214     print(info)
 215
 216
 217 main()