signing.py

   1 from zeroinstall import SafeException
   2 from zeroinstall.injector import gpg
   3 import tempfile, os, base64, sys, shutil
   4
   5 def check_signature(path):
   6         data = file(path).read()
   7         xml_comment = data.rfind('\n<!-- Base64 Signature')
   8         if xml_comment >= 0:
   9                 data_stream, sigs = gpg.check_stream(file(path))
  10                 sign_fn = sign_xml
  11                 data = data[:xml_comment + 1]
  12                 data_stream.close()
  13         elif data.startswith('-----BEGIN'):
  14                 data_stream, sigs = gpg.check_stream(file(path))
  15                 sign_fn = sign_plain
  16                 data = data_stream.read()
  17         else:
  18                 return data, sign_unsigned, None
  19         for sig in sigs:
  20                 if isinstance(sig, gpg.ValidSig):
  21                         return data, sign_fn, sig.fingerprint
  22         print "ERROR: No valid signatures found!"
  23         for sig in sigs:
  24                 print "Got:", sig
  25         ok = raw_input('Ignore and load anyway? (y/N) ').lower()
  26         if ok and 'yes'.startswith(ok):
  27                 import __main__
  28                 __main__.force_save = True
  29                 return data, sign_unsigned, None
  30         sys.exit(1)
  31
  32 def write_tmp(path, data):
  33         """Create a temporary file in the same directory as 'path' and write data to it."""
  34         fd, tmp = tempfile.mkstemp(prefix = 'tmp-', dir = os.path.dirname(path))
  35         stream = os.fdopen(fd, 'w')
  36         stream.write(data)
  37         stream.close()
  38         return tmp
  39
  40 def run_gpg(default_key, *arguments):
  41         arguments = list(arguments)
  42         if default_key is not None:
  43                 arguments = ['--default-key', default_key] + arguments
  44         arguments.insert(0, 'gpg')
  45         if os.spawnvp(os.P_WAIT, 'gpg', arguments):
  46                 raise SafeException("Command '%s' failed" % arguments)
  47
  48 def sign_unsigned(path, data, key):
  49         os.rename(write_tmp(path, data), path)
  50
  51 def sign_plain(path, data, key):
  52         tmp = write_tmp(path, data)
  53         try:
  54                 run_gpg(key, '--clearsign', tmp)
  55         finally:
  56                 os.unlink(tmp)
  57         os.rename(tmp + '.asc', path)
  58
  59 def sign_xml(path, data, key):
  60         tmp = write_tmp(path, data)
  61         try:
  62                 run_gpg(key, '--detach-sign', tmp)
  63         finally:
  64                 os.unlink(tmp)
  65         tmp += '.sig'
  66         encoded = base64.encodestring(file(tmp).read())
  67         os.unlink(tmp)
  68         sig = "<!-- Base64 Signature\n" + encoded + "\n-->\n"
  69         os.rename(write_tmp(path, data + sig), path)
  70
  71 def export_key(dir, fingerprint):
  72         assert fingerprint is not None
  73         # Convert fingerprint to key ID
  74         stream = os.popen('gpg --with-colons --list-keys %s' % fingerprint)
  75         try:
  76                 keyID = None
  77                 for line in stream:
  78                         parts = line.split(':')
  79                         if parts[0] == 'pub':
  80                                 if keyID:
  81                                         raise Exception('Two key IDs returned from GPG!')
  82                                 keyID = parts[4]
  83         finally:
  84                 stream.close()
  85         key_file = os.path.join(dir, keyID + '.gpg')
  86         if os.path.isfile(key_file):
  87                 return
  88         key_stream = file(key_file, 'w')
  89         stream = os.popen("gpg -a --export '%s'" % fingerprint)
  90         shutil.copyfileobj(stream, key_stream)
  91         stream.close()
  92         key_stream.close()
  93         print "Exported public key as '%s'" % key_file