zeroinstall/injector/trust.py

   1 """
   2 Records who we trust to sign feeds.
   3
   4 Trust is divided up into domains, so that it is possible to trust a key
   5 in some cases and not others.
   6
   7 @var trust_db: Singleton trust database instance.
   8 """
   9
  10 # Copyright (C) 2009, Thomas Leonard
  11 # See the README file for details, or visit http://0install.net.
  12
  13 from zeroinstall import _, SafeException
  14 import os
  15 from logging import info
  16
  17 from zeroinstall.support import basedir, tasks
  18 from .namespaces import config_site, config_prog, XMLNS_TRUST
  19
  20 KEY_INFO_TIMEOUT = 10   # Maximum time to wait for response from key-info-server
  21
  22 class TrustDB(object):
  23         """A database of trusted keys.
  24         @ivar keys: maps trusted key fingerprints to a set of domains for which where it is trusted
  25         @type keys: {str: set(str)}
  26         @ivar watchers: callbacks invoked by L{notify}
  27         @see: L{trust_db} - the singleton instance of this class"""
  28         __slots__ = ['keys', 'watchers']
  29
  30         def __init__(self):
  31                 self.keys = None
  32                 self.watchers = []
  33
  34         def is_trusted(self, fingerprint, domain = None):
  35                 self.ensure_uptodate()
  36
  37                 domains = self.keys.get(fingerprint, None)
  38                 if not domains: return False    # Unknown key
  39
  40                 if domain is None:
  41                         return True             # Deprecated
  42
  43                 return domain in domains or '*' in domains
  44
  45         def get_trust_domains(self, fingerprint):
  46                 """Return the set of domains in which this key is trusted.
  47                 If the list includes '*' then the key is trusted everywhere.
  48                 @since: 0.27
  49                 """
  50                 self.ensure_uptodate()
  51                 return self.keys.get(fingerprint, set())
  52
  53         def get_keys_for_domain(self, domain):
  54                 """Return the set of keys trusted for this domain.
  55                 @since: 0.27"""
  56                 self.ensure_uptodate()
  57                 return set([fp for fp in self.keys
  58                                  if domain in self.keys[fp]])
  59
  60         def trust_key(self, fingerprint, domain = '*'):
  61                 """Add key to the list of trusted fingerprints.
  62                 @param fingerprint: base 16 fingerprint without any spaces
  63                 @type fingerprint: str
  64                 @param domain: domain in which key is to be trusted
  65                 @type domain: str
  66                 @note: call L{notify} after trusting one or more new keys"""
  67                 if self.is_trusted(fingerprint, domain): return
  68
  69                 int(fingerprint, 16)            # Ensure fingerprint is valid
  70
  71                 if fingerprint not in self.keys:
  72                         self.keys[fingerprint] = set()
  73
  74                 #if domain == '*':
  75                 #       warn("Calling trust_key() without a domain is deprecated")
  76
  77                 self.keys[fingerprint].add(domain)
  78                 self.save()
  79
  80         def untrust_key(self, key, domain = '*'):
  81                 self.ensure_uptodate()
  82                 self.keys[key].remove(domain)
  83
  84                 if not self.keys[key]:
  85                         # No more domains for this key
  86                         del self.keys[key]
  87
  88                 self.save()
  89
  90         def save(self):
  91                 from xml.dom import minidom
  92                 import tempfile
  93
  94                 doc = minidom.Document()
  95                 root = doc.createElementNS(XMLNS_TRUST, 'trusted-keys')
  96                 root.setAttribute('xmlns', XMLNS_TRUST)
  97                 doc.appendChild(root)
  98
  99                 for fingerprint in self.keys:
 100                         keyelem = doc.createElementNS(XMLNS_TRUST, 'key')
 101                         root.appendChild(keyelem)
 102                         keyelem.setAttribute('fingerprint', fingerprint)
 103                         for domain in self.keys[fingerprint]:
 104                                 domainelem = doc.createElementNS(XMLNS_TRUST, 'domain')
 105                                 domainelem.setAttribute('value', domain)
 106                                 keyelem.appendChild(domainelem)
 107
 108                 d = basedir.save_config_path(config_site, config_prog)
 109                 fd, tmpname = tempfile.mkstemp(dir = d, prefix = 'trust-')
 110                 tmp = os.fdopen(fd, 'wb')
 111                 doc.writexml(tmp, indent = "", addindent = "  ", newl = "\n")
 112                 tmp.close()
 113
 114                 try:
 115                         os.rename(tmpname, os.path.join(d, 'trustdb.xml'))
 116                 except OSError:
 117                         #Fix for rename operation not working in windows if file dest exists
 118                         try:
 119                                 os.unlink(os.path.join(d, 'trustdb.xml.bak'))
 120                         except OSError:
 121                                 pass
 122                         os.rename(os.path.join(d, 'trustdb.xml'), os.path.join(d, 'trustdb.xml.bak'))
 123                         os.rename(tmpname, os.path.join(d, 'trustdb.xml'))
 124
 125         def notify(self):
 126                 """Call all watcher callbacks.
 127                 This should be called after trusting or untrusting one or more new keys.
 128                 @since: 0.25"""
 129                 for w in self.watchers: w()
 130
 131         def ensure_uptodate(self):
 132                 from xml.dom import minidom
 133
 134                 # This is a bit inefficient... (could cache things)
 135                 self.keys = {}
 136
 137                 trust = basedir.load_first_config(config_site, config_prog, 'trustdb.xml')
 138                 if trust:
 139                         keys = minidom.parse(trust).documentElement
 140                         for key in keys.getElementsByTagNameNS(XMLNS_TRUST, 'key'):
 141                                 domains = set()
 142                                 self.keys[key.getAttribute('fingerprint')] = domains
 143                                 for domain in key.getElementsByTagNameNS(XMLNS_TRUST, 'domain'):
 144                                         domains.add(domain.getAttribute('value'))
 145                 else:
 146                         # Convert old database to XML format
 147                         trust = basedir.load_first_config(config_site, config_prog, 'trust')
 148                         if trust:
 149                                 #print "Loading trust from", trust_db
 150                                 for key in file(trust).read().split('\n'):
 151                                         if key:
 152                                                 self.keys[key] = set(['*'])
 153                         else:
 154                                 # No trust database found.
 155                                 # Trust Thomas Leonard's key for 0install.net by default.
 156                                 # Avoids distracting confirmation box on first run when we check
 157                                 # for updates to the GUI.
 158                                 self.keys['92429807C9853C0744A68B9AAE07828059A53CC1'] = set(['0install.net'])
 159
 160 def domain_from_url(url):
 161         """Extract the trust domain for a URL.
 162         @param url: the feed's URL
 163         @type url: str
 164         @return: the trust domain
 165         @rtype: str
 166         @since: 0.27
 167         @raise SafeException: the URL can't be parsed"""
 168         import urlparse
 169         if os.path.isabs(url):
 170                 raise SafeException(_("Can't get domain from a local path: '%s'") % url)
 171         domain = urlparse.urlparse(url)[1]
 172         if domain and domain != '*':
 173                 return domain
 174         raise SafeException(_("Can't extract domain from URL '%s'") % url)
 175
 176 trust_db = TrustDB()
 177
 178 class TrustMgr(object):
 179         """A TrustMgr handles the process of deciding whether to trust new keys
 180         (contacting the key information server, prompting the user, accepting automatically, etc)
 181         @since: 0.53"""
 182
 183         __slots__ = ['config', '_current_confirm']
 184
 185         def __init__(self, config):
 186                 self.config = config
 187                 self._current_confirm = None    # (a lock to prevent asking the user multiple questions at once)
 188
 189         @tasks.async
 190         def confirm_keys(self, pending):
 191                 """We don't trust any of the signatures yet. Collect information about them and add the keys to the
 192                 trusted list, possibly after confirming with the user (via config.handler).
 193                 Updates the L{trust} database, and then calls L{trust.TrustDB.notify}.
 194                 @since: 0.53
 195                 @arg pending: an object holding details of the updated feed
 196                 @type pending: L{PendingFeed}
 197                 @return: A blocker that triggers when the user has chosen, or None if already done.
 198                 @rtype: None | L{Blocker}"""
 199
 200                 assert pending.sigs
 201
 202                 from zeroinstall.injector import gpg
 203                 valid_sigs = [s for s in pending.sigs if isinstance(s, gpg.ValidSig)]
 204                 if not valid_sigs:
 205                         def format_sig(sig):
 206                                 msg = str(sig)
 207                                 if sig.messages:
 208                                         msg += "\nMessages from GPG:\n" + sig.messages
 209                                 return msg
 210                         raise SafeException(_('No valid signatures found on "%(url)s". Signatures:%(signatures)s') %
 211                                         {'url': pending.url, 'signatures': ''.join(['\n- ' + format_sig(s) for s in pending.sigs])})
 212
 213                 # Start downloading information about the keys...
 214                 fetcher = self.config.fetcher
 215                 kfs = {}
 216                 for sig in valid_sigs:
 217                         kfs[sig] = fetcher.fetch_key_info(sig.fingerprint)
 218
 219                 # Wait up to KEY_INFO_TIMEOUT seconds for key information to arrive. Avoids having the dialog
 220                 # box update while the user is looking at it, and may allow it to be skipped completely in some
 221                 # cases.
 222                 timeout = tasks.TimeoutBlocker(KEY_INFO_TIMEOUT, "key info timeout")
 223                 while True:
 224                         key_info_blockers = [sig_info.blocker for sig_info in kfs.values() if sig_info.blocker is not None]
 225                         if not key_info_blockers:
 226                                 break
 227                         info("Waiting for response from key-info server: %s", key_info_blockers)
 228                         yield [timeout] + key_info_blockers
 229                         if timeout.happened:
 230                                 info("Timeout waiting for key info response")
 231                                 break
 232
 233                 # If we're already confirming something else, wait for that to finish...
 234                 while self._current_confirm is not None:
 235                         info("Waiting for previous key confirmations to finish")
 236                         yield self._current_confirm
 237
 238                 # Check whether we still need to confirm. The user may have
 239                 # already approved one of the keys while dealing with another
 240                 # feed.
 241                 domain = domain_from_url(pending.url)
 242                 for sig in kfs:
 243                         is_trusted = trust_db.is_trusted(sig.fingerprint, domain)
 244                         if is_trusted:
 245                                 return
 246
 247                 # Take the lock and confirm this feed
 248                 self._current_confirm = lock = tasks.Blocker('confirm key lock')
 249                 try:
 250                         done = self.config.handler.confirm_import_feed(pending, kfs)
 251                         if done is not None:
 252                                 yield done
 253                                 tasks.check(done)
 254                 finally:
 255                         self._current_confirm = None
 256                         lock.trigger()