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