mDNSMacOSX/README.privsep

   1 On Mac OS X, mDNSResponder now runs with user-ID and group-ID
   2 "_mdnsresponder". In order to perform certain privileged operations, a
   3 helper (unimagintively called mDNSResponderHelper) runs as root when
   4 needed and handles requests from mDNSResponder.
   5
   6
   7 * A new LaunchD job com.apple.mDNSResponderHelper starts
   8   mDNSResponderHelper on demand.  The helper exits after approximately
   9   10 seconds of idle time.
  10
  11 * The com.apple.mDNSResponder LaunchD job specifies the account under
  12   which to run, so that mDNSResponder starts as _mdnsresponder.
  13
  14 * A subdirectory named "mdns" and owned by _mdnsresponder has been
  15   created in /var/run.  The PID file and uDNS server socket has been
  16   moved to that subdirectory.
  17
  18 * There are currently six remote procedure calls handled by
  19   mDNSResponderHelper: mDNSPreferencesSetName, mDNSKeychainGetSecrets,
  20   mDNSConfigureServer, and mDNSAutoTunnelSetKeys
  21
  22 * mDNSPreferencesSetName allows mDNSResponder to set the computer name
  23   or local host name, and displays a notification if there was a
  24   conflict.
  25
  26 * mDNSKeychainGetSecrets causes mDNSResponderHelper to collect DNS
  27   keys from the system keychain.  SetDomainSecrets uses the result to
  28   populate AuthInfoList.  One could refactor this code further so that
  29   mDNSResponderHelper performs all the cryptographic operations, with
  30   the result that a compromise of mDNSResponder does not compromise
  31   keys.  But I think that may be more change than is advisable at this
  32   point.
  33
  34 * On the advice of the Security.framework team, I've used
  35   SecKeychainSetPreferenceDomain to ensure that the system keychain is
  36   references whenever a NULL SecKeychainRef is used.  Wherever a
  37   SecKeychainRef is needed, NULL is now specified.
  38
  39 * mDNSConfigureServer, and mDNSAutoTunnelSetKeys do various setup and
  40   teardown for BTMM.