PROXYMAP(8)		    System Manager's Manual		   PROXYMAP(8)



NAME
       proxymap - Postfix lookup table proxy server

SYNOPSIS
       proxymap [generic Postfix daemon options]

DESCRIPTION
       The  proxymap(8)	 server	 provides read-only or read-write table lookup
       service to Postfix processes. These services are implemented with  dis-
       tinct service names: proxymap and proxywrite, respectively. The purpose
       of these services is:

       o      To overcome chroot restrictions. For example,  a	chrooted  SMTP
	      server needs access to the system passwd file in order to reject
	      mail for non-existent local addresses, but it is	not  practical
	      to  maintain  a copy of the passwd file in the chroot jail.  The
	      solution:

	      local_recipient_maps =
		  proxy:unix:passwd.byname $alias_maps

       o      To consolidate the number of open lookup tables by  sharing  one
	      open  table  among multiple processes. For example, making mysql
	      connections from every Postfix daemon process  results  in  "too
	      many connections" errors. The solution:

	      virtual_alias_maps =
		  proxy:mysql:/etc/postfix/virtual_alias.cf

	      The  total  number  of  connections  is limited by the number of
	      proxymap server processes.

       o      To provide single-updater functionality for lookup  tables  that
	      do  not  reliably	 support multiple writers (i.e. all file-based
	      tables).

       The proxymap(8) server implements the following requests:

       open maptype:mapname flags
	      Open the table with type maptype and name mapname, as controlled
	      by  flags.  The  reply  includes the maptype dependent flags (to
	      distinguish a fixed string table from a regular  expression  ta-
	      ble).

       lookup maptype:mapname flags key
	      Look  up	the data stored under the requested key.  The reply is
	      the request completion status code and the lookup result	value.
	      The  maptype:mapname  and	 flags	are  the same as with the open
	      request.

       update maptype:mapname flags key value
	      Update the data stored under the requested key.	The  reply  is
	      the  request  completion	status	code.  The maptype:mapname and
	      flags are the same as with the open request.

	      To implement single-updater maps, specify a process limit	 of  1
	      in the master.cf file entry for the proxywrite service.

	      This request is supported in Postfix 2.5 and later.

       delete maptype:mapname flags key
	      Delete  the  data	 stored under the requested key.  The reply is
	      the request completion status  code.   The  maptype:mapname  and
	      flags are the same as with the open request.

	      This request is supported in Postfix 2.5 and later.

       The request completion status is one of OK, RETRY, NOKEY (lookup failed
       because the key was not found), BAD (malformed request)	or  DENY  (the
       table is not approved for proxy read or update access).

       There  is  no  close  command,  nor are tables implicitly closed when a
       client disconnects. The purpose	is  to	share  tables  among  multiple
       client processes.

SERVER PROCESS MANAGEMENT
       proxymap(8)  servers run under control by the Postfix master(8) server.
       Each server can handle multiple	simultaneous  connections.   When  all
       servers	are  busy while a client connects, the master(8) creates a new
       proxymap(8) server process, provided that  the  process	limit  is  not
       exceeded.   Each	 server	 terminates  after  serving  at least $max_use
       clients or after $max_idle seconds of idle time.

SECURITY
       The proxymap(8) server opens only tables	 that  are  approved  via  the
       proxy_read_maps	or proxy_write_maps configuration parameters, does not
       talk to users, and can run at fixed low	privilege,  chrooted  or  not.
       However,	 running  the proxymap server chrooted severely limits usabil-
       ity, because it can open only chrooted tables.

       The proxymap(8) server is not a trusted daemon process, and must not be
       used  to look up sensitive information such as user or group IDs, mail-
       box file/directory names or external commands.

       In Postfix version  2.2	and  later,  the  proxymap  client  recognizes
       requests	 to  access a table for security-sensitive purposes, and opens
       the table directly. This allows the same main.cf setting to be used  by
       sensitive and non-sensitive processes.

       Postfix-writable	 data  files should be stored under a dedicated direc-
       tory that is writable only by the Postfix  mail	system,	 such  as  the
       Postfix-owned data_directory.

       In  particular, Postfix-writable files should never exist in root-owned
       directories. That would open up a  particular  type  of	security  hole
       where  ownership	 of a file or directory does not match the provider of
       its content.

DIAGNOSTICS
       Problems and transactions are logged to syslogd(8).

BUGS
       The proxymap(8) server provides service to multiple clients,  and  must
       therefore not be used for tables that have high-latency lookups.

       The  proxymap(8)	 read-write  service  does not explicitly close lookup
       tables (even if it did, this  could  not	 be  relied  on,  because  the
       process	may be terminated between table updates).  The read-write ser-
       vice should therefore not be used with  tables  that  leave  persistent
       storage	in  an	inconsistent state between updates (for example, CDB).
       Tables that support "sync on  update"  should  be  safe	(for  example,
       Berkeley DB) as should tables that are implemented by a real DBMS.

CONFIGURATION PARAMETERS
       On  busy	 mail systems a long time may pass before proxymap(8) relevant
       changes to main.cf are picked up. Use the command "postfix  reload"  to
       speed up a change.

       The  text  below provides only a parameter summary. See postconf(5) for
       more details including examples.

       config_directory (see 'postconf -d' output)
	      The default location of the Postfix main.cf and  master.cf  con-
	      figuration files.

       data_directory (see 'postconf -d' output)
	      The  directory  with  Postfix-writable  data files (for example:
	      caches, pseudo-random numbers).

       daemon_timeout (18000s)
	      How much time a Postfix daemon process  may  take	 to  handle  a
	      request before it is terminated by a built-in watchdog timer.

       ipc_timeout (3600s)
	      The  time	 limit	for  sending  or receiving information over an
	      internal communication channel.

       max_idle (100s)
	      The maximum amount of time that an idle Postfix  daemon  process
	      waits for an incoming connection before terminating voluntarily.

       max_use (100)
	      The maximal number of incoming connections that a Postfix daemon
	      process will service before terminating voluntarily.

       process_id (read-only)
	      The process ID of a Postfix command or daemon process.

       process_name (read-only)
	      The process name of a Postfix command or daemon process.

       proxy_read_maps (see 'postconf -d' output)
	      The lookup tables that the  proxymap(8)  server  is  allowed  to
	      access for the read-only service.

       Available in Postfix 2.5 and later:

       data_directory (see 'postconf -d' output)
	      The  directory  with  Postfix-writable  data files (for example:
	      caches, pseudo-random numbers).

       proxy_write_maps (see 'postconf -d' output)
	      The lookup tables that the  proxymap(8)  server  is  allowed  to
	      access for the read-write service.

SEE ALSO
       postconf(5), configuration parameters
       master(5), generic daemon options

README FILES
       Use  "postconf readme_directory" or "postconf html_directory" to locate
       this information.
       DATABASE_README, Postfix lookup table overview

LICENSE
       The Secure Mailer license must be distributed with this software.

HISTORY
       The proxymap service was introduced with Postfix 2.0.

AUTHOR(S)
       Wietse Venema
       IBM T.J. Watson Research
       P.O. Box 704
       Yorktown Heights, NY 10598, USA



								   PROXYMAP(8)