PROXYMAP(8)                                                        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)

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