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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
       distinct 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
              table).

       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
       usability, 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,
       mailbox 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
       directory 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
       service 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
              configuration 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)