Ubuntu Manpage: proxymap - Postfix lookup table proxy server

Provided by: postfix_3.3.0-1ubuntu0.4_amd64

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:

• 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

• 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.

• 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.

sequence maptype:mapname flags function
Iterate over the specified database. The function is one of DICT_SEQ_FUN_FIRST or
DICT_SEQ_FUN_NEXT. The reply is the request completion status code and a lookup key and result
value, if found.

This request is supported in Postfix 2.9 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 UNIX 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.

       Available in Postfix 3.3 and later:

       service_name (read-only)
              The master.cf service name of a Postfix daemon process.

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

       Wietse Venema
       Google, Inc.
       111 8th Avenue
       New York, NY 10011, USA

                                                                                              PROXYMAP(8postfix)