TLSMGR(8postfix)

📦 version 3.8.6, in debian bookworm, ubuntu jammy, ubuntu noble

💖 TLSMGR — the Postfix TLS session cache + PRNG manager 💖

okay so bestie, this page is tlsmgr(8postfix) from the Postfix manuals, and it's literally the backstage crew keeping your TLS sessions and your random numbers cute and functional. let's get into it ✨

🌸 SYNOPSIS 🌸

tlsmgr [generic Postfix daemon options]

🦋 DESCRIPTION 🦋

so tlsmgr(8) manages the Postfix TLS session caches. she stores and retrieves cache entries whenever smtpd(8) and smtp(8) processes ask for them, and periodically she goes through and removes entries that have expired. no hoarding allowed 💅

she also manages the PRNG (pseudo random number generator) pool. she answers queries from the smtpd(8) and smtp(8) processes so they can seed their own internal PRNG pools. it's giving generous queen behavior, fr fr.

the tlsmgr(8)'s PRNG pool gets initially seeded from an external source (EGD, /dev/urandom, or a regular file). it's updated at configurable pseudo-random intervals with data from the external source. it's also updated periodically with data from TLS session cache entries and with the time of day, and it gets updated with the time of day whenever a process requests tlsmgr(8) service. busy busy busy ✨

the tlsmgr(8) saves the PRNG state to an exchange file periodically and when the process terminates, and reads the exchange file when initializing its PRNG. so she always remembers where she left off, iconic 🎀

🔒 SECURITY 🔒

the tlsmgr(8) is not security-sensitive. the code that maintains the external and internal PRNG pools does not "trust" the data that it manipulates, and the code that maintains the TLS session cache does not touch the contents of the cached entries — except for seeding its internal PRNG pool. so like, she minds her own business 🫶

the tlsmgr(8) can be run chrooted and with reduced privileges. at process startup it connects to the entropy source and exchange file, and creates or truncates the optional TLS session cache files.

with Postfix version 2.5 and later, the tlsmgr(8) no longer uses root privileges when opening cache files. these files should now be stored under the Postfix-owned data_directory. as a migration aid, an attempt to open a cache file under a non-Postfix directory is redirected to the Postfix-owned data_directory, and a warning is logged. the vibes are: glow up, move your files 💅

🩺 DIAGNOSTICS 🩺

problems and transactions are logged to syslogd(8) or postlogd(8). she's not secretive, she journals 🌸

💀 BUGS 💀

there is no automatic means to limit the number of entries in the TLS session caches and/or the size of the TLS cache files. so they can just... grow. no cap. watch them 😭

⚙️ CONFIGURATION PARAMETERS ⚙️

changes to main.cf are not picked up automatically, because tlsmgr(8) is a persistent process. use the command postfix reload after a configuration change. that's the whole move, bestie.

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

🎀 TLS SESSION CACHE 🎀

  • lmtp_tls_loglevel (0) — the LMTP-specific version of the smtp_tls_loglevel configuration parameter.
  • lmtp_tls_session_cache_database (empty) — the LMTP-specific version of the smtp_tls_session_cache_database configuration parameter.
  • lmtp_tls_session_cache_timeout (3600s) — the LMTP-specific version of the smtp_tls_session_cache_timeout configuration parameter.
  • smtp_tls_loglevel (0) — enable additional Postfix SMTP client logging of TLS activity.
  • smtp_tls_session_cache_database (empty) — name of the file containing the optional Postfix SMTP client TLS session cache.
  • smtp_tls_session_cache_timeout (3600s) — the expiration time of Postfix SMTP client TLS session cache information.
  • smtpd_tls_loglevel (0) — enable additional Postfix SMTP server logging of TLS activity.
  • smtpd_tls_session_cache_database (empty) — name of the file containing the optional Postfix SMTP server TLS session cache.
  • smtpd_tls_session_cache_timeout (3600s) — the expiration time of Postfix SMTP server TLS session cache information.

🎲 PSEUDO RANDOM NUMBER GENERATOR 🎲

  • tls_random_source (see 'postconf -d' output) — the external entropy source for the in-memory tlsmgr(8) pseudo random number generator (PRNG) pool.
  • tls_random_bytes (32) — the number of bytes that tlsmgr(8) reads from $tls_random_source when (re)seeding the in-memory pseudo random number generator (PRNG) pool.
  • tls_random_exchange_name (see 'postconf -d' output) — name of the pseudo random number generator (PRNG) state file that is maintained by tlsmgr(8).
  • tls_random_prng_update_period (3600s) — the time between attempts by tlsmgr(8) to save the state of the pseudo random number generator (PRNG) to the file specified with $tls_random_exchange_name.
  • tls_random_reseed_period (3600s) — the maximal time between attempts by tlsmgr(8) to re-seed the in-memory pseudo random number generator (PRNG) pool from external sources.

🧚 MISCELLANEOUS CONTROLS 🧚

  • 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.
  • 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.
  • syslog_facility (mail) — the syslog facility of Postfix logging.
  • syslog_name (see 'postconf -d' output) — a prefix that is prepended to the process name in syslog records, so that, for example, "smtpd" becomes "prefix/smtpd".

available in Postfix 3.3 and later:

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

👀 SEE ALSO 👀

📚 README FILES 📚

use "postconf readme_directory" or "postconf html_directory" to locate this information.

  • TLS_README, Postfix TLS configuration and operation

📜 LICENSE 📜

the Secure Mailer license must be distributed with this software. periodt.

🕰️ HISTORY 🕰️

this service was introduced with Postfix version 2.2. a legend from day one 👑

👑 AUTHOR(S) 👑

Lutz Jaenicke BTU Cottbus Allgemeine Elektrotechnik Universitaetsplatz 3-4 D-03044 Cottbus, Germany

adapted by:

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

and that's the whole page bestie 💖 this was TLSMGR(8postfix) — the Postfix manual page for the TLS session cache and PRNG manager — go forth and cache responsibly, mwah 🎀✨

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