Postfix manual - tlsproxy(8)

    TLSPROXY(8)                                                        TLSPROXY(8)

    NAME
           tlsproxy - Postfix TLS proxy

    SYNOPSIS
           tlsproxy [generic Postfix daemon options]

    DESCRIPTION
           The  tlsproxy(8)  server  implements a two-way TLS proxy. It is used by
           the postscreen(8) server to talk SMTP-over-TLS with remote SMTP clients
           that  are not allowlisted (including clients whose allowlist status has
           expired), and by the smtp(8) client to support  TLS  connection  reuse,
           but it should also work for non-SMTP protocols.

           Although  one  tlsproxy(8)  process  can serve multiple sessions at the
           same time, it is a good idea  to  allow  the  number  of  processes  to
           increase with load, so that the service remains responsive.

    PROTOCOL EXAMPLE
           The  example  below  concerns  postscreen(8).  However, the tlsproxy(8)
           server is agnostic of the application protocol, and the example is eas-
           ily adapted to other applications.

           After  receiving  a  valid  remote  SMTP  client  STARTTLS command, the
           postscreen(8) server sends the remote SMTP client endpoint string,  the
           requested  role  (server),  and  the  requested timeout to tlsproxy(8).
           postscreen(8)  then  receives  a  "TLS   available"   indication   from
           tlsproxy(8).   If the TLS service is available, postscreen(8) sends the
           remote SMTP client file descriptor to tlsproxy(8), and sends the plain-
           text 220 greeting to the remote SMTP client.  This triggers TLS negoti-
           ations between the remote SMTP client and tlsproxy(8).  Upon completion
           of  the  TLS-level  handshake, tlsproxy(8) translates between plaintext
           from/to postscreen(8) and ciphertext to/from the remote SMTP client.

    SECURITY
           The tlsproxy(8) server is moderately security-sensitive.  It  talks  to
           untrusted  clients  on  the network. The process can be run chrooted at
           fixed low privilege.

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

    CONFIGURATION PARAMETERS
           Changes to main.cf are not picked up automatically, as tlsproxy(8) pro-
           cesses  may run for a long time depending on mail server load.  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.

    STARTTLS GLOBAL CONTROLS
           The  following settings are global and therefore cannot be overruled by
           information specified in a tlsproxy(8) client request.

           tls_append_default_CA (no)
                  Append the system-supplied default Certification Authority  cer-
                  tificates   to   the   ones   specified   with  *_tls_CApath  or
                  *_tls_CAfile.

           tls_daemon_random_bytes (32)
                  The number of pseudo-random bytes that an  smtp(8)  or  smtpd(8)
                  process  requests from the tlsmgr(8) server in order to seed its
                  internal pseudo random number generator (PRNG).

           tls_high_cipherlist (see 'postconf -d' output)
                  The OpenSSL cipherlist for "high" grade ciphers.

           tls_medium_cipherlist (see 'postconf -d' output)
                  The OpenSSL cipherlist for "medium" or higher grade ciphers.

           tls_null_cipherlist (eNULL:!aNULL)
                  The OpenSSL cipherlist for "NULL"  grade  ciphers  that  provide
                  authentication without encryption.

           tls_eecdh_strong_curve (prime256v1)
                  The  elliptic curve used by the Postfix SMTP server for sensibly
                  strong ephemeral ECDH key exchange.

           tls_eecdh_ultra_curve (secp384r1)
                  The elliptic curve used by the Postfix SMTP server for maximally
                  strong ephemeral ECDH key exchange.

           tls_disable_workarounds (see 'postconf -d' output)
                  List or bit-mask of OpenSSL bug work-arounds to disable.

           tls_preempt_cipherlist (no)
                  With SSLv3 and later, use the Postfix SMTP server's cipher pref-
                  erence order instead of the remote  client's  cipher  preference
                  order.

           Available in Postfix version 2.8..3.7:

           tls_low_cipherlist (see 'postconf -d' output)
                  The OpenSSL cipherlist for "low" or higher grade ciphers.

           tls_export_cipherlist (see 'postconf -d' output)
                  The OpenSSL cipherlist for "export" or higher grade ciphers.

           Available in Postfix version 2.9 and later:

           tls_legacy_public_key_fingerprints (no)
                  A  temporary  migration  aid for sites that use certificate pub-
                  lic-key fingerprints with Postfix  2.9.0..2.9.5,  which  use  an
                  incorrect algorithm.

           Available in Postfix version 2.11-3.1:

           tls_dane_digest_agility (on)
                  Configure RFC7671 DANE TLSA digest algorithm agility.

           tls_dane_trust_anchor_digest_enable (yes)
                  Enable support for RFC 6698 (DANE TLSA) DNS records that contain
                  digests of trust-anchors with certificate usage "2".

           Available in Postfix version 2.11 and later:

           tlsmgr_service_name (tlsmgr)
                  The name of the tlsmgr(8) service entry in master.cf.

           Available in Postfix version 3.0 and later:

           tls_session_ticket_cipher (Postfix >= 3.0: aes-256-cbc, Postfix <  3.0:
           aes-128-cbc)
                  Algorithm used to encrypt RFC5077 TLS session tickets.

           openssl_path (openssl)
                  The location of the OpenSSL command line program openssl(1).

           Available in Postfix version 3.2 and later:

           tls_eecdh_auto_curves (see 'postconf -d' output)
                  The prioritized list of elliptic curves, that should be  enabled
                  in the Postfix SMTP client and server.

           Available in Postfix version 3.4 and later:

           tls_server_sni_maps (empty)
                  Optional  lookup tables that map names received from remote SMTP
                  clients via the TLS Server Name Indication  (SNI)  extension  to
                  the appropriate keys and certificate chains.

           Available in Postfix 3.5, 3.4.6, 3.3.5, 3.2.10, 3.1.13 and later:

           tls_fast_shutdown_enable (yes)
                  A  workaround  for implementations that hang Postfix while shut-
                  ting down a TLS session, until Postfix times out.

           Available in Postfix version 3.8 and later:

           tls_ffdhe_auto_groups (see 'postconf -d' output)
                  The prioritized list of  finite-field  Diffie-Hellman  ephemeral
                  (FFDHE) key exchange groups supported by the Postfix SMTP client
                  and server.

           Available in Postfix 3.9, 3.8.1, 3.7.6, 3.6.10, 3.5.20 and later:

           tls_config_file (default)
                  Optional configuration file with baseline OpenSSL settings.

           tls_config_name (empty)
                  The application name passed by Postfix to OpenSSL  library  ini-
                  tialization functions.

    STARTTLS SERVER CONTROLS
           These  settings are clones of Postfix SMTP server settings.  They allow
           tlsproxy(8) to load the same certificate and private key information as
           the  Postfix  SMTP  server, before dropping privileges, so that the key
           files can be kept read-only for root. These settings can currently  not
           be  overruled  by information in a tlsproxy(8) client request, but that
           limitation may be removed in a future version.

           tlsproxy_tls_CAfile ($smtpd_tls_CAfile)
                  A file containing (PEM  format)  CA  certificates  of  root  CAs
                  trusted to sign either remote SMTP client certificates or inter-
                  mediate CA certificates.

           tlsproxy_tls_CApath ($smtpd_tls_CApath)
                  A directory containing (PEM format) CA certificates of root  CAs
                  trusted to sign either remote SMTP client certificates or inter-
                  mediate CA certificates.

           tlsproxy_tls_always_issue_session_ids     ($smtpd_tls_always_issue_ses-
           sion_ids)
                  Force the Postfix tlsproxy(8) server to issue a TLS session  id,
                  even when TLS session caching is turned off.

           tlsproxy_tls_ask_ccert ($smtpd_tls_ask_ccert)
                  Ask a remote SMTP client for a client certificate.

           tlsproxy_tls_ccert_verifydepth ($smtpd_tls_ccert_verifydepth)
                  The verification depth for remote SMTP client certificates.

           tlsproxy_tls_cert_file ($smtpd_tls_cert_file)
                  File  with the Postfix tlsproxy(8) server RSA certificate in PEM
                  format.

           tlsproxy_tls_ciphers ($smtpd_tls_ciphers)
                  The minimum TLS cipher grade that the Postfix tlsproxy(8) server
                  will use with opportunistic TLS encryption.

           tlsproxy_tls_dcert_file ($smtpd_tls_dcert_file)
                  File  with the Postfix tlsproxy(8) server DSA certificate in PEM
                  format.

           tlsproxy_tls_dh1024_param_file ($smtpd_tls_dh1024_param_file)
                  File with DH parameters  that  the  Postfix  tlsproxy(8)  server
                  should use with non-export EDH ciphers.

           tlsproxy_tls_dh512_param_file ($smtpd_tls_dh512_param_file)
                  File  with  DH  parameters  that  the Postfix tlsproxy(8) server
                  should use with export-grade EDH ciphers.

           tlsproxy_tls_dkey_file ($smtpd_tls_dkey_file)
                  File with the Postfix tlsproxy(8) server DSA private key in  PEM
                  format.

           tlsproxy_tls_eccert_file ($smtpd_tls_eccert_file)
                  File  with  the  Postfix tlsproxy(8) server ECDSA certificate in
                  PEM format.

           tlsproxy_tls_eckey_file ($smtpd_tls_eckey_file)
                  File with the Postfix tlsproxy(8) server ECDSA  private  key  in
                  PEM format.

           tlsproxy_tls_eecdh_grade ($smtpd_tls_eecdh_grade)
                  The  Postfix  tlsproxy(8)  server  security  grade for ephemeral
                  elliptic-curve Diffie-Hellman (EECDH) key exchange.

           tlsproxy_tls_exclude_ciphers ($smtpd_tls_exclude_ciphers)
                  List of ciphers or cipher types to exclude from the  tlsproxy(8)
                  server cipher list at all TLS security levels.

           tlsproxy_tls_fingerprint_digest ($smtpd_tls_fingerprint_digest)
                  The   message   digest   algorithm   to  construct  remote  SMTP
                  client-certificate fingerprints.

           tlsproxy_tls_key_file ($smtpd_tls_key_file)
                  File with the Postfix tlsproxy(8) server RSA private key in  PEM
                  format.

           tlsproxy_tls_loglevel ($smtpd_tls_loglevel)
                  Enable  additional  Postfix  tlsproxy(8)  server  logging of TLS
                  activity.

           tlsproxy_tls_mandatory_ciphers ($smtpd_tls_mandatory_ciphers)
                  The minimum TLS cipher grade that the Postfix tlsproxy(8) server
                  will use with mandatory TLS encryption.

           tlsproxy_tls_mandatory_exclude_ciphers               ($smtpd_tls_manda-
           tory_exclude_ciphers)
                  Additional  list  of ciphers or cipher types to exclude from the
                  tlsproxy(8) server cipher list at mandatory TLS security levels.

           tlsproxy_tls_mandatory_protocols ($smtpd_tls_mandatory_protocols)
                  The SSL/TLS protocols accepted by the Postfix tlsproxy(8) server
                  with mandatory TLS encryption.

           tlsproxy_tls_protocols ($smtpd_tls_protocols)
                  List of TLS protocols that the Postfix tlsproxy(8)  server  will
                  exclude or include with opportunistic TLS encryption.

           tlsproxy_tls_req_ccert ($smtpd_tls_req_ccert)
                  With  mandatory  TLS  encryption,  require a trusted remote SMTP
                  client certificate in order to allow TLS connections to proceed.

           tlsproxy_tls_security_level ($smtpd_tls_security_level)
                  The  SMTP TLS security level for the Postfix tlsproxy(8) server;
                  when a non-empty value is specified, this overrides the obsolete
                  parameters smtpd_use_tls and smtpd_enforce_tls.

           tlsproxy_tls_chain_files ($smtpd_tls_chain_files)
                  Files  with  the Postfix tlsproxy(8) server keys and certificate
                  chains in PEM format.

           Available in Postfix version 3.9 and later:

           tlsproxy_tls_enable_rpk ($smtpd_tls_enable_rpk)
                  Request that remote SMTP clients send an RFC7250 raw public  key
                  instead of an X.509 certificate, when asking or requiring client
                  authentication.

    STARTTLS CLIENT CONTROLS
           These settings are clones of Postfix SMTP client settings.  They  allow
           tlsproxy(8) to load the same certificate and private key information as
           the Postfix SMTP client, before dropping privileges, so  that  the  key
           files can be kept read-only for root. Some settings may be overruled by
           information in a tlsproxy(8) client request.

           Available in Postfix version 3.4 and later:

           tlsproxy_client_CAfile ($smtp_tls_CAfile)
                  A file containing CA certificates of root CAs  trusted  to  sign
                  either  remote  TLS  server certificates or intermediate CA cer-
                  tificates.

           tlsproxy_client_CApath ($smtp_tls_CApath)
                  Directory with PEM format Certification  Authority  certificates
                  that  the Postfix tlsproxy(8) client uses to verify a remote TLS
                  server certificate.

           tlsproxy_client_chain_files ($smtp_tls_chain_files)
                  Files with the Postfix tlsproxy(8) client keys  and  certificate
                  chains in PEM format.

           tlsproxy_client_cert_file ($smtp_tls_cert_file)
                  File  with the Postfix tlsproxy(8) client RSA certificate in PEM
                  format.

           tlsproxy_client_key_file ($smtp_tls_key_file)
                  File with the Postfix tlsproxy(8) client RSA private key in  PEM
                  format.

           tlsproxy_client_dcert_file ($smtp_tls_dcert_file)
                  File  with the Postfix tlsproxy(8) client DSA certificate in PEM
                  format.

           tlsproxy_client_dkey_file ($smtp_tls_dkey_file)
                  File with the Postfix tlsproxy(8) client DSA private key in  PEM
                  format.

           tlsproxy_client_eccert_file ($smtp_tls_eccert_file)
                  File  with  the  Postfix tlsproxy(8) client ECDSA certificate in
                  PEM format.

           tlsproxy_client_eckey_file ($smtp_tls_eckey_file)
                  File with the Postfix tlsproxy(8) client ECDSA  private  key  in
                  PEM format.

           tlsproxy_client_fingerprint_digest ($smtp_tls_fingerprint_digest)
                  The message digest algorithm used to construct remote TLS server
                  certificate fingerprints.

           tlsproxy_client_loglevel ($smtp_tls_loglevel)
                  Enable additional Postfix  tlsproxy(8)  client  logging  of  TLS
                  activity.

           tlsproxy_client_loglevel_parameter (smtp_tls_loglevel)
                  The    name    of    the    parameter    that    provides    the
                  tlsproxy_client_loglevel value.

           tlsproxy_client_scert_verifydepth ($smtp_tls_scert_verifydepth)
                  The verification depth for remote TLS server certificates.

           tlsproxy_client_use_tls ($smtp_use_tls)
                  Opportunistic mode: use TLS when a remote server  announces  TLS
                  support.

           tlsproxy_client_enforce_tls ($smtp_enforce_tls)
                  Enforcement  mode: require that SMTP servers use TLS encryption.

           tlsproxy_client_per_site ($smtp_tls_per_site)
                  Optional lookup tables with the Postfix tlsproxy(8)  client  TLS
                  usage  policy  by  next-hop destination and by remote TLS server
                  hostname.

           Available in Postfix version 3.4-3.6:

           tlsproxy_client_level ($smtp_tls_security_level)
                  The default TLS  security  level  for  the  Postfix  tlsproxy(8)
                  client.

           tlsproxy_client_policy ($smtp_tls_policy_maps)
                  Optional  lookup  tables with the Postfix tlsproxy(8) client TLS
                  security policy by next-hop destination.

           Available in Postfix version 3.7 and later:

           tlsproxy_client_security_level ($smtp_tls_security_level)
                  The default TLS  security  level  for  the  Postfix  tlsproxy(8)
                  client.

           tlsproxy_client_policy_maps ($smtp_tls_policy_maps)
                  Optional  lookup  tables with the Postfix tlsproxy(8) client TLS
                  security policy by next-hop destination.

    OBSOLETE STARTTLS SUPPORT CONTROLS
           These parameters are supported for compatibility with  smtpd(8)  legacy
           parameters.

           tlsproxy_use_tls ($smtpd_use_tls)
                  Opportunistic  TLS:  announce  STARTTLS  support  to remote SMTP
                  clients, but do not require that clients use TLS encryption.

           tlsproxy_enforce_tls ($smtpd_enforce_tls)
                  Mandatory TLS: announce STARTTLS support to remote SMTP clients,
                  and require that clients use TLS encryption.

           tlsproxy_client_use_tls ($smtp_use_tls)
                  Opportunistic  mode:  use TLS when a remote server announces TLS
                  support.

           tlsproxy_client_enforce_tls ($smtp_enforce_tls)
                  Enforcement mode: require that SMTP servers use TLS  encryption.

    RESOURCE CONTROLS
           tlsproxy_watchdog_timeout (10s)
                  How much time a tlsproxy(8) process may take to process local or
                  remote I/O before it is terminated by a built-in watchdog timer.

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

           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
           postscreen(8), Postfix zombie blocker
           smtpd(8), Postfix SMTP server
           postconf(5), configuration parameters
           postlogd(8), Postfix logging
           syslogd(8), system logging

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

    HISTORY
           This service was introduced with Postfix version 2.8.

    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

                                                                       TLSPROXY(8)