NAME

       tlsproxy - Postfix TLS proxy

SYNOPSIS

       tlsproxy [generic Postfix daemon options]

DESCRIPTION

       The  tlsproxy(8) server implements a server-side TLS proxy. It is used by postscreen(8) to
       talk SMTP-over-TLS with remote SMTP clients that are not  whitelisted  (including  clients
       whose whitelist status has expired), 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 easily 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 plaintext 220 greeting to
       the remote SMTP client.  This triggers TLS negotiations 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).

CONFIGURATION PARAMETERS

       Changes to main.cf are not picked up automatically, as tlsproxy(8) processes 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 SUPPORT CONTROLS

       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 intermediate 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 intermediate CA certificates.

       tlsproxy_tls_always_issue_session_ids ($smtpd_tls_always_issue_session_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_mandatory_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.

       Available in Postfix version 2.11 and later:

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

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.

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 configuration 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)
              The mail system name that is prepended to the process name in  syslog  records,  so
              that "smtpd" becomes, for example, "postfix/smtpd".

SEE ALSO

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

                                                                               TLSPROXY(8postfix)