Linux Manual Pages

Free Software * Books

Source Code

Free Media

Linux

TLSPROXY

NAME
SYNOPSIS
DESCRIPTION
PROTOCOL EXAMPLE
SECURITY
DIAGNOSTICS
CONFIGURATION PARAMETERS
STARTTLS SUPPORT CONTROLS
OBSOLETE STARTTLS SUPPORT CONTROLS
RESOURCE CONTROLS
MISCELLANEOUS CONTROLS
SEE ALSO
LICENSE
HISTORY
AUTHOR(S)

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".

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

Opportunity

Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.

Free Software

Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.

Free Books

The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.

Education

Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.