TLSPROXY(8postfix)TLSPROXY(8postfix)NAMEtlsproxy - Postfix TLS proxy
SYNOPSIStlsproxy [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 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).
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 SUPPORT CONTROLS
tlsproxy_tls_CAfile ($smtpd_tls_CAfile)
A file containing (PEM format) CA certificates of root CAs
trusted to sign either remote SMTP client certificates or inter‐
mediate CA certificates.
tlsproxy_tls_CApath ($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 ($smtpd_tls_dh1024_param_file)
File with DH parameters that the Postfix tlsproxy(8) server
should use with EDH ciphers.
tlsproxy_tls_dh512_param_file ($smtpd_tls_dh512_param_file)
File with DH parameters that the Postfix tlsproxy(8) server
should use with 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_session_cache_timeout ($smtpd_tls_session_cache_timeout)
The expiration time of Postfix tlsproxy(8) server TLS session
cache information.
OBSOLETE STARTTLS SUPPORT CONTROLS
These parameters are supported for compatibility with smtpd(8) legacy
parameters.
tlsproxy_use_tls ($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 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)
The mail system name that is prepended to the process name in
syslog records, so that "smtpd" becomes, for example, "post‐
fix/smtpd".
SEE ALSOpostscreen(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)
