1TLSPROXY(8) System Manager's Manual TLSPROXY(8)
2
6 tlsproxy - Postfix TLS proxy
7
9 tlsproxy [generic Postfix daemon options]
10
12 The tlsproxy(8) server implements a two-way TLS proxy. It is used by
13 the postscreen(8) server to talk SMTP-over-TLS with remote SMTP clients
14 that are not whitelisted (including clients whose whitelist status has
15 expired), and by the smtp(8) client to support TLS connection reuse,
16 but it should also work for non-SMTP protocols.
17 Although one tlsproxy(8) process can serve multiple sessions at the
19 same time, it is a good idea to allow the number of processes to
20 increase with load, so that the service remains responsive.
21
23 The example below concerns postscreen(8). However, the tlsproxy(8)
24 server is agnostic of the application protocol, and the example is eas‐
25 ily adapted to other applications.
26 After receiving a valid remote SMTP client STARTTLS command, the
28 postscreen(8) server sends the remote SMTP client endpoint string, the
29 requested role (server), and the requested timeout to tlsproxy(8).
30 postscreen(8) then receives a "TLS available" indication from
31 tlsproxy(8). If the TLS service is available, postscreen(8) sends the
32 remote SMTP client file descriptor to tlsproxy(8), and sends the plain‐
33 text 220 greeting to the remote SMTP client. This triggers TLS negoti‐
34 ations between the remote SMTP client and tlsproxy(8). Upon completion
35 of the TLS-level handshake, tlsproxy(8) translates between plaintext
36 from/to postscreen(8) and ciphertext to/from the remote SMTP client.
37
39 The tlsproxy(8) server is moderately security-sensitive. It talks to
40 untrusted clients on the network. The process can be run chrooted at
41 fixed low privilege.
42
44 Problems and transactions are logged to syslogd(8) or postlogd(8).
45
47 Changes to main.cf are not picked up automatically, as tlsproxy(8) pro‐
48 cesses may run for a long time depending on mail server load. Use the
49 command "postfix reload" to speed up a change.
50 The text below provides only a parameter summary. See postconf(5) for
52 more details including examples.
53
55 The following settings are global and therefore cannot be overruled by
56 information specified in a tlsproxy(8) client request.
57 tls_append_default_CA (no)
59 Append the system-supplied default Certification Authority cer‐
60 tificates to the ones specified with *_tls_CApath or
61 *_tls_CAfile.
62 tls_daemon_random_bytes (32)
64 The number of pseudo-random bytes that an smtp(8) or smtpd(8)
65 process requests from the tlsmgr(8) server in order to seed its
66 internal pseudo random number generator (PRNG).
67 tls_high_cipherlist (see 'postconf -d' output)
69 The OpenSSL cipherlist for "high" grade ciphers.
70 tls_medium_cipherlist (see 'postconf -d' output)
72 The OpenSSL cipherlist for "medium" or higher grade ciphers.
73 tls_low_cipherlist (see 'postconf -d' output)
75 The OpenSSL cipherlist for "low" or higher grade ciphers.
76 tls_export_cipherlist (see 'postconf -d' output)
78 The OpenSSL cipherlist for "export" or higher grade ciphers.
79 tls_null_cipherlist (eNULL:!aNULL)
81 The OpenSSL cipherlist for "NULL" grade ciphers that provide
82 authentication without encryption.
83 tls_eecdh_strong_curve (prime256v1)
85 The elliptic curve used by the Postfix SMTP server for sensibly
86 strong ephemeral ECDH key exchange.
87 tls_eecdh_ultra_curve (secp384r1)
89 The elliptic curve used by the Postfix SMTP server for maximally
90 strong ephemeral ECDH key exchange.
91 tls_disable_workarounds (see 'postconf -d' output)
93 List or bit-mask of OpenSSL bug work-arounds to disable.
94 tls_preempt_cipherlist (no)
96 With SSLv3 and later, use the Postfix SMTP server's cipher pref‐
97 erence order instead of the remote client's cipher preference
98 order.
99 Available in Postfix version 2.9 and later:
101 tls_legacy_public_key_fingerprints (no)
103 A temporary migration aid for sites that use certificate pub‐
104 lic-key fingerprints with Postfix 2.9.0..2.9.5, which use an
105 incorrect algorithm.
106 Available in Postfix version 2.11-3.1:
108 tls_dane_digest_agility (on)
110 Configure RFC7671 DANE TLSA digest algorithm agility.
111 tls_dane_trust_anchor_digest_enable (yes)
113 Enable support for RFC 6698 (DANE TLSA) DNS records that contain
114 digests of trust-anchors with certificate usage "2".
115 Available in Postfix version 2.11 and later:
117 tlsmgr_service_name (tlsmgr)
119 The name of the tlsmgr(8) service entry in master.cf.
120 Available in Postfix version 3.0 and later:
122 tls_session_ticket_cipher (Postfix >= 3.0: aes-256-cbc, Postfix < 3.0:
124 aes-128-cbc)
125 Algorithm used to encrypt RFC5077 TLS session tickets.
126 openssl_path (openssl)
128 The location of the OpenSSL command line program openssl(1).
129 Available in Postfix version 3.2 and later:
131 tls_eecdh_auto_curves (see 'postconf -d' output)
133 The prioritized list of elliptic curves supported by the Postfix
134 SMTP client and server.
135 Available in Postfix version 3.4 and later:
137 tls_server_sni_maps (empty)
139 Optional lookup tables that map names received from remote SMTP
140 clients via the TLS Server Name Indication (SNI) extension to
141 the appropriate keys and certificate chains.
142
144 These settings are clones of Postfix SMTP server settings. They allow
145 tlsproxy(8) to load the same certificate and private key information as
146 the Postfix SMTP server, before dropping privileges, so that the key
147 files can be kept read-only for root. These settings can currently not
148 be overruled by information in a tlsproxy(8) client request, but that
149 limitation may be removed in a future version.
150 tlsproxy_tls_CAfile ($smtpd_tls_CAfile)
152 A file containing (PEM format) CA certificates of root CAs
153 trusted to sign either remote SMTP client certificates or inter‐
154 mediate CA certificates.
155 tlsproxy_tls_CApath ($smtpd_tls_CApath)
157 A directory containing (PEM format) CA certificates of root CAs
158 trusted to sign either remote SMTP client certificates or inter‐
159 mediate CA certificates.
160 tlsproxy_tls_always_issue_session_ids ($smtpd_tls_always_issue_ses‐
162 sion_ids)
163 Force the Postfix tlsproxy(8) server to issue a TLS session id,
164 even when TLS session caching is turned off.
165 tlsproxy_tls_ask_ccert ($smtpd_tls_ask_ccert)
167 Ask a remote SMTP client for a client certificate.
168 tlsproxy_tls_ccert_verifydepth ($smtpd_tls_ccert_verifydepth)
170 The verification depth for remote SMTP client certificates.
171 tlsproxy_tls_cert_file ($smtpd_tls_cert_file)
173 File with the Postfix tlsproxy(8) server RSA certificate in PEM
174 format.
175 tlsproxy_tls_ciphers ($smtpd_tls_ciphers)
177 The minimum TLS cipher grade that the Postfix tlsproxy(8) server
178 will use with opportunistic TLS encryption.
179 tlsproxy_tls_dcert_file ($smtpd_tls_dcert_file)
181 File with the Postfix tlsproxy(8) server DSA certificate in PEM
182 format.
183 tlsproxy_tls_dh1024_param_file ($smtpd_tls_dh1024_param_file)
185 File with DH parameters that the Postfix tlsproxy(8) server
186 should use with non-export EDH ciphers.
187 tlsproxy_tls_dh512_param_file ($smtpd_tls_dh512_param_file)
189 File with DH parameters that the Postfix tlsproxy(8) server
190 should use with export-grade EDH ciphers.
191 tlsproxy_tls_dkey_file ($smtpd_tls_dkey_file)
193 File with the Postfix tlsproxy(8) server DSA private key in PEM
194 format.
195 tlsproxy_tls_eccert_file ($smtpd_tls_eccert_file)
197 File with the Postfix tlsproxy(8) server ECDSA certificate in
198 PEM format.
199 tlsproxy_tls_eckey_file ($smtpd_tls_eckey_file)
201 File with the Postfix tlsproxy(8) server ECDSA private key in
202 PEM format.
203 tlsproxy_tls_eecdh_grade ($smtpd_tls_eecdh_grade)
205 The Postfix tlsproxy(8) server security grade for ephemeral
206 elliptic-curve Diffie-Hellman (EECDH) key exchange.
207 tlsproxy_tls_exclude_ciphers ($smtpd_tls_exclude_ciphers)
209 List of ciphers or cipher types to exclude from the tlsproxy(8)
210 server cipher list at all TLS security levels.
211 tlsproxy_tls_fingerprint_digest ($smtpd_tls_fingerprint_digest)
213 The message digest algorithm to construct remote SMTP
214 client-certificate fingerprints.
215 tlsproxy_tls_key_file ($smtpd_tls_key_file)
217 File with the Postfix tlsproxy(8) server RSA private key in PEM
218 format.
219 tlsproxy_tls_loglevel ($smtpd_tls_loglevel)
221 Enable additional Postfix tlsproxy(8) server logging of TLS
222 activity.
223 tlsproxy_tls_mandatory_ciphers ($smtpd_tls_mandatory_ciphers)
225 The minimum TLS cipher grade that the Postfix tlsproxy(8) server
226 will use with mandatory TLS encryption.
227 tlsproxy_tls_mandatory_exclude_ciphers ($smtpd_tls_manda‐
229 tory_exclude_ciphers)
230 Additional list of ciphers or cipher types to exclude from the
231 tlsproxy(8) server cipher list at mandatory TLS security levels.
232 tlsproxy_tls_mandatory_protocols ($smtpd_tls_mandatory_protocols)
234 The SSL/TLS protocols accepted by the Postfix tlsproxy(8) server
235 with mandatory TLS encryption.
236 tlsproxy_tls_protocols ($smtpd_tls_protocols)
238 List of TLS protocols that the Postfix tlsproxy(8) server will
239 exclude or include with opportunistic TLS encryption.
240 tlsproxy_tls_req_ccert ($smtpd_tls_req_ccert)
242 With mandatory TLS encryption, require a trusted remote SMTP
243 client certificate in order to allow TLS connections to proceed.
244 tlsproxy_tls_security_level ($smtpd_tls_security_level)
246 The SMTP TLS security level for the Postfix tlsproxy(8) server;
247 when a non-empty value is specified, this overrides the obsolete
248 parameters smtpd_use_tls and smtpd_enforce_tls.
249 tlsproxy_tls_chain_files ($smtpd_tls_chain_files)
251 Files with the Postfix tlsproxy(8) server keys and certificate
252 chains in PEM format.
253
255 These settings are clones of Postfix SMTP client settings. They allow
256 tlsproxy(8) to load the same certificate and private key information as
257 the Postfix SMTP client, before dropping privileges, so that the key
258 files can be kept read-only for root. Some settings may be overruled by
259 information in a tlsproxy(8) client request.
260 Available in Postfix version 3.4 and later:
262 tlsproxy_client_CAfile ($smtp_tls_CAfile)
264 A file containing CA certificates of root CAs trusted to sign
265 either remote TLS server certificates or intermediate CA cer‐
266 tificates.
267 tlsproxy_client_CApath ($smtp_tls_CApath)
269 Directory with PEM format Certification Authority certificates
270 that the Postfix tlsproxy(8) client uses to verify a remote TLS
271 server certificate.
272 tlsproxy_client_chain_files ($smtp_tls_chain_files)
274 Files with the Postfix tlsproxy(8) client keys and certificate
275 chains in PEM format.
276 tlsproxy_client_cert_file ($smtp_tls_cert_file)
278 File with the Postfix tlsproxy(8) client RSA certificate in PEM
279 format.
280 tlsproxy_client_key_file ($smtp_tls_key_file)
282 File with the Postfix tlsproxy(8) client RSA private key in PEM
283 format.
284 tlsproxy_client_dcert_file ($smtp_tls_dcert_file)
286 File with the Postfix tlsproxy(8) client DSA certificate in PEM
287 format.
288 tlsproxy_client_dkey_file ($smtp_tls_dkey_file)
290 File with the Postfix tlsproxy(8) client DSA private key in PEM
291 format.
292 tlsproxy_client_eccert_file ($smtp_tls_eccert_file)
294 File with the Postfix tlsproxy(8) client ECDSA certificate in
295 PEM format.
296 tlsproxy_client_eckey_file ($smtp_tls_eckey_file)
298 File with the Postfix tlsproxy(8) client ECDSA private key in
299 PEM format.
300 tlsproxy_client_fingerprint_digest ($smtp_tls_fingerprint_digest)
302 The message digest algorithm used to construct remote TLS server
303 certificate fingerprints.
304 tlsproxy_client_loglevel ($smtp_tls_loglevel)
306 Enable additional Postfix tlsproxy(8) client logging of TLS
307 activity.
308 tlsproxy_client_loglevel_parameter (smtp_tls_loglevel)
310 The name of the parameter that provides the
311 tlsproxy_client_loglevel value.
312 tlsproxy_client_scert_verifydepth ($smtp_tls_scert_verifydepth)
314 The verification depth for remote TLS server certificates.
315 tlsproxy_client_security_level ($smtp_tls_security_level)
317 The default TLS security level for the Postfix tlsproxy(8)
318 client.
319 tlsproxy_client_policy_maps ($smtp_tls_policy_maps)
321 Optional lookup tables with the Postfix tlsproxy(8) client TLS
322 security policy by next-hop destination.
323 tlsproxy_client_use_tls ($smtp_use_tls)
325 Opportunistic mode: use TLS when a remote server announces TLS
326 support.
327 tlsproxy_client_enforce_tls ($smtp_enforce_tls)
329 Enforcement mode: require that SMTP servers use TLS encryption.
330 tlsproxy_client_per_site ($smtp_tls_per_site)
332 Optional lookup tables with the Postfix tlsproxy(8) client TLS
333 usage policy by next-hop destination and by remote TLS server
334 hostname.
335
337 These parameters are supported for compatibility with smtpd(8) legacy
338 parameters.
339 tlsproxy_use_tls ($smtpd_use_tls)
341 Opportunistic TLS: announce STARTTLS support to remote SMTP
342 clients, but do not require that clients use TLS encryption.
343 tlsproxy_enforce_tls ($smtpd_enforce_tls)
345 Mandatory TLS: announce STARTTLS support to remote SMTP clients,
346 and require that clients use TLS encryption.
347
349 tlsproxy_watchdog_timeout (10s)
350 How much time a tlsproxy(8) process may take to process local or
351 remote I/O before it is terminated by a built-in watchdog timer.
352
354 config_directory (see 'postconf -d' output)
355 The default location of the Postfix main.cf and master.cf con‐
356 figuration files.
357 process_id (read-only)
359 The process ID of a Postfix command or daemon process.
360 process_name (read-only)
362 The process name of a Postfix command or daemon process.
363 syslog_facility (mail)
365 The syslog facility of Postfix logging.
366 syslog_name (see 'postconf -d' output)
368 A prefix that is prepended to the process name in syslog
369 records, so that, for example, "smtpd" becomes "prefix/smtpd".
370 Available in Postfix 3.3 and later:
372 service_name (read-only)
374 The master.cf service name of a Postfix daemon process.
375
377 postscreen(8), Postfix zombie blocker
378 smtpd(8), Postfix SMTP server
379 postconf(5), configuration parameters
380 postlogd(8), Postfix logging
381 syslogd(8), system logging
382
384 The Secure Mailer license must be distributed with this software.
385
387 This service was introduced with Postfix version 2.8.
388
390 Wietse Venema
391 IBM T.J. Watson Research
392 P.O. Box 704
393 Yorktown Heights, NY 10598, USA
394 Wietse Venema
396 Google, Inc.
397 111 8th Avenue
398 New York, NY 10011, USA
399 TLSPROXY(8)