1TLSPROXY(8) System Manager's Manual TLSPROXY(8)
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6 tlsproxy - Postfix TLS proxy
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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 allowlisted (including clients whose allowlist 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 in‐
20 crease 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 tl‐
31 sproxy(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 au‐
82 thentication 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 in‐
105 correct 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 Available in Postfix 3.5, 3.4.6, 3.3.5, 3.2.10, 3.1.13 and later:
144 tls_fast_shutdown_enable (yes)
146 A workaround for implementations that hang Postfix while shut‐
147 ting down a TLS session, until Postfix times out.
148
150 These settings are clones of Postfix SMTP server settings. They allow
151 tlsproxy(8) to load the same certificate and private key information as
152 the Postfix SMTP server, before dropping privileges, so that the key
153 files can be kept read-only for root. These settings can currently not
154 be overruled by information in a tlsproxy(8) client request, but that
155 limitation may be removed in a future version.
156 tlsproxy_tls_CAfile ($smtpd_tls_CAfile)
158 A file containing (PEM format) CA certificates of root CAs
159 trusted to sign either remote SMTP client certificates or inter‐
160 mediate CA certificates.
161 tlsproxy_tls_CApath ($smtpd_tls_CApath)
163 A directory containing (PEM format) CA certificates of root CAs
164 trusted to sign either remote SMTP client certificates or inter‐
165 mediate CA certificates.
166 tlsproxy_tls_always_issue_session_ids ($smtpd_tls_always_issue_ses‐
168 sion_ids)
169 Force the Postfix tlsproxy(8) server to issue a TLS session id,
170 even when TLS session caching is turned off.
171 tlsproxy_tls_ask_ccert ($smtpd_tls_ask_ccert)
173 Ask a remote SMTP client for a client certificate.
174 tlsproxy_tls_ccert_verifydepth ($smtpd_tls_ccert_verifydepth)
176 The verification depth for remote SMTP client certificates.
177 tlsproxy_tls_cert_file ($smtpd_tls_cert_file)
179 File with the Postfix tlsproxy(8) server RSA certificate in PEM
180 format.
181 tlsproxy_tls_ciphers ($smtpd_tls_ciphers)
183 The minimum TLS cipher grade that the Postfix tlsproxy(8) server
184 will use with opportunistic TLS encryption.
185 tlsproxy_tls_dcert_file ($smtpd_tls_dcert_file)
187 File with the Postfix tlsproxy(8) server DSA certificate in PEM
188 format.
189 tlsproxy_tls_dh1024_param_file ($smtpd_tls_dh1024_param_file)
191 File with DH parameters that the Postfix tlsproxy(8) server
192 should use with non-export EDH ciphers.
193 tlsproxy_tls_dh512_param_file ($smtpd_tls_dh512_param_file)
195 File with DH parameters that the Postfix tlsproxy(8) server
196 should use with export-grade EDH ciphers.
197 tlsproxy_tls_dkey_file ($smtpd_tls_dkey_file)
199 File with the Postfix tlsproxy(8) server DSA private key in PEM
200 format.
201 tlsproxy_tls_eccert_file ($smtpd_tls_eccert_file)
203 File with the Postfix tlsproxy(8) server ECDSA certificate in
204 PEM format.
205 tlsproxy_tls_eckey_file ($smtpd_tls_eckey_file)
207 File with the Postfix tlsproxy(8) server ECDSA private key in
208 PEM format.
209 tlsproxy_tls_eecdh_grade ($smtpd_tls_eecdh_grade)
211 The Postfix tlsproxy(8) server security grade for ephemeral el‐
212 liptic-curve Diffie-Hellman (EECDH) key exchange.
213 tlsproxy_tls_exclude_ciphers ($smtpd_tls_exclude_ciphers)
215 List of ciphers or cipher types to exclude from the tlsproxy(8)
216 server cipher list at all TLS security levels.
217 tlsproxy_tls_fingerprint_digest ($smtpd_tls_fingerprint_digest)
219 The message digest algorithm to construct remote SMTP
220 client-certificate fingerprints.
221 tlsproxy_tls_key_file ($smtpd_tls_key_file)
223 File with the Postfix tlsproxy(8) server RSA private key in PEM
224 format.
225 tlsproxy_tls_loglevel ($smtpd_tls_loglevel)
227 Enable additional Postfix tlsproxy(8) server logging of TLS ac‐
228 tivity.
229 tlsproxy_tls_mandatory_ciphers ($smtpd_tls_mandatory_ciphers)
231 The minimum TLS cipher grade that the Postfix tlsproxy(8) server
232 will use with mandatory TLS encryption.
233 tlsproxy_tls_mandatory_exclude_ciphers ($smtpd_tls_mandatory_ex‐
235 clude_ciphers)
236 Additional list of ciphers or cipher types to exclude from the
237 tlsproxy(8) server cipher list at mandatory TLS security levels.
238 tlsproxy_tls_mandatory_protocols ($smtpd_tls_mandatory_protocols)
240 The SSL/TLS protocols accepted by the Postfix tlsproxy(8) server
241 with mandatory TLS encryption.
242 tlsproxy_tls_protocols ($smtpd_tls_protocols)
244 List of TLS protocols that the Postfix tlsproxy(8) server will
245 exclude or include with opportunistic TLS encryption.
246 tlsproxy_tls_req_ccert ($smtpd_tls_req_ccert)
248 With mandatory TLS encryption, require a trusted remote SMTP
249 client certificate in order to allow TLS connections to proceed.
250 tlsproxy_tls_security_level ($smtpd_tls_security_level)
252 The SMTP TLS security level for the Postfix tlsproxy(8) server;
253 when a non-empty value is specified, this overrides the obsolete
254 parameters smtpd_use_tls and smtpd_enforce_tls.
255 tlsproxy_tls_chain_files ($smtpd_tls_chain_files)
257 Files with the Postfix tlsproxy(8) server keys and certificate
258 chains in PEM format.
259
261 These settings are clones of Postfix SMTP client settings. They allow
262 tlsproxy(8) to load the same certificate and private key information as
263 the Postfix SMTP client, before dropping privileges, so that the key
264 files can be kept read-only for root. Some settings may be overruled by
265 information in a tlsproxy(8) client request.
266 Available in Postfix version 3.4 and later:
268 tlsproxy_client_CAfile ($smtp_tls_CAfile)
270 A file containing CA certificates of root CAs trusted to sign
271 either remote TLS server certificates or intermediate CA cer‐
272 tificates.
273 tlsproxy_client_CApath ($smtp_tls_CApath)
275 Directory with PEM format Certification Authority certificates
276 that the Postfix tlsproxy(8) client uses to verify a remote TLS
277 server certificate.
278 tlsproxy_client_chain_files ($smtp_tls_chain_files)
280 Files with the Postfix tlsproxy(8) client keys and certificate
281 chains in PEM format.
282 tlsproxy_client_cert_file ($smtp_tls_cert_file)
284 File with the Postfix tlsproxy(8) client RSA certificate in PEM
285 format.
286 tlsproxy_client_key_file ($smtp_tls_key_file)
288 File with the Postfix tlsproxy(8) client RSA private key in PEM
289 format.
290 tlsproxy_client_dcert_file ($smtp_tls_dcert_file)
292 File with the Postfix tlsproxy(8) client DSA certificate in PEM
293 format.
294 tlsproxy_client_dkey_file ($smtp_tls_dkey_file)
296 File with the Postfix tlsproxy(8) client DSA private key in PEM
297 format.
298 tlsproxy_client_eccert_file ($smtp_tls_eccert_file)
300 File with the Postfix tlsproxy(8) client ECDSA certificate in
301 PEM format.
302 tlsproxy_client_eckey_file ($smtp_tls_eckey_file)
304 File with the Postfix tlsproxy(8) client ECDSA private key in
305 PEM format.
306 tlsproxy_client_fingerprint_digest ($smtp_tls_fingerprint_digest)
308 The message digest algorithm used to construct remote TLS server
309 certificate fingerprints.
310 tlsproxy_client_loglevel ($smtp_tls_loglevel)
312 Enable additional Postfix tlsproxy(8) client logging of TLS ac‐
313 tivity.
314 tlsproxy_client_loglevel_parameter (smtp_tls_loglevel)
316 The name of the parameter that provides the tl‐
317 sproxy_client_loglevel value.
318 tlsproxy_client_scert_verifydepth ($smtp_tls_scert_verifydepth)
320 The verification depth for remote TLS server certificates.
321 tlsproxy_client_use_tls ($smtp_use_tls)
323 Opportunistic mode: use TLS when a remote server announces TLS
324 support.
325 tlsproxy_client_enforce_tls ($smtp_enforce_tls)
327 Enforcement mode: require that SMTP servers use TLS encryption.
328 tlsproxy_client_per_site ($smtp_tls_per_site)
330 Optional lookup tables with the Postfix tlsproxy(8) client TLS
331 usage policy by next-hop destination and by remote TLS server
332 hostname.
333 Available in Postfix version 3.4-3.6:
335 tlsproxy_client_level ($smtp_tls_security_level)
337 The default TLS security level for the Postfix tlsproxy(8)
338 client.
339 tlsproxy_client_policy ($smtp_tls_policy_maps)
341 Optional lookup tables with the Postfix tlsproxy(8) client TLS
342 security policy by next-hop destination.
343 Available in Postfix version 3.7 and later:
345 tlsproxy_client_security_level ($smtp_tls_security_level)
347 The default TLS security level for the Postfix tlsproxy(8)
348 client.
349 tlsproxy_client_policy_maps ($smtp_tls_policy_maps)
351 Optional lookup tables with the Postfix tlsproxy(8) client TLS
352 security policy by next-hop destination.
353
355 These parameters are supported for compatibility with smtpd(8) legacy
356 parameters.
357 tlsproxy_use_tls ($smtpd_use_tls)
359 Opportunistic TLS: announce STARTTLS support to remote SMTP
360 clients, but do not require that clients use TLS encryption.
361 tlsproxy_enforce_tls ($smtpd_enforce_tls)
363 Mandatory TLS: announce STARTTLS support to remote SMTP clients,
364 and require that clients use TLS encryption.
365 tlsproxy_client_use_tls ($smtp_use_tls)
367 Opportunistic mode: use TLS when a remote server announces TLS
368 support.
369 tlsproxy_client_enforce_tls ($smtp_enforce_tls)
371 Enforcement mode: require that SMTP servers use TLS encryption.
372
374 tlsproxy_watchdog_timeout (10s)
375 How much time a tlsproxy(8) process may take to process local or
376 remote I/O before it is terminated by a built-in watchdog timer.
377
379 config_directory (see 'postconf -d' output)
380 The default location of the Postfix main.cf and master.cf con‐
381 figuration files.
382 process_id (read-only)
384 The process ID of a Postfix command or daemon process.
385 process_name (read-only)
387 The process name of a Postfix command or daemon process.
388 syslog_facility (mail)
390 The syslog facility of Postfix logging.
391 syslog_name (see 'postconf -d' output)
393 A prefix that is prepended to the process name in syslog
394 records, so that, for example, "smtpd" becomes "prefix/smtpd".
395 Available in Postfix 3.3 and later:
397 service_name (read-only)
399 The master.cf service name of a Postfix daemon process.
400
402 postscreen(8), Postfix zombie blocker
403 smtpd(8), Postfix SMTP server
404 postconf(5), configuration parameters
405 postlogd(8), Postfix logging
406 syslogd(8), system logging
407
409 The Secure Mailer license must be distributed with this software.
410
412 This service was introduced with Postfix version 2.8.
413
415 Wietse Venema
416 IBM T.J. Watson Research
417 P.O. Box 704
418 Yorktown Heights, NY 10598, USA
419 Wietse Venema
421 Google, Inc.
422 111 8th Avenue
423 New York, NY 10011, USA
424 TLSPROXY(8)