1TLSPROXY(8)                 System Manager's Manual                TLSPROXY(8)
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NAME

6       tlsproxy - Postfix TLS proxy
7

SYNOPSIS

9       tlsproxy [generic Postfix daemon options]
10

DESCRIPTION

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
18       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

PROTOCOL EXAMPLE

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
27       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

SECURITY

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

DIAGNOSTICS

44       Problems and transactions are logged to syslogd(8) or postlogd(8).
45

CONFIGURATION PARAMETERS

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
51       The text below provides only a parameter summary. See  postconf(5)  for
52       more details including examples.
53

STARTTLS GLOBAL CONTROLS

55       The  following settings are global and therefore cannot be overruled by
56       information specified in a tlsproxy(8) client request.
57
58       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
63       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
68       tls_high_cipherlist (see 'postconf -d' output)
69              The OpenSSL cipherlist for "high" grade ciphers.
70
71       tls_medium_cipherlist (see 'postconf -d' output)
72              The OpenSSL cipherlist for "medium" or higher grade ciphers.
73
74       tls_low_cipherlist (see 'postconf -d' output)
75              The OpenSSL cipherlist for "low" or higher grade ciphers.
76
77       tls_export_cipherlist (see 'postconf -d' output)
78              The OpenSSL cipherlist for "export" or higher grade ciphers.
79
80       tls_null_cipherlist (eNULL:!aNULL)
81              The OpenSSL cipherlist for "NULL" grade ciphers that provide au‐
82              thentication without encryption.
83
84       tls_eecdh_strong_curve (prime256v1)
85              The  elliptic curve used by the Postfix SMTP server for sensibly
86              strong ephemeral ECDH key exchange.
87
88       tls_eecdh_ultra_curve (secp384r1)
89              The elliptic curve used by the Postfix SMTP server for maximally
90              strong ephemeral ECDH key exchange.
91
92       tls_disable_workarounds (see 'postconf -d' output)
93              List or bit-mask of OpenSSL bug work-arounds to disable.
94
95       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
100       Available in Postfix version 2.9 and later:
101
102       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
107       Available in Postfix version 2.11-3.1:
108
109       tls_dane_digest_agility (on)
110              Configure RFC7671 DANE TLSA digest algorithm agility.
111
112       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
116       Available in Postfix version 2.11 and later:
117
118       tlsmgr_service_name (tlsmgr)
119              The name of the tlsmgr(8) service entry in master.cf.
120
121       Available in Postfix version 3.0 and later:
122
123       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
127       openssl_path (openssl)
128              The location of the OpenSSL command line program openssl(1).
129
130       Available in Postfix version 3.2 and later:
131
132       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
136       Available in Postfix version 3.4 and later:
137
138       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
143       Available in Postfix 3.5, 3.4.6, 3.3.5, 3.2.10, 3.1.13 and later:
144
145       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

STARTTLS SERVER CONTROLS

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
157       tlsproxy_tls_CAfile ($smtpd_tls_CAfile)
158              A file containing (PEM  format)  CA  certificates  of  root  CAs
159              trusted to sign either remote SMTP client certificates or inter‐
160              mediate CA certificates.
161
162       tlsproxy_tls_CApath ($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
167       tlsproxy_tls_always_issue_session_ids     ($smtpd_tls_always_issue_ses‐
168       sion_ids)
169              Force  the Postfix tlsproxy(8) server to issue a TLS session id,
170              even when TLS session caching is turned off.
171
172       tlsproxy_tls_ask_ccert ($smtpd_tls_ask_ccert)
173              Ask a remote SMTP client for a client certificate.
174
175       tlsproxy_tls_ccert_verifydepth ($smtpd_tls_ccert_verifydepth)
176              The verification depth for remote SMTP client certificates.
177
178       tlsproxy_tls_cert_file ($smtpd_tls_cert_file)
179              File with the Postfix tlsproxy(8) server RSA certificate in  PEM
180              format.
181
182       tlsproxy_tls_ciphers ($smtpd_tls_ciphers)
183              The minimum TLS cipher grade that the Postfix tlsproxy(8) server
184              will use with opportunistic TLS encryption.
185
186       tlsproxy_tls_dcert_file ($smtpd_tls_dcert_file)
187              File with the Postfix tlsproxy(8) server DSA certificate in  PEM
188              format.
189
190       tlsproxy_tls_dh1024_param_file ($smtpd_tls_dh1024_param_file)
191              File  with  DH  parameters  that  the Postfix tlsproxy(8) server
192              should use with non-export EDH ciphers.
193
194       tlsproxy_tls_dh512_param_file ($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
198       tlsproxy_tls_dkey_file ($smtpd_tls_dkey_file)
199              File  with the Postfix tlsproxy(8) server DSA private key in PEM
200              format.
201
202       tlsproxy_tls_eccert_file ($smtpd_tls_eccert_file)
203              File with the Postfix tlsproxy(8) server  ECDSA  certificate  in
204              PEM format.
205
206       tlsproxy_tls_eckey_file ($smtpd_tls_eckey_file)
207              File  with  the  Postfix tlsproxy(8) server ECDSA private key in
208              PEM format.
209
210       tlsproxy_tls_eecdh_grade ($smtpd_tls_eecdh_grade)
211              The Postfix tlsproxy(8) server security grade for ephemeral  el‐
212              liptic-curve Diffie-Hellman (EECDH) key exchange.
213
214       tlsproxy_tls_exclude_ciphers ($smtpd_tls_exclude_ciphers)
215              List  of ciphers or cipher types to exclude from the tlsproxy(8)
216              server cipher list at all TLS security levels.
217
218       tlsproxy_tls_fingerprint_digest ($smtpd_tls_fingerprint_digest)
219              The  message  digest  algorithm   to   construct   remote   SMTP
220              client-certificate fingerprints.
221
222       tlsproxy_tls_key_file ($smtpd_tls_key_file)
223              File  with the Postfix tlsproxy(8) server RSA private key in PEM
224              format.
225
226       tlsproxy_tls_loglevel ($smtpd_tls_loglevel)
227              Enable additional Postfix tlsproxy(8) server logging of TLS  ac‐
228              tivity.
229
230       tlsproxy_tls_mandatory_ciphers ($smtpd_tls_mandatory_ciphers)
231              The minimum TLS cipher grade that the Postfix tlsproxy(8) server
232              will use with mandatory TLS encryption.
233
234       tlsproxy_tls_mandatory_exclude_ciphers        ($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
239       tlsproxy_tls_mandatory_protocols ($smtpd_tls_mandatory_protocols)
240              The SSL/TLS protocols accepted by the Postfix tlsproxy(8) server
241              with mandatory TLS encryption.
242
243       tlsproxy_tls_protocols ($smtpd_tls_protocols)
244              List  of  TLS protocols that the Postfix tlsproxy(8) server will
245              exclude or include with opportunistic TLS encryption.
246
247       tlsproxy_tls_req_ccert ($smtpd_tls_req_ccert)
248              With mandatory TLS encryption, require  a  trusted  remote  SMTP
249              client certificate in order to allow TLS connections to proceed.
250
251       tlsproxy_tls_security_level ($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
256       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

STARTTLS CLIENT CONTROLS

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
267       Available in Postfix version 3.4 and later:
268
269       tlsproxy_client_CAfile ($smtp_tls_CAfile)
270              A file containing CA certificates of root CAs  trusted  to  sign
271              either  remote  TLS  server certificates or intermediate CA cer‐
272              tificates.
273
274       tlsproxy_client_CApath ($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
279       tlsproxy_client_chain_files ($smtp_tls_chain_files)
280              Files with the Postfix tlsproxy(8) client keys  and  certificate
281              chains in PEM format.
282
283       tlsproxy_client_cert_file ($smtp_tls_cert_file)
284              File  with the Postfix tlsproxy(8) client RSA certificate in PEM
285              format.
286
287       tlsproxy_client_key_file ($smtp_tls_key_file)
288              File with the Postfix tlsproxy(8) client RSA private key in  PEM
289              format.
290
291       tlsproxy_client_dcert_file ($smtp_tls_dcert_file)
292              File  with the Postfix tlsproxy(8) client DSA certificate in PEM
293              format.
294
295       tlsproxy_client_dkey_file ($smtp_tls_dkey_file)
296              File with the Postfix tlsproxy(8) client DSA private key in  PEM
297              format.
298
299       tlsproxy_client_eccert_file ($smtp_tls_eccert_file)
300              File  with  the  Postfix tlsproxy(8) client ECDSA certificate in
301              PEM format.
302
303       tlsproxy_client_eckey_file ($smtp_tls_eckey_file)
304              File with the Postfix tlsproxy(8) client ECDSA  private  key  in
305              PEM format.
306
307       tlsproxy_client_fingerprint_digest ($smtp_tls_fingerprint_digest)
308              The message digest algorithm used to construct remote TLS server
309              certificate fingerprints.
310
311       tlsproxy_client_loglevel ($smtp_tls_loglevel)
312              Enable additional Postfix tlsproxy(8) client logging of TLS  ac‐
313              tivity.
314
315       tlsproxy_client_loglevel_parameter (smtp_tls_loglevel)
316              The    name   of   the   parameter   that   provides   the   tl‐
317              sproxy_client_loglevel value.
318
319       tlsproxy_client_scert_verifydepth ($smtp_tls_scert_verifydepth)
320              The verification depth for remote TLS server certificates.
321
322       tlsproxy_client_use_tls ($smtp_use_tls)
323              Opportunistic mode: use TLS when a remote server  announces  TLS
324              support.
325
326       tlsproxy_client_enforce_tls ($smtp_enforce_tls)
327              Enforcement mode: require that SMTP servers use TLS encryption.
328
329       tlsproxy_client_per_site ($smtp_tls_per_site)
330              Optional  lookup  tables with the Postfix tlsproxy(8) client TLS
331              usage policy by next-hop destination and by  remote  TLS  server
332              hostname.
333
334       Available in Postfix version 3.4-3.6:
335
336       tlsproxy_client_level ($smtp_tls_security_level)
337              The  default  TLS  security  level  for  the Postfix tlsproxy(8)
338              client.
339
340       tlsproxy_client_policy ($smtp_tls_policy_maps)
341              Optional lookup tables with the Postfix tlsproxy(8)  client  TLS
342              security policy by next-hop destination.
343
344       Available in Postfix version 3.7 and later:
345
346       tlsproxy_client_security_level ($smtp_tls_security_level)
347              The  default  TLS  security  level  for  the Postfix tlsproxy(8)
348              client.
349
350       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

OBSOLETE STARTTLS SUPPORT CONTROLS

355       These  parameters  are supported for compatibility with smtpd(8) legacy
356       parameters.
357
358       tlsproxy_use_tls ($smtpd_use_tls)
359              Opportunistic TLS: announce  STARTTLS  support  to  remote  SMTP
360              clients, but do not require that clients use TLS encryption.
361
362       tlsproxy_enforce_tls ($smtpd_enforce_tls)
363              Mandatory TLS: announce STARTTLS support to remote SMTP clients,
364              and require that clients use TLS encryption.
365
366       tlsproxy_client_use_tls ($smtp_use_tls)
367              Opportunistic mode: use TLS when a remote server  announces  TLS
368              support.
369
370       tlsproxy_client_enforce_tls ($smtp_enforce_tls)
371              Enforcement mode: require that SMTP servers use TLS encryption.
372

RESOURCE CONTROLS

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

MISCELLANEOUS CONTROLS

379       config_directory (see 'postconf -d' output)
380              The default location of the Postfix main.cf and  master.cf  con‐
381              figuration files.
382
383       process_id (read-only)
384              The process ID of a Postfix command or daemon process.
385
386       process_name (read-only)
387              The process name of a Postfix command or daemon process.
388
389       syslog_facility (mail)
390              The syslog facility of Postfix logging.
391
392       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
396       Available in Postfix 3.3 and later:
397
398       service_name (read-only)
399              The master.cf service name of a Postfix daemon process.
400

SEE ALSO

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

LICENSE

409       The Secure Mailer license must be distributed with this software.
410

HISTORY

412       This service was introduced with Postfix version 2.8.
413

AUTHOR(S)

415       Wietse Venema
416       IBM T.J. Watson Research
417       P.O. Box 704
418       Yorktown Heights, NY 10598, USA
419
420       Wietse Venema
421       Google, Inc.
422       111 8th Avenue
423       New York, NY 10011, USA
424
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427                                                                   TLSPROXY(8)
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