.section "Including TLS/SSL encryption support" "SECTinctlsssl"
.cindex "TLS" "including support for TLS"
.cindex "encryption" "including support for"
-.cindex "SUPPORT_TLS"
.cindex "OpenSSL" "building Exim with"
.cindex "GnuTLS" "building Exim with"
-Exim can be built to support encrypted SMTP connections, using the STARTTLS
-command as per RFC 2487. It can also support legacy clients that expect to
+Exim is usually built to support encrypted SMTP connections, using the STARTTLS
+command as per RFC 2487. It can also support clients that expect to
start a TLS session immediately on connection to a non-standard port (see the
&%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
line option).
OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
implementing SSL.
+.new
+If you do not want TLS support you should set
+.code
+DISABLE_TLS=yes
+.endd
+in &_Local/Makefile_&.
+.wen
+
If OpenSSL is installed, you should set
.code
-SUPPORT_TLS=yes
+USE_OPENSL=yes
TLS_LIBS=-lssl -lcrypto
.endd
in &_Local/Makefile_&. You may also need to specify the locations of the
OpenSSL library and include files. For example:
.code
-SUPPORT_TLS=yes
+USE_OPENSL=yes
TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
TLS_INCLUDE=-I/usr/local/openssl/include/
.endd
.cindex "pkg-config" "OpenSSL"
If you have &'pkg-config'& available, then instead you can just use:
.code
-SUPPORT_TLS=yes
+USE_OPENSL=yes
USE_OPENSSL_PC=openssl
.endd
.cindex "USE_GNUTLS"
If GnuTLS is installed, you should set
.code
-SUPPORT_TLS=yes
USE_GNUTLS=yes
TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
.endd
in &_Local/Makefile_&, and again you may need to specify the locations of the
library and include files. For example:
.code
-SUPPORT_TLS=yes
USE_GNUTLS=yes
TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
TLS_INCLUDE=-I/usr/gnu/include
.cindex "pkg-config" "GnuTLS"
If you have &'pkg-config'& available, then instead you can just use:
.code
-SUPPORT_TLS=yes
USE_GNUTLS=yes
USE_GNUTLS_PC=gnutls
.endd
remote_smtp:
driver = smtp
message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}}
-.ifdef _HAVE_DANE
- hosts_try_dane = *
-.endif
.ifdef _HAVE_PRDR
hosts_try_prdr = *
.endif
With &"strict"& a response from the DNS resolver that
is not labelled as authenticated data
is treated as equivalent to a temporary DNS error.
-The default is &"never"&.
+The default is &"lax"&.
See also the &$lookup_dnssec_authenticated$& variable.
&*Note*&: Under versions of OpenSSL preceding 1.1.1,
when a list of more than one
file is used for &%tls_certificate%&, this variable is not reliable.
+.new
+The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
+.wen
.vitem &$tls_in_peercert$&
.vindex "&$tls_in_peercert$&"
commands are acceptable.
When used, the pipelining saves on roundtrip times.
+See also the &%hosts_pipe_connect%& smtp transport option.
+
Currently the option name &"X_PIPE_CONNECT"& is used.
.wen
&*Note*&: Under versions of OpenSSL preceding 1.1.1,
when a list of more than one
file is used, the &$tls_in_ourcert$& variable is unreliable.
-
-&*Note*&: OCSP stapling is not usable under OpenSSL
-when a list of more than one file is used.
+.new
+The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
+.wen
If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
if the OpenSSL build supports TLS extensions and the TLS client sends the
The value of this option is expanded and indicates the source of DH parameters
to be used by Exim.
-&*Note: The Exim Maintainers strongly recommend using a filename with site-generated
+.new
+This option is ignored for GnuTLS version 3.6.0 and later.
+The library manages parameter negotiation internally.
+.wen
+
+&*Note: The Exim Maintainers strongly recommend,
+for other TLS library versions,
+using a filename with site-generated
local DH parameters*&, which has been supported across all versions of Exim. The
other specific constants available are a fallback so that even when
"unconfigured", Exim can offer Perfect Forward Secrecy in older ciphersuites in TLS.
Certificate Authority.
Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
+.new
+The macro "_HAVE_TLS_OCSP" will be defined for those versions.
+.wen
.new
For OpenSSL 1.1.0 or later, and
for GnuTLS 3.5.6 or later the expanded value of this option can be a list
of files, to match a list given for the &%tls_certificate%& option.
The ordering of the two lists must match.
+.new
+The macro "_HAVE_TLS_OCSP_LIST" will be defined for those versions.
+.wen
.new
The file(s) should be in DER format,
-except for GnuTLS 3.6.3 or later when an optional filetype prefix
-can be used. The prefix must be one of "DER" or "PEM", followed by
+except for GnuTLS 3.6.3 or later
+or for OpenSSL,
+when an optional filetype prefix can be used.
+The prefix must be one of "DER" or "PEM", followed by
a single space. If one is used it sets the format for subsequent
files in the list; the initial format is DER.
-When a PEM format file is used it may contain multiple proofs,
-for multiple certificate chain element proofs under TLS1.3.
+If multiple proofs are wanted, for multiple chain elements
+(this only works under TLS1.3)
+they must be coded as a combined OCSP response.
+
+Although GnuTLS will accept PEM files with multiple separate
+PEM blobs (ie. separate OCSP responses), it sends them in the
+TLS Certificate record interleaved with the certificates of the chain;
+although a GnuTLS client is happy with that, an OpenSSL client is not.
.wen
.option tls_on_connect_ports main "string list" unset
unless you really, really know what you are doing. See also the generic
transport option of the same name.
-.option dnssec_request_domains routers "domain list&!!" unset
+.option dnssec_request_domains routers "domain list&!!" *
.cindex "MX record" "security"
.cindex "DNSSEC" "MX lookup"
.cindex "security" "MX lookup"
details.
-.option dnssec_request_domains smtp "domain list&!!" unset
+.option dnssec_request_domains smtp "domain list&!!" *
.cindex "MX record" "security"
.cindex "DNSSEC" "MX lookup"
.cindex "security" "MX lookup"
It also turns SMTP into a client-first protocol
so combines well with TCP Fast Open.
+See also the &%pipelining_connect_advertise_hosts%& main option.
+
Note:
When the facility is used, the transport &%helo_data%& option
will be expanded before the &$sending_ip_address$& variable
.code
USE_GNUTLS=yes
.endd
-in Local/Makefile, in addition to
-.code
-SUPPORT_TLS=yes
-.endd
-You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
+in Local/Makefile
+you must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
include files and libraries for GnuTLS can be found.
There are some differences in usage when using GnuTLS instead of OpenSSL:
If DANE is not usable, whether requested or not, and CA-anchored
verification evaluation is wanted, the above variables should be set appropriately.
-Currently the (router or transport options) &%dnssec_request_domains%& must be active and &%dnssec_require_domains%& is ignored.
+The router and transport option &%dnssec_request_domains%& must not be
+set to "never" and &%dnssec_require_domains%& is ignored.
If verification was successful using DANE then the "CV" item in the delivery log line will show as "CV=dane".
The name is placed in the variable &$event_name$& and the event action
expansion must check this, as it will be called for every possible event type.
+.new
The current list of events is:
+.wen
.display
&`dane:fail after transport `& per connection
&`msg:complete after main `& per message
&`tcp:close after transport `& per connection
&`tls:cert before both `& per certificate in verification chain
&`smtp:connect after transport `& per connection
+&`smtp:ehlo after transport `& per connection
.endd
New event types may be added in future.
&`msg:host:defer `& error string
&`tls:cert `& verification chain depth
&`smtp:connect `& smtp banner
+&`smtp:ehlo `& smtp ehlo response
.endd
The :defer events populate one extra variable: &$event_defer_errno$&.
git://git.exim.org / exim.git / blobdiff