tls_dh_min_bits smtp transport option

[users/jgh/exim.git] / doc / doc-docbook / spec.xfpt

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index b650fc39fa6d47d22f013fb99d0cde49802c05c1..78d5b0b183041375c924889e53989a2097e632cf 100644 (file)
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -45,7 +45,7 @@
 . the <bookinfo> element must also be updated for each new edition.
 . /////////////////////////////////////////////////////////////////////////////
 
 . the <bookinfo> element must also be updated for each new edition.
 . /////////////////////////////////////////////////////////////////////////////
 

-.set previousversion "4.75"
+.set previousversion "4.80"

 .set version "4.80"
 
 .set ACL "access control lists (ACLs)"
 .set version "4.80"
 
 .set ACL "access control lists (ACLs)"


@@ -1647,7 +1647,6 @@ architecture and operating system for itself, but the defaults can be
 overridden if necessary.
 
 
 overridden if necessary.
 
 

-.new

 .section "PCRE library" "SECTpcre"
 .cindex "PCRE library"
 Exim no longer has an embedded PCRE library as the vast majority of
 .section "PCRE library" "SECTpcre"
 .cindex "PCRE library"
 Exim no longer has an embedded PCRE library as the vast majority of


@@ -1662,7 +1661,6 @@ If your operating system has no
 PCRE support then you will need to obtain and build the current PCRE
 from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
 More information on PCRE is available at &url(http://www.pcre.org/).
 PCRE support then you will need to obtain and build the current PCRE
 from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
 More information on PCRE is available at &url(http://www.pcre.org/).

-.wen

 
 .section "DBM libraries" "SECTdb"
 .cindex "DBM libraries" "discussion of"
 
 .section "DBM libraries" "SECTdb"
 .cindex "DBM libraries" "discussion of"


@@ -1873,14 +1871,12 @@ SUPPORT_TLS=yes
 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
 TLS_INCLUDE=-I/usr/local/openssl/include/
 .endd
 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
 TLS_INCLUDE=-I/usr/local/openssl/include/
 .endd

-.new

 .cindex "pkg-config" "OpenSSL"
 If you have &'pkg-config'& available, then instead you can just use:
 .code
 SUPPORT_TLS=yes
 USE_OPENSSL_PC=openssl
 .endd
 .cindex "pkg-config" "OpenSSL"
 If you have &'pkg-config'& available, then instead you can just use:
 .code
 SUPPORT_TLS=yes
 USE_OPENSSL_PC=openssl
 .endd

-.wen

 .cindex "USE_GNUTLS"
 If GnuTLS is installed, you should set
 .code
 .cindex "USE_GNUTLS"
 If GnuTLS is installed, you should set
 .code


@@ -1896,7 +1892,6 @@ USE_GNUTLS=yes
 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
 TLS_INCLUDE=-I/usr/gnu/include
 .endd
 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
 TLS_INCLUDE=-I/usr/gnu/include
 .endd

-.new

 .cindex "pkg-config" "GnuTLS"
 If you have &'pkg-config'& available, then instead you can just use:
 .code
 .cindex "pkg-config" "GnuTLS"
 If you have &'pkg-config'& available, then instead you can just use:
 .code


@@ -1904,7 +1899,6 @@ SUPPORT_TLS=yes
 USE_GNUTLS=yes
 USE_GNUTLS_PC=gnutls
 .endd
 USE_GNUTLS=yes
 USE_GNUTLS_PC=gnutls
 .endd

-.wen

 
 You do not need to set TLS_INCLUDE if the relevant directory is already
 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
 
 You do not need to set TLS_INCLUDE if the relevant directory is already
 specified in INCLUDE. Details of how to configure Exim to make use of TLS are


@@ -2133,7 +2127,6 @@ files or libraries are required. When a lookup type is not included in the
 binary, attempts to configure Exim to use it cause run time configuration
 errors.
 
 binary, attempts to configure Exim to use it cause run time configuration
 errors.
 

-.new

 .cindex "pkg-config" "lookups"
 .cindex "pkg-config" "authenticators"
 Many systems now use a tool called &'pkg-config'& to encapsulate information
 .cindex "pkg-config" "lookups"
 .cindex "pkg-config" "authenticators"
 Many systems now use a tool called &'pkg-config'& to encapsulate information


@@ -2153,7 +2146,6 @@ AUTH_GSASL_PC=libgsasl
 AUTH_HEIMDAL_GSSAPI=yes
 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
 .endd
 AUTH_HEIMDAL_GSSAPI=yes
 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
 .endd

-.wen

 
 .cindex "Perl" "including support for"
 Exim can be linked with an embedded Perl interpreter, allowing Perl
 
 .cindex "Perl" "including support for"
 Exim can be linked with an embedded Perl interpreter, allowing Perl


@@ -2945,6 +2937,27 @@ use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
 if this is required. If the &%bi_command%& option is not set, calling Exim with
 &%-bi%& is a no-op.
 
 if this is required. If the &%bi_command%& option is not set, calling Exim with
 &%-bi%& is a no-op.
 

+.new
+.vitem &%-bI:help%&
+.oindex "&%-bI:help%&"
+.cindex "querying exim information"
+We shall provide various options starting &`-bI:`& for querying Exim for
+information.  The output of many of these will be intended for machine
+consumption.  This one is not.  The &%-bI:help%& option asks Exim for a
+synopsis of supported options beginning &`-bI:`&.  Use of any of these
+options shall cause Exim to exit after producing the requested output.
+
+.vitem &%-bI:sieve%&
+.oindex "&%-bI:sieve%&"
+.cindex "Sieve filter" "capabilities"
+This option causes Exim to emit an alphabetically sorted list of all supported
+Sieve protocol extensions on stdout, one per line.  This is anticipated to be
+useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
+&`SIEVE`& capability response line.  As the precise list may depend upon
+compile-time build options, which this option will adapt to, this is the only
+way to guarantee a correct response.
+.wen
+

 .vitem &%-bm%&
 .oindex "&%-bm%&"
 .cindex "local message reception"
 .vitem &%-bm%&
 .oindex "&%-bm%&"
 .cindex "local message reception"


@@ -2991,6 +3004,26 @@ The specified sender is treated as if it were given as the argument to the
 preference to the address taken from the message. The caller of Exim must be a
 trusted user for the sender of a message to be set in this way.
 
 preference to the address taken from the message. The caller of Exim must be a
 trusted user for the sender of a message to be set in this way.
 

+.vitem &%-bmalware%&&~<&'filename'&>
+.oindex "&%-bmalware%&"
+.cindex "testing", "malware"
+.cindex "malware scan test"
+This debugging option causes Exim to scan the given file,
+using the malware scanning framework.  The option of &%av_scanner%& influences
+this option, so if &%av_scanner%&'s value is dependent upon an expansion then
+the expansion should have defaults which apply to this invocation.  ACLs are
+not invoked, so if &%av_scanner%& references an ACL variable then that variable
+will never be populated and &%-bmalware%& will fail.
+
+Exim will have changed working directory before resolving the filename, so
+using fully qualified pathnames is advisable.  Exim will be running as the Exim
+user when it tries to open the file, rather than as the invoking user.
+This option requires admin privileges.
+
+The &%-bmalware%& option will not be extended to be more generally useful,
+there are better tools for file-scanning.  This option exists to help
+administrators verify their Exim and AV scanner configuration.
+

 .vitem &%-bnq%&
 .oindex "&%-bnq%&"
 .cindex "address qualification, suppressing"
 .vitem &%-bnq%&
 .oindex "&%-bnq%&"
 .cindex "address qualification, suppressing"


@@ -3038,6 +3071,12 @@ configuration file is output.
 If a list of configuration files was supplied, the value that is output here
 is the name of the file that was actually used.
 
 If a list of configuration files was supplied, the value that is output here
 is the name of the file that was actually used.
 

+.new
+.cindex "options" "hiding name of"
+If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
+name will not be output.
+.wen
+

 .cindex "daemon" "process id (pid)"
 .cindex "pid (process id)" "of daemon"
 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
 .cindex "daemon" "process id (pid)"
 .cindex "pid (process id)" "of daemon"
 If &%log_file_path%& or &%pid_file_path%& are given, the names of the


@@ -3251,26 +3290,6 @@ above concerning senders and qualification do not apply. In this situation,
 Exim behaves in exactly the same way as it does when receiving a message via
 the listening daemon.
 
 Exim behaves in exactly the same way as it does when receiving a message via
 the listening daemon.
 

-.vitem &%-bmalware%&&~<&'filename'&>
-.oindex "&%-bmalware%&"
-.cindex "testing", "malware"
-.cindex "malware scan test"
-This debugging option causes Exim to scan the given file,
-using the malware scanning framework.  The option of &%av_scanner%& influences
-this option, so if &%av_scanner%&'s value is dependent upon an expansion then
-the expansion should have defaults which apply to this invocation.  ACLs are
-not invoked, so if &%av_scanner%& references an ACL variable then that variable
-will never be populated and &%-bmalware%& will fail.
-
-Exim will have changed working directory before resolving the filename, so
-using fully qualified pathnames is advisable.  Exim will be running as the Exim
-user when it tries to open the file, rather than as the invoking user.
-This option requires admin privileges.
-
-The &%-bmalware%& option will not be extended to be more generally useful,
-there are better tools for file-scanning.  This option exists to help
-administrators verify their Exim and AV scanner configuration.
-

 .vitem &%-bt%&
 .oindex "&%-bt%&"
 .cindex "testing" "addresses"
 .vitem &%-bt%&
 .oindex "&%-bt%&"
 .cindex "testing" "addresses"


@@ -3919,9 +3938,9 @@ for that message.
 
 .vitem &%-n%&
 .oindex "&%-n%&"
 
 .vitem &%-n%&
 .oindex "&%-n%&"

-.cindex "Sendmail compatibility" "&%-n%& option ignored"
-This option is interpreted by Sendmail to mean &"no aliasing"&. It is ignored
-by Exim.
+This option is interpreted by Sendmail to mean &"no aliasing"&.
+For normal modes of operation, it is ignored by Exim.
+When combined with &%-bP%& it suppresses the name of an option from being output.

 
 .vitem &%-O%&&~<&'data'&>
 .oindex "&%-O%&"
 
 .vitem &%-O%&&~<&'data'&>
 .oindex "&%-O%&"


@@ -6026,16 +6045,16 @@ that it implements the details of the specific authentication mechanism,
 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
 when Exim offers authentication to clients; in the examples, this is only
 when TLS or SSL has been started, so to enable the authenticators you also
 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
 when Exim offers authentication to clients; in the examples, this is only
 when TLS or SSL has been started, so to enable the authenticators you also

-need to add support for TLS as described in &<<SECTdefconfmain>>&.
+need to add support for TLS as described in section &<<SECTdefconfmain>>&.

 
 The &%server_condition%& setting defines how to verify that the username and
 password are correct. In the examples it just produces an error message.
 To make the authenticators work, you can use a string expansion
 
 The &%server_condition%& setting defines how to verify that the username and
 password are correct. In the examples it just produces an error message.
 To make the authenticators work, you can use a string expansion

-expression like one of the examples in &<<CHAPplaintext>>&.
+expression like one of the examples in chapter &<<CHAPplaintext>>&.

 
 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
 
 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the

-usercode and password are in different positions.  &<<CHAPplaintext>>&
-covers both.
+usercode and password are in different positions.
+Chapter &<<CHAPplaintext>>& covers both.

 
 .ecindex IIDconfiwal
 
 
 .ecindex IIDconfiwal
 


@@ -6245,7 +6264,6 @@ using Berkeley DB versions 3 or 4, it opens existing databases for reading with
 the DB_UNKNOWN option. This enables it to handle any of the types of database
 that the library supports, and can be useful for accessing DBM files created by
 other applications. (For earlier DB versions, DB_HASH is always used.)
 the DB_UNKNOWN option. This enables it to handle any of the types of database
 that the library supports, and can be useful for accessing DBM files created by
 other applications. (For earlier DB versions, DB_HASH is always used.)

-.new

 .next
 .cindex "lookup" "dbmjz"
 .cindex "lookup" "dbm &-- embedded NULs"
 .next
 .cindex "lookup" "dbmjz"
 .cindex "lookup" "dbm &-- embedded NULs"


@@ -6257,7 +6275,6 @@ ASCII NUL characters to form the lookup key.  An example usage would be to
 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
 &(cram_md5)& authenticator.
 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
 &(cram_md5)& authenticator.

-.wen

 .next
 .cindex "lookup" "dbmnz"
 .cindex "lookup" "dbm &-- terminating zero"
 .next
 .cindex "lookup" "dbmnz"
 .cindex "lookup" "dbm &-- terminating zero"


@@ -6756,13 +6773,11 @@ is used on its own as the result. If the lookup does not succeed, the
 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
 &<<SECTforexpfai>>& for an explanation of what this means.
 
 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
 &<<SECTforexpfai>>& for an explanation of what this means.
 

-.new

 The supported DNS record types are A, CNAME, MX, NS, PTR, SPF, SRV, and TXT,
 and, when Exim is compiled with IPv6 support, AAAA (and A6 if that is also
 configured). If no type is given, TXT is assumed. When the type is PTR,
 the data can be an IP address, written as normal; inversion and the addition of
 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
 The supported DNS record types are A, CNAME, MX, NS, PTR, SPF, SRV, and TXT,
 and, when Exim is compiled with IPv6 support, AAAA (and A6 if that is also
 configured). If no type is given, TXT is assumed. When the type is PTR,
 the data can be an IP address, written as normal; inversion and the addition of
 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:

-.wen

 .code
 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
 .endd
 .code
 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
 .endd


@@ -6789,15 +6804,15 @@ white space is ignored.
 
 .cindex "TXT record" "in &(dnsdb)& lookup"
 .cindex "SPF record" "in &(dnsdb)& lookup"
 
 .cindex "TXT record" "in &(dnsdb)& lookup"
 .cindex "SPF record" "in &(dnsdb)& lookup"

-.new
-For TXT and SPF records with multiple items of data, only the first item is returned,
+For TXT records with multiple items of data, only the first item is returned,

 unless a separator for them is specified using a comma after the separator
 unless a separator for them is specified using a comma after the separator

-character followed immediately by the TXT/SPF record item separator. To concatenate
-items without a separator, use a semicolon instead.
-.wen
+character followed immediately by the TXT record item separator. To concatenate
+items without a separator, use a semicolon instead. For SPF records the
+default behaviour is to concatenate multiple items without using a separator.

 .code
 ${lookup dnsdb{>\n,: txt=a.b.example}}
 ${lookup dnsdb{>\n; txt=a.b.example}}
 .code
 ${lookup dnsdb{>\n,: txt=a.b.example}}
 ${lookup dnsdb{>\n; txt=a.b.example}}

+${lookup dnsdb{spf=example.org}}

 .endd
 It is permitted to specify a space as the separator character. Further
 white space is ignored.
 .endd
 It is permitted to specify a space as the separator character. Further
 white space is ignored.


@@ -9771,10 +9786,8 @@ This operator returns a somewhat random number which is less than the
 supplied number and is at least 0.  The quality of this randomness depends
 on how Exim was built; the values are not suitable for keying material.
 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
 supplied number and is at least 0.  The quality of this randomness depends
 on how Exim was built; the values are not suitable for keying material.
 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.

-.new

 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
 for versions of GnuTLS with that function.
 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
 for versions of GnuTLS with that function.

-.wen

 Otherwise, the implementation may be arc4random(), random() seeded by
 srandomdev() or srandom(), or a custom implementation even weaker than
 random().
 Otherwise, the implementation may be arc4random(), random() seeded by
 srandomdev() or srandom(), or a custom implementation even weaker than
 random().


@@ -10180,7 +10193,6 @@ string is lexically greater than the second string. For &%gt%& the comparison
 includes the case of letters, whereas for &%gti%& the comparison is
 case-independent.
 
 includes the case of letters, whereas for &%gti%& the comparison is
 case-independent.
 

-.new

 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
        &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
 .cindex "string" "comparison"
 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
        &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
 .cindex "string" "comparison"


@@ -10197,7 +10209,6 @@ ${if inlist{needle}{foo:needle:bar}}
 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
   ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
 .endd
 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
   ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
 .endd

-.wen

 
 .vitem &*isip&~{*&<&'string'&>&*}*&  &&&
        &*isip4&~{*&<&'string'&>&*}*& &&&
 
 .vitem &*isip&~{*&<&'string'&>&*}*&  &&&
        &*isip4&~{*&<&'string'&>&*}*& &&&


@@ -10309,12 +10320,10 @@ See &*match_local_part*&.
 
 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
 .cindex "&%match_ip%& expansion condition"
 
 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
 .cindex "&%match_ip%& expansion condition"

-.new

 This condition matches an IP address to a list of IP address patterns. It must
 be followed by two argument strings. The first (after expansion) must be an IP
 address or an empty string. The second (not expanded) is a restricted host
 list that can match only an IP address, not a host name. For example:
 This condition matches an IP address to a list of IP address patterns. It must
 be followed by two argument strings. The first (after expansion) must be an IP
 address or an empty string. The second (not expanded) is a restricted host
 list that can match only an IP address, not a host name. For example:

-.wen

 .code
 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
 .endd
 .code
 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
 .endd


@@ -10360,10 +10369,8 @@ just as easy to use the fact that a lookup is itself a condition, and write:
 .endd
 .endlist ilist
 
 .endd
 .endlist ilist
 

-.new

 Note that <&'string2'&> is not itself subject to string expansion, unless
 Exim was built with the EXPAND_LISTMATCH_RHS option.
 Note that <&'string2'&> is not itself subject to string expansion, unless
 Exim was built with the EXPAND_LISTMATCH_RHS option.

-.wen

 
 Consult section &<<SECThoslispatip>>& for further details of these patterns.
 
 
 Consult section &<<SECThoslispatip>>& for further details of these patterns.
 


@@ -10392,10 +10399,8 @@ item can be used, as in all address lists, to cause subsequent items to
 have their local parts matched casefully. Domains are always matched
 caselessly.
 
 have their local parts matched casefully. Domains are always matched
 caselessly.
 

-.new

 Note that <&'string2'&> is not itself subject to string expansion, unless
 Exim was built with the EXPAND_LISTMATCH_RHS option.
 Note that <&'string2'&> is not itself subject to string expansion, unless
 Exim was built with the EXPAND_LISTMATCH_RHS option.

-.wen

 
 &*Note*&: Host lists are &'not'& supported in this way. This is because
 hosts have two identities: a name and an IP address, and it is not clear
 
 &*Note*&: Host lists are &'not'& supported in this way. This is because
 hosts have two identities: a name and an IP address, and it is not clear


@@ -10742,14 +10747,12 @@ is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
 negative response to an AUTH command, including (for example) an attempt to use
 an undefined mechanism.
 
 negative response to an AUTH command, including (for example) an attempt to use
 an undefined mechanism.
 

-.new

 .vitem &$av_failed$&
 .cindex "content scanning" "AV scanner failure"
 This variable is available when Exim is compiled with the content-scanning
 extension. It is set to &"0"& by default, but will be set to &"1"& if any
 problem occurs with the virus scanner (specified by &%av_scanner%&) during
 the ACL malware condition.
 .vitem &$av_failed$&
 .cindex "content scanning" "AV scanner failure"
 This variable is available when Exim is compiled with the content-scanning
 extension. It is set to &"0"& by default, but will be set to &"1"& if any
 problem occurs with the virus scanner (specified by &%av_scanner%&) during
 the ACL malware condition.

-.wen

 
 .vitem &$body_linecount$&
 .cindex "message body" "line count"
 
 .vitem &$body_linecount$&
 .cindex "message body" "line count"


@@ -11882,7 +11885,6 @@ command in a filter file. Its use is explained in the description of that
 command, which can be found in the separate document entitled &'Exim's
 interfaces to mail filtering'&.
 
 command, which can be found in the separate document entitled &'Exim's
 interfaces to mail filtering'&.
 

-.new

 .vitem &$tls_bits$&
 .vindex "&$tls_bits$&"
 Contains an approximation of the TLS cipher's bit-strength; the meaning of
 .vitem &$tls_bits$&
 .vindex "&$tls_bits$&"
 Contains an approximation of the TLS cipher's bit-strength; the meaning of


@@ -11890,7 +11892,6 @@ this depends upon the TLS implementation used.
 If TLS has not been negotiated, the value will be 0.
 The value of this is automatically fed into the Cyrus SASL authenticator
 when acting as a server, to specify the "external SSF" (a SASL term).
 If TLS has not been negotiated, the value will be 0.
 The value of this is automatically fed into the Cyrus SASL authenticator
 when acting as a server, to specify the "external SSF" (a SASL term).

-.wen

 
 .vitem &$tls_certificate_verified$&
 .vindex "&$tls_certificate_verified$&"
 
 .vitem &$tls_certificate_verified$&
 .vindex "&$tls_certificate_verified$&"


@@ -11922,7 +11923,6 @@ the value of the Distinguished Name of the certificate is made available in the
 value is retained during message delivery, except during outbound SMTP
 deliveries.
 
 value is retained during message delivery, except during outbound SMTP
 deliveries.
 

-.new

 .vitem &$tls_sni$&
 .vindex "&$tls_sni$&"
 .cindex "TLS" "Server Name Indication"
 .vitem &$tls_sni$&
 .vindex "&$tls_sni$&"
 .cindex "TLS" "Server Name Indication"


@@ -11937,7 +11937,6 @@ used) to the client, based upon the value of the SNI extension.
 The value will be retained for the lifetime of the message.  During outbound
 SMTP deliveries, it reflects the value of the &%tls_sni%& option on
 the transport.
 The value will be retained for the lifetime of the message.  During outbound
 SMTP deliveries, it reflects the value of the &%tls_sni%& option on
 the transport.

-.wen

 
 .vitem &$tod_bsdinbox$&
 .vindex "&$tod_bsdinbox$&"
 
 .vitem &$tod_bsdinbox$&
 .vindex "&$tod_bsdinbox$&"


@@ -12692,6 +12691,7 @@ listed in more than one group.
 .row &%tls_advertise_hosts%&         "advertise TLS to these hosts"
 .row &%tls_certificate%&             "location of server certificate"
 .row &%tls_crl%&                     "certificate revocation list"
 .row &%tls_advertise_hosts%&         "advertise TLS to these hosts"
 .row &%tls_certificate%&             "location of server certificate"
 .row &%tls_crl%&                     "certificate revocation list"

+.row &%tls_dh_max_bits%&             "clamp D-H bit count suggestion"

 .row &%tls_dhparam%&                 "DH parameters for server"
 .row &%tls_on_connect_ports%&        "specify SSMTP (SMTPS) ports"
 .row &%tls_privatekey%&              "location of server private key"
 .row &%tls_dhparam%&                 "DH parameters for server"
 .row &%tls_on_connect_ports%&        "specify SSMTP (SMTPS) ports"
 .row &%tls_privatekey%&              "location of server private key"


@@ -12880,7 +12880,6 @@ See also the &'Policy controls'& section above.
 Those options that undergo string expansion before use are marked with
 &dagger;.
 
 Those options that undergo string expansion before use are marked with
 &dagger;.
 

-.new

 .option accept_8bitmime main boolean true
 .cindex "8BITMIME"
 .cindex "8-bit characters"
 .option accept_8bitmime main boolean true
 .cindex "8BITMIME"
 .cindex "8-bit characters"


@@ -12896,7 +12895,6 @@ A more detailed analysis of the issues is provided by Dan Bernstein:
 .display
 &url(http://cr.yp.to/smtp/8bitmime.html)
 .endd
 .display
 &url(http://cr.yp.to/smtp/8bitmime.html)
 .endd

-.wen

 
 .option acl_not_smtp main string&!! unset
 .cindex "&ACL;" "for non-SMTP messages"
 
 .option acl_not_smtp main string&!! unset
 .cindex "&ACL;" "for non-SMTP messages"


@@ -13478,7 +13476,6 @@ to set in them.
 See &%dns_retrans%& above.
 
 
 See &%dns_retrans%& above.
 
 

-.new

 .option dns_use_edns0 main integer -1
 .cindex "DNS" "resolver options"
 .cindex "DNS" "EDNS0"
 .option dns_use_edns0 main integer -1
 .cindex "DNS" "resolver options"
 .cindex "DNS" "EDNS0"


@@ -13488,7 +13485,6 @@ the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
 on.
 
 If the resolver library does not support EDNS0 then this option has no effect.
 on.
 
 If the resolver library does not support EDNS0 then this option has no effect.

-.wen

 
 
 .option drop_cr main boolean false
 
 
 .option drop_cr main boolean false


@@ -14382,7 +14378,7 @@ harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
 transport driver.
 
 
 transport driver.
 
 

-.option openssl_options main "string list" unset
+.option openssl_options main "string list" "+no_sslv2"

 .cindex "OpenSSL "compatibility options"
 This option allows an administrator to adjust the SSL options applied
 by OpenSSL to connections.  It is given as a space-separated list of items,
 .cindex "OpenSSL "compatibility options"
 This option allows an administrator to adjust the SSL options applied
 by OpenSSL to connections.  It is given as a space-separated list of items,


@@ -14402,12 +14398,10 @@ yourself in the foot in various unpleasant ways.  This option should not be
 adjusted lightly.  An unrecognised item will be detected at startup, by
 invoking Exim with the &%-bV%& flag.
 
 adjusted lightly.  An unrecognised item will be detected at startup, by
 invoking Exim with the &%-bV%& flag.
 

-.new

 Historical note: prior to release 4.80, Exim defaulted this value to
 "+dont_insert_empty_fragments", which may still be needed for compatibility
 with some clients, but which lowers security by increasing exposure to
 some now infamous attacks.
 Historical note: prior to release 4.80, Exim defaulted this value to
 "+dont_insert_empty_fragments", which may still be needed for compatibility
 with some clients, but which lowers security by increasing exposure to
 some now infamous attacks.

-.wen

 
 An example:
 .code
 
 An example:
 .code


@@ -15660,12 +15654,10 @@ receiving incoming messages as a server. If you want to supply certificates for
 use when sending messages as a client, you must set the &%tls_certificate%&
 option in the relevant &(smtp)& transport.
 
 use when sending messages as a client, you must set the &%tls_certificate%&
 option in the relevant &(smtp)& transport.
 

-.new

 If the option contains &$tls_sni$& and Exim is built against OpenSSL, then
 if the OpenSSL build supports TLS extensions and the TLS client sends the
 Server Name Indication extension, then this option and others documented in
 &<<SECTtlssni>>& will be re-expanded.
 If the option contains &$tls_sni$& and Exim is built against OpenSSL, then
 if the OpenSSL build supports TLS extensions and the TLS client sends the
 Server Name Indication extension, then this option and others documented in
 &<<SECTtlssni>>& will be re-expanded.

-.wen

 
 .option tls_crl main string&!! unset
 .cindex "TLS" "server certificate revocation list"
 
 .option tls_crl main string&!! unset
 .cindex "TLS" "server certificate revocation list"


@@ -15673,17 +15665,68 @@ Server Name Indication extension, then this option and others documented in
 This option specifies a certificate revocation list. The expanded value must
 be the name of a file that contains a CRL in PEM format.
 
 This option specifies a certificate revocation list. The expanded value must
 be the name of a file that contains a CRL in PEM format.
 

-.new

 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.

-.wen
+
+
+.option tls_dh_max_bits main integer 2236
+.cindex "TLS" "D-H bit count"
+The number of bits used for Diffie-Hellman key-exchange may be suggested by
+the chosen TLS library.  That value might prove to be too high for
+interoperability.  This option provides a maximum clamp on the value
+suggested, trading off security for interoperability.
+
+The value must be at least 1024.
+
+The value 2236 was chosen because, at time of adding the option, it was the
+hard-coded maximum value supported by the NSS cryptographic library, as used
+by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
+
+If you prefer more security and are willing to break some clients, raise this
+number.
+
+Note that the value passed to GnuTLS for *generating* a new prime may be a
+little less than this figure, because GnuTLS is inexact and may produce a
+larger prime than requested.

 
 
 .option tls_dhparam main string&!! unset
 .cindex "TLS" "D-H parameters for server"
 
 
 .option tls_dhparam main string&!! unset
 .cindex "TLS" "D-H parameters for server"

-The value of this option is expanded, and must then be the absolute path to
-a file which contains the server's DH parameter values.
-This is used only for OpenSSL. When Exim is linked with GnuTLS, this option is
-ignored. See section &<<SECTopenvsgnu>>& for further details.
+The value of this option is expanded and indicates the source of DH parameters
+to be used by Exim.
+
+If it is a filename starting with a &`/`&, then it names a file from which DH
+parameters should be loaded.  If the file exists, it should hold a PEM-encoded
+PKCS#3 representation of the DH prime.  If the file does not exist, for
+OpenSSL it is an error.  For GnuTLS, Exim will attempt to create the file and
+fill it with a generated DH prime.  For OpenSSL, if the DH bit-count from
+loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
+and treated as though the &%tls_dhparam%& were set to "none".
+
+If this option expands to the string "none", then no DH parameters will be
+loaded by Exim.
+
+If this option expands to the string "historic" and Exim is using GnuTLS, then
+Exim will attempt to load a file from inside the spool directory.  If the file
+does not exist, Exim will attempt to create it.
+See section &<<SECTgnutlsparam>>& for further details.
+
+If Exim is using OpenSSL and this option is empty or unset, then Exim will load
+a default DH prime; the default is the 2048 bit prime described in section
+2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
+in IKE is assigned number 23.
+
+Otherwise, the option must expand to the name used by Exim for any of a number
+of DH primes specified in RFC 2409, RFC 3526 and RFC 5114.  As names, Exim uses
+"ike" followed by the number used by IKE, of "default" which corresponds to
+"ike23".
+
+The available primes are:
+&`ike1`&, &`ike2`&, &`ike5`&,
+&`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
+&`ike22`&, &`ike23`& (aka &`default`&) and &`ike24`&.
+
+Some of these will be too small to be accepted by clients.
+Some may be too large to be accepted by clients.

 
 
 .option tls_on_connect_ports main "string list" unset
 
 
 .option tls_on_connect_ports main "string list" unset


@@ -15702,9 +15745,7 @@ the expansion is forced to fail, or the result is an empty string, the private
 key is assumed to be in the same file as the server's certificates. See chapter
 &<<CHAPTLS>>& for further details.
 
 key is assumed to be in the same file as the server's certificates. See chapter
 &<<CHAPTLS>>& for further details.
 

-.new

 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.

-.wen

 
 
 .option tls_remember_esmtp main boolean false
 
 
 .option tls_remember_esmtp main boolean false


@@ -15752,9 +15793,7 @@ connecting clients, defining the list of accepted certificate authorities.
 Thus the values defined should be considered public data.  To avoid this,
 use OpenSSL with a directory.
 
 Thus the values defined should be considered public data.  To avoid this,
 use OpenSSL with a directory.
 

-.new

 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.

-.wen

 
 
 .option tls_verify_hosts main "host list&!!" unset
 
 
 .option tls_verify_hosts main "host list&!!" unset


@@ -17076,6 +17115,38 @@ look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
 case routing fails.
 
 
 case routing fails.
 
 

+.section "Declining addresses by dnslookup" "SECTdnslookupdecline"
+.cindex "&(dnslookup)& router" "declines"
+There are a few cases where a &(dnslookup)& router will decline to accept
+an address; if such a router is expected to handle "all remaining non-local
+domains", then it is important to set &%no_more%&.
+
+Reasons for a &(dnslookup)& router to decline currently include:
+.ilist
+The domain does not exist in DNS
+.next
+The domain exists but the MX record's host part is just "."; this is a common
+convention (borrowed from SRV) used to indicate that there is no such service
+for this domain and to not fall back to trying A/AAAA records.
+.next
+Ditto, but for SRV records, when &%check_srv%& is set on this router.
+.next
+MX record points to a non-existent host.
+.next
+MX record points to an IP address and the main section option
+&%allow_mx_to_ip%& is not set.
+.next
+MX records exist and point to valid hosts, but all hosts resolve only to
+addresses blocked by the &%ignore_target_hosts%& generic option on this router.
+.next
+The domain is not syntactically valid (see also &%allow_utf8_domains%& and
+&%dns_check_names_pattern%& for handling one variant of this)
+.next
+&%check_secondary_mx%& is set on this router but the local host can
+not be found in the MX records (see below)
+.endlist
+
+

 
 
 .section "Private options for dnslookup" "SECID118"
 
 
 .section "Private options for dnslookup" "SECID118"


@@ -20194,7 +20265,6 @@ This option applies only to deliveries in maildir format, and is described in
 section &<<SECTmaildirdelivery>>& below.
 
 
 section &<<SECTmaildirdelivery>>& below.
 
 

-.new

 .option maildir_use_size_file appendfile&!! boolean false
 .cindex "maildir format" "&_maildirsize_& file"
 The result of string expansion for this option must be a valid boolean value.
 .option maildir_use_size_file appendfile&!! boolean false
 .cindex "maildir format" "&_maildirsize_& file"
 The result of string expansion for this option must be a valid boolean value.


@@ -20203,7 +20273,6 @@ creates a &_maildirsize_& file in a maildir if one does not exist, taking the
 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
 value is zero. See &%maildir_quota_directory_regex%& above and section
 &<<SECTmaildirdelivery>>& below for further details.
 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
 value is zero. See &%maildir_quota_directory_regex%& above and section
 &<<SECTmaildirdelivery>>& below for further details.

-.wen

 
 .option maildirfolder_create_regex appendfile string unset
 .cindex "maildir format" "&_maildirfolder_& file"
 
 .option maildirfolder_create_regex appendfile string unset
 .cindex "maildir format" "&_maildirfolder_& file"


@@ -22295,12 +22364,10 @@ protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
 deliveries into closed message stores. Exim also has support for running LMTP
 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
 
 deliveries into closed message stores. Exim also has support for running LMTP
 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
 

-.new

 If this option is set to &"smtps"&, the default vaule for the &%port%& option
 changes to &"smtps"&, and the transport initiates TLS immediately after
 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
 The Internet standards bodies strongly discourage use of this mode.
 If this option is set to &"smtps"&, the default vaule for the &%port%& option
 changes to &"smtps"&, and the transport initiates TLS immediately after
 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
 The Internet standards bodies strongly discourage use of this mode.

-.wen

 
 
 .option retry_include_ip_address smtp boolean true
 
 
 .option retry_include_ip_address smtp boolean true


@@ -22384,6 +22451,19 @@ This option specifies a certificate revocation list. The expanded value must
 be the name of a file that contains a CRL in PEM format.
 
 
 be the name of a file that contains a CRL in PEM format.
 
 

+.new
+.option tls_dh_min_bits smtp integer 1024
+.cindex "TLS" "Diffie-Hellman minimum acceptable size"
+When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
+key agreement is negotiated, the server will provide a large prime number
+for use.  This option establishes the minimum acceptable size of that number.
+If the parameter offered by the server is too small, then the TLS handshake
+will fail.
+
+Only supported when using GnuTLS.
+.wen
+
+

 .option tls_privatekey smtp string&!! unset
 .cindex "TLS" "client private key, location of"
 .vindex "&$host$&"
 .option tls_privatekey smtp string&!! unset
 .cindex "TLS" "client private key, location of"
 .vindex "&$host$&"


@@ -22413,7 +22493,6 @@ ciphers is a preference order.
 
 
 
 
 
 

-.new

 .option tls_sni smtp string&!! unset
 .cindex "TLS" "Server Name Indication"
 .vindex "&$tls_sni$&"
 .option tls_sni smtp string&!! unset
 .cindex "TLS" "Server Name Indication"
 .vindex "&$tls_sni$&"


@@ -22424,8 +22503,9 @@ certificate and private key for the session.
 
 See &<<SECTtlssni>>& for more information.
 
 
 See &<<SECTtlssni>>& for more information.
 

-OpenSSL only, also requiring a build of OpenSSL that supports TLS extensions.
-.wen
+Note that for OpenSSL, this feature requires a build of OpenSSL that supports
+TLS extensions.
+

 
 
 
 
 
 


@@ -23604,18 +23684,15 @@ included by setting
 .code
 AUTH_CRAM_MD5=yes
 AUTH_CYRUS_SASL=yes
 .code
 AUTH_CRAM_MD5=yes
 AUTH_CYRUS_SASL=yes

-.new

 AUTH_DOVECOT=yes
 AUTH_GSASL=yes
 AUTH_HEIMDAL_GSSAPI=yes
 AUTH_DOVECOT=yes
 AUTH_GSASL=yes
 AUTH_HEIMDAL_GSSAPI=yes

-.wen

 AUTH_PLAINTEXT=yes
 AUTH_SPA=yes
 .endd
 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
 authentication mechanism (RFC 2195), and the second provides an interface to
 the Cyrus SASL authentication library.
 AUTH_PLAINTEXT=yes
 AUTH_SPA=yes
 .endd
 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
 authentication mechanism (RFC 2195), and the second provides an interface to
 the Cyrus SASL authentication library.

-.new

 The third is an interface to Dovecot's authentication system, delegating the
 work via a socket interface.
 The fourth provides an interface to the GNU SASL authentication library, which
 The third is an interface to Dovecot's authentication system, delegating the
 work via a socket interface.
 The fourth provides an interface to the GNU SASL authentication library, which


@@ -23626,7 +23703,6 @@ The sixth can be configured to support
 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
 not formally documented, but used by several MUAs. The seventh authenticator
 supports Microsoft's &'Secure Password Authentication'& mechanism.
 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
 not formally documented, but used by several MUAs. The seventh authenticator
 supports Microsoft's &'Secure Password Authentication'& mechanism.

-.wen

 
 The authenticators are configured using the same syntax as other drivers (see
 section &<<SECTfordricon>>&). If no authenticators are required, no
 
 The authenticators are configured using the same syntax as other drivers (see
 section &<<SECTfordricon>>&). If no authenticators are required, no


@@ -23658,7 +23734,6 @@ The remainder of this chapter covers the generic options for the
 authenticators, followed by general discussion of the way authentication works
 in Exim.
 
 authenticators, followed by general discussion of the way authentication works
 in Exim.
 

-.new

 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
 per-mechanism basis.  Please read carefully to determine which variables hold
 account labels such as usercodes and which hold passwords or other
 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
 per-mechanism basis.  Please read carefully to determine which variables hold
 account labels such as usercodes and which hold passwords or other


@@ -23680,7 +23755,6 @@ A &'realm'& is a text string, typically a domain name, presented by a server
 to a client to help it select an account and credentials to use.  In some
 mechanisms, the client and server provably agree on the realm, but clients
 typically can not treat the realm as secure data to be blindly trusted.
 to a client to help it select an account and credentials to use.  In some
 mechanisms, the client and server provably agree on the realm, but clients
 typically can not treat the realm as secure data to be blindly trusted.

-.wen

 
 
 
 
 
 


@@ -23728,10 +23802,8 @@ This option must be set for a &%plaintext%& server authenticator, where it
 is used directly to control authentication. See section &<<SECTplainserver>>&
 for details.
 
 is used directly to control authentication. See section &<<SECTplainserver>>&
 for details.
 

-.new

 For the &(gsasl)& authenticator, this option is required for various
 mechanisms; see chapter &<<CHAPgsasl>>& for details.
 For the &(gsasl)& authenticator, this option is required for various
 mechanisms; see chapter &<<CHAPgsasl>>& for details.

-.wen

 
 For the other authenticators, &%server_condition%& can be used as an additional
 authentication or authorization mechanism that is applied after the other
 
 For the other authenticators, &%server_condition%& can be used as an additional
 authentication or authorization mechanism that is applied after the other


@@ -24338,7 +24410,6 @@ lookup_cram:
 Note that this expansion explicitly forces failure if the lookup fails
 because &$auth1$& contains an unknown user name.
 
 Note that this expansion explicitly forces failure if the lookup fails
 because &$auth1$& contains an unknown user name.
 

-.new

 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
 using the relevant libraries, you need to know the realm to specify in the
 lookup and then ask for the &"userPassword"& attribute for that user in that
 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
 using the relevant libraries, you need to know the realm to specify in the
 lookup and then ask for the &"userPassword"& attribute for that user in that


@@ -24351,7 +24422,6 @@ cyrusless_crammd5:
                   dbmjz{/etc/sasldb2}}
   server_set_id = $auth1
 .endd
                   dbmjz{/etc/sasldb2}}
   server_set_id = $auth1
 .endd

-.wen

 
 .section "Using cram_md5 as a client" "SECID177"
 .cindex "options" "&(cram_md5)& authenticator (client)"
 
 .section "Using cram_md5 as a client" "SECID177"
 .cindex "options" "&(cram_md5)& authenticator (client)"


@@ -24426,7 +24496,7 @@ Kerberos, note that because of limitations in the GSSAPI interface,
 changing the server keytab might need to be communicated down to the Kerberos
 layer independently. The mechanism for doing so is dependent upon the Kerberos
 implementation.
 changing the server keytab might need to be communicated down to the Kerberos
 layer independently. The mechanism for doing so is dependent upon the Kerberos
 implementation.

-.new
+

 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
 may be set to point to an alternative keytab file. Exim will pass this
 variable through from its own inherited environment when started as root or the
 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
 may be set to point to an alternative keytab file. Exim will pass this
 variable through from its own inherited environment when started as root or the


@@ -24435,7 +24505,6 @@ With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
 environment variable.  In practice, for those releases, the Cyrus authenticator
 is not a suitable interface for GSSAPI (Kerberos) support.  Instead, consider
 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
 environment variable.  In practice, for those releases, the Cyrus authenticator
 is not a suitable interface for GSSAPI (Kerberos) support.  Instead, consider
 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&

-.wen

 
 
 .section "Using cyrus_sasl as a server" "SECID178"
 
 
 .section "Using cyrus_sasl as a server" "SECID178"


@@ -24466,10 +24535,8 @@ sasl:
   server_set_id = $auth1
 .endd
 
   server_set_id = $auth1
 .endd
 

-.new

 .option server_realm cyrus_sasl string&!! unset
 This specifies the SASL realm that the server claims to be in.
 .option server_realm cyrus_sasl string&!! unset
 This specifies the SASL realm that the server claims to be in.

-.wen

 
 
 .option server_service cyrus_sasl string &`smtp`&
 
 
 .option server_service cyrus_sasl string &`smtp`&


@@ -24542,7 +24609,6 @@ who authenticated is placed in &$auth1$&.
 
 . ////////////////////////////////////////////////////////////////////////////
 . ////////////////////////////////////////////////////////////////////////////
 
 . ////////////////////////////////////////////////////////////////////////////
 . ////////////////////////////////////////////////////////////////////////////

-.new

 .chapter "The gsasl authenticator" "CHAPgsasl"
 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
 .chapter "The gsasl authenticator" "CHAPgsasl"
 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"


@@ -24563,7 +24629,7 @@ made that any particular new authentication mechanism will be supported
 without code changes in Exim.
 
 
 without code changes in Exim.
 
 

-.option server_channelbinding gsasl bool false
+.option server_channelbinding gsasl boolean false

 Some authentication mechanisms are able to use external context at both ends
 of the session to bind the authentication to that context, and fail the
 authentication process if that context differs.  Specifically, some TLS
 Some authentication mechanisms are able to use external context at both ends
 of the session to bind the authentication to that context, and fail the
 authentication process if that context differs.  Specifically, some TLS


@@ -24697,12 +24763,10 @@ gsasl_cyrusless_crammd5:
   server_condition = yes
 .endd
 
   server_condition = yes
 .endd
 

-.wen

 
 . ////////////////////////////////////////////////////////////////////////////
 . ////////////////////////////////////////////////////////////////////////////
 
 
 . ////////////////////////////////////////////////////////////////////////////
 . ////////////////////////////////////////////////////////////////////////////
 

-.new

 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"


@@ -24749,7 +24813,6 @@ authentication.  If that was empty, this will also be set to the
 GSS Display Name.
 .endlist
 
 GSS Display Name.
 .endlist
 

-.wen

 
 . ////////////////////////////////////////////////////////////////////////////
 . ////////////////////////////////////////////////////////////////////////////
 
 . ////////////////////////////////////////////////////////////////////////////
 . ////////////////////////////////////////////////////////////////////////////


@@ -24935,9 +24998,7 @@ There are some differences in usage when using GnuTLS instead of OpenSSL:
 The &%tls_verify_certificates%& option must contain the name of a file, not the
 name of a directory (for OpenSSL it can be either).
 .next
 The &%tls_verify_certificates%& option must contain the name of a file, not the
 name of a directory (for OpenSSL it can be either).
 .next

-The &%tls_dhparam%& option is ignored, because early versions of GnuTLS had no
-facility for varying its Diffie-Hellman parameters. I understand that this has
-changed, but Exim has not been updated to provide this facility.
+The default value for &%tls_dhparam%& differs for historical reasons.

 .next
 .vindex "&$tls_peerdn$&"
 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
 .next
 .vindex "&$tls_peerdn$&"
 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for


@@ -24945,27 +25006,38 @@ separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
 affects the value of the &$tls_peerdn$& variable.
 .next
 OpenSSL identifies cipher suites using hyphens as separators, for example:
 affects the value of the &$tls_peerdn$& variable.
 .next
 OpenSSL identifies cipher suites using hyphens as separators, for example:

-DES-CBC3-SHA. GnuTLS uses underscores, for example: RSA_ARCFOUR_SHA. What is
-more, OpenSSL complains if underscores are present in a cipher list. To make
-life simpler, Exim changes underscores to hyphens for OpenSSL and hyphens to
-underscores for GnuTLS when processing lists of cipher suites in the
+DES-CBC3-SHA. GnuTLS historically used underscores, for example:
+RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
+in a cipher list. To make life simpler, Exim changes underscores to hyphens
+for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
+to handle its own older variants) when processing lists of cipher suites in the

 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
 option).
 .next
 The &%tls_require_ciphers%& options operate differently, as described in the
 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
 option).
 .next
 The &%tls_require_ciphers%& options operate differently, as described in the
 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.

+.next

 .new
 .new

+The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
+When using OpenSSL, this option is ignored.
+(If an API is found to let OpenSSL be configured in this way,
+let the Exim Maintainers know and we'll likely use it).
+.wen

 .next
 Some other recently added features may only be available in one or the other.
 This should be documented with the feature.  If the documentation does not
 explicitly state that the feature is infeasible in the other TLS
 implementation, then patches are welcome.
 .next
 Some other recently added features may only be available in one or the other.
 This should be documented with the feature.  If the documentation does not
 explicitly state that the feature is infeasible in the other TLS
 implementation, then patches are welcome.

-.wen

 .endlist
 
 
 .endlist
 
 

-.section "GnuTLS parameter computation" "SECID181"
-.new
+.section "GnuTLS parameter computation" "SECTgnutlsparam"
+This section only applies if &%tls_dhparam%& is set to &`historic`& or to
+an explicit path; if the latter, then the text about generation still applies,
+but not the chosen filename.
+By default, as of Exim 4.80 a hard-coded D-H prime is used.
+See the documentation of &%tls_dhparam%& for more information.
+

 GnuTLS uses D-H parameters that may take a substantial amount of time
 to compute. It is unreasonable to re-compute them for every TLS session.
 Therefore, Exim keeps this data in a file in its spool directory, called
 GnuTLS uses D-H parameters that may take a substantial amount of time
 to compute. It is unreasonable to re-compute them for every TLS session.
 Therefore, Exim keeps this data in a file in its spool directory, called


@@ -24981,6 +25053,10 @@ place, new Exim processes immediately start using it.
 
 For maximum security, the parameters that are stored in this file should be
 recalculated periodically, the frequency depending on your paranoia level.
 
 For maximum security, the parameters that are stored in this file should be
 recalculated periodically, the frequency depending on your paranoia level.

+If you are avoiding using the fixed D-H primes published in RFCs, then you
+are concerned about some advanced attacks and will wish to do this; if you do
+not regenerate then you might as well stick to the standard primes.
+

 Arranging this is easy in principle; just delete the file when you want new
 values to be computed. However, there may be a problem. The calculation of new
 parameters needs random numbers, and these are obtained from &_/dev/random_&.
 Arranging this is easy in principle; just delete the file when you want new
 values to be computed. However, there may be a problem. The calculation of new
 parameters needs random numbers, and these are obtained from &_/dev/random_&.


@@ -24998,14 +25074,18 @@ and letting Exim re-create it, you can generate new parameters using
 renaming. The relevant commands are something like this:
 .code
 # ls
 renaming. The relevant commands are something like this:
 .code
 # ls

-[ look for file; assume gnutls-params-1024 is the most recent ]
+[ look for file; assume gnutls-params-2236 is the most recent ]

 # rm -f new-params
 # touch new-params
 # chown exim:exim new-params
 # chmod 0600 new-params
 # rm -f new-params
 # touch new-params
 # chown exim:exim new-params
 # chmod 0600 new-params

-# certtool --generate-dh-params --bits 1024 >>new-params
+# certtool --generate-dh-params --bits 2236 >>new-params
+# openssl dhparam -noout -text -in new-params | head
+[ check the first line, make sure it's not more than 2236;
+  if it is, then go back to the start ("rm") and repeat
+  until the size generated is at most the size requested ]

 # chmod 0400 new-params
 # chmod 0400 new-params

-# mv new-params gnutls-params-1024
+# mv new-params gnutls-params-2236

 .endd
 If Exim never has to generate the parameters itself, the possibility of
 stalling is removed.
 .endd
 If Exim never has to generate the parameters itself, the possibility of
 stalling is removed.


@@ -25014,11 +25094,24 @@ The filename changed in Exim 4.80, to gain the -bits suffix.  The value which
 Exim will choose depends upon the version of GnuTLS in use.  For older GnuTLS,
 the value remains hard-coded in Exim as 1024.  As of GnuTLS 2.12.x, there is
 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
 Exim will choose depends upon the version of GnuTLS in use.  For older GnuTLS,
 the value remains hard-coded in Exim as 1024.  As of GnuTLS 2.12.x, there is
 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,

-and Exim does so.  Exim thus removes itself from the policy decision, and the
-filename and bits used change as the GnuTLS maintainers change the value for
-their parameter &`GNUTLS_SEC_PARAM_NORMAL`&.  At the time of writing, this
-gives 2432 bits.
-.wen
+and Exim does so.  This attempt to remove Exim from TLS policy decisions
+failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
+of the NSS library.  Thus Exim gains the &%tls_dh_max_bits%& global option,
+which applies to all D-H usage, client or server.  If the value returned by
+GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
+to &%tls_dh_max_bits%&.  The default value has been set at the current NSS
+limit, which is still much higher than Exim historically used.
+
+The filename and bits used will change as the GnuTLS maintainers change the
+value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
+&%tls_dh_max_bits%&.  At the time of writing (mid 2012), GnuTLS 2.12 recommends
+2432 bits, while NSS is limited to 2236 bits.
+
+In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
+increase the chance of the generated prime actually being within acceptable
+bounds, as GnuTLS has been observed to overshoot.  Note the check step in the
+procedure above.  There is no sane procedure available to Exim to double-check
+the size of the generated prime, so it might still be too large.

 
 
 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
 
 
 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"


@@ -25028,7 +25121,10 @@ There is a function in the OpenSSL library that can be passed a list of cipher
 suites before the cipher negotiation takes place. This specifies which ciphers
 are acceptable. The list is colon separated and may contain names like
 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
 suites before the cipher negotiation takes place. This specifies which ciphers
 are acceptable. The list is colon separated and may contain names like
 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&

-directly to this function call. The following quotation from the OpenSSL
+directly to this function call.
+Many systems will install the OpenSSL manual-pages, so you may have
+&'ciphers(1)'& available to you.
+The following quotation from the OpenSSL

 documentation specifies what forms of item are allowed in the cipher string:
 
 .ilist
 documentation specifies what forms of item are allowed in the cipher string:
 
 .ilist


@@ -25065,9 +25161,26 @@ includes any ciphers already present they will be ignored: that is, they will
 not be moved to the end of the list.
 .endlist
 
 not be moved to the end of the list.
 .endlist
 

+The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
+string:
+.code
+# note single-quotes to get ! past any shell history expansion
+$ openssl ciphers 'HIGH:!MD5:!SHA1'
+.endd
+
+This example will let the library defaults be permitted on the MX port, where
+there's probably no identity verification anyway, but ups the ante on the
+submission ports where the administrator might have some influence on the
+choice of clients used:
+.code
+# OpenSSL variant; see man ciphers(1)
+tls_require_ciphers = ${if =={$received_port}{25}\
+                           {DEFAULT}\
+                           {HIGH:!MD5:!SHA1}}
+.endd
+

 
 
 
 

-.new

 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
          "SECTreqciphgnu"
 .cindex "GnuTLS" "specifying parameters for"
 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
          "SECTreqciphgnu"
 .cindex "GnuTLS" "specifying parameters for"


@@ -25092,12 +25205,27 @@ aware of future feature enhancements of GnuTLS.
 
 Documentation of the strings accepted may be found in the GnuTLS manual, under
 "Priority strings".  This is online as
 
 Documentation of the strings accepted may be found in the GnuTLS manual, under
 "Priority strings".  This is online as

-&url(http://www.gnu.org/software/gnutls/manual/html_node/Priority-Strings.html).
+&url(http://www.gnu.org/software/gnutls/manual/html_node/Priority-Strings.html),
+but beware that this relates to GnuTLS 3, which may be newer than the version
+installed on your system.  If you are using GnuTLS 3,
+&url(http://www.gnu.org/software/gnutls/manual/html_node/Listing-the-ciphersuites-in-a-priority-string.html, then the example code)
+on that site can be used to test a given string.

 
 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
 "&%gnutls_require_protocols%&".  &%tls_require_ciphers%& was an Exim list.
 
 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
 "&%gnutls_require_protocols%&".  &%tls_require_ciphers%& was an Exim list.

-.wen
+
+This example will let the library defaults be permitted on the MX port, where
+there's probably no identity verification anyway, and lowers security further
+by increasing compatibility; but this ups the ante on the submission ports
+where the administrator might have some influence on the choice of clients
+used:
+.code
+# GnuTLS variant
+tls_require_ciphers = ${if =={$received_port}{25}\
+                           {NORMAL:%COMPAT}\
+                           {SECURE128}}
+.endd

 
 
 .section "Configuring an Exim server to use TLS" "SECID182"
 
 
 .section "Configuring an Exim server to use TLS" "SECID182"


@@ -25157,13 +25285,22 @@ this). There is one other option that may be needed in other situations. If
 tls_dhparam = /some/file/name
 .endd
 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
 tls_dhparam = /some/file/name
 .endd
 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers

-with the parameters contained in the file. This increases the set of cipher
-suites that the server supports. See the command
+with the parameters contained in the file.
+Set this to &`none`& to disable use of DH entirely, by making no prime
+available:
+.code
+tls_dhparam = none
+.endd
+This may also be set to a string identifying a standard prime to be used for
+DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
+used is &`ike23`&.  There are a few standard primes available, see the
+documetnation for &%tls_dhparam%& for the complete list.
+
+See the command

 .code
 openssl dhparam
 .endd
 .code
 openssl dhparam
 .endd

-for a way of generating this data. At present, &%tls_dhparam%& is used only
-when Exim is linked with OpenSSL. It is ignored if GnuTLS is being used.
+for a way of generating file data.

 
 The strings supplied for these three options are expanded every time a client
 host connects. It is therefore possible to use different certificates and keys
 
 The strings supplied for these three options are expanded every time a client
 host connects. It is therefore possible to use different certificates and keys


@@ -25330,7 +25467,6 @@ outgoing connection.
 
 
 
 
 
 

-.new

 .section "Use of TLS Server Name Indication" "SECTtlssni"
 .cindex "TLS" "Server Name Indication"
 .vindex "&$tls_sni$&"
 .section "Use of TLS Server Name Indication" "SECTtlssni"
 .cindex "TLS" "Server Name Indication"
 .vindex "&$tls_sni$&"


@@ -25402,7 +25538,6 @@ see &`-servername`& in the output, then OpenSSL has support.
 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
 0.5.10.  (Its presence predates the current API which Exim uses, so if Exim
 built, then you have SNI support).
 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
 0.5.10.  (Its presence predates the current API which Exim uses, so if Exim
 built, then you have SNI support).

-.wen