Docs: add note on round-robin DNS problems vs. authentication

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

diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt
index 2acd5d38e67d78b9a6170552790430dbc5070627..18e1710360e925b6fad6cbb422149325a0589049 100644 (file)
--- a/doc/doc-docbook/spec.xfpt
+++ b/doc/doc-docbook/spec.xfpt
@@ -434,6 +434,7 @@ directory are:
 .row &_filter.txt_&          "specification of the filter language"
 .row &_Exim3.upgrade_&       "upgrade notes from release 2 to release 3"
 .row &_Exim4.upgrade_&       "upgrade notes from release 3 to release 4"
 .row &_filter.txt_&          "specification of the filter language"
 .row &_Exim3.upgrade_&       "upgrade notes from release 2 to release 3"
 .row &_Exim4.upgrade_&       "upgrade notes from release 3 to release 4"

+.row &_openssl.txt_&         "installing a current OpenSSL release"

 .endtable
 
 The main specification and the specification of the filtering language are also
 .endtable
 
 The main specification and the specification of the filtering language are also


@@ -4474,12 +4475,12 @@ The name should not contain a &'/'& character.
 For a periodic queue run (see below)
 append to the name a slash and a time value.
 
 For a periodic queue run (see below)
 append to the name a slash and a time value.
 

-If other commandline options speicify an action, a &'-qG<name>'& option
+If other commandline options specify an action, a &'-qG<name>'& option

 will specify a queue to operate on.
 For example:
 .code
 exim -bp -qGquarantine
 will specify a queue to operate on.
 For example:
 .code
 exim -bp -qGquarantine

-mailq -qGquarantime
+mailq -qGquarantine

 exim -qGoffpeak -Rf @special.domain.example
 .endd
 
 exim -qGoffpeak -Rf @special.domain.example
 .endd
 


@@ -4918,8 +4919,12 @@ using this syntax:
 .endd
 on a line by itself. Double quotes round the file name are optional. If you use
 the first form, a configuration error occurs if the file does not exist; the
 .endd
 on a line by itself. Double quotes round the file name are optional. If you use
 the first form, a configuration error occurs if the file does not exist; the

-second form does nothing for non-existent files. In all cases, an absolute file
+second form does nothing for non-existent files.
+.new
+The first form allows a relative name. It is resolved relative to
+the directory of the including file. For the second form an absolute file

 name is required.
 name is required.

+.wen

 
 Includes may be nested to any depth, but remember that Exim reads its
 configuration file often, so it is a good idea to keep them to a minimum.
 
 Includes may be nested to any depth, but remember that Exim reads its
 configuration file often, so it is a good idea to keep them to a minimum.


@@ -7105,7 +7110,7 @@ Retries for the dnsdb lookup can be controlled by a retry modifier.
 The form if &"retry_VAL"& where VAL is an integer.
 The default count is set by the main configuration option &%dns_retry%&.
 
 The form if &"retry_VAL"& where VAL is an integer.
 The default count is set by the main configuration option &%dns_retry%&.
 

-.cindex cacheing "of dns lookup"
+.cindex caching "of dns lookup"

 .cindex TTL "of dns lookup"
 .cindex DNS TTL
 Dnsdb lookup results are cached within a single process (and its children).
 .cindex TTL "of dns lookup"
 .cindex DNS TTL
 Dnsdb lookup results are cached within a single process (and its children).


@@ -9100,7 +9105,7 @@ If the ACL returns defer the result is a forced-fail.  Otherwise the expansion f
 
 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
        {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
 
 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
        {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"

-.cindex "expansion" "extracting cerificate fields"
+.cindex "expansion" "extracting certificate fields"

 .cindex "&%certextract%&" "certificate fields"
 .cindex "certificate" "extracting fields"
 The <&'certificate'&> must be a variable of type certificate.
 .cindex "&%certextract%&" "certificate fields"
 .cindex "certificate" "extracting fields"
 The <&'certificate'&> must be a variable of type certificate.


@@ -12205,7 +12210,7 @@ normally the gid of the Exim user.
 .cindex "uid (user id)" "of originating user"
 .cindex "sender" "uid"
 .vindex "&$caller_uid$&"
 .cindex "uid (user id)" "of originating user"
 .cindex "sender" "uid"
 .vindex "&$caller_uid$&"

-.vindex "&$originaltor_uid$&"
+.vindex "&$originator_uid$&"

 The value of &$caller_uid$& that was set when the message was received. For
 messages received via the command line, this is the uid of the sending user.
 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
 The value of &$caller_uid$& that was set when the message was received. For
 messages received via the command line, this is the uid of the sending user.
 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim


@@ -12823,7 +12828,7 @@ If TLS has not been negotiated, the value will be 0.
 
 .vitem &$tls_in_ourcert$&
 .vindex "&$tls_in_ourcert$&"
 
 .vitem &$tls_in_ourcert$&
 .vindex "&$tls_in_ourcert$&"

-.cindex certificate veriables
+.cindex certificate variables

 This variable refers to the certificate presented to the peer of an
 inbound connection when the message was received.
 It is only useful as the argument of a
 This variable refers to the certificate presented to the peer of an
 inbound connection when the message was received.
 It is only useful as the argument of a


@@ -13093,7 +13098,7 @@ initial startup, even if &%perl_at_start%& is set.
 .oindex "&%perl_taintmode%&"
 .cindex "Perl" "taintmode"
 To provide more security executing Perl code via the embedded Perl
 .oindex "&%perl_taintmode%&"
 .cindex "Perl" "taintmode"
 To provide more security executing Perl code via the embedded Perl

-interpeter, the &%perl_taintmode%& option can be set. This enables the
+interpreter, the &%perl_taintmode%& option can be set. This enables the

 taint mode of the Perl interpreter. You are encouraged to set this
 option to a true value. To avoid breaking existing installations, it
 defaults to false.
 taint mode of the Perl interpreter. You are encouraged to set this
 option to a true value. To avoid breaking existing installations, it
 defaults to false.


@@ -14013,6 +14018,7 @@ acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
 .option acl_smtp_dkim main string&!! unset
 .cindex DKIM "ACL for"
 This option defines the ACL that is run for each DKIM signature
 .option acl_smtp_dkim main string&!! unset
 .cindex DKIM "ACL for"
 This option defines the ACL that is run for each DKIM signature

+(by default, or as specified in the dkim_verify_signers option)

 of a received message.
 See chapter &<<CHAPdkim>>& for further details.
 
 of a received message.
 See chapter &<<CHAPdkim>>& for further details.
 


@@ -14400,7 +14406,7 @@ it obviously cannot send an error message of any kind.
 
 There is a slight performance penalty for these checks.
 Versions of Exim preceding 4.88 had these disabled by default;
 
 There is a slight performance penalty for these checks.
 Versions of Exim preceding 4.88 had these disabled by default;

-high-rate intallations confident they will never run out of resources
+high-rate installations confident they will never run out of resources

 may wish to deliberately disable them.
 
 .option chunking_advertise_hosts main "host list&!!" *
 may wish to deliberately disable them.
 
 .option chunking_advertise_hosts main "host list&!!" *


@@ -14764,7 +14770,7 @@ not used.
 .option event_action main string&!! unset
 .cindex events
 This option declares a string to be expanded for Exim's events mechanism.
 .option event_action main string&!! unset
 .cindex events
 This option declares a string to be expanded for Exim's events mechanism.

-For details see &<<CHAPevents>>&.
+For details see chapter &<<CHAPevents>>&.

 
 
 .option exim_group main string "compile-time configured"
 
 
 .option exim_group main string "compile-time configured"


@@ -15115,7 +15121,7 @@ If the &%smtp_connection%& log selector is not set, this option has no effect.
 .option hosts_proxy main "host list&!!" unset
 .cindex proxy "proxy protocol"
 This option enables use of Proxy Protocol proxies for incoming
 .option hosts_proxy main "host list&!!" unset
 .cindex proxy "proxy protocol"
 This option enables use of Proxy Protocol proxies for incoming

-connections.  For details see &<<SECTproxyInbound>>&.
+connections.  For details see section &<<SECTproxyInbound>>&.

 
 
 .option hosts_treat_as_local main "domain list&!!" unset
 
 
 .option hosts_treat_as_local main "domain list&!!" unset


@@ -15289,6 +15295,9 @@ connecting on a regular LDAP port.  This is the LDAP equivalent of SMTP's
 of SSL-on-connect.
 In the event of failure to negotiate TLS, the action taken is controlled
 by &%ldap_require_cert%&.
 of SSL-on-connect.
 In the event of failure to negotiate TLS, the action taken is controlled
 by &%ldap_require_cert%&.

+.new
+This option is ignored for &`ldapi`& connections.
+.wen

 
 
 .option ldap_version main integer unset
 
 
 .option ldap_version main integer unset


@@ -16705,7 +16714,7 @@ example, instead of &"Administrative prohibition"&, it might give:
 .option smtputf8_advertise_hosts main "host list&!!" *
 .cindex "SMTPUTF8" "advertising"
 When Exim is built with support for internationalised mail names,
 .option smtputf8_advertise_hosts main "host list&!!" *
 .cindex "SMTPUTF8" "advertising"
 When Exim is built with support for internationalised mail names,

-the availability therof is advertised in
+the availability thereof is advertised in

 response to EHLO only to those client hosts that match this option. See
 chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
 
 response to EHLO only to those client hosts that match this option. See
 chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
 


@@ -20883,7 +20892,7 @@ resent to other recipients.
 .option event_action transports string&!! unset
 .cindex events
 This option declares a string to be expanded for Exim's events mechanism.
 .option event_action transports string&!! unset
 .cindex events
 This option declares a string to be expanded for Exim's events mechanism.

-For details see &<<CHAPevents>>&.
+For details see chapter &<<CHAPevents>>&.

 
 
 .option group transports string&!! "Exim group"
 
 
 .option group transports string&!! "Exim group"


@@ -20998,7 +21007,7 @@ The control does not apply to shadow transports.
 
 .cindex "hints database" "transport concurrency control"
 Exim implements this control by means of a hints database in which a record is
 
 .cindex "hints database" "transport concurrency control"
 Exim implements this control by means of a hints database in which a record is

-incremented whenever a transport process is beaing created. The record
+incremented whenever a transport process is being created. The record

 is decremented and possibly removed when the process terminates.
 Obviously there is scope for
 records to get left lying around if there is a system or program crash. To
 is decremented and possibly removed when the process terminates.
 Obviously there is scope for
 records to get left lying around if there is a system or program crash. To


@@ -23255,12 +23264,12 @@ message_suffix =
 &`\n`& to &`\r\n`& in &%message_suffix%&.
 
 
 &`\n`& to &`\r\n`& in &%message_suffix%&.
 
 

-.option path pipe string "see below"
-This option specifies the string that is set up in the PATH environment
-variable of the subprocess. The default is:
-.code
-/bin:/usr/bin
-.endd
+.option path pipe string&!! "/bin:/usr/bin"
+.new
+This option is expanded and
+.wen
+specifies the string that is set up in the PATH environment
+variable of the subprocess.

 If the &%command%& option does not yield an absolute path name, the command is
 sought in the PATH directories, in the usual way. &*Warning*&: This does not
 apply to a command specified as a transport filter.
 If the &%command%& option does not yield an absolute path name, the command is
 sought in the PATH directories, in the usual way. &*Warning*&: This does not
 apply to a command specified as a transport filter.


@@ -23645,7 +23654,7 @@ of the message. Its value must not be zero. See also &%final_timeout%&.
 .option dkim_canon smtp string&!! unset
 .option dkim_strict smtp string&!! unset
 .option dkim_sign_headers smtp string&!! unset
 .option dkim_canon smtp string&!! unset
 .option dkim_strict smtp string&!! unset
 .option dkim_sign_headers smtp string&!! unset

-DKIM signing options.  For details see &<<SECDKIMSIGN>>&.
+DKIM signing options.  For details see section &<<SECDKIMSIGN>>&.

 
 
 .option delay_after_cutoff smtp boolean true
 
 
 .option delay_after_cutoff smtp boolean true


@@ -23962,12 +23971,12 @@ unauthenticated. See also &%hosts_require_auth%&, and chapter
 .cindex "RFC 3030" "CHUNKING"
 This option provides a list of servers to which, provided they announce
 CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
 .cindex "RFC 3030" "CHUNKING"
 This option provides a list of servers to which, provided they announce
 CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.

-BDAT will not be used in conjuction with a transport filter.
+BDAT will not be used in conjunction with a transport filter.

 
 .option hosts_try_fastopen smtp "host list!!" unset
 
 .option hosts_try_fastopen smtp "host list!!" unset

-.option "fast open, TCP" "enabling, in client"
-.option "TCP Fast Open" "enabling, in client"
-.option "RFC 7413" "TCP Fast Open"
+.cindex "fast open, TCP" "enabling, in client"
+.cindex "TCP Fast Open" "enabling, in client"
+.cindex "RFC 7413" "TCP Fast Open"

 This option provides a list of servers to which, provided
 the facility is supported by this system, Exim will attempt to
 perform a TCP Fast Open.
 This option provides a list of servers to which, provided
 the facility is supported by this system, Exim will attempt to
 perform a TCP Fast Open.


@@ -24151,7 +24160,7 @@ the use of the SIZE option altogether.
 .option socks_proxy smtp string&!! unset
 .cindex proxy SOCKS
 This option enables use of SOCKS proxies for connections made by the
 .option socks_proxy smtp string&!! unset
 .cindex proxy SOCKS
 This option enables use of SOCKS proxies for connections made by the

-transport.  For details see &<<SECTproxySOCKS>>&.
+transport.  For details see section &<<SECTproxySOCKS>>&.

 
 
 .option tls_certificate smtp string&!! unset
 
 
 .option tls_certificate smtp string&!! unset


@@ -25856,6 +25865,19 @@ turned into a permanent error if you wish. In the second case, Exim tries to
 deliver the message unauthenticated.
 .endlist
 
 deliver the message unauthenticated.
 .endlist
 

+.new
+Note that the hostlist test for whether to do authentication can be
+confused if name-IP lookups change between the time the peer is decided
+on and the transport running.  For example, with a manualroute
+router given a host name, and DNS "round-robin" use by that name: if
+the local resolver cache times out between the router and the transport
+running, the transport may get an IP for the name for its authentication
+check which does not match the connection peer IP.
+No authentication will then be done, despite the names being identical.
+
+For such cases use a separate transport which alwats authenticates.
+.wen
+

 .cindex "AUTH" "on MAIL command"
 When Exim has authenticated itself to a remote server, it adds the AUTH
 parameter to the MAIL commands it sends, if it has an authenticated sender for
 .cindex "AUTH" "on MAIL command"
 When Exim has authenticated itself to a remote server, it adds the AUTH
 parameter to the MAIL commands it sends, if it has an authenticated sender for


@@ -27527,7 +27549,7 @@ Great care should be taken to deal with matters of case, various injection
 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
 can always be referenced; it is important to remember that &$tls_in_sni$& is
 arbitrary unverified data provided prior to authentication.
 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
 can always be referenced; it is important to remember that &$tls_in_sni$& is
 arbitrary unverified data provided prior to authentication.

-Further, the initial cerificate is loaded before SNI is arrived, so
+Further, the initial certificate is loaded before SNI is arrived, so

 an expansion for &%tls_certificate%& must have a default which is used
 when &$tls_in_sni$& is empty.
 
 an expansion for &%tls_certificate%& must have a default which is used
 when &$tls_in_sni$& is empty.
 


@@ -28904,7 +28926,7 @@ This behaviour can be adjusted by appending the option &*defer=*&<&'value'&>
 to the control; the default value is &"spool"& and the alternate value
 &"pass"& copies an SMTP defer response from the target back to the initiator
 and does not queue the message.
 to the control; the default value is &"spool"& and the alternate value
 &"pass"& copies an SMTP defer response from the target back to the initiator
 and does not queue the message.

-Note that this is independent of any receipient verify conditions in the ACL.
+Note that this is independent of any recipient verify conditions in the ACL.

 
 Delivery in this mode avoids the generation of a bounce mail to a
 (possibly faked)
 
 Delivery in this mode avoids the generation of a bounce mail to a
 (possibly faked)


@@ -29128,7 +29150,7 @@ that are being submitted at the same time using &%-bs%& or &%-bS%&.
 .vitem &*control&~=&~utf8_downconvert*&
 This control enables conversion of UTF-8 in message addresses
 to a-label form.
 .vitem &*control&~=&~utf8_downconvert*&
 This control enables conversion of UTF-8 in message addresses
 to a-label form.

-For details see &<<SECTi18nMTA>>&.
+For details see section &<<SECTi18nMTA>>&.

 .endlist vlist
 
 
 .endlist vlist
 
 


@@ -29800,7 +29822,7 @@ deny  dnslists = blackholes.mail-abuse.org
 warn  message  = X-Warn: sending host is on dialups list
       dnslists = dialups.mail-abuse.org
 .endd
 warn  message  = X-Warn: sending host is on dialups list
       dnslists = dialups.mail-abuse.org
 .endd

-.cindex cacheing "of dns lookup"
+.cindex caching "of dns lookup"

 .cindex DNS TTL
 DNS list lookups are cached by Exim for the duration of the SMTP session
 (but limited by the DNS return TTL value),
 .cindex DNS TTL
 DNS list lookups are cached by Exim for the duration of the SMTP session
 (but limited by the DNS return TTL value),


@@ -29913,7 +29935,7 @@ multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
 of expanding the condition might be something like this:
 .code
 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
 of expanding the condition might be something like this:
 .code

-dnslists = sbl.spahmaus.org/<|192.168.2.3|192.168.5.6|...
+dnslists = sbl.spamhaus.org/<|192.168.2.3|192.168.5.6|...

 .endd
 Thus, this example checks whether or not the IP addresses of the sender
 domain's mail servers are on the Spamhaus black list.
 .endd
 Thus, this example checks whether or not the IP addresses of the sender
 domain's mail servers are on the Spamhaus black list.


@@ -36037,7 +36059,7 @@ off the &%outgoing_interface%& option.
 .next
 .cindex "log" "outgoing remote port"
 .cindex "port" "logging outgoint remote"
 .next
 .cindex "log" "outgoing remote port"
 .cindex "port" "logging outgoint remote"

-.cindex "TCP/IP" "logging ougtoing remote port"
+.cindex "TCP/IP" "logging outgoing remote port"

 &%outgoing_port%&: The remote port number is added to delivery log lines (those
 containing => tags) following the IP address.
 The local port is also added if &%incoming_interface%& and
 &%outgoing_port%&: The remote port number is added to delivery log lines (those
 containing => tags) following the IP address.
 The local port is also added if &%incoming_interface%& and


@@ -38481,9 +38503,9 @@ To include this support, include &"SUPPORT_PROXY=yes"&
 in Local/Makefile.
 
 It was built on specifications from:
 in Local/Makefile.
 
 It was built on specifications from:

-http://haproxy.1wt.eu/download/1.5/doc/proxy-protocol.txt
+(&url(http://haproxy.1wt.eu/download/1.5/doc/proxy-protocol.txt)).

 That URL was revised in May 2014 to version 2 spec:
 That URL was revised in May 2014 to version 2 spec:

-http://git.1wt.eu/web?p=haproxy.git;a=commitdiff;h=afb768340c9d7e50d8e
+(&url(http://git.1wt.eu/web?p=haproxy.git;a=commitdiff;h=afb768340c9d7e50d8e)).

 
 The purpose of this facility is so that an application load balancer,
 such as HAProxy, can sit in front of several Exim servers
 
 The purpose of this facility is so that an application load balancer,
 such as HAProxy, can sit in front of several Exim servers


@@ -38789,7 +38811,7 @@ can be used to affect that action (more on this below).
 An additional variable, &$event_data$&, is filled with information varying
 with the event type:
 .display
 An additional variable, &$event_data$&, is filled with information varying
 with the event type:
 .display

-&`msg:delivery         `& smtp confirmation mssage
+&`msg:delivery         `& smtp confirmation message

 &`msg:rcpt:host:defer  `& error string
 &`msg:rcpt:defer       `& error string
 &`msg:host:defer       `& error string
 &`msg:rcpt:host:defer  `& error string
 &`msg:rcpt:defer       `& error string
 &`msg:host:defer       `& error string