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experimental-spec.txt
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experimental-spec.txt
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From time to time, experimental features may be added to Exim.
While a feature is experimental, there will be a build-time
option whose name starts "EXPERIMENTAL_" that must be set in
order to include the feature. This file contains information
about experimental features, all of which are unstable and
liable to incompatible change.
Brightmail AntiSpam (BMI) suppport
--------------------------------------------------------------
Brightmail AntiSpam is a commercial package. Please see
http://www.brightmail.com for more information on
the product. For the sake of clarity, we'll refer to it as
"BMI" from now on.
0) BMI concept and implementation overview
In contrast to how spam-scanning with SpamAssassin is
implemented in exiscan-acl, BMI is more suited for per
-recipient scanning of messages. However, each messages is
scanned only once, but multiple "verdicts" for multiple
recipients can be returned from the BMI server. The exiscan
implementation passes the message to the BMI server just
before accepting it. It then adds the retrieved verdicts to
the messages header file in the spool. These verdicts can then
be queried in routers, where operation is per-recipient
instead of per-message. To use BMI, you need to take the
following steps:
1) Compile Exim with BMI support
2) Set up main BMI options (top section of Exim config file)
3) Set up ACL control statement (ACL section of the config
file)
4) Set up your routers to use BMI verdicts (routers section
of the config file).
5) (Optional) Set up per-recipient opt-in information.
These four steps are explained in more details below.
1) Adding support for BMI at compile time
To compile with BMI support, you need to link Exim against
the Brighmail client SDK, consisting of a library
(libbmiclient_single.so) and a header file (bmi_api.h).
You'll also need to explicitly set a flag in the Makefile to
include BMI support in the Exim binary. Both can be achieved
with these lines in Local/Makefile:
EXPERIMENTAL_BRIGHTMAIL=yes
CFLAGS=-I/path/to/the/dir/with/the/includefile
EXTRALIBS_EXIM=-L/path/to/the/dir/with/the/library -lbmiclient_single
If you use other CFLAGS or EXTRALIBS_EXIM settings then
merge the content of these lines with them.
Note for BMI6.x users: You'll also have to add -lxml2_single
to the EXTRALIBS_EXIM line. Users of 5.5x do not need to do
this.
You should also include the location of
libbmiclient_single.so in your dynamic linker configuration
file (usually /etc/ld.so.conf) and run "ldconfig"
afterwards, or else the produced Exim binary will not be
able to find the library file.
2) Setting up BMI support in the Exim main configuration
To enable BMI support in the main Exim configuration, you
should set the path to the main BMI configuration file with
the "bmi_config_file" option, like this:
bmi_config_file = /opt/brightmail/etc/brightmail.cfg
This must go into section 1 of Exim's configuration file (You
can put it right on top). If you omit this option, it
defaults to /opt/brightmail/etc/brightmail.cfg.
Note for BMI6.x users: This file is in XML format in V6.xx
and its name is /opt/brightmail/etc/bmiconfig.xml. So BMI
6.x users MUST set the bmi_config_file option.
3) Set up ACL control statement
To optimize performance, it makes sense only to process
messages coming from remote, untrusted sources with the BMI
server. To set up a messages for processing by the BMI
server, you MUST set the "bmi_run" control statement in any
ACL for an incoming message. You will typically do this in
an "accept" block in the "acl_check_rcpt" ACL. You should
use the "accept" block(s) that accept messages from remote
servers for your own domain(s). Here is an example that uses
the "accept" blocks from Exim's default configuration file:
accept domains = +local_domains
endpass
verify = recipient
control = bmi_run
accept domains = +relay_to_domains
endpass
verify = recipient
control = bmi_run
If bmi_run is not set in any ACL during reception of the
message, it will NOT be passed to the BMI server.
4) Setting up routers to use BMI verdicts
When a message has been run through the BMI server, one or
more "verdicts" are present. Different recipients can have
different verdicts. Each recipient is treated individually
during routing, so you can query the verdicts by recipient
at that stage. From Exim's view, a verdict can have the
following outcomes:
o deliver the message normally
o deliver the message to an alternate location
o do not deliver the message
To query the verdict for a recipient, the implementation
offers the following tools:
- Boolean router preconditions. These can be used in any
router. For a simple implementation of BMI, these may be
all that you need. The following preconditions are
available:
o bmi_deliver_default
This precondition is TRUE if the verdict for the
recipient is to deliver the message normally. If the
message has not been processed by the BMI server, this
variable defaults to TRUE.
o bmi_deliver_alternate
This precondition is TRUE if the verdict for the
recipient is to deliver the message to an alternate
location. You can get the location string from the
$bmi_alt_location expansion variable if you need it. See
further below. If the message has not been processed by
the BMI server, this variable defaults to FALSE.
o bmi_dont_deliver
This precondition is TRUE if the verdict for the
recipient is NOT to deliver the message to the
recipient. You will typically use this precondition in a
top-level blackhole router, like this:
# don't deliver messages handled by the BMI server
bmi_blackhole:
driver = redirect
bmi_dont_deliver
data = :blackhole:
This router should be on top of all others, so messages
that should not be delivered do not reach other routers
at all. If the message has not been processed by
the BMI server, this variable defaults to FALSE.
- A list router precondition to query if rules "fired" on
the message for the recipient. Its name is "bmi_rule". You
use it by passing it a colon-separated list of rule
numbers. You can use this condition to route messages that
matched specific rules. Here is an example:
# special router for BMI rule #5, #8 and #11
bmi_rule_redirect:
driver = redirect
bmi_rule = 5:8:11
data = postmaster@mydomain.com
- Expansion variables. Several expansion variables are set
during routing. You can use them in custom router
conditions, for example. The following variables are
available:
o $bmi_base64_verdict
This variable will contain the BASE64 encoded verdict
for the recipient being routed. You can use it to add a
header to messages for tracking purposes, for example:
localuser:
driver = accept
check_local_user
headers_add = X-Brightmail-Verdict: $bmi_base64_verdict
transport = local_delivery
If there is no verdict available for the recipient being
routed, this variable contains the empty string.
o $bmi_base64_tracker_verdict
This variable will contain a BASE64 encoded subset of
the verdict information concerning the "rules" that
fired on the message. You can add this string to a
header, commonly named "X-Brightmail-Tracker". Example:
localuser:
driver = accept
check_local_user
headers_add = X-Brightmail-Tracker: $bmi_base64_tracker_verdict
transport = local_delivery
If there is no verdict available for the recipient being
routed, this variable contains the empty string.
o $bmi_alt_location
If the verdict is to redirect the message to an
alternate location, this variable will contain the
alternate location string returned by the BMI server. In
its default configuration, this is a header-like string
that can be added to the message with "headers_add". If
there is no verdict available for the recipient being
routed, or if the message is to be delivered normally,
this variable contains the empty string.
o $bmi_deliver
This is an additional integer variable that can be used
to query if the message should be delivered at all. You
should use router preconditions instead if possible.
$bmi_deliver is '0': the message should NOT be delivered.
$bmi_deliver is '1': the message should be delivered.
IMPORTANT NOTE: Verdict inheritance.
The message is passed to the BMI server during message
reception, using the target addresses from the RCPT TO:
commands in the SMTP transaction. If recipients get expanded
or re-written (for example by aliasing), the new address(es)
inherit the verdict from the original address. This means
that verdicts also apply to all "child" addresses generated
from top-level addresses that were sent to the BMI server.
5) Using per-recipient opt-in information (Optional)
The BMI server features multiple scanning "profiles" for
individual recipients. These are usually stored in a LDAP
server and are queried by the BMI server itself. However,
you can also pass opt-in data for each recipient from the
MTA to the BMI server. This is particularly useful if you
already look up recipient data in Exim anyway (which can
also be stored in a SQL database or other source). This
implementation enables you to pass opt-in data to the BMI
server in the RCPT ACL. This works by setting the
'bmi_optin' modifier in a block of that ACL. If should be
set to a list of comma-separated strings that identify the
features which the BMI server should use for that particular
recipient. Ideally, you would use the 'bmi_optin' modifier
in the same ACL block where you set the 'bmi_run' control
flag. Here is an example that will pull opt-in data for each
recipient from a flat file called
'/etc/exim/bmi_optin_data'.
The file format:
user1@mydomain.com: <OPTIN STRING1>:<OPTIN STRING2>
user2@thatdomain.com: <OPTIN STRING3>
The example:
accept domains = +relay_to_domains
endpass
verify = recipient
bmi_optin = ${lookup{$local_part@$domain}lsearch{/etc/exim/bmi_optin_data}}
control = bmi_run
Of course, you can also use any other lookup method that
Exim supports, including LDAP, Postgres, MySQL, Oracle etc.,
as long as the result is a list of colon-separated opt-in
strings.
For a list of available opt-in strings, please contact your
Brightmail representative.
Sender Policy Framework (SPF) support
--------------------------------------------------------------
To learn more about SPF, visit http://www.openspf.org. This
document does not explain the SPF fundamentals, you should
read and understand the implications of deploying SPF on your
system before doing so.
SPF support is added via the libspf2 library. Visit
http://www.libspf2.org/
to obtain a copy, then compile and install it. By default,
this will put headers in /usr/local/include and the static
library in /usr/local/lib.
To compile Exim with SPF support, set these additional flags in
Local/Makefile:
EXPERIMENTAL_SPF=yes
CFLAGS=-DSPF -I/usr/local/include
EXTRALIBS_EXIM=-L/usr/local/lib -lspf2
This assumes that the libspf2 files are installed in
their default locations.
You can now run SPF checks in incoming SMTP by using the "spf"
ACL condition in either the MAIL, RCPT or DATA ACLs. When
using it in the RCPT ACL, you can make the checks dependent on
the RCPT address (or domain), so you can check SPF records
only for certain target domains. This gives you the
possibility to opt-out certain customers that do not want
their mail to be subject to SPF checking.
The spf condition takes a list of strings on its right-hand
side. These strings describe the outcome of the SPF check for
which the spf condition should succeed. Valid strings are:
o pass The SPF check passed, the sending host
is positively verified by SPF.
o fail The SPF check failed, the sending host
is NOT allowed to send mail for the domain
in the envelope-from address.
o softfail The SPF check failed, but the queried
domain can't absolutely confirm that this
is a forgery.
o none The queried domain does not publish SPF
records.
o neutral The SPF check returned a "neutral" state.
This means the queried domain has published
a SPF record, but wants to allow outside
servers to send mail under its domain as well.
This should be treated like "none".
o permerror This indicates a syntax error in the SPF
record of the queried domain. You may deny
messages when this occurs. (Changed in 4.83)
o temperror This indicates a temporary error during all
processing, including Exim's SPF processing.
You may defer messages when this occurs.
(Changed in 4.83)
o err_temp Same as permerror, deprecated in 4.83, will be
removed in a future release.
o err_perm Same as temperror, deprecated in 4.83, will be
removed in a future release.
You can prefix each string with an exclamation mark to invert
its meaning, for example "!fail" will match all results but
"fail". The string list is evaluated left-to-right, in a
short-circuit fashion. When a string matches the outcome of
the SPF check, the condition succeeds. If none of the listed
strings matches the outcome of the SPF check, the condition
fails.
Here is an example to fail forgery attempts from domains that
publish SPF records:
/* -----------------
deny message = $sender_host_address is not allowed to send mail from ${if def:sender_address_domain {$sender_address_domain}{$sender_helo_name}}. \
Please see http://www.openspf.org/Why?scope=${if def:sender_address_domain {mfrom}{helo}};identity=${if def:sender_address_domain {$sender_address}{$sender_helo_name}};ip=$sender_host_address
spf = fail
--------------------- */
You can also give special treatment to specific domains:
/* -----------------
deny message = AOL sender, but not from AOL-approved relay.
sender_domains = aol.com
spf = fail:neutral
--------------------- */
Explanation: AOL publishes SPF records, but is liberal and
still allows non-approved relays to send mail from aol.com.
This will result in a "neutral" state, while mail from genuine
AOL servers will result in "pass". The example above takes
this into account and treats "neutral" like "fail", but only
for aol.com. Please note that this violates the SPF draft.
When the spf condition has run, it sets up several expansion
variables.
$spf_header_comment
This contains a human-readable string describing the outcome
of the SPF check. You can add it to a custom header or use
it for logging purposes.
$spf_received
This contains a complete Received-SPF: header that can be
added to the message. Please note that according to the SPF
draft, this header must be added at the top of the header
list. Please see section 10 on how you can do this.
Note: in case of "Best-guess" (see below), the convention is
to put this string in a header called X-SPF-Guess: instead.
$spf_result
This contains the outcome of the SPF check in string form,
one of pass, fail, softfail, none, neutral, permerror or
temperror.
$spf_smtp_comment
This contains a string that can be used in a SMTP response
to the calling party. Useful for "fail".
In addition to SPF, you can also perform checks for so-called
"Best-guess". Strictly speaking, "Best-guess" is not standard
SPF, but it is supported by the same framework that enables SPF
capability. Refer to http://www.openspf.org/FAQ/Best_guess_record
for a description of what it means.
To access this feature, simply use the spf_guess condition in place
of the spf one. For example:
/* -----------------
deny message = $sender_host_address doesn't look trustworthy to me
spf_guess = fail
--------------------- */
In case you decide to reject messages based on this check, you
should note that although it uses the same framework, "Best-guess"
is NOT SPF, and therefore you should not mention SPF at all in your
reject message.
When the spf_guess condition has run, it sets up the same expansion
variables as when spf condition is run, described above.
Additionally, since Best-guess is not standardized, you may redefine
what "Best-guess" means to you by redefining spf_guess variable in
global config. For example, the following:
/* -----------------
spf_guess = v=spf1 a/16 mx/16 ptr ?all
--------------------- */
would relax host matching rules to a broader network range.
SRS (Sender Rewriting Scheme) Support
--------------------------------------------------------------
Exiscan currently includes SRS support via Miles Wilton's
libsrs_alt library. The current version of the supported
library is 0.5.
In order to use SRS, you must get a copy of libsrs_alt from
http://srs.mirtol.com/
Unpack the tarball, then refer to MTAs/README.EXIM
to proceed. You need to set
EXPERIMENTAL_SRS=yes
in your Local/Makefile.
DCC Support
--------------------------------------------------------------
*) Building exim
In order to build exim with DCC support add
EXPERIMENTAL_DCC=yes
to your Makefile. (Re-)build/install exim. exim -d should show
EXPERIMENTAL_DCC under "Support for".
*) Configuration
In the main section of exim.cf add at least
dccifd_address = /usr/local/dcc/var/dccifd
or
dccifd_address = <ip> <port>
In the DATA ACL you can use the new condition
dcc = *
After that "$dcc_header" contains the X-DCC-Header.
Return values are:
fail for overall "R", "G" from dccifd
defer for overall "T" from dccifd
accept for overall "A", "S" from dccifd
dcc = */defer_ok works as for spamd.
The "$dcc_result" variable contains the overall result from DCC
answer. There will an X-DCC: header added to the mail.
Usually you'll use
defer !dcc = *
to greylist with DCC.
If you set, in the main section,
dcc_direct_add_header = true
then the dcc header will be added "in deep" and if the spool
file was already written it gets removed. This forces Exim to
write it again if needed. This helps to get the DCC Header
through to eg. SpamAssassin.
If you want to pass even more headers in the middle of the
DATA stage you can set
$acl_m_dcc_add_header
to tell the DCC routines to add more information; eg, you might set
this to some results from ClamAV. Be careful. Header syntax is
not checked and is added "as is".
In case you've troubles with sites sending the same queue items from several
hosts and fail to get through greylisting you can use
$acl_m_dcc_override_client_ip
Setting $acl_m_dcc_override_client_ip to an IP address overrides the default
of $sender_host_address. eg. use the following ACL in DATA stage:
warn set acl_m_dcc_override_client_ip = \
${lookup{$sender_helo_name}nwildlsearch{/etc/mail/multipleip_sites}{$value}{}}
condition = ${if def:acl_m_dcc_override_client_ip}
log_message = dbg: acl_m_dcc_override_client_ip set to \
$acl_m_dcc_override_client_ip
Then set something like
# cat /etc/mail/multipleip_sites
mout-xforward.gmx.net 82.165.159.12
mout.gmx.net 212.227.15.16
Use a reasonable IP. eg. one the sending cluster acutally uses.
DMARC Support
--------------------------------------------------------------
DMARC combines feedback from SPF, DKIM, and header From: in order
to attempt to provide better indicators of the authenticity of an
email. This document does not explain the fundamentals, you
should read and understand how it works by visiting the website at
http://www.dmarc.org/.
DMARC support is added via the libopendmarc library. Visit:
http://sourceforge.net/projects/opendmarc/
to obtain a copy, or find it in your favorite rpm package
repository. If building from source, this description assumes
that headers will be in /usr/local/include, and that the libraries
are in /usr/local/lib.
1. To compile Exim with DMARC support, you must first enable SPF.
Please read the above section on enabling the EXPERIMENTAL_SPF
feature. You must also have DKIM support, so you cannot set the
DISABLE_DKIM feature. Once both of those conditions have been met
you can enable DMARC in Local/Makefile:
EXPERIMENTAL_DMARC=yes
LDFLAGS += -lopendmarc
# CFLAGS += -I/usr/local/include
# LDFLAGS += -L/usr/local/lib
The first line sets the feature to include the correct code, and
the second line says to link the libopendmarc libraries into the
exim binary. The commented out lines should be uncommented if you
built opendmarc from source and installed in the default location.
Adjust the paths if you installed them elsewhere, but you do not
need to uncomment them if an rpm (or you) installed them in the
package controlled locations (/usr/include and /usr/lib).
2. Use the following global settings to configure DMARC:
Required:
dmarc_tld_file Defines the location of a text file of valid
top level domains the opendmarc library uses
during domain parsing. Maintained by Mozilla,
the most current version can be downloaded
from a link at http://publicsuffix.org/list/.
Optional:
dmarc_history_file Defines the location of a file to log results
of dmarc verification on inbound emails. The
contents are importable by the opendmarc tools
which will manage the data, send out DMARC
reports, and expire the data. Make sure the
directory of this file is writable by the user
exim runs as.
dmarc_forensic_sender The email address to use when sending a
forensic report detailing alignment failures
if a sender domain's dmarc record specifies it
and you have configured Exim to send them.
Default: do-not-reply@$default_hostname
3. By default, the DMARC processing will run for any remote,
non-authenticated user. It makes sense to only verify DMARC
status of messages coming from remote, untrusted sources. You can
use standard conditions such as hosts, senders, etc, to decide that
DMARC verification should *not* be performed for them and disable
DMARC with a control setting:
control = dmarc_disable_verify
A DMARC record can also specify a "forensic address", which gives
exim an email address to submit reports about failed alignment.
Exim does not do this by default because in certain conditions it
results in unintended information leakage (what lists a user might
be subscribed to, etc). You must configure exim to submit forensic
reports to the owner of the domain. If the DMARC record contains a
forensic address and you specify the control statement below, then
exim will send these forensic emails. It's also advised that you
configure a dmarc_forensic_sender because the default sender address
construction might be inadequate.
control = dmarc_enable_forensic
(AGAIN: You can choose not to send these forensic reports by simply
not putting the dmarc_enable_forensic control line at any point in
your exim config. If you don't tell it to send them, it will not
send them.)
There are no options to either control. Both must appear before
the DATA acl.
4. You can now run DMARC checks in incoming SMTP by using the
"dmarc_status" ACL condition in the DATA ACL. You are required to
call the spf condition first in the ACLs, then the "dmarc_status"
condition. Putting this condition in the ACLs is required in order
for a DMARC check to actually occur. All of the variables are set
up before the DATA ACL, but there is no actual DMARC check that
occurs until a "dmarc_status" condition is encountered in the ACLs.
The dmarc_status condition takes a list of strings on its
right-hand side. These strings describe recommended action based
on the DMARC check. To understand what the policy recommendations
mean, refer to the DMARC website above. Valid strings are:
o accept The DMARC check passed and the library recommends
accepting the email.
o reject The DMARC check failed and the library recommends
rejecting the email.
o quarantine The DMARC check failed and the library recommends
keeping it for further inspection.
o none The DMARC check passed and the library recommends
no specific action, neutral.
o norecord No policy section in the DMARC record for this
sender domain.
o nofrom Unable to determine the domain of the sender.
o temperror Library error or dns error.
o off The DMARC check was disabled for this email.
You can prefix each string with an exclamation mark to invert its
meaning, for example "!accept" will match all results but
"accept". The string list is evaluated left-to-right in a
short-circuit fashion. When a string matches the outcome of the
DMARC check, the condition succeeds. If none of the listed
strings matches the outcome of the DMARC check, the condition
fails.
Of course, you can also use any other lookup method that Exim
supports, including LDAP, Postgres, MySQL, etc, as long as the
result is a list of colon-separated strings.
Several expansion variables are set before the DATA ACL is
processed, and you can use them in this ACL. The following
expansion variables are available:
o $dmarc_status
This is a one word status indicating what the DMARC library
thinks of the email. It is a combination of the results of
DMARC record lookup and the SPF/DKIM/DMARC processing results
(if a DMARC record was found). The actual policy declared
in the DMARC record is in a separate expansion variable.
o $dmarc_status_text
This is a slightly longer, human readable status.
o $dmarc_used_domain
This is the domain which DMARC used to look up the DMARC
policy record.
o $dmarc_domain_policy
This is the policy declared in the DMARC record. Valid values
are "none", "reject" and "quarantine". It is blank when there
is any error, including no DMARC record.
o $dmarc_ar_header
This is the entire Authentication-Results header which you can
add using an add_header modifier.
5. How to enable DMARC advanced operation:
By default, Exim's DMARC configuration is intended to be
non-intrusive and conservative. To facilitate this, Exim will not
create any type of logging files without explicit configuration by
you, the admin. Nor will Exim send out any emails/reports about
DMARC issues without explicit configuration by you, the admin (other
than typical bounce messages that may come about due to ACL
processing or failure delivery issues).
In order to log statistics suitable to be imported by the opendmarc
tools, you need to:
a. Configure the global setting dmarc_history_file.
b. Configure cron jobs to call the appropriate opendmarc history
import scripts and truncating the dmarc_history_file.
In order to send forensic reports, you need to:
a. Configure the global setting dmarc_forensic_sender.
b. Configure, somewhere before the DATA ACL, the control option to
enable sending DMARC forensic reports.
6. Example usage:
(RCPT ACL)
warn domains = +local_domains
hosts = +local_hosts
control = dmarc_disable_verify
warn !domains = +screwed_up_dmarc_records
control = dmarc_enable_forensic
warn condition = (lookup if destined to mailing list)
set acl_m_mailing_list = 1
(DATA ACL)
warn dmarc_status = accept : none : off
!authenticated = *
log_message = DMARC DEBUG: $dmarc_status $dmarc_used_domain
add_header = $dmarc_ar_header
warn dmarc_status = !accept
!authenticated = *
log_message = DMARC DEBUG: '$dmarc_status' for $dmarc_used_domain
warn dmarc_status = quarantine
!authenticated = *
set $acl_m_quarantine = 1
# Do something in a transport with this flag variable
deny condition = ${if eq{$dmarc_domain_policy}{reject}}
condition = ${if eq{$acl_m_mailing_list}{1}}
message = Messages from $dmarc_used_domain break mailing lists
deny dmarc_status = reject
!authenticated = *
message = Message from $dmarc_used_domain failed sender's DMARC policy, REJECT
Event Actions
--------------------------------------------------------------
(Renamed from TPDA, Transport post-delivery actions)
An arbitrary per-transport string can be expanded upon various transport events.
Additionally a main-section configuration option can be expanded on some
per-message events.
This feature may be used, for example, to write exim internal log information
(not available otherwise) into a database.
In order to use the feature, you must compile with
EXPERIMENTAL_EVENT=yes
in your Local/Makefile
and define one or both of
- the event_action option in the transport
- the event_action main option
to be expanded when the event fires.
A new variable, $event_name, is set to the event type when the
expansion is done. The current list of events is:
msg:complete after main per message
msg:delivery after transport per recipient
msg:host:defer after transport per attempt
msg:fail:delivery after main per recipient
msg:fail:internal after main per recipient
tcp:connect before transport per connection
tcp:close after transport per connection
tls:cert before both per certificate in verification chain
smtp:connect after transport per connection
The expansion is called for all event types, and should use the $event_name
variable to decide when to act. The value of the variable is a colon-separated
list, defining a position in the tree of possible events; it may be used as
a list or just matched on as a whole. There will be no whitespace.
There is an auxilary variable, $event_data, for which the
content is event_dependent:
msg:delivery smtp confirmation mssage
msg:host:defer error string
tls:cert verification chain depth
smtp:connect smtp banner
The msg:host:defer event populates one extra variable, $event_defer_errno.
The following variables are likely to be useful depending on the event type:
router_name, transport_name
local_part, domain
host, host_address, host_port
tls_out_peercert
lookup_dnssec_authenticated, tls_out_dane
sending_ip_address, sending_port
message_exim_id, verify_mode
An example might look like:
event_action = ${if eq {msg:delivery}{$event_name} \
{${lookup pgsql {SELECT * FROM record_Delivery( \
'${quote_pgsql:$sender_address_domain}',\
'${quote_pgsql:${lc:$sender_address_local_part}}', \
'${quote_pgsql:$domain}', \
'${quote_pgsql:${lc:$local_part}}', \
'${quote_pgsql:$host_address}', \
'${quote_pgsql:${lc:$host}}', \
'${quote_pgsql:$message_exim_id}')}} \
} {}}
The string is expanded when each of the supported events occur
and any side-effects of the expansion will happen.
Note that for complex operations an ACL expansion can be used.
The expansion of the event_action option should normally
return an empty string. Should it return anything else the
following will be forced:
msg:delivery (ignored)
msg:host:defer (ignored)
msg:fail:delivery (ignored)
tcp:connect do not connect
tcp:close (ignored)
tls:cert refuse verification
smtp:connect close connection
No other use is made of the result string.
Known issues:
- the tls:cert event is only called for the cert chain elements
received over the wire, with GnuTLS. OpenSSL gives the entire
chain including those loaded locally.
Redis Lookup
--------------------------------------------------------------
Redis is open source advanced key-value data store. This document
does not explain the fundamentals, you should read and understand how
it works by visiting the website at http://www.redis.io/.
Redis lookup support is added via the hiredis library. Visit:
https://github.com/redis/hiredis
to obtain a copy, or find it in your operating systems package repository.
If building from source, this description assumes that headers will be in
/usr/local/include, and that the libraries are in /usr/local/lib.
1. In order to build exim with Redis lookup support add
EXPERIMENTAL_REDIS=yes
to your Local/Makefile. (Re-)build/install exim. exim -d should show
Experimental_Redis in the line "Support for:".
EXPERIMENTAL_REDIS=yes
LDFLAGS += -lhiredis
# CFLAGS += -I/usr/local/include
# LDFLAGS += -L/usr/local/lib
The first line sets the feature to include the correct code, and
the second line says to link the hiredis libraries into the
exim binary. The commented out lines should be uncommented if you
built hiredis from source and installed in the default location.
Adjust the paths if you installed them elsewhere, but you do not
need to uncomment them if an rpm (or you) installed them in the
package controlled locations (/usr/include and /usr/lib).
2. Use the following global settings to configure Redis lookup support:
Required:
redis_servers This option provides a list of Redis servers
and associated connection data, to be used in
conjunction with redis lookups. The option is
only available if Exim is configured with Redis
support.
For example:
redis_servers = 127.0.0.1/10/ - using database 10 with no password
redis_servers = 127.0.0.1//password - to make use of the default database of 0 with a password
redis_servers = 127.0.0.1// - for default database of 0 with no password
3. Once you have the Redis servers defined you can then make use of the
experimental Redis lookup by specifying ${lookup redis{}} in a lookup query.
4. Example usage:
(Host List)
hostlist relay_from_ips = <\n ${lookup redis{SMEMBERS relay_from_ips}}
Where relay_from_ips is a Redis set which contains entries such as "192.168.0.0/24" "10.0.0.0/8" and so on.
The result set is returned as
192.168.0.0/24
10.0.0.0/8
..
.
(Domain list)
domainlist virtual_domains = ${lookup redis {HGET $domain domain}}
Where $domain is a hash which includes the key 'domain' and the value '$domain'.
(Adding or updating an existing key)
set acl_c_spammer = ${if eq{${lookup redis{SPAMMER_SET}}}{OK}}
Where SPAMMER_SET is a macro and it is defined as
"SET SPAMMER <some_value>"
(Getting a value from Redis)
set acl_c_spam_host = ${lookup redis{GET...}}
Proxy Protocol Support
--------------------------------------------------------------
Exim now has Experimental "Proxy Protocol" support. It was built on
specifications from:
http://haproxy.1wt.eu/download/1.5/doc/proxy-protocol.txt
Above URL revised May 2014 to change version 2 spec:
http://git.1wt.eu/web?p=haproxy.git;a=commitdiff;h=afb768340c9d7e50d8e
The purpose of this function is so that an application load balancer,
such as HAProxy, can sit in front of several Exim servers and Exim
will log the IP that is connecting to the proxy server instead of
the IP of the proxy server when it connects to Exim. It resets the
$sender_address_host and $sender_address_port to the IP:port of the
connection to the proxy. It also re-queries the DNS information for
this new IP address so that the original sender's hostname and IP
get logged in the Exim logfile. There is no logging if a host passes or
fails Proxy Protocol negotiation, but it can easily be determined and
recorded in an ACL (example is below).
1. To compile Exim with Proxy Protocol support, put this in
Local/Makefile:
EXPERIMENTAL_PROXY=yes
2. Global configuration settings:
proxy_required_hosts = HOSTLIST
The proxy_required_hosts option will require any IP in that hostlist
to use Proxy Protocol. The specification of Proxy Protocol is very
strict, and if proxy negotiation fails, Exim will not allow any SMTP
command other than QUIT. (See end of this section for an example.)
The option is expanded when used, so it can be a hostlist as well as
string of IP addresses. Since it is expanded, specifying an alternate
separator is supported for ease of use with IPv6 addresses.
To log the IP of the proxy in the incoming logline, add:
log_selector = +proxy
A default incoming logline (wrapped for appearance) will look like this:
2013-11-04 09:25:06 1VdNti-0001OY-1V <= me@example.net
H=mail.example.net [1.2.3.4] P=esmtp S=433
With the log selector enabled, an email that was proxied through a
Proxy Protocol server at 192.168.1.2 will look like this:
2013-11-04 09:25:06 1VdNti-0001OY-1V <= me@example.net
H=mail.example.net [1.2.3.4] P=esmtp PRX=192.168.1.2 S=433
3. In the ACL's the following expansion variables are available.
proxy_host_address The (internal) src IP of the proxy server
making the connection to the Exim server.