[Pkg-exim4-users] authenticated ACL

Sun Oct 30 21:42:01 UTC 2005

On Sun, Oct 30, 2005 at 06:16:54PM +0100, Andreas Metzler wrote:
> Neither local_from_check = false nor local_sender_retain = true *add*
> missing Message-ID and Date headers to messages submitted by
> authenticated SMTP, which is what
> control = submission/sender_retain
> is supposed to do.

I now understand what you mean. Yes, I agree that this should be added.

My suggestion for the new acl file is attached, and I have even
rudimentarily tested it. Please comment.

Greetings
Marc

### acl/30_exim4-config_check_rcpt
#################################

# This access control list is used for every RCPT command in an incoming
# SMTP message. The tests are run in order until the address is either
# accepted or denied.
#
acl_check_rcpt:
  # Accept if the source is local SMTP (i.e. not over TCP/IP). We do this by
  # testing for an empty sending host field.
  accept
    hosts = :

  # The following section of the ACL is concerned with local parts that contain
  # certain non-alphanumeric characters. Dots in unusual places are
  # handled by this ACL as well.
  #
  # Non-alphanumeric characters other than dots are rarely found in genuine
  # local parts, but are often tried by people looking to circumvent
  # relaying restrictions. Therefore, although they are valid in local
  # parts, these rules disallow certain non-alphanumeric characters, as
  # a precaution.
  #
  # Empty components (two dots in a row) are not valid in RFC 2822, but Exim
  # allows them because they have been encountered. (Consider local parts
  # constructed as "firstinitial.secondinitial.familyname" when applied to
  # a name without a second initial.) However, a local part starting
  # with a dot or containing /../ can cause trouble if it is used as part of a
  # file name (e.g. for a mailing list). This is also true for local parts that
  # contain slashes. A pipe symbol can also be troublesome if the local part is
  # incorporated unthinkingly into a shell command line.
  #
  # Two different rules are used. The first one has a quite strict
  # default, and is applied to messages that are addressed to one of the
  # local domains handled by this host.
  # If you have local accounts that include strange characters, you can
  # use the macro provided to change the ACL range or to disable the
  # check completely.
  .ifdef CHECK_RCPT_LOCAL_LOCALPARTS
  deny
    domains = +local_domains
    local_parts = CHECK_RCPT_LOCAL_LOCALPARTS
    message = restricted characters in address
  .endif

  # The second rule applies to all other domains, and its default is
  # considerably less strict.
  .ifdef CHECK_RCPT_REMOTE_LOCALPARTS
  deny
    domains = !+local_domains
    local_parts = CHECK_RCPT_REMOTE_LOCALPARTS
    message = restricted characters in address
  .endif

  # Accept mail to postmaster in any local domain, regardless of the source,
  # and without verifying the sender.
  #
  accept
    .ifndef CHECK_RCPT_POSTMASTER
    local_parts = postmaster
    .else
    local_parts = CHECK_RCPT_POSTMASTER
    .endif
    domains = +local_domains : +relay_to_domains

  # deny bad senders (envelope sender)
  # CONFDIR/local_sender_blacklist holds a list of envelope senders that
  # should have their access denied to the local host. Incoming messages
  # with one of these senders are rejected at RCPT time.
  #
  # The explicit white lists are honored as well as negative items in
  # the black list. See /usr/share/doc/exim4-config/default_acl for details.
  deny
    message = sender envelope address $sender_address is locally blacklisted here. If you think this is wrong, get in touch with postmaster
    !acl = acl_whitelist_local_deny
    senders = ${if exists{CONFDIR/local_sender_blacklist}\
                   {CONFDIR/local_sender_blacklist}\
                   {}}

  # deny bad sites (IP address)
  # CONFDIR/local_host_blacklist holds a list of host names, IP addresses
  # and networks (CIDR notation)  that should have their access denied to
  # The local host. Messages coming in from a listed host will have all
  # RCPT statements rejected.
  #
  # The explicit white lists are honored as well as negative items in
  # the black list. See /usr/share/doc/exim4-config/default_acl for details.
  deny
    message = sender IP address $sender_host_address is locally blacklisted here. If you think this is wrong, get in touch with postmaster
    !acl = acl_whitelist_local_deny
    hosts = ${if exists{CONFDIR/local_host_blacklist}\
                 {CONFDIR/local_host_blacklist}\
                 {}}

  # Deny unless the sender address can be verified.
  #
  # This is disabled by default so that DNSless systems don't break. If
  # your system can do DNS lookups without delay or cost, you might want
  # to enable this feature.
  .ifdef CHECK_RCPT_VERIFY_SENDER
  deny
    message = Sender verification failed
    !acl = acl_whitelist_local_deny
    !verify = sender
  .endif

  # For some sender domains, we do callout to verify if a sender
  # exists.
  deny
    !acl = acl_whitelist_local_deny
    senders = ${if exists{CONFDIR/local_sender_callout}\
                         {CONFDIR/local_sender_callout}\
                   {}}
    !verify = sender/callout

  # For some recipient domains, we do callout to verify if a recipient
  # exists. This is especially handy for customers that receive a lot of
  # spam to non-existent addresses.
  deny
    !acl = acl_whitelist_local_deny
    recipients = ${if exists{CONFDIR/local_rcpt_callout}\
                            {CONFDIR/local_rcpt_callout}\
                      {}}
    !verify = recipient/callout

  # Warn if the sender host does not have valid reverse DNS.
  # 
  # If your system can do DNS lookups without delay or cost, you might want
  # to enable this.
  # If sender_host_address is defined, it's a remote call.  If
  # sender_host_name is not defined, then reverse lookup failed.  Use
  # this instead of !verify = reverse_host_lookup to catch deferrals
  # as well as outright failures.
  .ifdef CHECK_RCPT_REVERSE_DNS
  warn
    message = X-Host-Lookup-Failed: Reverse DNS lookup failed for $sender_host_address (${if eq{$host_lookup_failed}{1}{failed}{deferred}})
     condition = ${if and{{def:sender_host_address}{!def:sender_host_name}}\
                      {yes}{no}}
  .endif

  # Accept if the message arrived over an authenticated connection, from
  # any host. Again, these messages are usually from MUAs, so recipient
  # verification is omitted.
  #
  accept
    authenticated = *
    control = submission/sender_retain

  # Check against classic DNS "black" lists (DNSBLs) which list
  # sender IP addresses
  .ifdef CHECK_RCPT_IP_DNSBLS
  warn
    message = X-Warning: $sender_host_address is listed at $dnslist_domain ($dnslist_value: $dnslist_text)
    log_message = $sender_host_address is listed at $dnslist_domain ($dnslist_value: $dnslist_text)
    dnslists = CHECK_RCPT_IP_DNSBLS
  .endif

  # Check against DNSBLs which list sender domains, with an option to locally
  # whitelist certain domains that might be blacklisted. If you want one
  # blacklist per domain, you need to replicate the stanza for each DNSBL.
  .ifdef CHECK_RCPT_DOMAIN_DNSBLS
  warn
    message = X-Warning: $sender_address_domain is listed at $dnslist_domain ($dnslist_value: $dnslist_text)
    log_message = $sender_address_domain is listed at $dnslist_domain ($dnslist_value: $dnslist_text)    !senders = ${if exists{CONFDIR/local_domain_dnsbl_whitelist}\
                    {CONFDIR/local_domain_dnsbl_whitelist}\
                    {}}
    dnslists = CHECK_RCPT_DOMAIN_DNSBLS/$sender_address_domain
  .endif

  # This hook allows you to hook in your own ACLs without having to
  # modify this file. If you do it like we suggest, you'll end up with
  # a small performance penalty since there is an additional file being
  # accessed. This doesn't happen if you leave the macro unset.
  .ifdef CHECK_RCPT_LOCAL_ACL_FILE
  .include CHECK_RCPT_LOCAL_ACL_FILE
  .endif

  # Accept if the address is in a local domain, but only if the recipient can
  # be verified. Otherwise deny. The "endpass" line is the border between
  # passing on to the next ACL statement (if tests above it fail) or denying
  # access (if tests below it fail).
  #
  accept
    domains = +local_domains
    endpass
    message = unknown user
    verify = recipient

  # Accept if the address is in a domain for which we are relaying, but again,
  # only if the recipient can be verified.
  #
  # If you want to use the more conservative "unknown user" error
  # message in case of a non-existing local part, you might want to
  # set CHECK_RCPT_GIVE_UNKNOWN_USER. However, this might reveal
  # local information, which is the cause for it not being enabled by
  # default.
  accept
    domains = +relay_to_domains
    endpass
    .ifdef CHECK_RCPT_GIVE_UNKNOWN_USER
    message = ${if eq{$acl_verify_message}{Unrouteable address}{unknown user}{$acl_verify_message}}
    .else
    message = unrouteable address
    .endif
    verify = recipient

  ############
  # If control reaches this point, the domain is neither in +local_domains
  # nor in +relay_to_domains.
  ############

  # Accept if the message comes from one of the hosts for which we are an
  # outgoing relay. Recipient verification is omitted here, because in many
  # cases the clients are dumb MUAs that don't cope well with SMTP error
  # responses. If you are actually relaying out from MTAs, you should probably
  # add recipient verification here.
  #
  accept
    hosts = +relay_from_hosts
    control = submission/sender_retain

  # Reaching the end of the ACL causes a "deny", but we might as well give
  # an explicit message.
  #
  deny
    message = relay not permitted

-- 
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